The Video Battery Handbook

TABLE OF CONTENTS


Please note: The Video Battery Handbook is organized as one large HTML file. This should allow you to print the entire Handbook directly from your browser by choosing <File, Print> from your menu bar. Your primary navigation tools for the Handbook are Hyperlinks and the <Back> button on your browser. Most of the links from here point to the detailed table of contents, which contains links to the main discussion topic, and to a more deeply technical discussion of the topic. At any time, you can click on your <Back> button to return to the table of contents. If there is enough interest, we will also provide a normally-sectioned HTML version with smaller pages and more traditional navigation in the future. If you'd like to see this, send us an e-mail. Thanks!


The Video Battery Handbook, World Wide Web edition, copyright 1996, 1997 Anton/Bauer Inc.

The following are registered trademarks of Anton/Bauer, Inc.: Snap-On, Magnum, Impac, Ultralight, Micro-Code, Propac, Triconn, ACS, SSP, Lifesave, ADM, Datatap, Powerstrap, Digi-Code, Data-Link, Probe, Compac Magnum, Logic Series, Logic Series Logo, Anton/Bauer, Anton./Bauer logo, Automatique, InterActive, The Quality Standard of the Video Industry, Power/Charger, HyTRON, HyTRON Battery System.


return to the Anton/Bauer home page


INTRODUCTION

Since the first television camera left the studio, video professionals have consistently identified batteries as the most problematical aspect of ENG/EFP. In the intervening two decades both video and battery technologies have dramatically improved. The latest Interactive microprocessor battery and charger systems are very reliable, delivering consistent high performance and eliminating all the problems associated with earlier systems. Yet the most recent surveys indicate that battery problems still head the list of many video professionals.

The explanation for this apparent paradox inevitably involves a misapplication. It seems that some video technicians will spend quite some time carefully analyzing the specifications and applicability of cameras and recorders, yet treat the battery as if it were a lens cap that has no bearing on operation or performance. In some cases it is assumed that the battery offered by the equipment manufacturer must be correct for the application. This assumption is incorrect. As each new generation of camera/VTR is developed, many equipment manufacturers merely continue to offer the older technology battery from previous models without regard to optimum compatibility or major technological advances. As an example, a battery developed in the 1970s for a 3/4" VTR is still being offered by several manufacturers with their latest CCD component camcorders which actually specify a higher voltage battery.

A battery should be selected with the same care and analysis as the other components in the system. There is no excuse for jeopardizing an entire video operation with an improper battery when it is really quite simple to determine the optimum battery for any application. This guide covers each element of battery/charger selection in a direct step-by-step style. We will focus our discussions on Nickel Cadmium (Ni-Cd) technology because of its widespread use in professional video, but have included some discussion of upcoming technologies such as Nickel Metal Hydride (NiMH) and rechargeable lithium. Following these guidelines will assure the selection of a battery system that will deliver optimum performance, greatest reliability, and long trouble free operation for your specific video application.

This guide will present all the elements essential in determining the proper battery and charger system for a modern professional video operation. You will note we have included additional technical sections for those technicians and engineers who wish a more in-depth explanation. One section deals with the aspects of on-camera lighting, an important factor in battery selection and quality video production. A Problem Appendix at the back of this manual discusses the most prevalent battery problems with respective causes and cures.


DETAILED TABLE OF CONTENTS

VOLTAGE

Voltage Technical Section

CAPACITY

Capacity Technical Section

BATTERY CONSTRUCTION

Construction Technical Section

BATTERY DESIGN FEATURES

CHARGING

Charging Technical Section

BATTERY LIFE

SAFETY HAZARDS

COLD CLIMATE PRECAUTIONS

PORTABLE LIGHTING

PROBLEM APPENDIX (with Solutions!)

UPDATE: NEW BATTERY TECHNOLOGIES 1997


VOLTAGE

There is ironically great confusion concerning the proper voltage battery for an application. In reality this is a very simple and direct specification. The confusion is due to the popular but incorrect practice of referring to a battery or camcorder by a single voltage. There is no such thing as a "12 volt battery" or a "12 volt camera". These numbers do not refer to average voltage, nor do they signify minimum or maximum voltage. These numbers are called ‘nominal’ ratings, which are merely convenient ‘names’ for these devices and have absolutely no relevance whatsoever to a specific application.

In actuality, every battery and every camera/VTR has a voltage range over which it operates. The process of matching the correct voltage battery to a piece of equipment simply requires that :

The first step is to establish the accurate voltage range of your equipment. If you have the instruction or technical manual, turn to the specification section and find the ‘Power’ entry. Hopefully you will find one of the following type entries:

In both of these cases the range of the device is 11 to 17 volts. Specifically, below 11 volts the device will cease to function properly (in some cases a camcorder or VTR will unthread or drop out of record below this voltage). Likewise voltages above 17 volts may damage the equipment or, more likely, blow a fuse or breaker.

If you no longer have the technical manual or the Power entry has a single number such as :

you will have to determine the voltage range by other means. One method is a simple phone call to the equipment manufacturer. Talk to an engineer and give him your precise model number. Our experience has shown that in order to avoid confusion, the voltage range will be best determined by asking the following two questions :

  1. "What is the lowest voltage I can supply to this device before quality or performance is adversely affected?"
  2. "What is the absolute highest voltage I can put to this device without causing damage or blowing a fuse?"

Once the voltage range of your equipment is accurately determined, the next step is to establish which voltage battery has a range that falls totally within the range of your equipment. The voltage range of NiCd batteries typically used in the video industry is as follows :

Matching the correct battery to your equipment is now straightforward. As an example, consider the typical technical manual entries above that listed the power range as 11 to 17 volts. In this case both the "13.2 volt" [11-15 1/2] and the "14.4 volt" [12-17] batteries have ranges totally within the equipment specification and are therefore fully compatible. In cases such as in this example where more than one battery is applicable, the best run time and reliability will always be achieved with the higher voltage battery. Note carefully that the range of the "12 volt" [10-14] battery extends below that of the equipment and is not compatible. The use of a "12 volt" battery in this application will cause a multitude of serious problems that are covered in the following technical section. (See also figure #1 and #2)

In addition to the above, the following general facts may also prove helpful for proper voltage selection :

  1. A "12 volt nominal" battery should never be used with modern video equipment. This is due to the fact that virtually every piece of professional video equipment designed in the last 10 years has a minimum voltage requirement of between 10.5 and 11.0 volts. Thus the 10 volt full discharge rating of a "12 volt nominal" battery is significantly below the minimum voltage requirement of all professional video equipment. (VTR batteries with cables such as BP-90 types and small NP-1 types should be particularly avoided. See Technical Section)
  2. A "13.2 volt nominal" battery can be considered a universal video battery that is compatible with virtually all professional video equipment. This is based on the fact that all modern video equipment (1980 +) specify a maximum voltage of 15.5 volts or higher, and a minimum voltage of 11 volts or lower (down to 10.5 volts). Thus the 11 to 15.5 volt range of a "13.2 volt nominal" battery falls totally within the operating range of all professional video equipment.
  3. A "14.4 volt nominal" battery should be used only with equipment which specifies such a battery or has a maximum voltage rating of 17 volts or higher. It is true that a "14.4 volt nominal" battery will provide better performance and life relative to a comparable "13.2 volt" battery, however not all video equipment can accommodate the high 17 volts that a "14.4 volt" battery can initially exhibit. Make sure your equipment can accommodate voltages as high as 17 volts before using a "14.4 volt" battery. As a rule, most professional equipment now being manufactured is designed to deliver optimum performance with "14.4 volt" batteries. However, when in doubt , always use a "13.2 volt" battery.

Please feel free to call the Anton/Bauer Service Center Hotline [1-800-541-1667]. Based on your model number, an Anton/Bauer engineer can tell you which voltage and type battery will deliver optimum performance with your equipment.

VOLTAGE TECHNICAL SECTION

BATTERY VOLTAGE RANGE

While the ‘nominal’ voltage rating is technically meaningless, battery "range" limits are very significant. When a fully charged battery is first placed on a piece of equipment and power is turned on, the initial voltage may be as high as the upper range limit. Typically the voltage will begin to drop quickly during the first few minutes, then continue to drop more slowly throughout the rest of the discharge cycle until the voltage reaches the lower range limit at which point the battery has released all its stored energy. The shape of this discharge curve and the rate at which the voltage drops is dependent on many factors including the power drain rate, battery size, age, temperature, and cell formulation. (See fig. #2) However, regardless of the shape in between, the lower limit remains the same and is called the ‘End Of Discharge Voltage’ or EODV by the cell manufacturers.

This EODV is the most critical voltage rating of a battery, and the only voltage specification stated by the cell manufacturer relative to capacity. This is the voltage down to which a NiCd battery must be taken in order to retrieve 100% of the available capacity. To put it another way, the cell manufacturer will guarantee full capacity only if the battery is discharged down to the EODV. Conversely, you can not get all the energy out of the battery until it reaches this voltage. Therefore, if the lower range limit of the battery (EODV) is below the lower operating voltage limit of the equipment, you will never get the full capacity or run time out of the battery.

Figure #1 clearly illustrates the problems of powering a modern piece of video equipment with a battery of improper voltage. In this example, the 10.0 volt End Of Discharge Voltage (EODV) rating of the "12 volt nominal" battery is significantly below the 11 volt minimum or "cut-off" voltage of the professional camcorder. Only a 13.2 or 14.4 camera battery fully conforms to the operating range of professional video equipment.

The discharge curve ‘A’, in figure 2, is typical of a "12 volt" NiCd battery in mid-life. Note that this battery is perfectly within specification and still delivers close to 100% of its rated capacity at its specified EODV of 10 volts. However, the camcorder can not make use of all this power because as soon as the battery voltage falls below 11 volts, the camcorder ceases to operate. The battery appears to have ‘lost’ 25% of its capacity. In reality the rest of the energy is still there, but the camcorder just can’t get to it. This is called "unavailable capacity" and is totally due to a battery voltage mismatch with the equipment.

The phenomena known as NiCd "memory" (see also "memory" in the Problem Appendix) is illustrated by curve ‘B’ where it is apparent that "memory" is actually a ‘voltage depression phenomena’. At the so-called "memory" point the voltage suddenly drops about 1.2 volts, where it is once again below the camcorder cut-off voltage. The camcorder stops and it appears that "memory" has caused a 50% loss of capacity. But if you look again, it is not really a loss of capacity. The battery will still deliver close to 100% capacity within the EODV voltage specification.

Curve ‘C’ represents a mid-life NiCd in cold weather. In this case the battery will run the camcorder for only 25% of its normal time. Again, there is nothing wrong with the battery. Curve ‘C’ is fully within the normal NiCd operating specifications yielding rated capacity at the EODV of 10 volts.

In all of these instances cameramen usually blame the apparent loss of capacity and run time on the battery ‘getting old’, or that strange "memory thing", or the cold weather. Considering these curves, it is easy to understand why "12 volt" batteries seem so unreliable. Depending on prevailing conditions you never know exactly how much run time you will get from a battery. In reality all three of these losses of capacity are due solely to the operator using the wrong voltage battery.

Curves ‘D’, ‘E’, and ‘F’ represent the discharge curves of a "14.4 volt" battery under the identical three conditions and with the identical camcorder. As if by magic the "getting old", "memory", and cold weather problems suddenly disappear. Why? Because the 12.0 volt EODV or full discharge voltage rating of the "14.4 volt" battery is properly above the 11 cut-off voltage of the camcorder. The curves of a "13.2 volt nominal" battery with an EODV of 11.0 volts would also deliver 100% capacity in all these cases.

The problems of using a "12 volt" battery as illustrated above are further aggravated if it is a BP-90 type or other style that uses an attached short cable and small coaxial connector. The power drain of modern camcorders will create a significant ‘voltage drop’ across the high contact resistance of these small plugs. This voltage drop lowers the curves in the examples above resulting in a more severe loss of capacity in each case. Likewise, small "12 volt" VTR batteries such as the NP-1 types, should also be particularly avoided. These small capacity batteries have greater internal resistance which also results in a significant lowering of the voltage curve. This also results in a significant loss of run time regardless of voltage level and a very severe loss of capacity in the above illustrated examples.

From the foregoing it should be painfully clear why "12 volt" batteries, especially small VTR types or cable styles, should be strictly avoided for professional video applications.


CAPACITY

There are many video professionals who have unwittingly crippled their field production capabilities by selecting the wrong capacity battery for the wrong reasons. The criteria for selecting the capacity of a video battery is very different from those for selecting a battery for a film camera or any other portable application for that matter. A film cameraman can look through his camera all day without a battery even being attached. He can be setting up a shot or waiting for an event to occur for hours without drawing any power. A film camera only draws power when film is rolling, much like a power drill that only draws current when drilling a hole. The film cameraman can thus select a battery based on how many film magazines he expects to shoot between battery changes.

Video is very different from almost all other battery applications. A cameraman functions through his eyes and is comfortable only when he can ‘see’ through his camera. Unlike a film camera, you can not ‘see’ through a video camera unless it is turned on and drawing full power. The video camera is always drawing power while the cameraman sets up his shot or waits for a politician to step out of the capitol building. The power consumed by a video camera therefore has absolutely nothing to do with the number of video cassettes being shot. A cameraman can often run through an entire battery before rolling a single minute of tape. While the criteria of motion pictures is the amount of film a battery can run, the critical consideration for video is the amount of time a battery can run a camera or camcorder.

The vital question when selecting a video battery is thus: "How long must the equipment run between battery changes?" And the answer is a simple but emphatic : 2 FULL HOURS.

This is the most basic rule of selecting a battery for a professional video application: the battery must run the associated equipment for a full 2 hours. This is not an arbitrary or capricious guideline but rather a very serious specification which is based on extensive statistical analysis of hundreds of professional video operations. It is also based on pure logic. There are several significant considerations for this 2- hour rule, the most important of which is battery change disruptions.

Surveys of video professionals have indicated conclusively that more than one battery change disruption per morning/afternoon is unacceptable. One battery change interruption can be reasonably anticipated and is deemed manageable. However, two or more are perceived as random disruptions that seriously impair production efficiency and result in lost time and shots. The ultimate battery system is thus 4 batteries and 1 four-position charger. Start the day with battery #1. Mid morning change to battery #2 if necessary. At lunch-break change to battery #3 (even if #2 is not fully depleted). Mid afternoon change to battery #4 when necessary. The result is a maximum of one interruption per morning/afternoon. In order to assure this simple and efficient routine, the battery must be capable of running the equipment for a minimum of 2 hours.

A one-hour battery, by contrast, involves a very complex system of 10 batteries, 3 chargers, and the chaos of as many as 8 interruptions per day (see Technical Section). It has been proven conclusively that batteries that deliver fewer than 1 1/2 hours of run time are severely disruptive, inefficient, and uneconomical. And batteries providing less than one hour of operation are outright disasters. The classic reasons for making this mistake include the desire for a ‘small’ or ‘light weight’ battery. As the Technical Section explains, the proper 2-hour batteries actually balance the camcorder better for less operator fatigue, and weigh less and cost less than the equivalent amount of smaller type batteries. Insufficient capacity can cripple a video operation. Start with the correct, efficient, and economical 2-hour battery for your application.

To emphasize the criticality of this two hour minimum run time specification, it is interesting to note that two out of the three major U.S. television networks have been using Anton/Bauer Silver Zinc high performance batteries for the last decade. A single Silver Zinc battery can run a camera/camcorder for an entire day, eliminating all battery change disruptions. While the initial expense of these batteries is significantly greater than NiCd, these major networks have determined that battery change disruptions are far more costly. Silver Zinc batteries are not recommended for most applications, especially in light of recent advances in NiCd technology. The point here is that two out of three major networks considered even one interruption per morning/afternoon too disruptive and costly which truly emphasizes the criticality of the two hour minimum and one disruption maximum.

Determining the proper 2-hour battery for any application is incredibly simple. Capacity refers to the total power a fully charged battery can deliver and is measured in "watt hours" (not "ampere hours", see Technical Section). To determine the capacity of a 2-hour battery for any application merely take the power rating of the camera or camcorder and multiply by 2.

As an example, assume your technical manual or the label on your camcorder states "Power Consumption = 26 watts". The proper battery for that camcorder should have a minimum of 2 x 26 or 52 watt hours of capacity. After this calculation, select from those batteries with capacity ratings of 52 watt hours or greater. The following additional points should also be considered :

CAPACITY TECHNICAL SECTION

The topic of capacity is technically more complex than the simple rating number would suggest. Like voltage, the capacity rating is "nominal" and in practice the actual amount of energy a particular battery can deliver to a camcorder can vary over a wide range depending on a multitude of parameters and conditions. This section will provide a better understanding of the most significant elements that can affect the available capacity of a battery and the run time of your camcorder.

Watt hours or Ampere hours ? - The most classic cause of confusion involves the units used to rate battery capacity. While cell manufacturers rate individual cells in "ampere hours", the proper unit for the measurement of energy in a group of cells, or battery, is the "watt hour". This is quite evident since watts are the unit of power and hours the unit of time. The older practice of rating a battery in ‘ampere hours’ is both incorrect and misleading. As an example, assume a "12 volt" battery and a "14.4 volt" battery are both rated at 5 ampere hours and are to be used with a device that draws 24 watts. Given that both batteries have the same "capacity" of 5 ampere hours, one would conclude that both batteries will run the device for an identical length of time. But this is not true. The "nominal" watt hour capacity rating for each of these batteries is calculated as follows:

The nominal run time is calculated by dividing this capacity rating by the power of the equipment :

Thus the "14.4 volt" battery will provide a minimum of 20% greater run time compared to a "12 volt" battery with the identical ‘amp hour’ rating. It should now be evident why the ampere hour rating is misleading . Always compare and select batteries using ‘Watt Hour’ ratings. From the above example it is also clear that you can determine the nominal run time of any battery by simply dividing the Watt Hour Rating of the battery by the power draw in watts of the equipment.

The technical reason why the higher voltage battery will deliver greater run time involves the modern power supply circuit found in all professional video equipment since the late seventies. Older style power supplies were ‘constant current’ types that merely sliced away any extra voltage thus wasting energy. Modern ‘switch mode’ circuits are ‘constant power’ types that actually use the extra voltage to reduce current. This keeps the power draw constant with comparatively no wasted energy. Here lies the fallacy of the ‘Amp Hour’ rating. All modern cameras actually draw less current (amps) from higher voltage batteries. This reduction in current drain has other benefits in addition to proportionately greater run time. As discussed next, reduced current drain raises the "effective capacity" rating of the battery which further enhances run time as well as overall performance and life.

"Testing Capacity" - Many technicians make the common mistake of testing battery capacity by discharging through a load resister or light bulb and using the number of minutes to fully discharge the battery as an indication of capacity. Unfortunately this method produces highly erroneous results. An example will best demonstrate the fallacy of using discharge time as an indication of capacity:

Two NiCd batteries are to be tested for capacity, one is a ten cell ‘12 volt’ while the other is a twelve cell ‘14.4 volt’. Both fully charged batteries are discharged on a load resister or light bulb with a resistance of 3 ohms. The ‘12 volt’ battery runs a full hour (60 min) while the ‘14.4 volt’ runs only 55 minutes before reaching their respective EODVs. Most technicians would conclude that the ‘14.4 volt’ battery had almost 10% less capacity than the ‘12 volt’ battery. In reality this test proves the ‘14.4 volt’ battery actually has 32% more capacity than the ‘12 volt’ battery.

Using the basic formula I=V/R (current equals voltage divided by resistance), the ‘12 volt’ battery was being discharged at 4 amps by the 3 ohm resister while the ‘14.4 volt’ battery was being discharged at the higher rate of 4.8 amps by the same 3 ohm resister. Taking the broad liberty of using the ‘nominal voltage’ rating as an ‘average voltage’, the capacity of the ‘12 volt’ battery would be calculated by multiplying ‘12 volts’ by the 4 amps discharge current times the one hour duration:

Thus while the discharge test seemed to indicate that the ‘14.4 volt’ battery had less capacity, in reality it had greater than 30% more capacity and would run a camcorder more than 30% longer than the ‘12 volt’ battery. This timed discharge test is equally misleading for lighting applications since the higher voltage battery not only raises the wattage rating of a given bulb, but also increases the lumens/watts efficiency of the bulb. Thus, for a given level of illumination, the ‘14.4 volt’ battery would also provide longer illumination time than the ‘12 volt’ battery.

Always remember, discharge data must be rendered into Watt Hour Capacity otherwise it is totally irrelevant and misleading.

"Rated Capacity" - The capacity rating of a battery is extremely dependent on the rate of power drain. In addition to the aforementioned EODV, every cell manufacturer always includes a current specification with the capacity rating such as "5 ampere hours @ 5 ampere current drain". This specific example is called the "C" rate or "One-Hour" rate capacity. In other words, the battery will deliver "5 amps for one hour". Because of internal resistance and other factors, the effective capacity will be less at greater current drains. Conversely the effective capacity will be greater for lower current drains. In the above example, this same cell may be rated : "5.5 ampere hours @ 1 ampere current drain" which is the "C/5" or "five-hour rate" capacity. Likewise the "C/10" or "ten-hour" rating may read : "5.8 ampere hours @ 1/2 amp current drain". Cell manufacturers will typically use one of these three standard rates to specify capacity.

The "Numbers Game" - Note from the above that the cell appears to magically gain capacity as you go from the ‘one-hour’ to the ‘five-hour’ and then to the ‘ten-hour’ rating method. Some battery manufacturers use this ‘magic’ to make their batteries sound like they have more capacity. Theoretically and ethically, a battery should be rated using the method that most closely approximates the power drain and run time of the intended application. For all video applications this is most definitely the ‘one-hour’ or "C" rate method which is used by most professional video battery manufacturers. Unfortunately not every video manufacturer uses the appropriate rating system. As an example, one slide-in type video battery is rated on the label as having "2 amp hours" of capacity. This rating was taken from the cell manufacturers ‘ten-hour’ specification. However, the ‘one-hour’ rating for this battery, which is consistent with the application, is only "1.7 amp hours" or 15% less. In addition to this ‘number game’, the relationship between current drain and available capacity is very relevant when comparing batteries of different sizes even if they are properly rated. The term ‘effective capacity’ refers to this variation of capacity with changing current loads.

Effective Capacity - Contrary to popular belief and simple logic, two 25-watt hour batteries will deliver less run time than one 50-watt hour battery. This is due to "effective capacity" which derates the capacity of a battery based on increased power drain. In essence, a 25-watt camcorder represents a ‘light’ load to a 50-watt hour battery but appears twice as large to a small 25-watt hour battery. As a result, the 25-watt hour battery may actually deliver only 20 watt hours while the 50-watt hour battery will provide a full 50 watt hours with the same load. Thus it may take ten 25-watt hour batteries with up to 8 change disruptions to equal the run time of four 50-watt hour batteries with only 2 interruptions. In addition, the 10 smaller batteries will weigh more than the 4 larger batteries. And don’t forget "charger capacity". Ten smaller batteries will require 3 four-position chargers instead of one. In most cases the proper 2-hour per battery system is less expensive to purchase and far more economical in the long run.

Camera/Camcorder Balance - The critical mistake of selecting a battery with insufficient capacity can almost always be traced to the erroneous penchant for a ‘lighter weight’ battery. In reality, most video professionals agree that good balance is far more critical than a minor difference in overall weight. With zoom lenses becoming more sophisticated and heavier, and camcorders becoming more compact, the overall package is becoming front-heavy on the cameraman’s shoulder. This front biased weight places a fatiguing strain on the operators right arm and back. In almost all cases the proper 2-hour battery at the rear will perfectly balance and stabilize the camera while eliminating back and arm fatigue. In most cases the perfectly balanced camera can feel lighter than an imbalanced camera equipped with a smaller battery. The irony here is that many cameramen create all the insufficient capacity problems outlined above thinking that they are getting some kind of weight benefit. In reality any such benefit is imperceptible or even non-existent.

Capacity and Voltage - Do not forget the lesson of figure #2 in the Voltage Technical Section. Using a battery of insufficient voltage will reduce available capacity up to 80%. Access to 100% of the available capacity can be assured only if the EODV of the battery is above the cut-off voltage of the camera/camcorder.

Capacity and Charging - When you get to the Charging Technical Section you will learn that despite everything that has been said here, it is really the charger/battery relationship that determines whether the battery runs the camcorder for two hours or two minutes.


BATTERY CONSTRUCTION

It is quite ironic that in this Space Age / Computer era many battery problems, failures, and hazards are still the result of something so mundane as poor ‘packaging’ techniques. A modern NiCd cell is actually a very fragile device that can be damaged or destroyed by physical forces typically encountered every day. Lacking the proper protective casings and professional construction techniques, a NiCd battery has no hope of surviving in the real world of professional ENG/EFP. In addition, improper construction can create a serious risk of fire (See Safety Hazards Section).

To assure dependable operation and preclude failures and hazards caused by poor construction techniques, choose a battery based on the following design guidelines :

  1. The battery should have a very durable case of high impact injection molded material. The cells inside should be isolated from the case at points of critical stress such as corners. Avoid thin plastic cases that allow you to actually feel the cylindrical cells inside. These offer no protection and will transmit any impact directly to the cells causing separator failure.
  2. Look for solid, unitized construction which distributes and absorbs impact like a crash helmet. Avoid batteries that are constructed of two halves that are screwed together. Screws create stress concentrations that will crack under impact and also prevent impact energy from being distributed evenly over the entire battery.
  3. The electrical contacts must be low-resistance and preferably gold plated multi-point contact types. Insertion of the battery into the charger or camcorder should result in significant ‘wiping action’ to maintain a clean and reliable connection. The contacts must also be recessed significantly to preclude short circuits should the battery accidentally come into contact with a small metal object. Avoid batteries with small consumer grade connectors on the end of short cables. These connectors exhibit high resistance which lowers the output voltage and can significantly reduce running time. In addition, these cable type connectors are very prone to damage and failure.

The importance of a rugged and well designed case has recently gained additional significance. Some of the latest high capacity cells achieve their greater energy capability by utilizing thinner cell casings and a new plate material that is more fragile than the standard sintered plate technology. This adds up to a cell that is actually more fragile and vulnerable than those that the video industry has been using for the last decade. Without adequate protection, new fragile construction cell technology will cause more problems than it will solve.

(The IMPAC design of all Anton/Bauer professional batteries complies fully with the above guidelines.)

CONSTRUCTION TECHNICAL SECTION

This figure represents the interior construction of a modern NiCd cell. (Many other cell technologies also share this design.) The basic elements include one positive and one negative plate that are kept apart by two extremely thin separators. These plates and separators are wound together jelly-roll fashion and ‘stuffed’ into a thin walled metal canister. The negative plate is welded to the bottom of the canister. After the proper amount of liquid electrolyte has been added, the positive plate is welded to a top-cap that is then used to seal the top of the canister. The insulating ring between the cap and canister also helps create an ‘airtight’ seal. While the cell is designed to operate as a ‘sealed system’, a safety vent in the cap will discharge the excessive pressure that could result from improper charging or discharging practices. The key word in this paragraph is "thin"; thin separators, thin plates, and thin-walled canister.

Internal Short Circuits - The canister of a NiCd battery offers very little protection to the internal components. Firstly, it is so thin you can easily crush the canister between your thumb and forefinger like a miniature beer can. Secondly, the internal plates and separator assembly are practically press fit into the canister so that even the slightest deformation of the canister will cause a corresponding distortion and stress to the plates and separator. The separator is the only thing keeping the positive and negative plates from touching and it is so thin that you can see through it like tissue paper. These two facts account for one of the most plaguing battery problems: the high impedance internal short circuit.

Accelerated Self Discharge and Imbalanced Batteries - When a battery is tossed onto a shelf or accidentally knocked against another object, a cell case can be slightly dented, creating a permanent internal pressure point. At this pressure point the two plates are being squeezed together and eventually the separator begins to break down allowing a small leak of current to pass from the positive plate to the negative. This phenomenon is sometimes referred to as ‘accelerated self-discharge’. Depending on the severity of the ‘short’, a cell can totally discharge itself in a few days or even a few hours. This condition causes several serious and sometimes perplexing problems.

Typically only one or two cells in a battery are so inflicted. Thus while these cells may be totally depleted, the remaining cells may be fully charged. Of course when such a battery is placed on a camcorder it will appear ‘dead’ or discharged. Yet when it is placed on a conventional battery charger, the majority of fully charged cells will trigger a "READY" indication and the battery remains in its totally imbalanced and unuseable state. In many cases such a battery is believed dead and unfortunately thrown out.

While a properly designed Interactive battery/charger system can correct this imbalanced stalemate (see Charger Technical Section), prevention is always preferable to the cure. Prevention in this case requires a highly protective battery construction such as the Anton/Bauer IMPAC case which uses the same materials and design techniques as a crash helmet. The injection molded LEXAN® polycarbonate case is computer designed to absorb and dissipate impacts while the cells inside are isolated from the case at points of highest stress. The double overlapping welded construction forms a unitized shield eliminating stress concentrations and case failure. With this advanced technology construction, the battery can survive a 5 foot drop onto a hard surface and exhibit no internal cell injury. One of the most perplexing battery anomalies can thus be eliminated by professional quality case design and construction.


BATTERY DESIGN FEATURES

The voltage, capacity, and case construction of a battery are critical elements that can be easily qualified. However there are many other aspects and features of a battery design that can have a profound effect on the efficiency and reliability of an ENG/EFP operation. When selecting a battery system, the following additional points must be considered :

Cell Type and Quality - There are now many different NiCd cell types and formulations available from a multitude of manufacturers around the world. Relatively few of these manufacturers produce a cell with the quality and performance features which meet the requirements of professional video. Within this small group of premium cells there are several different formulations that have specific performance benefits and trade-offs. Factors such as run-time, overall life, economy, and charger compatibility must be considered. The Technical Section below covers some of the more basic aspects of cell selection.

Internal Construction - While the integrity of the overall battery case is the paramount construction feature, the quality of the internal assembly is also quite important. All cells should be strap welded. Cell insulating sleeves should be heavy duty fibre type instead of thin PVC plastic. There should be no wiring that can become pinched between the cells and the case. A design that incorporates printed circuit boards and molded-in wire channels eliminates wire flexing, connection fatigue, and pinched wires that can cause catastrophic short circuits or complete failures. An analysis of assembly techniques and components combined with plain common sense can often indicate which batteries will survive in the field and which are failures or hazards waiting to happen.

Quality Control - Research has shown that an analysis of the first few cycles of a NiCd battery can reveal several potential problems that would eventually prove disruptive in the field. We believe the computerized 100% full discharge testing performed on every Anton/Bauer professional battery is an exemplary form of quality control. This computer print-out, which is shipped with each battery, indicates capacity, voltage plateau, and includes a complete voltage discharge curve which is the most effective indication of overall cell matching and performance.

"Universal" Vs. InterActive Batteries - All batteries can be classified into two basic categories: (1) so-called "universal" replacement type batteries, and (2) InterActive types that are an integral part of an InterActive battery/charger system. The universal type usually includes just two electrical contacts [power-out plus and minus] and must be charged with a dedicated slow charger or a universal fixed rate fast charger. The InterActive battery is part of a battery/charger system that relies on precise battery data to facilitate accurate and dependable charging. The battery must therefore have a network of sensors and circuits in order to monitor the necessary parameters and provide the data required by the interactive charger. The battery must also include communication contacts in addition to the two power output contacts. As explained in the charging section, only an interactive battery/charger system should be considered for professional video and film applications.

Digital Battery - The most advanced InterActive battery is the Digital type that includes a complete microprocessor in addition to the other interactive sensors and circuits. These Digital circuits provide the highest level of charge accuracy and convenience while facilitating a new type of automatic battery management and maintenance system (see charging section). However the Digital battery has a unique feature that will be of greatest interest to the cameraman. The microprocessor in the battery includes a "fuel computer" program that monitors electrical current both into and out of the battery and can accurately compute the state of charge and remaining capacity at all times. This remaining charge or ‘available capacity’ can be displayed in a LCD so the cameraman can know at a glance the remaining run time available from the battery. In addition to this LCD in the battery, professional video camera/camcorder manufacturers have begun to include a ‘remaining battery time indicator’ or ‘fuel gauge’ in the viewfinder that couples to a special interactive contact on the Anton/Bauer Digital Battery and battery mount. This viewfinder display can be a ‘bar graph’ or digital ‘percent remaining’ number. Cameramen who have been mislead for years by the unreliability of the meaningless ‘low voltage warning’ light will be pleased with this new fuel gauge which is an accurate quantitative representation of remaining run time as computed by the battery.

Battery Mounting - The following points should be considered when selecting a battery and mounting system:

  1. A quick-release mount is preferable to a battery that slides into a box or compartment. The box concept restricts the equipment to a specific size battery while a quick-release mount allows the user to use any of a variety of battery types and sizes to match a particular assignment. Furthermore the quick-release mount allows the equipment to be made much smaller for transporting by merely removing the battery. In addition, the existing boxes and compartments will not accommodate many of the new cell technologies that are currently being developed which differ from NiCd in both size and form-factor.
  2. Do not use batteries that have a cable mounted connector. The high resistance of the small connector can cause voltage reduction problems while the wire and its mating with both the battery and connector have consistently been identified as the most frequent cause of battery failure. In addition, these connectors have no latch or detent mechanism and frequently become disconnected inadvertently during operation and charging.
  3. Make sure the power contacts are rated for a minimum of 10 amps and are self cleaning ‘wiping action’ type connectors where a male plug slides into a corresponding female socket. Avoid ‘touch’ type contacts which are not self cleaning. Also avoid contacts that are rivetted due to the unreliability of such connections in electrical applications.
  4. The battery mount on the camera should include a power socket designed specifically to power a camera mounted light. Camera mounted ‘fill’ lights powered from the camera battery have become necessities for high quality location video. The latest generation of these lights has achieved an extremely high level of efficiency and draw very little power which has allowed them to be powered from the camera battery. This power connection should be independently fused so that the camera will always stay powered even if a problem develops with the light. (See Lighting Section)
  5. Note: The Anton/Bauer Gold Mount system, which is included as standard equipment by every professional camera/camcorder manufacturer, has been designed to meet all the above criteria.

CELL FORMULATION TECHNICAL SECTION

NiCd Cell Types

  1. "Sintered/Sintered" - This is the classic premium NiCd cell which has been employed by most professional video battery manufacturers for more than a decade. This designation refers to the fact that both the positive and negative plates have been impregnated with active material using a sintering process. This type of construction has earned a well deserved reputation for ruggedness, long life, and consistent performance under a wide range of conditions. Recent developments in sintered/sintered technology have resulted in improved capacity while retaining the other desirable attributes of this type cell which include heavy duty construction and low internal resistance. This type cell is still the choice for applications stressing reliability, high power drain, and long life under extreme conditions.
  2. "Pressed" or "Pasted" - While this type cell also utilizes a sintered positive plate, the active material is pressed onto the negative plate. (Japanese cell manufacturers use the term "pasted negative" while Americans refer to this type cell as a "pressed negative") . In the past, this type cell was considered to be of inferior quality relative to a sintered/sintered. Though it typically exhibited slightly greater initial capacity for its size, the pressed negative cell never-the-less remained unpopular for professional video applications. This was due to several serious drawbacks which included an inability to be safely and effectively fast charged, shorter cycle life (especially when fast charged), higher internal impedance, and greater susceptibility to internal damage and shorts.
  3. Recent developments, however, have now given new life to the pressed negative formulations. The physical vulnerability of these cells have been significantly addressed with new impact absorbing battery case designs. Furthermore, cell manufacturers have significantly improved pressed negative formulations to yield substantial gains in power density (capacity/size). Many ‘High Performance’ or ‘High Capacity’ NiCd batteries now being offered are of this pressed negative construction.

    While these latest "high performance" pressed negatives are capable of run times up to 25 % greater than comparable sintered/sintered types, the following points must be considered. Cycle life of pressed negative formulations are typically 30%-50% less than those of sintered/sintered types. These type cells should only be used as part of an InterActive battery/charger system. Charging with conventional chargers will not only fail to produce the expected gains in capacity, but will result in dramatically reduced cycle life. In addition, due to the relative vulnerability of the pressed negative cells, greater emphasis should be placed on the integrity of the battery case construction. Lastly, due to a higher internal resistance, pressed negative cells will not perform as well in higher power applications. In essence the ‘effective capacity’ of a pressed negative battery is more drastically reduced by higher current drains than the more heavy duty sintered/sintered type. For higher current drain applications a sintered/sintered cell may produce longer run times and a greater overall life than a pressed negative battery with a higher "rated" capacity. (See Effective Capacity in Capacity Technical Section above).

    While the potential capacity gains of the latest "high performance" pressed negatives are certainly desirable, make sure all the pros and cons relative to the specific equipment application and usage requirements are considered before making a final decision.

  4. "High Porosity" - This relatively new development is based on a very high porosity plate material that is sometimes called "sponge metal". This great porosity exposes significantly more plate material to the electrolyte and thus the battery appears to have the plate area of a larger battery with associated greater capacity. Such technology theoretically holds the promise of significant improvements in power density for certain applications. In its present form, this cell construction exhibits all the aforementioned characteristics of a pressed negative type cell and the associated caveats expressed above apply equally to this type cell.

In general, the performance claims of any cell technology must be tempered, by the specifics of the application. These specifics include power drain, charger design, battery case design, as well as the relative importance of the many battery characteristics such as capacity, ruggedness, and overall life.

Alternate Cell Technologies

  1. Lead Acid or Gel Cells - This cell technology has no viable application to professional video. Even consumer video has dropped Gel Cells in favor of the more reliable and economical NiCd. The only allure of lead acid/gel cell batteries was their initial low cost. In reality these cells are more expensive than NiCd due to a significantly shorter cycle life. With a high internal impedance, these type cells also exhibited significantly reduced ‘effective capacity’ in professional video applications. Relative to a comparable NiCd battery, lead acid/gel cell types are bigger, heavier, more costly, have less than 1/4 the cycle life and are irreparably damaged if left in the discharged state for extended periods.
  2. Silver Zinc - These type cells have been popular in limited circles since the advent of ENG/EFP. At that time, silver zinc had a power density 3 times that of NiCd and several television networks opted to build an ENG operation around this technology. Cameramen love the ‘shoot-all-day-on-one-battery’ aspect which eliminates battery interruptions and the carrying of spare batteries. The popularity of silver zinc remained limited and is currently waning for several reasons. Initial expense is almost three times that of NiCd while cycle life is rated 75% less. Moreover, while NiCd has proven to be a rugged almost foolproof technology, silver zinc is extremely unforgiving of deviations from its associated list of specific operating procedures and limitations. Silver zinc batteries, unlike NiCds, also require periodic disassembly and service.
  3. The introduction of InterActive technology and improved NiCd cell formulations has reduced the power density advantage of silver zinc. Considering this and the aforementioned economic and operational drawbacks, silver zinc is no longer considered a viable alternative for new applications.

Future Cell Technologies

There are several new rechargeable technologies currently being developed which include metal hydride and lithium types. While power density advantages of up to 3 times that of NiCd have been proffered, it must be remembered that the actual magnitude of these advantages are application dependent and may be significantly less given the power levels of professional video and film. In actuality the push to a new cell technology may be motivated more by environmental concerns than by performance benefits. In any event, between these new technologies and the rapid advances in Nickel Cadmium formulations, the video industry can definitely look forward to a combination of smaller and higher power batteries in the not too distant future.

Unfortunately these new cell technologies are not compatible with conventional NiCd chargers. Metal hydride and lithium type batteries can be destroyed and a serious hazard created if charging is attempted with a conventional NiCd charger. When these new cell technologies are introduced, a complete and total conversion to the new system will have to be facilitated. An InterActive NiCd battery/charger system is unique in this regard as it is designed to be compatible with most future cell technologies . (See Charging Section next)


CHARGING

Once a professional battery of the correct voltage and capacity for a particular application has been selected, the success or failure of your video operation will depend almost entirely on the charging system. Poor and erratic performance is primarily due to a basic characteristic of rechargeable batteries known as "charge acceptance". Simply stated, a battery actually rejects or accepts any or all the current from a charger depending on a multitude of prevailing conditions. Contrary to the outdated popular concept, a battery is not like the fuel tank in your car that merely has to be ‘filled’ with a specific quantity of fuel. A battery is more organic and can not be ‘filled’ with charge current any more than a flower can be ‘filled’ with water. In order to achieve optimum capacity a battery must be ‘fed’ charge current in a precise manner according to a multitude of parameters and conditions. All conventional chargers ignore these factors and merely deliver a fixed and steady flow of current, reducing battery performance to a mere game of chance. It is not uncommon for a charger to indicate that a battery has been given a full charge and is ‘ready’ to use when in fact the battery has ‘accepted’ less than half the charge current and thus contains less than half its potential capacity.

It is now acknowledged that the charging process must consider all the parameters and conditions that affect charge acceptance in order to properly charge a battery and assure optimum performance. This is exactly the basis of the latest innovation in battery technology: InterActive battery/charger systems. The key to this technology is designing the battery and charger together as a complete system. During charging, the battery and charger "talk" to each other. The battery is designed with a network of electronic sensors that monitor vital charging parameters while a program module contains critical data such as cell formulation, capacity, and voltage. All this data is fed to the charger microprocessor which then creates the optimum charge regime for that battery under the actual prevailing conditions. In essence the battery is controlling the charge process by telling the charger who it is and how it wants to be fed today. This technology brings rechargeable batteries from the dark ages into the space ages with consistent and dependable high performance while eliminating the fire and hydrogen gas explosion hazards that have always existed with conventional chargers.

This is the only rule of charging you need to know : select an InterActive battery/charger system for dependable high performance and safe trouble free operation. With the development and introduction of this highly reliable system technology, it would be a travesty to base a professional video operation on anything else. (The Technical Section covers the specific benefits and technical features of this system as well as the problems of conventional charging.)

Charging Future Battery Technologies - There are several new cell technologies on the horizon that hold the promise of significant performance and environmental benefits. These new cells can not be charged on conventional NiCd chargers, or more to the point, they can be destroyed and create a hazard to the operator if such is attempted. The expensive ordeal of having to switch an entire battery system en masse to the new technology will eventually have to be faced. While a change to the new cell technology is inevitable, the accompanying ordeal is not. The new InterActive chargers typically include all software data on a single replaceable program chip within the charger. As each cell improvement or new cell technology is introduced, the corresponding charge regimes may be programmed into an updated chip that is simply inserted into the charger in place of the old one. The updated charger could then identify and properly charge the new type batteries as well as all the older types simultaneously. With this new system a gradual and economical transition to a new cell technology is possible.

CHARGING TECHNICAL SECTION

It is the charging system, or more precisely the battery/charger interaction, that will ultimately make or break a portable video operation. Assuming a professionally constructed battery of correct voltage and capacity has been selected for an application, all remaining problems of poor or erratic performance can always be traced to improper charging practices or a charger with insufficient control and safety circuits. The following topics address the most prevalent causes of unreliable and poor battery performance, as well as premature battery failures.

SLOW CHARGING

Every NiCd cell used in the video industry is the sealed cylindrical type, which has an inherent ability to accept a certain amount of overcharge current indefinitely. The two important aspects of this type cell that facilitates this overcharge capability is its sealed construction and a negative plate that has slightly more area than the positive plate. During charging, virtually all the charge energy is being stored in the cell by converting the chemical elements of the internal plate compounds. The cell is essentially fully charged when all the positive plate material has been converted. If the charge current continues past this point, it can not be absorbed by chemical conversion and instead it produces oxygen gas at the anode. Because the cell is sealed, this oxygen is contained in the cell where it eventually finds its way to the unused portion of the larger negative plate where it is absorbed. In the process of absorbing oxygen, heat is created and thus the overcharge current is essentially dissipated as heat. The cell is designed to dissipate a certain amount of overcharge current in this manner indefinitely with no immediate adverse affects. This ability to absorb oxygen has its definite limit which is usually a current that is one tenth the ampere hour rating of the cell (C/10 rate). Thus a 5 amp hour cell can absorb up to 0.5 amps or 500 ma of overcharge current continuously with no immediate adverse effects.

This continuous ability to dissipate an overcharge current of up to ‘C/10’ is the precise basis and definition of a "slow" or "overnight" charger. The term "trickle charge" is also used to describe charge rates of ‘C/10’ or slightly less. Such chargers are incredibly simple and in many cases consist of no more than a transformer and a diode in a small black box. The ‘C/10’ constant current will typically charge the appropriate battery in 15 to 20 hours and when the battery is fully charged there is allegedly no problem as the battery will happily dissipate the continuing charge current indefinitely. At first glance the ‘slow’ or ‘overnight’ charger seems foolproof, economical, safe, and dependable.

Contrary to its deceptively simple concept, the slow charger is impractical and should be avoided for professional video applications for several important reasons :

  1. TIME - Slow charging is too slow for professional applications. The 20 hours necessary for a complete slow charge means that a battery brought in at 6 PM will not be fully charged until 2 PM the next afternoon which is totally unacceptable. While an 8 hour charge routine would be perfectly acceptable, almost all professional portable products, from electric drills to portable video, have standardized on a one hour fast charge routine.
  2. CELL FORMULATION - Because almost every professional application has standardized on a one hour charge routine, major cell manufacturers have formulated modern NiCd cells for maximum charge acceptance at this one hour or ‘C’ rate. When these cells are charged at the slow rate, they can exhibit reduced capacity with each such charge cycle. For example, a high performance NiCd cell from one major manufacturer delivered only 50% of its rated capacity after only 10 conventional slow charge cycles. (After 2 fast charge cycles this battery once again produced 100% of its rated capacity.) By virtue of this change in cell formulation the slow charge process as a primary means of recharging NiCd batteries has been rendered totally obsolete.
  3. HEAT AGING - The vital plate separators and cap seal of a NiCd cell are fabricated of organic components which deteriorate with age. As a matter of fact, separator failure and the resulting internal short circuit is one of the more common forms of NiCd end-of-life failure. Elevated temperatures will accelerate the decomposition of any organic material and batteries are no exception. Batteries should always be stored in a cool environment for optimum life. Conversely, heat is one of the major killers of batteries.
  4. Unfortunately, the slow charging process dissipates the continuing excess charge current as heat. An analysis of a variety of video batteries reveals that temperatures of 45_ to 55_ C are typical during extended slow charging. These elevated temperatures will cause the organic components of the cell to decompose at a rate 5 to 10 times faster than normal! In other words, a battery that would typically be expected to deliver two years of service would fail in as few as 3 months of extended slow charging. This accelerated heat aging is also a major problem with fast chargers that employ a trickle charge after the fast charge cycle is completed. (See Battery Life Section).
  5. RESTRICTED APPLICATION - Because of its inherent simplicity and constant current output, a slow charger must be dedicated to one specific voltage and capacity battery. A slow charger can be totally ineffective if connected to a battery with a greater rated capacity or slightly higher voltage than that for which it was designed. A much worse consequence results if a slow charger is connected to a battery with less capacity or fewer cells than its design specifies. In such cases the battery will be severely damaged or destroyed and there is a risk of fire.

For these and other reasons, the professional film and video industries do not employ slow chargers as a primary charge routine. A small slow charger makes an excellent emergency/back-up charger due to its compact size and low cost, however it must not be used as the primary every day charger.

FAST CHARGING

The extremely simple slow charger is based solely on the inherent design capability of many NiCd cells to effectively endure an overcharge at the slow charge ‘C/10’ rate indefinitely. If the overcharge current were greater than this ‘C/10’ rate, the cell would begin to produce oxygen at a rate much faster than it can absorb. The internal pressure would rise dramatically until the safety vent opened spewing forth gas and electrolyte. This venting process, accompanied by elevated temperatures and the possibility of a fire, would continue until the cell was destroyed. Clearly such a catastrophe must be avoided. Herein lies the critical difference between the simple ‘slow’ charger and the complex ‘fast’ charger. When using a charge rate greater than the ‘slow’ or ‘C/10’ rate, some very dependable means must be employed to accurately recognize the moment of full charge and then terminate or reduce the charge current to the ‘C/10’ rate or less before the cell is damaged or destroyed.

FAST CHARGE TERMINATION

In order to comprehend the criticality of this ‘fast charge termination’ procedure, consider that the popular one hour fast charge routine uses a charge current that is ten times greater than the slow or ‘C/10’ rate. Thus when the cell reaches full charge it will begin to produce oxygen gas at a rate 10 times greater than its maximum absorption capability resulting in a rapid and potentially catastrophic build-up of pressure and temperature. The fast charge termination or ‘cut-off’ is one of the most critical elements of a fast charger, and it is the inability of conventional fast chargers to dependably execute this function that is responsible for the universally accepted notion that "fast charging is bad for a battery".

In reality it is slow charging that is bad for the battery while fast charging is good for the battery. As previously discussed, all modern cell formulations ‘like’ to be fast charged and will deliver optimum performance when fed a one-hour charge rate under proper conditions. This situation is reminiscent of the old tale about the man who fell off the roof of a 20 story building and was not injured from the fall. However the sudden stop at the pavement killed him. Likewise, the problem is not ‘fast charging’ or the high current fast charge rate, but rather the failure to terminate this high rate of current once the cell is fully charged.

Accurate and dependable recognition of the full charge condition of a multicell battery under all conditions is extremely difficult, and until very recently virtually impossible. The various methods presently used to determine the full charge condition and the problems associated with each are as follows :

  1. VOLTAGE CUT-OFF [VCO] - This is the most popular method of fast charge termination. It is used universally in most original equipment chargers delivered by video equipment manufacturers and it is the only method that can be used with conventional two contact (+ and -) batteries. As can be seen from figure 3, the voltage of a NiCd cell steadily rises during the charge process. Upon reaching full charge, the cell begins to generate and reabsorb oxygen gas as previously described which causes the voltage to drop. In its modern form, a VCO charger uses a microprocessor circuit to monitor the charge voltage and terminate the fast charge current when this reduction in voltage is sensed. Such chargers are also called -ÆV ("minus delta vee") types because of this process. In addition, the microprocessor can also monitor and respond to other relevant characteristics of the charge voltage, which is referred to as ‘voltage algorithms’. All these methods that rely on the charge voltage for fast charge termination are generically VCO type chargers.
  2. Looking at fig 3, the voltage profile, and in particular its -ÆV aspect, appears to be a reliable and effective basis for determining the full charge of a NiCd battery. Actually, if video batteries consisted of one cell and were always charged under controlled conditions, this method would work just fine. Unfortunately every cell manufacturer states that the VCO method, and the -ÆV type in particular, becomes progressively problematical and unreliable as the number of cells in the battery increases and admonishes against relying on this method when charging batteries with 10 or more cells in series.

    In actuality, all professional video batteries actually consist of 10 to 12 cells in series and thus the problems associated with this type charger should have been anticipated and expected. The problems with this method are primarily related to temperature and cell imbalances.

    The pronounced rise and then dip in voltage (-ÆV) of figure 3 curve A is based on an optimized charge rate at room temperature. If the charge rate or the temperature deviates from these optimum values, the magnitude of the -ÆV dip may be reduced dramatically (figure 3 curve B) causing it to become unrecognizable to the charger termination circuit. Thus termination will not be properly executed which will destroy the battery and create a fire hazard. This problem often occurs with warm or hot batteries but is particularly acute with cold batteries.

    These -ÆV chargers can rarely recognize a cold battery resulting in one of two very undesirable conditions. The initial high impedance of a cold battery may create an immediate rise and drop in voltage when charging begins which prematurely triggers the "Full Charge" cut-off. This is why a battery from one of these chargers can sometimes have a "READY" indication and yet remain fully depleted. More typically, the charger does not receive a false trigger and delivers the full fast charge current to the cold battery as if it were at room temperature. Cell manufacturers clearly warn that this is the most dangerous thing you can do to a NiCd battery. A cold NiCd ( approx 40_ F or less) can not accept the full fast charge current and will generate hydrogen gas under these circumstances. When such a battery is removed from the charger or placed on a camcorder a spark can ignite the hydrogen gas causing the battery to explode . (See Safety Section)

    The -ÆV charger can not recognize or cope with cell imbalances either. The cells used in premium batteries are usually matched for capacity before assembly. At Anton/Bauer every professional battery is 100% computer tested for performance and cell balance with the computer print-out shipped with each battery. Nevertheless, the 10 or more cells within a video battery will eventually develop slight differences in capacity due to a multiplicity of factors including unequal rates of self discharge. As Murphy would predict, the probability that 10 to 12 cells will reach full charge at the same instant is virtually nil. As one cell is increasing in voltage toward the end of charge, another cell is decreasing in voltage, etc., etc., etc. Because the charger can only read the sum voltage of all these cells in series, the cells with rising voltages cancel out the reduction in voltage of those cells that have reached full charge. As a result the charger ‘sees’ a relatively flat voltage curve and misses the charge termination point. This is why the cell manufacturers are wary of using the -ÆV technique in such multi-cell applications. Based on this same syndrome, these type chargers can not cope with batteries that have "memory" or imbalances caused by high impedance shorts. Such batteries will either be destroyed, damaged, or result in a partial charge. (See Memory in the Problem Appendix)

    In addition to the hazards, it is clear from the forgoing why batteries charged on these type chargers appear so unreliable. Depending on temperature, balance, and many other factors, the battery may receive a reasonably full charge one day and a mere fraction of a charge on the next.

  3. TEMPERATURE CUT-OFF [TCO] - Upon reaching full charge, the continued charge current will begin to create heat inside the cell due to the oxygen absorption process. The subsequent rise in temperature in cells designed for this cut-off method is a very definite and reliable indication that the fully charged condition has been achieved. When properly monitored and analyzed this rise in temperature can be a very effective and dependable basis for a fast charge termination system. A TCO system must include the appropriate temperature sensors in the battery and an additional connection between battery and charger for the transmission of temperature data.
  4. Not all TCO systems are the same. Many systems employ a single temperature sensor at one point in the battery pack which assumes that all cells will reach full charge at about the same time. However, such a system can create serious problems if the cells are imbalanced in which case some cells can be undercharged while others can be damaged by overcharge.

    The unique All Cell Sensing system as used in all Anton/Bauer professional batteries utilizes a network of sensors that monitor the temperature of every cell in the battery. This system is the only safe and reliable method to address an imbalanced battery. When the first cell in the battery reaches full charge, its respective sensor triggers the charger to reduce the potentially damaging fast charge current. The charger then enters a ‘balance mode’ that computes the magnitude of a possible imbalance and provides a balancing or equalizing charge rate that will bring all remaining cells to full charge without damaging those cells that have already attained 100% charge. Once all cells are fully charged, the charger enters the patented Lifesaver mode that keeps the battery 100% charged and balanced indefinitely without the heat build-up and accelerated aging of conventional trickle chargers.(See the following topics in the Problem Appendix: Accelerated Self Discharge, Unbalanced Batteries, Equalizing Mode, and Maintenance Mode.)

    In addition to being an effective means of fast charge termination, temperature information can be extremely vital to many other charger functions. The relevance and accuracy of battery voltage data during charging is significantly improved when coupled with cell temperature information. Likewise, the charge acceptance factor that greatly influences battery performance is also very temperature dependent. The microprocessor of an InterActive battery/charger system uses the critical cell temperature along with other vital data to optimize performance and life as well as eliminate the safety hazards of cold temperature charging.

  5. DELTA TEMPERATURE CUT-OFF [DELTA TCO (DT/dt)] - The most advanced TCO type system is employed in the Anton/Bauer Digital InterActive battery. The Digital battery contains special temperature sensors which convey real time, temperature information to the charger’s microprocessor allowing the charger to analyze the rate of temperature change of the cells in the battery pack. This analysis is then used to determine a precise fast charge cut-off point which is more accurate than either VCO or standard TCO methods. This advanced cut-off method is required for safe charging of the new Ni-MH (Nickel metal hydride) cells and is already a feature of the Anton/Bauer Digital InterActive battery and charger.
  6. DIGITAL OR FULL BATTERY CUT-OFF [FUL] - Another feature only available with the Anton/Bauer Digital InterActive battery and chargers is the FUL cutoff. Due to the InterActive technology, an Anton/Bauer InterActive battery can relate it’s own state of charge to the microprocessor in the charger. Therefore, when a battery reading 100% in it’s display is placed on the charger, no fast charge current is needed to bring that battery to one of the aforementioned cutoff methods. The battery merely tells the charger to enter the patented Lifesaver mode to keep it at the 100% charged level without adding any additional heat to the battery, therefore prolonging the life of the cells.
  7. COMPUTATION (or CAPACITY) CUT-OFF [CCO] - The CCO or Computation method of fast charge termination is a very dependable complement to either the TCO or the VCO systems. This pre-determined charge profile is established prior to the start of the charge cycle by the charger’s microprocessor during the battery evaluation phase. By recognizing the battery's cell formulation, temperature, rated capacity and number of cells, the InterActive charger's microprocessor will select a fail-safe maximum charge profile from its database. The charger continuously monitors the charging process against the battery's maximum charge profile and will terminate charge automatically if this profile is exceeded.

An explanation of these five termination methods usually prompts the question : "Which one is best"? And the answer begins with "none of them". Each method has its strong points and a specific range over which it is effective, however none of them are totally safe and dependable over the full range of conditions that are normally encountered in the professional film and video industries.

Voltage Cut Off systems, including microprocessor ‘voltage algorithm’ types, are reasonably effective under ideal conditions but can be extremely unreliable and hazardous if the battery is cold or imbalanced. The TCO techniques as exemplified by the Anton/Bauer ACS and Digital InterActive battery systems are extremely effective and are the only safe methods that can charge cold or imbalanced batteries. The CCO method is a safe and reliable ‘back-up’ system and is effective under a wide range of conditions, but because it is a ‘computation’ method it lacks the accuracy requisite for use as a primary cut-off method.

The final answer to the question of which termination system is best is "All of them together". While all conventional chargers employ only one charge termination method, Anton/Bauer InterActive Microprocessor chargers include all five types of termination systems which operate simultaneously and independently. Each battery includes a complex network of sensors and logic circuits that provide the charger microprocessor with the critical temperature and cell data to facilitate an accurate TCO, Delta TCO, temperature correlated VCO, FUL or CCO cut-off . The charger monitors all these systems simultaneously and will accurately terminate the fast charge when any one of these systems recognizes the full charge state. This fail-safe multi-redundant technique utilizes the strengths of all these methods while it precludes the inherent weaknesses of any one system. This is the only system that is safe and effective over the entire range of possible conditions.

CHARGE ACCEPTANCE

As mentioned above, a battery is not a "fuel tank" but rather an organic system that will efficiently store energy by an internal chemical transformation when fed electric current (charge rate) in a precise manner and under specific conditions. When these specified charge rates and conditions are not met, the internal chemical transformations do not proceed in their normal manner. Under certain conditions the normal chemical transformation will cease altogether and all the charge current will be diverted into secondary reactions that result in no energy being stored at all. These secondary reactions include the formation of explosive gas as well as destructive heat.

It is ludicrous to expect reliability from a charger that just throws out a fixed electric current without any regard to the critical conditions and parameters that affect the chemical transformation. Yet virtually all conventional chargers do just that. Charging a battery with one of these conventional non-interactive chargers is nothing more than a game of chance.

Among the major factors affecting 'charge acceptance' (the ability of a battery to store the energy delivered by the charger) are temperature, cell formulation, and the rated capacity (size) of the cell. The dire consequence of a charger ignoring these factors can be deduced by analyzing just one element of the complex charge routine : average fast charge current. Consider the following facts taken directly from cell manufacturers’ specifications:

  1. For a given cell, the fast charge rate must be adjusted by a factor of over 1,000 % according to prevailing temperature in order to assure optimum charge acceptance and remove the danger of explosion.
  2. Given a particular size cell, the fast charge rate must be adjusted by a factor of over 500% according to chemical formulation and plate structure (sintered, pressed metal, etc.)
  3. Fast charge current for a particular cell formulation and temperature is directly proportional to cell size or rated capacity. Since professional video batteries utilize cells in the range of 2 AH to 8 AH, this represents a corresponding variation in charge current of another 400%.

From these three specifications it should be clear that based upon the size, formulation, and temperature of the cells, the safe and optimum charge current would have to be adjustable over a range of 200 to 1 or 2,000 %. This means that a conventional charger with its single fixed fast charge rate can be delivering up to 200 times too much or too little current to a battery according to the safety and performance specifications of the cell manufacturer. The poor performance and life associated with using these type chargers should no longer appear to be such a mystery.

INTERACTIVE CHARGE TECHNOLOGY

The basis of InterActive charge technology is very logical and simple: each battery actually controls its own charge process according to its size, chemical formulation, temperature and all the other parameters and conditions that affect charge acceptance in order to optimize performance, safety, and overall life. The battery of an InterActive battery/charger system features a network of sensors and logic circuits that can generate all the vital data necessary to create an optimized charge routine. Through a special communication link, the interactive charger responds to this data by delivering a charge profile that perfectly matches the cell manufacturers specifications under the prevailing conditions. All elements of chance and the risk of uncharged batteries, fire, and explosion are removed.

In addition to dependable performance, safety, and prolonged life, this interactive technology is also the basis for a new concept in battery system management. Batteries have always represented an inordinately large percentage of video maintenance time. By comparison, modern cameras and recorders require little attention and a stock of fresh video tape is easy to maintain. Only the battery is an unknown consumable that can cause unpredictable disruptions when they fail. How do you keep track of the age, recent performance, and use pattern of a battery in order to identify a potential problem before it becomes a failure in the field?

The high level of intelligent data available from the battery and microprocessor charger of an InterActive system can facilitate a very sophisticated and completely automatic maintenance program. InterActive chargers with built-in or accessory diagnostic units can automatically test batteries for capacity, voltage profile, and all other major parameters. Through an LCD or attached printer, these sophisticated units can automatically identify all battery anomalies including loss of capacity, voltage depression, bad cells, "memory", and accelerated self discharge. Potential problems can be easily identified before they cause disruption in the field.

DIGITAL INTERACTIVE TECHNOLOGY

The latest Digital InterActive battery/charger systems provide the ultimate in charging and diagnostic capabilities. Each Digital battery features a built-in diagnostic program that automatically calibrates and analyzes battery performance every time it is used. A "Service" icon will be displayed in the intergral LCD if any potential problem or anomaly is detected. In addition the Digital battery can display and print out its serial number, date of manufacture, number of charge/discharge cycles to date, present calibrated capacity, and other pertinent parameters. The task of managing a large battery inventory is practically eliminated with this new Digital battery system. Not only are potential battery problems automatically identified, but batteries due for end-of-life replacement can be pulled from service before they fail in the field. The Digital diagnostic program also performs service analysis which indicates when a battery should be returned to the manufacturer for warranty repair or replaced with a new battery based on the delivery of its full rated life. The Digital InterActive diagnostic system eliminates the major equipment management task of ENG/EFP while providing the highest level of charging accuracy and dependability. The Digital battery also provides important features for the cameraman which are covered in the Digital Battery Section.


BATTERY LIFE

The overall life expectancy of a rechargeable battery is greatly influenced by a myriad of factors which have been frequently responsible for reducing the life of a NiCd to less than 30% of its theoretical maximum. There are many video professionals that accept the fact that a NiCd battery appears dead after only 6 months or a year. In reality, a high quality NiCd battery should deliver a full two years of operation while the advanced heavy duty Propac InterActive battery can deliver more than double this operating life. Most of the factors affecting life have been addressed throughout this handbook under the associated headings. The following is a compendium of the major factors influencing battery life with recommendations for optimizing each.

Heat - Batteries should not be exposed to elevated temperatures. Heat greatly accelerates the aging process and can reduce battery life by more than 80%. Whenever possible keep batteries at room temperatures. In extremely hot climates, keep batteries out of direct sunlight where possible and return batteries to an air conditioned environment at the earliest practical opportunity. Avoid leaving batteries for extended periods in an enclosed van or the trunk of a car. Common sense can easily predict the many other elevated temperature situations that should be avoided.

The charger can often be the worst elevated temperature environment for the battery. Improper charge termination and a trickle charge can create extremely high temperatures which are maintained indefinitely while the battery is on the charger. An InterActive battery/charger system with accurate temperature sensors and the Lifesaver maintenance mode will preclude this common form of heat damage. If you are not using an InterActive battery/charger system, feel the temperature of a battery that has been on the charger for about 20 hours or longer. If it is warm or hot to the touch, it is being prematurely aged by a trickle charge. (If it is at room temperature, it probably is receiving no maintenance charge and will thus experience self discharge).

During storage for periods greater than a few weeks, batteries should be wrapped in a sealed plastic bag and placed in a refrigerator. Before being returned to service, the batteries should be allowed to achieve room temperature before being removed from the plastic bag. Once at room temperature, the batteries should be charged on an InterActive charger in order to equalize and compensate any minor self discharge. If an InterActive charger is not available, charge the batteries overnight (14-16 hours maximum) on the proper slow charger designed specifically for that battery. Do not use a conventional fast charger which has no means for addressing imbalances.

Charging - The charging process has a great influence on battery life. For maximum life every battery requires a specific charge profile for a given set of conditions. Any deviation from this optimum profile will have an adverse affect on battery life. As an example, two identical batteries were charged with seemingly identical chargers which provided similar performance during the operational life of the batteries. However one battery delivered twice the number of cycles and twice the length of service of the other due to a slight variation in charge routine. In extreme cases, an improper charge regime can destroy a battery and create a hazard. As previously explained, only an InterActive battery/charger system has the ability to identify and create the proper charge profile required for maximum life and performance.

If using a battery and/or charger that is not part of an InterActive system, the following guidelines will help prevent extensive life reduction.

  1. Do not connect a battery to a charger unless the label on the units specifically verify such compatibility by model number. If such verification is not present, the manufacturer of both the battery and charger should be consulted. (While a charger may appear to be correctly charging a battery, an improper charge rate or charge termination profile can adversely affect life in addition to impairing performance and creating a hazard).
  2. Avoid so-called "equivalent" replacement batteries or "re-built" batteries. While such replacements or re-builds may ‘look’ identical to the original, the internal cells typically differ from the originals for which the charge regime was optimized. Unfortunately such life reducing incompatibility does not show up until the battery dies in a fraction of the expected time. This and other internal differences can also reduce performance as well as create a serious safety risk.
  3. Do not use slow chargers as a primary means of recharging and avoid fast chargers that utilize a continuous trickle charge (see Heat above).
  4. Maintain adequate air circulation space between batteries when charging more than one battery at a time. Never group batteries together where they are touching each other during charging.
  5. Do not routinely use so-called ‘dischargers’ or ‘conditioners’ before recharging.(See ‘Discharge-Before-Charge Section’ in Problem Appendix)

Discharge Rates - The life of a battery can be significantly affected by the relationship between the size of the battery (rated capacity) and the rate of discharge. For a given size and type battery, higher discharge currents will reduce overall life expectancy while lower discharge currents will enhance battery life. (This is primarily due to internal impedance and heat).

As this rule applies to video, the life expectancy of a battery will not be adversely affected by a power consumption that is approximately half that of the capacity of the battery in watt-hours. For example, a 25 watt camcorder will have very little impact on the life of a battery rated at 50 watt-hours or greater. However, as the power consumption approximates the capacity of the battery or greater, life expectancy will be diminished. As a comparison, 50 watt-hour batteries powering the aforementioned 25 watt camcorder may provide months of additional service after 25 watt-hour batteries in the same application have expired. Thus for maximum life, as well as the previously stated practical reasons, select a battery with twice the rated capacity of the power consumption.

Over Discharge - Discharge current must never be allowed to continue after the battery has reached the EODV or end of discharge voltage. Running a camcorder or especially a light while the battery voltage is below the EODV can create a condition known as reverse polarity which will irreparably damage the battery and reduce its overall life. (See Problem Appendix). Therefore, never leave a battery powered piece of equipment unattended while it is running. Moreover, always change to a fresh battery as soon as a ‘low voltage warning’ appears or a light begins to noticeably dim.

Physical Shock - Transporting batteries unrestrained in a large case or loosely in the trunk of a car can create extremely high impact forces that will create conditions that will adversely affect both life and performance. In addition to selecting a ruggedly designed battery, always transport batteries in a fitted case or compartment. Maximum life will be attained when batteries are not dropped or excessively submitted to severe impacts.

Voltage Misapplication - This topic was covered in detail in the ‘Voltage’ section. But do not forget that using a "12 volt" nominal battery in professional video applications can create conditions that render the battery useless long before it reaches the end of its expected life. The full life expectancy of a battery can only be achieved when it is properly voltage matched to the equipment it is powering.

Cell Type - Life expectancy is also a function of cell type. Certain cell formulations and constructions will trade-off overall cycle life for other attributes such as power density or cost. Before selecting a battery, make sure you are aware of its life expectancy relative to its other specifications and to those of other similar batteries. (See also Cell Formulation Technical Section under: Battery Design Features).


SAFETY HAZARDS

Based upon proper battery and charger design, the operation and charging of NiCd batteries is extremely safe. Conversely, life threatening explosions and serious fires can result from failure to follow the explicit safety guidelines presented by the cell manufacturers. Unfortunately the great majority of battery and charger manufacturers have responded to these critical safety hazards by merely printing small warning disclaimers on their equipment and in the instruction manual rather than designing safe equipment that would prevent these hazards from occurring. If these warnings and danger labels are ignored, serious damage and injury can result. All users of rechargeable batteries should therefore be acutely aware of the following dangers.

Cold Temperature Charging

The fast charging of a cold battery is one of the most dangerous hazards associated with NiCd batteries and can result in a violent explosion. When a NiCd is fast charged at temperatures below +41_ F (+5_C ), the internal charging reaction can not proceed normally and a significant portion of the charge current can be diverted into producing highly explosive hydrogen gas. Cell manufacturers emphatically state that to avoid the risk of hydrogen gas explosion the fast charge current must be reduced or terminated when the temperature of the battery is below +5_C. Despite this danger, every conventional NiCd charger now being manufactured can not properly identify a potentially hazardous cold battery and can deliver to cold batteries charge currents typically 10 times greater than the safety limits set by the cell manufacturer. When the charger manufacturer warns: " Charge batteries that are between +5_C and +40_C only" he is not kidding.

The typical explosion scenario usually results from someone inadvertently leaving one or more batteries outside in a cold car or truck overnight, or coming in from an outdoor assignment on a cold day. In both cases the batteries are immediately put on the fast charger where the fast charge current will produce prodigious amounts of hydrogen gas. Due to its small atomic dimensions, hydrogen is highly permeable and will seep through the seals of the cell or exit directly through the vent if pressures are high. At this point the hydrogen gas from all the cells has accumulated inside the battery case. Removal of the battery from the charger or placement onto the camcorder can create a spark that will ignite the gas causing an explosion that can turn the battery into a fragmentation grenade. It is therefore crucial that everyone involved with recharging batteries be aware of this danger and understand that cold batteries must be allowed to reach room temperature before being placed on a charger.

Anton/Bauer engineers believe the risks of injury from cold temperature charging are too great to be relegated to a warning label that most people rarely see. Therefore every Anton/Bauer professional battery has a unique cold temperature protection circuit . There is never any risk of danger if a battery that is below the safe fast charging temperature is placed on the charger. The cold temperature safety sensor in the battery mates with the charger safety programs which then automatically control the charge rates to remain well within the safe limits specified by the cell manufacturers. Thus when using an Anton/Bauer system, the threat of cold temperature hydrogen explosions are virtually eliminated.

In addition, all Anton/Bauer chargers include special safety programs and a spark prevention circuit which address non-Anton/Bauer batteries that may be placed on the charger. However, while these precautions significantly reduce the risk of gas explosions, they do not provide the absolute protection of positive temperature measurement and interactive charge control. Again it must be stressed, except when using an InterActive battery with its cold temperature protection circuit on a complimentary InterActive charger, a cold battery should always be allowed to reach room temperature before being placed on a charger.

Fire Hazards

Unfortunately conventional NiCd batteries and chargers have been identified as the source of several fires and toxic smoke incidents over the years. After one such incident that almost resulted in tragedy, a major television network mandated that cameramen not charge batteries in their hotel room. An understanding of the conditions that can cause these disasters and the use of properly designed batteries and chargers can virtually eliminate any possibility of a fire or smoke hazard. The cause of all fire and smoke incidents can be basically grouped into three categories:

  1. Improper Fast Charging - The vast majority of incidents can be traced to a fast charger that has failed to recognize that the battery has reached full charge. As explained in the Charger Technical Section, one of the most critical functions of the fast charger is to recognize the moment that a battery reaches full charge in order to terminate the high fast charge current. Failure to terminate the fast charge current on time can have catastrophic ramifications. The continuing high current, which is typically 10 times greater than a fully charged cell can tolerate, produces inordinate amounts of heat. Unfortunately the fast charge termination method used by all conventional fast chargers (see VCO) is susceptible to error under many circumstances and is typically the cause of most fire and smoke incidents.
  2. In addition, most battery manufacturers use cells with PVC plastic insulating sleeves which unwittingly exacerbates the risk of serious fire. This type plastic has a low melting temperature and the heat of extended overcharge causes the insulating sleeve to shrink and split exposing the bare metal cell which instantly causes a catastrophic short circuit and fire hazard.(See Short Circuits below).

    The risk of fire and smoke injuries from fast charging can, and should, be eliminated. As explained in the Charging Technical Section, a properly designed system includes multiple thermal sensors in the battery which interface with a redundant charge termination system that includes a Temperature Cut-Off (TCO). This totally precludes the possibility of dangerous heat generation from overcharge thus removing the major cause of fire and smoke. As an additional redundant precaution, cells with fibre insulation instead of the standard PVC plastic should be used. This removes the possibility of an internal short circuit even if for some reason temperatures should rise above normal. A safely designed battery should also include a thermal fuse in the power circuit which will disconnect the battery from the charger or any other external device in the event that dangerous internal temperatures are detected.

  3. Slow Charging - A slow charger is a very simple device that delivers the correct and safe rate of charge current only when it is connected to the specific model battery for which it was designed. If a slow charger is connected to any other battery, particularly one with fewer cells, less capacity, or a lower maximum continuous charge rating than that for which it is designed, the battery could generate an abnormal amount of heat that may be sufficient to cause the identical hazards as outlined above under "fast charging".
  4. Cells with fibre insulation instead of plastic sleeves and the use of thermal safety fuses and fire retardant materials will significantly reduce the risk of a disaster. However a significant mismatch between battery and slow charger can still present a real hazard. A wide variety of compact slow chargers use the identical standard case which can easily mislead operators into believing that two slow chargers with very different electrical characteristics are interchangeable. The label on a slow charger should therefore be carefully matched to the label on the battery for compatibility before the two are interconnected. A safely designed battery connected to its designated slow charger should pose no fire or smoke hazard.

    As a last precaution, for safety as well as reasons of battery performance and life, batteries should always be charged in a position that maximizes free air circulation. Specifically, batteries should not be grouped close together or left in a bag or case during either fast or slow charging. Likewise, other objects should never be placed on top of charging batteries.

  5. Physical Shock and External Short Circuits - Low internal resistance is a desirable characteristic of a NiCd battery. However, this can become a hazard by releasing incredibly high rates of current if the battery is inadvertently short circuited. Such high currents can instantly transform internal wires and connecting straps into red hot elements causing the battery to burst into flames. This has been known to happen when a battery is accidentally dropped. In such cases the impact causes an internal collision between two or more cells sufficient to tear the thin insulating sleeves thus creating a direct short and instant fire. A pinched wire can create the same disaster.
  6. It has been shown that this type hazard can be effectively eliminated through preventative design measures. Heavy duty fibre type cell insulating sleeves should be used as they can survive repeated impacts that would cause plastic sleeves to fail. While more rugged insulating sleeves are highly desirable, the best approach is to prevent major impacts from reaching the cells or creating movement between the cells. As discussed in the Battery Construction Section, a high impact thermoplastic unitized case will perform this function . It is also important that all power conducting wires and straps are channeled in a manner to prevent chafing or pinching under impact.

    An external short circuit can create the same fire hazard as an internal short, however this is more easily avoided. The external power contacts should be recessed and the battery should include an externally replaceable and/or internal resetable fuse in the power circuit.

(All Anton/Bauer InterActive battery/charger systems comply to all the safety recommendations suggested in this Safety Hazard Section).

WARNING: Based upon reported incidents, so-called "equivalent" replacement batteries and "re-built" batteries can represent a serious safety risk. After purchasing a battery and associated compatible charger, another manufacturer may offer replacement batteries that are "identical to your original batteries", or offer to re-build your original batteries to "like new" conditions. Such replacement or re-built batteries are at best a misrepresentation and at worst a potential hazard.

Replacement or re-built batteries may ‘look’ identical to the original, and often re-use the original manufacturers cases, however the internal components, assembly techniques and quality control are almost always quite different. As an example, quality and safety specifications for the insulation, wire harnesses, safety sensors, thermal fuses, and electronic safety circuits of an original Anton/Bauer battery are not matched in the product provided by replacement manufacturers and rebuilders. In addition, the cell type and formulation is almost always different from the original for which the charger has been optimized. Unfortunately such hidden differences do not become evident until it is too late. Initially these replacements or re-builts only appear to be "equivalent", while the internal differences will eventually result in reduced performance and a life span that is usually half that of the original battery. Most critically, these internal differences pose a serious safety risk that have resulted in fire and explosion. Having invested in a safe and compatible battery/charger system, it is hazardous (as well as uneconomical) to utilize batteries not produced by the charger manufacturer.


COLD CLIMATE PRECAUTIONS

A portable video system that delivers satisfactory performance at normal temperatures can be rendered totally useless by cold temperatures. Cold temperatures below 40_F (+5_C) can also create serious battery hazards. Following the steps below will assure safe and optimum battery performance in cold climates.

  1. Do Not Use 12 volt Batteries The use of 12 volt batteries (BP-90, NP types, etc) is one of the most common causes of cold temperature video problems. The Voltage chapter covered in detail the problems of using 12 volt batteries however cold temperatures severely aggravate this situation. Due to the increase in internal cell resistance and the greater power drain of equipment at cold temperatures, batteries will operate at the lower end of their voltage range. From figures 1 & 4 it is clear that this does not create a problem for 13.2 volt or 14.4 volt NiCads which will always deliver 100% capacity. However 12 volt batteries which already yield only 60% to 80% of available capacity at room temperatures may deliver less than 25% at cold temperatures because they are operating almost totally below the cut-off voltage of the equipment.
  2. Keep Batteries Warm - Cold temperatures will adversely affect the normal electro-chemical reactions within the cells resulting in reduced available capacity. This loss of capacity can be minimized by keeping batteries warm during and prior to use. Fully charged batteries at room temperature can be placed in an insulated ‘cooler box’ or a heated vehicle until they are needed. When shooting in extremely cold climates, the operator should wear the battery under the outer garments and as close to the body as possible. This is easily accomplished with the Anton/Bauer system by wearing the UniPac belt accessory which includes the same Gold Mount that is standard on all professional cameras. This allows the normally camera/camcorder mounted Anton/Bauer battery to be conveniently worn under a coat.
  3. Use Proper Capacity Batteries - As explained in the Capacity chapter, the normal rule for selecting the proper battery for a camera/camcorder requires the battery to have a capacity in watt hours that is at least twice the power rating in watts of the equipment. Adhering to this rule becomes more critical at low temperatures. Small slide-in type batteries have more than twice the internal resistance and will be adversely affected to a far greater extent by cold temperatures compared to a heavy-duty battery such as the 60 watt hour Anton/Bauer Pro Pac. A small battery that was marginally acceptable at normal temperatures will thus be unsatisfactory under cold temperature conditions. A small battery that is also only 12 volts is a particularly disastrous combination for cold temperature applications.
  4. Never Put a Cold Battery on a Charger - (except for the Anton/Bauer InterActive system - see #5) - Charging cold batteries can result in a multitude of problems and disasters (See the Safety Hazard chapter). In addition to the risk of a violent explosion, the battery may accept very little or none of the charge current.
  5. Conventional chargers receive no temperature information from a battery and therefore deliver the standard and potentially dangerous fast charge current to a cold battery which will always result in one of the following problems and hazards:
    1. A - The charger delivers a standard charge regime to the cold battery resulting in reduced capacity, potential damage to the battery from electrolyte venting, and the risk of injuries from a hydrogen gas explosion.

      B - The charger indicates that the battery has been fully charged and is "Ready" yet the battery in reality has not been charged at all and will not run a camcorder for even five minutes. This common cold temperature problem of all conventional chargers results from the unfortunate similarity between the voltage profile of a normal battery at full charge and a cold battery at the beginning of charge. A depleted cold battery thus fools the charger microprocessor into thinking it is fully charged.

      C - The charger indicates "Faulty" and the battery has not been charged - This is a common occurrence with those chargers that include a "Faulty" indicator light and circuit. NiCads at cold temperatures can create a voltage profile that confuses these chargers which then refuse to charge the battery with the resultant "Faulty" indication. Unfortunately these chargers take a few minutes before defaulting which leaves an operator thinking the batteries are going to be charged normally.

    To avoid these inevitable problems and hazards, always allow cold batteries to reach safe and optimum charging temperatures (10_C -30_C / 50_F -85_F) before placing them on a fast charger. Depending on the severity of the climate, cold batteries can be expected to reach safe charging temperature after one to three hours at room temperature.

  6. Use Anton/Bauer InterActive Batteries and Chargers - All Anton/Bauer professional batteries include a unique temperature sensing network that sends accurate temperature information and other vital battery data to the charger (see Cold Temperature Charging p. 30). The charger microprocessor uses this data to create a safe and optimum charge profile under all conditions. A cold battery is easily identified by the charger which automatically initializes a special "Cold Battery Charge Mode" that always brings the battery safely to a full charge. Cold Anton/Bauer batteries can be confidently placed on a corresponding InterActive charger without the fear of the hazards, unreliability, and problems of conventional cold temperature charging as outlined in #4 above.
  7. Equipment Temperature - If cold climate shooting requires only short exposures to outside temperatures (5 to 10 minutes at a time), cameras and recorders can be kept warm and returned to a room temperature environment immediately after each outside excursion. However, for extended outside shooting, once equipment has stabilized at the outdoor temperature it should be allowed to remain at the cold temperature and not be periodically brought into a warm area in order to preclude lens condensation and VCR dew/moisture problems.
  8. Winterization of Equipment - When planning a major project in a cold climate such as the Winter Olympics or an Arctic documentary it may be prudent to contact the respective equipment manufacturers concerning specific cold climate preparations and precautions. This is particularly important for motion picture cameras.
  9. Take Extra Batteries - Despite all the aforementioned precautions, the cumulative effects of cold temperature on equipment and batteries is bound to have some effect on power efficiency, so it is always a good idea to have additional back-up batteries in cold climates.

PORTABLE LIGHTING

The latest video camcorders are technological marvels that bear little resemblance to the crude tube devices of the seventies. With the evolution of advanced CCD chips, digital signal processing, and now digital recording formats, you would assume that video images being viewed today are quite superior to those of a decade ago. Unfortunately this is often not the case.

The quality of ENG/EFP images is now worse than it was ten years ago in many instances. The reason for this is that engineers have been improving every element of the video camera except the most critical. The camcorder only records the image; it is light that creates the image. The latest CCD cameras have such high sensitivity and low noise that cameramen are encouraged to shoot with available light in almost any situation. And indeed this is exactly what most do, especially since the advent of the one man crew. The problem is not the quantity of light, but rather the quality of the light. Available light almost always involves ceiling fixtures with virtually all illumination coming from above. While this type of illumination is satisfactory for the background, it creates a disaster in the foreground. The horrors of available light are familiar to everyone : dark eye sockets, glowing noses, giant chin shadows, radiant foreheads, and exaggerated wrinkles. It’s not a pleasant sight.

There have been attempts to solve this problem in the past with camera mounted lights, however the images produced are as ghastly as those with no light at all. The 100 to 250 watt bulbs used in these lights totally overpower the subject with an unnatural search-light effect reminiscent of interrogation scenes in 1940s movies. In addition, this bright foreground causes the lens to close down making the background dark and muddy. Lastly, cameramen hate these lights because of the additional weight and bulk of the light and battery belt, and after waiting so long for the development of the one-piece camcorder, the last thing they want to do is attach a dangling cable to it.

An elegantly simple solution to this available-light problem has now gained wide spread popularity. It is a tiny camera mounted ‘fill light’ that is designed to perfectly fill and thus remove the shadows created by overhead lighting. The concept for such a light is easy to understand. According to architectural specifications and actual location measurements, virtually all interior locations are lit to within one f-stop of 40 foot candles. A survey of video professionals further revealed that the vast majority of ENG ‘stand-ups’, interviews, and foreground action always occurs within 1 to 2 meters of the camera. The perfect fill light must thus produce about 40 fc at approximately 1-2 meters (5 ft.) with a beam angle sufficient to cover all popular lenses. A light output greater than 40 fc from the camera position overpowers the available light creating the flattening "searchlight-in-the-face" look and also causes the lens to iris down making the background muddy. Likewise, significantly fewer than 40 fc of light from the camera will not effectively remove the shadows which are by definition those areas that are not receiving the 40 fc of available light from above. Studio lighting "models" the subject with light from both the front and above in comparable proportions which is exactly what the "40 fc perfect fill" does in conjunction with the existing ceiling light. These are the first lights designed to work with available light to create studio quality video.

The visual improvement from such a light is phenomenal. The subtle ‘fill’ from this light perfectly matches the existing available light and miraculously removes all offending foreground shadows without affecting background clarity or exposure. No verbal account can begin to describe how this simple ‘fill’ can instantly transform any available light location from a shadowy nightmare to an apparently ‘studio lit’ scene.

In addition to successfully meeting the visual criteria, the Anton/Bauer Ultralight also overcomes all the other practical problems of previous lights. By utilizing a high efficiency and precisely angled reflector, the Ultralight consumes 30% less power than conventional lights of equal illumination. As a result the required 40 fc of light is achieved with only 25 watts. (Now it is clear why those 250 watt lights were so horrible; they were using 10 times too much power.)

With such low power drain, this small light can be powered from the same battery that powers the camera or camcorder. Such a configuration eliminates the need for dangling cables or additional battery belts. A PowerTap socket allows the light to be plugged directly into the battery mount at the rear of all professional cameras. (Most professional cameras include the Gold Mount directly from the manufacturer, however there is a Gold Mount available for every major camera and camcorder). The additional current drain of the light should not have a significant impact on battery run-time. A battery providing 2 1/2 hours of operation will still deliver almost 2 hours with an Ultralight in a typical ENG situation.

This fill light is not really an "accessory" for an ENG/EFP camera but rather a "necessity" for professional quality video and most major professional cameras/camcorder manufacturers are now making such fill lights an integral part of the camera design. Working in close cooperation with camera/camcorder manufacturers, the Ultralight 2 is designed to be manufactured into the handle of any camera or camcorder, and can be controlled automatically by the VCR ‘Rec’ button to turn on and off simultaneously with the VCR. This Automatique&trade; feature elimates wasted battery capacity and, together with the low power consumption, allows this light to be powered directly from the camera battery without any significant reduction in camera run time. When it comes time to put the camcorder back in the case, or if the light is not needed, the lamp base folds into the handle and completely disappears.

While the built-in ULTRALIGHT 2 is a standard feature on many new camera designs, those with current model cameras and camcorders can also experience the benefits of this system with an ULTRALIGHT 2 that can be easily attached to the handle of any camera. When not in use, the light base folds down to a mere 1.5 inches and remains connected to the Power Tap® receptacle found on all Anton/Bauer Gold Mounts which provides power directly from the camera battery. (Most professional cameras include the Gold Mount directly from the manufacturer, however there is a custom Gold Mount available for every major camera and camcorder). A Custom Gold Mount with the Automatique circuit included is available for many applications which allows the VCR button to control the on/off function.

The use of a 25 watt ‘fill light’ powered from the camcorder battery should not have a significant impact on the selection of your battery/charger system. In most cases the battery system recommended for a specific application will not be changed by the addition of a low power fill light. However, the following guidelines should be considered when using a camera mounted and powered light.

  1. Do not ‘cheat’ on the aforementioned 2-hour minimum run-time rule. The watt-hour capacity of the battery should be a minimum of 2 times the power consumption rating of the camera/camcorder and preferably slightly greater.
  2. In light of the above rule, you may want to consider a battery system consisting of two different size batteries. A larger capacity, heavy duty type for indoors where fill light is needed, and a smaller capacity for outdoors assignments. As an example, a 23 watt camcorder should be matched with a 2 x 23 or 46 watt hour battery. While a Compac Magnum battery (44 watt hours) may be quite satisfactory for outdoor (no light) assignments, a Pro Pac&trade; at 60 watt hours would be a much better choice when a fill light is being used. Thus a system consisting of two Compac Magnums and two Propacs and one 4-position Magnum Quad charger would be perfect for such an application, and is indeed a popular configuration.
  3. Surveys have shown that the additional power drain of a fill light is relatively insignificant except when the cameraman inadvertently leaves the light on when tape is not running. It is important therefore to develop the habit of turning the light off immediately after the tape is stopped. A better alternative is the Ultralight ‘Automatique’ circuit which can be retrofitted to many popular cameras and camcorders. This feature is built into an Anton/Bauer Gold Mount and couples with the VCR ‘roll’ circuit in the camera. The light can be controlled manually or automatically, turning on/off with the VCR button on the camera which eliminates wasted power.
  4. For greater distances from the camera to the subject, additional light output may appear to be needed. However in most cases this does not mean that a higher wattage bulb is necessary. Utilizing ‘spot’ type bulbs and focus adapters, the light output can be increased by more than 10 times with no increase in wattage. When distance between camera and subject increases, the lens is usually at a longer focal length or more narrow viewing angle. By matching the beam angle of the light to that of the lens, an enormous percentage of the light that would otherwise be wasted is now concentrated onto the subject.

As an example, most flood style fill lights are designed to cover the angle of a 9mm wide angle lens. Now consider such a 25 watt flood light with a typical ENG lens that is zoomed-in a mere 20% or so. At only 36mm about 94% of the flood light now falls outside the image area and is wasted, while only 6% of the light is actually falling within the viewing area. Matching the beam angle of the light to that of the lens will put 100% of the 25 watt light back in the scene, while the alternative to achieve the same illumination level would require the light output of the flood bulb to be increased from 25 watts to 400 watts!

While the 25 watt bulb will cover the vast majority of interior ‘fill’ situations, there are several instances where additional wattage and light output may be required. These include the following:

  1. Outdoor "Daylight Fill" - In many cases a subject outdoors will be in an area or position that is getting less light than the background or one side of the face may be more highly illuminated than another. This is basically the same situation as indoor fill except the illumination level to be filled may be 20 or more times as bright . This situation can typically be addressed by an 85 watt spot (narrow beam angle) with a dichroic ‘daylight’ color filter. Such an arrangement, which is almost equivalent to an old inefficient style 30 volt 250 watt ‘sun-gun’, can typically provide an "f- 8" lens stop at a reasonably close distance.
  2. Distant Interior Wide Angle - The 25 watt universal fill light can cover an individual or typical "two-shot" (interviewer/subject) at any distance up to about 10 feet (3 meters). However, to cover a larger group of people (wide angle lens) at distances of 13 to 20 feet (4-6 meters) will require an 85 watt flood set-up (an 85 watt flood bulb or 85 watt spot bulb with wide angle adapter). In those rare instances where a large group at 20 or more feet from the camera must be covered, a quick switch to a 200 watt 30 volt head module may be required. Such a bulb can be powered by a standard "30 volt" (28.8 volt) battery belt, or two regular ProPac 14 video batteries with the special "30 volt" lighting holder.
  3. Exterior Night - The most prolific use of the old style 250 watt ‘sun-gun’ occurred at night covering "disaster scenes". However in light of the most recent advances in CCD and camera technology, high-voltage/high-wattage lights are no longer recommended for optimum video quality in these situations. Contrary to the popular conception, less light should come from the camera as an exterior scene gets darker. A bright light from the camera at night will produce flat video and destroy background detail. Greater realism, clarity, and overall quality can usually be achieved with the lower power 25 watt bulb even if 6 dB or 9 dB of gain is necessary.

PROBLEM APPENDIX (with Solutions)

Batteries appear to be the most misunderstood aspect of professional video, possessing a "complex personality" that over the years has spawned an extensive popular mythology that unfortunately is more fiction than fact. This has led to a plethora of battery problems that has compromised many a video production. Throughout this handbook we have attempted to clarify most of these misunderstandings in a practical and topical manner. The following are those battery subjects that did not seem to fall logically into any one of the preceding chapters and are therefore addressed here.

Memory - NiCd "memory" is probably the most widely misunderstood of all battery anomalies. A major source of the confusion surrounding "memory" stems from the fact that there are two totally separate phenomena that have been called "memory". One of these is the "true" memory phenomenon which virtually never exists in video applications. The other is actually a ‘voltage drop’ problem that has become known as a "memory" problem based on its symptoms. It is this latter voltage drop pseudo "memory" that has been the long time subject of myth in the video industry.

The "true" memory was first observed by NASA while monitoring an orbiting satellite. Each day at precisely the same times, this satellite alternately passed from sunlight, where its NiCd batteries were solar charged, into darkness, where the batteries were called upon to power the craft. After many cycles of this precise duration partial discharge/charge routine, the scientists found that the battery would refuse to deliver power beyond that point to which it had previously been repetitively discharged. In other words, the battery "memorized" the point of partial discharges and then refused to give energy beyond that point if called upon to do so. This story has given rise to the myth that batteries should always be fully discharged before being charged in order to prevent the mysterious "memory" from robbing the remaining capacity.

This type of memory is extremely rare and almost never occurs in the video industry or any other industry for that matter. This rare memory phenomenon only results when the amount of the repetitive partial discharge is precisely identical each time, as occurred in the satellite. Relating this to video, a battery would, for example, have to be discharged for exactly 23 1/2 minutes at the exact same rate each day and then recharged each night for a week or more before this type of memory developed. Clearly nothing even close to this could ever happen. Yes, batteries are frequently only partially discharged and then recharged, but never in the precise manner necessary for true memory to be developed.

The "memory" so often mentioned in the video industry is not really a loss of capacity nor does it result from repeated partial discharges. It is in reality a voltage depression phenomenon and fig 5 is a graphic representation. At the so-called "memory" depression point, the voltage of the battery will drop about 1.2 volts. Figure 5 curve ‘A’ represents a "12 volt" nominal battery on a typical camcorder. Note that at the "memory" point the battery voltage drops below the camera cut-off voltage and thus the camera will stop. It appears that the battery has no more capacity. However this is not true. As can be seen, the battery can still deliver full capacity to the specified EODV at this lower voltage without a problem. The problem is the camcorder, which can not use this capacity. (Called "unavailable capacity". See also Battery Voltage section). This is why this type of "memory" became known as a "loss of capacity", because in this misapplication it does indeed result in a loss of capacity.

Curve ‘B’ represents the proper "14.4 volt" nominal battery for this camcorder. Note that the so-called "memory" point and associated voltage depression results in no loss of capacity. So this type of "memory" really is not a "loss of capacity". But where does this voltage depression come from and why is it called "memory", and why do so-called dememorizers or dischargers seem to alleviate this problem?

This so-called "memory" problem may be traced to a secondary alloy of Nickel Cadmium. Very simply, when a fully charged NiCd battery remains on a slow charger or many fast chargers, it is receiving a ‘trickle charge’ which is designed to prevent self discharge. Unfortunately over a period of time, this conventional trickle charge gradually transforms the crystal structure of the Nickel Cadmium into the secondary alloy. While normal NiCd has a nominal voltage of 1.2 volts per cell, this secondary or "rogue" alloy has a lower characteristic voltage of approximately 1.08 volts per cell.

Now consider a 10 cell VTR type video battery that has developed some of the rogue alloy. It is really two-batteries-in-one: part of the battery is a "12 volt" nominal NiCd and the rest is a "10.8 volt" nominal secondary alloy. When this "dual battery" is placed on a camcorder, the power will always be drawn from the higher voltage section (normal NiCd) first and everything appears normal. Once all the normal high voltage NiCd has been discharged, power will begin to be drawn from the lower voltage alloy section of the battery. Of course at this point the voltage will fall to the characteristic voltage of the rogue alloy which is insufficient to keep the camcorder operating.

There appears to be a mysterious loss of capacity and the battery is returned to the charger. The question now is : "What is being recharged"? The answer is: not the rogue alloy part of the battery. Because the camcorder could not discharge the rogue alloy part of the battery, it is still fully charged and intact. Only the normal section of the battery is being recharged. Therefore the next day the battery will perform exactly as it did on the previous. First, everything will appear normal and then all of a sudden the camcorder will mysteriously stop at the same point as it did before as if it had "memorized" the point at which the capacity was lost. This is where the misnomer "memory" comes from. Likewise, this is where the myth of the discharger was born giving rise to the totally false notion that batteries should be discharged fully before being charged.

Now that the mysterious phenomenon of "memory" is understood, the principle of the discharger becomes apparent. Because the camcorder can not discharge the rogue alloy in a "12 volt" nominal battery, it will remain there "forever". As a matter of fact, the situation actually gets worse as each subsequent trickle charging will create even more rogue alloy. In reality the rogue alloy is a perfectly legitimate battery. If the afflicted battery is connected to a device that can properly run down to the correct full discharge voltage of 10.0 volts, the battery will be totally discharged, rogue alloy and all. Now when it is recharged it will be 100% normal NiCd and the missing capacity magically returns. Thus the creation of the "discharge-before-charge" myth is as follows:

  1. A camera/camcorder is powered with the wrong battery that has a full discharge voltage below the cut-off voltage of the camcorder.
  2. When trickle charging begins to create the rogue alloy, the camcorder can not discharge it. Thus the rogue alloy remains intact and the battery appears to progressively lose capacity.
  3. By placing the battery on a device that can discharge the rogue alloy, the battery becomes 100% normal alloy when recharged and the "lost capacity" miraculously returns.

Take another look at fig 5 Curve ‘B’. Note that when the correct battery with the proper voltage range for the camcorder is used, there is no "memory" problem. In essence the camcorder performs the function of the "dememorizer" or discharger by fully discharging and erasing the rogue alloy every time the battery is used. It should be absolutely clear that the "memory" problem and the associated ‘discharging-before-charging myth’ are both the result of using a "12 volt" nominal battery in applications calling for a "13.2 volt" or "14.4 volt" nominal battery. Moreover, when using the proper voltage battery, discharging fully before charging is not only unnecessary, it is not recommended (See section below).

While using the proper voltage battery eliminates the undesirable symptoms described as "memory", the formation of the rogue alloy can be prevented in the first place by proper charger design . The transformation of normal alloy into the NiCd secondary alloy is caused by a steady trickle charge that is employed by most conventional fast chargers to impede or eliminate the effects of self discharge (See Self Discharge Section, page 44).

Obviously the elimination of this trickle charge will stop the formation of the rogue alloy but then the problem of self discharge returns. Anton/Bauer has solved this paradox with the patented Lifesaver circuit used in all Anton/Bauer professional chargers which maintains batteries at 100% charge with virtually no generation of secondary alloy or damaging heat.

Discharge-before-charge - The above section on "memory" fully explains the origin of the discharge-before-charge myth and why it is unnecessary when using the correct battery for the application. For those who are still using "12 volt" nominal batteries and are thus experiencing "memory " symptoms, the correct solution is not a discharger but rather replacing the offending batteries with the correct "13.2 volt" or "14.4 volt" nominal batteries as outlined in the Voltage section. However if a discharger is currently being used, it is imperative that precautions are observed to avoid permanent damage to the battery and possible explosion.

A light bulb or resistor must never be used as an unmonitored load to discharge a battery as this will take the battery down to 0 volts. Fully discharging a battery to 0 volts may damage the battery irreparably and could cause a serious explosion. A video battery consists of ten or more cells in series. As a battery approaches the end of discharge, one cell will always reach total depletion before the others. Once this first cell reaches 0 volts, the remaining cells may still have some energy and will continue to deliver power to the load. This current passes through the depleted cell and will actually begin to charge the depleted cell in the wrong direction. This drives the cell into reverse polarity which will damage and weaken the cell as well as create explosive hydrogen gas. Once such a cell has been weakened in this manner, it becomes more vulnerable to reverse polarity on the next deep discharge thus beginning a vicious cycle that ends with total destruction of the battery or a hazardous explosion.

When applied to rechargeable batteries the expressions "full discharge" or "deep discharge" never mean a discharge to 0 volts but rather a discharge to the specified EODV or End of Discharge Voltage (sometimes called the ‘full discharge voltage’). Therefore a discharger must have an automatic cut-off set at the EODV of the battery or slightly below. When the battery voltage reaches this value, the load must be instantly disconnected from the battery to avoid damage and injury.

For reference, the EODV voltages recommended for discharger cut-off are:

When using the correct "13.2 volt" or ‘14.4 volt’ nominal battery for an application, discharging before charging is not only unnecessary, it is strongly not recommended. Such discharging actually detracts from the overall cycle life of the battery.

For those who continue to ‘believe’ in the existence of "memory" problems despite the aforementioned scientific evidence to the contrary, the following suggestions are offered:

• Feel free to once a month "exercise" your batteries by using a discharger with the proper cut-off circuit. After the discharge is completed, allow the battery to ‘rest’ for at least 2 to 4 hours before being recharged. Such an occasional discharge should have no significant adverse effect on the battery.

• Place ‘name labels’ on your batteries such as "Monday", "Tuesday", etc, or just "A", "B", "C", etc. On Monday, begin with the "Monday" or "A" battery and try to use it until depletion (low voltage warning in the camera), and then switch to any other battery. On Tuesday, start with the "Tuesday" or "B" battery and again try to use it until depletion before changing to any other battery. Continue in this manner each successive day. This practice will guarantee that each one of your batteries will receive a full discharge at least once a week. For those who feel for some reason that periodic discharging is beneficial, this is the safe and practical way to do it without reducing the life or performance of the batteries. In essence, by using the proper voltage battery, the camera performs the function of the perfect discharger.

Self Discharge - A fully charged NiCd, after it is removed from the charger, will experience a phenomena known as self discharge. Due to an internal characteristic of the NiCd cell, it will very slowly and steadily lose its charge over a period of time. At room temperatures, a battery will be expected to typically lose 5% of its capacity in the first 24 hours and then 1% each day thereafter. Colder temperatures will significantly slow the process while elevated temperatures will accelerate self discharge. Under normal circumstances self discharge can be considered insignificant as almost 90% of full charge capacity should be available after a week away from the charger.

The problem is not normal self discharge, but rather abnormal or accelerated self discharge. For a multiplicity of reasons (see Battery Construction section), a NiCd cell can develop anomalies that will accelerate the self discharge rate by a factor of 2 to 25 times! Such a cell can lose 50% of its capacity in less than one week. The problem that this can cause are numerous and complex due to the fact that in most cases only a few cells in a battery usually develop this problem while the majority of the cells still exhibit normal rates of self discharge. This is a major cause of an "unbalanced" battery.

Unbalanced Batteries - An unbalanced battery is characterized by having cells that are at different states of charge. This results from the fact that of the ten or more cells that make up the battery, each is likely to self discharge at a slightly different rate and over a period of time each cell will exhibit a slightly different capacity or state of change. This minor problem becomes major when one or more cells exhibit an anomaly known as accelerated self discharge in which case the magnitude of the imbalance can become extreme and render the battery useless. The course of events usually proceeds as follows:

  1. A battery has two or three cells that have developed accelerated self discharge.
  2. Over a short period of time these three cells have lost 40% of their charge while the other eight cells in the battery have experienced a normal loss of only 10%.
  3. Now this battery is used to power a camcorder and instead of running 2 hours it fails after only an hour and ten minutes. This is due to the fact that when the three cells with only 60% charge reach depletion, the voltage will drop sufficiently to stop the camcorder. The battery thus appears totally discharged and 30% of its normal capacity seems to have mysteriously disappeared.
  4. In reality the battery is not totally discharged as eight cells still have 30% charge remaining. Now when this battery is recharged, most conventional chargers will terminate the charge cycle when the eight cells are fully charged. Since these eight cells need only an additional 70%, the three cells that were totally depleted will only be 70% charged when all the other cells reach 100% charge. Therefore right off the charger, the battery has three cells that are 30 % depleted. The original imbalance is thus carried forward and the previous 'loss of capacity' will occur again if the battery is used immediately. The battery seems to have memorized this loss of capacity which causes some to erroneously believe they are experiencing a "memory" problem.
  5. If the battery is not used immediately, step #2 above occurs again. This time while the eight cells lose the normal 10%, the 40% that the other three lose is subtracted from the reduced 70% with which they began. Now the imbalance has compounded with the normal cells at 90% charge and the other three at only 30% charge.
  6. This process can continue until the three cells can be totally discharged while the remaining eight are 100% charged. At this point the battery is usually described as "not taking a charge" , and is given up as dead. The reason it "doesn’t take a charge" is because a majority of the cells are fully charged and the reason it appears "dead" is because some of the cells remain fully discharged.

Cells with moderate accelerated self discharge are quite common and the above course of events occurs all too frequently, however this need not happen. Batteries with such cells can provide perfect service if the correct measures are taken. Of course proper battery construction can effectively eliminate the major cause of accelerated self discharge (see Battery Construction section), but when this condition does exist, accelerated self discharge can be negated with a maintenance charge and any imbalances can be corrected with a special equalizing charge.

Equalizing Charge - Due to both normal and accelerated self discharge, a battery can become severely unbalanced ( see above ). Conventional charging can not address this problem as the fast charge current must be terminated when the first cells reach full charge otherwise they would be damaged. Any other cells that have not reached full charge at this point will remain in the less-than-fully-charged condition. Thus any imbalance that existed before charging will still exist after charging. In addition, conventional charge termination technology can be totally mislead by a severely unbalanced battery and fail to cut-off high rate charge current resulting in battery destruction and the risk of fire.

This apparent paradox and hazard has been eliminated through InterActive charge technology. The internal All Cell Sensing network monitors the charge status of every cell. No matter how severe the imbalance, the internal sensors will always identify the first cell reaching 100% charge and terminate the fast charge thus eliminating all risk of hazard and damage to the cells. Immediately after the fast charge current is terminated, the charger microprocessor enters the equalizing mode. Based upon data from the battery Microcode circuit and sensors, and charge data collected during the preceding fast charge cycle, the microprocessor calculates the magnitude of any possible imbalance. The battery then receives an equalizing charge cycle that consists of a precise charge rate designed to bring up to 100% those cells requiring additional charge while causing no damage to those cells that have already reached full charge. When all cells have reached 100% charge and the battery is fully balanced and equalized, the equalizing charge rate is terminated and the maintenance mode commences. When using an Anton/Bauer InterActive charger , this equalizing mode is a standard feature of every charge cycle thus assuring complete safety and a 100% charged and balanced battery every time. While the equalizing mode can correct any existing imbalances, the maintenance mode is designed to prevent imbalances from ever developing.

Maintenance Charge - Assuming a charger has successfully identified the full charge status of the battery and terminated the fast charge current, it will classically do one of two things. It will either terminate all charge current and essentially disconnect from the battery, or provide a continuous ‘trickle charge’ for as long as the battery remains on the charger. Both of these alternatives create serious problems.

Terminating all charge current is identical to removing the battery and placing it on a storage shelf until it is needed. This allows the cells within the battery to experience both normal and accelerated self discharge, as the case may be, which creates the highly undesirable scenario as outlined in #1 through #6 under "Unbalanced Batteries" above. Even if accelerated self discharge is minimal, normal self discharge can still rob a significant amount of run-time depending on the interval before use and the storage temperature.

After fast charge termination, many conventional fast chargers place the battery on a continuous ‘trickle charge’ for as long as the battery remains on the charger. This trickle charge is designed to fully compensate and thus negate virtually all self discharge, both normal and accelerated, keeping the battery fully balanced and charged. This concept is valid in theory, however the trickle charge unfortunately has serious side effects that are actually more detrimental to the battery than self discharge. Trickle charging creates heat that will elevate the cell temperature of a typical video battery to over 45_ C (113_ F) which causes the organic components of the cell to deteriorate at a rate 5 to 10 times faster than normal. In other words, the constant trickle charge is causing the battery to age up to 10 times faster than normal, and a battery that would be expected to provide 2 or more years of service may fail after only 3 months of use. In addition, these elevated temperatures also reduce charge acceptance resulting is reduced capacity. Lastly, extended trickle charging is the major cause of the phenomenon known as "memory". The bottom line is: trickle charging is one of the worst things you can do to a NiCd battery from both an economic as well as a performance perspective. (See Charging Technical Section : TCO and Heat Aging )

This is the proverbial "damned if you do and damned if you don’t" situation. If the battery does not receive a trickle charge, it will self discharge and become imbalanced. On the other hand, if the battery is given a trickle charge, self discharge and imbalances are prevented but performance will be impaired and battery life can be reduced by 80% . Confronted with this paradox many years ago, Anton/Bauer engineers sought to develop a maintenance charge regime that could prevent self discharge and imbalances without the heat generation and accelerated aging associated with conventional trickle charging. The successful result of this effort is the patented Lifesaver maintenance mode that is provided by every Anton/Bauer professional charger. After the battery has been charged and fully balanced by the equalizing mode, the battery is placed in the Lifesaver mode for as long as the battery is on the charger. The microprocessor, with data from the battery, creates the precise Lifesaver pulse profile to keep the battery 100% charged and balanced with virtually no temperature elevation or accelerated aging. The battery should remain on the charger until it is needed. This can be days, weeks, or even months.


For an update on new technologies, please see the current Supplement to this handbook.

return to the Anton/Bauer home page


Headquarters and
Sales Office for the Americas

14 Progress Drive
Shelton, CT 06484
Telephone:
+1-203-929-1100
1-800-422-3473
Fax:
+1-203-929-9935
E-mail: sales: websales@antonbauer.com
customer service: support@antonbauer.com
feedback: feedback@antonbauer.com

Sales Office for Europe

Western Way
Bury St Edmunds
Suffolk IP33 3TB England
Telephone:
+44-128-475-6448
Fax:
+44-128-475-7929
E-mail: gbrown@antonbauer.com

 


Sales Office for Asia and the Pacific

100 Beach Road
#33-05 Shaw Towers
Singapore 189702
Telephone:
+65-297-5784
Fax:
+65-297-5778
E-mail: msoh@antonbauer.com

  Copyright © 1996, 1997, 1998, 1999. All rights reserved