Battery Information

There are well-made and reliable batteries from many suppliers that will last many years if well treated. Anton Bauer has written much about battery maintenance and NRG has a very good pamphlet on batteries. (800-753-0357) Here is some information for unusual needs.

A battery's amp hours (AH) rating is theoretically the amps a battery will provide for an hour, but usually at a 1/10 of that rating for 10 hours. Film and pro video cameras will discharge a 10 AH battery in less than an hour, even if it only requires one amp current. The discharge curve of a lead acid battery voltage is pretty much a straight line down. Ni Cd batteries maintain their voltage longer and drop near the end of use which is good for their maintenance. Although lead acid batteries have more energy per weight, much of that energy is not usable because a 12-volt battery voltage drops below camera cutoff voltage, usually 11.5 volts. Video cameras shut off automatically at about 11.5 volts. 14-volt batteries will allow much deeper discharge, but it is harder on the battery and will shorten life.

Lead acid batteries and chargers are fairly cheap and are readily available some parts of the world. The larger the battery, the longer the cameras will operate. One 10 amp/hour (AH) battery will last longer than two, 5 AH batteries as the larger battery will hold its voltage better.

12 volt systems. Off the self, sealed batteries come in roughly 2.5, 5, 7, and 10 AH sizes. "Smart" chargers (ones that charge fast and then trickle charge to avoiding damage) are available at electronic suppliers. 16-hour chargers are cheap, but take longer to recharge, but won't hurt a battery if left on after the battery is fully charged.

12 volt wet batteries and chargers for cars and motorcycles are also available in even more places. A car battery will run a camera or 12-volt video monitor all day. Use large cables (#12 or #14 gauge) to avoid resistance loss for cables over 6 feet. Boxes for car batteries are available in marine and camping vehicle stores. DO NOT AIR SHIP HIGH AMPERAGE BATTERIES. IT IS DANGEROUS TO THE PLANE. If you plan to get batteries on location, take all the cables, boxes and connectors that you might need. You might even rent a battery.

14-volt lead acid combinations of one 6 and two 4 volt batteries will power a video camera much longer before the camera shuts of at 11.5 volts. I know of no smart chargers for this voltage available at electronics stores. There are 8 and 6-volt smart chargers available from Bescor and they may have a 14-volt smart charger.

6-volt batteries and chargers are available for 6-volt cameras.

8-volt batteries can be made with two 4-volt batteries. So far as I know the only smart chargers are from Bescor. These will run VX700, VX 1000 or other 7.5 volt camera a long time. A battery and charger is about the cost of one internal battery. (The Sony TRV 900 runs a long time on one full size internal factory battery.)

When buying lead acid batteries, check the manufacture or shelf life date. Don't buy old lead acid batteries. Most Ni Cds are OK with age. I don't know about nickel hydride.

Chargers. You can charge any lessor voltage battery from a car battery with a light globe or power resistor. Let's say you want to charge an 8-volt battery at 1000 mils or 1 amp. If you need to drop 4 volts you need a resistance of R=E / I = 4Volts / 1 Amp = 4 Ohms. To find the wattage of the resistor you need P = I x E = 1 x 4 = 4 watts, which is a pretty large resistor. You can also use a light globe to drop the voltage and also be sure that the battery is charging. A 12 volt 25 watt globe should draw 25 / 12 = 2 amps. The resistance of the globe at 12 volts would be R = E / I = 12 / 2 = 6 ohms. 4 volts dropped over 6 ohms would be I = E / R = 4 / 6 = .66 amps which is a good charge for 10 Amp Hour battery. BUT light globes have a lower resistance at lower than operating voltages and you might get a 1 amp charge rate, which is just fine.

Wall transformer chargers are available for most voltages. Resistors can reduce current. Transformers and diodes can make higher current chargers. Check charge voltages and currents.

Ni Cds trickle charge at a 1/10 of their AH rating for 14 hours. That's 140% of their amount of discharge. Most cells will not be hurt by this charge, but wet Ni Cds will vent water vapor that has to be replaced with distilled water right after a full charge.

Connectors. Matching the plugs on consumer camcorders is difficult. Some power cables can be cut and reconnected with plugs. Some Sony cables use 3 wires and all three are needed to use the factory power supply. A stereo 1/4" plug or 4 wire Jones plug are cheap and easy to wire. Put the male plug on the camera side.

For 2 wire systems I like the Jones plugs. If you have 6 or 8-volt systems and also 12-volt systems you might use 4 pin Jones for the 12-volt systems to avoid wrong voltage problems. Radio Shack stocks the 2 pin Jones.

Meters. To build, test and maintain batteries you must have a VOM with amperage scales and know how to use it. They are useful even with commercial batteries and for trouble shooting cables, batteries, fuses, lights, and outlets.

Battery terminal voltages vary for many reasons: 1. The charge remaining. 2. If on or off charge. 3. Rate of charge. 4. Time after charge. 5. Time since discharge and amount of discharge. 6. If in use. A battery can have an almost open circuit and can read full voltage with a meter, but not run camera. A useful device is making an adapter between the battery and camera that will check both the battery voltage and current with the camera running. I feel this it the best test. The factors above still apply. You can also connect a 12 volt 25 watt car lamp to a camera plug (XLR-3 male) and test cables and batteries without a camera.

You can make your own Ni Cd "D" size 4 AH batteries or replace cells in a bad back. You can replace one or two shorted or open cells in a pack, but if more are bad, replace them all. A shorted cell will read no voltage and the charger will keep charging and the batteries will get hot and often self-destruct. An open cell will show a high voltage under charge or discharge. Make sure to get solder tab cells and not 1.5 AH "D" cells that are the same price as "C" cells. Include fuses in your pack.

When a pack will run a camera for only a short time, but recharges too fast, it has partly open cells. A larger voltage appears across the cell and tells the charger the total voltage is up to full and the charger stops charging.

You can parallel wire lead acid batteries for more AH rating, but not Ni Cds; they will discharge each other.

When one cell of a lead acid pack goes bad, usually most of the rest are about to go and should be replaced. A couple of years is all you can expect under normal use.

DON'T LEAVE LEAD ACID BATTERIES DISCHARGED. If you won't be using them for some time you can plug a trickle charger into one timer set for one hour into another set for one hour and get a 1 hour charge every 24 days. Set the first one-hour and the second for 30 minutes and get one hour charge every 48 days. Most camera Ni Cds should not be trickle charged. Some Ni Cds are made to trickle charge, such as toothbrushes and raisers.

Other Ni Cd batteries. The batteries and chargers for remote control cars are cheap and work fine for 6 and 7.2-volt cameras and DAT recorders. They will run a camera for quite some time. These packs have thermocouple cut-offs that open when the battery gets hot from charging or heavy discharge.

Portable power tool batteries come in 7.2, 9, 12, 14, and 18 volts. They are cheaper than camera batteries. Many also have thermocouples. The flashlights for these batteries can be converted to pocket or belt packs with a cable. Watch polarity!

Ni Cd batteries loose about 1% of their charge per day. Nickel Hydride even faster. Lead acid batteries hold their charge very well

Most Ni Cd 9-volt transistor batteries are 7.2 volts and won't work for radio microphone systems. There are a few 8,4 volt ones that will work.

Dry batteries are not very useful for cameras because they loose their voltage quickly. A camera will stop long before the battery is even partly discharged. .9 volts is the lowest design voltage for a 1.5 dry battery with a 1.6 initial voltage. Even "D" size batteries won't last long. Maybe for the very low current Sony TRV 900.

Used and surplus wet Ni Cd batteries can give very large currents and can last many years with care. Unused ones can be many years old and if they will take a charge will probably work fine. C and H Sales in Pasadena California have some 28 volt 8 AH packs for $100 that will run a 30-volt Photosonics, XR-35 or Fries Mitchell motor. Be careful of polarity because some of the same plugs have different polarity. These batteries can be tapped for lower voltages.

A convenient pack for hand held Arri IIIs is are 10 "C" Ni Cd cells in a 5 and 5 cell pack with cable attached that will fit in the pocket or belt clip. A charged pack will shoot 2 or 3 mags. The same thing could be done with 12-volt portable tool packs, which would have chargers available. Try the flashlights for battery holders.

Photosonics 16 mm IVN and 35 mm 4ML are sensitive to voltage over 28 volts. A Ni Cd battery just off charge can have enough voltage to damage the electronics of the camera.

110-volt packs can be made of 10, 12-volt car batteries or a set of Ni Cds. The Ni Cds will hold voltage and color temperature better, but are less efficient that lead acid per pound. Chargers can be as simple as a rectifier and voltage dropping light in series from 110 volt AC. USE A ISOLATION TRANSFORMER TO PREVENT DEADLY SHOCKS. Rectified 110 AC is about 140 volts and can be reduced with lights. A 9 light FAY will allow different charge rates for large car battery systems. The lights are running at a very low voltage and won't effect their longevity.

A handy unit is the 6 globe 12-volt light made by American Market. Each globe is switched and both halves will pan separately for more control. This can light backgrounds where cabling regular lights is not possible.

Battery care. Don't deep cycle lead acid batteries. Using Ni Cds until video cameras quit is proper deep cycling and other cycling should not be needed.

Recharge lead acid batteries as soon as possible.

DO NOT RUN BATTERIES LOW WITH LIGHTS. It is bad for all kinds of batteries. When a light gets a bit dim, turn it off.

Most Ni Cds can be left discharged. I don't know about Nickel Hydride.

© Copyright 1999-2004 Ron Dexter. All Rights Reserved.