PANAVISION cameras may be supplied either with Nickel Cadmium or Sealed Lead Acid batteries. Both types have a good power to weight ratio, are maintenance free and hold their charge well under normal temperature conditions. From the users’ point of view the principal differences are in the voltage of the individual cells, the type of charger that needs to be used and the effect of habitual overcharging.
PANAVISION supply two types of Nicad Batteries, the normal type being made up of cylindrical cells and the higher capacity type which uses rectangular nickel-cadmium alkaline cells.
Cylindrical cells, being smaller, are most usually used for battery belts and for onboard batteries.
All Nicad batteries hold their charge best when kept cool and deliver best when warm. They self-discharge quite rapidly at temperatures above 95°F (35°C) but below 32° (0°C) can hold their charge for years.
They give of their maximum at 85-95°F (30-35°C). At 32°F (0°C) they give only half capacity and at -40° may not operate at all.
The nominal voltage of Nicad cells is 1.2v. When charging is just completed, for a short period, the voltage may be as high as 1.5v per cell. For this reason they should be rested for at least two hours after charging to allow the voltage to stabilize.
On discharge Nicad cells maintain a very constant 1.2v per cell until they come to the end of their charge when the voltage drops rapidly. They should not be discharged below 1v per cell.
Nicad batteries must only be recharged using a constant current type charger designed especially for recharging Nicad type cells.
If Nicad batteries are frequently recharged before they have been fully discharged they will suffer from what is known as ‘memory effect’ and will cease to hold their full capacity. This state can be corrected by discharging the batteries to 1v per cell several times between full charging. It is very bad practice to recharge Nicad batteries when they are already fully charged.
PANAVISION Inc. inTarzana has a special nicad battery testing rig which plots the current flow of batteries as they are fully discharged under controlled conditions. On this device any malfunction, even of a single cell, is plotted on a graph so that any faulty cell may be identified and replaced.
1. Cylindrical and rectangular Nicad battery cells, 2. Battery belt made up of Nicad cells, 3. Nicad battery test rig, 4. Nicad battery graphs.