Battery Rating And Current Test

A battery has 2 ratings: a reserve capacity rating at 27° C (80° F) which is an estimate of the time a fully charged battery will operate the vehicle with no generator operation; and a cold rating at -18° C (0° F) which indicates the cranking load capacity. Refer to Battery Load Test.

Reserve Capacity
The reserve capacity is the maximum length of length of time (expressed in minutes) required for a fully charged battery to discharge to a terminal voltage of 10.5 volts direct current (VDC). All batteries are rated at a constant temperature of 27°C (80°F) and a constant drain of 25 amperes. This current drain is about the same as operating a vehicle with the headlamps on with other minimal electrical loading (radio etc.) and no generator output.

Cold Cranking Amperage
The cold cranking amperage rating is the minimum amperage which must be maintained by the battery for 30 seconds while meeting a minimum voltage requirement of 7.2 VDC. All batteries are tested at -18°C (0°F)

Electrolyte Freezing
The freezing point of the electrolyte depends on its specific gravity. Since specific gravity depends on the state of charge, the battery should be protected against freezing by keeping it in a charged condition. If the electrolyte is frozen, the battery will need to be replaced.