A battery has two ratings:
| • | The reserve capacity |
| • | The cold cranking amperage. |
Reserve Capacity
The reserve capacity is an estimate of how long the vehicle can be driven with no generator output, the headlamps turned on and a minimum electrical load (most of the accessories turned off). It is the maximum amount of time (in minutes) it will take for a fully charged battery, being discharged at a constant rate of 25 amperes and a constant temperature of 27° C (80° F), to reach a terminal voltage of 10.5 volts. Other temperature or current draws, the state of charge, the condition of the battery, etc., will affect how long the battery will actually last when the vehicle is being driven without generator output.
Cold Cranking Amperage
Cold cranking amperage is an indication of the ability of the battery to crank the engine at cold temperatures. This rating is the minimum amperage the battery must maintain for 30 seconds at -18° C (0° F), while maintaining at least 7.2 volts. The actual performance of a battery will vary with actual temperature.
