Reserve Capacity

The reserve capacity rating 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 a fully charged battery, being discharged at a constant rate of 25 amperes and 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, or the condition of the battery will affect how long the battery will actually last when the vehicle is being driven without generator output.