A battery’s RC represents the length of time a battery can maintain a vehicle’s electrical needs in the event of a charging system failure (alternator failure). BCI (Battery Council Industry) defines RC for a 12V SLI (Starting, lighting, ignition) battery as the amount of time (in minutes) that a battery can deliver 25 amps at 27 degrees celcius or 80 degrees farenheit while maintaining terminal voltage of at least 10.5 volts.