Reserve Capacity (RC) : RC is a general indicator of how long a new, fully charged battery can continue to operate essential accessories if the vehicle’s alternator fails. It identifies how many minutes the battery can deliver a constant current of 25 amps at 80°F without falling below the minimum voltage, 1.75 volts per cell, needed to keep your vehicle running.

Amp Hour and C20 Battery Capacity : Amp Hour or C20 is an indicator of how much energy is stored in a battery. It is the energy a battery can deliver continuously for 20 hours at 80°F without falling below 10.5 volts.