RC (Reserve Capacity)
Minutes the battery delivers 25 A while staying above 10.5 V. Measures autonomy with engine off or alternator failed.
RC (Reserve Capacity) indicates how many minutes the battery can deliver a continuous 25 A without the voltage dropping below 10.5 V, starting from 100% charge at 27°C. It is the key figure for knowing how long consumers will last with the engine off (radio, navigation, hazard lights) or if the alternator fails on the road. A typical mid-range car battery has 90-150 minutes of RC; premium batteries (deep cycle, large AGM) reach 180-220. Approximate conversion: RC × 0.6 ≈ Ah (not exact). The EN standard does not require it as a primary specification (it prioritises CCA and Ah) but the American SAE/BCI highlight it.
For users of motorhomes, boats or vehicles with many electrical accessories RC is more relevant than CCA.