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Capacity & Reserve Capacity

Battery capacity describes how much energy a battery stores and delivers over time. It is measured in amp-hours (Ah), while reserve capacity (RC) is measured in minutes. Together with CCA, these define a battery's full electrical profile.

Capacity (Ah) — the C20 Rate

Capacity is typically quoted at the C20 rate — the current a battery can deliver over 20 hours before reaching a defined end voltage.

  • The C20 rate is the standard reference for deep-cycle and automotive capacity comparison.
  • A higher Ah means more stored energy, supporting vehicles with high electrical accessory loads.

Reserve Capacity (RC)

Reserve capacity is the number of minutes a battery can deliver a defined discharge current (typically 25A) at 25°C before dropping below the cut-off voltage.

  • RC measures how long the vehicle can run on battery power alone if the alternator fails.
  • Higher RC is valuable for vehicles with heavy accessory loads or start-stop systems.

Capacity vs CCA

  • Ah measures stored energy over time — how long the battery can supply current.
  • CCA measures the peak current burst for starting.
  • A vehicle with high electrical accessories needs Ah; a cold-weather diesel needs CCA.
  • Most OEM specifications list both, and both must be confirmed.

Measurement Standards

Capacity and RC are measured to the relevant standard (JIS, DIN, BCI, SAE, EN). Confirm the test basis and rate (C20 vs C5) when comparing capacity values, as different rates yield different numbers.

See CCA Testing for how these metrics differ and why both matter.

Source & Purchase

For high-volume OEM and private-label sourcing with full analytical documentation, browse the complete battery model catalog on the main website to request specifications and bulk pricing.