Battery Reserve Capacity to Amp-Hours
The amp-hours behind a battery's reserve-capacity minutes.
Example
You enter
- Reserve capacity (minutes) 120
You get
- Amp-hours (at the 25 A reserve rate) 50.0 Ah
Checked against published worked examples from: RELiON Battery.
Details, formula, and sources
ScopeBCI / SAE J537 reserve capacity is the minutes a fully charged 12 V battery at 80 F sustains a 25 A draw to a 10.5 V cutoff, so amp-hours at that rate = 25 x RC/60 -- an RC of 120 minutes is 50 Ah. This RC-rate capacity is lower than the 20-hour-rate amp-hours on a deep-cycle label (Peukert's effect), so the two are not interchangeable; cold reduces it further. A comparison aid; the battery rating and a load test govern.
Formula or tableamp_hours = 25 x reserve_capacity_minutes / 60.
Source and editionBCI / SAE J537 reserve capacity, by name; the battery's published rating and a load test govern.
Free accessThe 25 A / 10.5 V / 80 F reserve-capacity definition is a published BCI / SAE J537 rating basis; the reserve minutes come from the battery spec.
What governsEstimate. AHJ and licensed professional govern.
API field namesrc_minutes, amp_hours
- Reserve rate 25 A draw to a 10.5 V cutoff at 80 F on a 12 V batteryBCI / SAE J537