Battery Atlas

Conversions

Wh to Ah Converter

Convert stored energy (Wh) into amp-hours at a given voltage.

V

Formula

Ah = Wh ÷ V

Worked example

1,200 Wh ÷ 12 V = 100 Ah. The same 1,200 Wh at 24 V is only 50 Ah.

Limitations and warnings

  • Always compare batteries of different voltages in Wh, not Ah.

Four values that are often confused

Nominal capacity (Ah)
Charge a battery delivers under rated conditions, usually over 20 hours (C20) at 25 °C.
Usable capacity
The part of the nominal capacity you can use without damaging the battery — about 50% for lead-acid, 80–90% for LiFePO4.
Cranking current (CCA)
Current deliverable for a short time in the cold to start an engine. It measures power, not stored charge, and cannot be converted to Ah.
Stored energy (Wh)
Ah × voltage. The right unit to compare batteries of different voltages.