Battery Atlas

Conversions

Ah to Wh Converter

Convert battery charge (Ah) into stored energy (Wh) using the nominal voltage.

V

Lead-acid 12 V battery: 12 V nominal. LiFePO4 4-cell: 12.8 V.

Formula

Wh = Ah × V

Worked example

100 Ah × 12.8 V = 1,280 Wh (1.28 kWh).

Limitations and warnings

  • Result is nominal stored energy, not usable energy. Multiply by the usable depth of discharge for real availability.

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.