Battery Capacity Calculator

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Volts per cell V

mAh per cell

Cells in series

Strings in parallel

Usable share of the printed capacity % — see below

Load current mA, for the C-rate

Enter a cell voltage and capacity, then press Calculate.

From the book — Chapter 2. Series adds volts, parallel adds hours. Wh = V × Ah. C-rate = load current ÷ capacity — under 1C is gentle, well over it is not.

Matches Chapter 2, including the usable-capacity derate. Everything stays in your browser — no sign-up, nothing stored.