Determine the correct charging current for a battery from its capacity and C-rate.
The C-rate expresses current relative to capacity, so 0.2C on a 200 Ah battery is 40 A. Charge time is slightly longer than the reciprocal of the C-rate because the final absorption stage tapers the current. Exceeding the manufacturer C-rate is the fastest way to destroy a battery, and it also raises charger cost disproportionately.
Battery Charging Current
Charging current = capacity × C-rate
Charging current = capacity × C-rate The C-rate expresses current relative to capacity, so 0.2C on a 200 Ah battery is 40 A. Charge time is slightly longer than the reciprocal of the C-rate because the final absorption stage tapers the current.
Exceeding the manufacturer C-rate is the fastest way to destroy a battery, and it also raises charger cost disproportionately.
This calculator takes 4 inputs: Battery capacity, Charge C-rate, Battery voltage, Charger efficiency. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.