Battery Charge Time Calculator | BatteryPackCalc

How to Use the Charge Time Calculator

Enter your pack capacity in amp-hours and the constant-current rating of your charger in amps. Dividing capacity by current gives the ideal bulk-phase time: the default 14 Ah pack on a 5 A charger needs 14 ÷ 5 = 2.8 hours of constant-current charging — about a 0.36C charge rate, since 5 A flowing into 14 Ah is 5 ÷ 14 of the capacity per hour. The results panel shows three figures: the CC phase time plus minimum and maximum total-time estimates. The charge current must be greater than zero — the calculator flags zero or negative input as invalid because the division is undefined there.

Real lithium chargers follow a CC-CV profile: they push constant current until the pack reaches its maximum voltage, then hold that voltage steady while the current tapers toward zero. That taper phase adds time the simple capacity-over-current division cannot see, which is why the tool also reports a realistic total range of 1.2× to 1.5× the CC figure — between 3.36 and 4.2 hours for the 14 Ah / 5 A example above.

Where a given charge lands inside that range depends on how hard the charger pushes relative to pack capacity (a higher current finishes the bulk phase sooner but spends proportionally longer in the taper), on the state of charge you start from, and on any cell balancing the BMS performs near the top of the charge. The estimate assumes a full charge from the low-voltage cutoff; when topping up a partially charged pack, enter only the capacity that still needs to be replaced.