Battery pack capacity formula

Use this formula to compute a lithium-ion battery pack capacity:

% = 1.25 * v / s - 3.875

Where % is the remaining capacity as a fraction of 1 (multiply by 100 to get a percentage), v is the pack voltage and s is the number of cells in series.

Example:

Your pack has 3 cells in series and the measured voltage is 11.5 volts. in the previous equation we replace v with 11.5, s with 3 which gives:

% = 1.25 * 11.5 / 3 - 3.875

The result is 0.91666...67 which can be considered as 91.67% of remaining capacity for instance.