Cell balancing

Cell balancing is the battery management process that keeps the cells in a battery pack at similar states of charge. In a battery made from cells connected in series, small differences in capacity, self-discharge, impedance or temperature can mean one cell reaches a voltage limit before the rest of the pack. The BMS or battery electronics may reduce charge to higher-voltage cells or manage the charging stage so the lower cells catch up, depending on the battery design. Imbalance can reduce usable capacity, make charging stop earlier than expected or appear in an app, service log or battery warning as cell-balance status. It should not be treated as a user adjustment or as proof that a failing cell can be fixed by charging for longer; manufacturer instructions and BMS control still decide how balancing is handled.