A rechargeable multiple cell battery pack has an application associated therewith that draws power from the battery pack. While the battery pack is in operation, voltage, current, state-of-charge (SOC), and impedance data are collected on a per-cell basis and an algorithm is performed to determine a state-of-charge for each individual cell of the battery pack consistent with predetermined criteria. The individual cells are charged to the respective, determined state-of-charge (SOC) levels.