Grading cells for a battery pack

摘要

A battery pack having a first secondary cell and a second secondary cell, preferably of a non-aqueous chemistry, is described. Each secondary cell has a discharge capacity and an internal resistance to a direct charge current. To diminish and alleviate problems associated with extended cycling of battery packs, the internal resistance to the direct charge current and the discharge capacity of each secondary cell is substantially matched. Thereby, the battery packs have longer running voltages and increased energy density.