A novel method of battery management was developed for large battery packs such as those used in Plug In Hybrid and Battery Electric Vehicles where the existing battery management system and DC/DC converter are replaced by an integrated, modular battery management-DC/DC converter system. The system contains of a number of small DC-DC converters in parallel with one or more cells. Differing loads through the DC-DC converters are used to differentially balance the various cells. This method has the increases battery life by reducing stress on the weaker cells in the battery. Simulations show life extensions of 30-50%, depending on the type of vehicle and the location. Different balancing strategies may be employed depending on the needs of the battery and vehicle. This method allows more range in older vehicles, as the range is no longer limited by the capacity of the weakest cell. The proposed system will not only allow a longer battery life, but the total system cost may be reduced. Implementation of prototype hardware in a Ford PHEV battery will be discussed.