Abstract: Battery un-uniformity is a critical problem for the battery pack in the automotive powertrain application. Life model and thermal model were combined with the equivalent circuit model (ECM) to analyze the divergence caused by the un-uniformity decay rate between the cells in the battery pack. The results show different trends of decay for different working conditions. The  temperature which has a close relationship with the polarization process has a significant impact on the decay rate. Both capacity variation and polarization variation should be considered in the cell selection during the battery pack assembly. The method can be applied to the cell selection during the battery pack design and assembly phases.

Key words:  battery uniformity, equivalent circuit model (ECM), lifespan decay, automotive power source