Effects of Temperature Differences Among Cells on the Discharging Characteristics of Lithium-Ion Battery Packs with Series/Parallel Configurations during Constant Power Discharge

This work aims to make a comparative analysis of the unbalanced discharging phenomenon for battery packs with series/parallel configurations due to the temperature differences among the cells. A theoretically-based model is developed for the battery pack and constant power discharging processes are simulated by the model. At a constant temperature difference, lowering the operating temperature increases the divergence among the cell terminal voltages for the series pack and the cell discharging currents for the parallel pack. Increasing the temperature differences decreases the dischargeable energy of the series battery pack, whereas it has little effect on that of the parallel configuration. Given the same temperature difference, the cell energy differences within the parallel battery pack are 5–10 times higher than those within the series configuration, which shows that the temperature can be maintained much more uniformly for a parallel battery pack than for series configuration.