Investigation of series-parallel connections of multi-module batteries for electrified vehicles

Large-format Lithium-ion battery packs consist of the series and parallel connection of elemental cells, usually assembled into modules. The required voltage and capacity of the battery pack can be reached by various configurations of the elemental cells or modules. It is thus worth investigating if different configurations lead to different performance of the battery pack in presence of a mismatch in the cell characteristics. A simulation tool is developed in this work and applied to a battery pack consisting of standard 12 V modules connected with various serial/parallel topologies. The results show that battery configurations with modules directly connected in parallel and then assembled in series are more robust against variation of the cell capacity through the battery. Moreover, given the cells and the battery configuration, we show that changing the position of the cells has a significant impact on the usable capacity of the battery.