A novel measurement technique for parallel-connected lithium-ion cells with controllable interconnection resistance

Due to the broad use of parallel-connected cells across multiple applications, it is essential to understand the current distribution between them. Variations in resistance, temperature and capacity can lead to an inhomogeneous current distribution and have a deleterious influence on ageing and safety. It is therefore crucial to investigate the current distribution within such systems. However, the task of designing a low-complexity test apparatus, that does not itself affect the current measurement, remains incomplete. This work investigates a novel measurement method to connect cells in parallel with controllable interconnection resistances. Instead of a physical connection, the presented method couples the cell using Kirchhoff’s laws via a commercial battery cycler. This connection allows investigation of parallel-connected cells, without influencing factors such as contact resistances or an additional measurement environment. Further, two studies demonstrate the influence of the additional interconnection resistance caused by the parallel connection of two cells. The results of measurements including a differential voltage analysis show, that the cell current divides according the ratio of the combined cell and interconnection resistance, whilst the open-circuit-voltage influences the shape of the current distribution.