Battery cells are commonly connected in parallel to increase the capacity of battery packs. However, non-uniform boundary conditions across parallel-connected cells may result in an uneven current distribution, thereby reducing system performance. Directly monitoring the current distribution during operation is challenging for the Battery Management System due to the high costs and complexity involved in installing a current sensor in each parallel path, making prior estimation essential.

The impact of the number of cells on current inhomogeneity in parallel configurations remains largely unexplored in existing literature, as such measurements are resource-intensive and prone to inaccuracies. In this study, we present a measurement methodology that enables flexible adjustment of the number of cells in parallel while introducing a controlled deviation in the path resistance of one cell. By systematically varying both deviation in path resistance and the number of cells, we analyse their effects on current inhomogeneity across three cell technologies.

Our findings show that current inhomogeneity scales linearly with the deviation in path resistance and asymptotically with the number of cells, irrespective of cell technology and whether the deviating cell has an increased or decreased path resistance compared to the others. Notably, cells with reduced path resistance can also pose challenges. The identified sensitivities allow to scale the current inhomogeneity measured within a specific parallel configuration to any desired parallel configuration. Our measurement methodology significantly reduces the effort required for investigating the impact of inhomogeneous boundary conditions within parallel configurations, providing valuable insights for the design and optimization of battery systems.