Influences of Cell to Cell Variances and the Battery Design on thermal and electrical imbalances among parallel Lithium-Ion Cells

Batteries consist of a high number of single cells in order to fulfill the power and energy requirements of large-scale applications. Electrical and thermal imbalances among the cells of the battery arise during operation caused by cell to cell variations and battery design tolerances. This heterogeneous stress can result in a accelerated degradation of individual cells, which reduces the lifetime of the whole battery. To prevent this effect insights of the impacts on cell imbalances, regarding the State of Charge (SoC), temperature and current, are essential to improve the battery operation strategy. In this paper the influence of cell to cell variances and the thermal design of the battery on the mentioned cell imbalances are experimentally investigated for two parallel-connected cells. Experiments with three cell groups, having different cell parameter variances, are conducted. In order to investigate the thermal influence of the cell packaging and battery design, different cooling scenarios are considerd, like an insulation and a heterogeneous cooling of the cells.