Dynamics of current distribution within battery cells connected in parallel

摘要

The current distribution of lithium-ion batteries connected in parallel is asymmetric. This influences the performance of battery modules and packs. The ratio of asymmetry depends on the differences between the battery cell parameters and the dynamics of the load profile. This detailed simulative study varies both of these factors and shows the influences on current and charge throughput. The cell parameters are based on real-world effects caused by production and operation. Differences in impedance generate higher current deltas and charge throughput differences compared to capacity differences due to manufacturing fluctuations.The simulation model in this study uses mainly a linear open circuit voltage (OCV) so that the results are not influenced by nonlinearities. A subsequent analysis uses a defined nonlinearity in the OCV to show its impact on the current distribution. The results show that the temporary difference in current caused by the nonlinearity of the OCV exceeds the effect of the chosen parameter differences.Finally, a comparison of the different cell dimensioning shows that high-energy (HE) cells display an inert behaviour with respect to current asymmetry. High-power (HP) cells are more dynamic. This means that impedance differences have a greater influence on HE and capacity differences on HP cells.