Comparison of Active and Passive Balancing by a Long Term Test Including a Post-Mortem Analysis of all Single Battery Cells

Due to the fact, that there are basically no practical test comparisons between active and passive lithium-ion battery balancing systems, a long term test is carried out. Therefore two batteries with an active and a passive balancing system are cycled. After about 2600 cycles test is stopped to start with further investigations. Capacity decrease and the increase of internal resistance of the two used battery packs are presented. To investigate the influence of load cycles in combination with different battery management systems (BMS) a detailed single cell investigation is executed. Finally, active balancing increases the usable capacity by a maximum of 2% compared to passive balancing and reduces the cell to cell deviation of capacity and internal resistance. Furthermore it is shown that the additional stress due to frequent energy redistribution in active balancing systems has no negative ageing effects to the cells compared to passive balancing.