Comparative Analysis and Evaluation of the Different Active Cell Balancing Topologies in Lithium Ions Batteries

Series connected batteries must have their cells balanced whenever charging and discharging to extend battery lifespans, assure safe operation, and increase battery pack useful capacity. It also causes charge imbalance issues, which will result in battery cell damage and battery life loss. Several charge/discharge equalization circuits have been suggested however, presently there has been no work regarding the comparison and evaluation of the speed and efficiencies in both modes. In this study, cell balancing on dc-to-dc buck-boost converter and interleaved flyback converter topologies operating in discontinuous current mode are analyzed, designed, and implemented. A simulation model of the converter-based topologies of an active cell balancing system is proposed and designed along with a power loss analysis, efficiencies, and control technique. With the purpose of establishing an energy storage application, the system's cells are grouped into 8 series cells for SOC balancing and 2 series cells for voltage balancing circuit design. Power loss analysis is performed to analyze the efficiency of these two converter topologies to identify which system performs better. In SOC balancing in charging mode, the buck-boost and interleaved flyback converters' power efficiencies are 85.596% and 65.1521% respectively and during voltage balancing 93.9078% and 73.1506% respectively.