A Low-Cost and High-Efficiency Active Cell-Balancing Circuit for the Reuse of EV Batteries

Abstract

In this paper, a high-efficiency and low-cost active cell-to-cell balancing circuit for the reuse of electric vehicle (EV) batteries is proposed. In the proposed method, a battery string is divided into two legs to transfer the charge from each cell in one leg to that in the other and a bidirectional CLLC resonant converter is used to transfer energy between the selected cells. Thanks to the proposed structure, the number of bidirectional switches and gate drivers can be reduced by half compared to the conventional direct cell-to-cell topologies, thereby achieving lower cost for the system. The CLLC converter is used to transfer the charge, and it is designed to work at resonant frequencies to achieve zero-voltage zero-current switching (ZVZCS) for all the switches and diodes. Consequently, the system’s efficiency can be enhanced, and hence, the fuel economy of the system can also be improved significantly. To verify the performance of the proposed active cell-balancing system, a prototype is implemented for balancing the three EV battery modules that contain twelve lithium-ion batteries from xEV. The maximum efficiency achieved for the charge transfer is 89.4%, and the balancing efficiency is 96.3%.

A Method for Assessing the Technical Condition of Traction Batteries Using the Metalog Family of Probability Distributions

“…Moreover, it is able to manage the balancing process of the entire package [44]. Battery voltage balancing involves balancing the charge level of individual cells connected in series or parallel, depending on the design [45]. Each battery has its own individual characteristics and may have slight differences in charge level and internal resistance.…”