An Optimized Mesh-Structured Switched-Capacitor Equalizer for Lithium-Ion Battery Strings

The existing switched-capacitor (SC)-based equalizers either have slow equalizing speed and low efficiency or have bulky volume and low reliability. Therefore, an optimized mesh-structured SC equalizer (MSSCE) is introduced to achieve a tradeoff between the equalization performances and size as well as cost. The proposed MSSCE achieves all the shortest balancing paths from one cell to any cell in a battery string, significantly improving the equalization speed and efficiency. The switching impedance of the proposed MSSCE is derived and analyzed, which provides design guidance for the switching frequency and the capacitance. A four-cell prototype was set up. Experimental results confirm that the proposed MSSCE enhances the balancing speed with a high efficiency of 91.7%, moreover which is robust to the imbalanced cell voltages.