Zeta-SEPIC Converter-based Integrated Battery Equalization Method for Lithium-ion Battery Strings

Battery equalization management is a key technology for ensuring the safe and efficient operation of equipment containing battery energy storage systems, such as electric vehicles, drones, and renewable energy generation. In this paper, an integrated equalizer for lithium-ion battery strings is proposed. This equalizer enables the multiplexing of switches in a traditional centralized equalization system and integrates the bidirectional switch used for battery selection in the switch array and power switch used for energy conversion in the bidirectional Zeta-SEPIC converter, thereby obtaining high-power-density characteristics. This equalizer has a buffer-based structure that guarantees efficiency and expandability when equalizing series-connected battery strings. Compared with conventional methods, the proposed scheme exhibits a controllable equalization current, small number of components, low cost, and high efficiency, and has broad application prospects and practical value. The operating principles, theoretical derivations, and design considerations are thoroughly analyzed. An experimental test platform is built, and experiments are conducted using a four-cell lithium-ion battery string. The experimental and comparison results verified the superiority and feasibility of the Zeta-SEPIC converter-based battery equalizer.