A String-to-Cell Battery Equalizer Based on Fixed-Frequency LCC Resonant Converter

Battery equalization technology can effectively mitigate inconsistency in battery strings. In this paper, an LCC resonant converter based string-to-cell (S2C) battery equalizer is proposed to achieve easy-control battery equalization. This equalization scheme utilizes a common equalizer shared by each unbalanced cell to transfer energy from the entire string to a single cell. The proposed equalizer achieves a constant balancing current with simple fixed-frequency open-loop control. The constant balancing current facilitates a fixed equalization speed. The design considerations of the proposed equalizer are analyzed in detail, which ensures zero-voltage switching (ZVS) among all MOSFETs during the equalization process. An experimental platform to balance four Lithium-Ion battery cells is designed to verify the system performance. Experimental results validate the functionality and analysis of this battery equalizer.