Key performance metrics in battery equalization systems include equalization speed, energy flow path length and control complexity. In this digest, we propose a string-to-cell equalizer based on the C2L3 resonant topology to achieve a good comprise among those metrics. The proposed equalizer hybridizes constant current (CC) and constant voltage (CV) balancing in different stage of equalization, ensuring both fast speed and high accuracy. Moreover, we adopt direct string-to-cell (S2C) and cell-to-string (C2S) connections to minimize energy flow path length. By achieving zero-voltage-switching (ZVS) in all MOSFETs, we can boost the conversion efficiency. A functional prototype of the equalizer is constructed and tested. The recorded peak efficiency reaches 88.89% and 83.65% in S2C and C2S modes, respectively. These results demonstrate the efficiency and effectiveness of the proposed design across different operational modes.
