Voltage-SOC balancing control scheme for series-connected lithium-ion battery packs

The basis for determining whether the cell needs to be balanced is generally the voltage or SOC (state of charge), the voltage balancing control scheme is simple but performs poorly, the SOC balancing control scheme performs well but needs to estimate the SOC of all cells. Based on the analysis why existing naive approaches are not effective for voltage balancing control scheme, the voltage-SOC balancing control scheme is proposed, which has the advantages of simple of voltage balancing control scheme and well performance of SOC balancing control scheme. By utilizing the difference of voltage of cell and SOC of battery pack, the difference of SOC between two cells can be obtained indirectly, and the transition from voltage balancing control scheme to SOC balancing control scheme can be realized, while the advantages of voltage balancing control scheme and SOC balancing control scheme are retained. The 4 experiments designed show that the estimated errors of the difference between the SOCs of the two cells are 0.24%, 5.3%, -5%, and 0.8%, respectively, which proves the excellent performance of voltage-SOC balancing control scheme.