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Lithium battery has become the main power source of new energy vehicles due to its high energy density and low self-discharge rate. In the actual use of the series battery pack, due to the internal resistance and self-discharge rate of batteries and other factors, inconsistencies between the individual cells are unavoidable. Such inconsistencies will reduce the energy utilisation rate and service life of the battery pack, and even endanger the safety of the battery systems. To improve the consistency of the series battery pack, a novel balancing method based on the flyback converter is proposed in this study. The flyback converter with a simple and reliable structure is used to realise the energy transfer between the whole battery pack and any single cell. Compared with the traditional balancing topology, the topology proposed in this study reduces the number of components and the volume of the balancing system, and only needs one set of control signals on the converter primary side, thus reducing the control difficulty. The experimental results show the effectiveness of the novel balancing method.

An active balancing method based on two flyback converters is proposed for series-connected battery pack. Balanced energy can be transferred between the whole battery and any single cell. The proposed topology reduces the number of energy storage components, the volume and the cost of the balancing system. And it has the characteristics of fast balancing speed and high balancing efficiency. Based on the topology, a dual-objective hybrid control strategy is proposed, which can reduce the highest voltage and boost the lowest voltage in the charging or discharging process of the cells in one sampling period, so as to improve the balancing speed. Simulation and experimental results show that the proposed method has a good balancing effect and can significantly improve the consistency of series battery pack. This work is potentially significant in terms of improved reliability of battery packs and savings of costs and lives in safety-critical applications.