Novel Direct Active Cell-to-Cell Balancing Approach for Energy Storage Systems based on a Flying Inductor Circuit Topology

State-of-the-art energy storage systems utilize many battery cells in series and parallel connection to provide the required energy and power for the individual use case. In such applications, e.g. electric mobility or grid energy storages, monitoring and balancing systems for every individual cell are required. Cell voltage deviations are naturally intrinsic and are caused by different chemical, electrical and thermal properties of each cell as well as cyclic and calendric aging. This paper deals with a new active flying inductor balancing concept and its implementation. In contrast to other topologies, which often transfer energy through adjacent cells only, the proposed approach enables direct energy transfer between any two cells requiring only one inductor as intermediate storage. The circuit topology and consecutive addressing of cells also allows implementation of cell voltage monitoring simultaneously to the balancing process, making additional sensors unnecessary. A customized implementation of algorithms, such as energy-based or voltage-based balancing is possible. Simulations and experimental results validate the proposed approach and indicate high efficiency and balancing rate.