Advanced cell-to-cell equalisation strategy for series connected Li-ion batteries in xEV applications

Lithium-ion batteries are widely used in energy storage systems for electric vehicles (EVs) and renewable applications due to their high energy density and long lifespan. However, cell imbalance in battery packs leads to non-uniform states of charge (SoC), degrading performance, reducing cycle life, and posing safety risks such as thermal runaway. Traditional passive balancing dissipates excess energy as heat, while active balancing improves efficiency but increases cost and complexity. This paper proposes a novel interleaved flyback converter (IFBC) topology for active cell balancing, enabling efficient energy transfer and minimising heat dissipation with reduced system complexity. A 48 V battery pack with 12 series-connected cells using IFBC was developed and tested under charging, discharging, and normal modes. The system maintains a SoC difference below 2% for optimal balancing, achieving balance in 172.5, 352.3, and 238.2 seconds, respectively, across the three modes, demonstrating its effectiveness for practical battery management applications.