Cell balancing: techniques, challenges and future research directions with emphasis on transportation applications

Efficient and reliable energy systems are the key to the advancement of society. High-performance batteries are essential for widely used technologies such as electric vehicles (EVs) and portable electronics. In addition, an effective battery management system (BMS) is crucial to ensure the vital parameters of the battery. However, BMS can experience cell imbalance due to charging/discharging dynamics, which reduces battery capacity, life span, efficiency and raises critical safety concerns. This requires effective cell-balancing techniques. The existing literature offers only limited coverage that integrates passive and active methods, series and parallel configurations, and transportation-sector applications within a unified framework, and in this article, cell balancing and corresponding techniques are reviewed. Initially, the authors detail a comparison of passive cell balancing techniques and assess their respective advantages, drawbacks and practical applications. The authors discuss the strengths and weaknesses of active cell balancing methods and the applicability of cell balancing for both series and parallel connected cells. In addition, the authors examine the need for cell balancing in commonly used batteries and applications in EVs. Lastly, the authors present detailed prospects that include challenges and directions for future research.