Modeling, Evaluation, and Comparison of Battery Equalizers Based on the Conservation of Energy

Equalization systems significantly affect the performance and lifespan of battery packs. As battery packs increase in size and complexity, accurate and computationally efficient tools for evaluating equalizers become increasingly important. Mathematical modeling offers a practical alternative to real-time simulations and experimental testing, which can be costly and time-consuming. However, conventional modeling approaches often experience accuracy limitations during long-duration equalization, reducing the reliability of estimations. This paper presents simplified yet highly accurate mathematical models for various equalizers based on the conservation of energy. The models incorporate converter efficiency and use a closed-form interval-based approach that significantly reduces memory usage and computational load. A comprehensive comparison of equalizer performance is conducted using the proposed models, and novel metrics are introduced for improved evaluation of energy redistribution and loss. The results demonstrate that the proposed models predict equalization time and voltage with less than 1% error. In simulation and cycle-by-cycle-based approaches, the processing time increases to days as battery capacity grows; However, the closed-form model exhibits capacity-independent computation time, enabling high scalability for large EV packs. Furthermore, the results show that direct-cell-to-cell equalizers achieve higher energy transfer efficiency, while adjacent-cell-to- cell structures provide faster equalization, offering practical guidance for topology selection in EV applications.