Battery Cell Reconfiguration to Expedite Charge Equalization in Series-Connected Battery Systems

Abstract

As a common issue of battery systems, the charge imbalance among battery cells/modules/packs may cause reduced charge capacity, low energy efficiency, accelerated degradation, and even fire hazard. To battle this issue, various circuit designs and control strategies have been developed in past decades. In these research and development efforts, the equalization time, which is defined as the time needed for the battery system to reach charge equalization, is often regarded as one of the most important performance measures. While great efforts have been made to shorten the charge equalization time through the designs of balance circuits and control strategies, limited attention is given to the battery cell reconfiguration. Indeed, numerical experiments show that the equalization time can be significantly affected by the connection pattern of battery cells. In this letter, we study such effects in battery systems with series-based charge equalization structure, and develop the cell reconfiguration algorithm to quickly identify a cell connection configuration with near-minimum charge equalization time. Numerical simulation shows that the proposed algorithm can significantly expedite the charge equalization process.