Synchronous Impedance Spectroscopy Extraction From Reconfigurable Lithium-Ion Battery System via Switching Transient Signal

Cell inconsistency in large-scale energy storage system constitutes a critical bottleneck limiting operational efficiency. Reconfigurable Battery Systems (RBSs) can regulate cell interconnections within modules to achieve cell balance and optimize module performance. However, the control strategies of the RBS depend on precise states of the cells, where conventional current, voltage, and temperature measurement systems inadequately support. This letter proposes an online Electrochemical Impedance Spectroscopy (EIS) measurement method that leverages switching transients during operation of the RBS. An Energy-Focused S-Transform (EFST) is introduced to enhance high-frequency impedance acquisition capabilities during transient periods, and thus expanding the bandwidth for EIS. The proposed algorithm achieves precise extraction of cell-level EIS signals from switching transients inherent in RBS reconfiguration, enabling real-time electrochemical state assessment that directly supports advanced RBS control strategies. The validation of the proposed method is proved across a wide temperature range (- 20°C to 35°C) and multiple states-of-charge.