An Active Equalization Method for Cascade Utilization Lithium-Ion Battery Pack With Online Measurement of Electrochemical Impedance Spectroscopy

With the rapid development of new energy vehicles, a large number of lithium batteries have been produced, used, and then retired. The full utilization and safe use of the whole life cycle of the batteries have become a hot topic in the research field. Compared to brand-new batteries, retired power batteries exhibit significant inconsistency and safety risks, thus necessitating effective battery equalization and safety monitoring methods. In this article, an active equalization method for cascade utilization lithium battery pack with online measurement of electrochemical impedance spectroscopy is proposed to actively equalize the retired battery pack and alleviate the inconsistency of the battery pack. Besides, the electrochemical impedance spectrum of the single battery is measured online without adding additional hardware circuits so as to realize real-time safety monitoring and solve the safety problem of the battery. Finally, in order to verify the feasibility of the active equalization and electrochemical impedance spectrum monitoring scheme designed in this article, a simulation model is built based on the matlab-Simulink platform. The simulation results show that the six batteries in the proposed scheme model complete the active equalization in about 710 s, 850 s, and 740 s, respectively, in the balance mode, charge mode, and discharge mode, and the electrochemical impedance spectrum in the frequency range of 1–20 KHz can be successfully measured.