A Cell Equalization Method Based on Resonant Switched Capacitor Balancing for Lithium Ion Batteries

Abstract

This paper presents the concept of a cell balancing method for Lithium Ion (Li-ion) batteries for Electrical Vehicles (EV), based on Resonant Switched Capacitor Converter (RSCC) balancing technique. It equalizes eight number of cells in a series. In Li-ion batteries, voltage differences always exist between cells due to charging and discharging process, therefore a battery management system (BMS) is required to ensure that all cells are equally charged or discharged and it also increases the life cycle of the battery. An equalizing method is essential to achieve the best performance. A number of cell balancing method have been presented. Among them, Switched Capacitor Converter (SCC) is more effective compared to other methods because it can be implemented easily. Low volume, low cost, high power density are its features. However, low balancing speed is an important problem of the SCC. In this paper, a resonant switching capacitor is proposed to reduce the balancing time and reduce the energy loss. The simulation results are performed to verify the feasibility of the system.