An Improved Battery Equalizer with Reduced Number of Components Applied to Electric Vehicles

Abstract

The investigation of electric vehicle technologies has increased significantly in the last few years. These vehicles can substantially reduce the environmental impact of the transportation sector. In electric cars, the battery is a crucial element. The batteries are made up of several stacked cells to meet the requirements of the propulsion system. Battery equalizer circuits take active measures to ensure that a particular variable is kept inside an allowable range in all cells. Inductor-based equalizers are very popular since the equalization current is controlled. This paper proposes a single-inductor architecture with a reduced number of components. The proposed topology can transfer energy from adjacent cell-to-cell or adjacent string-to-string. This paper analyzes the operation of the converter, its design, and the design of the controller. Furthermore, a comparison of the proposed equalizer with other inductor-based schemes was made considering the component count, stress on devices, equalization time, driver complexity, and other parameters. The theoretical efficiency of the proposed equalizer obtained was 84.9%, which is competitive with other literature solutions. The impact of battery size on the number of circuit components was also analyzed. Finally, simulation results in open load and changes of current through the battery conditions were performed to validate the theoretical analysis.