Modeling of single inductor based battery balancing circuit for hybrid electric vehicles

Li Ion batteries are the proficient energy source for powering Hybrid Electric Vehicles (HEV) due to its smaller size, lighter weight, and improved charge efficiency without memory effect. The battery pack constitutes of a combination of cells in series and parallel configurations. Due to cell impedance mismatch, each cell possesses different potentials which cause different State of Charge (SOC) of cell. Battery balancing is a key issue which aims to maximize the capacity of the battery pack to make all of its energy available for use and also increase the battery's endurance. This paper presents an automatic battery balancing circuit model by using single switch inductor with SOC based logic controller. The performances during static, charging, discharging and mixed conditions are analyzed. The main advantage of the proposed approach is that it has fastest equalisation time due to constant inductor current which is controlled by Proportional Integral (PI) controller and SOC-based logic controller for controlling the switching action.