Cell balancing in battery management system

Abstract

The common subsystems of battery management system (BMS) in Electric Vehicle are SOC estimation, cell balancing and thermal management. The subsystems of the BMS are required to operate in real time and rapidly charging and discharging conditions. Besides, the BMS should be properly designed so that it can operate in harsh environment. Cell balancing is a very important subsystem of BMS which will prolong the life of battery. In this aspect, cell balancing system is not only covers the task of protecting the cells, it also includes the task for charge equalization among the cells. The most common type of cell protecting system applied in electronic device is interruption of the charging and discharging of the battery to avoid the battery in reaching its maximum and minimum allowable voltage. On the other hand, the charge imbalance among batteries may cause a slight mismatch on capacity or temperature differences of series connected batteries. The charge imbalance occurs in the form of unequal voltages along the battery string. The two major categories of cell balancing methodologies are active methods and passive methods. In this project, all the categories of cell balancing will be studied extensively, and an efficient and suitable converter based active method is proposed and simulated using MATLAB/SIMULINK.