Battery Management System for Li-Ion Batteries in Electric Vehicles

Electric vehicular technology is rapidly growing throughout the world. The battery in any EV is prime source of energy and it constitutes almost 50% of the total cost of an electric vehicle. The range of any EV depends on the charge health of the battery. Hence it is quite serious to protect these battery stacks by regular maintenance and monitoring. This entire job is taken care by Battery Management System (BMS). In the whole working of the BMS, cell balancing is an important task especially with Li-ion batteries. This paper presents a method of the cell balancing in Li-ion battery after finding the weak or unbalanced cells. A Bi-directional DC-DC converter configuration is presented as a centralized converter along with a switch matrix to select the cells to be balanced. The cell balancing methodology uses pack to cell to pack type of scheme. Both passive and active balancing simulations are performed in MATLAB Simulink. The results are presented to demonstrate the effectiveness of the active cell balancing algorithm and approach.