Active Cell Balancing Circuit using Switched inductor Buck-Boost Converter for Li-ion Battery Strings with Maximum Efficiency Operation

An active cell balancing circuit with maximum efficiency operation using switched-inductor buck-boost converter for series connected battery strings is presented in this paper. The proposed balancing circuit has advantage over conventional balancing circuit, which is the ability to balance non-adjacent cells also. Moreover, it simplifies control complexities by utilizing one pair of complementary PWM signals to balance all the cells within the battery module. To form a single module with three cells connected in series, the proposed balancing circuit requires only two inductors and four switches. The analysis, modes of operation and control strategy of the proposed circuit are described in detail. The energy transfer with the efficiency of 97.7% is achieved with proposed balancing circuit. To verify the proposed circuit, MATLAB/Simulink platform is utilized and a laboratory prototype is developed.