Fast Active Balancing Circuit for Li-ion Battery Modules using a DC-DC Bipolar Converter

In this paper, a non-isolated DC-DC bipolar converter for fast balancing of series-connected Li-ion batteries is introduced. It is an active balancing circuit with the ability to transfer energy from an auxiliary source to the cells. Due to the importance of balancing time, in this method, energy is transferred to two adjacent cells, simultaneously. Since energy is injected into two cells simultaneously, the balancing time is reduced. To control the DC-DC converter, a PI controller is designed. To investigate the converter, its state space model has been acquired and the simulation results have been evaluated. The simulation results show the equalization time is significantly reduced.