A control strategy for dynamic balancing of lithium iron phosphate battery based on the performance of cell voltage

Cell balancing is an important means to increase the capacity of the battery pack which consists of a series of cells, and to extend battery cycle life. Degree of inconsistency among cells is evaluated using capacity, charge and internal resistance. Different balancing criteria and implementations are analyzed on the conditions of battery energy storage system. Based on the cell voltage performance of the lithium iron phosphate battery, a novel control strategy for dynamic balance is proposed. The start-stop criterion of the balancer is adjusted as cell voltages changes with SOC and current. Simulation results on a cell-to-pack balance circuit show that the strategy for dynamic balance achieves SOC equilibrium among cells and solves the problems of frequent start-stop balancing and balancing current commutation, that are caused by the common strategy based on a fixed voltage threshold in the overall process.