Battery equalization based on state of charge

With the development and popularity of Lithium battery powered PEVs (Pure Electric Vehicles), BMS (Battery Management System) with equalization techniques become a key issue in high performance PEV design. This paper introduces a linear regression based real-time State of Charge calculation method through a second-order RC model of Lithium batteries. Then a fuzzy control method is adopted to balance the remaining capacity among batteries by a set of bi-directional fly-back DC-DC converters. Test bed experiments show that the proposed equalization system can provide effective balance result with relative high overall performances, energy efficiency and robustness.