A New Battery Active Balancing Method with Supercapacitor Considering Regeneration Process

Lithium-ion batteries have been widely used in new energy vehicles (NEV) as large energy storage systems (ESS). It is necessary to balance series-connected cells to avoid over-charging or over-discharging as well as to improve the amount of usable energy. This paper starts with a comprehensive review of the existing strategies and gives a battery balancing category. A new balancing topology with its control algorithms is then introduced. A supercapacitor is used in the balancing circuit which replaces the highest state of charge (SOC) cell and is charged during the vehicle regeneration process. The supercapacitor also transfers energy to the lowest SOC cell after it is fully charged. This new strategy can not only improve the balancing efficiency due to fewer times of energy conversion but also reduce the required balancing time compared to single capacitor balancing.