Switched-capacitor charge equalization circuit for series-connected batteries

The charge unbalancing decreases the total storage capacity and the entire life cycle of batteries. In order to prevent the charge differences among cells, cell balancing system or charge equalization have been proposed. This paper proposes an active balancing system based on switched-capacitor charge equalization for series-connected batteries. This circuit topology allows two series-connected cells to charge one capacitor and then the charge of capacitor will be transferred to the other cell which is insufficiently charged. In order to achieve better efficiency, cell voltages are monitored to decide which cell is insufficiently charged. Besides, small inductors are inserted into the switching capacitors charging path to reduce the current spikes.