A balancing circuit for a plurality of series connected cells or substrings of cells is provided. In one implementation, the balancing circuit includes a plurality of primary ports; an isolated secondary port; and one or more DC-DC converters connected between the primary ports and the isolated secondary port. Each DC-DC converter includes at least one power switch. The DC-DC converters are configured to adjust a primary port current received at one or more of the plurality of primary ports based upon a difference between a voltage at the one of the primary ports and a reference voltage. Also provided are an electrical power system including such as balancing circuit and a method of balancing a plurality of electric cell substrings using such a balancing circuit.
GOVERNMENT LICENSE RIGHTS
 This invention was made with government support under grant number DE-AR0000216 awarded by the U.S. Department of Energy. The government has certain rights in the invention.