Patent ID: 8405349

Claim:
An energy storage system comprising: a plurality of batteries connected in series; a first regulator circuit configured to balance voltages across two first battery sets of the plurality of batteries, the first regulator circuit comprising at least one switchable connection and at least one energy storage unit, wherein the at least one switchable connection connects the at least one energy storage unit to the two first battery sets; a second regulator circuit configured to balance voltages across two second battery sets of the plurality of batteries, wherein each set in the two first battery sets includes one set from the two second battery sets; and a controller connected to the first regulator circuit and the second regulator circuit and configured to: monitor voltages across the two first battery sets and voltages across the two second battery sets; identify voltage imbalances between the two first battery sets and voltage imbalances between the two second battery sets; and adjust the first regulator circuit and the second regulator circuit to minimize the voltage imbalances between the two first battery sets and the voltage imbalances between the two second battery sets.