Circuit, method, device, and energy storage system for balancing battery energy

A circuit for balancing battery energy comprising a charging branch (201) that is parallel-connected to each battery of an energy storage battery pack. Each charging branch (201) comprises: a first end of the charging branch (201) that is connected to a first output end of a charger (2011), a second output end of the charger (2011) that is connected to a second end of the charging branch (201) via a switch (K1), a first input end of the charger (2011) that is connected to a first end (A1) of the energy storage battery pack, and a second input end of the charger (2011) that is connected to a second end (A2) of the energy storage battery pack. The charger (2011) charges the battery corresponding to the charging branch (201) when the switch (K1) in the charging branch (201) is closed. The circuit allows for increased efficiency in utilizing the energy of the energy storage battery pack.