BATTERY MANAGEMENT SYSTEM, BATTERY PACK, ENERGY STORAGE SYSTEM AND BATTERY MANAGEMENT METHOD

Discussed is a battery management system that may include a battery monitoring device to detect a voltage of each of a reference battery cell and a plurality of battery cells having a common flat region, and detect a current of the battery pack, and a control circuit to stop a charging of the battery pack, initialize a cumulative current value, and determine a state of charge (SOC) of the cell group to be equal to a sum of an SOC of the reference battery cell and the predetermined value, when the voltage of the reference battery cell reaches a reference voltage during the discharge of the battery pack.