ENERGY STORAGE SYSTEM

The energy storage system of the present disclosure includes: a battery configured to store a received electrical energy in a form of direct current or to output the stored electrical energy; and a battery management system configured to control the battery, wherein the battery management system includes: a sensing unit comprising a plurality of sensors for measuring voltage, current, and temperature of the battery; a memory configured to store a charge/discharge cycle count that is increased according to execution of charge/discharge cycle and a under voltage protection level which is a reference value of a under voltage protection that protects from discharging at a certain voltage or lower; and a microcomputer unit that increases the under voltage protection level, when the charge/discharge cycle count reaches a reference number of times.