A Battery Management System (BMS) includes a sensing unit and a Micro Control Unit (MCU). The sensing unit measures a battery current, a battery voltage, and a battery temperature. The MCU determines a State of Charge (SOC) reset point based on the measured battery current and voltage. The BMS determines a battery overcharge state using a current integration result after the SOC reset point is reached. The MCU includes an SOC calculator and a full charge determining unit. The SOC calculator transmits a present current integration value upon detecting the SOC reset point. The full charge determining unit receives the present current integration value, integrates the current using the measured battery current, and determines that the battery is being overcharged when the current integration value reaches a predetermined battery rating capacity.