Provided are a battery management system, a battery management method, a battery pack and an electric vehicle. The battery management system includes a sensing unit to generate battery information indicating a current, a voltage and a temperature of a battery, and a control unit. The control unit determines a temporary estimate for a SOC in a current cycle using a time update process of an extended Kalman filter based on a previous estimate indicating a SOC in a previous cycle and the battery information. The control unit determines open circuit voltage (OCV) information based on the temporary estimate. The control unit determines a definitive estimate indicating the SOC in the current cycle using a measurement update process of the extended Kalman filter based on the temporary estimate, the OCV information and the battery information.