A battery control system, which controls operation of a plurality of batteries connected to an electric power system, comprises: detecting means that detects a delay period of each of the batteries which represents a period that has elapsed after the battery control system supplies the battery with an execution command for charging or discharging the battery until the battery operates according to the execution command; measuring means that measures a frequency rate-of-change of electric power of the electric power system; selecting means that selects adjustment batteries for adjusting the electric power of the electric power system from the batteries based on the frequency rate-of-change and the delay period of each of the batteries; and command means for supplying the execution command to the adjustment batteries.