A method of operating a storage battery device installed in a railroad vehicle, wherein: the storage battery device comprises at least one battery module comprising an assembled battery including a plurality of battery cells, a cell monitoring unit that detects a voltage and a temperature of each of the battery cells, and a temperature adjusting unit that adjusts the temperature of each of the battery cells; a heating unit that heats a medium supplied to the temperature adjusting unit and outputs the heated medium; a cooling unit that cools the medium supplied to the temperature adjusting unit and outputs the cooled medium; and a battery management unit including a temperature detector and a battery temperature controller, the temperature detector configured to communicate with the cell monitoring unit and an outside, and to detect a temperature of the medium, the battery temperature controller performing temperature control of the battery cells by controlling the heating unit and the cooling unit using the temperature of the medium detected by the temperature detector, a computed SOC of each of the battery cells, and the voltage and temperature of each of the battery cells received from the cell monitoring unit of the battery module to adjust a temperature of the medium, the method comprising: - receiving an operation plan of the railroad vehicle for a predetermined period of time from the outside, and - computing a prediction value indicating a change over time of the SOC of the battery cell based on the operation plan, to set a time of day for performing the temperature control of the battery cells based on the operation plan, and to perform the temperature control of the battery cells. the storage battery device comprises at least one battery module comprising an assembled battery including a plurality of battery cells, a cell monitoring unit that detects a voltage and a temperature of each of the battery cells, and a temperature adjusting unit that adjusts the temperature of each of the battery cells; a heating unit that heats a medium supplied to the temperature adjusting unit and outputs the heated medium; a cooling unit that cools the medium supplied to the temperature adjusting unit and outputs the cooled medium; and a battery management unit including a temperature detector and a battery temperature controller, the temperature detector configured to communicate with the cell monitoring unit and an outside, and to detect a temperature of the medium, the battery temperature controller performing temperature control of the battery cells by controlling the heating unit and the cooling unit using the temperature of the medium detected by the temperature detector, a computed SOC of each of the battery cells, and the voltage and temperature of each of the battery cells received from the cell monitoring unit of the battery module to adjust a temperature of the medium, the method comprising: - receiving an operation plan of the railroad vehicle for a predetermined period of time from the outside, and - computing a prediction value indicating a change over time of the SOC of the battery cell based on the operation plan, to set a time of day for performing the temperature control of the battery cells based on the operation plan, and to perform the temperature control of the battery cells. - receiving an operation plan of the railroad vehicle for a predetermined period of time from the outside, and - computing a prediction value indicating a change over time of the SOC of the battery cell based on the operation plan, to set a time of day for performing the temperature control of the battery cells based on the operation plan, and to perform the temperature control of the battery cells.