BATTERY DEVICE AND METHOD FOR INSTALLING AND OPERATING SAME

Frequent charging/discharging to an electric energy storage element is suppressed to accomplish an energy saving and a longer lifetime. A transmission-line-side power converter device 2 converts power from a transmission line 1, and supplies DC power to a feeder line 3. The feeder line 3 is connected to an electric energy storage element 4 via a power converter device 5. An output current controller 6 is connected with a line voltage detector 7 that detects a line voltage of the feeder line 3, and a charging rate detector 8 that detects a charging rate SOC of the electric energy storage element 4. The output current controller 6 is connected with a control table 9 that sets charging/discharging start voltages and charging/discharging current saturated voltages based on the detected line voltage and charging rate. The control table 9 is provided with a data inputter/outputter 10. The output current controller 6 performs a control in such a manner as to facilitate the electric energy storage element to discharge even at a high line voltage as the charging rate becomes high, and to suppress the electric energy storage element to be charged at the low line voltage. Moreover, the output current controller 6 controls in such a manner as to make the discharging difficult at a low line voltage and to facilitate charging at the low line voltage as the charging rate becomes low.