FIG. 11 is a block diagram showing an example of a system including a stationary power supply according to the fifth embodiment. FIG. 11 is a diagram showing an application example to stationary power supplies 112, 123 as an example of use of battery packs 300A, 300B according to the third embodiment. In the example shown in FIG. 11, a system 110 in which the stationary power supplies 112, 123 are used is shown. The system 110 includes an electric power plant 111, the stationary power supply 112, customer side electric power system 113, and an energy management system (EMS) 115. Also, an electric power network 116 and a communication network 117 are formed in the system 110, and the electric power plant 111, the stationary power supply 112, the customer side electric power system 113 and the EMS 115 are connected via the electric power network 116 and the communication network 117. The EMS 115 performs control to stabilize the entire system 110 by utilizing the electric power network 116 and the communication network 117.
