A first electrical storage stack is connected in series with a second electrical storage stack. A current interrupter is configured to interrupt a current path by being removed from the current path. First and second detection line are respectively connected to first and second terminals of the first electrical storage stack. The second electrical storage stack is connected to the second terminal of the first electrical storage stack via the current interrupter. A third detection line is connected to a portion of the current path, located on the second electrical storage stack side of the current interrupter. A controller is configured to control charging and discharging operations of each of the first and second electrical storage stacks on the basis of the voltage of the first electrical storage stack, the voltage being detected via the first detection line and the third detection line.