Each of the switching elements S1 to S4 of the electric power converter 11 is, for example, a transistor element, such as an IGBT. As will be described later, each of the switching elements S1 to S4 is turned on or off in accordance with the logical addition of a PWM1 and a PWM2. The PWM1 is a first PWM signal. The PWM2 is a second PWM signal. The switching elements S1 to S4 are connected in series with each other such that the direction from a high-voltage line 26 toward a reference line 28 is a forward direction. The high-voltage line 26 is an output line of the electric power converter 11. In addition, diodes D1 to D4 are respectively connected in antiparallel with the switching elements S1 to S4.

The electric power converter 11 includes a first reactor L1 and a first capacitor C1. The first reactor L1 is connected in series with the first battery B1. The first capacitor C1 is connected in parallel with the first battery B1. The electric power converter 11 includes a second reactor L2 and a second capacitor C2. The second reactor L2 is connected in series with the second battery B2. The second capacitor C2 is connected in parallel with the second battery B2.