A converter can selectively use reactors through an ON-OFF control on relays by an electronic control unit. The first reactor is disposed as a component of the converter separately from a main battery. On the other hand, the second reactor is so disposed as to have a heat transfer path between the second reactor and the main battery. At least based on the output from the temperature sensor, in a low temperature state of the main battery, the electronic control unit turns off the first relay, and turns on the second relay, thereby configuring a reactor of the converter by using the second reactor.