Power source device

A power control device for a vehicle includes a first battery (B1), a second battery (B2), the voltage of which is lower than the voltage of the first battery, and a transformer (57). The transformer (57) includes a primary coil (57a), to which an alternating-current power source (67) is connected, a first secondary coil (57b), to which the first battery (B1) is connected, and at least one second secondary coil (57c), to which the second battery (B2) is connected. A rectification circuit (62) is located between the second secondary coil (57c) and the second battery (B2). A voltage adjustment circuit (63) is located between the rectification circuit (62) and the second battery (B2). A control section (66) charges the first battery (B1) using the alternating current power source (67), and, simultaneously supplies electrical power to the second battery.