VEHICLE-MOUNTED POWER SOURCE DEVICE

The vehicle-mounted power source device comprising: a low-voltage battery; a high-voltage battery; a boost unit that boosts electrical power for charging the high-voltage battery; a solar panel that converts solar light to electrical power; a bi-directional buck-boost unit that boosts/bucks the electrical power converted by the solar panel; and a control unit that performs control in a manner so as to charge the low-voltage battery by means of electrical power of which the voltage has been altered by the buck-boost unit. When the amount of stored electrical power at the low-voltage battery is at least a predetermined value, the control unit performs control in a manner so that the electrical power stored at the low-voltage battery is boosted by the boost unit and the bi-directional buck-boost unit, and the high-voltage battery is charged by means of the boosted electrical power.