A power control device for a vehicle, the power control device comprising: a generator mounted on the vehicle and configured to regenerate power from kinetic energy of the vehicle; a high-voltage battery configured to accumulate the power regenerated by the generator; a low-voltage battery of which a nominal voltage is lower than a nominal voltage of the high-voltage battery; a voltage converter configured to lower an output voltage from the high-voltage battery and charge the low-voltage battery at the lowered voltage; a controller configured to control the voltage converter, and to operate the voltage converter to start the charging of the low-voltage battery after the vehicle is powered ON and before an engine mounted on the vehicle is started; and a relay device (6b, 6c) configured to switch between a connected state and a disconnected state of the high-voltage battery and the voltage converter; characterized by a hood sensor configured to detect an open state and a closed state of a hood of the vehicle, wherein in a state where the high-voltage battery is connected to the voltage converter and the low-voltage battery is charged through the voltage converter controlled by the controller, an update of control program the controller cannot be performed, an update of the control program of the power control device requires the hood of the vehicle to be in the open state, the controller is configured to switch the relay device (6b, 6c) to the disconnected state, when the open state of the hood is detected by the hood sensor after the vehicle is powered ON (S1-S2), if the hood is closed after the vehicle is powered ON (S1-S2), the controller allows the voltage converter to lower the voltage of the power outputted from the high-voltage battery into the low-voltage battery to charge the low-voltage battery, and as long a starter switch of the engine is not turned ON, if the hood is opened, then the lowering of the voltage by the voltage converter is suspended. a generator mounted on the vehicle and configured to regenerate power from kinetic energy of the vehicle; a high-voltage battery configured to accumulate the power regenerated by the generator; a low-voltage battery of which a nominal voltage is lower than a nominal voltage of the high-voltage battery; a voltage converter configured to lower an output voltage from the high-voltage battery and charge the low-voltage battery at the lowered voltage; a controller configured to control the voltage converter, and to operate the voltage converter to start the charging of the low-voltage battery after the vehicle is powered ON and before an engine mounted on the vehicle is started; and a relay device (6b, 6c) configured to switch between a connected state and a disconnected state of the high-voltage battery and the voltage converter; characterized by a hood sensor configured to detect an open state and a closed state of a hood of the vehicle, wherein in a state where the high-voltage battery is connected to the voltage converter and the low-voltage battery is charged through the voltage converter controlled by the controller, an update of control program the controller cannot be performed, an update of the control program of the power control device requires the hood of the vehicle to be in the open state, the controller is configured to switch the relay device (6b, 6c) to the disconnected state, when the open state of the hood is detected by the hood sensor after the vehicle is powered ON (S1-S2), if the hood is closed after the vehicle is powered ON (S1-S2), the controller allows the voltage converter to lower the voltage of the power outputted from the high-voltage battery into the low-voltage battery to charge the low-voltage battery, and as long a starter switch of the engine is not turned ON, if the hood is opened, then the lowering of the voltage by the voltage converter is suspended.