VEHICLE POWER DEVICES, SYSTEMS, AND METHODS FOR SLEEP MODE

A power supply device for a vehicle includes an energy storage device, and a converter coupled to an external power source and that converts a first voltage provided by the external power source into a second voltage. The power supply device includes at least one switching element coupled between the converter and the energy storage device, and a controller that monitors a charge level of the energy storage device while the vehicle is not in operation. The control controls switching of the at least one switching element based on the charge level to either i) connect the converter to the energy storage device to exit a sleep mode and enter a charge mode to charge the energy storage device with the second voltage, or ii) disconnect the converter from the energy storage device to exit the charge mode and enter the sleep mode.