A converter includes a plurality of switching elements, at least one capacitance, and a resonant circuit. The plurality of switching elements include a first switching element coupled to a first control signal line that controls switching of the first switching element, a second switching element coupled to a second control signal line that controls switching of the second switching element, a third switching element coupled to a third control signal line that controls switching of the third switching element, and a fourth switching element coupled to a fourth control signal line that controls switching of the fourth switching element. The plurality of switching elements, the resonant circuit, and the at least one capacitance operate to convert a first voltage into a second voltage that charges a first battery and a second battery.