System of charging battery of vehicle and method for controlling the same

A method for controlling a system of charging a battery of a vehicle, the method comprising:

• receiving, from a controller, a charge start signal for starting to charge a first battery with a relay open, wherein the first battery is connected to a first direct current (DC) converter and is to be charged with a DC voltage converted by the first DC converter;
• charging, controlled by the controller, a DC capacitor of a charger up to a predetermined initial charge voltage using power stored in a second battery by operating the first DC converter and a second DC converter in a backward direction, wherein the DC capacitor is configured to receive a DC voltage converted from an alternating current (AC) charge voltage and wherein the second DC converter is connected to the battery of the vehicle and converts a magnitude of a voltage of the first battery;
• and
• charging, controlled by the controller, the first battery by changing the relay into a short state and operating the first DC converter in a forward direction to apply a voltage converted from the AC charge voltage to the first battery,
• wherein the first DC converter converts the magnitude of a voltage of the DC capacitor,
• wherein the relay is connected between a charge input terminal and the charger, the charge input terminal is a terminal to which the AC charge voltage is input, and
• wherein the second battery receives a DC voltage provided by the second DC converter.