Generally, a vehicle is a machine capable of running by using a motor as a power source, capable of carrying persons or freights, or capable of executing various types of functions. A vehicle may be classified according to a motor type. For example, a vehicle may be classified as a gasoline vehicle using a gasoline engine as a motor, a diesel vehicle using a diesel engine as a motor, a liquefied petroleum gas (LPG) vehicle using liquefied petroleum gas as fuel, a gas turbine vehicle using a gas turbine as a motor, or an electric vehicle (EV) using a motor and using electricity charged in a battery. In case of a vehicle using a fossil fuel such as gasoline, diesel, or LPG, environment pollution due to exhausted gas may be caused and petroleum resources may be exhausted.
Accordingly, electric vehicles using electricity as a driving power are being considered. An electric vehicle adopts a driving motor which obtains driving power by receiving electricity from a battery. As compared to an engine which obtains driving power by using fossil fuel such as gasoline or diesel, an electric vehicle does not cause discharge of carbon oxide. Thus, electric vehicles have been spotlighted as eco-friendly vehicles. Recently, electric vehicles have been being rapidly developed due to high oil prices and reinforced regulations on exhaustion gas.