This paper introduces a mobile robot developed for replacing battery of electric vehicle automatically and intelligently. The developed robot based on a modular concept has four different parts, including mechanical system, control system, detecting device and driving module. The mechanical system driven by AC servo motors and controlled by control system has four degrees of freedom, and adjusting movements are independent and accurate. All measures enhance its reliability and reduce the EV charging time. This paper introduces the different parts and advantages of this charging mechanism.