This model car uses a reversible PEM (proton exchange membrane) fuel cell. Hydrogen and oxygen gasses are stored in the tanks located in the back of the car. The gasses react in the fuel cell (center) and produce water and electrical current that drives a small electric motor (front). Prior to the use, the tanks need to be filled. Hydrogen and oxygen are produced in the fuel cell using electrolysis of water powered by an external battery. The battery is completely disconnected after the gas tanks are filled.