A vehicle having wheels for riding the vehicle over a carrier such as a road or rails, said vehicle having a battery and a generator connected thereto, said generator having a stator and a rotor being arranged to generate electrical power for charging said battery, wherein said wheel drives said rotor by means of a shaft connected to the centre of said wheel and axially extending therefrom, wherein the connection between said rotor and said shaft comprises a gear box for regulating the rotation speed of said rotor relative to the rotation speed of said wheel, characterized in that said gear box comprises a planetary gear train of the type having a sun gear, planet gears and an annular gear, and that said shaft, said sun gear and said rotor extend around a common axis.