An electrical charging system for an energy accumulator of a motor vehicle. The electrical charging system comprises a supply input in a conductor system having at least one phase conductor and a neutral line for energy supply from a grid. The charging system also comprises a rotating field machine which, via its phase windings, is operably connected to a rectifier. The rectifier is provided on the other side for connection to the energy accumulator to be charged, the phase windings of the rotating field machine can be either selectively isolated and interconnected such that the charging system is designed for step-up connecter charging operation and step-down charging operation by way of at least one isolated phase winding and, in particular, all the isolated phase windings.