A method for operating a charging device for a battery of a motor vehicle. The charging device converts electric power obtained from a motor vehicle-external, three-phase energy system supplying other consumers in an infrastructure unit, in particular a house, by a converter device into an electric current that is suitable for charging the battery, and supplies electric energy of the battery by the converter device into the energy system. The charging device receives in an operating phase phase-resolved power data, which is fed to the energy system and measured by a measuring device, and determines phase-specified target power while using phase-related power data outputs for each phase. The target power that is determined for each phase is retrieved from each phase.