A charging group can be identified via the respective master charging station. Each charging group can include several extenders in addition to the master. Communication between the reev backend and a charging group takes place exclusively via the master. For this purpose, an LTE stick, including a SIM card, is installed in the control unit for the master charging station. The data exchange between the communicating master charging station and the connected extender charging stations in a charging group takes place via BUS cabling.