Extender charging stations are charging stations that are connected to the master and cannot communicate independently with the backend. The connection between the reev backend and a charging group runs exclusively via the master charging station, which is connected to the mobile network. For this purpose, an LTE stick, incl. SIM card is installed in the control unit for the master charging station or the external control center for the charging group. The data exchange between master and extender charging stations takes place via BUS cabling.