Inner workings of a charging station

RCD

The current first passes through the residual current circuit breaker (RCCB). This monitors the circuit and trips as soon as a residual current (AC) is detected.
This ensures that there is no danger to people or equipment in the event of a fault in the supply line or the station. The RCD is therefore the first safety network of the charging station.

Installation contactor

After the RCD, the current flows through the installation contactor – basically a remote-controlled on/off switch. It starts and stops the current flow as soon as a signal is received from outside, for example through phase current detection or the start of the charging process.

Phase current detection

The power grid in buildings consists of three so-called phases, which must remain in balance. Phase current detection measures whether the vehicle is drawing excessive current from one or more phases. If the grid becomes unbalanced as a result, the system sends a signal to the installation contactor – the charging process is automatically stopped to ensure grid stability.

DC residual current module

While the RCD monitors the alternating current (AC), the DC residual current module protects the charging station on the vehicle side. It prevents faulty direct currents (DC) from the vehicle from reaching the house connection and impairing the electronics or safety equipment there.

In some wallboxes, a type B RCD is installed instead, which detects both AC and DC residual currents. However, the separate DC module has an advantage: it checks the situation again after a fault and can automatically resume operation in many cases – without manual intervention.

Energy meter

If no fault currents are detected, the current continues to flow to the energy meter. Here, the actual power consumption is measured in kWh – i.e. only the power that actually reaches the vehicle battery. The station’s own consumption is not measured, which enables billing in compliance with calibration law. Drivers therefore only pay for the energy that was actually charged.

Logging gateway

The energy values from the meter are signed and stored in the logging gateway. This signing ensures that the values remain unchanged and traceable – an important component for legally compliant operation and transparent billing of charging processes.

Emergency capacitor

In the event of a power failure, operation of the charging station would be interrupted – and the plug lock would remain active. This is where the emergency capacitor comes in: it ensures that the plug can still be unlocked so that the charging cable can be safely disconnected.

EVCC – the brain of the charging station

The Electric Vehicle Charge Controller (EVCC) is the central control module of the charging station. It communicates with the vehicle, the DC residual current module and the phase current detection and activates the charging process via the installation contactor. In short: no charging station would work without the EVCC.

Backend

Modern charging stations also have a backend system that transmits data from the EVCC and energy meter to a cloud via a SIM card or internet connection.
There, users and charging processes can be managed, billed and controlled using software. Several charging stations can thus be intelligently networked to efficiently distribute the available electricity – this is the basis for smart load management.

Conclusion

A charging station is much more than just a socket. It combines precise measurement technology, intelligent control and the highest safety standards. Thanks to modern software solutions, it becomes the heart of a safe, efficient and sustainable charging infrastructure.