Charging management for car parks
In car parks with numerous charging stations for electric cars, controlled charging management is essential to avoid overloading the grid connection. Using the OCPP protocol, SCS has developed an innovative gateway together with EKZ that monitors and controls charging stations from different manufacturers.
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Initial situation
In car parks with many charging stations, the cumulative charging current can quickly exceed the capacity of the domestic connection. Coordinated control of the charging stations is therefore necessary. Different station models are often used together to form a charging system.
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SCS solution
Together with EKZ, SCS has developed the software for a local edge device that controls the charging stations via the Open Charge Point Protocol (OCPP). It also reads other electricity meters to obtain a comprehensive picture of energy generation and consumption at the installation site. The device acts as a virtual charging station and thus enables seamless integration into the charging management backend.
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Added value
EKZ offers its customers effective charging management. The edge device considers signals from the distribution grid operator and power specifications from a higher-level energy management system to ensure optimal distribution of the charging current. The system is also able to remain operational if the connection to the backend is interrupted.
Project insights
Electric cars charge with up to 32 A or 22 kW. In an apartment block, the house connection is typically designed for 500 A, with 400 A reserved for the building. The remaining 100 A for the charging infrastructure are already fully utilised with three electric cars. As many people have a similar daily routine, they often charge their vehicles at the same time at the beginning of the more favourable low tariff times.
Advantages of load management
Instead of opting for the expensive expansion of the house connection, the implementation of a load management system is a more economical option. The available power capacity is thus dynamically distributed to the loads. As an electric car only requires an average of 8 kWh per day, they can charge at reduced rates or alternately. In order to minimise charging losses, the charging power is not reduced significantly and alternating charging is started earlier instead.
Universal OCPP protocol
A universal and open charging management system is required if different charging stations are used in the car park. Together with EKZ, SCS developed software for the manufacturer-independent EKZ charging management system, which is based on the open “Open Charge Point Protocol” (OCPP) and is supported by many charging station types. This means that the solution remains future-proof and flexibly expandable without being dependent on specific manufacturers.
Edge device with algorithms
At the heart of the system is the edge device, an industrial single-board computer that acts as a gateway between the charging stations and the backend in the car park. In addition to controlling the charging stations, it records measured values from the electricity meters and takes signals from the distribution grid operator into account to optimise the distribution of the available electricity.
Security and reliability with Yocto Linux
The edge device runs Yocto Linux, a lean Linux distribution customised for the application. The connection to the backend is protected via a VPN, while the firewall only opens necessary ports. Each device uses an individual client certificate for secure VPN access and the system is robustly protected against unauthorised access. The operating system is updated over-the-air (OTA) with encrypted and signed software images. This process is robust against interruptions and faulty firmware files. In this case, the device boots into the previous system, which avoids on-site maintenance.
Successful implementation
By mid-2025, the EKZ charging management system had been installed in over 1,600 car parks with around 60,000 parking spaces without the need to extend the house connection. By monitoring the charging stations and house connection meters in real time, the edge device optimises the power distribution to the charging stations dynamically and efficiently.
(Copyright Main Picture: EKZ/Norbert Egli)