Challenge / Goal
In the company car park of MAHLE 100 AC charging points have been installed for employee cars and company cars in order to reduce pollution in Stuttgart city. At the same time, the installation serves as a demonstrator and a real lab for further development of the chargeBIG charging infrastructure. The project was funded by the German Federal Ministry of Economics.
The objectives of the project were:
· Reduce air pollution in Stuttgart City (in particular NOx)
· Enable e-mobility at work for drivers who cannot charge at home
· Realize a large charging infrastructure with old and limited electric grid connection
· Develop a charging infrastructure with the lowest cost
· Have a real-life life test field for further development of chargeBIG charging infrastructure
The new developed chargeBIG charging solution is an single-phase "AC Destination Charging" with charging capacities between 2.3 and 7.2kW and consists of a central and intelligent control unit - the charging cabinet - and permanently attached cables with plugs instead of charging pillars or wall boxes at the parking slots. Depending on the parking slot, the device is equipped either with a stand pillar or a wall bracket with a permanently attached charging cable. Instead of installing expensive components at each parking place, the necessary components (e.g. charge controller, energy measurement, fuses, etc.) are placed in the central charging cabinet. A single charging cabinet can control up to 36 charging points with single-phase charging power. For the demonstrator at MAHLE with 100 charging points three charging cabinets have been installed. The 100 charging points includes four three-phase AC charging points with 22kW.
Centralization offers considerable cost advantages not only in production but also in maintenance. The centralization also offers advantages over conventional solutions in the areas of communication and IT security. In addition, chargeBIG has a clear advantage in terms of electric safety. A charging point is only supplied with power when a vehicle is connected. In cases of vandalism or accidents there is no danger because the charging point is without power.
The demonstrator is completed by a battery storage with 60kW power and 66kWh energy, a DC charger with up to 120kW power out of the battery and a PV installation with 70kW peak in order to charge the electric cars with green power.
The power supply for this 100 charging point demonstrator is an old transformer with about 200 to 300kW remaining power. No update for the connection to the electric grid was necessary. This became possible by the use of dynamical phase-individual load management. The available power is dynamically distributed to all charging cars. The electric cars are used as a controllable load. If a car is charged the whole day during parking, charging with low power is sufficient.
MAHLE’s corporate start-up chargeBIG has successfully passed the VDE’s certification procedure end of March 2021. This means that chargeBIG, with the support of the calibration authorities in the relevant federal states, can now bill customers in compliance with the German Measurement and Verification Act. Based on this certification, the charging hardware and software in the car park in Stuttgart is under revision, so that the billing process is conform to the callibration law.
The charging infrastructure is open to visitors of the municipal zoological garden on the weekends to recharge their electric car
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