The station’s 450-kW charging capacity allows for a significant reduction in charging times.
By Murray Slovick, Contributing Editor
Fast, convenient charging solutions increase the attractiveness of electric vehicles (EVs). Recently, the research consortium FastCharge presented a prototype for a 450-kW output charging station in Jettingen-Scheppach, located near the A8 motorway between Ulm and Augsburg, Germany. The charging capacity of the new fast charger is three to nine times as high as what’s currently possible with dc charging stations today.
At this ultra-fast charging station, electrically powered research vehicles from BMW and Porsche created as part of the project demonstrated charging times of less than three minutes for the first 100 kilometers of range or 15 minutes for a full charge (10-80% state of charge, SOC) of the BMW i3’s high-voltage battery, which has a net capacity of 57 kWh.
This was achieved using an intelligent charging strategy including precise preconditioning of the storage temperature at the start of charging, temperature management during the charging operation itself, and a coordinated charging capacity profile over time. The charging operation was carried out via a novel multi-voltage network on the vehicle side using a high-voltage dc-dc converter. It transforms the required 800-V input voltage of the charging station to the lower 400-V system voltage of the BMW i3 research vehicle. The system also gives the vehicle reverse compatibility, allowing it to be charged at both old and future charging stations.
A voltage of 900 V and an amplitude of 500 A yields the projected charging time of under 15 minutes assuming other technical challenges can be met, such as cooling down charging cables, plugs, and vehicle power sockets during the charging process, allowing for the use of more flexible cables with smaller diameters similar to today’s fuel hoses. For this solution, FastCharge has applied the plugs and standards of the Combined Charging System (CCS). Cooled HPC (high power charging) cables made by Phoenix Contact were used, which are fully CCS-compatible. The cooling fluid is an environment-friendly mixture of water and glycol. This makes maintenance comparatively straightforward as compared to hermetically sealed systems that use oil, for example, in terms of refilling the cooling fluid.
Participants of the three-year FastCharge project are (alphabetically): Allegro, BMW, Phoenix Contact, Porsche AG, and Siemens AG.
The Siemens energy supply system being used in the project enables researchers to test the limits of the fast-charging capacity demonstrated by vehicle batteries. It can handle higher voltages of up to 920 V—the level anticipated in future electrically powered vehicles. The system integrates both the high-power electronics for the charging connections as well as the communication interface to the electric vehicles.
This charge controller ensures the output is automatically adapted so that different electric cars can be charged using a single infrastructure. The system’s architecture permits several vehicles to be charged at the same time.
To link the system to the public power grid in Jettingen-Scheppach, a charging container was set up with two charging connections as part of the project. One connection provides a charging capacity of 450 kW maximum, while the second can deliver up to 175 kW. In each case, the charging capacity provided automatically adjusts to the vehicle’s maximum permitted charging capacity. Both charging stations are now available for use free of charge for all CCS-compatible vehicles.