A German project has developed a fast charger design that can provide 400km of range for an electric vehicle (EV) in just 15 minutes without the need for complex cooling.
The project, called “Direct Superfast charging for the Electric vehicle”, brought together hofer powertrain, Bochum University of Applied Sciences, innolectric, Keysight Technologies, Sensor-Technik Wiedemann (STW) and Voltavision to analyze and optimize the entire energy flow chain from the power grid to the charging electronics and the charging cable to the vehicle battery.
The project developed a 450kW fast-charging station and a prototype vehicle with a 400km range that charges in just 15 minutes rather than 90 minutes for a typical 50kW fast charger.
“The challenge of the research project was to further optimize this charging power and, to this end, to modify and further develop the electronic components, charging cable technology and vehicle battery that have been common on the market to date,” says Prof. Dr.-Ing. Kai André Böhm, professor at Esslingen University of Applied Sciences and project manager of the project.
Bochum-based innolectric developed a new standard-compliant charging communication system, the DC Charging Controller, specifically for the fast charging process.
Keysight Technologies designed the power electronics for the fast-charging process, which enables the power of up to 450 kW by using silicon carbide (SiC) technology. This was used in the prototype vehicle from Bochum University of Applied Sciences that takes 400 kW of power at 460 A and up to 900 V. This would overload a normal vehicle with a common vehicle battery by a factor of four because the power loss in the battery increases by approximately quadratically with the charging current.
The battery was developed by hofer powertrain and the University of Bochum with an efficient compromise between heat generation, service life, and range. The various cell formats that made it to the shortlist were tested by the high-voltage test service provider Voltavision. The standardized and automated test procedures were modified again and again during the research project and in some cases newly developed by Voltavision.
The final battery prototype now shines with cells with a P/E ratio of 3.5 and an energy density of 210 Wh/kg. The new high power prototype battery with Li-Io technology has a voltage of 645-903 V and can hold around 128 kWh.
Various strategies for the actual charging process were also tested by hofer powertrain and employees of the Bochum University of Applied Sciences. The selection of the cells allows a charging process with a constant current of 460 A due to the optimal P/E for the fast charging process and avoided the need for an elaborate cooling concept, as the battery temperature only rises by 26 °C during the fast charging process.
The Management System (BMS) was developed by Sensor-Technik Wiedemann (STW).
With an average discharge power of 70 kW and a discharge energy of 90.3 kWh, the overall efficiency of 92 %.