The days of using a charging cable for electric cars are numbered – and it’s unlikely that drivers will miss hanging around at charging stations. In the future, wireless charging and discharging of autonomous electric cars (also known as “inductive bidirectional charging”) will be the norm on smart roads. Now a joint project from the Institute for Automation and Communication (ifak) has brought this possibility a step closer.

The FEEDBACCAR project, which brings together ifak with the car maker Audi, Zollner Elektronik GmbH and the energy marketer e2m within the Zuse research community, has demonstrated that contactless charging can be nearly as effective as conventional cable charging. "We were able to show that not only the wireless automatic charging of e-cars, but also the feeding of battery power from such vehicles back into the power grid are technically possible without any problems," explains the project manager at ifak, Axel Hoppe in a press release.

The tests were carried out with a bidirectional inductive charger up to 11 kilowatts integrated into the vehicle within enhanced communication structures (WLAN and 5G networks). Specially-developed interoperable coil systems helped achieve the high efficiencies required. The project partners tested, among other things, fully-automatic charging of the battery and the feeding of current back into the power grid, all contactless.

"Contrary to what is often assumed, wireless charging is nearly as effective as conventional charging with a charging cable, because system efficiencies, for instance from the mains connection to the battery, of more than 90 percent are achieved," concludes Hoppe in the release.

FEEDBACCAR also looked into the economic possibilities for operators of fleet vehicles, as well as individual owners, for selling back unused electricity into the grid when the car is parked. This is particularly relevant for future car models that will shape integrated mobile solar power systems.