Most wireless EV charging systems use an induction coil on the underside of the vehicle and a floor-mounted charging station, but researchers at the Fraunhofer Institute for Integrated Systems and Device Technology (IISB) in Germany are developing an alternative method that makes the connection at the front end of the vehicle. This addresses a number of problems.
According to the Fraunhofer team, the underside approach requires larger, more powerful coils because of the gap of up to 15 cm between car and ground, which drives up costs. With the front-end system, the car is positioned almost touching the induction source, allowing for the use of smaller coils: 10 cm instead of 80 cm across.
The plastic charging column is approximately waist-high, and is designed to bend backwards, or even to flip down and out the way if pushed by the vehicle. “The car could drive over it if necessary,” says IISB’s Dr Bernd Eckardt. “Touching the charging station causes no damage to the car body.” Charging can take place even if the vehicle is not perfectly positioned, and current can flow regardless of the vehicle’s size or height.
Another problem with floor-mounted chargers is is that foreign objects or pets can get in the way. The IISB researchers find that cats enjoy curling up on the slightly warm ground-mounted charging station. Metallic paper such as chewing-gum wrappers can blow under the car and into the induction zone, where it can get so hot that it bursts into flame. IISB’s front-end charger eliminates these issues.
“We’ve been consistently upping the system’s performance over the past year, and are now in possession of a prototype that is able to transmit three kilowatts at an overall efficiency of 95 percent,” says Dr Eckardt. “Today’s electric car models can be recharged overnight.”