Inductive charging - pretty smart

The electric Smart whirrs its way to the parking bay. It is the little EQ Forwto, which actually has to be plugged in every 100 kilometers. But not this model. It no longer needs a plug at all, because it can be charged inductively. The white Smart EQ is a test vehicle from the Stuttgart-based automotive supplier Mahle, which is using it to demonstrate its inductive charging system. It works surprisingly simply.

"If it fits in a Smart, then it fits in any car," says Arnd Franz, Managing Director of Mahle. Inductive charging works contactlessly. A plate on the asphalt of the parking lot sends the energy via electromagnetic waves to a receiver in the vehicle floor. There is no need to fiddle around with the charging plug. However, the car must be parked exactly one centimeter above the transmitter.

The problem: as the car approaches the base plate, it is covered by the short hood of the Smart. This is where the positioning system comes in. A Mahle invention that was recently elevated to world standard by the Society of Automotive Engineers (SAE). "We have set the standard here. This will be a strong impetus for electromobility," says Franz. Condition for the SAE decision: Mahle must make the technology available to every manufacturer - in return for a license fee, which is low, however, promises Franz.

The system uses the ground coil as a kind of direction finder. An arrow on the navigation screen indicates where the driver should steer. This works perfectly with the small Smart. Once the car is in the right place, which it does straight away, a stop signal indicates that the maneuver has been successful. Now 11 kilowatts of electricity flows into the battery of the small Smart. Later, a charging capacity of 22 kW will also be possible.

The ground coil is supplied by Siemens and the induction technology by US company Witricity. The positioning software with transmitter and receiver, the DIPS (Differential Inductive Positioning System), comes from Mahle. It automatically establishes a connection with the controlled charging point when the vehicle approaches the charging point.

The system is designed in such a way that even high-legged SUVs and off-road vehicles with high ground clearance can be charged. Safety is a top priority: The radiation is harmless to humans and animals. And if a cat makes itself comfortable on the coil, the current transmission is stopped. Leaves or snow on the base plate are also no problem.

In addition to public charging points, for example in parking garages or in front of shopping centers, Mahle is also targeting the private garages of e-car owners. Vehicles with automated driving functions can also navigate to the charging point independently. The system makes double sense for cars that drive themselves into the garage at home when the driver has already got out. This is because the autonomous parking assistant can also take over the charging of the electric car. BMW and Mercedes already offer such parking assistants.

The little Smart isn't there yet. It continues to charge and has already gained a few kilometers of range. The efficiency of the system is 92 percent. That's how much of the energy used ends up in the battery. Transmission by cable is not much more efficient. Mahle promises that only 1.5 percent of the charging power is lost through wireless transmission. The system is said to be no more expensive than a high-quality wallbox. And in public spaces, inductive charging points have another advantage over conventional charging stations: constant use means that the charging plugs wear out and have to be replaced regularly. As there are no moving parts, there is also no wear and tear.

Vehicles with inductive charging technology are set to come onto the market in three years' time. Arnd Franz will not reveal who the first manufacturer will be. However, there is interest not only in Germany, but also in Asia. This would remove one obstacle to e-mobility, namely having to handle the charging plug. What could be more obvious than thinking about the next step, dynamic charging: Couldn't electric vehicles also "refuel" with energy while driving using induction coils in the road? The TU Braunschweig is actually working on such a system. The car manufacturer Stellantis already has a test track with charging coils in the road that transmit electricity while driving. However, series production is still a long way off. (aum)