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Audi e-tron 2019: Wireless charging still in the too hard basket

One of the downfalls of owning an EV is remembering to actually plug it in when you're done with it.
Tim Robson
Contributing Journalist
CarsGuide

21 Sep 2018 • 3 min read

Innovative plate-charging system shows promise but not yet ready to be rolled out.

One of the downfalls of owning an EV is remembering to actually plug it in when you're done with it. And if your electric car is out of juice in the morning, it's not the work of a moment to top it up.

Inductive charging is the science of pushing charge into a battery via inductive coils or plates; many mobile phone makers are now equipping batteries with the same system, which then allows the phone to be simply laid on a surface rather than be plugged in.

"An alternating current raised to 85 kHz causes a changing magnetic field in the coil belonging to the inductive charging station," reads an Audi release. "If the car's charging system's second coil is situated inside that magnetic field, a force is exerted on the charged moving particles in the vehicle's copper coil, inducing a voltage. The coil systems have optimally matching resonant frequencies."

Audi has been working on a larger scale system for its EVs, even rolling out a workable prototype last year. Software built into the car's self-parking computer allows the car to locate and park itself over the top of a 90cm x70cm plate, which can sit unsecured on a garage floor and is only 70mm in height.

Once the car is in position, a 60cm by 60cm plate raises to within a centimetre of the battery base and charging can begin. The small gap allows for up to 90 per cent charging efficiency, according to Audi.

Once charging is finished, or if the driver hits the start button, the plate retracts back into the unit.

However, the system was nowhere in evidence at the launch of the e-tron, and Audi's COO of Technical Operations, Ulrich Widmann admits that the program has hit a few hurdles.

"For wireless charging, you have a lot of security aspects, because a lot of people are really afraid that something is between the car and the charging plate," he said at the launch of the e-tron.  "And also, depending on the distance, the efficiency of the power is dependent on the distance of the two plates in the car and on the infrastructure."

What could be between the plate and the car? Pets, for example, or objects mislaid in a garage that may disrupt the charging process. But there is also another issue that's come to light, and that's battery capacity.

"If you have very big battery, you need really a longer time, because all these wireless charging systems are not able to provide high-power charging," Mr Widmann confirmed. "So I think the use case is more that, if you travel short distances, you always then drive the car on this charging infrastructure, but the fill-up is not from empty to full; it's always adding the last percentages."

The Audi e-tron's 95kWh battery, for example, will take more than 10 hours to charge on a domestic 240V Australian plug, or 8.5 hours if the car's charger is wired into a three-phase power socket. Inductive-charging such a large battery from 10 per cent to 80 per cent capacity may take as long as 12 hours.

Mr Widmann is confident, though, that the system will make it into production. "We just will launch in the future for the A8 and then roll out the system throughout our fleet where it's applicable," he confirmed.

Would wireless charging help convince you to go electric? Tell us what you think in the comments below.