Wireless charging for your coffee maker

by Leland Teschler, Executive Editor, @DW_LeeTeschler

Today’s average teenager has never seen a dial telephone. It looks as though cords that plug into ac outlets will soon look just as strange to high schoolers. That’s because wireless charging may become ubiquitous enough to make ac power cords obsolete for most kinds of electrical equipment rather than just being a novelty for personal electronics.

“Eventually your kitchen appliances sitting on the countertop won’t have cords. The idea of plugging your blender into the wall will seem silly. Ditto for construction workers and wireless tools. In EVs, wireless charging will be like cup holders.—you won’t be able to sell vehicles without it.”

So said Argonne National Laboratory Principal Electrical Engineer Theodore Bohn. He came to this conclusion from his work in Argonne’s Transportation Technology R&D Center. There he tests vehicular wireless charging systems to see if equipment from different manufacturers will work with each other.

Interestingly, Bohn thinks wireless charging will become common in EVs long before it starts to pervade the rest of society. The reason is that the Society of Automotive Engineers is hammering out standards for wireless EV charging. But no standards govern the wireless charging schemes now available for consumer electronics. That make the whole field a little like the Wild West; there are several different technologies used. Some employ inductive techniques, others use magnetic coupling, still others depend on resonant circuits. There is no interoperability among any of them. Moreover, Apple, the 800-lb gorilla of consumer electronics, has chosen not to adopt any of the techniques proposed so far. “Apple doesn’t use any of them and wants to do its own thing,” said Bohn.

Meanwhile, Bohn thinks the SAE standard for wireless vehicular charging could be ready by the end of 2016. But there is still a lot of work to do. “Interoperability is the biggest technical challenge,” he said. “Each company has its own IP that it tries to advocate. For example, Qualcomm has a double-D-shaped coil, other suppliers have configurations that look like solenoids, and still others want the pick-up coil to be flat and circular.”

And there is a lot of variability in the performance of the systems Bohn is testing. “Some of these designs work well when they are aligned, but are miserable when misaligned by even a few centimeters. Of course, it’s difficult to park a 20-ft vehicle to a spot within centimeters. Even some vehicle navigation systems can’t self-park cars to that accuracy. The throughput for some wireless charging systems really falls off quickly with any misalignment because they are highly tuned,” Bohn explained.

One factor slowing the process is that manufacturers can’t decide on parameters in a reference design that all systems must interact with. “The standard must require a certain amount of efficiency and throughput under set conditions. For example, if you exit the vehicle and its height rises by 30 mm, you want it to still charge acceptably. Or there might be snow melting and the parked vehicle gets 30 mm closer to the charging pad. These things really happen—people park poorly and on top of debris. They are issues the committee is working through,” Bohn said.

All this makes it time consuming to come up with specs that will be bullet proof in the real world. But SAE standards will be the reason cars will have wireless charging long before coffee makers or food processors do.