New standards and better technology are improving wireless EV charging

The nation's electric vehicle charging infrastructure is nowhere near built out, but wireless charging, the technology that could someday make today's plug-in chargers obsolete, is edging closer to commercial viability.

The speed, power density and efficiency of wireless charging is increasing at the same time engineers are finding ways to reduce weight. And in August, automakers and suppliers established standards aimed at making wireless charging work uniformly, regardless of vehicle brand or charging equipment manufacturer.

Automakers including Tesla, Stellantis, Hyundai and Volkswagen are interested in giving their EV customers the option of cutting the charging cord. Wireless charging won't eliminate the plug — at least not right away — but it would give drivers the option of simply parking over a mat to charge their vehicle's battery pack.

Here are the latest developments.

SAE International Standard J2954 finalizes a method of ensuring that the pad on the ground will work with the receiving pad on the vehicle — regardless of manufacturer — and that the vehicle is aligned properly over the pad for efficient charging.

The alignment component, experts say, could someday be used by autonomous vehicles to self-park accurately over charging pads. Correct alignment of the transmitting and receiving pads maximizes efficiency.

"The standard specifies the hardware used in a performance test for the charging coils up to 11 kilowatts. It also gives information for the control system, which could be used for software for charging," Jesse Schneider, chair of the J2954 committee, told Automotive News.

In developing the standard, SAE engineers worked with wireless charging companies, electronics manufacturers who make charging equipment and automakers. SAE said the new standard provides the "missing link" that is preventing commercialization of wireless charging.

The J2954 standard, covering software and hardware, is based on technology developed by German supplier Mahle. The company's Differential Inductive Positioning System uses a low-intensity magnetic field generated from coils in the ground charging pad that is picked up by coils in the charging equipment on the vehicle. The system carries out a test to ensure the vehicle is aligned. SAE's Wireless Power Transfer team said the standard has demonstrated wireless charging up to 11 kW with 93 percent efficiency.

SAE's lab and field tests also show the system works in snowy and wet conditions.

The SAE standard is "a great thing for the industry. It should accelerate, in our opinion, the adoption of wireless charging. On the plug-in side, they are still struggling with the lack of a standard," said Pamposh Zutshi, vice president of product at wireless charging manufacturer WiTricity.

Researchers at Oakridge National Laboratory in Tennessee have been working to perfect commercially viable high-speed wireless chargers that can dramatically reduce charging times.

Most commercially available light-duty vehicle chargers range from 12 kW to about 20 kW. The lab's goal is to develop wireless technology that delivers 250 to 300 kW of power and reduces charging times to about 15 minutes for about a 90 percent charge.

Earlier this summer, lab engineers and researchers, in a project with Volkswagen, demonstrated a lightweight wireless charger in a Porsche Taycan that set a power density record. Developed over three years, the lab's polyphase charger delivered 270 kW of power.

Most wireless chargers employ a single-phase system that uses a single coil, which cycles from peak to zero and back again. But the polyphase system rotates three pulsating fields and delivers constant power.

Omer Onar, who runs the lab's vehicle electronics power group, said the polyphase charger works on all EV batteries regardless of chemistry. What could limit charging speed, he said, is the batteries' ability to take that much power safely.

Even though the system can transfer power at more than 10 times the rate of most wireless chargers, it doesn't add much weight to the vehicle. That's because of the way the copper is wound in the receiving coils, Onar said.

"It uses the same amount of copper in existing systems. The geometry of the winding is inspired by the way it is done in electric motors," he said.

Because of the large amount of current required to charge wirelessly at 270 kW, Onar said he believes commercial applications of power-dense, superfast wireless chargers will come first. But he said the polyphase layout can be scaled down for home chargers and still deliver about four times more power density than single-phase wireless chargers.

No EVs come from the factory with built-in wireless charging for battery packs. But in-vehicle wireless charging has proven popular for cell phones, and it may be paving the way for wireless EV battery pack charging.

Tesla has already outfitted the Cybertruck with some of the electrical fittings that could be used to integrate a wireless battery pack charger. Hyundai this summer completed wireless charging tests in Korea and is expected to eventually offer it in its growing line of EVs. Hyundai used technology licensed from WiTricity.

The Watertown, Mass., company holds wireless charging patents, and is just launching its fourth generation of wireless chargers. The company sees the path to commercializing the technology starting with the captive fleets that are converting to EV from ICE.

"We are working with a large number of fleets and we have deployed the first units," Zutshi of WiTricity said. "Return-to-depot fleets are an excellent use case for wireless. It's touchless." He said school buses, because they sit idle most of the day, are a natural fit for wireless charging.

Zutshi said implementing the SAE standard requires just minor hardware and software updates to the ground and vehicle wireless charging equipment.

Home wireless chargers and public chargers, Zutshi said, would come after commercial applications.

"Whenever there is a technology transition, you have the old technology. Then you have an overlap period with the old and the new," Zutshi said. "And then, eventually, the new takes over from the old. That's kind of the standard new technology introduction curve. So there will be a time there will be both, and then there won't be a need for a plug."