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Oct 23, 2024

Inside The Technology Behind Wireless EV Charging

Wireless charging is as easy as driving over a pad and parking. As we progress with electric vehicle technology, charging convenience is of top importance among prospective buyers. While it hasn’t

Wireless charging is as easy as driving over a pad and parking.

As we progress with electric vehicle technology, charging convenience is of top importance among prospective buyers. While it hasn’t quite matched the ease of taking a few minutes at the pump to fill up, DC fast charging has gotten us pretty close. Then, it certainly helps that at-home Level 2 charging is becoming more commonplace, too.

But convenience is more than just speed. Having the ability to go about one’s day with as little interaction with a cable as possible is important to those in the market for the kilowatt-powered life, at least according to Boston-based wireless charging company, WiTricity. This operation’s been in the game since 2007, though primarily focused on automotive applications since 2010. That’s well before many consumers ever considered EVs to be a viable form of everyday transportation.

I recently had the opportunity to chat with WiTricity and other industry members about how this technology works, as well as get a solid idea of how exactly it could benefit consumers. According to some experts, we may be on the verge of mass adoption.

A diagram outlining the path of wireless charging.

WiTricity’s current product is what it calls its fourth-generation system, and outlines convenience, enhanced vehicle-to-grid (V2G) functionality and autonomy as its three main focuses, and in that order of importance. But before diving into what each of those mean, let’s discuss how it works.

First and foremost, the system is simple and is classified as magnetic resonance: There’s a wall box that can connect to any type of power input, whether it’s commercial, three-phase, single-phase, etc. That connects to a pad—the charger—which is weatherproof and built to the Society of Automotive Engineers’ (SAE) J2954 Standard. This covers wireless power transfer (WPT) for passenger vehicles (including pickup trucks), and light commercial.

The SAE pointed out to me in an email that a lot has gone into creating this standard. In fact, 394 members comprise its Wireless Power Transfer Task Force, which is responsible for not only J2954, but also J2954/2, the heavy duty WPT standard up to 500 kW. Besides the SAE, stakeholders include nearly every major automaker, the International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), large-scale suppliers like Denso and wireless charging startups like InductEV, WAVE, WiPowerOne, ZEV Station, Electreon, Magment and WiTricity.

WiTricity's display at the 2023 Los Angeles Auto Show.

The method of transmitting energy between the pad and receiver per the SAE J2954 standard is fascinating.

“Let’s say you’ve got 240-volt wiring in your home at 60 hertz AC,” Alex Gruzen, former CEO of WiTricity explained to me when I first learned of this technology a few months back. “That connects to our wall box, which takes it and turns it into DC, and then it turns it back into AC again, but at 85 kilohertz.”

He then continued on explaining the fascinating path that electricity takes. “So now we’re feeding AC to what’s called a coil resonator [in the ground assembly], which is turning that AC charge into a magnetic field around the coil, and is oscillating at 85 kilohertz. A receiver that’s matched and tuned to it, which is a smaller coil on the car, can start capturing that energy. As energy flows from the ground coil and is captured in the receiver coil, it’s then turned into DC [onboard the vehicle].” The DC converted power goes directly to the battery system, too, rather than back through the vehicle’s conventional charging system.

Regardless of air gap (eight inches is considered standard), from coil to coil is 98-99%. If there’s a larger air gap, such as on a higher-sitting SUV, truck, or commercial vehicle, all it takes is a larger receiver with more surface area to capture the same amount of energy. Not only that, but overall efficiency from the grid to the vehicle is around 90 percent; this is because the air gap effectively acts as a transformer, therefore skipping a conventional form of isolation that plugging in requires to avoid damage on either end.

According to the SAE, all of this aligns with the J2954.

WiTricity had a Ford Mustang Mach-E on display receiving WPT at last year’s Los Angeles Auto Show, which is what initially drew my attention towards all of this. “Our job was to figure out how to install this technology without [manufacturer] support,” Christian Dommell, Product Manager at engineering firm Motivo said during an in-person interview. WiTricity enlisted this Southern California-based operation’s help in coming up with an air-tight proof-of-concept. “OEMs want to know that the technology is ready to go, it’s mature, and then understand the costs.” WiTricity introduced a pilot program to present its technology to automakers—as in, get a car and work with Motivo to make it ready for demo purposes—to then help automakers determine if they want to scale it for regular production. WiTricity’s end goal here is to produce units itself, rather than license it out, and production is already up and running. But so far, there haven’t been any major announcements of automakers including it as part of its options and accessories.

Golf carts and other smaller electric vehicles are the perfect candidates for early adoption ... [+] wireless charging.

With that in mind, there are many areas across the wide spectrum of mobility, outside of passenger vehicles, where wireless charging adoption makes a lot of sense. Ready your Caddyshack references: Golf carts are the perfect candidate for wirelessly juicing up.

WiTricity find this to be a great place to grow. “We have the full product ready for those automakers, what do we do with it in the time between now and mass market launches?” a representative told me. It certainly makes sense: mass-adoption of EVs in this sphere is already well underway and easy to integrate.

Scaling up from golf carts, wireless charging benefits a wide range of consumers, including persons with disabilities in passenger vehicles, as it completely cuts out the activity of handling cumbersome cables.

Then, there’s wireless charging’s impact on fleet operations, like intra-urban delivery services, port operations, and beyond. It’s all about streamlining logistics. “Large pedestals and cumbersome cables can make it difficult for fleet operators to deploy and maintain plug-in chargers at scale,” said Joe Benz, current WiTricity CEO. “Free of moving parts with a near zero footprint, our systems are easier to deploy and maintain. Wireless will enable fleets to go electric in ways legacy plug-in charging cannot.” Finally, another useful application is autonomous vehicles: As that technology progresses, giving them the ability to simply drive to a pad and park bolsters self-sustainment and increases their viability in everyday use.

WiTricity's been all over the world.

“I drive it, I park it, I drive it, I park it—it’s like having a car with infinite range,” a WiTricity representative told me. “You just never have to think about charging.” This sentiment isn’t quite a full-on reality at the moment, at least outside of an owner’s residence. However, if adoption increases at a mass scale, going about one’s daily errands could net an increase in charge with no thought at all.

“When we show them wireless charging—the experience—their purchase intent for their next car to be an EV soars. What if instead of throwing several-thousand-dollar checks at customers to get them to buy an EV, why don’t we actually build something they really want?”

Not only that, but the company believes that if automakers offer this technology, it gives them a clear competitive advantage over those who don’t. Think: The hype surrounding Tesla’s wireless charging news.

Fleet applications are endless.

Another incentive that WiTricity has in mind for its wireless charging technology is similar to anyone with solar panels on their homes’ roofs: Sending power back with vehicle-to-grid (VTG). There’s potential to flow vehicles’ stored energy back into the grid, or simply offset demand, to alleviate strain at peak hours.

Taking it as easy on America’s (and other nations’) grids will become a real challenge. V2G could reduce such stress, but also join in the fight to reduce wasted renewable energy sources. Vehicles could stock up with energy produced during peak production—such as during the day—and provide it for when it's either reduced or not producing any at all—such as during nighttime hours.

It’s also important to note that this concept isn’t new, though, as GM Ultium-based vehicles, Rivian, and others have plans for it on the plugged-in front. It’s also been in the news quite a bit lately as it may be required by law in California and other states.

Wireless charging takes on a European flavor.

As pointed out by the companies I talked to, one of the hurdles to making WPT an everyday form of charging was getting automakers on board—it takes a lot of time. Though, there’s more to it than that.

“WPT’s alignment among companies hasn’t been standardized and the path towards mass production has been unclear,” Jesse Schneider of CEO & CTO of ZEV Station, another company in the wireless game, pointed out to me via email. Scheider also chairs the SAE’s Wireless Power Transfer Task Force. “That is all about to change for light duty vehicles.” While the accepted charging level of 11kW has been around for a while now, he means standardization across the entire board, including public charging infrastructure.

According to a report published by the SAE this past Spring, “Wireless Power Transfer (WPT) is set to become an alternative to conductive charging and promises highly efficient charging of electric and plug-in-hybrid vehicles based on the previous publications of the SAE J2954 standards. However, a single common methodology for alignment of the Vehicle Assembly (VA) to the Ground Assembly (GA) for wireless charging public infrastructure was not included in the first two versions of the SAE J2954 standard.”

That’s right, outlining the proper methodology on how to line-up over the pad in a public charging scenario. Which is not only a testament to the potential inconveniences that may arise from WPT, but also the lengths that SAE members have gone to in minimizing them as well.

If there’s one thing I took away from my time talking with WiTricity, ZEV Station, the SAE and Motivo, it’s that the future of wireless charging has the potential to not only make electric vehicle operation far more convenient, but also alter our interpretation of range. Then, to go one further, re-shape our definition of the power grid.

It’s important to point out that wireless charging isn’t intended as a replacement or competitor to plugging in, just a way to expand the ecosystem and increase convenience. And, alleviate any potential strife at the plug, of course. The discussion surrounding plug standardization is still as crucial as ever.

Based on the research I was given and questions I had answered, as well as the exhaustive list of companies and organizations on board to make WPT a thing, the future is bright for integrating EV ownership more and more into the mainstream.

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