Wireless Charging On A Massive Scale

Despite the increasing popularity of various electric vehicles, the limits of battery technology continue to be a bottleneck in their day-to-day use. They don’t behave well in extreme temperatures, they can wear out quickly, and, perhaps most obviously, charging them is often burdensome. Larger batteries take longer to charge, and this can take a lot of time and space, but this research team from Chalmers University are looking to make this process just a little bit easier.

The group has been developing an inductive wireless charging method for large vehicles including cars, trucks, busses, and ferries that can deliver 500 kW across a 15 cm (6 inch) air gap. The system relies on a silicon carbide semiconductor and extremely thin copper wire in order to make all this happen, and eliminates the need for any human involvement in the charging process. This might not be too much of a hassle for plugging in an electric car, but for larger vehicles like busses and ferries traditional charging methods often require a robot arm or human to attach the charging cables.

While this technology won’t decrease the amount of time it takes batteries to charge, it will improve the usability of devices like these. Even for cars, this could mean simply pulling into a parking space and getting the car’s battery topped off automatically. For all the talk about charging times of batteries, there is another problem looming which is that plenty of charging methods are proprietary as well. This charger attempts to develop an open-source standard instead.

Thanks to [Ben] for the tip!

26 thoughts on “Wireless Charging On A Massive Scale

    1. It’s half a foot. That’s enough that you could park over a spot and the coil could get raised up without too much precision in Z.

      I’m not saying it’s perfect, but there will never be a magic solution. We’ll just see more and more engineering developments like this over time, and then one day there will be a solution that’s good enough, and we will start to see early real-world adoption and more momentum in development, just like with EVs themselves.

        1. So it took a good hundred years (for the purpose of EVs) to advance from “entirely suck” to just “suck”? When it eventually gets to “doesn’t suck” I’ll think about trading in my internal combustion-powered car.

          1. Well, technically about 164 years since the lead-acid battery was invented in 1859.

            But more precisely, the span of “entirely sucks” spanned from 1881 from the first EV to use said batteries to 1996 when Nissan put the first lithium batteries into a prototype EV, which is 115 years. Then it took another 25 years for the cost to come down enough that I could technically buy a small EV with a battery that still sucks.

            So, not holding my breath yet. The race is on, which comes first: working nuclear fusion or the affordable practical electric vehicle?

          2. Some good signs that may be sooner than later. The Lightyear is coming out soon, manufacturer states that the built in solar panel will provide enough charge to the average driver that you’ll only need to plug in once every 6 months.

            Other battery advances are rather exciting as well, including a fluid charge medium (proper terminology escapes me currently) that you would exchange at a filling station instead of recharging, with similar energy densities to gasoline, once efficiency is taken into account, old fluid returning to the factory to recycle/regenerate. Combine the two, you have a 5 minute stop at the energy station every 6 months, or the typical 5 minute stop every few hours on a long roadtrip, exactly the same way you treat your current ICE on a roadtrip.

            That tech is still early, of course.

          3. Lightyear went bankrupt a couple months ago friend. It was always a bad idea, theres just not enough flux coming off the sun to charge a car like that. Good aerodynamics though

  1. 98% efficiency at 500 kW still means there’s 10 kW of power leaking out somewhere. Hopefully not into EMI.

    >The system relies on a silicon carbide semiconductor and extremely thin copper wire

    They mean Litz wire, which is used to combat skin and proximity effects which occur when you try to put high frequency AC through an inductor.


  2. I admire the ingenuity, but have to wonder if it’s a bit too complex to be practical. Trying to make a transformer with a 6″ air gap seems unnecessary, less efficient, and likely to have EMI problems.

    Way back in the 1970’s, the company I worked for had hundreds of in-plant electric vehicles that all used wireless charging, made by a company called Inductran. Basically, it was a big 60 Hz transformer that had been cut in two, with half of it in the floor and the other half in the vehicle. The vehicle was driven over the charging spot, where a raised “curb” contained the lower half of the transformer. When the vehicle was parked over it, its half of the transformer mated with the one in the floor. Simple, reliable, and efficient (coupling efficiency was over 98%, basically the same as any big transformer).

    Later I worked for a company that developed General Motor’s MagneCharge charging system. It was the same basic idea, but using a high frequency switchmode transformer. It used a “paddle” on a cable with the primary of the transformer, that fit into a slot in the car with the secondary. But the primary could just as well have been floor-mounted to mate with the car-mounted secondary.

    1. That sounds like a much better idea; this could also be done with a HF transformer, with half of the ferrite core in the vehicle, and the other half coming out of the ground, pushed up by a spring-loaded (compliant) mechanism. The spring takes care of the Z axis, and if the cores are relatively large, some misalignment shouldn’t really be an issue either, as long as there is sufficient overlap between the cores. Alignment could be improved by providing the driver with some assistance while parking.

      I really don’t see why you would want to bridge a 15cm gap. 2% of 500kW is still a significant amount of power lost.

      The efficiency is impressive though.

  3. Rather than do this, how about looking at how Disney recharges the cars in Luigi’s rollickin roadsters at the California Adventure. The car to be charged (they switch depending on the battery conditions) parks in a specific spot on the open area where a plate with terminals is located. When it parks this plate comes up and makes contact with the terminals on the bottom of the car. Power is delivered DIRECTLY and not requiring the inductive process or the losses inherent in the transfer. I’m not saying to do a dynamic charging system, but build one that does not rely on inductive charging.

    Cars that would have the technology would deploy some kind of alignment key and lock in for charging.

    Electric cars need to resolve issues. Too much of their implementation is based on the “We’ll figure out how to do that later.” Recycling and disposal are the biggest hurdles because many that think like me won’t touch that technology until they show me it’s not going to be a bigger headache than what we deal with today.

  4. I might butcher this so sorry they mention the frequencies being approximately 4x higher than current wireless charging systems which puts them around 80khz. that is fine and all but what they do not mention is at how many db @ spl which most countries around the world have laws against going over specific levels. So until they release that spec to even see if the technology would be legal to use it is really a moot discussion.

  5. Yeah proprietary charting standards are going to be a nightmare, just look at the state of messaging on the internet for example.

    Induction charging probably isn’t worth the hassle over direct connections with current configurations, but it could enable a different model, where charging is built into the infrastruture.

    If all stop lights, parking spots, or just slower sections of road etc had induction chargers built in, we could make cars with much smaller batteries, since they would be getting small topups regularly.

    1. The irony of wireless charging is that the spools of wire used for the transmission coils contain enough wire to pull an extension cord to where you’re going. Literally kilometers of wire.

  6. What do you mean with those “robotic arms”
    I kinda wonder how it’s going with the Yara Birkland. I guess that needs some kind of large boom for charging, and those last 15 cm are then also not going to matter much.

  7. The way I’ve seen wireless charging justified in these cases, given the coupling is not perfect, is that you are just as efficient once you consider you don’t need to spend a couple percent on your galvanic isolation transformer. However, it does seem like even with near field effects, big coils at small relative distances, etc, you’re talking about making the low to medium frequency RF ranges completely unusable, just to avoid plugging in a physical cable. And it will only work when the ev itself is able to put a coil right near the charging location while keeping anything conductive far enough away not to see big induced currents. A human won’t really feel the effects at these low frequencies if they’re not touching big pieces of metal, although it’s surely outside of typically allowable emission limits. But all your stuff will.

  8. There seems to be a certain infatuation with non contact charging of electric vehicles. People with liquid fueled car don’t seem to have an insurmountable problem with going of the way to get to gas stations and putting a hose into an on-vehicle receptacle to transfer fuel.

    Yes, it does take longer to transfer energy with current electric vehicle technology. The question is, “how much does that matter?” The answer is sometimes. Case 1 is renters and others who do not have access to outdoor electrical outlets where they live, allowing vehicles to be plugged in while parked. Case 2 is long distance driving where stopping for 60 minutes every 300 miles may not be desirable.

    Electric vehicle use is a different paradigm from liquid fueled vehicles in that under most daily use scenarios EVs may be charged a little bit at a slow rate while parked. That is unlike liquid fueled vehicles which are customarily refueled with enough energy for several days or even a week’s worth of travel all at once.

    95% of my own vehicle use is trips with destinations within 15 miles of where I live. I bought a used 2011 Nissan LEAF in 2014. By modern standards, the LEAF had a laughable 80 mile or so useable range. Despite that, I was able to plug the LEAF into a 120 Volt socket, and had no problems with having enough charge for daily use. I switched to a Chevy Bolt in 2017 and the Bolt lets me cover destinations in more than 1/2 state where I live on a single charge. When I return from a trip which uses almost all the charge, it can take more than a day to return to completely full, but that doesn’t prevent using the car around town for short trips as charge gradually accumulates while the car is parked at home. I just use the 12 Amp cord supplied with the Bolt. The cord works on both 120 and 240 Volts, and for the first few years I owned the Bolt, charged it at 120 Volts because I did not have a 240 Volt circuit available. I could probably stay with 120 Volts given my use case, but there is about 5% better energy capture at 240 Volts due to fewer losses in the on-board inverter and the i^2 * R losses in premise wiring taking place over less total time (12 Amps at either voltage).

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