Off topic : e-cars : Is there a possibility to charge their batteries wireless?

Would be a big improvement and give the whole charging process much more flexibility and mobility.
Its possible with phones we all know, so why not with such cars!
But what about effectiveness?

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There are a few companies looking to wirelessly charge cars, they have a pad or mat that stays on the ground and you just drive your car over it to charge. There is also a company looking into investing so cars could charge while driving.

The speed and efficiency are so much lower that you probably couldn’t get a full charge overnight. At least with current technology. That may change in the future, but for now it would be too slow.

Ironically yes.

A car is necessarily wide and low. So their shape naturally suits wireless. You could park them over a wireless area which is narrow and so most of the energy gets into a relatively wider vehicle.

It would still be less efficient than wired due to eddy currents inherent in all magnetic induction.

Once room temperature superconducting happens then the eddy currents don’t happen with heat.

So yes, eventually.


Electrons deliver more energy than photons so wired will always be more efficient than wireless for this universe for all time. Sorry. I didn’t invent the universe.

I can see a hybrid of you drive over, or park, wireless areas where you get a top-up to complement wired. I can see where top-up is enough for short-mileage users they get by purely on wireless.

Vehicles also can use the fact they move. A changing electric field makes a changing magnetic field which makes a changing electric field. So for static motion items like phones on pads, the electric field has to be made alternating, high frequency. But for a moving vehicle you can use DC as the vehicle moving over DC will create a changing electric field. So I can imagine top-up sections of road, as you drive over you get a little recharge.

I’d like for them to focus on range before they come out with wireless chargers for cars. I’m not an electric car owner but I’d prefer to have longer range than what’s currently offered


For small countries and in cities the range of todays batteries could be sufficient.
But I always consider : here in München > 1,3 millions inhabitants
I like to use public service.
Efficient, no problems with parking and so relaxing even in Covid-times
(mask only and distance).
No car is needed! :smiley:

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Range at high speed would naturally increase with self driving as you get in the slipstream of the vehicle in front and the cars ahead send braking signals if there’s an issue. Each vehicle then has less drag.

So technology will give advantages where someone has no viable alternative (public transport etc)

I don’t think wireless charging for cars is a bad idea, but I think they need to improve other things before they start worrying about wireless charging

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In a crowded market even “toy” features get added to differentiate. There will be a moment when vehicle wireless charging will be an option, and the geek buyer at that time will justify to themselves to buy that option.

You can use in-road induction fields to transfer energy to a moving vehicle, but you can also reverse polarity where they act as a brake, so you can use them slow a vehicle approaching a junction. and impart energy stored to use to accelerate out the other side of the junction.

Wider topic is vehicles are going to die as resources get constrained. Cities are more efficient places for people , so costs are higher outside of cities so only the rich are rural. In cities you are not far physically from everything you need, so walk / bike / public-transport. So the idea of vehicles will naturally die away anyway.

There will be a moment when those who lived in a place where they needed a gasoline vehicle, will move to electric vehicle, because largely they are forced to by environmental laws (similar to green air, and clean water acts in 19th and 20th century), who then are squeezed out of their vehicles by the much better of that energy to drive more productive things than moving a human. During that future story I can see wireless happening, in roads and offices, parking lots, etc.

Eventually yes, but the technology has to improve a lot before that is really feasible. Phone wireless chargers are only about 50-60% efficiency compared to wired chargers, which would mean the time to charge would increase significantly. Couple that with the fact that cars have large batteries to charge (>60KW), which makes even wired charging long it would take a lot of energy and a lot of time to deliver a meaningful wireless charge.

Someone double-check my math…

Assuming today’s technology begins at


100KWh vehicle batteries, with 400 miles range.

Assume 60% efficiency, you need to push in 100 / 0.6 = 167KWh energy

Assuming 8 hours recharge mean you need 167/8 = 20KW power input.

Assuming 240V , 20,000/240= 87A. That’s a highly lethal current so no surprise a thick current Tesla connector.

Current wireless technology from a small plate about 3cmx3cm gives about 40W, (Android phones e.g. Huawei, OnePlus) so scale that up to say 1mx1m means (100/3 squared) 1100 more, 44KW. Arguably I should use 27W wireless not 40W so then I get 1100x27 = 30KW.

Above is 20KW for an overnight example, and 30KW > 20KW so I’ve just demonstrated theoretically, scaling up wireless to a 1 meter square underneath vehicle you can recharge an electric vehicle wirelessly overnight.

So yes you can do it now using the underneath of vehicle with a huge set of induction rings.

You’d have engineering challenges, heat being the major one and the energy lost would be very wasteful, but you could work on them over time - if you didn’t use for the full recharge but just a top-up, say a wireless pad a car lot outside restaurant, make use of an hour without plugging in.

I agree it is a long way off being viable, probably never competitive for overnight recharging as you’re wasting a lot energy as heat, but earlier is viable top-up making use of times when not on a long static wired recharge.

Not too dissimilar to how many consumers use wireless phone recharging, they don’t intend to charge from empty to full fast, they tend to use to top-up through the day and often accept slow overnight charging as the waste is a few $/year.

Huge waste relative to a cyclist, who a fit one is making 100W, and averages 20mph at 100W, 400 miles is thus 20 hours cycling and consumes about 5000Kcals/day or about 15000KCals or 17Kwh, a lot less than the 100KWh of the vehicle.

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I think it is very much so possible but I think until the demand of people buying electric cars increases or they find ways to make it more energy efficient it won’t be happening soon.

The math seems reasonable except for the power of the 3x3 wireless charger. Anker’s delivers 10w while consuming about 18w. The other issue is the size of the induction field, scaling a 5mm field to 12-14 inches would require very significant power. Unless the charging pad could move up closer to the bottom of the vehicle to reduce that distance.

Exciting prospect though. When we reach it we won’t be far(less than a decade) from having highways that charge your vehicle wirelessly while you drive, so you can just drive forever :wink:

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So we’re inventing it here.

Induction of stationary vehicle requires AC which is how Qi works. You’d not have one big ring but many small, and you can spread them apart, so long as 1 square meter underneath the vehicle, then viable. An accelerating electron (circling) has higher acceleration in smaller circles, so more smaller is more efficient than one big (theoretically).

Induction of a moving vehicle for “drive’n’charge” is DC.

On-ramps to freeways can be charged by off-ramps from freeways.

I do think KISS will kick in, wired is simpler, and ultimately vehicles are not sustainable, why move a whole vehicle just to move a person’s weight when better the person doesn’t move and you move the goods they consume. I see cities growing and emphasis on mass transit of goods to cities and the people move themselves using their legs. Vehicles thus only are local to a city, do a few miles, and then can be charged locally with things like wireless.

As a test, I attempted to stop using cars 18 years ago. So far this last 12 months I think I’ve driven twice. Cities like New York, while not perfect, do hint at how most will live, mostly walking, for longer trips walking to the public transport locations.

However I have also trips like this, 9000 miles:


For which right now nothing but gasoline vehicle would do.

So I see what’s possible and the challenges ahead.

Definitely I think that urban transit will evolve beyond single individual vehicle. Ford also sees it, which is why they’ve already branched into areas like shared e-scooters or medium density self driving e-shuttles. Excitingly for this forum, it does seem like batteries will play an important role in shaping that future.

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I see it here in München.
They reduced the electric tramways in the 1980/90.
But now they are creating new tracks.
Very good.

The parking space is extremely limited and everyone here got a car.

That means, a family (parents and two elder kids) got four cars, but they are living in a small apartment.
The bigger the car the better . The best is a SUV!

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Here’s something related from a few years ago:

Induction charging strips on roads, Wipeout style!

Obviously there would be a few challenges implementing induction charging on motorways/highways but I can definitely see something like this taking off in the not-too distant future. Potentially going cross country without having to use a recharging/refuelling station sounds great!

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Well imagine if:

  1. the on-ramp accelerated you to speed using not induction to your motor but the metal of the vehicle.

Accelerate like:

4m28s shows a car moving.

Because the energy of acceleration and the motor is external you don’t consume battery not engine from within the car.

  1. mesh network of self driving vehicles who then get really close to each other so each vehicle has almost no wind resistance, you’d get the same fuel efficiency at 125mph as at 10mph.

Like this but much faster

  1. the off-ramp the opposite of 1) where the car is decelerated and the energy dumped into the road is powering the on-ramp.

You’d then have a high speed very efficient door to door system. The vehicle does not need as large a battery nor engine as the freeway does most of where the efficiency comes from and at the smaller slower non-freeway roses you use the engine and battery. The speed would then mean you could commute further, say 100 miles/day with times less than an hour and days between recharges.

Just vote for me as Planet President and I’ll get all the scientists onto it and non of this wasting time on other things.

Self driving vehicles will further reduce energy requirements as you can neatly line up vehicles behind each other reducing drag, optimize acceleration/deceleration, use V2V communication to know how traffic is up the road or around the bend. Not there yet, but things are moving in that direction.

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