3.2kW wireless EV charger, uhhhhhhh

[CopperCone]

Uh just because pumping explosive ass gasoline into a car is unsafe, does not mean that focusing design on direct conduction of electricity into cars is a good idea.. when there is an alternative technology that can be developed.

that's a fallacy. You have a bias for efficiency/cost. The performance of a previous unrelated technology should not be considered in making a decision, it is not rational to do so. It is human life at stake.

Your argument is that it might have a better track record then gasoline (at least in filling, not sure how it is with road way accidents).

And you need to consider what happens when things get super common and you have budget brands, overseas brands, etc. Not just high end teslas.

Enforcing a particular direction might mean shady manufacturers have less effect on safety later. The standard will be intrinsically tighter.

Personally I don't even like interacting with power cords. I prefer to install more outlets so things stay connected. And I modify stuff to have IEC sockets as they are safer. It's just better not to flex conductors and insulators. Cords are like a super weak point in equipment.

Usually you have a heavy metal or plastic body, well insulated or grounded. Then you have a wimpy flexible thing that can put out 4000A peak connected to it. Its just basic to see it as dangerous.

And I prefer a big metal thing I am going inside of is floating rather then ground reference especially if its in a damp garage, incase you forget to unplug it.

[Mr. Scram]

Are we really arguing whether cables can be safe? Literally billions of people use electric cables with deathly voltages every day without even thinking about it and with very few incidents. The potential problems that do exist are engineering problems.

Besides, wireless power isn't magically safe. It has its own complications and safety issues.

[JohnnyMalaria]

And you get to live out your shuttle bay fantasies (sorry if it's large - it needs to be):

[Mr. Scram]

And you get to live out your shuttle bay fantasies (sorry if it's large - it needs to be):

I want a robot arm attaching an umbilical as if it's a rocket ship, damn it!

[amyk]

85% efficiency... so 15% of 3.2kW which is 480W gets wasted as... heat?

[apis]

Google says: "an efficiency rate of around 85%". (3.2kW * 0.15 = 480W losses)
https://www.gizmodo.com.au/2018/05/bmw-launches-worlds-first-wireless-charging-for-electric-cars-groundpad-530e-iperformance/

Like a connected charger doesn't have losses 

I assume 85% refers only to the efficiency of the wireless transfer (under ideal circumstance)? :/

[ajb]

The wireless charger has a substantial benefit with self-driving cars, and that's probably at least 30% of the reason it's being seriously developed.  The car can simply drive itself into a parking space and start charging. 

Of course there's another way to solve that. . .

And you get to live out your shuttle bay fantasies (sorry if it's large - it needs to be):

I want a robot arm attaching an umbilical as if it's a rocket ship, damn it!

. . .which is cool, but still a far less elegant solution than the wireless charging pad.  It requires a whole mechanical arrangement, a whole vision system for alignment, it's bulky and prone to getting driven into, etc.  Whereas the wireless pad needs no moving parts and at most relies on the sensor suite that's already built into the car anyway.

[julianhigginson]

if you're going to have a physical connection capability anyway, then the wireless transfer option seems like a bit of a waste of energy, and money.

surely putting the cable and direct charger electronics you would have anyway onto a guided arm isn't going to cost that much? simple visual feature detection and navigation seems like something even an advanced maker could arrange themselves with a raspberry Pi, openCV,  and some off the shelf stepper motor gear or a robot arm kit.

yeah it's neat to charge wirelessly, but you will need a 3500kW receiver coil and electronics in the car, 3500kW charger coil and electronics in the charger, both of which will cost a fair bit, and after all that it's an extra 0.85 multiplier on your vehicle's entire efficiency.

[DG41WV]

why not use a docking station with physical contacts, like a roomba? maybe put that arm thing inside the wireless charging station.   
https://youtu.be/byQ0CBgjE-0?t=6s

[vk6zgo]

and seriously wtf is this all this laziness talk?? I lift heavy and walk. Why is some health conscious ompa loompas telling me I need even more exercise plugging in fucking cables?? What is that like 0.05 calories burned and minor hand eye coordination (maybe it prevents wasted people from sending shitty texts idk???)

If you are serious about your health you probably periodically go outside and go for walks, lift weights, run.. .wtf is plugging in a cable gonna do? Exercise is like, sweat coming off of you, sore muscles... if anything having to remember to plug in a cable is bad for you, you gotta occupy your mind with remembering to plug in a cable?? Why the unnecessary stress?

why you gonna try to make me touch something connected to mains?

Did you make yourself a cup of coffee the morning?
Toast?

 i don't go around trying to encourage people to beat alligators with broomsticks. wtf

[james_s]

Personally I don't even like interacting with power cords. I prefer to install more outlets so things stay connected. And I modify stuff to have IEC sockets as they are safer. It's just better not to flex conductors and insulators. Cords are like a super weak point in equipment.

You have a very strange hangup concerning electricity, borderline paranoia, especially strange to see on an engineering forum. Most people interact with electrical cords on a daily basis, even completely non-technical people like my mother have managed to do this their entire lives without injury. Electrocution involving properly designed and installed equipment that has not been tampered with is exceedingly rare. When was the last time you actually had one of these "super weak" power cords fail? The only one I can think of that I've encountered was on a 70 year old radio, the conductors were fine but the rubber insulation crumbled.

You are free to go to heroic measures in order to avoid interacting with power cords. Meanwhile the rest of us will keep using them uneventfully.

[vk6zgo]

You will no doubt enjoy the induced RF " bites" you will get from metal objects in your garage.
OK, it's only 3.2kW, but in such close proximity, you will almost certainly get them.

Ohh, & you will love it when the weird neighbour next door who thinks his house wiring & your mobile phone
are giving him cancer hears about it.

He will probably drag in a few of his mates & they will picket your house.

[Kjelt]

Of course there's another way to solve that. . .

. . .which is cool, but still a far less elegant solution than the wireless charging pad.  It requires a whole mechanical arrangement, a whole vision system for alignment, it's bulky and prone to getting driven into, etc.  Whereas the wireless pad needs no moving parts and at most relies on the sensor suite that's already built into the car anyway.

That is supercool but way overengineered IMO.
Ok so lets say we keep the car and charger homing beacon alignment,
The wireless way needs 8cm max space, is it so difficult to raise a connector with autoalignment properties for 8 cm? That is all that is needed another 8cm good electrical connection that could not be so hard.

[nctnico]

Google says: "an efficiency rate of around 85%". (3.2kW * 0.15 = 480W losses)
https://www.gizmodo.com.au/2018/05/bmw-launches-worlds-first-wireless-charging-for-electric-cars-groundpad-530e-iperformance/

Like a connected charger doesn't have losses 

I assume 85% refers only to the efficiency of the wireless transfer (under ideal circumstance)? :/

No. Why would it?
Besides that people should think about transferring 200kW or even more. With those power levels using cables become less easier to handle by people. If you have a way to get rid of a cable + plug it would make charging safer (partly because there is no wear on plugs and cables).

[apis]

Google says: "an efficiency rate of around 85%". (3.2kW * 0.15 = 480W losses)
https://www.gizmodo.com.au/2018/05/bmw-launches-worlds-first-wireless-charging-for-electric-cars-groundpad-530e-iperformance/

Like a connected charger doesn't have losses 

I assume 85% refers only to the efficiency of the wireless transfer (under ideal circumstance)? :/

No. Why would it?
Besides that people should think about transferring 200kW or even more. With those power levels using cables become less easier to handle by people. If you have a way to get rid of a cable + plug it would make charging safer (partly because there is no wear on plugs and cables).

Because wireless power transfer is usually very inefficient (losses in the coils, the switching, radiative losses, etc), and it's marketing fluff so it's going to be exaggerated. On top of that to reach full efficiency you need to have the coils very close and aligned properly.

It's nice in theory (drove Tesla mad) but in the end, even when you have receiver and transmitter touching each other (and what is the point with wireless then?) it's not very efficient.

Those new gimmicky Qi phone chargers are officially* 70-80% efficient and then you have a gap of a few mm. (Don't get why people want them anyway, you can't use the phone while it's charging that way, it's pretty restrictive for being "wireless").

* they don't really give an official figure because "it varies". In reality it is much less:
https://youtu.be/ExU32UyGX6w?t=5m24s
(Spoiler: 40% extra loss compared to a normal usb cable.)

In a future when most vehicles are electric, if they become even 5% less efficient that will have a huge impact on global energy consumption.

[Jeroen3]

Its quite safe if it works. The problem is still that you need to handle a high voltage conductor that can malfunction and it can be cut, insulation can go bad, control systems malfunction, etc.

If it was in a industrial setting they would probably check it with a fucking megger periodically. To do it right you probobly need to disable it with contactors (rather then relying on a software safety to depower a H-bridge or something). This means electromechanical parts, which means ware and tear, inspection requirements, etc.

I have never handled ev-charing cables, but they look like they are reinforced PUR cables. PUR cables are almost indestructible, but expensive. The next best thing is rubber cable, this is also very solid cable, but eventually will get cuts and damages. Rubber cables are used in industrial setting when the cables are temporary. Rubber cables are indeed regularly tested to spec. The insulation is rarely at fault, is it would you could see it with visual inspection, mostly the contact resistance on the plugs fails spec.

PVC cables are toys compared to rubber or PUR.

You don't need a physical disconnect, there are online insulation monitors.

[nctnico]

Google says: "an efficiency rate of around 85%". (3.2kW * 0.15 = 480W losses)
https://www.gizmodo.com.au/2018/05/bmw-launches-worlds-first-wireless-charging-for-electric-cars-groundpad-530e-iperformance/

Like a connected charger doesn't have losses 

I assume 85% refers only to the efficiency of the wireless transfer (under ideal circumstance)? :/

No. Why would it?
Besides that people should think about transferring 200kW or even more. With those power levels using cables become less easier to handle by people. If you have a way to get rid of a cable + plug it would make charging safer (partly because there is no wear on plugs and cables).

Because wireless power transfer is usually very inefficient (losses in the coils, the switching, radiative losses, etc), and it's marketing fluff so it's going to be exaggerated. On top of that to reach full efficiency you need to have the coils very close and aligned properly.

It's nice in theory (drove Tesla mad) but in the end, even when you have receiver and transmitter touching each other (and what is the point with wireless then?) it's not very efficient.

Those new gimmicky Qi phone chargers are officially* 70-80% efficient and then you have a gap of a few mm. (Don't get why people want them anyway, you can't use the phone while it's charging that way, it's pretty restrictive for being "wireless").

Qi is not relevant in this discussion because it uses magnetic coupling which is very inefficient. You can get better efficiencies in real world applications over longer distances by using resonant coupling. Qi is optimised for low power low cost solutions and efficiency doesn't matter. This does not mean wireless power transfer using inductors is inherently inefficient.

[apis]

Qi is not relevant in this discussion because it uses magnetic coupling which is very inefficient. You can get better efficiencies in real world applications over longer distances by using resonant coupling. Qi is optimised for low power low cost solutions and efficiency doesn't matter. This does not mean wireless power transfer using inductors is inherently inefficient.

Do you know of any other real world wireless resonant system in use that someone have tested and published the efficiency of? I believe it when I see it.

But either way, it is always going to be less efficient than copper wire. In a future where everyone drives an electric vehicle, if you make the fuel even 5% less efficient it will have a huge impact on global energy use. And for what? So people doesn't have to spend a few seconds plugging in a cable? :/

[Wolfram]

Qi is not relevant in this discussion because it uses magnetic coupling which is very inefficient. You can get better efficiencies in real world applications over longer distances by using resonant coupling. Qi is optimised for low power low cost solutions and efficiency doesn't matter. This does not mean wireless power transfer using inductors is inherently inefficient.

Do you know of any other real world wireless resonant system in use that someone have tested and published the efficiency of? I believe it when I see it.

But either way, it is always going to be less efficient than copper wire. In a future where everyone drives an electric vehicle, if you make the fuel even 5% less efficient it will have a huge impact on global energy use. And for what? So people doesn't have to spend a few seconds plugging in a cable? :/

Inductive charging can be done at > 90 % efficiency with realistic geometries for EV charging: https://ieeexplore.ieee.org/abstract/document/6953459/ . Foreign object detection is one of the main challenges in this field, the actual power conversion is a solved problem.

For those without IEEE access, the abstract answers the question pretty nicely:

In this paper, the design and hardware realization of a 3.5kW inductive power transfer system to charge electric vehicles is presented. The commercial success of such a wireless charger is highly dependent on the energy conversion efficiency. The presented design consists of a circular receiver coil mounted on a car and a larger circular transmitter coil fixed to the ground. It achieves an efficiency as high as 96.5% from 400 VDC to 400 VDC. This figure includes the necessary power electronics circuits on the transmitter and receiver side and is achieved over an air gap of 110mm between those coils. Even with a lateral misalignment of 100mm between transmitter and receiver and an increased air gap of 160mm the efficiency was determined to be 94.3%. Due to the limited space available on the vehicle the dimensions of the receiver coil are a mere 240×240 mm, which results in a coupling coefficient of less than 10 %. With these results the efficiency is no longer inferior to a wire connected charging system. Instrumental to achieve this performance is a careful optimization of the transmitter and receiver geometry and the proper tuning of the electric part of the circuit. Both aspects are discussed in detail in this paper.

Note that this includes the power conversion electronics. The best conductive (wired) charger DC/DC converters are presently around 97 % efficient, so the difference is small, especially considering that most chargers are between 92 and 94 % efficient, including typical 3.6 kW onboard chargers.

[apis]

Inductive charging can be done at > 90 % efficiency with realistic geometries for EV charging: https://ieeexplore.ieee.org/abstract/document/6953459/ . Foreign object detection is one of the main challenges in this field, the actual power conversion is a solved problem.

For those without IEEE access, they get a measured efficiency of 96.5 % with a coil spacing of 110 mm. The receiver coil is 240 x 240 mm in size.

Impressive if they can take that from the lab to a commercial system that operates at similar efficiency. It's not a verified real world working system though, just because you can get that efficiency in a lab doesn't mean you can mass produce it that efficient economically. Would be interesting to see independent test of that bmw-charger for example.

Even if they succeed with that, it's still 5% losses, compare that to a connector. Would you want to make your car 5% less fuel efficient just so you didn't have to plug in the cord? Unless they manage to get the losses negligible this isn't a good idea imho.

It's a classic example of an over engineered solution to a non existent problem that in reality just makes things worse.

Note that this includes the power conversion electronics. The best conductive (wired) charger DC/DC converters are presently around 97 % efficient, so the difference is small, especially considering that most chargers are between 92 and 94 % efficient, including typical 3.6 kW onboard chargers.

They only mean the electronics involved in the wireless transfer, so compared to a normal connector you have to add the 5% losses from their laboratory prototype to the other charging component losses.

Once you have the power in the car, it's the same whether it was transferred wireless or not. After that you will need the same type of DC/DC converter to charge the batteries.

Ideally you should compare it with a system where you replace the wireless transfer module with a normal connector. It's the extra losses in the wireless transfer compared to a connector that is the problem here.

That there exist crappy chargers just shows that if these wireless chargers become common, in practice they will perform way worse than that.

[nctnico]

Qi is not relevant in this discussion because it uses magnetic coupling which is very inefficient. You can get better efficiencies in real world applications over longer distances by using resonant coupling. Qi is optimised for low power low cost solutions and efficiency doesn't matter. This does not mean wireless power transfer using inductors is inherently inefficient.

Do you know of any other real world wireless resonant system in use that someone have tested and published the efficiency of? I believe it when I see it.

The one I designed and which is being produced & used does 80% end-to-end using off-the-shelf components. However this system has some inefficiencies due to design constraints. The 85% claim of the system which this topic is about isn't far fetched at all and I think it is possible to get better efficiencies. Surprisingly there is very little good and useful information on wireless energy transfer using inductors available. When a customer approached me to design a system which could deal with a 20mm gap I basically had to invent everything by myself.

But either way, it is always going to be less efficient than copper wire. In a future where everyone drives an electric vehicle, if you make the fuel even 5% less efficient it will have a huge impact on global energy use. And for what? So people doesn't have to spend a few seconds plugging in a cable? :/

How about plugging a cable in which is as thick as your arm and requires several tens of Nm of force to fixate the plug? Old and disabled people -for starters- aren't go to be able to do that. If you want to do really high power fast charging using a cable is going to be a big problem.

[CopperCone]

I would rather get an rf bite then touch 400vdc. Rf will just burn you while dc will remove a limb.
Think that its great.

Embedding some kind of badass rf transmitter in the garage floor would be epic. 95% efficency is great.

[apis]

The one I designed and which is being produced & used does 80% end-to-end using off-the-shelf components. However this system has some inefficiencies due to design constraints.

That is very impressive. There will always be design constraints so that sounds realistic. Still this means 10-15% less compared to using a connector (which would typically be ~95% efficient according to Wolfram's post).

So your car will use 10-15% more fuel if you use this.

How about plugging a cable in which is as thick as your arm and requires several tens of Nm of force to fixate the plug? Old and disabled people -for starters- aren't go to be able to do that. If you want to do really high power fast charging using a cable is going to be a big problem.

Yeah, there will always be a compromise between efficiency and comfort but here we are talking 10% less efficient compared to using the normal cables used today.

[CopperCone]

Where did you get that from wolframs post? I think you need to reread it

[Wolfram]

Inductive charging can be done at > 90 % efficiency with realistic geometries for EV charging: https://ieeexplore.ieee.org/abstract/document/6953459/ . Foreign object detection is one of the main challenges in this field, the actual power conversion is a solved problem.

For those without IEEE access, they get a measured efficiency of 96.5 % with a coil spacing of 110 mm. The receiver coil is 240 x 240 mm in size.

Impressive if they can take that from the lab to a commercial system that operates at similar efficiency. It's not a verified real world working system though, just because you can get that efficiency in a lab doesn't mean you can mass produce it that efficient economically. Would be interesting to see independent test of that bmw-charger for example.

There is no exotic technology used in that paper, the components are similar to those that you would find in a typical off-the-shelf high power battery charger.

They only mean the electronics involved in the wireless transfer, so compared to a normal connector you have to add the 5% losses from their laboratory prototype to the other charging component losses.

Once you have the power in the car, it's the same whether it was transferred wireless or not. After that you will need the same type of DC/DC converter to charge the batteries.

Ideally you should compare it with a system where you replace the wireless transfer module with a normal connector. It's the extra losses in the wireless transfer compared to a connector that is the problem here.

That there exist crappy chargers just shows that if these wireless chargers become common, in practice they will perform way worse than that.

The presented system is an actual charger, not just a power transfer system. It hooks up to the battery directly, and CV/CC charging control is performed on the transmitter side.

A wired DC charger would typically consist of an AC-DC converter (active PFC) with an efficiency of 96 - 98 %, and an isolated DC/DC converter, typically with an efficiency of 94 - 98 %. This system replaces the second stage, with a similar efficiency.