Air Coupled EV Charging

On Monday, 25 March 2019 15:32:05 UTC-7, snipped-for-privacy@gmail.com wrote: ...

ny sort really. They have a video that compares their 10 kW system to the "standard" 3.3 kW system. I've never seen a 3.3 kW L2 charger. That would be 240 volts, ~15 amps. The lowest I've seen is about 7 kW. ...

n hybrids are ~2kW.

use.

use.

nly work up to those levels (3.3kW or less) even if the EVSE advertises hig her capability.

power is constant at the maximum rating until close to the end of the charg e.

on the Pilot line. The charger internal to the vehicle only consumes power up to that amount or to its internal limit.

few vehicles significant?

...

You stated that you had never seen an L2 EV charger rated at less than 7kW

- I was giving you a couple of examples.

kw

Reply to
keith
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A system could be made, with lower Q and coupling coefficient in the 0.9 range, by relatively simple automated motion and optical target acquisition. Drive over the plate, park, and let the robot attendant refill the electron tank. You just want to be sure that the demi-transformer is powered-down and retracted into its foxhole before driving off.

Heck, if you can park in the right vicinity, a blinkielight beacon can attract any nearby charge attendant the moment your drivers' seat is vacated.

Reply to
whit3rd

So with the former it is like a transformer and the latter more like a radio transmitter and receiver. Kinda. I get that.

But isn't it true that the power transferred goes down the square of the distance ? Even Tesla knew that, and of course he tried to break the rules.

Hang on here, a tuning fork is not loaded. This coil that has its output rectified is going to have real power taken from it.

Even at its exact resonance there must be enough excitement to overcome that load.

I have seen a separable transformer, it was like a male and female. That makes sense to me because even regular transformers are wound with the primary either in the middle or around, or more likely the other way around. Whatever.

The facts don't seem to jibe here but it might be me.

Reply to
jurb6006

ficiencies are due to different converter topology and components

d the losses involved? Do you know anything about the cable sizes they use for the current chargers? How much power is lost in the cable and connect or?

You may be well right that he doesn't know. That can be found by a table, w ire size and current, not hard. However anyone claiming that magnetism is a more efficient way to transfer power than a piece of wire has some convinc ing to do before I buy it.

I do however admit that inductive, if efficient enough is the way to go. Co nnectors are a pain in the ass and they are also out in the elements. they will corrode and eventually let out some smoke and then how much to replace ? That 75 watt Hakko is not likely to be able to handle the job.

If there is empirical evidence that inductive or resonant can be more effic ient than wire there has to be a reason. Something deficient in the connect ors or something, though that would be heat and that would be smoke and tha t would Al Fine.

I just don't see it, enlighten me. How the hell can it be better than a pie ce of wire ?

Reply to
jurb6006

require a small number of turns, and can that be efficient? "

I would imagine they are multifilar and not much of a core. (to saturate)

Reply to
jurb6006

I think it is all about the Rx coil.

Does the loop antenna in an AM radio "suck" more power out of the incident E and H field if the loop is resonant? If so.... how and why?

I think the answer is yes, but not sure and not sure how or why. thinking of grid dip meter... m

Reply to
makolber

Impedance is lowest at resonant.

Reply to
edward.ming.lee

any sort really. They have a video that compares their 10 kW system to th e "standard" 3.3 kW system. I've never seen a 3.3 kW L2 charger. That wou ld be 240 volts, ~15 amps. The lowest I've seen is about 7 kW. ...

in hybrids are ~2kW.

ll use.

ll use.

only work up to those levels (3.3kW or less) even if the EVSE advertises h igher capability.

t power is constant at the maximum rating until close to the end of the cha rge.

le on the Pilot line. The charger internal to the vehicle only consumes pow er up to that amount or to its internal limit.

a few vehicles significant?

W - I was giving you a couple of examples.

You gave examples of cars that needed less than 7 kW. The term "charger" i s normally applied to the device that is used to connect the car to a 240 v olt power source. It's not really a charger in that it does nothing with t he incoming power other than switch it on and off. But that is what I was talking about.

The lowest unit I have seen in the wild or even discussed is rated for 30 a mps, so about 7 kW.

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Reply to
gnuarm.deletethisbit

On Wednesday, 27 March 2019 14:52:20 UTC-7, snipped-for-privacy@gmail.com wrote: ...

7kW - I was giving you a couple of examples.

is normally applied to the device that is used to connect the car to a 240 volt power source. It's not really a charger in that it does nothing with the incoming power other than switch it on and off. But that is what I wa s talking about.

amps, so about 7 kW.

...

I was using the terminology where the unit external to the car is an EVSE. The unit inside of the car is the charger (except for level 3).

There are quite a few EVSEs available that support less than 30A - particul arly portable ones. I have an Aerovironment unit that does 16A when plugged into a 240V socket.

Here is another example:

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ation

kw

Reply to
keith

rote:

efficiencies are due to different converter topology and components

and the losses involved? Do you know anything about the cable sizes they u se for the current chargers? How much power is lost in the cable and conne ctor?

wire size and current, not hard. However anyone claiming that magnetism is a more efficient way to transfer power than a piece of wire has some convi ncing to do before I buy it.

No one is asking you to buy it. This is between the taxi owners and the po wer providers. One of them will need to pay for the losses. I don't think the company making the equipment will get away with lying about the effici ency since this will be money from someone's wallet.

Connectors are a pain in the ass and they are also out in the elements. the y will corrode and eventually let out some smoke and then how much to repla ce ? That 75 watt Hakko is not likely to be able to handle the job.

Not just a PITA, but in the use case of the taxi being charged while in the moving line of a taxi queue connectors are a no-go.

icient than wire there has to be a reason. Something deficient in the conne ctors or something, though that would be heat and that would be smoke and t hat would Al Fine.

I believe someone pointed out that the rest of the power supply system is d ifferent as well. Providing DC power to an EV is not without losses before it reaches the cable and connector, although I don't think you appreciate the current flowing. I recall the number 400 volts being used in charging discussions and I this system provides 74 kW. That's almost 200 amps! The cable that connects to the car has to be flexible with lots of strands. I don't know what gauge they use, I do know the cables I've used get hot. I believe it would take a fair amount of wasted power for it to heat up that much. It's a damn thick cable, about the size of a gas pump hose, but muc h heavier and stiffer. Then there are some 10's or 100's of feet to the ca binet where the converters are housed.

iece of wire ?

You don't actually know anything about the system do you? Stop focusing on a piece of wire and look at the system.

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Reply to
gnuarm.deletethisbit

See this paper for a high Q self resonant coil:

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At the same distance as the diameter of the coil, they achieve:

95% efficiency k = 0.03

See equation 13 for the efficiency relationship

A typical coil for a EV charging application has a lot lower distance between the coils as compared to the diameter, so efficiency will be even higher (see fig 7)

Cheers

Klaus

Reply to
klaus.kragelund

Which partner is responsible to limit the charging current ? Is it the charging station or the electronics in the car ? The charging should start at full current and then it should start to drop.

Making an unregulated 400 Vdc power supply capable of a few hundred anps is not a big deal with 6, 12 or 18 pulse rectifier thus with 2 to

6 diode voltage drops, the efficiency would be very high. Adding accurate voltage.and current regulation complicates things.

If the current regulation us not done in the external charger, then it must be done within the car,.

Most likely the low direct coupling efficiency might include MV/LV transformer losses, rectification losses in charging station as well as current limit in charging station and/or in car electronics.

The high RF efficiency suggests that it only contains the losses in the pick-up coil and RF rectification, thus comparing apples with oranges.

Reply to
upsidedown

Oh, and why resonant?:

  1. Resonance nullifies the leakage inductance and magnetising inductance increasing the gain of the coupling

  1. Switching harmonics are filtered, so low frequency sine current on the secondary side

  2. Resonant operation of the Class D stage: low losses of the driver

  1. Lower harminics, resulting on lower copper losses (dowell proimity loss has less effect). Skin effect lower effect

See page 11 (18) in this paper:

formatting link

Shows once again that quality factor is the key, k really does not matter much at resonance

Cheers

Klaus

Reply to
klaus.kragelund

On Wednesday, March 27, 2019 at 6:01:33 PM UTC-4, snipped-for-privacy@kjwdesigns.com wrot e:

:

n 7kW - I was giving you a couple of examples.

r" is normally applied to the device that is used to connect the car to a 2

40 volt power source. It's not really a charger in that it does nothing wi th the incoming power other than switch it on and off. But that is what I was talking about.
30 amps, so about 7 kW.

. The unit inside of the car is the charger (except for level 3).

ularly portable ones. I have an Aerovironment unit that does 16A when plugg ed into a 240V socket.

station

I don't know why you are continuing to discuss this. You were talking abou t the cars, I was talking about charging units, totally different things. Which I pointed out clearly. I was never talking about mobile cables, or t he boards in the cars. I was talking about charging stations. This should have been clear in the context of discussing the video of a charging stati on.

The examples you are giving now are rare and not seen much in the *wild* wh ich is my entire point. I never said they didn't exist. The video in ques tion compares their system to the '"standard" 3.3 kW system.' I don't see how this could be anything like a "standard" since they are not at all comm on. 30 amp systems are *much* more common, at least here in the US. That is what I would call the standard. I would also point out that charging a battery EV is not very effective at 3.3 kW. That requires more than overni ght charging to fill the battery on most EVs sold today. So in the context of the video the 3.3 kW system is a poor choice for comparison.

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Reply to
gnuarm.deletethisbit

On Wednesday, March 27, 2019 at 7:03:01 PM UTC-4, snipped-for-privacy@downunder.com wr ote:

s different as well. Providing DC power to an EV is not without losses bef ore it reaches the cable and connector, although I don't think you apprecia te the current flowing. I recall the number 400 volts being used in chargi ng discussions and I this system provides 74 kW. That's almost 200 amps! The cable that connects to the car has to be flexible with lots of strands. I don't know what gauge they use, I do know the cables I've used get hot. I believe it would take a fair amount of wasted power for it to heat up t hat much. It's a damn thick cable, about the size of a gas pump hose, but much heavier and stiffer. Then there are some 10's or 100's of feet to the cabinet where the converters are housed.

The car is always the boss, or in reality, the battery management system (B MS). The charger (or EVSE, a not so friendly term) simply reports to the c ar the available current. The car then uses what it needs up to that level .

I'm sure that is not the case as it won't fool any of the operators. They will be measuring the power drawn from the utility and the power supplied t o the car. If this company is spouting BS it will be discovered very quick ly. Only Donald Trump lies even when everyone knows he is lying.

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Reply to
gnuarm.deletethisbit

Space is the realest inductor!

Tim

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Reply to
Tim Williams

Well, he claims to have made resonant couplers, but making something is not proof of understanding...

Tim

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Reply to
Tim Williams

Not loaded with what?

If you can hear it, there's a load on it. If it's vibrating your fingers, there's a load on it!

A tuning fork can resonate for tens of seconds, evidently having a Q of some thousands. Pretty comparable to the present subject, actually.

Just because you are or aren't drawing real electrical power from something, doesn't mean it doesn't obey the laws of physics. :-)

Tim

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Reply to
Tim Williams

Wrong. If you generate the power you waste without burning fossil carbon (and dumping the CO2 generated into the atmosphere) you can waste as much as you like without damaging the planet.

Generating energy from solar cells is cheap (when the sun is shining). John Larkin has not been paying attention for years and has some very antiquated ideas (most of which he seems to have got from denialist propaganda web sites).

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Bill Sloman, Sydney
Reply to
bill.sloman

Digikey, tape and reel.

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Reply to
John Larkin

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