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Gigafactory Will Lead the Way as Battery Pack Prices Drop By 35%

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Critic
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Wireless Charging Efficiency
Critic   6/3/2015 11:35:32 AM
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It sure seems like a direct, conductive connection would be an efficient way to charge a car.  For lazy people, the connection could be made automatically.  After you park your car over a charging port, the connection to the underside of the car is made robotically and charging begins.  When you return to your car, charging stops and the charging arm retracts.  No big deal.  Alternatively, the car could drive into a self-aligning charging port.

The article at www.modernpowersystems.com/news/newshigh-efficiency-inductive-ev-charger-developed says that a 13-cm coil spacing was used.  This is very close- most cars have more ground clearance than this.

www.wirelesspowerconsortium.com/technology/transfer-efficiency.html shows that for best efficiency of the coupled charging coils, we need close spacing and coils of similar size.  For best efficiency, the Q of the coils must be high, which is not easy to achieve.  The alignment of the coils in the X-Y plane is also important.

It is true that wireless power transfer people like to play games with efficiency figures.  An IEEE paper, "A High Efficiency 5 kW Inductive Charger for EVs Using Dual Side Control" by Wu, Gilchrist, Sealy, and Bronson includes a detailed efficiency analysis and (inaccurately) measured data.  The authors state that "only conduction losses are considered" in their analysis. 

If someone were to actually measure the efficiency of a wireless charging system accurately, I am confident that we would find that wireless charging is not as efficient as a direct connection.

William K.
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Re: you don't need a great battery
William K.   6/3/2015 8:22:03 AM
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I do agree with you that accepting wireless power transmission as effective certainly takes immagination. 

The fact is that no matter how hard we wish something to be true we are still limited by those laws of physics and mathmatics, as they relate to energy fields. I know that technology is advancing , and possibly some day energy will be available cheap enough so as to not matter how much is wasted. But that day is not in the near future as I see it.

I am aware that there are huge amounts of profit to be had by catering to laziness, and so wireless charging will always be supported. But until it can deliver the same efficiency as a direct connection that lower efficiency will always need to be noted, and presented to those who seem to be mandating that all inefficient uses of energy be curtailed. In addition, sometimes the truth does stand in the way of maximizing profit. This may be one of those times.

Cylon13
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Iron
Re: you don't need a great battery
Cylon13   6/3/2015 8:04:00 AM
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@WilliamK.....

You keep beating this inefficiency dead horse as if it's case closed; well, in your mind it may be. I really think you need to rely on a little imagination here. Technology is not stagnant. Also, you never addressed the point of reducing the energy transfer if indeed the wireless is that inefficient.  I see this paradigm everywhere that people think they have to go somewhere and fill-up on energy. The idea of making charging available as many places as you can breaks that paradigm, as well as solves the issues for those who are stuck in it. Agaiin, a new paradigm where topping off the tank, (battery) becomes reasonable is all I'm suggesting.

William K.
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Re: you don't need a great battery
William K.   6/3/2015 6:34:56 AM
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The one time that I saw an actual published efficiency of a wireless charging system it was in a very complex format, quite different fromhow efficiency is normally presented. That may be reasonable because coupling efficiency depends on a number of variables. 

But the universal tendancy to never clearly state the real efficiency tells me that it is not very good, because most folks brag about good efficiency.

The "best" one claimed a fairly high efficiency for converting transmitted power into charging power, but neglecting to use input power. So transmitting efficiency was not included.

ttemple
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Re: you don't need a great battery
ttemple   6/2/2015 9:14:08 PM
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I hear you.  That's why I said "they claim..."

William K.
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Re: you don't need a great battery
William K.   6/2/2015 8:27:34 PM
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97.5% efficiency is astounding, and also. So now the question is about the unknown "weasel words" describing what they mean by efficiency. That may be where the obfuscation lies.

ttemple
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Re: you don't need a great battery
ttemple   6/2/2015 7:39:39 PM
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www.modernpowersystems.com/news/newshigh-efficiency-inductive-ev-charger-developed

They claim efficiency of 97.5%, which isn't bad.

William K.
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Platinum
Re: you don't need a great battery
William K.   6/2/2015 7:29:31 PM
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At a time when eficiency is being mandated for all sorts of things it just does not seem reasonable that an inefficient system catering to the lazy and incompetent portion ofour society should be touted as a wonderful feature. We live with many restrictions all in the name of conservation of energy, and then hee is the low efficiency wireless charging system getting high praises. I would rather that wireless charging would go the way of open carbon arc lighting.

Cylon13
User Rank
Iron
Re: you don't need a great battery
Cylon13   6/2/2015 9:45:39 AM
"I see that you make no claim that wireless charging is efficient. It is always far less efficient than connected charging."

Of course not, human behavior doesn't rely on what is most efficient. It's usually based upon what's most comfortable. Pulling into a parking spot and connecting a charger is easy enough; however, pulling into a spot and doing nothing is easier.

"I do not claim that the magnetic fields are harmful, but that a number of folks think that they are. And blind fear often causes problems, since many politicians cater to those folks."

Well OK.... that's sensible enough; but blind fear as a substitute for science and reason is not an argument for not doing something. The blindness part is usually something self-imposed and the fear part is usually a reflection of the brainwashing in play. Politicians cater to the wealthy and corporations, not average people.

patb2009
User Rank
Gold
Re: Lowe battery prices? Don't bet on it.
patb2009   6/1/2015 10:19:07 PM
well, if the Gigafactory can generate fat margins, then you will see

other Gigafactories come online.

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