wireless charging of batteries

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Has anybody tried to wirelessly charge a battery?
Is this impossible to implement? What is the maximum power that a wireless channel can carry? Of course it would depend upon bandwidth, noise, etc.

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Unfortunately air is a rather resistive medium, and thus any transfer of energy through free air will yield very low efficiency and high loss. I imagine it might be possible in space with a focused microwaves beam or something. I think I saw an article about NASA exploring this avenue on larger scales, to extract solar energy in space (where solar panels with concentrators can be used at much higher efficiency) and then transmit it to ground on massive antennas with a very narrow but high power microwave beam. From what I was reading practical applications of this were 10-20 years away.

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"Wireless" power transfer at small cost is limited to things like the cordless toothbrushes in which the base is like one half of a transformer and the other half is inside the handle.

There are many reasons why "wireless power" has never worked like it was envisioned by Tesla. The biggest is the "inverse-square" issue. From any antenna, the power density is reduced by a factor of 4 every time you double distance. To get any reasonable quantity of power, you need huge power densities near the antenna, and that becomes a hazard to the environment.

It is also very difficult to generate RF power at the levels needed to make this work AND it is very difficult to extract the RF power from the "ether" efficiently, especially at any quantity above a few milliwatts.

Jim

 

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How about using IR to charge then? Solar radiation seems to travel millions of miles and still provide energy that can be used (even in air).

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MIT are on it...

They say the key is Magnetically coupled resonance, putting two object on the same ressonante frequency.

http://web.mit.edu/newsoffice/20...

Regards,
Brunomusw

Regards,

Bruno Muswieck

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Read The Wireless Battery Charger Really Works article or go directly to WildCharge site.

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npat_avr wrote:
How about using IR to charge then? Solar radiation seems to travel millions of miles and still provide energy that can be used (even in air).

Light also 'suffers' from the inverse square law. It happens that what the sun emits is so intense that it still has enough ooompf to be useful when it reaches Earth :)

What we humans can generate with our primitive technology is completely and totally insignificant compared to what the sun generates. It's 109 times bigger than Earth, and it has 332,900 times the mass of Earth, most of it pure energy :D

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If your product is outside then a small solar array is your "wireless" charger

Quote:
Solar radiation seems to travel millions of miles and still provide energy that can be used (even in air).

The sun is a skosh more powerful than a lightbulb or LED. If you do not believe me look at the sun directly. I bet it hurts!!(LOL)

Jim

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for an example of a commercial wireless charging system, look at the palm touchstone

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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I think Nikola beat the MIT kids by only 110 years 8-) In all fairness though, the transmitter was a 1/4 wave top loaded helical antenna, but the receiver was a light bulb connected to a resonant inductor. In these days of reducing energy consumption, the losses of any sort of substantial wireless power scheme will not likely be tolerated.

Tom Pappano
Tulsa, Oklahoma

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What distance do you want ?
What is the power you want to transfer ?

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My phone charges wirelessly, but nobody's saying anything about how efficient it isn't, or how much RF noise pollution is produced.

Yes, it can be done, solar/piezo/RF rectification..
Very low rates, but practical for some apps.

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jcgalvez wrote:
Read The Wireless Battery Charger Really Works article or go directly to WildCharge site.

I looks to me like this is really a base with multiple conductors, and a connector that is designed to contact the conductors. They also now sell skins for iPhones with an de-integrated connector.

So, I don't think we can refer to this as 'wireless', as in 'RF'. Its just convenient.

David

Dr. David Harris OpenLCB Development Team openlcb.org

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Quote:

I looks to me like this is really a base with multiple conductors, and a connector that is designed to contact the conductors.

That company approached us with a view to us representing them in Europe so I've seen this in action. It is not "wireless" in the RF sense. They were at pains to point out how inefficient that method is. The "clever bit" in their design is that they produce molded cases for popular devices like iPhones and Blackberrys that act as a protective shield that has 3 small metal contacts exposed in a tripod pattern. The "base" is a board with metal strips across and the clever bit is that whatever way you lay the phone/MP3 down it's guaranteed that at least 2 of the pins will always contact alternate "fingers" of the metal strips. The base then pulses a signal up the fingers and has a dialog with the "case" to work out which orientation it is in and then switches the main +ve/-ve current into the right fingers to get the charge polarity right.

While it works we couldn't see folks wanting to have the metal base pads dotted around.

To be honest, when mini-USB is adopted as the standard charging jack for all products it's going to be easier simply to have the one charger for all devices and folks will probably accept having to "plug in".

Cliff

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Quote:
I think Nikola beat the MIT kids by only 110 years Cool In all fairness though, the transmitter was a 1/4 wave top loaded helical antenna, but the receiver was a light bulb connected to a resonant inductor. In these days of reducing energy consumption, the losses of any sort of substantial wireless power scheme will not likely be tolerated.

I don't think that Tesla beat MIT guys, is something really different now, MIT guys are bringing the Tesla's main ideia to the next level, to the level that may be in some years this technology will be acessible to everyone...

Regards,
Brunomusw

Regards,

Bruno Muswieck

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Quote:

I don't think that Tesla beat MIT guys, is something really different now, MIT guys are bringing the Tesla's main ideia to the next level, to the level that may be in some years this technology will be acessible to everyone...

It doesn't seem like anything fundamentally new to me. The MIT 'transmitter' was a coil without an antenna rather than with one, and Tesla's goal was long distance transmission rather than short, but I'm not seeing any new science here. It was wrong that the article did not credit Tesla's prior art. The problem with efficiency still remains, and IMHO won't be tolerated with today's energy costs.

Tom Pappano
Tulsa, Oklahoma

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Quote:
It doesn't seem like anything fundamentally new to me.

Tom, principles are the same, but now MIT are developing the technology to achieve a level that may be it will became avaliable to the masses.
And you said right, "Tesla's goal was long distance transmission rather than short" his goal, but He said that he could do it, but he didn't...

Regards,
Brunomusw

Regards,

Bruno Muswieck

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Wikipedia covers the topic pretty well. Apparently 80% efficiency is routine for medical implants.
I don't see much difference between the MIT discovery and Tesla's methods. Certainly they should have referenced him.

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Wow 80% seems a high efficiency. So why don't they "productionize" it?
Also is this similar to one of those magnetic metal detectors? What if you had a pacemaker and wanted to charge it without setting it off? (similar to how people with pacemakers cannot go through metal detectors at airports)