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Installing A Wireless Charging System: What It Really Takes

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Electric cars of various types are often grouped as "plug-in cars," but recharging the battery pack doesn't always require an actual plug.

Wireless charging, in which the car is positioned over a charging pad on the floor of a garage, is sometimes touted as a technology that will ease the adoption of electric cars by eliminating the unpleasant need to plug the car into a charging station.

We're not sure we're convinced--a charging cable is usually nice and clean compared to your average gasoline hose--but there's a lot of activity in wireless charging nonetheless.

Hertz, the car rental agency, is expanding its electric-car rental program by starting to experiment with wireless battery charging. Last Friday, it installed its first wireless-charging unit in the garage at its Park Ridge, New Jersey, headquarters.

The goal is to test the unit internally and gather feedback on well it works in everyday use. Users will give feedback on daily usage, their charging routines, the interfaces, and any new functions they feel should be added. Five other companies will take part in separate trials along the same lines as well.

Hertz sent us photos of the installation process, which took about six hours. They're snapshots--the quality isn't the highest--but they give a good idea of the adaptations required to the Nissan Leaf electric car to fit the receiving end of the Plugless Power system Hertz chose.

2012 Infiniti LE Concept

2012 Infiniti LE Concept

Enlarge Photo

They also show the Plugless Power system (from Evatran, Wyetheville, Virginia) mounted on the garage wall, plugged into a 240-Volt outlet, and the installation of the garage-floor charging pad over which the car must be positioned to recharge.

Note that the power conduit for the charging pad has to be trenched into the concrete garage floor. That potentially makes installation messier and adds an extra step to what's required to install a conventional charging station on the wall.

At the recent New York Auto Show, the Infiniti LE concept--which previews a four-door electric luxury sedan that will go into production two years from now--was shown with a wireless charging system.

The clever angle there was that the Infiniti's self-parking system would let the car position itself precisely over the charging pad without the need for the driver to make such fine adjustments.

Would you adopt wireless charging for your own electric car (if you had one)? Or is a conventional cable-and-plug-handle setup good enough?

Leave us your thoughts in the Comments below.

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Comments (20)
  1. I'd say that cost will, as usual, dictate adoption rates. As mentioned, power cords are not Cobra snakes and people have, you know, plugged in things for about, oh, a century or so.
     
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  2. Clearly it's convenient and sabotage proof in public space. Maybe it's a way to solve the problem of heavy charging cables for future superfast charging (200+KW chargers...)if that is a real issue, but that depends on the safety limits of this technology. Wouldn't want to microwave the whole town in the process....
     
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  3. Whether it is a car or a cell phone the one question I have about wireless charging mats is how efficient are they compared to a wired connection. A certain amount of power must be lost in the wireless transfer process. If that loss is more than 10% then I would rather plug my car in and not waste power.
     
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  4. Everybody claims about 5% loss or less.
     
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  5. A true Wireless system is "silly" scientifically speaking. Volt and Leaf can charge at 3.3KW and Ford Forcus can charge at 6.6KW. Do you really want to park near a "wireless" charging station? That is powerful enough to be a radio station. Not to mention the loss in efficiency. It is related to the square of the distance. The best you can do is couple inches away. At that distance, the loss can still be significant.

    But they can always make the charging process easier by installing charging "rails" where connection are wired but no efforts are needed beside parking skills..
     
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  6. What you are saying is "silly" scientifically speaking ;)

    The frequency used for this system is in the tens of kHz, so your cell phone (in the GHz band) is safe. Even old-school AM radio is in the kHz range and won't be affected. And of course any such system must conform FCC regulations. So no fear of a 3.3 kW transmitter disturbing all radio traffic in a wide area!
     
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  7. Secondly your claim that power loss is equal to the square of the distance is not true. This is only so for a perfectly omnidirectional signal in vacuum. This is more sophisticated and based on matching harmonic freqencies of the coils. You could say that the receiver in the car 'bends' the electromagnetic field towards itself.

    The gap width can be more than just a few inches, I've read up to 40 cm..

    Some background articles to get you up to speed on wireless charging:
    http://www.greencarcongress.com/2011/12/evatran-20111223.html
    http://www.greencarcongress.com/2011/04/siemens-20110408.html
    http://www.greencarcongress.com/2011/03/haloipt-to-provide-induction-charging-system-for-phantom-ee.html
     
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  8. I never said it won't work. Induction charging has been used in many different places. From your toothbrush charging to Induction stove. But all of them lose their efficiency with distance. Even in your links, it indicates that it would work up to 15 inches BUT it ignores the efficiency rating at that distance. It said the efficiency rating is at 90% but it didn't say at what distance and power that efficiency was measured. They are "marketing" info, not engineering technical info. Even at the best case 90%, a 3.3KW system would lose about 300W of power. That would add 10% to the cost. Direct connection is much higher in efficiency.
     
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  9. So....do you have an idea what the maximum safe power transfer for inductive charging might be, in other words, could it be used for fast charging?
     
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  10. According to what I've read at greencargress.com, yes. It could be used for fast charging without safety issues.
     
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  11. Well, the charging system frequency is inversely proportion to the coil size. The higher the frequency, the smaller the coil size. KHz is perfectly fine. But with amount of power emitting, safety is relative. People don't even want a high power wifi system (less than 1 W or 2W), do you think they want a 3.3KW system?
     
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  12. There are more comments in this thread
  13. First thing to get off my mind is that I have never seen a comment system so stupid as to claim the cursor keys to do some nifty navigation, preventing you from editing any typing mistakes.

    I'll probably give up in frustration after a few posts!
     
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  14. Plug-in is fine for me. I learned how to plug-in the gas nozzle at the age of 15 when I got my first drivers license. Yeah, way back then, 1945, one could get a license @ 15. However, Plug-in electric would be (1) cleaner, (2) won't smell of gas and (3) will never burp gas all over you.
     
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  15. I don't believe claims that inductive charging equipment can be as cheap as plugs. Many extol the convenience of inductive charging, but come on, how difficult is it to grab a plug and push it into a socket? Me? I wouldn't pay more than $100 for this extra convenience.
     
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  16. Just look at all the loss factors involved with inductive charging that is NOT necessary. 1. Convert 50/60Hz to higher frequency will have "switching" loss. Then Inductive charging will have another 5-10% loss (assuming ideal distance). Then the receiver have to down convert back to lower frequency. Another loss...

    All of those can be avoided with conductive charging. After all, electric car is about efficiency...
     
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  17. OK I think I read all the posts n replies above. I gotta go with Xialong on this one. It seems the power loss with any type of wireless charging puts into the realm of only for rich folk or specific applications like taxis of same model that can have the charging pad just a few centimeters away from the EV to dramatically reduce electricity loss during transmission.

    Better yet I think Mr. Li's idea of conductive charging has more merit then wireless. We've had this type of charging for decades now with many of the city buses in San Franscisco. Not exactly sure how the rails would work for existing homes but for new homes it seems like it might be a future option to have installed....like solar panels are going to be later this decade.
     
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  18. somhow we have to get away from the big batteries that lose life and are too expensive...we need to be able to continuously charge or supply the car with energy as we drive..that is the way the electric car will work ..also we won't have to drag around the large battery packs
     
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  19. These pads would solve the major problem of other EV drivers unplugging your car while it is getting charged. For home use, I really don't think it makes much of a difference, but there have been times that I forgot to plug in.
     
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  20. This is pretty much my take as well. Plugs are easy and economical. Wireless would be resistant to unthinking EV drivers, vandals and saboteurs in the public space. It would also make opportunistic charging a bit simpler.
     
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