I do like Bob's solution for it's simplicity. However, anything
mechanical under the car is a non-starter for the OEMs (they claim it is
THE most hostile environment in the world). In some ways, this is the
equivalent of the J1772 - no power to the lines until you have the power
signal active. I hope to get the wireless charging as simple as that,
but then how to deal with paying for the power? *sigh*
I have great respect for the testers - they do come up with the oddest
corner cases, don't they? :) As for whether it is possible to steal
20W, yeah, that's possible as long as you don't disturb the flux too much.
As for the coils, not my area of expertise. Yes, it is quite possible
to focus the beam, and I *think* this is what will end up happening.
However, at this time in the standards groups, they have not decided on
the final technology. Once they do decide I'll be sure to let the group
know (once I get clearance from the dreaded lawyers). :)
On 7/20/14, 11:54 AM, Peri Hartman via EV wrote:
Another thought, Peter. Is it possible to use multiple coils to
focus the "beam"? I don't know wave theory but I believe directional
radio transmitters work by having two or more antenae. Can something
similar be done with inductive coils?
If so, then using some sort of directional recognizer, the transmitter
could focus the beam exactly to the receiver area. I'm hoping this
would reduce risk of exposure when humans, animals are in the vicinity
and also improve efficiency.
Peri
------ Original Message ------
From: "Lee Hart via EV" <ev@lists.evdl.org>
To: "Martin WINLOW" <m...@winlow.co.uk>; "Electric Vehicle Discussion
List" <ev@lists.evdl.org>
Sent: 20-Jul-14 11:37:04 AM
Subject: Re: [EVDL] EVLN: BMW&Daimler developing 3-Hour Wireless
Inductive EVSE for i3 EV
From: Martin WINLOW
Not wanting to shoot your work down but I am reminded of (I think
it was) Lee's idea of using
an auto engaging charger connection which would be much more
efficient, much cheaper and only
marginally less practical.
It was actually Bob Rice's solution (although the idea is no doubt
even older). In 1968, Bob had an EV with drive-on charging. It was a
bump-stop that you drove up against. A platform between the front
wheels would slide sideways to center itself between the front
wheels. It had two brush contacts on the top surface, that mated with
contacts on the bottom of the car. The contacts were dead until the
car was present and electrical contact was established. Simple as dirt!
I know that people are often fascinated by complex solutions.
Advertising can often talk them into paying extraordinary prices for
trivial conveniences or hypothetical benefits. Companies like them
because they can make a lot of money selling them (especially if they
can get laws passed to make it a "standard"). But if you actually
expect them to be widely used or survive in the long run, I think
we'd all be better served by working on simpler ways of doing it.
GM's Magnecharger comes to mind. A good idea, expensively
implemented, legislated as a standard, and now a footnote in history.
On an 85 KHz high power inductive charger: As an EE, I can't see how
the charger can detect a 0.1% energy loss to some unexpected device
in the area. And yet, that's enough power to easily heat up
unintended "receivers" and fry sensitive electronics that by chance
just happen to resonate at 85 KHz. How can you reassure me that this
won't happen?
When I was designing safety-critical consumer electronics, we'd have
someone on the team whose *job* it was to try to "break" the system.
If the guy was good (and he needed to be) :-) he'd come up with
things we never thought of in our wildest dreams! So... with your
inductive setup, what if you *tried* to find a way to trick the
electronics, and steal 5-10 watts of power from the charger without
tripping the safety shutdowns? If you can do it, then Murphy will
probably discover some mass-produced gadget that just happens to do it.
--
A free whistle given away in millions of boxes of Captain Crunch
cereal just happened to be exactly the right frequency to turn off
the phone company's long-distance billing equipment, so kids could
make free long-distance calls!
--
Lee Hart http://www.sunrise-ev.com/controllers.htm now includes the
GE EV-1 controller
--
Those who say it cannot be done should not interrupt the one who is
doing it. -- Chinese proverb
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net
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