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RE: (ET) battery charger controller
- Subject: RE: (ET) battery charger controller
- From: "David Roden (Akron OH USA)" <roden ald net>
- Date: Fri, 18 Aug 2000 16:40:48 -0400
- Sender: owner-elec-trak cosmos5 phy tufts edu
Larry, as I'm sure you know with your background in EVs, charging voltage
is important, but there is another factor. For longest battery life, the
charger needs a more sophisticated controller. It can be done with
linear devices or with a microprocessor, but no matter how you implement
it, you really need the IUI2 scheme I outlined in a previous post
(constant current / constant voltage / constant current).
Perhaps you were closer to the GE project, and you may know something
that I don't. However, while it may have been a contributing factor, I
don't think that the charger is the center of what shut down the ET. The
6-7 years of life that reasonably careful users get from the batteries is
fairly respectable. Longer battery life would just have postponed the
date on which the original users parked the tractor.
I think what killed the ET was the same thing that stymies sales of road
EVs right now -- the high cost of a limited-production machine relative
to its perceived benefits. The ETs primary virtues -- quiet operations
and zero emissions -- just aren't important enough to the average person
to pay that much more for.
And even if someone did buy one, after using it for 5-7 years and killing
the battery pack, for the typical Jane Homeowner those virtues apparently
often weren't strong enough to convince her to ante up $350 for a new
pack. That's why we're sometimes able to find these machines in dark
garage corners with stone-dead batteries.
Just like with road EVs, there are only a few possible sales stimulants
for electric garden tractors (or anything else that replaces a fueled
device). For some years now, I've argued that there are four enabling
conditions for EVs:
1. Adequate economic advantage for EVs
2. An activist government
3. An educated, environmentally aware population
4. Full cooperation from vehicle producers
At least three of these need to be in place for them to succeed. Right
now, the US doesn't have ~any~ of them, with one exception: Arizona has
a pretty strong road EV incentive package, which covers points 1 and 2
(as I understand the law, Arizona residents can get back, in direct
rebates and tax incentives, just about 100% of the money they spend to
buy a road EV in tax incentives).
I've slightly modified this list recently, as I no longer believe that
economic advantage alone is sufficient for the first point, and education
alone is not enough for the third.
I think that, for the first point, EVs have to provide a significant
advantage in ~convenience~. This might be caused by a fuel shortage and
the attendant inconvenience. By this I mean gas lines and/or rationing.
Increased fuel cost alone has to be ~very~ high before it has an
equivalent effect.
I also now believe that point 3 needs a strong marketing component to
generate intangible emotional rewards for prospective purchasers.
David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak E15 36vdc
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