RE: (ET) battery charger controller

["David Roden (Akron OH USA)" <roden ald net>]

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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