Re: (ET) Intro: Just bought an Elec-Trac

["Bob Murcek" <rmurcek geisinger edu>]

Just a clarification about the transformer isolation thing...  You can 
charge three pairs of 6V batteries at the same time from a single source, 
but you'd have to disconnect some of the tractor's interbattery 
connections.  This has been a hot topic here since most consider this a 
major nuisance.

>>> "Christopher Zach" <czach computer org> 1/7/2002 9:40:46 PM >>>
> Ah, but each of the three chargers has a transformer isolating it from 
> the
> power line, and from the other two.  Your regulator probably will not --
> although I believe that some MPTs may, I'm not sure.

Actually, they do. If they didn't, then the power from the batteries would
go screaming up into the panels causing back-voltage flow.

Still, I am going to test this over the weekend. At worst case, a diode
placed between the charger and the panel should prevent any form of
back-current, and since the max current forward is 7amps (well, 10) I can
use a reasonably diode.

Or I can just give it up and go with a 36 volt regulator. We shall see.

> But if you are using a flying 6-volt charger you can be more subtle,
equalizing
> at the battery level.  Perhaps it could measure the on-charge voltage and
> current, maybe look at the change in voltage and/or current over the time
that
> it's charging that particular battery.  It might store that information
for each
> battery, and use it to control the amount of time that it spends 
> connected
to
> each battery.  This way, if you've given the lift a workout, it could 
> give
the lift
> batteries a little more charge; or if you mowed after dark, it could give
the
> headlight batteries the extra they need.

The headlights are 12 volts? Hm. Methinks I need to go to my shed, plug in
the soldering iron, and build a 36v to 12v DC-DC inverter for the lights.
Not really hard to do, since I like to ride around with the lights on :-) 
Or
maybe a circuit to turn the lights on and off based on the ambient light.
This is the reason I got this thing. Not to have an electric tractor as 
much
as a platform to build fun things on. Does it happen to have air horns? :-)

> I tend to lean toward the third of these.  But that doesn't stop me from
having
> strong opinions about some battery manufacturers -- mostly one or two 
> that
I
> avoid.  <g>

Thank you for the thoughts. Sounds logical.

> Put it this way: if you get Trojan or US Battery (AKA Interstate
Workaholic)
> it's hard to go wrong.  Typical price range is $45-55 each.

50*6=$300. Not too bad for a one shot expense. And if the thing blows up, I
can use the batteries in the shed (more power!) so it's not really a waste
per se.

> I'd hate to see you run a smelly ICE vac for this purpose.  Hmm, I wonder
if
> you could adapt a rechargeable lawn blower/vac -- would it have enough
> guts?  Or maybe a 115 volt blower/vac, powered by a modern 36v inverter
(the
> ET inverter was pretty hefty)?  Uh-oh, now we're getting into some
significant
> expense ...

You know, I have a bunch of inverters here. They call them computer UPS
units for some reason. Seems that some crazy people junk UPS units because
the "replace battery" light came on. Boo hoo.

Of course, they're easy to re-wire to a battery core, put out very clean
power (they're for computers) and they would probably fit in an ET with 
room
to spare :-) The leaf-vac might not work alone, but if I attach the
craftsman bagger to the side discharge of the E20, I could use the vac at
the rear of the pipe as a sort of "super charger". It would also mulch
anything that came up the pipe, and provide negative pressure at the blades
(so the leaves would *want* to go up the tube). That plus a pair of 55
gallon drum liners. Yep, that would do it....

Thanks for the thoughts. I like to let my mind out to play on these sorts 
of
projects.

Chris