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

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

On 7 Jan 2002 at 13:01, Christopher Zach wrote:

> Well one thought would be to use three 12 volt regulators coming off the
> panels. Each 12v regulator would be charging two batteries. The back 
> ends of
> the regulators would all bus off the common current coming from the the 
> four
> panels rigged in parallel.
> 
> Same logic as plugging three household chargers in, then plugging those 
> into
> the same wall outlet. But I'll bet that the batteries would never charge 
> at
> *quite* the same rate, the universe being what it is...

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.

> 
> Another possibility would be to charge the batteries in sections of 24 
> volts
> using a timer. Thus with a battery layout of
> 
> 1 2 3 4 5 6
> 
> Batteries 1234 would be charged first for 5 mins at 24 volts. Then we 
> would
> shift to batteries 3456 for 5 mins at 24 volts. Then batteries 1256 for 5
> minutes. Result would be all three batteries receiving roughly the 
> amount of
> charge. Of course there would be overhead for the logic.

I think you're on the right track.  One caution, though:  batteries in an 
electric 
vehicle ~never~ discharge entirely evenly, because of manufacturing 
variations and inconsistent temperatures.  It's much worse in a stock ET, 
because the battery pack is tapped to power the lights and lift.

So if I were an electrical engineer (which I'm not; I dropped out of the 
program 
<g>) I'd probably consider a buck converter to drop that 24 volts to 6, 
and fly 
it around from battery to battery.

It might also be advantageous to use a bit of logic.   You want to 
equalize the 
batteries as you charge.  With the usual series charger this is done by 
main 
force: sending current through the cells and batteries already charged in 
order to finish up the ones that started off lower.  In other words, 
deliberately 
overcharging the already-charged ones.

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.

> I was thinking the T105 as a Trojan battery. I have heard their
> batteries are more solid than most. Is there a cheap generic battery that
> will get me started?

Golf car batteries are something of a commodity, and the makers are pretty 
competitive, so prices tend to stay fairly close.  

Some people think that Trojans are somehow better.  There are others who 
say that they might have been once but Trojan have made them cheaper in 
recent years (presumably for competitive reasons).  Still others say that 
the 
differences among well made batteries are less important in service life 
than 
the care you give them.  

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>

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.

Some folks have had good luck with Sam's Club batteries, which I think 
sell 
for around $40.  But beware, they buy from whomever bids lowest that 
quarter, so you could get anything.

The low-budget starter usually recommended is to get used batteries from a 
golf car shop or large golf course.  Avoid "rebuilt" batteries; they 
aren't a very 
good value.


> 
> If the T20 allows side discharge, I might be able to mount the Craftsman
> bagger on the rear, then run a very long pipe back to it. Might not work
> though if the blades aren't very fast...

I think you can make at least some of the mower decks side discharge by 
removing a plate inside.  There may be some other changes required too.  
Maybe someone else has the answer to this.

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 ...

Someone else suggested a tow-behind sweeper, which is probably good if 
you have a large yard with few areas where you have to jockey the tractor 
around.  (Of course a tow-behind vac would also make things more 
cumbersome in smaller yards or those with lots of cul-de-sacs.)

David Roden
Akron OH USA