Re: (ET) Battery questions....

["Christopher Zach" <czach computer org>]

Hm. Gel cells have a different voltage-charge relationship than standard
flooded batteries. They float at different points, and typically are not
equalized.

And they *HATE* being charged by a simple transformer and a pair of diodes.
The charger in the ET will probably overheat the batteries and cause them 
to
either rupture or die fast. If you really want to use these, get another
charger (you might have to build one, as most people do not run 36 volts)

As to using Gel cells in a high current job like an ET... Well, here's a
thought:

I currently use a pair of 80amp gel cells in my shed to power the whole
thing. They're nice, no question there and they will not freeze if
discharged and left in the cold like a LA battery, but here's the problem:

When I run the inverter at full load and start pulling over 60 amps, the
voltage at the batteries starts dropping *hard* to about 23 volts. Pull 40
amps for an hour, no problem. 10amps for 6 hours? No problem. However when
you draw on them hard, the voltage output drops like a rock. It's not being
dropped in the wires; 4 gauge is rated to over 100+amps with no voltage 
drop
on the 10 foot length between battery and inverter.

I think the reason is that the plates can't react with the sulfuric acid in
the battery gel as quickly as the lead-acid flooded batteries can.

Just a data point; I'd recommend going to Sam's and getting 6 golf cart
batteries.

Chris


----- Original Message -----
From: "Tim Chapin" <tchapin umich edu>
To: <elec-trak cosmos phy tufts edu>
Sent: Monday, January 14, 2002 9:18 AM
Subject: (ET) Battery questions....


> I found a guy that is selling "Golf Cart" batteries, in sets of six for
> $150.  The story is, he buys them in bulk and then resells them.
Currently
> he has 21 left that are a year old but never used.  The brand name is 
> Best
> and they are what he calls "dry cell" batteries.  Was told you could cut
> them in half and have nothing leak out of them.
>
> Questions
> Any one heard of this brand and type of battery?
> If so are they any good? (seller stated they are a very expensive battery
> that will out last normal battery--of course what else would he say).
> Will the typical elec-trak charger charge these batteries?
>
> If they are something worth looking into, I will get back to him on the
> size.  He wasn't sure and gave me the size 15 X 7 X 7.  If that is truly
> the size, they will not fit any way.
>
>
>
>