Date: Wed, 13 Mar 96 09:07:58 EST
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: sas@xyplex.com (Scott Sminkey - Sustaining Eng Group)
Subject: RE: Battery for Vanagon
Steve Maher <smaher@gi.com> wrote:
>Most car batteries are lead-acid, of course. But weren't there once some
>nickel-cadmium car batteries? The advantage here, of course, is that
>it doesn't hurt a NiCd battery when you run it all the way down flat,
>while it does hurt a lead-acid type to do that.
Whoa! It *does* hurt a NiCd battery to run it down flat! What can happen
is that one or more of the cells in the pack reverse polarity. If that
happens, you might be able to use a zapping technique to reverse it back,
but that doesn't always work. There has been much written about the care
and feeding of NiCds in ham radio publications, so if you want the details,
check the index of QST magazine at your local library.
To summarize, NiCds are not deep discharge type batteries, but on the other
hand, they should be discharged substantially before recharging rather than
"topped off" frequently or continuously. If they are discharged only a little
bit then recharged, you'll find you won't get a lot of use between each
recharge. A slow charger is always better than a fast charger to prolong the
useful life, i.e., number of charge-use-recharge cycles.
You are right that lead-acid batteries shouldn't be run down flat either,
but they can be discharged much deeper than NiCds, particularly the types
designed for deep discharge, and they will recover. Lead-acid batteries
can and should be trickle charged to prolong life and can take many more
charge-use-recharge cycles than NiCds.
The other type of battery to consider is sealed gel cells. These are like
lead-acid batteries but use a paste instead of a liquid. They have the
advantages of lead-acids without the potential mess and safety hazard of
spilled acid. A good cheap source of these is burglar alarms companies
where they periodically swap out the gel cells even if they are good. These
used but good gel cells often make their way to electronics and ham radio
flea markets. A bunch of the small ones would make a nice 12VDC source for
a camper. There are special charging requirements for gel cells which I'm
not familiar enough with to explain here. QST had an article about this and
a project to build a charger not too long ago.
Hope this is all useful to someone...
Scott
amateur radio WO1G
'91 Vanagon Westfalia Camper
=============
Scott Sminkey, Sustaining and Specials Eng. Xyplex.Inc.
ssminkey@xyplex.com 295 Foster St.
508 952-4792 fax 508 952-4887 Littleton, MA 01460
> *** Friends don't let friends vote Democratic! ***
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