From: elmore@virga.ucar.edu (Kim Elmore)
Subject: Re: batteries on concrete
Organization: Research Applications Program/NCAR, Boulder, CO
Date: Tue, 8 Sep 1992 22:10:27 GMT

	I went around a couple of times with the editor of the Ham
Radio about this very thing in a couple of Letters to the Editor.  I
challenegd an article that was otherwise excellent (as were nearly all
of the them in the dearly departed HR) when the author cautioned the
reader not to place lead-acid batteries on concrete because they would
be "destroyed"...

	The editor (I gotta look these up again; I still have them)
*supported* this viewpoint, evidenced by a reply he sent to my letter!
So, I wrote a *second* one and they both got published in the
"Letters" column.

	Anyway, I worked as a gopher in an automotive garage for
several summers and the mechanics there swore by this phenomenon.  So,
my dad and I, who were on good terms with them, challenged them to a
bet: we'd place two identical, new batteries on the floor, one
supported by the Holy Piece Of Wood and the other exposed to the Wrath
of the Evil Concrete.  On a daily basis, we took specific gravity and
voltage measurements on the batteries and graphed the results.  We did
discuss load testing, but everyone felt that voltage along with SG of
each cell was quite sufficient.  We did this for two or three weeks,
after being assured by everyone there that the "exposed" battery would
be dead in about a week.  If we lost, we'd buy the batteries at full
price and pay some amount to the participants.  If *they* lost, the
participants owed us something like $10 each and a grovelling apology
:-) This was the 70's, so $10 was a fair bit of money.

	Needless to say, we won the bet; the two batteries were
indistiguishable in their characteristics.  Whence the myth?  Well, as
near as we could figure, because cars are driven every day charge
retention isn't an issue.  Batteries that would otherwise be useless
had enough charge left to start the engine (if it was well tuned) and
then be charged enough for the next time; the short power requirement
followed by extended charging gave them an extra lease on life.  In
most cases, these batteries would be dead after several days standing
idle.  Often, when a battery needed to be removed it had been cranked
to oblivion anyway, so a minor problem was just made worse.
Automotive lead-acid batteries show a high self-discharge anyway.  It
all added up to bad batteries to start with.  Of course, upon
replacing a marginal battery into the auto, it was found to be dead.
The owner complained that it was OK to begin with and all the poor
mechanics could come up with was "must've been the concrete".  Go to
any garage: when mechanics remove a battery, they will inevitably set
it on a piece of wood.  Mystical tales explaining the unknown often
take on nearly immortal lives of their own.

	Besides, it's harmless enough, I suppose.  Still, it's one of
"those things" that never fail to draw a comment from me.  Q.E.D.  :-)



					Kim Elmore
					N5OP, PP ASEL/Glider 2232456
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From: alanb@hpnmdla.sr.hp.com (Alan Bloom)
Date: Thu, 10 Sep 1992 18:45:17 GMT
Subject: Re: Re: Of PL259 on 9913 and other sins.
Organization: Hewlett-Packard, Santa Rosa, CA