RE: Lead-Acid batteries and concrete floors

["Art Gale" <gale@candw.ky>]

OK, this one I know...I think.

 The question comes up so often while teaching auto electrics, that i
researched it a bit .

According to an engineer at Interstate batteries (forgotten the name) it WAS
true.
It came from the days LONG long ago...of wooden frames and glass containers
used in early batteries.

Sure enough, when left on a damp floor the wood gets unevenly moist, warps,
cracks the glass container  and there you go...battery no more good.

Of course there is also the dampness allowing a greater self discharge
current, but it couldn't be dramatic.

My only other plausible explanation comes from the still coolness of the
concrete promoting a more dense layer of lead sulphate than would form if it
were warmer or moving...and in my experience these batteries died from long
term neglect rather than floor material.

As for the temperature stratification....I don't buy it because the
conductivity isn't stratified
where is this current flowing to exactly?  I can't see how it could do
anything but make plate composition slightly different top to bottom...
can't see a battery killing current.


-----Original Message-----
From: owner-ev@listproc.sjsu.edu [mailto:owner-ev@listproc.sjsu.edu]On
Behalf Of VanDerWal, Peter
Sent: Friday, March 30, 2001 5:32 PM
To: ev@listproc.sjsu.edu
Subject: Lead-Acid batteries and concrete floors
Importance: Low


I'm sure we've all heard that Lead-Acid batteries will go dead quickly if
you store them on concrete floods (i.e. in the garage).

I'd pretty much assigned this to the "Old Wives" tale section since nobody
could provide me with a credible explanation of why this was so or any
verifiable tests indicating it was true.

Well I was going through some old magazines and I found a letter to the
editor that actually provided a reasonable sounding explanation of why this
happens.  I'm still not sure that they do go dead quicker on concrete, since
I've not heard of anybody testing it, but if they do this sounds like why.

The author pointed out that concrete floors tend to be colder than the
ambient temperature.  I've noticed this, I believe it's due to evaporation.

Anyway with the battery sitting on the floor, the bottom of the battery will
be colder than the rest of it.  This causes temperature stratification of
the electrolyte (different temperature layers).  The different temperatures
in the electrolyte leads to different specific gravity with the colder fluid
at the bottom having a lower specific gravity than the warmer fluid on top.
The different specific gravities will cause different voltage potentials
across the tops and bottoms of the plates.  With different voltage
potentials current will flow inside the battery and cause it to go dead
quicker.

So what do you folks think, sound reasonable?

P.S. If true I would suspect this has less effect on AGMs and Gel Cells.