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Re: (ET) Golf cart batteries



This was not a myth but a solution due to material selection.
Originally the battery cases were manufactured out of a natural rubber
based compound.  This organic material was microscopically porous.  When
sitting on concrete the path to ground was established thereby draining
down the battery.  Modern battery cases are now plastic based and do not
have the microscopic porosity issues; i.e. The batteries can now sit on
Cement floors without gradual discharge. 

-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu
[mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Charlie
Sent: Thursday, January 15, 2009 12:59
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) Golf cart batteries

On Wed, Jan 14, 2009 at 4:52 PM, David Roden wrote:
>
>  There's no validity to the old myth that batteries left on a concrete

> floor will discharge, BTW.

David, have you performed any experiments to test this "old myth"?

I've never met anybody (other than myself) in 25 years of inquiry, who
actually did the experiment.

When I did it (20 years or more ago) I unfortunately did not control for
temperature, I didn't carefully clean the battery tops, and I didn't use
brand new batteries with a single batch of fresh electrolyte, so my
experiment wasn't really good enough to be considered science.

With that caveat being made, a lead-acid car battery resting directly on
concrete self-discharged slightly faster than the one resting on a
nominal 1" greasy wooden plank right next to it when measured every
weekday with a cheap ball-type hydrometer over the course of two or
three months.  I didn't write anything down at the time, which I greatly
regret since I can no longer remember any of the numbers.

Because of this I always put a board between concrete and a battery.
I have never suffered any harm from doing so, and it's really not any
extra work, and "old myths" in my experience often contain more than a
grain of truth.  For example, if you don't walk under ladders, you're
less likely to have a gallon paint can fall on your head.

I will happily change my behavior as soon as I see a properly documented
and controlled experiment that proves the batteries I use will not
discharge faster on concrete, but so far nobody's been able to point me
to any experimental data better than my own.  There's been no shortage
of people telling me I'm a liar or a superstitious fool, though. ;)

--Charlie

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