Re: (ET) Golf cart batteries

["Hazen, Dwight L" <hazen indiana edu>]

>From this web site, answers are all over the place.

http://oldholden.com/node/29402

Dwight
------------------

Just an example, I like this one Dwight.


Regardless whether you think
   prove it yourself (not verified) on Sat, 26/05/2007 - 13:55.
Regardless whether you think the experiments were flawed, why not try it 
for yourself? I have (by accident) tried the experiment with two new 
batteries, fully charged, one sat on a "creeper" off the floor and the 
other on the concrete. This was in mid-summer in Texas, and in four weeks, 
the battery on the concrete was DEAD AS A HAMMER (not slightly lower in 
voltage because it was cooler). The battery on the creeper was practically 
fully charged still.

After a few weeks of being perplexed (I was a physics major and knew what 
I'd seen was impossible :-) I finally figured out what was going on: The 
cell voltage is indeed dependent upon the temperature of the cell... but 
the top of the cell was not at the same temperature as the bottom of the 
cell! One part of the cell was discharging and trying to charge the other 
part of the cell because of the temperature gradient across the cell. The 
cool, 23C concrete was soaking the heat out of the bottom of the battery 
by conduction, and the top part of the battery was being warmed by the 37C 
ambient air.

So... setting a battery on the concrete won't discharge it IF the ambient 
air temperature is the same as the concrete... but if the concrete is 
significantly cooler OR WARMER than the surrounding air, the battery WILL 
discharge itself. Try it for yourself if you don't believe it... and I'll 
expect credit when all the battery manufacturers quit "busting the myth" 
and actually try it for themselves, sheepishly admitting that I (and all 
our grandfathers) were right all along!

-Jon



-----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 PM
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

_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak