Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Battery on the ground

On Thu, 20 Mar 2008 08:54:22 -0800, "SteveB"
wrote:

I have heard that if you sit a battery on the ground or concrete that it
will lose its charge faster. Is this true?

Steve

There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation" which degrades
part of the plates much more quickly than when stored on an insulating
board. Can't find the cite right now, but it was explained by a
battery expert a few years back.

There is a reason MOST battery brackets on cars have a plastic tray
instead of mounting the battery directly on steel.
It is not as serious a problem with today's plastic cases as it was
with the old hard rubber cases, but with a large amount of our plastic
products coming from China, and the makeup of some of the plastics
being less than certain, I would not bet on it not being a problem in
the near future.

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Default Battery on the ground

On Fri, 21 Mar 2008 01:01:58 GMT, with neither quill nor qualm, Howard
Eisenhauer quickly quoth:

On Thu, 20 Mar 2008 13:48:28 -0400, clare at snyder dot ontario dot
canada wrote:

On Thu, 20 Mar 2008 08:54:22 -0800, "SteveB"
wrote:

I have heard that if you sit a battery on the ground or concrete that it
will lose its charge faster. Is this true?

Steve

There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation" which degrades
part of the plates much more quickly than when stored on an insulating
board. Can't find the cite right now, but it was explained by a
battery expert a few years back.


Nowadays, with Global Warming(kumbaya) and all, it's not a problem.
chortle Well, 'cept with Clare and the rest of the Arctic Circle
folks.


Theres just too much ancedotal evidence to dismiss this as an old
wives tale and this is the only explanation I've heard that makes
sense. I can see this happening on a floor that's in contact with the
ground, if the concrete was at room temperature , i.e. a second or
third story floor, then you shouldn't have a problem. That being said
I have stored batteries on concrete floors, I just give a kick every
now & then to keep the electrolyte mixed up. .


I stored the new battery for the welder on the shop floor for 2 years
and it was still pretty well charged when I tried it. I'm with Wes
since I haven't seen any dead batteries from being stored on the
floor. Anecdote that, Howie. I've heard the tale but throughout my
15ish years as a Wrench, I never saw it, and I haven't since, 22 more
years.


The "electrons leaking through the case" only happens with the plates
are coated with balonium. ;.


g

--
Death is more universal than life; everyone dies but not everyone lives.
-- A. Sachs
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On Thu, 20 Mar 2008 13:48:28 -0400 in rec.crafts.metalworking, clare
at snyder dot ontario dot canada wrote,
There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation"


Right. I was wondering if anybody who knew was going to post.
Conditions have to be right for it to occur, which is probably why
so many don't understand it.
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Default Battery on the ground

Don Foreman fired this volley in
:

If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?

Thank you Don. I was having near-irresistable urges to post something
similar. Apparently, in acid, Brownian motion ceases. Heavy molecules
settle out. G

LLoyd

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On Fri, 21 Mar 2008 01:13:50 -0700, David Harmon
wrote:

On Thu, 20 Mar 2008 13:48:28 -0400 in rec.crafts.metalworking, clare
at snyder dot ontario dot canada wrote,
There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation"


Right. I was wondering if anybody who knew was going to post.
Conditions have to be right for it to occur, which is probably why
so many don't understand it.


If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?


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On Fri, 21 Mar 2008 14:55:13 -0600, Don Foreman
wrote:

On Fri, 21 Mar 2008 01:13:50 -0700, David Harmon
wrote:

On Thu, 20 Mar 2008 13:48:28 -0400 in rec.crafts.metalworking, clare
at snyder dot ontario dot canada wrote,
There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation"


Right. I was wondering if anybody who knew was going to post.
Conditions have to be right for it to occur, which is probably why
so many don't understand it.


If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?


Most definitely.

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Default Battery on the ground

On Fri, 21 Mar 2008 17:38:32 -0400, clare at snyder dot ontario dot
canada wrote:

On Fri, 21 Mar 2008 14:55:13 -0600, Don Foreman
wrote:

On Fri, 21 Mar 2008 01:13:50 -0700, David Harmon
wrote:

On Thu, 20 Mar 2008 13:48:28 -0400 in rec.crafts.metalworking, clare
at snyder dot ontario dot canada wrote,
There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation"

Right. I was wondering if anybody who knew was going to post.
Conditions have to be right for it to occur, which is probably why
so many don't understand it.


If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?


Most definitely.


OK, perhaps I should have said lower pH or higher concentration. Even
plain water with a temperature gradient will have higher s.g. where
colder, down to 39F anyway.
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On Fri, 21 Mar 2008 14:55:13 -0600 in rec.crafts.metalworking, Don
Foreman wrote,
If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?


Why wouldn't the cold acid be a more dense than the warm acid?
But actually, the acid will stratify due to gravity without even a
temperature gradient if it sits long enough without stirring.

Good proposal for an experiment, by the way, but you would have to
use a battery not a beaker.

Let's see if I can keep the polarities straight. If you put a
lead-acid battery on your cold plate and establish a temperature
gradient through it, the warmer top will try to generate a higher
voltage than the colder bottom and you will have a current flowing
within the cell that discharges the battery. The top side reaction
depletes the H2SO4, making the density gradient worse.

When the temperature equalizes, the current flows the other way and
the plates even out enough for the same thing to happen again the
next day. Without the internal circulating current, nothing much
happens.

OK, that is probably pretty badly bollixed up, but you get the idea.
It has nothing to do with porous cases or external leakage. No
doubt somebody on sci.electrochem.battery can explain it better.
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On Fri, 21 Mar 2008 20:23:13 -0700, David Harmon
wrote:

On Fri, 21 Mar 2008 14:55:13 -0600 in rec.crafts.metalworking, Don
Foreman wrote,
If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?


Why wouldn't the cold acid be a more dense than the warm acid?
But actually, the acid will stratify due to gravity without even a
temperature gradient if it sits long enough without stirring.

Good proposal for an experiment, by the way, but you would have to
use a battery not a beaker.

Let's see if I can keep the polarities straight. If you put a
lead-acid battery on your cold plate and establish a temperature
gradient through it, the warmer top will try to generate a higher
voltage than the colder bottom and you will have a current flowing
within the cell that discharges the battery. The top side reaction
depletes the H2SO4, making the density gradient worse.

When the temperature equalizes, the current flows the other way and
the plates even out enough for the same thing to happen again the
next day. Without the internal circulating current, nothing much
happens.

OK, that is probably pretty badly bollixed up, but you get the idea.
It has nothing to do with porous cases or external leakage. No
doubt somebody on sci.electrochem.battery can explain it better.


This is the only theory that makes any sense to me.

Restating what I think you have tried to assert, with slight
modification and a bit of embellishment if I may:

If there is a vertical temperature gradient then cell voltage at the
top must be different from cell voltage at the bottom because cell
voltage depends upon temperature as well as electrolyte specific
gravity (s.g.).

If the cell's EMF is different at top than at bottom then current
must circulate within the cell. Example: I may have the signs
wrong, but let's say that the cell EMF is 12.20 at the bottom and
12.25 at the top. There's a net loop (vector sum) EMF of 0.05 volts
so enough current must circulate to produce .05 volts of IR drop in
the plates. (Kirchoff's law) But note that the circulating current
at the top is opposite in direction to the current at the bottom, so
it has the effect of charging in one region while discharging in the
other region. This eventually will result in changing the specific
gravities of the electrolytes in these respective regions until the
difference in s.g. offsets the difference in temperature so difference
in EMF becomes zero and a state of equilibrium is reached.
Stratification has thus necessarily occurred due to electrochemical
action and in spite of kinetic diffusion. I'm quite sure that kinetic
diffusion would prevent battery acid from stratifying in a beaker, but
(as you noted) a beaker is not a battery.

The net charge of the cell would not have changed except that the
charge-discharge process is not 100% reversable and efficient (not to
mention IR losses) so there must be some net loss of charge until
equilbrium is reached.

If the battery is temperature cycled from day to day, then this
process could happen periodically. In that case, some charge would
be lost with each cycle.

I don't know anything about how or if stratification would cause
plates to "sulfate" or whatever. That probably depends as much or
more on battery construction, age and history as anything else.

---

I have not noted self discharge rate in batteries kept on my concrete
floor to be any higher than others not on the floor ... but there
isn't much temperature gradient between floor and near-floor ambient
in my space. I keep air circulating 24/7/365 for other reasons.

---

I do not presume to dispute convictions or beliefs of others. This
is merely my tediously analytical way of trying to understand things.
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On Fri, 21 Mar 2008 23:51:02 -0600 in rec.crafts.metalworking, Don
Foreman wrote,
I don't know anything about how or if stratification would cause
plates to "sulfate" or whatever.


Remaining in a discharged state for any length of time is what
causes the plates to form large hard crystals of lead sulfate,
usually irreversibly.
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