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From: John De Armond
Subject: Re: How to store 12V battery?
Date: Mon, 08 Jan 2001 05:13:49 -0500

Eugene Blanchard wrote:
> Hi
> I've got a 12V car battery (lead acid) that I'm not going to be using
> for at least 6 months. Any suggestions on how to store it?

Well, here's what the government says on the subject:

Probably more than what you wanted to know :)

Here's what works for me.

1. Bring the battery inside and wash the outside thoroughly with a
dilute solution of baking soda, making sure that none gets in the
vents.  This will neutralize and remove conductive contamination on
the outside of the case that will speed the apparent self-discharge
rate.  Also kills acid that will corrode things near it.  If you
have a DVM, you can check your work by touching the meter probes to
most any two random somewhat separated spots on the battery top.  If
you read any voltage, there is still leakage across the top of the
battery and requires more cleaning.

2. Store off the floor (so that crap doesn't collect around it and
not cuz concrete "sucks it down"  - it doesn't) in a clean and dry
place where the battery can't freeze.  If the battery is fully
charged and the specific gravity is up, anywhere under shelter is

3.  Top off the water.  Put a full charge on the battery (at least
overnight) and check the specific gravity of the electrolyte on each
cell with a temperature compensated hydrometer.  A very nice one can
be had at NAPA for under $10.  The absolute value isn't so important
as the equality.  If they are not equal across all cells within
about 0.05 points, the battery should be equalized before storage.
This involves overcharging the battery for several hours until even
the deep seated sulfate is converted to lead sponge and acid.  It
requires a charger capable of producing up to 16 volts.  If you
don't have one, a battery shop will probably do it for you for a
couple of bux if the battery isn't in too bad a condition.  Don't
underestimate the value of equalizing.  I deal with a lot of
batteries and know that proper equalizing will double (or more) the
life of any wet lead-acid battery (maintenance free excepted.)

4.  Attach one of the small automatic battery maintainer chargers to
the battery.  Not just a trickle charger but a unit with some smarts
that will turn off when the battery is fully charged and back on
again when it self-discharges a bit.  Everyone from Wally-world on
down sells little 1 amp jobbies for about $30.

5.  Check it every so often to make sure the water is up.  Probably
isn't necessary with the automatic maintainer but until you have
some experience with the device, better to be sure.

Of course, you could just yank it and park it in the garage and
forget about it :-)

An example of what good care can do.  I just replaced a pair of
Delco Voyager Group 27 trolling batteries on my computer room UPS
that I installed in 1992.  The batteries were essentially stored
during that period.  The UPS has a smart charger.  I equalized them
about once a year.  When I replaced them, they still showed about
1/4 of nameplate capacity on the load test. They still would have
cranked an engine but they would not run the computers long enough


From: John De Armond
Subject: Re: Best way to store battery?
Date: Sat, 02 Jun 2001 21:06:01 -0400

THP wrote:

> > Storing a dirty battery on a concrete floor is a guaranteed way to
> > discharge it over time.
> >
> NO...that's a myth!!! the battery WILL NOT discharge due to the fact
> that it has been placed on the ground or on concrete period!!!

No it's not.  It is a myth that the concrete discharges the
battery.  It is NOT a myth that a dirty battery sitting on concrete
(or any other damp surface) will self discharge - just what the
original poster said.  The concrete supplies moisture to the
conductive crap on the outside of the battery. This conductive film
gradually discharges the battery.  You can actually measure this.
Put a dirty battery in a moist environment, leave it awhile and then
probe the case at two points, one near but not touching each post,
with a DVM.  The voltage you see is from the current flowing through
the film.  Sitting the battery on blocks simply gets it a little
further away from the damp floor.


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