Date: Fri, 21 Apr 1995 20:22:13 -0600 (MDT)
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Jack Reed <jackr@fortnet.org>
Subject: Re:Speaking of batteries...
As promised, here's the text of one of the articles I've collected on
EDTA relative to lead-acid batteries. I have another, longer and heavier
article that would have to be shipped due to the length and graphics
included in it. If you're really interested in it, let me know offline.
It was put out, as mentioned previously, by an alternative energy
BBS and specifically relates to the type of deep cycle batteries
used in photo-voltaic systems. The author was able to bring back from
the dead several (16, I think) big, heavy batteries that had been drawn
down to nothing by a vengeful ex-wife by leaving the lighting in the
cabin on for several months after disconnecting the charging system.
As the article explains, significant work had to be done to rejuvenate
the batteries such as several rinse and drain cycles replete with trickle
charging.
If EDTA could bring _those_ batteries back, it can certainly help the
batteries we abuse in our bricks 8).
Jack
(article follows)
>From Vintage BMW Bulletin, Nov-Dec 1991, v19n6
Prolonging the Useful Life of a Lead Acid Battery
by K.L. Martin, B.Sc.(Hon) (London)
Very few lead acid batteries are replaced because they stop working. In
almost every case the battery is replaced because it doesn't work _well
enough_ anymore. What is not generally realized is that something can be
done at this stage which may prolong the useful life of the battery -
quite often by many years, and that the same treatment carried out
earlier in the battery's life may well have stopped the symptoms from
occurring in the first place.
The reason for a battery failing is due to the chemical processes which
take place in each cell when the battery is not fully charged. Even the
slightest discharge condition allows both plates to react slowly with the
sulfuric acid electrolyte to form lead ions. It is these lead ions which
cause problems; they combine with sulfate ions in sulfuric acid to form
highly insoluble lead sulfate. When this coats the plates of the
battery, it fails to deliver enough power to be of use. The battery may
well be serviceable every other way - only the "sulfating" stops the
battery from delivering enough power to be of use.
The sulfating can effectively be removed, or prevented, by adding to each cell
a chemical called tetrasodium ethylenediaminetetraacetate (often
abbreviated to tetrasodium EDTA). This chemical forms co-ordination
compounds with many metal ions, including lead ions formed in the
discharge cycle of a battery. The compound formed by lead ions and the
EDTA ion is not particularly stable in the acid medium of a battery, but
when it breaks down again any lead sulfate regenerated tends to drop to
the bottom of the cell where it lays harmlessly since it doesn't conduct
electricity. Any regenerated EDTA ions are free to continue their work.
This is likely to occur if the motorcycle is used just for short trips, is
infrequently used, or has at any time suffered from an inefficient
charging system. Treating with the chemical can also help keep an
original battery in use, and can help in bringing back into use a stored
battery. It is also a once-only treatment, lasting the life of the
renovated battery.
(end of article)