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)