Brent Regan has made a good point regarding the "desulfation" of lead acid
batteries. There are however reams of information available on the web
written by people far more qualified than I on the subject of lead acid
battery sulfation. I therefore hesitate to engage in technical debate of the
subject. I will however pass on the following which seemed to be the most
understandable description of sulfation I could find. Brent is right, BUT
there seems to be more to "desulfating" than simple charging. See the item
below.

The little chargers I'm offering to the LML readership seem to be moderately
priced while providing something more than a simple trickle charger. If you
have an expensive battery it seems to be a rather small price to pay to
extend its life by perhaps a factor of two or so, not to mention avoiding
the potential hazards of having a battery whose capacity is minimal at the
wrong time.

Ted Stanley


Lead Acid Battery Cycle:
When lead acid batteries discharge, some of the sulfuric acid in the
electrolyte is converted to lead sulfate crystals and begin to coat the
plates. These crystals interfere with and reduce the capacity of the
battery. During recharging operations, sulfate crystals are converted back
into sulfuric acid.

Most, but not all of the sulfates will be reconverted. These stubborn
patches of sulfates will continue to grow and will harden to a class III
bond. If unchecked they will grow to the point of battery failure. Sulfation
is the failure mode of 84% of lead acid batteries that are discarded yearly.

Sulfation on the plates are in three classes in bonding strength to the
plates or grades of difficulty to remove. The first grade is removed by
recharging. The second grade rapidly dissolves with pulsing. The third or
hardest grade (long term sulfation deposits) SLOWLY dissolve with pulsing,
as the chemical bonds are really tough to break.

Equalization charges, while it accelerates the consumption of the positive
plate(s) serve two purposes. First it is a crude and inefficient method of
desulfation. Secondly, it creates gassing in the battery. This results in
the stirring of electrolyte. Without this stirring, electrolyte can stratify
(layer) with the acid settling to the bottom of the case. This condition
will cause the bottoms of the plates to be rapidly consumed and severely
reduce capacity.

An alternative to equalization charging would be to use two different
approaches to maintain the battery bank. Desulfating the plates by pulse
conditioning will ensure the total removal of class III bonded sulfates.
Electrolyte stratification can be eliminated by bubbling (aerating) the
batteries using compressed air periodically. The industry standard when
using alternate battery maintenance methods is to set the charge controllers
to 5% above float voltage levels.