Hi Steve,
About the square wave business,
No i don't believe it makes any difference.
The only way i know of to deal with the sulphate build up is to take
the battery apart and physically clean the plates.
Also i don't think that its just sulphate build up, i think that the
'dosing' or 'doping' of the plates to give them a preference for
negative or positive, is also affected and deteriorates, why i don't
know.
Cleaning plates these days has to be done carefully, they are no
longer made of sheet lead, it is now a form of pressed granules like
a biscuit, this gives a greater surface area, and improves maximum
discharge current, but also makes them physically weaker so that the
separators are now also part of what keeps everything in place.
Cleaning the battery plates is a last resort when all else has failed.
Most batteries are not made in a way that they can be easily taken
apart and put back together. If i do this i generally do it with the
battery upside down, after separating the casing, usually by physical
damage to the fixing around the top. I would rather do small damage
to the top than to the casing, as i have never found a satisfactory
glue to use for repair to a damaged case, but around the top, pitch
will usually be ok.
Best of luck, and please keep me informed as to your progress,
Regards, John