So I went to visit the guy at ecorecon and he tells a very interesting story. He does actually chemically clean, renew and recon the batteries to be as good as new. Complete clean of all lead plates inside battery. Using patented solvents. Complete replacement of electrolyte with new, being liquid or gel.
Fully tested over 7 days with charge discharge monitoring to see performance of the battery and warranty of 18 months given.
He has many happy customers over the last few years that are happily using their recon batteries for all sorts of uses, from car, deep cycle to solar.
And just to show prices the 170Ah Northstar solar batteries are going for around R1500, plus you can get a discount if you bring in old batteries but only compulsory for "car" batteries.