Battery bank cell failures are an expensive annoyance, but there's an easy way to fix them! All you need are a reciprocating saw, hammer, and pry bar. Simply cut open the battery, and use a butter knife to pry the shorted plates apart, then superglue the case back together. Good as new!
APRIL FOOLS and DO NOT TRY THIS AT HOME!
There is no way to repair a shorted battery cell.
In these photos, my students found a ruined battery by performing specific gravity tests, and we decided to turn it into a "cutaway" battery for classroom visualization purposes. The procedure was to drain the electrolyte into a bucket, then slowly adding this to half a bucket of water while slowly stirring in baking soda to neutralize the acid. Then flush the battery interior with lots of water before cutting into it.