John In Detroit said:
Let me phrase it this way.. If a battery is sitting there and the acid gets down to the point where 1/4 inch of the very top of the plates is exposed..... How much damage is there likely to be?
John, Your question cannot be answered without first making certain assumptions on SOC, elapsed time, operating temperatures, etc...
Chances are the active material (the lead paste) is not even exposed yet at the 1/4 inch level. Just the top edges of the plate grid might be exposed so the extent of damage would be nil. (however, any oxidation/corrosion of the exposed area could not be considered a good thing as this contaminant remains in the battery chemistry forever.)
Assuming an actual 1/4 inch of the active material is exposed, (sitting) in a fully charged battery, even accepting the fact of oxidation, the damage would be
extremely gradual and most likely reversed when water is added.
The problem is that this is not how we use our batteries. That same 1/4 inch of material above the level of the electrolyte will not be charged or discharged (through the acid bath) during normal cycles. This allows the wet and dry portions of the plates to heat and cool at different rates, possibly warping and cracking the paste and damaging the battery with the flaked off material. This heat can also damage the separators depending on what material was used in their construction. Assuming no shorts were caused, adding water will stop any further damage. You'll have a tough time proving or measuring any degradation.
(Insert disclaimers here................)
That's the "John in Detroit" answer.
The quick answer is:
Add 1/4 inch distilled water and
FAGIDABOUTIT ;D ;D