Battery maintenance

I brought home 2 ragrats yesterday, found the lights were on a few hours
later. Then I took battery home and put it on the charger.
In the morning it was still trickling a little under 1.5 amp
(and the "charged" light was never on)

So I pulled the caps off the 6 cells to check the elctrolyte level
(since I could never tell from the side what the fluid level is)
it seemed like a little low even though I could not see bare plates
in any single cell.

So I dumped what seemed like a pint of distilled water among 6 cells
(and now am having second thoughts).
that water level is probably level with the bottoms of the caps.
Which is probably too high.

I suppose the vent is there to get the fumes out, not to let the excess
electrolyte level drain and battery to "self balance", is it?
(the syringe is missing, I wonder if I put it on when I will have
installed the batter a year or two ago)

What is likely to happen due to what's probably now a somewhat
overfilled (12V lead acid) battery? tnx