Vulcan you may have posted the qustion but the O/P has not responded.
Oh and I see many of you saying 2 quarts of water means batteries are damaged.. yes, might have taken a month or two off their total life.. Two quarts is about the maximum you can add to a GC-2 pair before damage sets in but I would not call them toast based on that.
IN fact I had to add about 2 quarts a year to mine.. that would indicate (At least on my interstates) the fluid level in the battery was JUST at top of plate level.. That is the absolute MINIMUM level without damage.
To the original poster.. There are many convrters.. IF you have, for example, a Magneteck 6300 series power center/converter assembly then leaving the fridge on (or lights or most anything save the radio) while plugged in had no effect on the battery charging.
and the Magnetek is very well known for doing what your convertr did.
The magnetek has two sections.. A converter that powers most of the stuff in the RV when pluggd in, and a battery over-charger that does what happened to your batteries if left plugged in long enough.
MOre modern convrters (Say parallex (Who bought Magntek) 7300 are also not that good at long term charging but still can cuse the kind of damage you describe.. Just takes longer.
Finally we have decent 3-stage converters In the 45 amp range "Multi Hundred Dollar" price tags means someone is goughing you 150 is closer (157 at best converter for a 9245 deck mount)
or if fixing a combo power/center converter you can go with the 4600
http://www.bestconverter.com/PD-9245C-45-Amp-RV-ConverterCharger_p_170.html