Put one of these guys in "Charge Wizard"
http://www.progressivedyn.com/prod_d...ge_wizard.html
and it will monitor and float the batteries when they are charged and avoids overcharging. I put one in 2 yrs ago and have yet to need to add water. Stays full. Easy to install, plug into the converter and thats it. Cheap too. Check CW.
Cheers,
Bill