Most often 13.6VDC charge voltage from any battery charge setup will boil out battery fluids over time. When this charge voltage is reduced to 13.2VDC then the boiling out of fluids is much reduced (if any)...
When you leave the battery connected to a charge source of 13.6VDC you should be checking the fluid levels. I check mine every couple of weeks.
Once the battery fluids get below the cores inside the batteries then the battery may short out internally. This will make the battery start getting hotter and hotter and really start boiling out more fluids.
It is hard to re-cover a battery from these problems.
This is why a SMART MODE CHARGING setup is so important for us. These system will use all of the necessary charging voltages to keep your battery re-charged. More importantly these units will drop back to a 13.2 VDC mode when currents are not being demanded by your system. This charging 13.2 VDC mode is just below the boiling out of fluids level and really saves your long term connected batteries.
I check my batteries on a regular basis using my MULTIMETER and watch the charging voltages coming from my on-board converter/charger unit or connected to the truck charging system when pulling my trailer very close to make sure all is doing what it is suppose to be doing...
ALot of us RV'ers can't afford to keep replacing dead deep cycle batteries where just a few simple measurements on a good maintenance schedule would prevent the batteries from going dead.
Just some of my thoughts
Roy ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS