I have a 2014 Winnebago sightseer. Chassis battery is only a year old and fluids are full. I have shore power(50amp) plugged in. However, if I leave unit unattended for a period of time(Still plugged...
I did two things to address this problem: 1) I replaced the original flooded battery (the factory tag was still on it) with an AGM; 2) I bought a Coleman smart charger from Newegg on a flash sale for $14, and I keep it attached to the battery while my rig is stored. I also keep a lanyard on the steering wheel to remind myself not to start the engine with the charger attached, lest I fry yet another battery charger. HTH