I just bought my third deep cycle marine battery in three years for my Rockwood Fifth Wheel. They keep going dead. I bring them indoors in winter and keep them connnected (plugged in) in the RV all ...
Need a voltmeter to verify charging. 13.2 to 14.6 is charging. Steady 12.6 or less is not charging.
If it is a WFCO... get a different brand. Progressive dynamics, Boondocker, or IOTA. You do not need anything big... 35 to 45 amps is fine plugged in with a single battery.