My solution - long:
My Winnebago Fuse on the Ford Transit 350 HD chassis had this issue. The Ford engine alternator uses a new Ford Smart Charge technology to charge the Ford engine battery (2 AGM batteries) . However we Fuse owners have discovered that when the Winnebago Fuse House batteries are connected to the engine alternator system, the Ford Smart Charge regulator never drops charge down from its high 14.7 Volt output level. What this means is that all batteries are constantly being charged high rate for many hours a day while driving. This is a good way to cook and ruin nice AGM batteries, including the Ford chassis batteries. I resolved this issue by adding a simple switch to in the battery solenoid circuit that disconnects the Ford 12 V system totally from the House battery bank when driving. The Ford Smart Charge system now drops down to the 13.7V level as it should when the chassis batteries are full and the House batteries are kept safe - my 200W solar keep them up just fine. Same principle could be applied if one changed out the House batteries to another type.
