[Chuck v]

Scott,

Yes it sure points to your present house batteries as being end-or-life. Can you see any date codes on them? Most auto supply stores will be able to check a battery for pass/fail...but often this is based on CCA which is not an important parameter for your house batteries (but crucial for your engine cranking batteries...) If the dealer's shade tree mechanics found 12 volt batteries that would physically fit where the 6 volt ones were originally I would doubt they would have the capacity you would want in a house battery, but they would get you through your remodeling. You need deep cycle batteries in this location.

The 9180 is not the most sophisticated of float chargers, so your electrolyte levels in the house batteries may be low (or have been for some time in the past if the 'dealer' just topped them off recently -- this could be another cause of failure of the house battery charging and use you are observing.

Lastly, on my Magnum inverter there are several programming choices for battery chemistry types (flooded lead-acid, AGM, Gel-Cel, etc.) as well as the capacity of the stack so it can choose how aggressively and to what terminal voltage to charge and maintain things. I suspect that the Xantrex is similar as I recall... You will want to get the 6 volt 220 amp-hour cells renewed as soon as you can.

Chuck