Batteries were disconnected and the disconnects were disconnected. I have been through the coach pretty well, and I can see no place to put additional batteries, particularly any place where they would be accessible. I did not disconnect the battery cable at the inverter - I thought it safer to leave it be, in case it were active. (The running inverter seemed to suggest that.) I didn't relish the idea of being ankle-deep in a narrow bay with a thousand amps of sparking cable.
I think the solar panel output was over 12 volts at over 2 amps, which might be enough to keep the inverter active, based on above. I realize that my cell-phone charger might be enough to make the inverter stop inverting in those conditions.
Must have been the solar panel.
Matt B