As I said above, that’s exactly the problem I found and fixed:  loose connection in the voltage sensing cable for the alternator.   But the latest is that the alarm came back on last night after 8 hours on shore power with the 60 A  Charger.  So now I’m retesting the batteries (maybe they got damaged since the last test) and looking for a loose connection in the 60A charger circuit.  The fun never stops with these complicated boats .....