Oliver Collectors

I made it to the 2011 Badger Steam and Gas show in Baraboo, Wi this year with my 1964 Oliver 1800 &quot;C&quot;. I had a great time, but had to jump the battery on my tractor each day.
The batterys are about 2 years old, two six volt x 2= 12 volt system. The regulator is new and the generator appears in good condition (Clean, good brushes, wires attached, connectors good, belt tight). The positive ground 12 volt system seperates the real mechanic from the &quot;want to be&quot;! What are the best steps in order to check this out so I can get it charging again. The volt meter on the dash says 12 volts, but I think its just the battery reading.

Any help is much appreciated.