When you check at the battery terminals with voltmeter, it should read more than 12v that means your generator/regualtor is working fine. Did you check how many amps you generator is pushing. Atleast 30 AMPS you need I believe.
I asked this question before and never got an answer, is there such a thing called 12V or 6V generator. I had the same problem but I switched to Alternator because I may put AC later
Ganesh
