RV Repair: Onan Generator, battery connections, secondary battery

Question
The generator on my '94 Tioga Montara will run for 10 minutes and then stop. With the engine running, the generator will run for 20 minutes and then stop. Any idea of what the problem could be? Thanks for your help!

Answer
Some of the generators require a 12v power source to continue to run.  If this Generator is wired to the house or secondary battery and it is low, that could be the problem, with the chasis engine running, the isolater may be charging somewhat. Check all of your battery connections and make sure they are all clean and tight from the Generator to the battery