I'm a newbie. I put a new battery in my 57 drove it around for less than 20 minutes, turned the car off and then needed a jump.
Why?
Background info.
This happened on the first drive after I dug the car out from the grave.
I put in a pertronix ignition switch.
I would suspect that your new battery was not properly charged by the supplier of the battery. A new battery should operate the car (with no accessories like a/c, etc.) for at least two hours. I would drive the car back to the battery supplier and ask them to check the battery and the charging system. (simple test - should take less than 1 minute).
Let me define "new". Something I should of mentioned. I bought the battery late last year and have since had to recharge it. How does this effect things?
It all depends on how the battery was stored. If the battery was stored in a very cold area that could cause the battery to have problems. I would suggest that you charge the battery and then perform a specific gravity test. You should be able to buy a tester at a good auto parts store for under $5-10.
I would also suggest that you test the charging system of your car with a voltmeter. I am no expert with batteries, but these are some good suggestions.
Does this problem have anything to do with the generator? Or is that impossible to tell from the forum?
Recharge your battery, fire it up,then while its running carefully remove the positive cable, if it dies its not charging.