1969 Dodge Dart Engine Stutter

Hmm. I turned the car off and came back 15 minutes later. Turned the car on and then turned on the head lights. Started making knocking noises. They went away after 4 minutes running. Those noises were what it was doing before, when it would start to sputter and die.
After it has some time to run, the voltage on the battery goes higher and the knocking goes away. Maybe my battery is bad and it isnt holding enough charge?