The past couple weeks my cars idle has been pulsing from 1 to 2 rpms after it has been running for a while. The last couple days the battery has barely had enough power to turn it over, just barely starting my car. I even tried letting the car run for a while, then shutting it off, then starting it back up and the battery still has trouble turning over the motor. I think that maybe the alternator is going bad and not charging the battery, or the battery itself is going bad, but that wouldn't explain the idle pulsing. Please help me before i have to jump start my car every time i want to go for a ride. Thanks.

when the engine is off, what is the voltage of the battery?
when the engine is running, what is the voltage of the battery?

will help to diagnose the problem. I would have thought it was the battery on the way out