Intermittent will not start, battery draining?

Hello,

Does the battery drain when the engine is running or when the car sits overnight?
When does not start, are you able to jump start it?
So, when the engine runs what is the voltage output to the battery?
The alternator should have 13.6V to 15.2V output to the battery.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

If the battery drains overnight then you have an excessive parasitic drain, which could be due to any number of electrical components staying on or malfunctioning. Like a glove box light staying on or a shorted window switch.

Let me know a bit more about what you have been experiencing.
Thank you.