If you have to add a bunch of variables and add situations to the original statement to make yourself right then you were never right.
A bunch of variables"? You mean like
"a car audio system"? My "bunch of variables" speaks directly to your question.
Here's what you wanted to know, in case you forgot:
"tell us that the battery is what runs the car stereo in a running car"
Answer the questions:
When the power draw of your system exceeds the alternator capability in that running car, what powers the system?
If your alternator is a 200 AMP unit but your system is drawing 400 AMPS with the car running, what happens when you disconnect the battery?
If you haven't finished your "build" yet, answer the questions for anyone's system that may have the specs I describe.
But, maybe I'll save you (and the rest of us) some time from your filibustering, spin, backpedaling, tapdancing :
My real-world examples within my questions show that the battery indeed DOES run the system in a running car. The alternator is there to keep the battery charged, and delivers amperage AS NEEDED.
A car will start and run without an alternator. A car will not start and run without a battery.
I'm sure you'll filibuster anyway, and if you do, remember to find an example of taking the battery out of a car and being able to start it and run it on just an alternator. Go to any resource you can find regarding how a car actually works, and do some learning.
For extra credit, tell us what the stereo system in a Tesla is powered by: battery or alternator?