two unrelated questions

[jrd1990zr1]

I just took my Z down from the lift and found out the battery didn't have enough juice to start it. Jumped it, started right up. I let it run for awhile to look for a very minor noise from the front of the engine which appears to be the belt tensioner fluttering. I also detect a slight bearing noise. Are tensioners making this type a noise common? I initially thought it might be the alternator but it does not sound like it. Any thoughts?

2nd while the car was running charging the battery I turned the dash lights on to check the charging. I noticed quite a bit of flickering in the interior lights. Does this sound more like a bad battery, or when I pull the plenum should I have the alternator checked out? Any thoughts?

Thanks, John