the knocking you hear is the crankshaft bearing as a ressult of being driven with no oil getting to the bearings.. unfortunately you now have a scrap engine in your car
your Alternator
check alternator belt may be slipping.if the belt isworn or glazed replace it if problems is still there replace alternator.
Usually when the battery light comes on its the Alternator, or a bad wire from Alternator to battery, but id check Alternator first.
Is the battery/alt warning light on? if they didn't disconnect the battery while the starter was being replaced and they accidently shorted the battery cable out it could have damaged the regulator of the alternator some of the Delphi regulators are very sensitive to that, but if it tested normal at the parts place, does it run down while driving or while sitting?
Your battery is weak, or your your alternator is not charging battery.
the battery is dead and needs to be charged or replaced, or it could also be the alternator is going bad
Wires between Alternator and Battery, and between Alternator plug connector and fuse box etc.
Alternator is defective or battery has a dead cell.
Sounds like the alternator is gone.
Not likely.
Don't believe a word AutoZone tells you. My battery died so I went there and they tested my battery and alternator and told me it was the battery. So I bought a new battery and 2 days later, dead again. Went back and they tested again and THIS time, it was the alternator. I went nuts on them and ended up getting both my battery AND alternator for free for their mistake that left me stranded at 12am.
If the engine is running, then no. The alternator constantly keeps the battery charged.