Battery Light Flickering

I started my 97 passat this morning and everything was normal. About 5 minutes of driving later my battery light starting flickering. When i was at red lights, the light was bright and clearing flickering. When i was driving or accelerating, the light, while still one, was extremely dim and hardly visible. What could this problem be? It still starts fine

Mine was worn brushes/commutator in the alternator.

Hook up a voltmeter to your battery with the engine running and see what you get.

Just been there my self and ended up replacing the voltage regulator on the alternator{the part with the brushes), it instantly fixed the problems you are describing here

Sent fra min GT-I9300 via Tapatalk

When replacing the volt reg assembly, take a look at the slip rings. If the slip rings have deep grooves in them, take the alternator to a good automotive electronics shop for a rebuild. Probably only a little over $100 for that. Whatever you do, do not abandon an OEM Bosch alternator for a rebuild from a chain store.

Before you take it to a shop, see if you want to do it yourself:
https://forums.tdiclub.com/showthread.php?t=430807