Battery electrical help Plz

Good Afternoon,

Today i started my Vrs and went two min down the road and all off a sudden my lights dipped and i could hear like a grinding or arc sound at the same time the battery warning light came on the dash board. It will be on for a second then go off then ten seconds later it did it again. then it hasnt happen for the rest of the 5 min jorney.

Therfore for 2 - 5 seconds the battery light was on with a noise in the engine bay and dipping the electrics.

I have run the engine with the bonnet up and couldnt spot anything or notice anything incorrect with the altinator bearing.

Anyone have any ideas

Thanks alot.