I had em light on now and again,charged when it wanted to etc etc. I run an earth cable direct from the battery to the body of the alternator. I used one of the three or four(cant remember) 8mm bolts to secure the earth lead at alternator end.
Buy an earth lead from the likes of halfords with a ring both ends about a ft or so long and bolt it on. It cant do any harm.
My only worry is you may need an ecu reset