Starting issues, '01 X5

[Drkenigma1]

Ok here' the problem. I was driving home late at night, about 70 miles from home and the "battery light light came on. I was determined to make it home so I crossed my fingers and prayed to make it home. I drove 60 miles and the "X" slowly cut out on me. I removed the battery took it home and gave it a full charge. I had the "X" towed home. The battery took the charge and checked out fine. Ok so it has to be the water cooled alternator. Dealer cost $750. I removed it and took it to a alternator shop. It was dead, so for $300 I had it rebuilt. I installed it along with a water pump and belts. Everything together, fluids filled, no extra parts, and electrical connectors are where they is supposed to be. Here's to problem, it cranks but has rough starts, idles roughly,then dies. No check engine lights or an faults. What is it?????