2001 Expedition battery light came on and truck died. I had the alternator checked at NAPA and they said it was good. I bought a MAXX battery at Wal-Mart with a 850 cca rating. Worked fine for 1/2 hour then the battery light came on and stayed on. It is a steady light. The battery guage stays in the middle. The truck starts fine. When i put the alternator back on, I lost the brass nut that holds the wire coming from the battery to the alternator. I put a regular nut on in it's place. What is the reason the battery light is staying on? Could it be a loose belt? Thank you for the help.