The battery light comes on at high rpms on a 2004 Expedition what up?

Check the Belt Tensioner All engines use an automatic drive belt tensioner. On the 7.5L engine, there are two belts; one uses the automatic tensioner, while the alternator belt requires periodic tensioning. On all belts using an automatic tensioner, no adjustment is necessary because the tensioner adjusts for belt wear. To adjust the tension on the 7,5L engine alternator belt, loosen the adjusting bolts and rotate the alternator until the proper tension is on the drive belt and tighten the adjusting bolts. It is recommended that the belt tension indicator mark be inspected with the engine OFF at 60,000 mile (96,000 km) intervals. If the wear indicator mark is out of specification, the drive belt is worn or an incorrect drive belt has been installed. The 4.6L, 5.4L, 6.8L, all have one belt and one belt tensioner. Look at the diagram on top of the radiator or somewhere in the engine compartment. Also, Check your alternator