A belts sole job is to transfer the power / torque from the crank pulley to all the accessories and it does so through the wedging force of the belt and correct belt tension placed on it by the tensioner. Belt squeal or noise usually indicates loss of tension in the accessory belt drive system. This loss of tension can come from a couples of different areas and I would begin with the tensioner if it has one, replace it if the vehicular has any age. Secondly material loss in a belt can cause a similar problem. If the belt is squealing it is creating heat and losing material which means it is no longer griping the pulley. A belt is made similar to a tire (you replace those don?t you from wear?) and just 5% loss of belt material will create a loss of tension /grip as well. As mentioned high amperage alternators place a tremendous load on the system. A slipping belt from loss of tension will also facilitate pulley wear. Once that happens, though difficult to detect, you must also replace the pulley as well.
To end I will say that a slipping belt is the worst thing that can happen to today?s belt system. If it continues, it creates a tremendous amount of heat as it slips that travel into the bearings. It can also create false engine codes and the accessories such as the alternator or A/C may be operating at a diminished output.
? Remove belt, inspect and clean all pulleys with soap and water or alcohol based brake cleaner
? Replace belt and tensioner together
Hope this helps