An excessive load from any accessory can cause this.
Check your ground connections too. A slightly loose ground can cause the charging system to operate at full charge, even when it shouldn't need to.
Does the alternator spin freely with the belt off? If it's tight or noisey, the front bearing is probably shot.
If it squeals from the A/C belt (with A/C clutch engaged or not) remove the A/C belt. The clutch pulley should spin freely (IGN. KEY OFF!) If it's balky, the clutch bearing is going out.
Ditto for the water pump. Do you have fresh coolant? Anti-freeze contains a water pump lube in it, and the lube wears out much faster than the anti-freeze. This can cause the pump to squeal or sieze.
How's the power steering oil? Does it spin smoothly?
All four belts on that car run on the water pump pulley. The pump and pulley can take a beating.