Re:  screeching
Steve,  your symptoms surely do sound like belt slipping induced by a much
higher charge rate causing the torque required to spin your alternator to
exceed the belts ability to spin it.   In other words, check for a loose
alternator belt.  If it seems tight enough, give it a small belt dressing
treatment to increase its coeficient of friction with the drive and driven
pullys.  Slipping belts "sing" and their music is commonly decoded by humans as
screeching.

John