Probably been discussed before but can't seem to find anything similar.
Battery charging kight came on and Power steering failed. Had garage change the Alernator and the power steering starting working again and battery charging light stayed off. Everything seemed fine for about 20 miles and then the spanner light came on and then the electric windows and the wipers went slow. Got home and the battery was almost flat. Got the car started and measured the battery which showed about 11.3.
Recharged battery and spanner light goes off and again everything seems fine but battery is not charging even though the charging light doesn't come on and again the spanner light comes on.

Any ideas or tips on probable fault would be much appreciated.