1998 Cadillac Concours battery not charging

Ok please help me so I know what it is on my dashboard it says battery not charging it will come on for like 30sec or a little more then go off then it comes back on then off. I have took it to autozone, oreillys, and advance auto parts to check to see if it was my alternator they all said that my alternator is good and said that it was my battery that was bad. So I got a new battery at advance auto parts because I still had a warranty on the old one. After I got the new battery and installing it to my car I drove it around and the damn thing came back on battery not charging. My car does still start up fine and runs good just dont know if I should drive it around like that and get stuck. SO PLEASE HELP ME WITH THIS ONE I LOVE MY CAR ITS MY PRIDE AND JOY!