1998 deville delegance. I get the occasional "BATTERY NOT CHARGING " message. Today I got it but after I had been driving around on freeway and side streets for about an hour and a half with no problemo, kept my eye on voltage reading and it fluctuated between 12.4 and 14v depending on RPMs. and then parked for about two hours,got back in started it up and got message. I drove about another ten miles or 20 minutes with message still there and little red battery icon lit up and it drove fine. So I pulled into garage, shut engine off, started it right back up, cranked fine and fired up and message and little red battery light was off and voltage seemed normal again, what gives????