What is proper voltage for battery for 1997 Cadillac Deville?

I just had to have a brand new alternator and battery (best one sold - or at least most expensive - at Sears Auto which was the only shop open this weekend when car broke down). At night with lights on the battery ranges from 11.8 volts when at idle to 12.5 while driving. During the day the battery ranges from 12.2 volts to 13.1 volts. I've been told this is too low (especially the night voltage) with brand new alternator %26amp; battery. Could there be another problem?What is proper voltage for battery for 1997 Cadillac Deville?The problem is a defective alternator, they probably got it from auto zone. Take the car back to Sears and tell them what is going on, I am sure they will resolve the problem at no cost to you.What is proper voltage for battery for 1997 Cadillac Deville?as far as i recall these are internally regulated so im quessing thats fine but make sure you dont have a draw somwhere that is robbing power from your system(also try all accesories on and lights on bright a\c on high and all that jazz and see if the voltage goes up or down)What is proper voltage for battery for 1997 Cadillac Deville?Should have about 14.3 to 14.5 volts. You still have a problem. Bad alternator I would suspect.