battery not holing charge on 1990 Cadillac DeVille

A few months back i had battery replaced. Within weaks of replacement couldn't start car. Had to get a jump. after jump ran car engine to charge battery. after about 15 minuets the engine stopped and i could not turn it over with the key in ignition. On the dash the light went on for the battery not charged.

2 answers
Have the alternator checked.
You'll want to get the charging system checked out, and the battery as well. Either the battery, alternator or the wiring can cause this problem, so have a shop run a quick charging system check, should charge about half an hour to diagnose this.