My 2001 audi seems to start up fine and but after

i have a 2001 audi a4 and few days ago my car started dying while driving i notice that my battery was drained. after i took the battery to a shop and have them look at it they said it was fine and just had to recharge for 30mins. after the battery was charge above 12 volts my battery started slowly to die again. i had to jump my car bout 3 times just to get home. what would be the problem plz help me :(