4 Wheel Drive/SUVs: battery drain, cadillac escalade esv, cadillac escalade

Question
Hello i have a cadillac escalade esv and i started having problems about the battery going dead i took it to get the battery and the alternator to get it check and they said everything was working correctly so i dont know what can it be sometimes it goes dead over night and sometimes it takes half a day and the truck wont start.  

Answer
Alfredo, it can be something very simple that is running down your battery, they make a tester that you can hook on your battery to see if you have a drain, than you pull each fuse out one by one untill the light showing the draw goes off , thanks ADAM