Start with radio, NAV and telematic (blue tooth module). Pull fuses for all of them and start putting them back in one at a time. When you insert one that results in a dead battery, you have your culprit. Had a similar problem after alternator took a dump. New alternator and new battery and it kept dying over night. Parasitic drain turned out to be the telematic that wasn't "going to sleep" like it was supposed to. Removed the telematic and problem solved. Best of luck!