The way to check for battery drain is as follows, get an ammeter, or a DMM that has an ammeter setting.
Remove the backseat bottom and roll down your rear windows so you can access the fusebox without opening the door.
Remove the negative cable.
connect the ammeter between the neg. cable and the negative battery post.
Wait a few seconds for all the electronics and check control to shut down.
There should be a small battery drain that is used for the clock, about less than .03 amps
Anything more than that value....begin by pulling fuses in the front, then rear fusebox while watching the ammeter for a drop in current drawn.
If the current comes down to less than .03 amps you have found the circuit draining the car!
ID and fix circuit accordingly.