There are a number of items in the X3 known to NOT shut down when you turn off the ignition. For me - it is the stereo head unit. To test if this is your issue make sure you turn off the stereo manually before ignition off for a while. See how you go = especially if parking for a long time period.
Originally Posted by peter_cd.cn
My changed at a local auto shop. Bought an aftermarket battery. The battery match and over achieved the factory requirements, but now the battery will die if I don't drive the car for more than 1 week. Checked the battery condition at multiple repair shops, and passed check.
Don't know why...
I suggest you find a dealer to do this.
If no difference then search this forum - there are a few causes for excess drain on the battery when the car is "supposed" to be off.
X3 3.0d 2006 (MY07)