How do you replace the battery on a 2002 BMW X5?

Answerlook in the trunk area, it's on the top left side of your spare tire (viewed as if you're opening the trunk sliding floor board). Rememeber to disconnect negative first (it would be either 12 or 13 mm open end wrench). disconnect positive then pull out battery. Installation should be the reverse of removal. sd330i/02e46/95e34/94e34/02e53.

There is a thread here with pictures and a full tutorial on how to change the battery.

http://www.bimmerfest.com/forums/showthread.php?t=2647

remove the spare tire. it is at the very bottom underneath the tire and a metal cover.