Removing the spare with the straps is going to be fun. Either read your owners manual on how to do it...or pull up the video on YouTube that shows how to remove the spare to access the battery.
As mentioned above, if you have SLS...then you'll have to remove the dome/cover over the air thingy (I think its 3 or 4 nuts holding it down).
X5 Battery Replacement E53 DIY Full Replacement Procedure - YouTube