TechKenny’s first tutorial on how to replace your car battery. *IMPORTANT, READ:
I was not the person in the video so don’t go flaming me, BUT it is highly recommended to have the iDrive reset or keep it powered during the installation of a new battery. Modern BMWs are filled with sensitive electronics including the iDrive system. Going without resetting the computer will be fine for a few years and will cause no problems, but in the long run it is a good idea to do the process correctly.
It would be in your best interest to keep the iDrive powered while changing the battery so that a reset will not be necessary. There is plenty of information on the forums about this but the way to do this is to hook up the jumper points under the hood of the car to another car or battery WHILE you change the battery in the back. This is to ensure that the iDrive system is constantly powered throughout.
When finished, you should also take your car to a local reputable mechanic in order to get your battery registered into the iDrive. This is to ensure that the alternator is programmed to know that a fresh battery was installed and will supply the correct amount of power to it. Good Luck with your installation!