I spoke with my service advisor today. He said that on my '07 328i without iDrive, I should not need to register the battery upon changing it as long as there are no warnings posted (which there aren't). You can check for warnings by moving the thumb switch on the turn signal lever to "CHECK" and pressing the button at the end. IF "CHECK OK" is displayed, you are good to go.
As a failsafe, I took the car to an independent servicer that I trust and they scanned for codes and found nothing. They said that if my windows and sunroof were worrking fine, then nothing needs to be reset. They also said that normal system voltage is 13.5 to 14.0 volts. My battery was out of the car for 2 hours before I found a new one, FYI.
Hope this helps.