Originally Posted by Bartman619
battery may need to be registered because it's not charging properly. the original battery was an AGM type and needed to be set up correctly with the ECU. you said you bought the battery at autozone, which leads me to think that the battery was non AGM and not registered. it's ok that its non AGM, but not getting the battery registered poses several problems. the ECU thinks that the new battery is the old one, and may be charging it to a different amperage and maybe not enough to keep its cold cranking amps. if you can find an independent BMW garage which can register your battery, it will be way cheaper than doing it at the dealer.
Why do you think the original battery was an AGM?
While registration is needed, what is more likely that something went wrong during the installation. These cars aren't like the old ones where you have two fat indestructible cables; our cars have very fragile electronics built into the cables that are frequently damaged if you just jank on the cables to remove them from the posts.