I'm not sure. this is what my owners manual says
"Battery replacement
Use approved vehicle batteries only.
Only use vehicle batteries that have been
approved for your vehicle by the manufacturer;
otherwise, the vehicle could be damaged and
systems or functions may not be fully available.
After a battery replacement, have the battery
registered on the vehicle by your service center
to ensure that all comfort functions are fully
available."
one could always call their local dealership or mechanic or BMW to verify...
ok so an update:
yesterday all sorts of bad messages (engine, transmission, etc...) started popping up. i called pep boys and they said "oh yeah, you're supposed to have the computer reset". they meant by a service provider. of course i paid them to install it correctly, but i think they don't know how to do it. essentially, i had to take it to my mechanic to have it reset (Wasn't free - so much for thinking a battery change is easy, even pep boys' self proclaimed "pros", and i could save a few bucks).
so the lesson is, for at least the 2011 X3 bmw, you need to have your battery changed by someone that knows how to reset the computer otherwise it will affect alot more than "comfort" features alluded to in the owners manual. risky to get the battery changed, then drive to the mechanic - go to a place that can do it all for you at one time.
i'm going to have to go back to pep boys to get some $ back, for doing an incomplete job that made me spend $ on a mechanic to fix their mess.