Wires

The charging system adapts the charging current over the life of the battery. A new (fresh) battery can be charged at different rates than an old tired one. In the "old days" the alternator just perpetually charged the battery, and nobody cared. For efficiency reasons, the alternator doesn't drag down the engine all the time (IE better mileage), and is cycled during times when charging is required.

Because of this, the car needs to know when a new battery is put in, or it won't last since it's not getting the proper charge profile.

aclass

Wow
It is always nice to learn something new and this one is something I have never heard of before.

ribeye

So, if you don't code it, what exactly will happen?

Wires

You just don't get the same life out of the replacement. How much, I cannot comment. IE 3 years vs 8 years? 7 vs 8?

Weebl

Yeah, it's more complicated than BMW. There you just click on adaptations and new battery, done.
People have just put in new batteries and not coded them with BMW's and nothing "bad" has happened but the alternator will overcharge as stated above. The biggest key was to make sure the reserve capacity and AH were the same and not go cheap on the battery. The alternator is relying on the fact that the battery is the same size and type (AGM/lead acid) to charge it at the optimal rate.
Pulled randomly from youtube.

ribeye

OK, so any garage that is properly equipped can do this. Or even I can do it with an odbeleven.

Wires

Yes, they shouldn't have a problem. My 2008 3-series BMW had to be registered as well, so it's been around for a while (at least in the German brands).

Weebl

+1 for the 08 E90

I used the Foxwell/Schwaben scanner and will do so again.

pal joey

ah the good ol days...pop the hood ,and get very easy open access to loosen the 2 nuts ...drop in a sears die hard, tighten it up, and drop the hood... done

patmurphey

Then try to remember where you put that radio activation code...