Originally Posted by af908
Can someone explain to me what happens if the battery is NOT registered?
I talked to a couple guys i know at the BMW dealership, including the shop Foreman, and they all said registration is not necessary. They did however, say that it only becomes an issue when changing the specs on the battery, where the car has to be recoded to charge the new battery.
The dealer techs were wrong that registration only needs to be done when changing specs (first time a dealer tech has been wrong, I know); it's in their own service guide that registration needs to be performed whenever installing a new battery. Coding needs to be done ON TOP OF that if changing specs. As for an explanation, there are 3 threads going about this, so here's just a copy/paste of what I've already posted in the other 2:
"Registering" is the process of informing the computer that a new battery has been installed, and while failing to do that won't prevent the new battery from working, it IS good to do and CAN make a difference in how the car manages the new battery and how long the new battery lasts. Dealers will definitely overcharge on labor for registration, because if you have a coding cable and the right software the process takes all of 60 seconds. There are DIY threads on this forum showing how to do this.
As for what exactly registering a battery does, the link I added at the bottom of the post shows a description of the process. Registering basically allows the computer to pull the proper amount of current from the battery and manage it properly, which it might not do if it thinks it's still dealing with an old battery.
I had first-hand experience with what happens when you don't register a battery recently with my wife's car. Her Mini Cooper S's moonroof would only close completely while the engine was running; when only the ignition was on, it would come forward but wouldn't pull itself all the way down to make the seal, and it moved much more slowly overall. I suspected the battery wasn't providing enough power, so we got a new one. The indy shop didn't have access to the computer they normally used to register batteries that day, so I told them to give me the car with just the battery and I'd DIY it. I tested the moonroof with the new battery BEFORE registering, and the problem remained, which I suspected was because the computer didn't know it could now pull more current from the battery. Registered the new battery, problem solved immediately.
Screenshot that describes battery registration: http://www.bimmerfest.com/forums/sho...2&postcount=18