I just inherited a 2006 BMW 325i sedan from my sister a couple of weeks ago, she told me she had had trouble with the battery dying on her a couple of times before giving the car to me and over the course of the last 2 weeks I have been having more and more difficulty starting the car. I came across this thread and it seems that by in large the folks who have posted that they did not need to register their new battery and everything was fine either got a replacement OEM battery from the BMW dealer, or an OEM spec battery from the auto store, which would make perfect sense seeing as how the computer would still be telling the alternator to charge the battery properly. But any battery that has different spec ratings from the original would seem to need to be re-registered to work properly. I called around to various independent shops in my area and two of them said they have never heard of the adaptation reset, one said that it definitely needed to be done (yet ironically was cheaper than the others--$55), and another said it definitely did NOT need to be done but told me if I really wanted it done they would do it for me free of charge. Makes me really wonder if I should trust my car to a supposed expert BMW authorized repair shop that didn't even know this needed to be done on a different-spec replacement battery.