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Message: <blockquote data-quote="Herbert" data-source="post: 739209" data-attributes="member: 18029">You need to register the new battery to the ECU.  Please read the following relevant info obtained from another international forum:"The reason of the battery registration is that BMW uses an "intelligent" alternator variable algorithm that monitors the battery condition (charge, rate of discharge, etc) and simply shuts on and off depending on this condition. That reduces engine load thus increasing efficiency -power and economy.When you replace the OEM battery you in fact are not telling that algorithm that the battery adapted values stored so far no longer apply -they were collected over a period of time from the old battery condition. So the "old" algorithm continues to do its job although the variable values changed. This could either under/over charge your new battery just because its charging/discharging characteristics not necessarily will have to match the old battery's.So the sole purpose of the battery registration is to update that algorithm to the new values, by starting over the collection of adaptive values from the new battery so it is charged/discharged exactly -or close to it- to its most particular efficient capacity. Sometimes it seems that the battery registration was not necessary when there are no problems with the new battery install. That's most probably due to the new battery condition pretty much matching the current alternator algorithm and that you are not asking too much from that battery... in other words, just luck. Sometimes it really messes up the new battery after awhile as the current algorithm keeps the battery under/over its real capacity. "</blockquote>

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