Quote:
Originally Posted by ABMW
Craig, your dealer is mistaken and probably knows nothing about what chemical reactions take place within a battery.
Keep your RPMs above 1k for over 10 minutes per day, and you'll be fine. If you're at idle or not above 1k for more than 10 mins. per day, maybe consider the battery tender.
Most modern vehicles cycle their alternators on and off at specific RPM ranges to lessen the load on their engines, creating smoother idle performance.
I have no idea what BMWs set their alternator to start at, but specifically driving on the freeway, is no different to the battery than idling the car at 2k rpms in the driveway for 10 mins.
The issue at hand is the amount of time spent driving the vehicle at a speed in which the alternator is charging the battery; that's it.
Find a new service advisor...
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IMO Craig's SA gave very practical advice. About the only time a 35d engine is normally running at or above 2k RPM is on the highway.
BTW a 35d
idles at under 1k rpm. In fact, mine idles closer to 600rpm and is rarely above 2k rpm for more than a few seconds unless it is on the highway. So suggesting that a 35d owner could IDLE their engine in their driveways at 2k rpm for 10 minutes to keep thier batteries charged is not very practical.
Funf Dreisig