md750i

Hello Im In Maryland owned a 2006 750i and now a 2009 535i the best options in Maryland for BMW dealers is as follows
#1- Tisher BMW in Silver Spring MD
#2- Sterling BMW in Sterling VA
I live in Frederick MD and will be driving the 41 miles to Tischer in Silver Spring they are a real good dealership ask for Joe Diss or Kevin Hull as a SA in my opinion the other dealers in the area are sub par at best I and all my buddies drive either benz or BMW as far as Bimmer if we cant do it ourselfs and the dealer is the aboslute last option the two abover mentioed are your best bet for a trustworthy stand up dealer I stamp them both

BimmerFan52

Based upon the reading of 11.9V, either your battery is no longer taking a full charge or you have a parasitic drain source which is draining the battery overnight after you return from your commute.

Confirm the 11.9V in the morning before starting, watch the voltage during the first 15 seconds as the alternator ramps up, and glance at it during your commute to insure the alternator continues to charge at 14.2-14.5V. After arriving at your destination turn the car off and then turn the key to position 2 without starting. If the battery is at 11.9V then the battery is likely bad. If the battery is at 12.4V or higher, then monitor it the same way when you leave work, during the commute home and after arrival, again turning the engine off, and then turning the key to position 2.

If, after driving, the battery is still no better than 11.9V I would go to a national auto parts chain that will test the battery, alternator and starter for free. They will likely confirm that the battery is bad.

Generally if the car starts on its own, charging a low battery will not damage an alternator. However, if you jump a car with a flat dead battery and count only on the alternator to fully recharge it, this can damage an older alternator that is already on the ragged edge.

If you search this forum you will find a number of references to sources and part numbers for aftermarket batteries, which will be in the $110-$160 range. Installation is free. The battery charge by the alternator is computer mapped, based upon the age and temperature of the battery, using an algorithm developed based upon the battery's cell type, starting amperage and age. BMW recommends entering this information into the computer when a new battery is installed to maximize the life and performance of the battery. An independent BMW repair shop will do this for about $50.

Battery replacement by a dealer ranges from $279 (my own case where other work happened to require the battery be disconnected and the computer reprogrammed anyway) to as high as $750 for the battery installation and computer updating at some dealers.

Good luck and post back if you have any further questions.

akgolfpro

Go pick up a interstate H9 battery and find a smaller shop to do the computer work!

gwf545

If after you replace the battery you are still having issues, suspect the voltage regulator which is integral with the alternator. I had a new battery that intermittently would get only partially recharged (it kept showing low voltage when I checked it) with little indication of a specific problem until I started getting all sorts of iDrive error messages from transmission to active steering. I removed and replaced the alternator, problem solved. I believe the regulator was intermittently failing to fully charge the battery then it finally failed completely. The onboard diagnostics did not detect it nor did my voltmeter and clamp ammeter.

scottfrazer

bimmerfan52 with fantastic advice. had the exact same probs. 2 fried cells. put new battery on without coding,went flat because it "thought" it was the old one. got it coded and idrive faults cleared at indi garage.found out why battery had gone south,due to voltage regulator not working correctly. so new alternator and reg been fitted as we speak.

Quarta2six

Got a good Indy Downtown Baltimore dont know if thats to far for you to drive. Idk what I would do without this guy. Also registered my battery when I got it replaced. I've only been to the dealer for an alignment and he told me to go there, NEVER anything else.