Actually a 2008 650i -- battery trouble?

SOURCE: Engine suddenly dies, all electrical goes out as well

Sounds to me like a poor battery cable connection. I am not familiar with the BMW cable routing but it should be simple enough to follow and repair.

First disconnect the negative cable from the battery and leave it disconnected until the final step.

Dicsonnect the positive battery terminal, clean the battery and cable terminal with a wire brush or light sand paper. Apply some dieletric grease or light coat of chasis grease and reconnect the cable to the battery. Follow the positive cable and do the same procedure to all connections down to the starter. Along this route you may notice a smaller wire connected enroute with a fusable link or fuse. Make sure to check these for loosness and or melted wire coating this can be a sign of a loose connection and your problem.

With the positive cable connections completed and reinstalled. Do the same to the negative cable, remembering not to reconnect the negative terminal to the battery until the very last step.

Sorry I don't have more knowledge of the wiring on the BMW.

Hope that helped.
Good Luck

SOURCE: malfunction indicator lamp

possible o2 sensor heater intermittent failure..try warming up the vehicle and see if it goes off ...high rpm right after start up with a short fast run to the store or something like that couldve caused this bank 5 malfunction...

SOURCE: 5 series Battery drain.

Hi, you will need to remove the passenger side kick panel under the dash then you will be able to see the side of the heater box, you should be able to see a black milti plug with a 2.5mm red and white wire, if you unplug this you will see the casing for the resistor, this just un clips from the heater box and remove, replacement is just the reverse, hope this helps or if you get stuck just ask for more help, mark.

Testimonial: "thanks for all the help."

SOURCE: My 1998 BMW 328i SERIES has a brand new battery

Firstly nice car.

It sounds like the alternator could be giving you hassle and the battery is not charging as you drive it. Two easy ways to check this 1. drive your car close to a wall at night and rev the engine with the lights on, if the lights dim then the alternator is nackered. 2. If you have access to a voltmeter check the voltage on the battery with the engine off, then turn on the engine and get some one to rev it. If the alternators working then the should only be slight movement in the voltage if not it will drain heavily (5-10 volts)

To reset the check control light turn the key in the ignition to as far as all the lights in the dash come on (dont start it) leave it in this position for about 2 mins (the car runs its own diagnostic check) then turn it off take out the key and put it back to the dash lights on position again.

Hope this helps.

SOURCE: 2003 BMW 325xi won't start, dashboard and radio go on.

My 2003 325xi died on the highway a few weeks ago, and I thought it was the battery. It turned out to be the alternator, which was an expensive problem to repair. If your battery is new, it could be the alternator, or a problem with the electrical system. I find the BMWs to be too complicated electrically, which often leads to problems! I'd check your alternator...