Does anybody know about battery drain on a BMW 650 I convertable !!!!


Asked by Jul 17, 2012 at 09:18 AM about the 2006 BMW 6 Series 650i Convertible

Question type: Maintenance & Repair

15 Answers


With information given its hard to say what you have going on there. One of the best ways to trouble-shoot a discharging battery is to use the fuses. This way you can eliminate one circuit at a time. Also be sure to keep the top of the battery clean. Current can leak across the top of a dirty battery and cause a slow drain.

1 out of 1 people think this is helpful.

Would need more info on situation to help with this question. How do you know the battery is being drained and is the battery orginal to the vehicle? Is the battery an AGM or lead acid battery?

2 out of 2 people think this is helpful.

Battery is new . An acid battery.Drains over a 3 or 4 day period of time.

4 out of 4 people think this is helpful.

If you have any suspect accessories you can pull those fuses and narrow it down to one circuit and then trouble-shoot that circuit.

You will not be able to diagnose a battery draw in your 650. You cannot start pulling fuses. There will be codes stored in your cars computer system which will give a highly qualified technician a start at working on your draw. It is very difficult to find out which of your coputers is not going to sleep properly. There is no way that you can do it as a do it yourselfer. The cars computers are designed to shut systems off that continue to draw power after the car is shut off and will shut them off. You must ave a discrepancy in a computer for the car to continue to draw. This is going to take trouble shooting the CAN bus network in your car. If you have pulled fuses you need to disclose that to anyone working on the vehicle as you have now set numerous fault codes and errors into your computers. An OBDII scanner will not be of any help in diagnosing this issue.

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Yes you do have to use common sense on pulling fuses. I'm talking things that are inconsequential to the diagnostic and emissions network. Examples would be brakes, courtesy lights, power windows/locks. NOT any part of the control or diagnostic electronics. Any circuit protected by a fuse is inherently susceptible to an open circuit and will not damage any other system.

You are not understanding. Every circuit in that car is controlled by a computer. It is not possible to pullk a single fuse that is not controlled by a computer. If a compoinent is left on or stays on the car will turn it off. If you have a battery drain a computer that is controlling the circuit will have to have stored a code that it turned something off that was not going off by it self. For example if you leave the doors open the car will over ride the lighting input store a fault code that it has done so and your battery will not drain. There is are power management computers that control power to all fuses. Pulling the fuses will not damage the circuits but will add hundreds of dollars to the diagnositic cost of repairing the vehicle as you will have added multiple failure codes in multiple systems in the car and make it impossible to sort out the real problem the car is having. Pulling fuses will not be of any help just cause a diagnositic nightmare.

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Your post made sense so we tried this on my friends 650. We pulled fuses on some circuits to see what happens. Pulled several different fuses such as courtesy lights headlights radio power seats power windows power locks etc. It did bring up a code, but when we replaced the fuses the code went away. Then I got thinking that there should never be a drain on the battery if the computer shuts any drain down. Also on her 650 the radio has blown fuses before, she said, and there was never a code....... I'm not trying to argue with you I'm just telling you what we found.

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Typically the drain is in te computers themselves. A simple light would kill the battery overnight. Taking a couple of days indicates that a computer is not staying asleep and is waking up from time to time for some fault. Even thoght the pending fault is going away when you pull and reinstall the fuses. The code record will still have them. If you are tracing a fault in a slow battery draw te code record is where you are going to look. The car stores these codes forever unless they are accessed and cleared. For example every bulb that ever burned out will be stored in the lighting module unless the code record is cleared.


Any idea how much current the computer draws when it is working?

We are not talking about a computer. There are at least nine and other control units that are not directly called computers but are. The problem is going to be that one of the computers or control units is coming back on after the car is shut down. The power management computers will monitor circuits that shut down and shut down those that do not shut down in the appropriate time. You are not going to be able to simplyu monitor the milli amp draw and find the problem. Something is coming back up after the car has shut down and waking up one or more of the computers. We run into this all the time. It is very complicated.

1 out of 1 people think this is helpful.

the convertible on 650i sport will not go to its upright posistion . it has stopped at 90% and will go no further . i hear the motor still operating but nothing is happing?

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anybody have an idea?

1 out of 1 people think this is helpful.

Go to There is an easy fix in the 645 section. One way to keep a battery drain at a minimum is to lock the car and make sure you keep your key at a distance of about 20 feet away. The key proximity can keep a lot of stuff going if it's unlocked. Locking puts the car to sleep immediately. Hope this helps.

1 out of 1 people think this is helpful.

Actually BMW's in that era (I have an '06 650i' drain the battery if the doors are not locked since sub systems keep running otherwise. Mine does the same thing.

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