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      03-23-2009, 09:44 AM   #1
paulcurtis
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Battery disconnect

Hi all,

I've not found a definitive answer for this yet, so im hoping someone can help.

If i disconnect the battery (key out) then what will I loose when the battery is reconnected?

Do systems need to be initialised?

The car radio unlocked? (I have no idea what the code is, the car is 2nd hand)

just wondering before i do it!

cheers
paul
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      03-23-2009, 10:44 AM   #2
FotiosF90M5
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the ONLY thing you lose it the time and date. i think mpg and that sort of thing too.
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      03-23-2009, 12:39 PM   #3
F104
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Quote:
Originally Posted by fotios335i View Post
the ONLY thing you lose it the time and date. i think mpg and that sort of thing too.
indeed that's all you loose. Do not disconnect the battery while the light in the starter button is still on, the ECU will be pulling 4 Amps while the light is on (about one minute). Then current draw drops (forgot to how much) and after 30 minutes from closing the door it drops to 40 milli-amp or less. So best is to take out trunk light, leave trunk open, close door, wait 30 minutes, and then disconnect it
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      03-23-2009, 12:48 PM   #4
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I just disconnect it...lol
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      03-23-2009, 04:06 PM   #5
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Active steering will need to be initialized.
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      03-23-2009, 04:46 PM   #6
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Quote:
Originally Posted by F104 View Post
indeed that's all you loose. Do not disconnect the battery while the light in the starter button is still on, the ECU will be pulling 4 Amps while the light is on (about one minute). Then current draw drops (forgot to how much) and after 30 minutes from closing the door it drops to 40 milli-amp or less. So best is to take out trunk light, leave trunk open, close door, wait 30 minutes, and then disconnect it
Aha! So THAT's how the dealership can get away with charging an hour's labour for a thirty minute job.
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      03-23-2009, 04:50 PM   #7
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Quote:
Originally Posted by F104 View Post
indeed that's all you loose. Do not disconnect the battery while the light in the starter button is still on, the ECU will be pulling 4 Amps while the light is on (about one minute). Then current draw drops (forgot to how much) and after 30 minutes from closing the door it drops to 40 milli-amp or less. So best is to take out trunk light, leave trunk open, close door, wait 30 minutes, and then disconnect it
whats the reason for doing this. im curious. thanks
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      03-24-2009, 02:08 PM   #8
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Quote:
Originally Posted by fotios335i View Post
whats the reason for doing this. im curious. thanks
A charging battery gives off explosive gases, whilst under load the disconnection will draw an arc and could ignite causing explosion. As the battery is in the boot BMW vent the battery via a small pipe to under the car. It is just good practise to dissconect this way.
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      05-15-2009, 04:21 PM   #9
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Originally Posted by SoCalTech View Post
Active steering will need to be initialized.
How does one go about doing this? Can I do it, or do I need to take it to the dealer?
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      05-15-2009, 08:42 PM   #10
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Dealer only.
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