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I have seen this topic covered somewhere, but I could not locate it today.

1. Connect a trickle charger thru cigarette light.
2. Disconnect old battery.
3. Install new battery.

Does that eliminate any potential for resetting some of the options?
Does the trickle charger stop working when you disconnect old battery?

Am I smoking something? Literally or figuratively.
 

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I don't think a regular charger will work because they are normally half wave rectifiers. You would need a full wave rectifier. Use jumper cables from another car or battery. Careful when removing the cables from the battery in the car so you don't ground out the positive cabvle.
 

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I don't think a regular charger will work because they are normally half wave rectifiers. You would need a full wave rectifier. Use jumper cables from another car or battery. Careful when removing the cables from the battery in the car so you don't ground out the positive cabvle.
+1 jumping it would be a good idea. can even be a 12V battery from a kids toy (big toy like rc car). just needs enough current to keep the computer running ... though a car bettery is best. you never know what the stupid ecu might think when it detects a different current, with an older car it would not be an issue :dunno:
 

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Good thing is you can hook the jumper cables up in the hood and you just have to make sure when you swap the battery in the trunk you don't ground the leads. I did it and it worked fine.
 

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Auto zone sell a small plug that plugs into your cigarette lighter and the other end hooks up to a 9 volts battery. It is less than $5.00.I used it and it works great. Hope this helps.
 

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I don't know how it can work unless you leave the key in the on position (which is a bad idea). In the BMW, the cigarette lighters are disconnected from the power source when you turn the key in the off position.
 

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I just swapped out battery on a 2007 550i and did not connect trickle charger or another battery and it kept all settings (radio presets, etc) so i don't think you need to do this. It will lose date/time/MPG.
 

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I don't know how it can work unless you leave the key in the on position (which is a bad idea). In the BMW, the cigarette lighters are disconnected from the power source when you turn the key in the off position.
Not on my e46 M3 or e36 328is as they're always "hot"...
 

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Good thing is you can hook the jumper cables up in the hood and you just have to make sure when you swap the battery in the trunk you don't ground the leads. I did it and it worked fine.
That is a great idea! Live and learn....
 

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My e46 was "hot" also when the key was removed. I also remember that in an e46 that even if the battery dies, the computer in the car holds the settings for like 30 minutes.

You should be be able to change a battery in 30 minutes.

I have also heard that you have to have an e60 reprogrammed after a battery swap? What needs to be programmed?
 

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I believe only if the battery is of a significally different size i.e. amp hours or cca's. I believe that the voltage and/or current regular needs to be reprogramed for the new battery rating so that it does not become over or under charged.
 
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