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bimmaster, BMW Technician
Category: BMW
Satisfied Customers: 1882
Experience:  3 years dealer experience, master bmw tech
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how do I replace and program a battery in a 2004 BMW 745Li

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how do I replace and program a battery in a 2004 BMW 745Li?
Hi, replacing the battery is fairly straight forward.
First you will need to open the right side trunk trim door. Unscrew the red knob and remove the jack.
Pull up the plastic cover to see the battery terminals.
Use a 10mm socket and ratchet to loosen and remove the negative cable first.
Then remove the positive terminal.
Close the compartment door.
Remove the trunk carpet, and floor bottom.
Remove the spare tire.
Remove the wing nut holding the wheel chock, and remove chock.
Loosen the 13mm nut for the battery hold down, and slide the battery out into the spare tire well and out of the car.

As far as programming.
If you are replacing the battery with the same style, and capacity, then the battery needs to be registered to the vehicle using the factory, or bmw specific scan tool.
This is found in service functions under power supply/battery.

If you are changing the battery to the newer style AGM black battery, and the vehicle is not registered for it. You will need to perform a retrofit procedure with the BMW programming system. So mostly only the dealer and very well equipped shops can do this.
It is not really too critical, since alot of people replace their own batteries and aren't aware it needs to be registered.
bimmaster and other BMW Specialists are ready to help you
Customer: replied 7 years ago.

Hello thanks for the quick reply...I have a factory battery in the car and I plan on replacing it with a battery from a local battery shop called Battery Source. Battery Source says they do this all the time with BMW's. The say connecting the car to a backup source, it never loses power therefore registration is not required. I'm a little skeptical but 100$ vs $500 is very appealing.


Will this work?

Registration is not something that is lost when the power is disconnected.
It's merely reseting the computer to charge the battery like a brand new one.
Over time the battery changes, and the charging strategy is changed to compensate.
So hooking it to the backup power supply will save the clock setting and radio stations, but does nothing regarding the registration.
bimmaster and other BMW Specialists are ready to help you
Customer: replied 7 years ago.
Thanks you were very helpful.
You're welcome, thankyou.