Just changed the battery on our 2011 x35i (with navigation, heated seats). I came across this thread and thought I should add my information here to help others who may find it useful in future.

The car was on its original battery, close to 6 years old, and even though there were no significant signs of stress on the battery, I wanted to change the battery as I had previously been stranded once in my old E53 X5 and didn't want to be surprised again.

I went with the BMW original battery. I called the local dealership and was given the replacement battery part number 61-21-2-353-812 and was quoted a good price what came out to $265 tax included. (included a 10% discount and $15 core charge that I will get back after returning the old one.)

Although changing the battery was pretty simple and I have done it many times on various cars including Mercedes and BMW, since I still wanted it registered I took it to my indy shop that quoted me $80 for registering it or $120 for install/register. For that $40 difference I just had them do the work while I was standing there and $120 later the new battery was installed and registered.

Some notes:

The mechanic unplugged all connectors before taking off the red distribution panel. I asked why, he said if the wires stay plugged in the connectors or the panel can break and cause issues. If I had done the work at home I would have kept everything connected as it was, but he took them off and put them back in afterwards.

After registering the battery and computer still connected to the car, we got a 'passenger restraining system / air bag malfunction' and the airbag red light on dashboard that was not there before. He checked and then unplugged and replugged the small black connector with two black/yellow wires which took care of the problem. (see picture below, the wires that appear just to the right of the + terminal of the battery, the far right end of the picture, connector not clearly shown in the picture but you can see the black/yellow wires).

I will be taking the old battery back to the dealership to get back the $15 core charge. Things look good now after a total cost of $395.

Below are pictures of:

- screenshot of the registration

- My old battery (interestingly enough, the part numbers do not exist in BMWs systems... I provided them to the dealership parts dept and they couldn't find them.)

- My new battery

Attached Images

   

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Currently driving: 2011 E70 x35i , 2011 E90 335d
Previous BMWs: 2007 E90 328i , 2005 E53 3.0i, 2011 F10 535i (6spd manual)