Does this sound like I need a new 12v battery?

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imchrisd

Member
Joined
Feb 5, 2023
Messages
12
Location
Mesa, AZ
Here's what happened to my 2016 REx...

A few days ago, I was programming the home link on the mirror and I had to turn the car off and on several times. When I pulled it into the garage, the check engine light was on. I drove it for a couple days because I wasn't using the gas engine and last night I plugged it into charge at about 55%. This morning I came out and it's completely dead. Nothing turns on and no lights come on when I plug in the charger.

Sound like time for a new battery or something more serious???

Thanks in advance, Chris
 
You almost certainly need a new 12 V battery, especially if the current battery is the original. If you have a 12 V battery charger, disconnect the high-voltage disconnect to the right of the frunk box, attach the charger to the battery, and see whether it will hold a charge.
 
There is a BMW Service Information Bulletin for replacing the 12V battery:

"SI B61 21 010 Remove and install (replace) 12V AUX vehicle battery"

You might be able to find it with a bit of searching but BMW has recently cracked down on sites that republish their technical documents, unfortunately.

There are a number of videos on YouTube that show how to do this. Having an app like BimmerLink will allow you to inform your i3 that it has a new 12V battery. The process is called "battery registration" and is more important for ICE BMWs versus the i3 but check it out in your searching.
 
Thank you to everyone who replied. I did replace the battery and it solved the issue. I was able to get one at the Stealer for $180 which is about the same price as the mail order one with shipping.

I reset all of the many errors with Bimmerlink but still have a Check Engine light with these errors:

09 Range extender motor electronics
1 error
117000: Fuel tank pressure / temperature sensor circuit: Malfunction or open circuit

1D Hybrid pressure refuelling electronic control unit
1 error
D04C1E: Sub-bus failed / tank pressure sensor does not respond

So goes my next project...
 
imchrisd said:
09 Range extender motor electronics
1 error
117000: Fuel tank pressure / temperature sensor circuit: Malfunction or open circuit

1D Hybrid pressure refuelling electronic control unit
1 error
D04C1E: Sub-bus failed / tank pressure sensor does not respond
I don't have a REx, but I believe I recall reading that BMW has extended the warranty on the fuel tank pressure sensor which has failed for many REx owners. If true, a BMW dealer would replace it at no cost. Hopefully, a REx owner will clarify and correct.
 
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