Car cannot start at all

okmoney · Apr 8, 2022

Background: Car was 100% charged / about 68k miles / 4 years. / Expired warranty

Out of nowhere, it cannot start at all this morning. No power what so ever. Everything cannot be turned on at all including back trunk and front cover. Need to towed the car to a local dealership for diagnose. Before it "died" , I saw a transmission malfunction alert on the dash board. (This is out of the blue as I just had my routine checkup 3 months ago and car ran smoothly yesterday).

Anyone experienced this before???

okmoney · Apr 8, 2022

2018 i3

symonray · Apr 8, 2022

If your car still has its original 12 volt battery, your problems may be caused by a 12 volt battery failure. They tend to fail within 4 or 5 years, and, when they do, the car becomes completely inoperable.

okmoney · Apr 8, 2022

I have the original 12 volt battery. Hopefully that's a quick fix.

What about that transmission malfunction error code? I searched up the forum and nobody mentioned that error code at all.

frictioncircle · Apr 9, 2022

okmoney said:
What about that transmission malfunction error code? I searched up the forum and nobody mentioned that error code at all.

When the 12V AUX battery is failing it can cause all sorts of bizarre errors to appear on the control display.

I replaced my battery with a new one ordered from the Remy Battery site, model AUX18L (the battery is made by East Penn).
https://remybattery.com/start-stop-aux18l-auxiliary-battery.html
Note that East Penn is the OEM for BMW's version of the battery.

Searching for AUX18L, East Penn or Remy Battery should give plenty of helpful posts on this board and install videos on YouTube.

Once you've swapped batteries it's recommended to register it, which is a software process that tells the car that it has a new 12V battery. Searching for "battery registration" will similarly turn up plenty of links.

If you're not already equipped with the tech to do this, you'll need a Bluetooth OBD-II dongle and software like Carly or Bimmerlink.

A new battery, OBD-II dongle and the app of your choice will come to somewhere between US$175-$250 (plus about an hour of your time). If you ask a BMW dealer to do this they'll charge you at least US$550.

I'm certain once you replace the 12V AUX battery that transmission malfunction error message will go away.

okmoney · Apr 9, 2022

That's great info. Thanks a lot.

Anonymous · Apr 9, 2022

When replacing the 12v battery yourself, with one you get from East Penn - make sure that the new battery is fully charged before you do the swap. Many new batteries come under charged, and taking out an old dead battery and putting in a new almost dead battery in an i3 won't solve the problem and may actually make it worse. A $25 - $50 battery charger that will handle AGM batteries is a good investment - will let you both check the health of a battery, and charge it when needed.

Also, registering the battery in an i3, unlike gas BMWs with alternators and starter motors, where the battery works hard turning over the engine to start it, and the charge level is adjusted as the battery ages and that charge level needs to be reset for a new battery, there is no such battery management in the i3. The battery is there to simply boot up the car's computer systems, and turn on the DC/DC converter which then powers all the car's electrics from the high voltage battery (as well as charging the 12v battery). Registering the battery in an i3 does nothing more than record the date of the battery swap, so many don't bother with registration - though an OBD dongle and BimmerLink are handy tools to have to diagnose issues with the car - and if you have them, might as well register the battery.

frictioncircle · Apr 10, 2022

Agreed MKH, a new 12V AUX battery should absolutely be fully charged before install.

Arm · Apr 10, 2022

Honestly the hassle of changing it yourself isn't worth it. Spend the extra couple of hundred dollars and have a dealer do it and have it covered for 12/months, 12k miles under new part warranty/labor coverage. All this jumping through hoops to change a battery, re-program, make sure it's charged, etc.

frictioncircle · Apr 11, 2022

Arm said:
Honestly the hassle of changing it yourself isn't worth it. Spend the extra couple of hundred dollars and have a dealer do it and have it covered for 12/months, 12k miles under new part warranty/labor coverage. All this jumping through hoops to change a battery, re-program, make sure it's charged, etc.

If starting from square one (not having any gear), Arm's suggestion makes sense if you're not inclined to get hands dirty.

Having acquired BimmerLink, an OBD-II adapter, and a battery charger over the past five years it was just wasteful to spend $500+ at a dealer when I could do the same work with what I had on-hand in under two hours. I didn't particularly enjoy doing the labor, but it wasn't hard.

I save my dealer visits for the really painful stuff!

Car cannot start at all

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