Huge system failure after charging on 2013 range extender

Today when I took the car off charge at a public charging point, every error imaginable came up. The power steering has stopped working, and there are the following warnings: Driver restraint malfunction, stability control failure, drivetrain no restart, slope too steep for park and gearbox P no longer does anything. There is also reduced power indicated by missing bars on the display. Checked all 12v fuses and no fuses blown.

How old is your 12 volt battery? When that dies, the car pretty much bricks itself, or throws all kinds of strange errors, because the 12 volt battery powers the car's main ECU, it's brain. No or below normal voltage power to the brain, and the car either goes into zombie freak-out mode, or just totally shuts down.

When you plug in the i3 to charge, there is a battery control module that checks the 12 volt battery, and if the charge is below normal, tries to charge it. If the battery was close to failure, that charge attempt could have pushed it over.

The 12v battery is totally fine, it sits at around 12.4v when the car is off. When the car is on, it rises to 14.8v. I've never had any error messages to do with the battery. I also tried disconnecting it to see if the error would clear but that hasn't worked.

I have ordered an ethernet OBD cable and ISTA D so that I can attempt to find what part has went faulty, and order a replacement. It is worth a try before wasting thousands getting BMW to sort it.

Are you testing the battery at the battery terminals, or through one of the accessory ports? If you are doing it through an accessory port, you are just testing the output of the DC to DC converter (which is pulling power from the HV battery pack), not the 12 v battery. With the car off, as soon as you open a door, the DC/DC converter goes on to power accessories, like door locks, and the ports at around 12 volts - but that power is coming from the HV battery pack, through the converter. The 14 volts you are seeing when the car is on, is the output of the DC/DC converter at full on, with 12 v battery charging enabled.

If you are testing via one of the power ports, try testing through the rear cargo area port.

First, leave the car off and locked for at least 20 minutes so all the accessory ports power down. Then just open the rear hatch, and test through that rear port. Supposedly opening the rear hatch does not turn on the DC/DC converter, like opening doors does.

Or just hump the battery down to your local auto parts store and have it tested.

Some of the errors also could point to a bad DSC control unit.

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MKH said:

First, leave the car off and locked for at least 20 minutes so all the accessory ports power down. Then just open the rear hatch, and test through that rear port. Supposedly opening the rear hatch does not turn on the DC/DC converter, like opening doors does.

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On our 2014 BEV with Comfort Access (might be important), opening the hatch causes the DC-DC converter to begin charging the 12 V battery. The only way I was able to measure the voltage of the 12 V battery without starting the DC-DC converter was to run long voltmeter leads up through the underside rear of the car to the 12 V terminals under the cargo area floor so that I didn't have to open the hatch.

I have monitored the voltage with the car off and as I said, it rests around 12.4 and goes to 14.9 when the car is switched on. I am measuring at the battery terminals. To start the DC converter on the 2013 model you have to charge the car or press the start button.

sdobbie said:

I have monitored the voltage with the car off and as I said, it rests around 12.4 and goes to 14.9 when the car is switched on.

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Maybe your 12 V battery isn't capable of maintaining a sufficient voltage when the high-voltage system is booting. I have been amazed to watch voltage of the 12 V system on our 2014 BEV drop as low as 11.9 V before the DC-DC converter begins charging the 12 V battery. I don't know how low the voltage would need to drop before errors would be stored. How low does the voltage drop on your i3 when the high-voltage system is booting?

How old is the battery? If it is four years, I'd replace it anyway, just to be sure - as it will be near end-of-life anyway. I know we are getting annoying harping on the battery, but 9 times out of 10, the sudden popping up of the 'everything is broke' errors is caused by a bad 12 v battery.

If that is not it - my take would be, once you have the ISTA software, is to note the errors, but then clear them, and see if the car goes back to normal, just to make sure that the faults aren't a one-off caused by some sort of power-surge or or software glitch related to the charging station.