[reductase]

I'm wondering what the symptoms are when there is no remaining stored energy. Does it give a pre shutdown warning?

Background:
Yesterday I was driving on range extender fuel with 4 miles range remaining. When I stopped for a traffic light, car drops into neutral and displayed a message to put foot on brake and shift into gear. I tried several times and got nothing. Couldn't move, so had to use the SOS button for roadside assistance. About 20 minutes pass and I decided to try it again, same message but this time it engages drive and I'm driving again with 3 miles range. When I stopped again for another traffic light, the same error message came up and it wouldn't move from neutral. This time the tow truck was already close by so it went straight to the service center. (Super annoying this all happened within a half mile of home.)

Knowing there was still fuel in the range extender and it is supposed to maintain charge at 6% , I was surprised that the initial diagnosis from the BMW service center is low voltage for drivetrain. Apart from the regular warnings that the available range is low, I would expect it gives a low power error if that is the actual problem. Has anyone experienced running out of battery mid-journey?

[afadeev]

Originally Posted by reductase

I'm wondering what the symptoms are when there is no remaining stored energy. Does it give a pre shutdown warning?

Yes, you get multiple warnings.
One with 6% battery left (IIRC), and a yellow warning light.
The second one with 2% battery left, and a red warning light, coupled with reduced power.

The lowest I got was 1.5% within 1/2 mile of the house, but then it's downhill, so I got the battery charged up to 2.5% by the time I pulled into the garage.

The car was still derivable, but I did not enjoy the experience, and made an effort not to repeat it.

Originally Posted by reductase

Background:
Yesterday I was driving on range extender fuel with 4 miles range remaining.

Range is irrelevant (BS estimation output), what was the battery SOC % level?

Originally Posted by reductase

When I stopped for a traffic light, car drops into neutral and displayed a message to put foot on brake and shift into gear. [...] About 20 minutes pass and I decided to try it again, same message but this time it engages drive and I'm driving again with 3 miles range. When I stopped again for another traffic light, the same error message came up and it wouldn't move from neutral.

That is strange, and not consistent with what I had experienced at all. Ever.
Perhaps, you were below 2% SOC?

Originally Posted by reductase

Knowing there was still fuel in the range extender and it is supposed to maintain charge at 6%

This is 2x strange.
Was REX running?
If not, why not (out of gas)?
If REX was running, was it failing to charge up the battery while you were parked?

If the answer to the last sentence is "yes", your REX was not working properly, and you should have it serviced.

If the REX was not running, then it must have been out of gas. In that case, if you were down to below 2% SOC, anything is possible. Although, I had never had the car force-drop into Neutral on either REX or BEV.

HTH,
a

[reductase]

Originally Posted by reductase

I'm wondering what the symptoms are when there is no remaining stored energy. Does it give a pre shutdown warning?

Yes, you get multiple warnings.
One with 6% battery left (IIRC), and a yellow warning light.
The second one with 2% battery left, and a red warning light, coupled with reduced power.

Definitely no red warning lights while I was driving- yellow came on when the Rex range was low, but not certain at what range remaining.

Range is irrelevant (BS estimation output), what was the battery SOC % level?

No idea where SOC% is displayed- I have the range remaining for battery and Rex. At no point did the battery go below the triangle which indicates Rex engagement (which I've experienced with subsequent power reduction while driving steep uphill with Rex).

Originally Posted by reductase

When I stopped for a traffic light, car drops into neutral and displayed a message to put foot on brake and shift into gear. [...] About 20 minutes pass and I decided to try it again, same message but this time it engages drive and I'm driving again with 3 miles range. When I stopped again for another traffic light, the same error message came up and it wouldn't move from neutral.

That is strange, and not consistent with what I had experienced at all. Ever.
Perhaps, you were below 2% SOC?

I didn't think so, based on the Rex triangle activation point battery remained at that level.

Originally Posted by reductase

Knowing there was still fuel in the range extender and it is supposed to maintain charge at 6%

This is 2x strange.
Was REX running?
If not, why not (out of gas)?
If REX was running, was it failing to charge up the battery while you were parked?

If the answer to the last sentence is "yes", your REX was not working properly, and you should have it serviced.

If the REX was not running, then it must have been out of gas. In that case, if you were down to below 2% SOC, anything is possible. Although, I had never had the car force-drop into Neutral on either REX or BEV.

Rex had been running for the previous several miles, on and off since it was at low speed. When I stopped the Rex stopped as well. The Rex didn't restart until after the 20 minutes had lapsed, it remained on until stopped at the second set of traffic lights and it didn't reactivate again. It was low on gasoline, but still had been showing 3 miles range remaining on Rex.

Thanks for your notes from your previous low battery experience. I'll be checking in with the service advisor again tomorrow, it's helpful knowing there are legit end of battery warnings, not this weird error.

[The J-Man]

I once had 4 miles remaining on electric and a message came on warning me that the Rex had malfunctioned and that I needed to pullover asap. Unfortunately I was about 20 miles from civilization, but I drove all the way down to 1 mile remaining and then pulled over. I tried restarting many times and the Rex tried to turnover but made a terrible noise. I eventually let it sit for about 20 minutes, tried again, and the Rex fired up and has worked normally since.