Unintended acceleration

[Rescuelady]

Morning,
I have seen posts in the past about unintended uncontrolled acceleration causing accidents on this forum before. One would think it was human error, floor mats or an electrical issue.
I was curious if anyone has any updates on unintended rapid acceleration? Thank you kindly

 

[Timjohn]

In the two years that I have been viewing this forum, I have never heard of an unintended acceleration with a BMW i3. Maybe you can provide the links to these postings.

 

[Timjohn]

OK this is what I found reported with a driver of an i3 in Hawaii ....nothing to do with a fault of the vehicle. Somehow I believe this is a credible explanation so not to worry that this is a systematic fault of BMW i3 vehicle. Social media is dangerous in starting rumours and falsehoods.

While information is scarce, we suspect the driver did one of two things. He either hit the accelerator instead of the brake while parking or he selected drive instead of reverse when attempting to leave the parking spot. It's more likely that the accelerator was applied when attempting to brake, as this seems to most often be the case with this type of accident.

 

[Joff]

I have heard of people thinking the car is accelerating on it's own when they are regenning and then hit a bump which causes the decel of regenning to stop temporarily. Another thing that has happened - because the car does not "creep" in drive, people can forget the car is in drive while they sit in a parking space then they accidently step on the accelerator and drive through a wall at the mall or something,( then blame the car!)

 

[Rescuelady]

https://www.e90post.com/forums/showthread.php?t=1566808

 

[Rescuelady]

https://www.bimmerfest.com/threads/2014-bmw-x3-full-acceleration-on-its-own-causes-crash.1167873/

 

[Rescuelady]

Thank you for the reply. Regards

 

[Timjohn]

Well thanks for the links to events of unintentional acceleration. However, none of these events were with BMW's i3 model.

 

[Arm]

The i3 has never ever had this issue...ever.

 

[Anonymous]

Only one I remember, was posted by a guy who rented or had just bought an i3 in the UK. Entering a tight parking space, he came in with a bit of speed, and turned sharply to full wheel lock to get into the space, then said the car accelerated, jumped the curb and tapped a pole. When you turn sharply, the regen braking shuts off, so what happened was the sudden loss of regen braking with an inexperienced i3 driver let the car get away from him when he was relying on the deceleration of the regen braking to slow and stop the car.

 

[Arm]

Only one I remember, was posted by a guy who rented or had just bought an i3 in the UK. Entering a tight parking space, he came in with a bit of speed, and turned sharply to full wheel lock to get into the space, then said the car accelerated, jumped the curb and tapped a pole. When you turn sharply, the regen braking shuts off, so what happened was the sudden loss of regen braking with an inexperienced i3 driver let the car get away from him when he was relying on the deceleration of the regen braking to slow and stop the car.

That's not acceleration...that's coasting :lol:

 

[Mastedon]

Our i3 has the "Unintended Acceleration" problem. I've asked several dealers and they state there is no known record of that issue.

It's not really acceleration as it is a "lack of deceleration" (regen stops) when going over a bump while slowing. Apparently (as mentioned above), the regeneration automatic braking that occurs when you take your foot off, or back off the pedal, gets somehow shocked over a decent sized bump or indentation in the road on our vehicle. It's somewhat unnerving when it happens even though we now know to expect it. Luckily it's momentary and only lasts several seconds before resuming normal operation.

Any ideas on what might be triggering that momentary loss of regen would be helpful.

 

[mojo]

Has it been scanned for diagnostic data?

 

[alohart]

It's not really acceleration as it is a "lack of deceleration" (regen stops) when going over a bump while slowing. Apparently (as mentioned above), the regeneration automatic braking that occurs when you take your foot off, or back off the pedal, gets somehow shocked over a decent sized bump or indentation in the road on our vehicle. It's somewhat unnerving when it happens even though we now know to expect it. Luckily it's momentary and only lasts several seconds before resuming normal operation.

Any ideas on what might be triggering that momentary loss of regen would be helpful.

I think traction control or dynamic stability control, whatever it's called, is to blame for this behavior. Traction control was improved considerably for LCI i3's. As a result, regen braking doesn't suddenly stop when driving over a rough road. Our former 2014 i3 suffered from this loss of regen braking over rough roads whereas our 2019 i3 has never suffered from this behavior. Unfortunately, I don't think this behavior can be changed in pre-LCI i3's.

 

[weajd]

I think there are a number of switching solenoids in the EME (inverter).
I speculate that if the rear wheels hit large bumps in the road, it might upset the solenoids and the switches to momentarily shut off the regeneration from AC at the electric motor to DC for the battery. This is just speculation without any experimentation.

 

[mojo]

My speculation (no inside knowledge, no empirical data) is that those who programmed the stability control for the car made a basic decision that if the car's sensor inputs suggested that the car is starting to lose stability, they will switch off regen to remove the possibility of losing rear wheel traction as a result.

As far as I'm aware, there is no means to use regen to "steer" the car from the rear, whereas if they turn off regen, they can use the rear brakes individually to assist in stability.

Of course we will never know for sure - as far as I know, BMW don't release info about the design of the car at that level of detail.

 

[martinj]

all i3s behave this way when hitting a bump I believe it’s a design feature to protect the engine mountings from excessive torque when the rubber hits the tarmac.

 

[alohart]

all i3s behave this way when hitting a bump I believe it’s a design feature to protect the engine mountings from excessive torque when the rubber hits the tarmac.

As I wrote, our 2019 i3 doesn't shut off regen braking when driving over rough city roads unlike our 2014 i3. Maybe regen braking would shut off on a very rough washboard unpaved road, but I've never driven on such a road in either of our i3's.

I think you're talking about propulsive power being shut off when a rear wheel loses contact with the pavement. That happens as you wrote.

 

[eNate]

With the 2018 introduction of the i3S and the LCI, BMW also switched to a new wheel speed sensor with 50x the fidelity of what was being used in the 2014-2017 cars. I'm pretty sure this is what eliminated the pesky trait of releasing regen over rough surfaces: the system could now confidently "know" what the wheels were doing.

https://www.press.bmwgroup.com/glob...rol-system-for-all-future-bmw-and-mini-models

"...in the new BMW i3s ... the innovative traction control system adapted specifically to the instantaneous power deliver of the BMW eDrive system. ... the system improves traction and driving stability in adverse weather and road conditions, in active Brake Energy Regeneration phases and when accelerating out of tight corners. At the heart of this innovation is the control system’s 50-times-faster routine, made possible because the control process is calculated directly in the powertrain instead of in a remote unit requiring long signal paths."​

 

[martinj]

thank you eNate for that fascinating detail