Hydroplane-like feeling regenerating downhill

[NineElectrics]

Several times, in both Snow Mode and All-Purpose, I have had to engage regen strongly when going down a fairly steep decline. The most common example is hitting traffic around the bend on a steep mountain pass. In these cases regen will cause the car to feel like it's floating, or hydroplaning. The feeling is scary, and I don't really feel like experimenting with either hitting the brakes or the accelerator in this case. Is traction control on regen really that bad, or is this some kind of artifact?

This alarming feeling is by far the worst feature of the car. I wish regen was as good as standard ABS/traction control, or, failing that, could disable regen completely.

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[NineElectrics]

Note, this also occurs on bare, wet roads. It's not just a snow/ice thing.

 

[jjswan33]

Are you talking about reduced/limited regen? If you go downhill a long ways the regen is severely limited (after the latest software update especially), it‘s worse with a cold battery (like after a day of snowboarding).

 

[NineElectrics]

Are you talking about reduced/limited regen? If you go downhill a long ways the regen is severely limited (after the latest software update especially), it‘s worse with a cold battery (like after a day of snowboarding).

No, I don't think so. At one moment I'll have full regen, and then all of a sudden it will feel like the car is hydroplaning, then after a few seconds it's back to normal.

 

[madgrey]

Decelerating hard on a downward incline is a worst case for load/weight transfer to unload the rear wheels. Could this be a factor?

 

[NineElectrics]

Decelerating hard on a downward incline is a worst case for load/weight transfer to unload the rear wheels. Could this be a factor?

I don't know. It could be that the regen's control loop loses control temporarily and must restart, deactivating completely while it does so. Or perhaps it loses traction.

I wonder how traction control for regen is managed. Is it an ASIC, or is it run in software with a real-time operating system? Given the issues requiring Snow Mode, I suspect whatever is modulating regen, it's not fully baked to be as mature as modern ABS systems are.

 

[NineElectrics]

I don't know. It could be that the regen's control loop loses control temporarily and must restart, deactivating completely while it does so. Or perhaps it loses traction.

I wonder how traction control for regen is managed. Is it an ASIC, or is it run in software with a real-time operating system? Given the issues requiring Snow Mode, I suspect whatever is modulating regen, it's not fully baked to be as mature as modern ABS systems are.

If anyone experiences similar safety issues, please report to the NHTSA here: https://www.nhtsa.gov/report-a-safety-problem#vehicle

 

[Scoiatael]

Several times, in both Snow Mode and All-Purpose, I have had to engage regen strongly when going down a fairly steep decline. The most common example is hitting traffic around the bend on a steep mountain pass. In these cases regen will cause the car to feel like it's floating, or hydroplaning. The feeling is scary, and I don't really feel like experimenting with either hitting the brakes or the accelerator in this case. Is traction control on regen really that bad, or is this some kind of artifact?

This alarming feeling is by far the worst feature of the car. I wish regen was as good as standard ABS/traction control, or, failing that, could disable regen completely.

Was it cold? When you go down steep inclines for a while in cold weather the regen might turn off completely and you need to use the brakes.

 

[EzMev]

I remember reading Kyle's first review in snow that the wheels locked up downhill when he hit (or completely lifted up his foot) high regen. I can't imagine a circumstance where regen causing all wheels to stop rolling makes any sense and yeah, would be the opposite of ABS.

I guess find a parking lot with a big puddle and test it out if you have the time and inclination. Sounds like they are trying to manage that in snow mode, but should be ABS-like in most modes and Regen settings, not causing the wheels to slip...

 

[rivmok]

I've experienced this a few times when it was around freezing temps and regen set to high. As Scoiatael suggests regen turns off or is limited and you need to use the brakes. Sometimes a message is displayed that the battery is too cold and other times I don't think there was any warning. So far I have not experienced this when regen is set to standard/normal mode.

This is mentioned in the owners guide:

It's also displayed by the power gauge on the right side of the dash via icons and hash marks on the gauge.

 

[NineElectrics]

Was it cold? When you go down steep inclines for a while in cold weather the regen might turn off completely and you need to use the brakes.

The temperature was in the low 40s. The regen limited warning was never shown and regen was working fully for the entirety of the trip. Even if regen was limited, it shouldn’t decide to turn off going 50 mph down a mountain pass, 50 miles into the trip.

I think what happened was this:
- regen was applied fully, and working fully
- the downhill slope caused the regen to be overloaded somehow (too much current to the battery?)
- regen turns off completely (!)
- car lunges forward
- regen ramps up again

That, my friends, is a BRAKE FAILURE and a non-negotiable safety issue. If regen chokes for whatever reason, the real brakes have to compensate instantly. I can’t have the car braking, then stop braking immediately because of black magic reasons. This is just shit engineering.

 

[Dark-Fx]

The temperature was in the low 40s. The regen limited warning was never shown and regen was working fully for the entirety of the trip. Even if regen was limited, it shouldn’t decide to turn off going 60 mph down a mountain pass, 50 miles into the trip.

I think what happened was this:
- regen was applied fully
- the downhill slope caused the regen to be overloaded somehow (too much current to the battery?)
- regen turns off completely (!)
- car lunges forward
- regen ramps up again

That, my friends, is a BRAKE FAILURE and a non-negotiable safety issue. If regen chokes for whatever reason, the real brakes have to compensate instantly. I can’t have the car slow, then stop braking because of black magic reasons. This is just shit engineering.

First EV? It's generally not turning off, there just is so little room available for Regen and the excessive weight of the truck that it feels that way. My Bolt would do this. My Harley Livewire will do this.

 

[NineElectrics]

First EV? It's generally not turning off, there just is so little room available for Regen and the excessive weight of the truck that it feels that way. My Bolt would do this. My Harley Livewire will do this.

No, it’s my tenth EV over ten years. I’ve also owned a Bolt. Sure, regen was sometimes limited in the cold or at high charge levels (not the case here, car was at 55% SoC after fifty miles and 1000+ ft elevation gain), but I’ve never experienced this issue before, where regen is working fully throughout the trip, then turns off suddenly, then turns back on again at full power two seconds later and remains working at full power for the remainder of the journey.

 

[Dark-Fx]

No, it’s my tenth EV over ten years. I’ve also driven the Bolt. Sure, regen was sometimes limited in the cold or at high charge levels, but I’ve never experienced this issue before, where regen is working fully throughout the trip, then turns off suddenly, then turns back on again at full power two seconds later.

I sure would if the front tires slipped at all. My Rivian would exhibit this occasionally on the sport tires on a particular paved road that would get a lot of gravel on it before a stop.

I'd see if it still does it in conserve mode.

 

[NineElectrics]

I sure would if the front tires slipped at all.

I can’t rule that out, as the highway was slightly damp (although clear, and it hadn’t rained all day). The grade was negative five percent. But given that the Rivian has four motors, I would expect all wheel regen all the time. If not, that’s a problem in its own right.

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