Regenerative braking on icy roads

[buddhafree]

Hold, Roll and Creep driving modes are only active at speeds below ~4 MPH. At higher speeds you have to actively control the degree of regenerative braking using your foot (even when regenerative braking may be reduced or if your Tesla Model Y has the option to enable low regenerative braking (2020, early 2021 Model Y only else when equipped the S3XY buttons available from Abstract Ocean.)

The point is not to allow complete wheel lockups. Rotational speed of the wheel is zero when it stops turning.
It was reported by few people who did tests on youtube as very helpful and it does make sense to me. I'm planning to try it once we get ice/snow conditions in my area.

 

[jcanoe]

The point is not to allow complete wheel lockups. Rotational speed of the wheel is zero when it stops turning.
It was reported by few people who did tests on youtube as very helpful and it does make sense to me. I'm planning to try it once we get ice/snow conditions in my area.

Wheel lockup can happen at higher speeds than ~4 MPH. Depending on road conditions one or more tires can break free whenever regenerative braking is active. Most regenerative braking in the dual motor Tesla Model Y is performed by the rear drive unit, a rear wheel lockup of one or both rear wheels could happen. If you manage to slow the Tesla Model Y to 4 MPH or less then Roll or Creep would lessen the chance of wheel lockup. In my experience descending the hill on my street when snow and ice is present wheel lockup under regenerative braking can occur at ~10 MPH when attempting to slow my descent.

 

[rjpjnk]

Hold, Roll and Creep driving modes are only active at speeds below ~4 MPH. At higher speeds you have to actively control the degree of regenerative braking using your foot (even when regenerative braking may be reduced or if your Tesla Model Y has the option to enable low regenerative braking (2020, early 2021 Model Y only else when equipped the S3XY buttons available from Abstract Ocean.)

The way I look at it, these modes Hold, Roll, Creep control what the car does *after* it stops, not how it stops. I think the intention is to emulate the feel of an automatic transmission creep or clutch roll if desired.

 

[dzajic]

We had some bad winter road conditions a few days ago, first time driving my new 2023 Model Y LR AWD (brand new Pirelli PZero winter tires) in really bad winter conditions, and while slowing down, the whole car started to rotate, it was terrifying. I've never had this happen in any modern car. Was this regen braking causing the loss of yaw control?

How can I prevent this dangerous behavior, and force the car to use ABS and ESP? From reading the recent comments here, I'm not sure what to do. This isn't my first EV, but my last two were RWD (i3 and Smart ED). I don't remember ever having a single stability control issue in 10 years with those cars.

 

[jcanoe]

We had some bad winter road conditions a few days ago, first time driving my new 2023 Model Y LR AWD (brand new Pirelli PZero winter tires) in really bad winter conditions, and while slowing down, the whole car started to rotate, it was terrifying. I've never had this happen in any modern car. Was this regen braking causing the loss of yaw control?

How can I prevent this dangerous behavior, and force the car to use ABS and ESP? From reading the recent comments here, I'm not sure what to do. This isn't my first EV, but my last two were RWD (i3 and Smart ED). I don't remember ever having a single stability control issue in 10 years with those cars.

Yes, the momentary loss of traction was due to the regenerative braking in the Tesla Model Y. The regenerative braking in the Tesla Model Y cannot be disabled or reduced (the option to set reduced regenerative braking in the Tesla Model Y was removed by Tesla; reason not provided by Tesla.) The Model Y's stability control and traction control will quickly bring this under control provided you have not gone off the road.

In bad weather/snow conditions drive in Chill mode. It may help to set the Pedal and Driving control set to Creep. Learn to come off the accelerator pedal slowly to prevent the regenerative braking from activating aggressively.

A high state of charge, i.e. above 85% and/or a cold battery will result in reduced regenerative braking being available until the battery has been warmed and the state of charge is reduced. You can now set the Regenerative Braking to use Blended Friction braking when the regenerative braking is reduced or unavailable. This setting results in more consistent slowing of the Tesla Model Y when you reduce pressure on the accelerator pedal when regenerative braking is reduced or not available.

 

[OxBrew]

Yes, the momentary loss of traction was due to the regenerative braking in the Tesla Model Y. The regenerative braking in the Tesla Model Y cannot be disabled or reduced (the option to set reduced regenerative braking in the Tesla Model Y was removed by Tesla; reason not provided by Tesla.) The Model Y's stability control and traction control will quickly bring this under control provided you have not gone off the road.

In bad weather/snow conditions drive in Chill mode. It may help to set the Pedal and Driving control set to Creep. Learn to come off the accelerator pedal slowly to prevent the regenerative braking from activating aggressively.

A high state of charge, i.e. above 85% and/or a cold battery will result in reduced regenerative braking being available until the battery has been warmed and the state of charge is reduced. You can now set the Regenerative Braking to use Blended Friction braking when the regenerative braking is reduced or unavailable. This setting results in more consistent slowing of the Tesla Model Y when you reduce pressure on the accelerator pedal.

OT, just curious, was this reply written by ChatGPT? Reads like it. All seems correct, not questioning it, just wondering.

Apologies for the aside.

 

[jcanoe]

OT, just curious, was this reply written by ChatGPT? Reads like it. All seems correct, not questioning it, just wondering.

Apologies for the aside.

Yes; please deposit $5.

 

[DrGriz]

Yes; please deposit $5.

100% agree with @jcanoe. We drive in those conditions regularly (almost daily) and I would strongly recommend that you also try putting the car in off-road assist as well. It also puts your car in chill, but the distributed braking and 4 wheel drive full time also helps greatly with preventing the momentary loss of traction from occurring in the first place.

 

[gt2690b]

100% agree with @jcanoe. We drive in those conditions regularly (almost daily) and I would strongly recommend that you also try putting the car in off-road assist as well. It also puts your car in chill, but the distributed braking and 4 wheel drive full time also helps greatly with preventing the momentary loss of traction from occurring in the first place.

Have you ever had problems with TCS being off while in off road mode?

 

[GtiMart]

Traction control isn't off in off-road mode. I actually wish it would let the tires slip a bit more. It's still very much present.

 

[dzajic]

Yes, the momentary loss of traction was due to the regenerative braking in the Tesla Model Y. The regenerative braking in the Tesla Model Y cannot be disabled or reduced (the option to set reduced regenerative braking in the Tesla Model Y was removed by Tesla; reason not provided by Tesla.) The Model Y's stability control and traction control will quickly bring this under control provided you have not gone off the road.

In bad weather/snow conditions drive in Chill mode. It may help to set the Pedal and Driving control set to Creep. Learn to come off the accelerator pedal slowly to prevent the regenerative braking from activating aggressively.

A high state of charge, i.e. above 85% and/or a cold battery will result in reduced regenerative braking being available until the battery has been warmed and the state of charge is reduced. You can now set the Regenerative Braking to use Blended Friction braking when the regenerative braking is reduced or unavailable. This setting results in more consistent slowing of the Tesla Model Y when you reduce pressure on the accelerator pedal when regenerative braking is reduced or not available.

Loss of traction wasn't my problem even though it was caused by that.
I'm trying to understand why the car didn't take action to bring the rotation under control.
The car couldn't know it was still on the road because the road wasn't visible.

 

[dzajic]

100% agree with @jcanoe. We drive in those conditions regularly (almost daily) and I would strongly recommend that you also try putting the car in off-road assist as well. It also puts your car in chill, but the distributed braking and 4 wheel drive full time also helps greatly with preventing the momentary loss of traction from occurring in the first place.

I'm willing to try it, maybe in a huge parking lot next time we have enough snow, but not sure how this would help unless ABS was activated in the event I experienced.
What's strange is I haven't noticed ABS come on once, does the car even have it? If so how can I tell it's working? Every other car I've had it was quite obvious from the pulsating at the wheels.

 

[DrGriz]

Have you ever had problems with TCS being off while in off road mode?

Traction control isn't off in off-road mode. I actually wish it would let the tires slip a bit more. It's still very much present.

Yes, T/C is off according to the user interface screen (and the owner's manual).

Also, when it is on, Chill is not highlighted and Standard Acceleration mode is a light color of gray which is different than the color when it is actually selected. I am not certain I know what that means, except that it implies that it is reduced.

Here is how the manual describes it. Sounds something like chill.

Am I concerned that T/C is off? Yes. But, I have never had a problem. We have driven on all sorts of compromised roads, from snow covered dirt to icy to rutted icy to glare ice to packed snow to slush to rutted snow. In every case we keep the steering screen up and have switched back and forth turning Off Road Assist on and off to see what it does. In every situation ORA feels much more stable. And we feel it instantly. We don't slip into ruts or kick out. Do we ever slip? Yes, but 1/100 of the times that we do in regular mode. We are cautious drivers. We slow down in poor conditions. But we can tell the change in feel of the road in a second. Someone else might feel different.

We do think that traction control is very good, but it takes a second (or a fraction thereof) to kick in and that's uncomfortable for us.

 

[DrGriz]

I'm willing to try it, maybe in a huge parking lot next time we have enough snow, but not sure how this would help unless ABS was activated in the event I experienced.
What's strange is I haven't noticed ABS come on once, does the car even have it? If so how can I tell it's working? Every other car I've had it was quite obvious from the pulsating at the wheels.

ABS is definitely there. I find it doesn't feel as strong as with other vehicles. Just my observation.

 

[dzajic]

ABS is definitely there. I find it doesn't feel as strong as with other vehicles. Just my observation.

Interesting. Will it activate without the brakes being applied? It should, but it didn't as far as I can tell.

 

[GtiMart]

The message "off-road assist enabled" doesn't imply that traction control is off. You are simply assuming that. The manual says "allowing wheels to spin" but doesn't state how much it allows them to spin. It might just reduce traction control by 10%, and that's how it feels to me on snow.
Same would be true for slip-start. It might say that it allows wheels to spin but they certainly don't spin freely, there's still a lot of reluctance to letting them slip. No burnouts possible.

 

[DrGriz]

The message "off-road assist enabled" doesn't imply that traction control is off. You are simply assuming that. The manual says "allowing wheels to spin" but doesn't state how much it allows them to spin. It might just reduce traction control by 10%, and that's how it feels to me on snow.
Same would be true for slip-start. It might say that it allows wheels to spin but they certainly don't spin freely, there's still a lot of reluctance to letting them slip. No burnouts possible.

I don't want to start a pissing contest, but did you look at the screenshot I posted? It literally has a line through T/C.

And the owner's manual discusses Off road assist under the section labeled "Disabling Traction Control"

But OK. Maybe "disable" doesn't mean what I think it does and it is only partial.

 

[GtiMart]

Fair enough, I also don't want a pissing contest. I will just state my personal experience and feeling. I turned on off-road mode this morning as there was a fresh foot of snow fallen in the last 24h. As soon as wheels start slipping, power is reduced whatever my accelerator pedal position. Obviously worse when the steering wheel is turned as stability control also kicks in but even straight, it's clear that there is some traction control. I need to pump the accelerator to try to induce some slippage. My feeling is that the back will slide sideways slightly more in a straight line acceleration, but there is no way I can put the car sideways.
Maybe there's no traction control but stability control kicks in as soon as there's 1 degree of yaw and that uses traction control...
Do with that information what you will

 

[DrGriz]

Fair enough, I also don't want a pissing contest. I will just state my personal experience and feeling. I turned on off-road mode this morning as there was a fresh foot of snow fallen in the last 24h. As soon as wheels start slipping, power is reduced whatever my accelerator pedal position. Obviously worse when the steering wheel is turned as stability control also kicks in but even straight, it's clear that there is some traction control. I need to pump the accelerator to try to induce some slippage. My feeling is that the back will slide sideways slightly more in a straight line acceleration, but there is no way I can put the car sideways.
Maybe there's no traction control but stability control kicks in as soon as there's 1 degree of yaw and that uses traction control...
Do with that information what you will

I don't want to put my car sideways, so whatever is happening is fine with me.

The other thing I have read (although I don't see it in the owner's manual where I have looked) is that while in ORA, the regenerative braking is distributed 50/50 front and back, and this may affect the behavior of the car in a challenging situation.

 

[GtiMart]

Absolutely. 50-50 is the main benefit, both for acceleration and regen, IMO. That's why I use it. Otherwise the car eventually sets itself up for 50-50 when there's a lot of slip, but will revert back to rear-biased after a little while of not slipping. It makes for a less predictable behavior so I prefer 50-50 when there's a lot of snow on the roads. When you're used to driving a Subaru, off-road mode feels better. I still wish I could turn corners like my previous WRX in its "traction mode" that reduced assistance. The car would accept a few degrees of yaw and counter-steer instead of systematically reducing power like my model 3 does.