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I love driving in snow! Regen braking seemed to turn off...

I love driving in snow and live up a steep, switchbacked road that ascends 1500’ in 5 miles, with a series of steep switchbacks. First move was to buy dedicated snows. Have used Blizzaks and Hakkapelitta’s but I couldn’t find Hakka’s to fit the 19” Geminis so went with Continental Viking Contact 7’s that were also highly rated but haven’t been around. They are smoother on dry pavement. I was really excited when we got a 5” dump yesterday and was looking forward to heading down the hill with regen braking. Have been a fan of manual transmissions for engine braking in sketchy conditions on steep declines.

While going down the first switchback it seemed like the car either was accelerating or sliding. After the third switchback I realized the regen just wasn’t working since I tested traction on the flats and hills with predictable outcomes.

Has anyone experienced this? I admit, this only happens with cranking the steering wheel. It might be considered a safety feature which is scary when expecting to slow down and actually speed up. I will have anticipate this and start using the brakes on corners, when traditionally I’d engine brake and let off the pedal in my ICE vehicles.

Thanks,
AndY
 
Off-road assist helps going up the steep switchbacks but didn’t stop the regen from stopping on the downs. I don’t know if this is a failure or a feature of the regen. I can see how unexpectedly letting off the accelerator in a sharp corner could cause a car to lose traction from the regen. It’s just I want to use it. It freaks me out to step on the brakes in a corner. I’m also a cyclist and motorcyclist and you always brake before a corner and not in it unless you want to break traction...
 

Snow Drift

[Off-Road Assist] Activated
Feb 10, 2016
1,996
1,612
Long Island
Did the regen work as expected anywhere along your drive?

As @MP3Mike said, if it was early morning, or anytime when the battery is cold, you get "...." under PRND, which means you have limited regenerative braking since the battery is cold.

I admit, this only happens with cranking the steering wheel. It might be considered a safety feature which is scary when expecting to slow down and actually speed up.

What do you mean by the car sped up? Was that due to gravity/inertia or do you think the car was powered? If you think the car was propelled forward...do you have CREEP on? That will drive the car forward at slow speeds and require you to use the brake pedal. Try using HOLD or ROLL, to get a normal manual car sensation of "the car listens to me" and continues to slow as you are off the accelerator.
 

TLej

Little-Known Member
Dec 29, 2015
553
557
Edmonton, Alberta, Canada
@Dogter Y I have heard that Tesla is disabling the ability to select standard or low regen, and instead having the car decide what level of regen is appropriate automatically. I'm not a fan of this idea, and I still have the ability to swap between regen states in my older S, but I don't know if this "feature" has already been implemented on newer cars (if in fact it is anything more than a rumour). Per your notes above, as long as the battery was able to accept regen what you describe is not how it has worked in the past.
 

jf64k

Member
May 9, 2020
490
546
Los Angeles
Found this bit in the Owner's Manual:

NOTE: Installing winter tires with aggressive compound and tread design may result in temporarily-reduced regenerative braking power. However, your vehicle is designed to continuously recalibrate itself, and after changing tires it will increasingly restore regenerative braking power after some moderate-torque straight-line accelerations. For most drivers this occurs after a short period of normal driving, but drivers who normally accelerate lightly may need to use slightly harder accelerations while the recalibration is in progress.

And this:

WARNING: In snowy or icy conditions Model Y may experience traction loss during regenerative braking, particularly when in the Standard setting and/or not using winter tires. Tesla recommends using the Low setting (see To Set the Regenerative Braking Level on page 61) in snowy or icy conditions to help maintain vehicle stability.
 
I have also noticed regen being less than what I have gotten used to.
I now need to warm up the car (which does make it nice getting into it) before I go.
If I just decide to get into the car, the dreaded dots are visible.

Regen_braking_cold (1).JPG

It can take some fair amount of driving mileage before they go away and the regen is back to normal.
 
Thanks for all the suggestions. Yes, the car is typically cold and 80% charged when I leave my house. I do have new snows, standard braking, and the problem is downhill only. It's better in Off-road Assist. I haven't noticed the "dots" but will look tomorrow before I drive down the hill. I recently drove from Portland to Boulder with the new snows so any "recalibration" should have happened. I've been relatively light on the pedal to conserve charge and tires, but like to play in the turns and like to charge back up the hill when the mood strikes. Every day I drive the Y the more I like it. I wish it had a pneumatic suspension that I could raise the ground clearance and a heated steering wheel. I wish the voice commands were programmable so I could add custom commands (unless there is a way to do this that I don't know). Snow performance is good, but I haven't tested the limits of traction it too much since there aren't many low consequence places to do that. It's interesting what the manual said about snow tires and decreased regen, and the low setting for braking is better for control in the snow.
 
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What the OP describes totally happens to me every time I leave my house. Regen is strong going into a turn/switchback, and then disappears, and the car accelerates on its own weight downhill. Then, strangely, 10 meters later, regen comes back. I got used to it.

A few weeks ago, a software update reduced regen fleet-wide. I preferred the old setting, personally, because it was easier to stick with one-pedal driving. But it's not a huge deal.

Thanks @jf64k for that interesting recommendation from the Owners' Manual.
 
Reviving a little bit of an old post here.

Having driven my Y in the snow a few times, I’ve notice a few interesting things about regen and snow/ice. Regen seems to be an interesting critter and double edge sword from what I’ve experienced so far. A main thing to keep in mind is regen requires rolling resistance to work. So do brakes for that matter. So in very slippery (ice) conditions, there isn’t enough traction to drive the generator and regen just doesn’t work. Just as your brakes don’t.

In more packed snow, less slippery conditions, I find there is enough rolling resistance for regen to still be (sometimes very) effective. So effective at times, that it upsets the weigh balance of the car, unweighting the rear wheels and potentially initiating a slide, especially if trying to turn. Sword edge number 2.

Where I love it, is during transitions. For instance when you’re trying to slow and hit a patch of ice. Because the rolling resistance is reduced, the amount of regen (braking force) is instantly reduced appropriately. Once the patch of ice is cleared, rolling resistance increases, as does regen effectiveness. So instead of pulsing the brakes in an on/off fashion like an ABS system, the braking force is essentially maximized for the available traction at the time.

That said, especially with the weight distribution piece, still requires attention and careful driving. But I have found that modulating the regen with the throttle to have much better stopping power and control than the brakes. If you’re experiencing reduced regen, particularly down hill in slippery conditions, it probably has more to do with (lack of) traction and you’re brakes likely aren’t as effective either.


I believe this video reaffirms some of these concepts as well as highlights some of the AWD functionality.
 

Rshephorse

Member
Aug 2, 2020
180
132
Plattsburg
I have been trying to figure this out. I have been using ScanMyTesla to follow the MaxRegen number- the peak amount of kW that the car could regenerate. There are two things I've noticed,
1) if I slip or slide on purpose it will drop regen
2) there is a section of road where the regen ALWAYS drops way down to the 20s of kW.
It DOESN'T matter how warm the battery is- does it with a 78 degree battery.
it Doesn't matter about the state of charge, it will do this when there is only 40% charge.
it doesn't even matter how slow I go! I've tried creeping down these S-turns, MaxRegen just plummets down as I creep around that first corner onto the steep grade.
What I think is happening is that i am either making too sharp of a turn, or the inclinometer/accelerometer is sensing the steep grade, and freaking out, and decreasing regen.

I can moderate the effect a bit by accelerating through these turns- which in the end leads to some crazy speed, but this is why I think it is the grade of the road that is causing the car to freak out- by me accelerating, I am fooling the accelerometer/inclinometer into not noticing how steep the road is,, obviously they are worried that too much regen in the hands of a clueless driver on a steep downhill is too much of a liability.

Wheel slippage? Different wheel rotations between wheels? might be it, but then I don't know why accelerating would mitigate it.

it's frustrating of course, using the hydraulic brakes when I know the battery is set up to accept a max regen >60 kW. And, it make the car a lot less fun to drive on exciting roads... I wish there was a "Rally Mode" that would allow max regen to stay as high as the battery would tolerate and let the driver modulate the decelerative force.
 

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