Regen braking in slippery situations

[SSD420]

I was reading some comments on the Facebook Model X group and noticed a comment about you should regen braking to low when in slippery conditions or in icy weather. Is this true? If yes, why?

I found in the slippery snow and ice earlier this week that it seemed helpful to keep me on a slower pace.

Someone also noted that regent braking locks the brakes??? Any truth to this stuff?

 

[SSD420]

*regen (iPhone autocorrect fail)

 

[Xenius]

Did my first wintry weather driving this past Saturday and didn't change my regen settings (I keep it on standard) and the Model S performed flawlessly. I'm sure some of our cold weather friends could give more input. I know Bjorn does a ton of snow/cold driving so I bet whatever setting he uses would be great.

 

[wycolo]

Is your Regen controllable from menu levels on the 17 inch screen (like on my 2012 S)? If so the driver has no ability to change this on the fly in response to changing road conditions. So you would have to err on the side of caution by setting to weak regen ahead of time or else developing a knack for dealing with High Regen safely by practice, practice etc. I drove thru 3 winters in the High Rockies with regen permanently set to High without any problems or panic situations FWIW. But at the first snow each winter I instinctively had to deal with the issue, especially if still running all-season tires! Get yourself top performance snow/ice tires (Blizzaks or equivalent) on all 4 wheels!

The Spark EV lets you set Regen simply by choosing D or L. What could be simpler than that?
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[Jeeps17]

I just had an X on overnight loan (to check garage fitment and have my wife try one loaded with our family), and it just happened to be a fairly nasty but typical Montreal weather phenomenon where we got a combination of 10cm snow immediately followed by warmer temperatures and freezing rain.

I had some fun testing the X in these slippery conditions (always in safe settings), and came away very impressed with Tesla's implementation of AWD traction control. I have been driving a RWD P85 S for over three years, and while it performs very well in most conditions, it is very easy to get the rear of the car swerving in medium amounts of snow or slush (especially on hills).

The X almost felt like it was on dry pavement, obviously acceleration was slower but I only felt the most minute wobble in the less used streets I drove on (more snow & slush). Braking with the friction brakes was excellent.

I tried both regen settings, and in these conditions found no significant difference (this surprised me), but to be fair I did not encounter large ice patches, as most streets had been doused with salt by the time I ventured out.

This may obviously not be applicable to D models, but when driving my S I usually leave regen to low in winter, standard was enough to cause the car to briefly lose grip while going down a snow-packed downhill street in previous winters.

I have quite a bit of experience driving in "real" winter conditions, and this extended test drive was enough to sway me to order an X (and more importantly my wife liked it enough not to object !).

 

[vandacca]

I've driven my X the past two weekends from Waterloo to Hamilton in the snow storms and I didn't have any issues with the regen (set to the more aggressive setting). And I am very cognisant of this issue ever since downshifting put my manual-drive pickup truck into a spin (during an ice storm) 25+ years ago.

 

[SSD420]

Thanks guys. I've always left regen at the highest setting too but after reading that other group, I wondered if I just hadn't hit enough slippery weather yet to have had an issue.

 

[Solarman004]

I also keep regen to standard for the same reason I would put my former van in low gear in nasty snow and ice: you have more control if all wheels are turning, than with braking when trying to slow down.
But remember that you can feather the regen by coming off the accelerator slowly. If you rapidly come fully off the pedal in std regen, on a snowy hill, you could lose some control. But on snowy hilks here in the Rockies, I've found controlled use of std regen to be excellent.

 

[Nerdy_Engineer]

I'm not sure how much of a difference it would make in the real world. I keep my Model X in a garage, but every time I drive it during or after we get snow, my regen is always limited because of the cold battery. I suppose if I drove longer so the battery pack could warm up enough for full regen. So I imagine that most of the time, even if our regen is set to standard in the winter, we're probably getting closer to the low regen anyways.

I took my Model X out last weekend to play in the snow. My rear tires (all season) slipped a little when pulling out of a street and turning hard right while accelerating more than I normally would. My old Subaru would have slipped a lot more in the same situation. I was thoroughly impressed by how the Model X handled in the snow. I didn't experience any noticeable sliding or anything from the regen, but I also wasn't in a situation where I was driving down a steep curving hill.

 

[⚡️ELECTROMAN⚡️]

I was wondering about this last week. It felt very stable and controlled when I hit full regen on the snow and ice. I only tested this in safe open areas. Does anyone know if it applies varying amounts of regen to individual wheels when regen braking just like it would when applying the standard brakes? It felt like it did.

 

[Pwdr Extreme]

I tested this very thing today in the P100D I'm driving which has the performance 22" wheels, so the tires aren't the best in the snow. Very slick roads in some sections. Max regen when slowing on pavement is usually around 55kw, when I deliberately did it on ice, the max regen limited to 30-35kw, so obviously the computer is reducing the regen acting similar to anti lock brakes. I was still able to maintain directional control and the vehicle tracked straight. It was apparent the tires were slipping some as I didn't have as much control as I did while coasting, but I still had control. Exactly like ABS brakes work. The stability system on the car will allow it slide some before stepping in, but will take over long before you get into trouble. I've been in some that the stability takes over too soon and too aggressively, almost making the situation worse.

In certain conditions, inducing a touch of oversteer actually will help the car corner. This is one situation the MX lacks, it tries to power both front wheels too aggressively which in turn causes the car to under steer. Safer for the typical person who isn't experienced with understeer / oversteer, but not as easy to maneuver for a veteran driver.

I should add I'm a Montana native with 2 million + miles of experience, so I am very familiar with how a car feels and reacts and also how to handle skidding and sliding conditions.