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Regenarative breaking on ice/snow,sliding ?

Discussion in 'Model S: Driving Dynamics' started by Matias, Apr 26, 2014.

  1. Matias

    Matias Active Member

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    #1 Matias, Apr 26, 2014
    Last edited: Apr 26, 2014
    Regenarative braking on ice/snow,sliding ?

    I read from Swedish car magazine "Teknikens Världen", that on winter regenerative braking can make cars back slide, if braking is set to "normal". I would like to hear Tesla owners experiences about regenerative braking on ice/snow.
     
  2. JohnQ

    JohnQ Active Member

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    I found it to operate no differently than using the brake pedal. If I lifted off the accelerator smoothly then there were no issues at all. If I pulled my foot off quickly it was no different than hitting the brakes hard.

    There's a physical difference, of course, since regen only "brakes" the rear wheels but I found that it didn't make too much of a difference. I did not switch to "low" regen in the snow; that may completely eliminate any concerns.
     
  3. Matias

    Matias Active Member

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    #3 Matias, Apr 26, 2014
    Last edited: Apr 26, 2014
    Does car reduce regenerative braking if rear wheels get locked? If not, I guess this could lead to spin if you are driving on curve?
     
  4. EarlyAdopter

    EarlyAdopter Active Member

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    Hi Matias,

    The traction control works in both directions - accelerating and decelerating. If the car detects the wheels locking up under regen it will back off to prevent slidding. I've experienced this a couple of times under heavy regen down steep, slippery slopes.

    Coupled with stability control make the Model S very hard to spin (unless you turn TC off). Nothing to worry about.
     
  5. Jason S

    Jason S Model S Sig Perf (P85)

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    Last year I spoke with an early Sig owner who drove his Model S using summer tires throughout winter, at elevation (snow & ice on roads most of winter). He said he changed his regen from standard to 'light' mode to reduce the sliding and that worked better.
     
  6. dsm363

    dsm363 Roadster + Sig Model S

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    Driving on ice with summer tires is taking a big risk but glad or worked out for him. Guess that shows how well the system works even with the wrong tires.
     
  7. Jaff

    Jaff Active Member

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    I think lifting off the accelerator smoothly is key...my wife normally drives our MS...she tends to lift off the accelerator "a little too quickly" (imo) in snowy road conditions when she senses the need to slow down...she did feel that the regen was causing the rear end to slip a little...she switched the regen setting to low, and felt more comfortable after doing so.

    I am used to the stronger regen on the Roadster...I never felt the need to reduce the regen setting.

     
  8. mknox

    mknox Well-Known Member

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    This is something I was initially quite worried about (before getting my Model S) as I'd had an accident in a RWD vehicle when the car downshifted going down an icy hill. The rear wheels lost traction and I spun into a ditch.

    We had a brutal 2013/2014 winter and I can say that the Model S performed like a champ. No issues with regen causing traction problems at all. I think some of this may be attributed to the fact that re-gen is reduced in the cold and a lot of the time I wasn't getting the full effect.
     
  9. rdrcrmatt

    rdrcrmatt Member

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    The car does reduce regen braking when the rear wheels slow faster than the front wheels.


    they need to update the programming a bit for when the stability control kicks in.. I think the car should go full neutral until throttle or brakes are applied. It almost put me into a armco barrier the way it is programmed now.
     
  10. Matias

    Matias Active Member

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    I don't yet have Tesla, but I have read all posts I found in internet concerning this problem. At the moment the wisest thing to do is probably set regen. braking to low on icy conditions.
     
  11. Doug_G

    Doug_G Lead Moderator

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    In slippery conditions, suddenly lifting the throttle in an ICE car can also get you in trouble, as can lifting on low regen.

    Whenever you're at (or beyond) the limit of grip, the last thing you want to ever do is anything sudden. That includes accelerator, brake, and steering inputs.

    If you get on a patch of sheer ice, just neutralize the throttle and coast across it. Once you're on the other side then you can get the car back under control. Doing anything else is likely to put you in a spin or otherwise make the car uncontrollable.

    I've driven through two full winters now with full regen enabled. I just drive the car properly!
     
  12. simonog

    simonog Member

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    This is cause for a little fine tuning of the software: if this is indeed the case, it increases the chance of oversteer (a spin). Most road cars are set up to under steer to prevent the chance of spin.
     
  13. JohnQ

    JohnQ Active Member

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    I know you don't have this opportunity given your location but to others I would recommend driving in the snow before drawing conclusions. Push the boundaries and see how the car reacts to sudden steering, brake and regen inputs. I found that the S compensated for any overly aggressive driver inputs during the past winter and handled better than most cars I've driven. As @Doug_G said, drive the car appropriately for the conditions (and I don't mean gingerly) and you'll have no issues.
     
  14. rdrcrmatt

    rdrcrmatt Member

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    Agreed, there needs to be some adjustment to the process for after stability control kicks in before regen turns back on.
     
  15. mknox

    mknox Well-Known Member

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    Before I got my Model S in early 2013 I felt the same way. in fact, I was quite concerned. Having driven through one of the worst winters in recent memory, my fears have been allayed. I did put on a good set of winter tires (Nokian Hakka R2s) but found the regen behaved itself nicely. One "side effect" of the cold is that it does limit the amount of re-gen you get, which probably helped a bit too, and eliminated any need to set it to "Low".
     
  16. DFibRL8R

    DFibRL8R Member

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    Had one experience exiting I-95 at night at high speed onto an exit ramp that turns out hadn't been cleared of snow/ice. The sudden appearance of the bad conditions prompted an abrupt (too abrupt) lift off the accelerator and a bit of side to side through the patch but I was impressed with how the car managed to get through overall.
    I typically drive in snow and ice as if the brakes won't work but it takes some practice to habitualize that a sudden release of the accelerator is more like braking in the Model S.
     

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