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Black Ice and Regen: bad combo?

Discussion in 'Model S: Driving Dynamics' started by scottm, Nov 13, 2015.

  1. S4WRXTTCS

    S4WRXTTCS Active Member

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    I honestly don't understand the ENTIRE cold weather functionality of this car. They desperately need a Canadian Engineering office.

    There is no heated front windshield. The cold weather heated area under the wiper doesn't count.
    There is no ability to pre-heat the battery for those of us that WANT regen in the morning (when it's in the 40's F). Without having to pre-heat the entire cabin.
    There is no off setting for regen
    There is no auto setting for regen (should be the default setting)

    In really cold weather odds are the regen is going to be really low so why not just turn it off when the roads are near 32F?

    I don't understand why we're even talking about driver training camps, or GOOD drivers. All kinds of people with different levels of experiences, and expectation of how the car is going to handle are driving the Tesla MS. Because of this the Tesla MS should default to a setting that is similar to an ICE car in this situation.

    You know how hard it is to retrain muscle memory? What if a person goes from an ICE car to this car on a fairly regular basis?
     
  2. chickensevil

    chickensevil Active Member

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    Wait, I'm confused, you guys act like you have experienced the car losing traction (legitimate loss not the minor corrections that it makes without even lighting the TC light). I say this because when the car detects loss of traction (which it can do far better than you can, and quicker), it cuts power. Period.

    This means if you are positive throttle it brings you down to neutral and if you are negative throttle (regen), yep, you guessed it, it brings you up to neutral. It does this until it regains some amount of traction and will try again to apply the "brakes" (regen). It works very similar to how ABS works (where it will pump the brakes for you), only it will "pump" the regen. That is to say it will cut regen power, gain back an amount of traction, and then reapply the regen. It can be very disconcerting, but I think most people drive in the snow incorrectly in the first place and forced "neutral" isn't likely the best choice for anyone except a professional race car driver (which the vast majority of people are not). I appreciate that on the Dual Motor cars you can't even fully disable traction control, and stability control is always forced on. The reason this is good is because you probably don't realize just how much instant torque you have and you are going to fry out your tires meaninglessly applying power to it. Or over react in the other direction and slam on the brakes, again, causing more issues.

    But no, the car works just fine with respect to regen, I suggest sometime you get going on a nice straight open road, slam on the brakes and *watch* the regen meter. At the same time it is applying the ABS on your brakes, it is cutting power to the regen. Note that the screen has a little bit of lag to it over what the computer is actually telling the car to do, but you can totally feel in in the peddles and the wheel.

    I make no claims to being the best driver in snow, but I have never felt more safe and in control than I have in the Tesla, and this is having driven it in various snow conditions (VA is right on the line so we get the 1 ft of snow all the way to the freezing rain/icy roads) and done it in just standard 19" all seasons. Sure if it snowed enough around here I would actually bother to get snow tires (or if I had 21's those are almost a must to switch out), but I feel very much in control over the direction of the car and I even, in safe areas, got to test the car a bit to see how it would respond to situations and it handles it exactly like you would want it to (and far better than anything I could do). To include a moderately spirited throttling on a left hand turn intersection forcing the car to kick out. This was one of the better ones I tested since it showed me how the car is really great at handling the rear end kicking out and all the systems taking over to pull you back on the straight and narrow.

    Disabling regen would just be more problematic than it would be worth. And those that would do that would be more likely to resort to their brakes instead (what they are used to) when the car is better able to control the handling and traction with the regen than the brakes. I think you need to learn your car a little bit better, and don't do it under conditions where you are pressured into being somewhere. Next snow, take some time to go LEARN your car and build confidence in both your own capabilities and how the car can react to things. Please don't wait until it is 5PM on the way home from work, you are tired, and annoyed by the traffic, and in the middle of a snowstorm/freezing rain. That is the *wrong* time to be figuring out how your car works.
     
  3. vgrinshpun

    vgrinshpun Supporting Member

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    100% agree with Chickensevil. Response time of ABS is 1/10 of a second. Response time of torque control by the Tesla drivetrain (including regen) is 1/1000 of a second with much better modulation.

    I do not mind having regen off button, but it will not be used on my car.
     
  4. chickensevil

    chickensevil Active Member

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    To be clear, I don't have an issue if they added a regen disable button, but it should be surrounded with a bunch of warnings and "ok" buttons just as traction control was.

    It also would see no use in my car. I don't ever even drop it into "low" mode and would love to see a "high" mode with stronger braking, maybe down to 120kW? I would much prefer to never use my brakes, even in the snow.
     
  5. tomcherv

    tomcherv Member

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    Quick thought: how many know what "Black Ice" is and have encountered it?

    Black ice is completely different than ice - it's worse.

    Black ice is created during extremely cold conditions (definitely below 0 F) when vehicle exhaust freezes onto the roadway. It is rarely visible and very slippery.

    Of course if everyone was driving a Tesla, we wouldn't have Black Ice to worry about in the first place.
     
  6. vgrinshpun

    vgrinshpun Supporting Member

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    Just to make the choice clear, when car is traveling at the speed of 65mph, the ABS system, due to it's latency, responds to the road condition that car passed 1/10 of a second prior, which is equivalent to 9.5 feet of travel. For the same speed, regen reacts to a road condition that car passed 1/1000 of a second prior, which is equivalent to 1.1 inch.
     
  7. Matias

    Matias Active Member

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    Do you know this? If it is so, I have no problem with regen. I'm affraid, that it keeps trying to apply regen all the time.
     
  8. ecarfan

    ecarfan Well-Known Member

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    Black Ice and Regen, bad combo

    Thank you @chickensevil for your very lucid and helpful post.
    Even though currently I live in a very moderate climate, I have also lived in Wisconsin and Canada so have some experience driving in harsh winter conditions. I am sure that many Tesla engineers have also lived and driven in snow and ice despite the fact that they currently live in California, as do I. They know how to engineer cars for those conditions. We know Tesla tests their cars in those conditions and has the advantage of working with vehicle systems that are far more responsive than traditional vehicles and can also react far quicker than humans can.
    The beginning of this thread is a classic example of a user (in this case, a "driver") misinterpreting how a system reacts to a real world condition and then making the assumption that they know better than the system designers and should be given the ability to override the system.
    Note that for years now the Model S (and the Roadster) has been highly respected in Norway for its handling capabilities in ice and snow.
     
  9. mknox

    mknox Well-Known Member

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    This was something I was VERY concerned about prior to taking delivery of my car. I recounted a number of times how I'd had a spin-out with a prior RWD ICE car when, going down a hill, the Cruise Control downshifted the car to maintain speed and there was back ice, unbeknownst to me. Very similar to the re-gen scenario... engine braking on the rear wheels only. I'm now heading in to my 4th winter with my Model S and can honestly say I have not once experience this kind of problem with the car. I've even tried to "induce" it on slippery roads (with no other traffic around) to see how it would behave. If I try, I can get a bit of wiggle and all sorts of ABS and/or TC noises and lights, but the car seems to do a pretty good job of maintaining composure.
     
  10. Matias

    Matias Active Member

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    Ok. Good to hear.
     
  11. DMC-Orangeville

    DMC-Orangeville 85D and John Deere 5100E

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    It's not exhaust, typically. It's ice "dew", when the air really cools down over night (0F / -20C), and is particularly prevalent on bridges and overpasses. It is nearly invisible, and turns the asphalt into ice, similar to an ice pebbled curling rink. I lost a convertible to it on an overpass on HWY 11 near North Bay Ontario. My daughter was driving it, touched the brakes, spun counter clockwise into the concrete rails, and continued to spin the other way into the concrete on the other side. The car is a pinball - no road resistance.

    The car was smashed to pieces - my daughter walked away with bruises.

    Black ice is the scariest hazard we face in the winter, as there is no preparation for it other than keeping your speed down, and your foot away from the brakes.
     
  12. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    It's the ESC that really helps here. I was worried about losing the rear of the car as it dragged down due to regen, but found that the moment the car gets slightly off-axis, the car does a pretty good job at applying all sorts of tactics to get it back on path again. I've had the rear wheels lock due to regen on slippery snow and ice (including black ice), and while the feeling is disconcerting, the car recovers well as long as you know how to respond to it.
     
  13. Skotty

    Skotty 2014 Model S P85

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    Not sure how good a Tesla is, but in a modern high-tech car, the only thing the driver should have to do is to say go or stop. It should be up to the car to manage the road conditions in as best a manner as possible. Of course, in the wrong situation, like moving too fast on an icy patch when needing to stop, it may be impossible for the car to avoid an accident, and the car can't do the impossible no matter how good it is.

    Point being, you shouldn't have to worry about special considerations for regen and icy patches -- the car should handle that concern. Whether or not a Tesla does this, I don't know.
     
  14. vgrinshpun

    vgrinshpun Supporting Member

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    It did for me so far (2.5 years, 46K miles) - under the variety of adverse conditions.

    Every time I've seen "regen-bad" posts, which are appearing regularly during the cold part of the year, I tried to provoke my regen into "bad" behavior, with inevitably, stubbornly good (for the ultimate stability of the car) results.
     
  15. AWDtsla

    AWDtsla Active Member

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    So, the driver cannot abdicate responsibility for driving the car during autopilot use when the car is driving itself, yet the driver abdicates all responsibility of keeping the car within the limits of traction because ABS, and stuff... Got it, makes perfect sense.

    Someday the car will drive better than any human can possibly do, but that day is still 5-10+ years away.
     
  16. Skotty

    Skotty 2014 Model S P85

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    Nope. Generally the driver is always responsible. I wasn't commenting on responsibility; I was commenting on capability. While autopilot and self driving cars may still be years away from perfection, eliminating wheel slippage should really already be mastered. Still, I'm not opposed to being able to turn things off if the driver really wants to manage everything herself.
     
  17. hdsm

    hdsm Member

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    Agree completely + we should have a better alarm that informs the driver the road is slippery
     
  18. yobigd20

    yobigd20 Well-Known Member

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    regen should have the option to be disabled. i have also experienced loss of traction when lifting the accelerator up and regen kicking in hard when on ice and snow. it's very very dangerous.
     
  19. vgrinshpun

    vgrinshpun Supporting Member

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    The two applicable questions are whether you intended to slow down when you lifted up the accelerator, and did car ultimately maintained the desired course. Depending on the answer to these questions, it is possible that if regen on your car was disabled you would've been worth off than with regen active.
     
  20. Soolim

    Soolim Member

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    I imagine that regen SHOULD work interactively with traction control and ABS, regardless of the user setting of the regen. Thinking of where I can try it safely.
     

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