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Does using the accelerator to hill-hold harm the motor?

Discussion in 'Model S' started by realyc, Apr 23, 2017.

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  1. realyc

    realyc Member

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    I like driving very smoothly when there are passengers in my S, especially when stopping at a light. I obsess on bringing the car to a perfectly smooth stop without feeling the suspension jerking back. It's really hard to do it when stopping uphill though :p so I sometimes use the accelerator to keep the car at 0 speed. I know that with a small toy-sized motor if you hook it up with a battery but don't allow it to spin, it'll burn out, so that leads me to wonder if doing so with a Tesla motor also harms it. What do you guys think?
     
  2. one5n1neSDoo

    one5n1neSDoo Member

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    Interesting question... Even more interested in the answer.
     
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  3. Hugh Mannity

    Hugh Mannity Mediocre Member

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    It doesn't sound like it's good on the motor but that may be just the brush type that it would be hard on, which the Tesla does not have. Am interested in hearing what the technical experts respond back with here as well.

    Just use the vehicle hold on hills.
     
  4. Haxster

    Haxster Member

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    A related question:
    When hill hold is engaged going down a hill, there's a message to push the brake to release it. If you ignore this and just push the throttle, does this stress the brake caliper or the release mechanism? (It's not a smooth release.)
     
  5. roblab

    roblab Active Member

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    In my car, hill hold goes on with very slight pressure, so I say it's often on at a light. Touching the go pedal will immediately kick off the H and we roll away. Yes, there's some noticeable click and clack, but mine is quite smooth, as I say, at a light. If I were on a hill, it might be more, but I doubt there is much harm to a brake caliper that can be applied at high speeds in an emergency situation. I wouldn't worry about it. And I wouldn't use the motor to hold the car, simply because to my mind that's what brakes are for.
     
  6. mal_tsla

    mal_tsla Member

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    No it doesn't hurt the motor. There is nothing in contact inside induction motors.

    The motor is barely powered to hold the car on most hills. Creating torque is the same as when driving.

    Look at the energy meter while holding on a hill. Compare that to normal acceleration. The motor generates heat when the value in the energy meter is high.

    Pressing the accelerator to release the hold friction brake doesn't hurt anything either. The car is moving not even one mph when the release occurs. Stopping for a red light even once from 50mph would wear those parts more than many many years worth of hold releases.
     
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  7. brucet999

    brucet999 Active Member

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    Why would you do that instead of just pressing hard on the brake pedal for Vehicle Hold?
     
  8. Joelc

    Joelc Member

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    It's a feature not available on every Model S. My 'classic' non-AP Model S P85 for example doesn't have it.
    I don't know when permanent hill-hold became standard.
     
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  9. bishoppeak

    bishoppeak Member

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    It is smoother than applying hill hold and then accelerating, especially on a steep hill.
     
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  10. realyc

    realyc Member

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    To clarify - I do have vehicle hold, but there's still a slight (I'm being very picky here) jerky motion when using the brake pedal to stop on an upward hill. I have to time it so that the instant (H) activates, I'm neither going forward nor rolling backwards - the latter gives a worse experience. It's more of an obsession than necessity :)
     
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  11. No2DinosaurFuel

    No2DinosaurFuel Active Member

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    If you come from a manual shift gear car, hills are no problem. Just press thr brake and quickly switch when it is red. No need for hill hold or throttling to keep the car from rolling backward. That is how you do it in a manual. Don't ride the clutch as they would say.

    But going on 0 rpm with current, it is definitely bad for any EV motor. But like others have said, as long as it is not too long the temperature rise due to the stall motor is not that much especially when it is a larger motor like the one in your p85 and at low current because it doesnt take much to keep the tesla from rolling back.
     
  12. HankLloydRight

    HankLloydRight Fluxing

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    I was going to add, I think the concern is that when you stall the EV motor by holding it in one position, the stator is energized with the rotor in one fixed position, pushing current through the same set of stator coils, which are usually only energized for short moments when the motor is normally rotating, generating more heat in those coils than normal. Now I don't know how much more heat is generated doing that, or how long before any damage is done (probably a long time), but like @No2DinosaurFuel said, just don't do it for long.

    I like rocking the car back and forth a little bit with the accelerator on a small hill waiting for a light. Kinda fun. Passengers usually don't find it as fun. :)
     
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  13. daniel

    daniel Active Member

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    I think that coming to a perfect stop without that slight jerk at the end is called a chauffeur's stop. I've never managed it, though I always try. But I'm just a regular driver, maybe a little below average, but I think not a lot.

    This being the internet, I will talk through my hat and give my opinion: I think that applying power to the motor when it is not turning is bad for it. But I'd imagine that Tesla's motors are engineered to tolerate some abuse. So if it's a lot of fun and you're willing to pay the price of putting some additional stress on the motor, hey, go for it. But if you're as compulsive about maintaining your car's health as you are about giving your passengers the perfect ride, it might be better just to learn to do a chauffeur's stop and start without riding the go pedal at a stop.
     
  14. SabrToothSqrl

    SabrToothSqrl Active Member

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    Ya'll worry too much. 8 year infinite mile warranty. Hold away.
     
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  15. Doug_G

    Doug_G Lead Moderator

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    I have a classic P85 and no hill hold, so I've done this occasionally. The amount of power being expended holding the car on a hill is trivial - easily verified by noting the power meter on the console. Driving at any speed uses more power. It's a brushless motor so there's nothing to wear. The power electronics are not going to get hot because they're designed to handle far more current continuously for hours. So all you'll do is waste a small number of electrons.
     
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  16. HankLloydRight

    HankLloydRight Fluxing

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    Mostly true, but when you're holding the motor in a fixed position at 0 mph, the stator coils which are designed for thousands of short pulses per second to turn the rotor are not really designed for constant current being applied, even at "low" power levels. With each short pulse under normal use, even at high power levels, there's also a short cooling-off period between each power pulse. The coils do not get this cooling-off period when constant power is applied, so they heat up quickly.
     
  17. ThisIsTrue

    ThisIsTrue Dismember

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    Exactly! Why, doing this means the motor won't fail for at least 96 months! After that, you'll pay for the replacement. :rolleyes:
     
  18. _jal_

    _jal_ Member

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    I thought they used variable frequency drives so it's nothing more than just low current in the coils delivering whatever power needed to keep the car from moving. There's no switching occurring. The wheels don't turn because the induced field in the rotor isn't sufficient to make it turn, but that shouldn't cause any problems.
     
  19. HankLloydRight

    HankLloydRight Fluxing

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    Right, there is no switching, so the coils still have constant current running through them, yes, enough to keep the rotor from turning. That doesn't mean the coils aren't heating up.
     
  20. _jal_

    _jal_ Member

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    They always have current running through them though unless you don't have your foot on the accelerator :-/
     

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