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additional regen braking from the brake pedal finally?

Discussion in 'Model S: Driving Dynamics' started by bhzmark, Feb 18, 2015.

  1. bhzmark

    bhzmark Active Member

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    Of course the MS has had limited regen braking triggered from the accel pedal lift off. It also has had completely separate friction braking from the beginning.

    But starting with the autopilot cars, Tesla has been using the iBooster as a brake booster. That's specifically designed to apply additional regen when the brake pedal is applied and is designed to use regen for deceleration rates of up to 0.3 g. After that, it uses the friction brakes and it's designed to be so smooth that you can't tell where one stops and the other starts.

    The iBooster is made by Bosch and I've never seen any statements from Tesla about their implementation. I've never seen anything from them saying that they use regen with the iBooster, which is one of its primary features. I've never seen anything from them that says they use the iBooster only to integrate automatic braking with autopilot and don't use the regen braking capability of the iBooster for regular driving.

    I can't see why they would start using the iBooster and go out of their way to bypass a feature of it and leave untapped regen and make brake dust instead.

    Can anybody confirm that Tesla has said something one way or another about using regen with the iBooster from the application of the brake pedal?

    For add'l info see: http://chargedevs.com/newswire/boschs-new-ibooster-improves-regenerative-braking-2/

    https://www.youtube.com/watch?v=f8RsWGs7Ls0

     
  2. BerTX

    BerTX Member

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    I like brake control of regen in conjunction with the current implementation that Tesla uses. Prepare for there to be a lot of detractors on this forum, though. It's a hard sell to those who don't understand it or have never used it on other vehicles. I have never been able to explain adequately that this is in addition to the current system, not a replacement for it.
     
  3. Tedkidd

    Tedkidd Member

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    I MUCH prefer regen on the accelerator. One pedal driving is fantastic!!

    Smart has slight regen on the accellerator and more on the brake pedal. Tough to distinguish between brake and regen, which I don't like, and of course you have to use two pedals, which I really don't like.

    I really like paddles (Mercedes). Simple regen adjustment is REALLY REALLY nice. Paddles are the one option I really wish my Smart had. Bluetooth would be second (I love the car, it replaces our Gem, and has been such fun to drive I've put a battery tender on my sportwagen, but regen on the brake pedal is 1999 thinking that most have moved away from for good reasons).

    VW's shifter cycling for regen is better than nothing. BMW regen is kinda heavy since its not adjustable. Tesla adjustment via screen completely sucks. Not convenient to adjust while driving. Been a long time since I drove the Lead, so not sure about that experience.
     
  4. commasign

    commasign Active Member

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    It would be great if this feature was active (or at least available as an option) when using the low regen setting. On long road trips, coasting can reduce leg fatigue.
     
  5. Saghost

    Saghost Active Member

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    One of the most interesting quotes I came across recently was on one of the TACC threads, where in assuring folks that TACC does use the brakes to slow the car when necessary, someone commented about how odd it felt to have the car pull the brake pedal away from them.

    After reflecting on this, I think Tesla probably opted for the most direct brake feel possible in implementing the iBooster system - the brake pedal directly linked to the master cylinder plunger, with the electric motor also driving the same plunger.

    This would give the same feel/feedback as unboosted brakes, but without the heavy pedal forces, and allow instant response from the computer as well. One thing it would not allow is regen on the brake pedal.

    It seems like an unusual choice for the EV industry, but I can't think of another reason for TACC to be moving the brake pedal itself, and it does have advantages.
    Walter
     
  6. mibaro2

    mibaro2 Member

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    I love one pedal driving.
    However, this feature of regen from the brakes in addition to regen from lifting your foot off the accelerator will come in handy when you need to slam on your brakes. Either due to traffic suddenly stopping, etc.
     
  7. rdrcrmatt

    rdrcrmatt Member

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    Regen is dangerous to add in poor traction conditions. The back wants to pass the front quickly.

    I prefer the current setup, leaving rear biased braking to regen, then front biased braking to the brake pedal. Unfortunately most people don't understand why you'd use one vs the other when needed.
     
  8. invisik

    invisik Member

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    I do like the current regen setup and one pedal driving, but would love to make slowing down a consistent experience. The car should compensate with brakes to provide the same rate of deceleration no matter how much regen is limited in cold weather. It is always a little surprising when you come to the first stoplight and regen is barely slowing the car. The rate of deceleration of the car changes as regen is less and less limited, so you could have a different deceleration experience at multiple times while driving--and need to be on the ball enough to be ready for it.

    I see this is a major problem for the Model 3 with less experienced/in-tune drivers trying to figure out how much brake pressure they need depending on regen.

    They need a "Use regen while braking only" option in addition to the current options--especially for people to regularly drive multiple cars (elec/gas) or don't get it.

    -m
     
  9. mibaro2

    mibaro2 Member

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    I had thought about that, But :
    Problem with that is since the battery is so cold, you can't regen to it...no matter how you do it.
    Maybe they will have to have a battery heater to keep the main battery warm enough to accept regen (only active when plugged in so it won't take away from your range) , or something like that.
    You are correct...the first stop is always a surprise one, and it won't work for the masses.
     
  10. David99

    David99 Active Member

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    There are 50k Model S on the road. Not a small number :)

    But I do think having extra regen on the brake pedal (whatever the technical solution to that is) makes a lot of sense. For normal driving you hardly touch the brake. The normal regen is perfect. Sometimes we need to stop faster and it is very easy to get higher regen out of the motor for those moments, triggered by the brake pedal. At the same time, the energy gained from these rare moments of hard regen isn't really making a difference.
     
  11. invisik

    invisik Member

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  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    How, this already happens when you lift your foot. Putting regen on the brakes will just lengthen the stopping distance as full regen won't be on the accelerator pedal anymore. It will also cause that transition feeling when the system decides to stop regenning on the brake pedal.
     
  13. billarnett

    billarnett Member

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    But that's not an issue with the AWD models :)

    - - - Updated - - -

    "Normal" is the same for everyone. In *my* normal driving I'm always having to use the brakes (a little) because the max regen just isn't quite enough for the way I want to make ordinary stops. I would be much happier if max regen was about 2x more force. Optionally, of course.
     
  14. Tedkidd

    Tedkidd Member

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    Another vote for paddles?...
     
  15. billarnett

    billarnett Member

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    Paddles seems like overkill to me. And it would be a hardware change and therefore useless to me and the rest of the existing fleet. It seems to me it would just fine to add another option in the regen settings for "high" in addition to standard and low.
     
  16. bhzmark

    bhzmark Active Member

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    Why do you think full regen, especially with the AWD D cars, is available on the accel pedal? Other threads say the braking effect from lifting off the accel seems have gone down.

    The point is the braking effect from the regen triggered by the accel pedal is EXACTLY AS IT NOW. But ADDITIONAL braking effect from regen, i.e., a harder and faster stop using the regen, can be triggered by the brake pedals.

    As noted above, some people seem to not be able to contemplate the idea that triggering additional regen braking from the brake pedal is even possible, but with the ibooster it should be possible.
     
  17. Tedkidd

    Tedkidd Member

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    Hmmm. But easier to access and change.

    Maybe an optional setting on the stearing wheel buttons or roller.
     
  18. strider

    strider Active Member

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    #18 strider, Feb 20, 2015
    Last edited: Feb 20, 2015
    The last part of that statement is wrong. THERE IS NO SUCH THING AS UNTAPPED REGEN IN A TESLA. Tesla has defined maximum regen as 60kW. Many factors went into that decision like ability of the pack to accept charge, traction, passenger comfort, etc. Tesla then decided to apply 100% of regen on the accelerator and 0% on the brake pedal. Other manufacturers will apply say, 30% of their max regen on the accelerator and the remaining 70% on the brake pedal. It still adds up to 100% of that manufacturer's max regen amount. So the only way to add regen to the brake pedal is to subtract it from the accelerator. Whether max regen can be higher than 60kW is something only Tesla knows. Yes, a D car has more traction available since it can regen through all 4 wheels. But there could still be limitations on the rate of energy that can flow into the pack since that energy has to go somewhere and has to be routed through the AC/DC conversion in the PEM (as opposed to DC direct into the battery in an SC).

    Tesla needed an electromechanical system for actuating the brakes and this unit can do that. I don't know what other vehicles use this system's regen feature but in Car and Driver's review of the i8 they complained about the sharp transition from regen to friction brakes. I've personally never driven a vehicle where that transition is smooth. Granted, I haven't driven every EV and hybrid out there.

    Please don't complicate the system with paddles or brake-pedal regen. Just use your foot! Simple is better. It just works. Does it take some getting used to? Sure. But it's no different than when we switched from column-mounted throttles to the floor pedal we're used to today. Don't mess up an elegant system just because it's different.
     
  19. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Because full regen means all the regen that Tesla gives you.

    Not trying to be funny, but there are threads like this after every major upgrade. If every thread that had this was true, there would be zero regen by now.

    The result would not be pretty. If you have regen on the brakes:

    1. There needs to be complex software to determine when to use the friction brakes and when to use regen.

    2. When any of the safety devices kick in, regen on the brakes stops because TC, VCS, ABS, etc. all rely on precise control over the friction brakes. This gives you a short time where it feels as if the brakes have gone away anytime you brake on an expansion joint, washboard surface, or pothole.
     
  20. billarnett

    billarnett Member

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    Ah, finally, a theory about why they did it this way that makes sense. I spoke to JB about this issue way back before the Roadster was released. He said at that time that the issue was that too much regen on the rear wheels only would cause handling difficulties. Which makes sense. But not with the AWD cars. So maybe they just stuck with that level of regen force on the S and engineered the PEM for that much but no more. I sure hope not. The P85D would feel a lot nicer with about 2x as much regen force, IMHO. And if it applied,a little all the way down to zero so you wouldn't always have to use the other pedal at every stop sign.
     

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