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Simulated regen braking option?

Discussion in 'Model S: Driving Dynamics' started by Bucket22, Jan 23, 2013.

  1. Bucket22

    Bucket22 P85 / #3287

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    The last few days, I've had to park my car unplugged all day in very cold conditions. When I've started my trips home, regen braking has been disabled until the battery warms up, as has been discussed in many other threads. Personally, I've found it to be a radical difference in driving dynamics without regen braking. (And I've only had a week and a half to learn new habits!) As when I occasionally drive ICE cars now, I feel like the car is "getting away from me" when I take my foot off the accelerator and expect the car to start slowing.

    My question is whether folks think it would be technically feasible and desirable to have a simulated regen braking option, where the car slows as it normally does when one takes one's foot off the accelerator, even if the energy created by the slowing isn't being captured by the too-cold battery. I understand that this would negatively affect range because energy is being wasted in braking. But I would like to have a virtual switch that allows that choice alongside the ones for creep and steering and suspension height.
     
  2. Longhorn92

    Longhorn92 MS VIN #10103 (40 kWh)

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    Bucket22: I like the idea of a faux regen option in cold weather for those who want a consistent driving experience; however, I would be surprised if it is technically feasible without some sort of hardware change.

    Also, thanks for the help this last weekend. The electrician is coming back out today to fix.
     
  3. raptorweb

    raptorweb Member

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    Someone correct me if I am wrong but to keep the regen feeling that you normally get via the motor would require a large resistive load to dump the generated power. Some have said that it would be nice to dump that power into the heating of the battery/cabin but those combined would still be a small part of the 60kw regen is capable of.

    As for doing it with brakes, I wouldn't want to be wasting the pad's just for the consistent feeling even if Tesla replaces them as part of the service plan.
     
  4. Babylonfive

    Babylonfive Power12

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    I don't think that anything would be 'wasted' (assuming a 60kW resistive load could be added) because the battery is already full and/or too cold to accept the charge, so there's no place else to put that energy anyway. Since the purpose (which I agree with) is to be consistent with 'single-pedal' response feel, it's very similar to when you would already use the brake - again, no actual waste would occur. It wouldn't affect range because the battery is already full when this happens.
     
  5. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    Yeah, but we're wasting the pads anyway.

    How about a large ultracapacitor to soak up regen braking energy? Round-trip efficiency should be better than recharging the battery, too.
     
  6. raptorweb

    raptorweb Member

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    This is true, I guess I was thinking more of the times where when regen is working I would use it to slow down a little but when its off I just coast instead. For full stops your right your using them either way if regen is off.
     
  7. Mike_Schlechter

    Mike_Schlechter Model S - P457

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    I have to say, after having no regen twice lately, I'd love if it had something that equated to regen, and like the idea of dumping the energy as heat, given it was extermely cold out both times. However, I doubt that is coming any time soon, and just need to be ok with it.

    That said, I can assume that Model S's in norther climes will likely have more brake wear than those in the warmer locales. Bummer.
     
  8. Doug_G

    Doug_G Lead Moderator

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    I doubt the brake wear will be much greater. The regen comes back after a bit of driving. Also weather varies... it's not always so cold. (Ccccold here today though!)
     
  9. Mark Petersen

    Mark Petersen Model S EU P71

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    well if you set the regen to low, the difference between low and limited is much less
    and you therefor get a much more consisten feeling
     
  10. Enadler

    Enadler Member

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    When regen wasnt available due to cold, brakes could be applied when the foot is removed from the accelerator to simulate the braking effect of regen. Yes pads would be worn but the alternative would be that you would need to apply the brake anyway. This solution would simply allow for the driving dynamics to be unaffected by a temporary loss of regen.
     
  11. jerry33

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

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    It would be very tricky to do this and get it right. Tesla could burn though a lot of R&D dollars doing this--perhaps as much as the motor design. One of the great things about Telsas is that the braking system and the motor and drive train are separate. This makes the car very robust and probably takes $10,000 or more off of the price of the car. Right now Tesla basically purchases brakes and installs them. It's a known quantity and not much has to be done for design and testing. To do the combined bit, they would have to develop their own braking system, and if they had a couple of reviews/incidents where there were brake problems, they would likely never recover.
     
  12. dsm363

    dsm363 Roadster + Sig Model S

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    I think a much more obvious warning about reduced generation (that is linked to driver profile and could be turned off) would get us most of the way there.
     
  13. pilotSteve

    pilotSteve Member

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    I find myself always mentioning to friends that I let drive my car to "remember you may have to use the brakes"..... its just a question of when. Certainly cold with limited regen is one of those times, as is panic stopping. But even stoplights sometimes need brakes, but not always.

    Not a problem to me as YOU drive the car (and make it stop) not the computers. Use brakes when you need to and always be prepared to.
     
  14. mknox

    mknox Well-Known Member

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    I'm not buying all this "saving brake pads" stuff (not directing this at you, stevezzzz. Just a general comment). My '09 Cadillac CTS has over 75,000 miles and is on the original pads and rotors. No brake repairs have ever been required (although I have had them inspected and cleaned). Maybe re-gen will extend brake life from 4 years to 6, but is this really that big a deal?
     
  15. jerry33

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

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    More like 10-15 years in my experience. Neither my 2001 nor 2004 Prius have ever required brake pads and there is still a ton left (100,000/145,000 miles). There was a picture posted a few years ago with a Prius with 180,000+ miles on it and the brake pads looked like new. Here is an article from a Canadian Taxi company. The relevant quote, "We change the brakes on a Toyota Corolla every seven to eight weeks, but on a Prius we change the brakes every 18 months or so". Regenerative braking really does reduce brake wear.
     

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