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Braking regeneration

Discussion in 'Prime Main Forum (2017-2022)' started by D.A.L, Sep 14, 2019.

  1. D.A.L

    D.A.L New Member

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    When coming to a stop light or stop sign, how much braking regen can the batteries suck up?
    Is slow gradual braking best to regen or will the batteries still suck up a more aggressive braking regen just as well?
     
  2. drash

    drash Senior Member

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    Well the battery can take quite a bit of regen, because it’s only for a relatively short period of time. The highest regen I’ve seen via the OBD program I use is about 27.6kW over a 2 second span when slowing down from 30 to 21 using B and hitting the brakes. Personally I try and coast or glide as that’s more fuel efficient, but getting it to glide is difficult and takes a lot of practice.

    Added: Conversely, accelerating is by far harder on your battery and electronics than braking. You can only press the brakes so far before the friction brakes are engaged. On the same trip I hit between 35 and 40kW five times accelerating and for longer periods of time (hills suck).

    For comparisons: cruising at about 52 mph takes about 29kW.

    iPad ? Pro
     
    #2 drash, Sep 14, 2019
    Last edited: Sep 14, 2019
  3. bisco

    bisco cookie crumbler

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    slow and gradual is better. not because of the battery, but because the harder you push the pedal, the more friction braking you do, and the less regenerative.
     
  4. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Who knows. Lots of speculation, but hard to say.
     
  5. D.A.L

    D.A.L New Member

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    "slow and gradual is better. not because of the battery, but because the harder you push the pedal, the more friction braking you do, and the less regenerative."

    Makes sense. Thanks.
     
  6. bisco

    bisco cookie crumbler

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    pleasure
     
  7. Salamander_King

    Salamander_King Senior Member

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    I am not sure if this info exists on Plus model, but on Premium and Advanced model with 11.6 display, you can check the numerical value of regenerated electricity under INFO, ENERGY, and Battery.

    It is per minute and per trip value and it reset for each trip. You probably want to compare per trip number in two travels on the same route under similar conditions one with hard braking vs another with slow gradual braking.

    IMG_20190529_074744.jpg
     
    #7 Salamander_King, Sep 14, 2019
    Last edited: Sep 14, 2019
  8. Marine Ray

    Marine Ray Senior Member

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    Do you have to manually reset or is it reset when turning off the car?
    Posted via the PriusChat mobile app.
     
  9. Salamander_King

    Salamander_King Senior Member

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    It's reset every trip automatically when you turn off the car.
     
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  10. mr88cet

    mr88cet Senior Member

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    As far as I can tell, that’s indeed true, but it doesn’t need to be “waaaay slow” to get good regeneration. Normal, well-pre-planned braking works great.
     
  11. JayGen4

    JayGen4 Member

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    What is known about how much or how the Prius decides how much Regen is working? I just learned recently that the brake pedal controls both but of course the computer probably jumps around between either. Hybrid brakes, essentially.

    Just curious. I've driven Tesla a lot and love the Regen on those.

    Is brake pad life a lot longer on the Prius due to some of the friction coming from Regen? It certainly is on the Tesla.
     
  12. Tideland Prius

    Tideland Prius Moderator of the North
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    Yes. I do nearly all city driving (highways only out of town or if I’m driving to the US) and the brake pads on our 2005 Prius last the life of the car - 245,000km.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Once more for the reminder that it's most efficient to drive so there is as little need for braking as reasonably practical. To focus on making "watthours regenerated" a big number is not an efficient strategy; having a car that can regenerate is better than one that can't, because at least you can use some of that energy again, but you pay a tax on it in both directions, into the battery and back out later.
     
  14. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    I thought that Tesla had "one-pedal" driving: you are expected to use only the "gas" pedal to speed up or slow down. And that the brake pedal was 100% friction braking (no regen).
     
  15. JayGen4

    JayGen4 Member

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    Yes and yes. I was referring to the Regen that kicks in right away as you ease off the acceleration.

    Very glad to know the Prius makes better use of the regen than just coasting. However, I think the way Tesla does it modulates much better. The Prius has a way of unpredictably deciding that it is time to apply the friction brakes and it is a little jerky sometimes where as my braking is always consistent in the Tesla.

    In other words, the Tesla doesn't decide when the friction brakes are applied; I do. However, the regen while coasting is dramatically more intense but you get used to it and the instantaneous response when you want it is very nice and dialed without having to use the brake pedal 98% of the time or so.
     
  16. jerrymildred

    jerrymildred Senior Member

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    Don't forget that the Prius was designed to be a familiar driving environment for people coming from old fashioned cars. Elon took a different approach that doesn't pay as much attention to tradition. So the Prius is programmed to simulate engine braking when you lift your foot off the accelerator. Tesla took a different approach. I can't see either being particularly better or worse, just different.
     
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  17. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Just 3rd gen here, but gotta say I've rarely if ever noticed odd about the braking. I wouldn't think 4th gen has changed?
     
  18. Trollbait

    Trollbait It's a D&D thing

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    Blending control of both braking types on one pedal was a challenge. Toyota has been improving the feel over the Prius generations.

    In addition to the different approach, battery capacity is a factor in how regenerative braking performs. Give the Prime the control of regen on the accelerator like the Tesla, and the amount of regen braking will be less because the battery sizes dictates how much energy it can take in at once. It will also reach full charge sooner. So you'll be switching to the friction brake manually sooner than with a Tesla.
     
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  19. JayGen4

    JayGen4 Member

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    Also good point.

    Too bad they didn't fit in a larger battery and a little stronger default regen. I think that's something Prius users would happily welcome if the marketing points are made clear. But perhaps they are scared to take that risk but honestly I think it makes the car that much more competitive.

    That's a good point. Ultimately I think that decision leads to a more poorly modulated braking experience but the average user is much less sensitive to that and much more to the aggressive regen of a Tesla. I think the Tesla is still more efficient and mostly due to being more responsive and better feel. Plus, you can adjust the intensity but then we're just making unfair comparisons.
     
    #19 JayGen4, Mar 20, 2020
    Last edited by a moderator: Mar 21, 2020
  20. ChapmanF

    ChapmanF Senior Member

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    The most noticeable time is when slowing moderately and then having one tire encounter a pothole, manhole cover, etc. Its fairly reproducible under those circumstances. You may not have noticed it, but it also generates a fairly constant stream of new PriusChat postings from people thinking their brakes are failing.