Regeneration: Coasting vs riding the brakes, which is better?

Discussion in 'Gen 4 Prius Main Forum' started by FuriousPrius, Sep 8, 2021.

  1. FuriousPrius

    FuriousPrius New Member

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    As the title says, what's the preferred and safer approach when coasting to a stop. Can I lightly ride the brakes while coasting, especially downhill?

    My worry is that this will engage the calipers and burn the brake pads faster, as there doesn't seem to be any indicators on whether the regenerative braking or hydraulic braking is the one active when slowing the car down.
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    I'd suggest - don't worry about it. Just don't drive aggressively if you're trying for max economy, but then, don't hold traffic up either - it annoys them.

    Wearing brake pads WILL NEVER be a problem with a PRIUS, unless, as mentioned earlier, you drive aggressively. They could well last the economical life of the car.

    Just enjoy it.
     
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  3. PtPri

    PtPri Junior Member

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    AFAIK... The brake pads only operate in two conditions:

    1 - if you exceed the "CHG" indication on the Hybrid system info screen/table, ie, if the blue bar fully fills that graph, and you press further on the brake.

    2 - When at very low speeds.


    So, if you drive normally and are aware of what's going on in front, the car will manage and prioritize regen beautifully.
     
  4. james nancy

    james nancy Junior Member

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    I agree with this view. Generally, braking is basically regenerative braking, except for the two conditions mentioned in the appeal. I have tried it. There are uphill, downhill, fast and slow speeds. I don’t like intense driving. I stopped and touched the front and rear brake discs. There is almost no temperature, that is, the brake disc usage rate is very low, and a lot of mixed The power car did not need to change the brake pads even after running 150 thousand kilometers.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    On my C, there is one display that shows (among other things) the relative amount of regen braking so you can tell about when the "switch over" will occur.
    I suspect yours has that too and you just haven't found it yet.
     
  6. fotomoto

    fotomoto Senior Member

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    My personal guide is if I can feel seat belt pressure on my chest, I’m approaching or already in the “brake pad zone”. FWIW

    My C-Max has a brake coach. Toyota and Honda use scores/ratings at the end of the trip. Power gauges. Lot of help/feedback is available to the driver.
     
  7. jerrymildred

    jerrymildred Senior Member

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    There's an Android app called Hybrid Assistant. It will show when braking is by regeneration and when it's by friction. In general, most of the stopping is regen until the last few mph unless you're stomping on the brakes. Here's one example video by @john1701a.


    The most efficient, if you have time and room and some belchfire V8 isn't breathing down your neck, is to glide with neither propulsion nor regeneration, letting rolling resistance slow you. That way no energy is lost to conversion heat. But those conditions are pretty rare.
     
    #7 jerrymildred, Sep 9, 2021
    Last edited: Sep 9, 2021
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  8. FuriousPrius

    FuriousPrius New Member

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    Interesting, I may have to look into this. What are those 5 brake pad icons below the big rotor icon? Is that indicating brake pad life?! If so, how are they sensing that?!
     
  9. alanclarkeau

    alanclarkeau Senior Member

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    One of the best clues is in your HUD:
    upload_2021-9-10_9-23-13.png

    If the GREEN goes below here:

    upload_2021-9-10_9-23-45.png

    You're regenerating.

    ++++++++++++++++++++++++++++++++++++++++++++

    If it goes a long way below, like below this line, there's a chance you could be using your brakes. I suspect it isn't a perfect representation, but will give you a good idea:

    upload_2021-9-10_9-25-19.png
     
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  10. royrose

    royrose Senior Member

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    I've been "riding my brakes" down hills in the mountains of Colorado for 12+ years and 103,000 miles. my mechanic says I have 70% of my brake pads left. ride em cowboy!
     
  11. royrose

    royrose Senior Member

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    the five icons represent the last 5 braking episodes. Green means fully or near fully regenerative, red means mostly friction brakes, yellow is somewhere in between. more info:

    Hybrid Assistant
     
  12. jerrymildred

    jerrymildred Senior Member

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    Good answer, Roy. Thanks. (y)
     
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  13. FuelMiser

    FuelMiser Senior Member

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    What's wrong with B mode?
     
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  14. PtPri

    PtPri Junior Member

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    I may be wrong but, B mode is for steep downhills when you'll exceed max battery capacity.
    It will use more resistance from engine/gear braking, thus being less effective regen-wise, but better for HV battery temperature and longevity.
     
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  15. FuelMiser

    FuelMiser Senior Member

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    Yes, all that, but what's the problem? I didn't say use B mode for every slow down. I was replying to the guy who says he "rides" the brakes in the mountains of Colorado! B mode in those conditions will be better for the friction brakes. Once you reach max regeneration, you will only be using your friction brakes. "Riding" them down a long descent will overheat, or at least wear them more than need be. Of course, that poster says his brakes are fine after 100K+ miles, so who knows.
     
  16. james nancy

    james nancy Junior Member

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    The guy who said that 150,000 kilometers does not change brake pads is me. Please forgive me for not considering drivers who drive mainly in mountainous areas, where they may use more brake pads. Yes, if the battery is full, then it can only be used. The speed is reduced by the engine or brake pads.
     
  17. royrose

    royrose Senior Member

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    No need for it except in long downhill stretches when the battery gets fully charged. Nothing "wrong" with it but why do it before reaching full charge.
    Just like you didn't say that you always use B mode, I didn't say that I always ride the brakes. I suspect that we are both making intelligent decisions, just emphasized different thing in our comments.

    After all, we are both smart enough to live in Colorado ;)
     
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  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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    There's been several responses saying the friction brakes are rarely needed, that braking can be purely regen, and so on. It sounds good, but I don't think it's true. In fact it's almost invariably a mix, some regen, some friction braking, the proportions varying with circumstance. @chapman may be along with some graphics.
     
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  19. sam spade 2

    sam spade 2 Senior Member

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    Because the change over is automatic.

    Does "B mode" not use regen FIRST and then cut in engine braking after that ?
    And I believe that the friction brakes aren't involved at all until the driver pushes the pedal.

    Note: Having the cruise control set at a reasonable speed slightly below your desired speed accomplishes about the same thing.
     
  20. royrose

    royrose Senior Member

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    I'll take your second statement first. Yes, I believe friction brakes aren't used unless you put your foot on the pedal. Some roads are steep enough that the pedal is needed even in B mode.

    I'm not sure if B mode uses regen first, maybe a combination? I've tended to only use B mode (or the sort of equivalent S mode in our Rav4 hybrid) when the battery gets full. Then I can feel a vibration from the engine braking. S mode is good because you can choose the intensity of engine braking.

    Also, down a long enough hill even coasting will fill the battery. In that condition, the Rav then kicks in some engine braking automatically. My wife, who doesn't usually pay attention to such things, will say "the battery must be full". I don't remember the Prius doing that, haven't used it in the mountains lately.
     
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