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Reduced Regen Braking Force

Discussion in 'Gen 3 Prius Technical Discussion' started by peirhead, Oct 6, 2010.

  1. peirhead

    peirhead Junior Member

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    I have noticed recently that I seem to be getting less regen braking force than I used to. Particularly noticeable at highter speeds at over 45MPH or 70 KMPH. The regen seems to have very little effect now until I have slowed down. I seem to have to use much more brake than I remember recently. And by the way the battery in not nearly fully charged....Regen does come on but seems to have very little slowing power....anyone else noticed this?
     
  2. fuzzy1

    fuzzy1 Senior Member

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    Roughly speaking, maximum regen braking force is inversely related to speed. The faster the car moving, the smaller the braking force needed to reach the maximum permitted battery recharge rate.

    Put another way, regen is limited by battery power. Power = Force * Speed.

    Could this be confusing the matter?
     
  3. qbee42

    qbee42 My other car is a boat

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    How can you tell? Do you have instrumentation, or is this a seat-of-the-pants thing?

    Tom
     
  4. peirhead

    peirhead Junior Member

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    This is strictly seat of the pants analysis! I understand the regen concept and Fuzzy1's reminder is well noted...It just seems that in the last couple of days I'm not getting as much regen at faster speeds. I can tell when I am bearing down on the brakes past the regen and into caliper mode...and am quite sure I wasn't doing it nearly as much a few days ago.
     
  5. spiderman

    spiderman wretched

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    Quantitatively can you see a difference in the charge section of the HSI?
     
  6. peirhead

    peirhead Junior Member

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    The HSI shows full regen almost as soon as I touch the brakes...yet I feel very little "drag" from the regen till I am down around 30 MPH
     
  7. adrianblack

    adrianblack Member

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    At 60mph it's very hard to feel full regen... as Fuzzy1 pointed out as speed goes up it takes much less slowing to reach maximum regen (battery charging.)

    There would be no way to tell what is going on with your car unless you have a Scangauge -- with that you can see exactly how many amps are going into the battery and how much friction brake is being used.

    What you are feeling is correct -- regen only really takes the place of the brakes below 30mph. In fact, it's around 15-10mph where regen really can slow the car.

    I commute mostly at 35mph or below and typically my brakes are barely used. When I get home the rotors are still cold to the touch. But I purposefully brake slowly to maximize regen.... At 35mph as soon as I start slowing regen is full on the HSI. I fill up the bar and then back off slightly to keep it just under max regen. Keep applying more force to the pedal as you slow down to ramp up regen.
     
  8. Flaninacupboard

    Flaninacupboard Senior Member

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    Has it got much colder in the last week? the battery can accept less regen when it's very cold (don't know the specifics of thresholds or amperage)
     
  9. GrumpyCabbie

    GrumpyCabbie Senior Member

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    I personally think the regen isn't as good as it was PRIOR to the recall software update back in February time.
     
  10. austingreen

    austingreen Senior Member

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    Has your fuel economy suffered?
     
  11. GrumpyCabbie

    GrumpyCabbie Senior Member

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    No, it's actually better :D but brake wear is worse.
     
  12. David Beale

    David Beale Senior Member

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    Full regen requires the ability to -fully use- the battery. You will not be allowed to do that if:
    1. The charge level is too high.
    2. The battery temperature is too high (I don't think it's limited by low temps as the battery will heat up during charging anyway).

    If the car is sitting in the sun on a hot day the battery -may- be warm. At the very least it will be warmer than on a cool day and therefore will warm up in less time. I say all this because the OP first posted in June, as the weather was warming in the maritimes.
     
  13. adrianblack

    adrianblack Member

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    I haven't had the recall done ..... so when I do, I will be able to see empirical differences on my ScanGauge II.
     
  14. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Maybe the regen is unchanged but the friction pads are used more than they were resulting in increased wear? I'm sure I noticed more black dust on the wheels ever since the update.