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(B) braking.

Discussion in 'Gen 3 Prius Technical Discussion' started by Caug1, Jun 12, 2011.

  1. qbee42

    qbee42 My other car is a boat

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    You use it on long, steep downhills to save wear on the friction brakes. The traction battery in the Prius has a finite capacity, which is rapidly exceeded during downhill braking. After it fills up, your Prius is forced to switch to friction braking. B mode forestalls the switch to friction brakes.

    Tom
     
  2. qbee42

    qbee42 My other car is a boat

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    Standard braking is still more efficient, so his statement is not gibberish. In the mountains you have an excess of potential energy, so regeneration efficiency is moot.

    Tom
     
  3. Caug1

    Caug1 Member

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    I see. I got it now.
    but what happens when battery displays only 2,3,5 bars full,. would it switch to friction brakes until it will be full, being all green battery?
    so until then friction brakes will not kick in, right?
    i never seen full battery, the max for me one less bar.
     
  4. qbee42

    qbee42 My other car is a boat

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    In a nutshell, your Prius will continue to use regenerative braking until a bit past full green bars. At that point it will switch to engine braking, just like B mode, and friction braking if necessary.

    The fact that you have never experience full green bars means that you have never needed B mode. Living where you do, it's unlikely that you will ever have a need for B mode, unless you go on a road trip.

    Tom
     
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  5. Caug1

    Caug1 Member

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    Qbee 42,
    you are the best.
    Thanks,
    Caug
     
  6. ksstathead

    ksstathead Active Member

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    I am not aware of anywhere in my state that B mode is needed, either. But I sure find some on trips to mountains.
     
  7. bnaccs

    bnaccs bnaccs

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    When th ebattery is fully charged when braking lets say down a steep mountain pass will the indicator not show the charge bar when the friction brakes are being used?
     
  8. macman408

    macman408 Electron Guidance Counselor

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    At least when coasting, I believe it will be smaller, though not gone - but in that case, it's not using the friction brakes, it's spinning the engine really fast. If you're coasting in B down a hill at moderate speeds or faster (say 35 mph+), you'll notice when the battery fills, because the engine will go from maybe 1500-2000 RPMs to 3000-4000 RPMs (aka much noisier). I don't recall for sure, but I think the bar still shows up when you apply the brakes.