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Confusion over "B" mode and when it should be used

Discussion in 'Gen 2 Prius Technical Discussion' started by lagreca, Jul 21, 2007.

  1. lagreca

    lagreca Junior Member

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    I am a new Prius owner, and am confused over when to ride the brakes, and when to use B mode.

    I've read that the brake pedal does not activate the physical brakes when gently pushed, but make the motors generate more power for the batteries. I thought physical brakes only come on in emergency stops, and under 7 mph.

    So on a long downhill, and any downhill for that matter, I thought it was a good idea to gently ride the brakes, instead of using B to help generate more power.

    However, where t hisgets tricky, is when the battery is full. The generators don't have anywhere to store the power, so I figured the next step to slow the car down, would be for the computer to turn the engine into a brake, using compression (similar to B mode). With physical brakes being used as a last resort. Is this correct? Or does the computer go from regen to physical brakes?
     
    #1 lagreca, Jul 21, 2007
  2. tochatihu

    tochatihu Senior Member

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    No replies yet to one of the all-time favorite Prius questions? Must be the middle of the night in Prius-land.

    It's late afternoon here in southern China and I just got an internet connection turned on, so I'll give it a shot. If you are on a long steep downhill and riding the brakes, pop it into 'B' When you get to the bottom (or are slowing too much) pop it back into 'D'. Under those circumstances, you are not losing much regeneration potential. If your big battery is full*, you are not losing any.

    *Full has a unique meaning for the Prius HV battery. But not one that needs discussion here. Just follow what your instincts appear to be telling you.
     
    #2 tochatihu, Jul 21, 2007
  3. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    #3 FL_Prius_Driver, Jul 21, 2007
  4. ken1784

    ken1784 SuperMID designer

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    #4 ken1784, Jul 21, 2007
  5. richard schumacher

    richard schumacher shortbus driver

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    Ditto that: just like in any car, don't ride the brakes. When you find yourself riding the brakes, that's when you shift to "B". When you are no longer riding the brakes shift back to "D" (otherwise fuel economy will suffer).

    Don't worry about managing regen and all that. The computers are always trying to do the right thing. The only reason that "B" exists is that the car cannot know how long is the downgrade in front of it, whereas presumably the driver can.
     
    #5 richard schumacher, Jul 22, 2007
  6. MarinJohn

    MarinJohn Senior Member

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    <div class='quotetop'>QUOTE(ken1784 @ Jul 21 2007, 09:59 AM) [snapback]482834[/snapback]</div>
    Excellent Ken-san, thanks!
     
    #6 MarinJohn, Jul 22, 2007
  7. FireEngineer

    FireEngineer Active Member

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    That write-up is actually from Hobbit here.

    Wayne
     
    #7 FireEngineer, Jul 23, 2007
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