How Much B-Mode Do You Use?

Discussion in 'Gen 3 Prius Main Forum' started by radiocycle, Jun 27, 2009.

  1. radiocycle

    radiocycle Active Member

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    How much, and how often, do you use B mode?

    Here on the central coast of California it's not what I'd call mountainous but there are some hills for sure. But I like to use B mode for slowing down even in the short run, as in slowing down from highway speeds coming off an off-ramp. I hear the rpm increase and I assume B mode is analogous to the L in old Chevy 'Powerslide' transmissions. So am I being hard on my 2010 by "shifting" into B Mode at 60 MPH?? I don't recall seeing anything in the manual about maximum speeds for using B Mode. Should B Mode only be used at say, 40 MPH when descending a long hill or something? Should I refrain from using it more than just occasionally? What say you?

    radio
     
  2. nineinchnail1024

    nineinchnail1024 New Member

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    I've never used it in either prius I've owned. Louisiana is pretty flat.
     
  3. john1701a

    john1701a Prius Guru

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    B will reduce MPG.

    You are transferring energy that would be captured by the generator to the engine.

    So unless the elevation change is a minimum of several hundred feet, you probably aren't going to use it.
    .
     
  4. Bruno_S

    Bruno_S New Member

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    When in B mode the battery is also recharged but braking will recharge it more. In an off-ramp situation it is better to brake gradually so it is done with the electric motor and most of the energy is sent to the battery. In B mode a lot of energy is wasted in heat and should be used on long downhills where you want to avoid brake wear and brake over heat.
     
  5. wvgasguy

    wvgasguy New Member

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    I am only familiar so far with the TCH but for the most part on a long grade as you're riding your brake (above 12 mph) I would think you're still using your regen "brakes" and not your hydraulic brakes, thus no brake wear is occuring. Once your battery hits full charge though would be when to begine using your "B" mode. I was always told that the B mode on the TCH did no regen, so either the Prius is a little different or I was told wrong. Either way it's not an effecient methof of transferring energy to the battery.

    I can't imagine ever needing it except in the mountains (and not the hills of WV)

    ( also since these coast so well downhill some people did use B mode on long slopes when they didn't want their brake lights to mislead traffic behind them)
     
  6. greylar

    greylar New Member

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    I posted this in another thread but I'll post it here as well. The only time B is actually useful is on long steep passes and it is obvious when you do. When the battery reaches full from breaking/coasting down hill there will be a moment when the car feels like it goes into neutral. That is when the computer decides that it isn't going to put any more juice into the battery. Which means that breaking is no longer regenerative and must use the break pads to slow the vehicle (or engine engine braking in B mode). In addition there is no regeneration from the simulated engine braking (thus the going into neutral feel). This takes significant time on a significant grade to achieve. Even here in Montana there is only one place that I have gone that I experience the phenomenon. So unless you just like wasting fuel there is no reason you should ever need "B".

    The more I think about it the more I wonder why Toyota didn't just dump the B mode and automatically go into B when the battery is full? Hmmm strange.

    G
     
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  7. Bruno_S

    Bruno_S New Member

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    If the hill is very long, it would be easier to set it to B instead of applying the brakes. I believe B is also a comfort feature.
     
  8. V8Cobrakid

    V8Cobrakid Green Handyman

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    you shouldn't be using it soooo much in a brands new 2010.

    i mean.. common.. the breakes are probably going to last way past 100k miles.. they really don't cost too much either.

    the only bad part is ( like people said i'm sure.. i'm just tired so i didn't read) you're wasting a lot of electricity.

    i'm a speeder.. so... i use it at odd times. i try to mainly use it on the really long 5 mile stretches down mountains where my battery would be green the first 1 mile and i'd be using constant brakes. It instead turns into B mode on all the time, very light braking to reduce speed.. and D mode for the last 1 mile to make sure i top off the battery before cruising through a stretch of city before the highway.

    if i'm cruising along with a decent charge, and someone pulls out in front of me ( no one in back of me) i'll use B for a second or so just to drop a few mph.

    btw.. i've shifted in and out of B mode with my Gen II while above 75mph with No ill effects... however.. you're still in break-in period ( like my first comment states) and you shouldn't be flooring it, or over reving it with B mode. Use the brakes more often...
     
  9. Midpack

    Midpack Member

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    I almost 3 years, never (on our TCH).
     
  10. patsparks

    patsparks An Aussie perspective

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    I only use it when I know my battery will be all green amd full at the bottom of the hill. I use it rather than braking as the car will dump excess energy anyway and switch to friction brakes as well.
     
  11. Prius_SGP

    Prius_SGP New Member

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    I only ever use it when going down log steep mountains, and a certain "hill" near me (it's a foot below the mountain mark). I mainly use it to help control my speed without having to use the brakes as much.
     
  12. TheForce

    TheForce Ron Paul 2012

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    Around here there are pot holes at every stop light stop sign and off ramp. I use B mode when my speed is below 20MPH to slow down in these pot hole areas. This helps prevent the traction control kicking in and killing regen when going over the bumps.
     
  13. wvgasguy

    wvgasguy New Member

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    But one of the the main advantages of this system is to capture energy. "Riding" the brakes can really boost the battery charge on a long grade without causing wear on your pads (until you're fully charged).
     
  14. DeanFL

    DeanFL 2010 owner - 1st Prius

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    I've noticed (while in the garage with the door down) that when I just begin to depress the brake pedal the brake lights do not come. It takes just a bit more travel, then switch on. At first I thought the switch at the brake pedal for the brake lights may need adjustment. Now I'm beginning to think it's designed that way in order to charge, not use the brake pads, while not alarming drivers behind that you're actually braking.

    I know this sounds convoluted - can someone shed light on this?
     
  15. wvgasguy

    wvgasguy New Member

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    I'm not sure about the settings on the Prius, but with the Camry (same design pysolophy) the hydraulic brakes would always be on under 12 mph. If you sere sitting still your brakes would be engaged. I'm not a technical expert but in laymans terms my understanding that what you are really seeing in regenerative braking is simpy a load slowing down your car from the generator charging the battery. It's not designed to stop you, but slowing the car to apply a torque against the generator will slow the car while charging the battery.

    Perhaps someone can give a technical explaination. I used to have a link back in 2007 when the TCH came out and I was curious about such things. Now I simply understand that it works so I don't worry too much about the technical side.

    However for new hybrid owners I'd look at the data links. One thread asked about the starter. Understanding the power splitting device is one of the basics of the system and you should look into that too.
     
  16. gofast

    gofast Member

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    Well, since you are from HELL you would not need to uses B mode becuae you are already at the botton and will not be climbing any hills in the near future and you should get better mileage right from the start because there is no warm up period.:eek:
     
  17. DeadPhish

    DeadPhish Senior Member

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    I've never used it at anytime in 120,000 miles. I'd probably only use it coming down out of the Appalachians at 70 mph.
     
  18. qbee42

    qbee42 My other car is a boat

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    In the OP's situation, don't use B mode at all. Use the brakes and regenerate the energy instead of wasting it as heat.

    Tom
     
  19. CAR4TWO

    CAR4TWO New Member

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    I'm with you Tom. I don't intend to use it at all. I did use it a couple of times just to see what it did. Once I learned that it was just down shifting to slow the car, I said to myself, "Well you can forget B." B stands for bad choice.
     
  20. royrose

    royrose Senior Member

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    I don't have my Prius yet. Am I understanding B mode correctly? B mode adds engine breaking? In B mode, if the battery is not fully charged, you get a combination of regenerative breaking and engine breaking? If battery in fully charged, you get just engine breaking? Or does B mode turn off regenerative breaking and always just give you engine breaking?

    Roy
     
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