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What happens if you drive in "B"

Discussion in 'Gen 2 Prius Main Forum' started by Tickwood, Dec 29, 2004.

  1. Tickwood

    Tickwood Active Member

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    Lets say you shift into "B" to go down a steep road on a small mountain and then forget to shift back to "D". What happens? I assume you gas mileage would drop, but are there more serious effects?
    thanks
     
  2. V8Cobrakid

    V8Cobrakid Green Handyman

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    engine just stays running which will put a drain on the battery since at low speeds it will start to run because of your fake idle.. so the electric motor will keep spinning it when you are stopped.. it feels like a badly times engine at that point.. you can feel it shake.
     
  3. efusco

    efusco Moderator Emeritus
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    I don't think it affects anything when you actually have your foot on the pedal applying power...I 'think' it cuts out the regen braking. But the second you let off you notice dramatically more drag than usual and the ICE doesn't shut down completely.

    I've accidently left it in B a few times and noticed something was wrong right away, and figured out what within a block.
     
  4. hdrygas

    hdrygas New Member

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    As far as I can tell if you drive in B other than steep down hill you my trash your battery, as you will not recharge. The battery does not do well if over charged or undercharged. The NiMH battery does best if kept in a narrow range of charge. Let the computer do its work. Just drive it. B is for steep down hills when you need engine braking. I have been on a few steep long down hills living close to a few mountain ranges. It is useful when you might need to be using the brakes for a long period, but if you are between the break and the accelerator you should be in D. B is for those hills where you need to down shift to keep in the speed limit on a down hill.
     
  5. DanMan32

    DanMan32 Senior Member

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    B won't discharge your battery, though it may fluctuate a little more. Main purpose of B, as stated, was to increase drag with ICE. For deceleration, that mostly means turning ICE with no fuel or spark. However, as Evan may be noting, ICE doesn't shut down at lights as quickly.

    Best to not use B unless you need to have extended deceleration, such as a steep downgrade, and need to avoid using hydraulic brakes.
     
  6. efusco

    efusco Moderator Emeritus
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    Just an FYI. I use B mode fairly often, but only BELOW 20mph....the ICE won't kick in but it will increase regenerative braking beyond what you'd get with just coasting. Nice way to be sure you're not losing anything through the friction brakes.
     
  7. Frank Hudon

    Frank Hudon Senior Member

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    it's the 60-80% rule you have to remember using B if the battery is under 80% it regens if over 80% it uses the battery to power the mg2 in "plugging" mode. Ie it powers the MG2 to force it to try and run backwards which then gives you the deceleration/drag on hills. If PC ever gets going again do a search on "results from the miniscanner" and read what happens on a 5 mile 10% grade.
     
  8. bruceha_2000

    bruceha_2000 Senior Member

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    I forgot to change from B to D Sunday night coming home from my in-laws after getting off the hill. I noticed nothing different when driving several miles including stops. The thing that DID clue me in, FINALLY, was that the CC wouldn't work.

    I had gotten to the 50 MPH road and set it but the car kept slowing down when I took my foot off the gas. I was starting to fret about needing a repair when I remembered I left it in B and I know the CC doesn't work in B. Went to D; all better! :oops: