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Engine starts and stops quickly in rapid succession

Discussion in 'Gen 2 Prius Technical Discussion' started by sbunin, Jan 28, 2009.

  1. sbunin

    sbunin NYC Prius Driver

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    My engine was starting and stopping multiple times in rapid succession. I had just started the car (it was cold) and gone done a long hill that recharged the car. When I checked, the battery indicated full charge (all lines green). I figured the car was starting to warm the engine but kept stopping because the battery was fully charged. To stop this I started the A/C and let the car warm up. Once the A/C was on, the battery lost 1 green bar fairly quickly and the engine stayed off. All this was within 2-3 minutes of starting the car. Has anyone else experienced something similar?

    Let me also add that this is my second post but I have been reading priuschat for about 3 years (Got my Prius Dec 2007). Thank you to everyone who posted before me, great information.
     
    #1 sbunin, Jan 28, 2009
  2. john1701a

    john1701a Prius Guru

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    That's normal (though rare for those of us in flat country)... and the engine isn't actually starting.

    The motor is repeatedly spinning up of the engine to consume the excess electricity just put into the battery for longevity protection.
    .
     
    #2 john1701a, Jan 28, 2009
  3. finman

    finman Senior Member

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    Yes, that's normal for a Prius with a full green battery.

    After a long downhill and full recharge from regen braking the computer will spin one of the electric motors (the one that normally spins to start the gas engine...i can never remember if it's MG1 or MG2...), and this in turn spins the gas engine with little to no fuel and no spark...just so the battery comes down to a normal charge level.

    A bit disconcerting when it happens, but completely what the car is designed to do: extend the battery life, protect the battery from too much charge or too little. A true "smart" car!
     
    #3 finman, Jan 28, 2009
  4. patsparks

    patsparks An Aussie perspective

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    What they said.
     
    #4 patsparks, Jan 28, 2009
  5. qbee42

    qbee42 My other car is a boat

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    To further clarify (which means to add more technical information than you want :)), the Prius works aggressively to manage the battery charge. It is not happy with all green bars as it leaves little room for regenerative braking. In this case, the controller spins the engine with MG1 just to burn off excess charge. In other words, it throws away some energy to bring the charge back down to an acceptable level.

    If you hadn't stopped, the Prius would have worked off the excess charge by using the electric motors more and the engine less. Being at a standstill, it was left with no option but to throw away energy.

    Tom
     
    #5 qbee42, Jan 29, 2009
  6. sbunin

    sbunin NYC Prius Driver

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    Thanks for the feedback. Good to hear someone else say it is normal but disconcerting.
     
    #6 sbunin, Jan 29, 2009
  7. Genoz World

    Genoz World ZEN-style living

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    that happens....but normal
     
    #7 Genoz World, Jan 30, 2009
  8. tochatihu

    tochatihu Senior Member

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    If you are at a standstill and can't bear this (rare) behavior you may shift into 'N'. HV battery management really ought to be done Toyota's way in general, but if you can't bear it...
     
    #8 tochatihu, Jan 30, 2009
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