Full charge engine goes on and off

Discussion in 'Gen 2 Prius Main Forum' started by danl, Jan 21, 2010.

  1. danl

    danl New Member

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    Solved - Full charge engine goes on and off

    I think this topic has come up before and I do recall reading that it was normal behaviour. But now that its been happening to me I'd just like to ask and make sure a trip to the dealer is (hopefully) not necessary.

    So on my morning daily commute to work, I glide down this long and moderately steep section of Rt2, at the bottom of which is a stop light. On 4/5 days, at the bottom of the hill, I'm at a full charge on the battery, 10 bars full green. Sometimes, when in that scenario, I notice the engine kicks on for a second, then off for a second, then on, then off, repeatedly until the light changes and I start moving again.

    My guess is that the battery is over charged and the car is trying to dump excess energy, but any insight/confirmation is appreciated. And if the car needs to dump the energy, why not just keep the engine on. Why go on and off and on and off?

    Ty
    -Dan
     
  2. qbee42

    qbee42 My other car is a boat

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    You are correct. The control system is bringing down the battery SOC by spinning the ICE as a load. Doing it in bursts allows for more accurate monitoring of the SOC, as the battery is not under heavy load between bursts.

    Tom
     
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  3. danl

    danl New Member

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    Thanks Tom. That works for me. I wish it wouldn't do that at the stop light though. Sometimes during the summer, people pull up besides me with their windows down and give me a questioning look as if saying "whats wrong with your hybrid?"
     
  4. ksstathead

    ksstathead Active Member

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    If you can EV (not necessarily EV mode) to reduce SOC before the descent, then it might not get full enough to compel the waste. Or you can use B on the descent to reduce regen, but better to use the EV before the crest and stay in D.
     
  5. Bobsprius

    Bobsprius BobPrius

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    "whats wrong with your hybrid?" Anyone giving you that look, say "nothing at all, my car is cycling using less gas while your's is running CONTINUOUSLY wasting gas!" ;)
     
  6. john1701a

    john1701a Prius Guru

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    Re: Solved - Full charge engine goes on and off

    That assessment of dumping is correct; however, the engine isn't going on and off. The motor just spins it to consume electricity (for the sake of battery longevity). So, what you are feeling is just RPM changes. It never actually starts.
    .
     
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  7. bagwell

    bagwell Active Member

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    Re: Solved - Full charge engine goes on and off

    very cool...!
     
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