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Weird ICE start-stop at bottom of hill

Discussion in 'Gen 2 Prius Main Forum' started by kinghuang, Jul 4, 2005.

  1. kinghuang

    kinghuang Member

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    I've noticed a really strange behaviour at the bottom of one particular hill on my normal route to the airport. There's a stop light at the bottom where two major roads connect. Whenever I drive down this hill and stop at the stop light, the Prius ICE will repeatedly cycle on and off extremely quickly and continuously. IE: It'll start and stop within a second, over and over again. The first time it happened, I didn't think much of it and just let it do its thing. But, I've noticed this three separate times now, and it just doesn't seem right. Because it's after a long downward slope, the battery is usually near full (first or second green bar). I've made sure that my foot is firmly on the break, so I don't think that's it. Yesterday, when I did the same drive, I tried shifting to neutral after I stopped, which stopped the ICE from repeatedly starting and stopping. Has anyone ever heard of this behaviour? It only happens at this intersection.

    Here's a Google map of the area for anyone that's interested. It always happens when I'm traveling eastbound on Country Hills Blvd., stopped just before Shanganappi Tr.
     
    #1 kinghuang, Jul 4, 2005
  2. galaxee

    galaxee mostly benevolent

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    When you go downhill you're charging the battery. Remember the Pri doesn't like overcharge on its HV battery. So when it gets full it'll kick on the ICE to drain off excess energy. Sounds like that's what's going on.

    I believe in N the car won't charge the battery so that would keep the issue from happening.
     
    #2 galaxee, Jul 4, 2005
  3. kinghuang

    kinghuang Member

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    <div class='quotetop'>QUOTE(galaxee\";p=\"103983)</div>
    I think the effect I'm getting at the bottom of this particular hill is different. I have experienced the ICE spinning freely when going down really long hills after the battery is "full". However, what happens at the bottom of this particular hill is that after I stop for a few seconds at the stop light, the ICE will start up (on gas) and then go off in the space of a second, and do this repeatedly. Since the battery is practically full, it shouldn't be spinning up to charge it. And, it's warmed up outside now, so I don't think it's because the engine is cold. Are there any general situations where the Prius ICE is supposed to come on and off repeatedly like this?
     
    #3 kinghuang, Jul 4, 2005
  4. DanMan32

    DanMan32 Senior Member

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    It isn't spinning up to charge it, rather it is running MG1 (powered) to drain the battery a bit, but not accept any current once ICE starts up. It then shuts down ICE, then uses power to start it up again. It is like cranking a malfuntioning engine until it goes dead, but in this case, ICE is actually started. The fact that you hear ICE spinning near the bottom of the hill confirms that the battery is full, and thus HV goes to 'bleed off' mode at the stop at the bottom of the hill.
    I know, sounds dumb to me, but that's what we speculate is happening. Since the function of N is to totally disconnect drivetrain, really what it does is disable MG1/MG2 control, both to prevent powering them, or prevent receiving power from them, thus ICE cannot be started.
     
    #4 DanMan32, Jul 5, 2005
  5. Marlin

    Marlin New Member

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    <div class='quotetop'>QUOTE(DanMan32\";p=\"104150)</div>
    I wonder why it wouldn't just spin the ICE with MG1 without starting it? All it would have to do is deny the ICE gas and spark. Perhaps it wasn't designed to shut off all gas to the ICE and therefore must start it to keep from flooding the ICE?
     
    #5 Marlin, Jul 5, 2005
  6. kinghuang

    kinghuang Member

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    I suppose that's reasonable enough. It does seem like a strange way to drain off the battery.

    Putting it into neutral for a minute shouldn't break anything, right? After all, I'll be going up a bit of an incline again after the light goes green. So, it would make more sense to drain the battery on that than on a dead stop.
     
    #6 kinghuang, Jul 5, 2005
  7. robinredbreast

    robinredbreast New Member

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    I have had the excact thing happen to mine ICE on off on off on off until I shut it down I was coming down my long steep driveway and had to stop half way down because my cat would not move out of the way. Its not letting off a charge . I had blue bars
     
    #7 robinredbreast, Jul 6, 2005
  8. love2drivefaster

    love2drivefaster Junior Member

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    Has anyone figured this issue out yet? I had this happen to me for the first time today. Similar situation. The HV battery is 1 bar from full. Im at a slight incline while parked. Weather is probably in the mid to low 60s. Car isnt really warmed up yet.
     
    #8 love2drivefaster, Nov 15, 2018
  9. Skibob

    Skibob Senior Member

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    If he did I don’t think he will tell. The OP has not logged on here in over 2 1/2 years.
     
    #9 Skibob, Nov 15, 2018
  10. bisco

    bisco cookie crumbler

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    a fully charged battery requires the engine to start to burn off any excess incoming charge. as the weather gets colder, the battery accepts less charge, and the engine comes on sooner
     
    #10 bisco, Nov 15, 2018
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