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ICE turning on and off

Discussion in 'Gen 2 Prius Technical Discussion' started by nosliw, Mar 29, 2008.

  1. nosliw

    nosliw New Member

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    Last night my car did a very funny thing.

    I had just gone down a long slope, so the battery was fully charged, and my foot was on the brake at a redlight.

    I noticed the engine start and then shut off a few seconds later. I could feel it start and stop every 2 or 3 seconds. I can't remember what the MFD said. It continued doing this for a minute until the light turned green.

    My foot was firmly on the brake, and it hasn't done it since.

    Anyone else experience this?
     
    #1 nosliw, Mar 29, 2008
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    This has never happened to my since my battery is almost never fully charged, but I remember some people talking about that here. Apparently, the ICE will run and burn off some of the extra charge. I can't explain it but I'm sure someone will chime in and be able to explain it.
     
    #2 TonyPSchaefer, Mar 29, 2008
  3. patsparks

    patsparks An Aussie perspective

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    The electric motor will spin the ICE (internal combustion engine) to dump excess energy if the battery is over 80% charged. If the battery is at full charge regularly at the bottom of a hill this is the only time I would recommend using B mode to slow the car on the hill. Basically this manually dumps some of the energy before it gets to the battery.
    This isn't compulsory, the Prius can look after itself.
     
    #3 patsparks, Mar 29, 2008
  4. qbee42

    qbee42 My other car is a boat

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    In case it wasn't obvious from the previous post, the engine isn't running when it does that, it is just being spun by MG1 to throw away excess charge. The motor spins the engine for a few seconds, then checks the battery. If it is still too high, it spins the engine some more. The cycle continues until the charge is down the the proper level.

    Tom
     
    #4 qbee42, Mar 30, 2008
  5. MPGsnob

    MPGsnob New Member

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    Is it ideal to have the battery green?
     
    #5 MPGsnob, Mar 30, 2008
  6. nosliw

    nosliw New Member

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    Interesting. Thanks for the replies.
     
    #6 nosliw, Mar 30, 2008
  7. efusco

    efusco Moderator Emeritus
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    No, it is ideal to have 6 blue bars...or about 60% SOC...that's what the car is programmed to shoot for to maximize battery life.
     
    #7 efusco, Mar 30, 2008
  8. nosliw

    nosliw New Member

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    What's wrong with letting the battery charge all the way up (like down that hill) and utilizing the battery more for a while to drain it back down?

    Doesn't that not waste the *free* energy from going downhill into something I can use for transport later?

    I noticed the ICE didn't kick back on to propel me until I hit about 25MPH after that (it was only very slightly downhill after the stoplight. I used up most the battery on the stop-and-go traffic before I got home.
     
    #8 nosliw, Mar 30, 2008
  9. pewd

    pewd Clarinet Dude

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    for all the car knows, you're fixin' to go down another hill ; the computer is trying to protect the battery from an overcharged situation.
    the computer cant see whats ahead, so it makes assumptions that fit the majority of situations.
     
    #9 pewd, Mar 30, 2008
  10. nosliw

    nosliw New Member

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    It didn't burn off much (not a bar) when it was churning the engine those few times. And on the way home I hardly used the ICE. Great mileage.

    In THIS situation do you think it would be best to just let 'er charge?

    If I use 'B' and understand it correctly, I'm just wasting that potential power.

    Or maybe I'll approach the hill slower and glide down the whole thing.

    Or maybe I should drive the thing like any other car and let it do its own thing.
     
    #10 nosliw, Mar 30, 2008
  11. richard schumacher

    richard schumacher shortbus driver

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    If the cabin heater was on then the engine was running to supply heat.

    The only reason to use B is to avoid riding the brakes on a loooonnng downgrade. Any other time it pointlessly reduces fuel economy.
     
    #11 richard schumacher, Mar 30, 2008
  12. efusco

    efusco Moderator Emeritus
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    It won't burn off 'much'. But it'll burn off a few percentage of the state of charge. As stated above, when the SOC goes above 80% the car will do all it can to get you back below that...it's too small a difference for you to see on the rough Energy Screen Battery display.

    yes. And in future generations we may well have GPS integrated into the programming of the HV ECU and the car will know that you're planning on going up a hill next and leave that higher charge there for you to use. But, as stated above, the car has no idea if you're going to go up hill, level or down hill and keeping the SOC above 80% will, potentially, shorten battery life just as being below 40% can.

    Probably...if the hill is very long and you're going to max out the battery SOC (80%+) either way then B-mode is fine. Most of us just don't bother as more often than not you're burning gas unnecessarily with the ICE running as it does in B-mode.

    NOW you're talking!!:hail:
     
    #12 efusco, Mar 30, 2008
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