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Won't coast on battery

Discussion in 'Gen 3 Prius Technical Discussion' started by Toddwilks, Sep 1, 2014.

  1. Toddwilks

    Toddwilks Active Member

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    Hello all,

    I just picked up a 10 prius III on Friday. I had an 09 prius prior to this one. I noticed that this car, will not coast unless I have my foot in it so that the ICE is running. It does this on level ground and even on the highway. It usually happens when I am in the 30-40 mph range I notice it the most. My 09 did not have this problem. It would coast all day long. Here is what I checked:

    Running in D not B
    Eco has been turned off

    I also noticed that it happened sometimes going down a slight hill. If I take my foot off the gas, it will slow down unless I push the pedal down enough to turn ICE back on. Is this normal? I'm only getting 44mpg combined whereas on my 09 I got 52-53 on the same trips.
     
  2. Former Member 68813

    Former Member 68813 Senior Member

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    Abnormal, are are driving with parking brake on? If not that, check brakes for sticking. If not that I don't know what but could be expensive to fix.
     
  3. jdcollins5

    jdcollins5 Senior Member

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    To coast, take your foot off the accelerator and while watching the HSI screen slowly feather the pedal until there is no regen or EV bars showing. For less than 46 mph, you can either coast or keep the bar to the left of the center line to keep ICE off and running on EV.

    The slight regen is to simulate engine drag of an ICE only vehicle.
     
  4. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Sounds defective to me too. Mine will float along on battery under 40 mph on many occasions. Trust your tyres are the correct type and up to correct pressures as drag could slow your car down. Is your alignment ok? Is the 12v ok? Has it been sitting on a dealers lot for months and run flat causing it to fail? That would/could cause the car to continuously try and charge it up using the HV battery charge and thus not allowing it to move the car forward. Are you hammering the a/c?

    You've not said what your miles are? Is the car a high mileage abused example?
     
  5. bisco

    bisco cookie crumbler

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    coasting is much more difficult in gen III, as the software does much of the work for you. as stated above, you have to really feather the pedal around the regen line. a scan gauge might help, but you'll get better mpg's than the gen II without as much p&g.
     
  6. Toddwilks

    Toddwilks Active Member

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    It has 59,000 miles on it and running Yokohama Avid S33 which I found out are not LRR tires. Alignment seems ok from what I can tell. The wheel is off center to keep the car straight but it doesn't pull one way or another. I'm not running the AC at all. How do I test the 12v in the gen III? The car was sitting on the lot for about a month. I picked it up with 1 mile more than they took it in with so I guess nobody rest drove it. Its also a CPO car.
     
  7. Toddwilks

    Toddwilks Active Member

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    Just checked again and they are 833D tires.

    Also everytime I get in the car, it only has 3 bars on the battery. Regardless of how charged it is when I get home. I leave nothing on and I make sure every night.
     
  8. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Easy check of the 12v if you don't have a multimeter is to leave the car over night and in the morning (when you don't need the car) is to put the car in Acc mode (NOT into Ready as that will start to charge the 12v) and then wind all 4 windows down at once and then back up again. If they're quick as normal then your 12v is fine, if they go painfully slowly and the interior lights go dull or out, then the 12v is your issue. To compare, put the car into Ready mode afterwards and try it again. If they whizz up and down nicely this time but slowly slowly before, then it's the 12v. Normally they last about 5 years or 70/80k miles, and sometimes more if looked after. But it's a small battery and doesn't need much to kill it such as been run totally flat on a dealers lot and left like that.

    They're not that expensive here in the UK at about £90 fitted. I understand they're about $300 in the US which sounds expensive.

    Don't worry too much about your HV battery being at different charge after being parked. It's temperature dependent (holds much more when warm compared to cold etc) and the car will tell you if it's not happy. You're also under warranty in the US so even if it is knackered, it's not a problem.
     
    gdanner likes this.
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe a borderline battery, and the regen's coming on excessively in an attempt to charge more, hence the poor coasting? How many miles on it?

    (That said, GrumpyCabbie's response sounds a lot more upbeat, I'd go with his guidance.)
     
  10. bisco

    bisco cookie crumbler

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    59,000. hopefully your hybrid battery is okay. i would take it in and have them look at it, everything is under warranty. all the best!(y)
     
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  11. David Beale

    David Beale Senior Member

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    BOTH the GII and GIII will regen a bit to simulate engine braking when you release the throttle pedal. The GIII, with tighter coupling, will give a bit more engine braking. It will also do it down to a lower speed. Use of "B" (which you already posted you were not) adds -real- engine braking.

    I don't see anything wrong here, but if you are still suspicious, use your hand to check wheel temps after you drive a mile or two with minimal use of the brakes. If any wheel is warmer than the others, you may have dragging brakes on that wheel. Keep in mind, if one side of the car was in the sun those two wheels -should- be warmer than the other two.

    Also, keep in mind the GIII uses the traction battery quite a bit more than the GII. Because of this, you can begin to wonder if anything is wrong when switching from a GII to a GIII. You will see different charge levels than you are used to, and the car will switch to EV mode more often and for longer periods, no matter what mode you have selected.

    One reason the GIII gets slightly better mileage than the GII, and perhaps one reason the traction battery may not last as long, though that is still being hotly debated.
     
  12. Toddwilks

    Toddwilks Active Member

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    Thank you for all of the responses. It's going to take a bit to learn these cars.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    Try touching the gas pedal, just enough to dispel the regen?
     
  14. Toddwilks

    Toddwilks Active Member

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    Nope. It has to be 3/4 of the HIS to maintain speed
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Assuming you've got a good feel for how it should typically coast, from your gen 2 experience, something's gotta be dragging then. I know, brilliant observation.

    Brakes? Jack up the rear with parking brake released (chock the front) and see how the rears are turning.
     
  16. bisco

    bisco cookie crumbler

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    this is your problem, pulse and glide is not about maintaining speed. it's about using the ice to accelerate to speed (your choice) then gliding to minimum (your choice), then pulsing again.
     
    #16 bisco, Sep 2, 2014
    Last edited: Sep 4, 2014
  17. GregP507

    GregP507 Senior Member

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    Based on my understanding of the gen III power-train, I don't think coasting in neutral is a good idea. The drive wheels are connected to the gas engine and motor-generator at all times through a planetary power-differential. There is no clutch. For the car to seem to coast in neutral, one or both of the motors must be running to compensate for forward motion. In other words, you're using energy, instead of capturing it from regeneration.
     
  18. Toddwilks

    Toddwilks Active Member

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    I'm not coasting in N. I'm talking about being able to basically just maintain any speed. The only way I can on the highway is by having the HSI close to full or in PWR. I just dropped it off at the dealer so let's see what they say. I'm fairly confident something is wrong because I drove the 09 today too and it seems like that car can coast for days and it seems so much faster ( I use that word loosely). I would expect otherwise.
     
  19. bisco

    bisco cookie crumbler

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    maybe a bad 12v and ice is trying to recharge. please keep us posted, all the best!(y)
     
  20. GregP507

    GregP507 Senior Member

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    That's possible, but an aux battery in such bad shape probably wouldn't start the car.