HV Battery is never fully charged!

Discussion in 'Gen 3 Prius Technical Discussion' started by ePRIU$, Feb 10, 2019.

  1. ePRIU$

    ePRIU$ New Member

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    Please see my picture, my HV battery is never fully charged, it always one bar short. Is this normal? This is my first Prius, it's 2012 Prius 3 with 122000 mile low, thanks.
     

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  2. Lightning Racer

    Lightning Racer Active Member

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    Yes, it's normal if you drive in a relatively flat area. You typically need sustained downhills with regenerative charging happening to get full bars.
     
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  3. wjtracy

    wjtracy Senior Member

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    We see more often in cold winter when the heater is on, in summer only mountain downhills.
     
  4. George W

    George W Member

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    Does the Gen 3 allow for the stationary charging method, as the Gen 2 does? If so, maybe try to see if that would light up the last 5% SoC.
     
  5. Lightning Racer

    Lightning Racer Active Member

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    Yes, it does. No need to do it, but if ePRIU$ is curious, with shifter in drive, hold the brake down with your left foot, then press and hold down the gas pedal.
     
  6. rjparker

    rjparker Senior Member

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    You don’t want it absolutely full most of the time or your regenerative braking won’t work and you will wear your brakes out much faster. Plus if you were to force engine charging when driving on level ground or while stopped to max out the charge, you are spending extra money to do it. And having no regen capacity means lower mpg because you can not capture your kinetic energy when slowing or going downhill, which is the chief mpg advantage of a hybrid. There are all sorts of hypermiling techniques to maximize energy conservation including coasting instead of regen in some cases.

    Perhaps more interesting is the fact Toyota allows 40% of the battery kwh to be used and that 40% is what you see on the gauge. The rest is left unused to ensure 10 years or 150,000 or more miles on the 201 vdc battery. Compare that with your experience using 12v batteries in non-hybrid vehicles. To see it “fully” max out the gauge, try a mile downhill with two or more regen bars showing due to light braking.

    The hybrid logic does not know what elevations are coming on your route so can not further optimize the charge level. Maybe someday the daily driver for most people will be 300 mile EVs where maxed out charge due to regen is not an issue when they all have 100 kwh Tesla equivalent batteries instead of the 1.3 kwh units a standard Prius employs or the 4.4 kwh a Prius plugin uses.
     
    #6 rjparker, Feb 11, 2019
    Last edited: Feb 11, 2019
  7. Grit

    Grit Senior Member

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    Nimh battery life span are maximized when their discharge & charge are within 40 to 60% capacity. Cells will heat up causing physical expansion over time which can cause leaks when near full capacity. The Prius follows that 40 60 rule.
     
  8. Grit

    Grit Senior Member

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    Technically it’s 1 and half bar short. At 65%, that one bar short you say will show. But When your SoC beyond 75%, a half size bar will be shown. Anymore regen after that, you hatch should blow up like fireworks.
     
  9. rjparker

    rjparker Senior Member

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    It can show full on the gauge with a long downhill regen. Mine occasionally does just that. But then it will take no more and the car is not as efficient and the brakes wear faster.
     
  10. FuelMiser

    FuelMiser Active Member

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    Yes, completely normal. The Prius is NOT an EV. It is a hybrid, meaning both gas and electric are designed to combine to propel the car. As has been pointed out, you want to keep unfilled capacity in the traction battery to take advantage of regen braking. Fortunately, the computer knows this, and does a good job of managing it all on its own.
     
  11. ASRDogman

    ASRDogman Active Member

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    I have gotten all bars lit up a few times. Mostly when the battery is pretty much charged and am on a long slowdown,
    which then I use the "B", and then light pressure on the brake pedal to get the regen to charge.

    Where does it say this? I AM NOT COMPLAINING, challenging or anything, I am just curious. I didn't see it in the owners manual, nor did I expect too.
    I'm only wondering where this info is, and more about how the Prius controls how it charges the battery. Thanks.
     
  12. qdllc

    qdllc Senior Member

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    Yeah. It happens only under the right circumstances. Go down a long hill/stretch with the cruise control on, and not only will the battery max, but the car will engine brake since it can't recapture any more energy into the battery. If that never happens, I'd be concerned.
     
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