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Hot battery?

Discussion in 'Gen 2 Prius Main Forum' started by Karkus, May 23, 2005.

  1. Karkus

    Karkus Junior Member

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    Location:
    Boulder, CO
    Vehicle:
    2019 Prius Prime
    Model:
    Prime Advanced
    This weekend we did a short trip into the Colorado mountains while it was quite hot (90F) and I experienced some unusual acceleration behavior.
    We climbed 2300 ft (7% grade) in the morning and everything seemed fine, then descended 700 ft. The Prius was left parked in the sun for a couple of hours.
    Then we returned the same way. On the curvy 700 ft climb with up to 10 % grade, there was a lag in acceleration whenever I hit the gas, and the car did not seem to want to use the battery much at all. When I reached the top of the steep hill, the battery was at 6 bars (I would expect about 2 bars under normal conditions at the top of such a hill). I could also hear a fan noise where the battery intake vent is. On the 2300 ft descent, the battery only charged up to 7 bars (I would expect eight) Note: I did not use AC.
    After leaving the car parked for a while in the shade, the battery behavior was back to normal.
    It seems that the Prius was trying to protect the HV battery from overheating by not using it much, which caused the lag in acceleration. Does that seem right? This may also explain why my gas mileage for this round trip was only 40 MPG (I filled up just before going up), whereas normal mountain driving gets me 45-50 MPG. The interesting thing is that I have owned this car for a year and a half and have done hot summer mountain driving many times without this problem (but such heat combined with an immediate very steep climb is unusual).
    Any comments?
     
    #1 Karkus, May 23, 2005
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Yes, the Prius is trying to keep the battery from overheating hence the fan that you heard was going off trying to cool the battery. That's another good reason to keep the A/C on. In the winter, the car will try to heat up the cabin as fast as possible to warm up the battery to keep it in its optimal operating temperature
     
    #2 Tideland Prius, May 23, 2005
  3. gschoen

    gschoen Member

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    Vehicle:
    2014 Prius Plug-in
    Model:
    Plug-in Base
    You'll not only keep the battery cooler but keeping the windows up and using A/C gives better mileage at a lower speed than regular car (does anyone know the approx. speed? ) If I'm sustaining speeds abouve 40MPH, or even a short time above 45MPH, I put the windows up just because its so noisy, the popping noise hurts my ears. I figure that's Prius telling me to put the windows up for better MPG! :wink:

    For best mileage just set your A/C to comfortable but not blasting temp. You and your batteries should be happy!

    (I love any excuse to get to use A/C - "I have to run the A/C - not for me, for the car!"
     
    #3 gschoen, May 23, 2005
  4. DanMan32

    DanMan32 Senior Member

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    I seem to get better mileage not using AC and having windows down, especially if the AC has to work hard. But if the AC has to work hard, I can't put up with the heat that I would have to deal with in having the AC off and windows down.

    Can't prove it empirically though.
     
    #4 DanMan32, May 23, 2005
  5. gschoen

    gschoen Member

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    Dan, do you find that just for lower speed cruising or both high and low? Does Wayne's MPG simulator let you test for windows up/down? I've always wondered what the speed is where aero drag is higher than a/c load.

    For my last car, Saturn SC2, I took "highway speed" to mean >~60MPH, but the Prii I've put the windows up much lower, mainly because of that popping noise.
     
    #5 gschoen, May 23, 2005
  6. DanMan32

    DanMan32 Senior Member

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    I don't do much highway driving these days. Max speed on major artery with lights (US19) is 55, but through most of Pasco, it is 45.

    AC load is variable, depending on climate conditions and conditioning requirements.

    Wayne's MPG simulator?
     
    #6 DanMan32, May 23, 2005
  7. seasalsa

    seasalsa Active Member

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    #7 seasalsa, May 23, 2005
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