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How often do you hear your Hybrid battery fan come on?

Discussion in 'Gen 2 Prius Main Forum' started by Kaptainkid1, Jun 26, 2021.

  1. Kaptainkid1

    Kaptainkid1 Active Member

    Joined:
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    Location:
    Los Angeles
    Vehicle:
    2009 Prius
    Model:
    III
    So this past week I packed up for a 4 day road trip in central California, specifically Mammoth Lakes. Roof box full and gear in trunk maxed out. I was lugging 600lbs in gear plus myself. This wasn't my 1st road trip in the Prius either. I've owned this used Prius for about 4 years now. It's in good condition and would say it's still has a ton life in her.

    I've done two 3000 mile road trips in her. She started acting up this past week. I noticed the Hybrid Battery fan blowing more than usual and only specifically after driving in mountain roads going down long hill over 3 miles. I was coasting down hill for 10 mins and the hybrid battery life Guage showed 100% green bars.
    I never heard the fans blow this much before.

    Here is a recap of cars condition:
    2009 Prius with 188k, original Hybrid battery and new 12 volt the last month.
    No check engine or red triangle.
    No pets and car never had pets before.
    I've cleaned the hybrid battery fans by using a leaf blower before I left on my trip. Try clean any dust or dirt in the system.

    The weather in Mammoth was mild about 80 degrees out. I've driven in LA the last 4 year in hot weather 100 + degrees and up and down mountain roads before. This was the 1st time I noticed the fans were on. Is the fan coming on more often a signs of Hybrid battery failure? I think before this trip I heard the fan come on maybe 10 times in 4 years. This week I heard it come on 10 times on this trip alone and only going down hill regenerate the hybrid on to full green bars every time.
    What should I look out for? Is this hybrid battery on its way out? 20210625_093707.jpg

    SM-A526U ?
     
    #1 Kaptainkid1, Jun 26, 2021
    Last edited: Jun 26, 2021
  2. edthefox5

    edthefox5 Senior Member

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    Only heard it once in 14 years when I forgot to put windshield shade in on top of roof parking garage. Car was burning hot inside and heard the fan come full blast.

    in your case the hybrid battery is failing. It’s giving you fair warning.

    Next will be RTOD and limp mode.
    What’s your plan if far from home and it goes into limp cause that’s coming.

    You have been around here you know the score. You must have some obd tester right?
     
    #2 edthefox5, Jun 26, 2021
    davecook89t likes this.
  3. Kaptainkid1

    Kaptainkid1 Active Member

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    I have OBD2 tester and no check engine lights yet.

    SM-A526U ?
     
    #3 Kaptainkid1, Jun 26, 2021
  4. bisco

    bisco cookie crumbler

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    i have never heard ine in 3 prius over 17 years. the fan is telling you the battery has reached max operating temp.
    it can also mean that there is blockage in the ventilation system, and/or cell delta's are expanding, creating more heat.
    it generally happens in the middle of the pack, where airflow is weakest over the life of the battery.
     
    #4 bisco, Jun 26, 2021
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  5. mr_guy_mann

    mr_guy_mann Senior Member

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    If you have a compatible bluetooth adapter you can get the Dr Prius and/or Hybrid Assistant apps to monitor the battery pack. Sounds like temps are going up when the pack is near maximum charge but you are still decelerating and charging. Are you using "brake" mode on the shifter?

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Jun 26, 2021
  6. drone13

    drone13 Active Member

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    Since you have an OBDII reader it would make sense to actively monitor the battery temps while driving. The HV cooling fan is programmed to come on at various speeds at predetermined temps according to the 3 temp sensors mounted on the batteries. The idea is to progressively ramp up the cooling to keep the battery under the damage threshold. It doesn't wait until your battery is so hot it's killing itself before actively trying to cool the pack. But your pack may be near end of life if it's getting too hot even with cooling. You can easily see this by watching the temps and that's the missing piece here for anyone to give you good advice.

    You might be having cooling fan issues or blockage issues. You need to pull the rear side panel to visually inspect and test. And you need to let us know what temps the batteries are reading. There are apps that allow this with the Dr Prius app probably being the easiest to read temps and test the operation with it's special features. But other apps can do this too and some of those can log temps for later analysis with a bit of setup.

    Visually inspect the cooling fan, test it, and grab some temp readings.
     
    #6 drone13, Jun 26, 2021
    donbright likes this.
  7. Kaptainkid1

    Kaptainkid1 Active Member

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    2009 Prius
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    No B mode but the mountain road was a steep grade. It was so steep and long I was doing 70mph down hill for like 10 mins just in drive without ever hitting the gas pedal. I suspect the quick 10 min charge was taxing the Hybrid Battery charging cycle creating a lot heat in the battery pack. Once I was driving normal again the hybrid fans never came back on. Even driving back on my 350 mile trip in 100 degree heat and AC maxed out.

    SM-A526U ?
     
    #7 Kaptainkid1, Jun 27, 2021
    Last edited: Jun 27, 2021
  8. Aaron Vitolins

    Aaron Vitolins Senior Member

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    If your fuel economy and performance isn’t tanking, or seeing rapid charge/discharge cycles I wouldn’t be too worried.

    But also keep in mind your hybrid battery is 12+ years old, and lives in a hot climate (bad!) so don’t be too shocked in the not so distant future it decides to give up. Maybe start saving for a new Toyota pack.
     
    #8 Aaron Vitolins, Jun 27, 2021
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  9. donbright

    donbright Active Member

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    "I've cleaned the hybrid battery fans by using a leaf blower before I left on my trip."

    I'm wondering if its possible something was knocked loose or jammed or maybe even over-sped?
     
    #9 donbright, Jun 29, 2021
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