Cleaned battery fan, 17% mpg boost

Discussion in 'Gen 2 Prius Fuel Economy' started by tidesofthesky, Jun 1, 2020.

  1. tidesofthesky

    tidesofthesky Member

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    Hey everyone! We are a triple Prius fam.

    We have had them for a few years and have always got about 39-41 mpg, no more, no less.

    While replacing the rear struts on my car, I decided to check the HV battery fan since it's in the same area. It was 100% clogged. I wish I had taken a picture. There was no chance of any air getting through. I cleaned it out and reinstalled, hoping that it would help with my battery longevity.

    What I didn't expect was an immediate boost to 47 mpg! This is just on a couple hour long drives, so it will probably increase even more on long road trips. Wow! I always assumed 40 was just what a high mileage Prius got.

    I also confirmed that I am on the original, unmodified battery pack (checked module date codes). 2007 Prius, 365,000 miles.

    Check your battery fans!! It might pay off.

    Posted via the PriusChat mobile app.
     
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  2. Salvage09

    Salvage09 Junior Member

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    what's the easiest way to get a look at the fan or inlet? I have no idea. ?Link?
     
  3. bisco

    bisco cookie crumbler

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    wow, well done!(y)
     
  4. Mendel Leisk

    Mendel Leisk Cloud Watcher

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    I just "followed my nose" the first time, got there. That's on a 3rd gen tho.
     
  5. GabrielD

    GabrielD Member

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    I just searched on Google this phrase "prius battery fan location" (see first attachment)
    Then, I searched here phrase "clean battery fan" (second attachment)
     

    Attached Files:

  6. dolj

    dolj Senior Member

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    Just be aware that that video made by Nutz about Bolts is Gen 3 centric, so it may not necessarily translate all that well to a Gen 2. If you use the Advanced Search options, you can limit the results to Gen 2 (and child forums) only, which would return more relevant results.
     
  7. Rocinante

    Rocinante New Member

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    I read this thread and cleaned mine yesterday, it was pretty bad, clogged with dog hair and dust. Before, my mpg was at around 43. Today my mpg was 41. It is a bit colder but damn I was expecting a boost. Would I get a check engine light if the fan wasn't working?
     
  8. Another

    Another Senior Member

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    Check battery with Dr Prius. Could be that the long time with dirty fan caused cell damage.
     
  9. alftoy

    alftoy Active Member

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    Cell damage? BMS would probably have something to say about that.
     
  10. Another

    Another Senior Member

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    Maybe
    Maybe not.
    Depends on how long any battery overheat was endured and extent of cell damage.
    Dr Prius free is a quick and simple means to see if any cells may be degrading or not. Many other tests I’m sure can be done too.
     
  11. alftoy

    alftoy Active Member

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    So which test apps do you use?
     
  12. Another

    Another Senior Member

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    Dr Prius works for me
    I don’t see any issues on n IR or diff
    YMMV
     
  13. Ginswheels

    Ginswheels Junior Member

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    I live in the Tetons at 6000 feet and below freezing 60% of the time. I get 32mpgs during the coldest weather and 51 mpgs as soon as we get into the high 30s. Things that noticeably affect mpg are weight in or on top of the car, air con use. I drive on bad roads in lousy conditions about half the time. But mine is a 2005 with only 130,000 miles so I’m pretty content.
     
  14. XrunDan

    XrunDan New Member

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    So, did all of you disconnect the hybrid battery before starting this process?
     
  15. nancytheprius

    nancytheprius Member

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    No, i did not, but i left the car off. There will be a case over the hybrid battery. Watch a video on how to clean the cooling fan. it’s not hard to get to the fan
     
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  16. edthefox5

    edthefox5 Senior Member

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    Your missing an important step in cleaning the hybrid cooling fan and that's checking that fan's plug for corrosion.

    All G2's leak rain water from cracks in the rear hatch upper corners primarily on the passenger side. To check how bad the cracks are pop off the black plastic strip on the roof. Its pulls right off. See how bad the cracks are under there they run from the upper hatch corner up that plastic cover valley.

    The leak is exactly right over the connector for the fan and drips right onto that connector. Many many reports of rotted fan connectors.

    Usually not an issue if the car is garaged but if its not its almost a guarantee you are leaking. This can be confirmed by getting a flashlight and looking in the 12 volt battery hole and look for either water or signs of rust in that battery well. Usually the battery is sitting in water.
    bad rust under the spare tire too.

    if so take the 12 out clean up the rust best you can and there's a rubber plug in the bottom. Take the plug out and drill a weep hole in it. I don't recommend removing the plug as its an easy way for mice to get into the car. They love this car's wiring.

    Also its a good idea to lubricate the fan bearing take the sticker off and put some lube in there. 20 weight oil works good.

    If you have a dog get some filter material from Home Depot cut out a piece to cover the fan inlet and attach the filter to that inlet with some velcro.
     
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  17. JayG144

    JayG144 Junior Member

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    I have this exact problem. thanks. I have to wait until it stops raining to fix it!
     
    #17 JayG144, May 14, 2022 at 11:01 PM
    Last edited by a moderator: May 16, 2022 at 11:17 AM
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  18. edthefox5

    edthefox5 Senior Member

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    Jay

    Use the search forums link up top search

    hatch leak

    lots of posts on how to mitigate the cracks.

    Good Luck!
     
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