Prius 2016,Gen4 going downhill battery overcharged and blocked

Discussion in 'Gen 4 Prius Technical Discussion' started by Georgi Kostov, May 24, 2022.

  1. Georgi Kostov

    Georgi Kostov New Member

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    Hello guys, can i ask you if my issue is something to worry about or not.
    I drive a 2016 Prius Gen4 with 40 000 miles on it. Today i drove downhill for 7 miles without using "B" mode (i know this is my mistake). Battery charged on the first mile and then i drove with the engine braking which i know is normal. However when i got downhill and started to use my regular battery i managed to discharg it to 10% and my engine breaking was still going. Meaning my engine wasn't charging the battery as it used to do.
    What i did was to cool the engine, shut it off, let it rest, started driving carefully and the battery charged to 40% which is normal.
    I checked with OBD scan tool for errors and i couldn't find any. There were no errors, engine is runnig cool, i have regular maintenance and everything.
    Please tell me if i should worry because my warranty just expired :D
    Thank you in advance. I appreciate any help.
     
    #1 Georgi Kostov, May 24, 2022
  2. bisco

    bisco cookie crumbler

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    welcome!

    perhaps the battery was overheated, and battery protection circuit prevented charging until it cooled down.
    make sure the cooling fan grill is not blocked. do you carry any pets regularly?
     
    #2 bisco, May 24, 2022
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  3. alanclarkeau

    alanclarkeau Senior Member

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    Sounds like the electronics intervened - it'll stop it from continuing to charge to protect the battery. Had you taken it out of "B" and put it back in "D"?

    I've had similar - when it was fully charged, it took maybe 10 mins of driving back on the "flat" before it settled down. Next day it was completely back to normal.
     
    #3 alanclarkeau, May 24, 2022
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  4. Georgi Kostov

    Georgi Kostov New Member

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    I recently cleaned the air filter for the battery fan, i got really scared because i was travelling with my 2 year old son in a mountain area. Perhaps indeed the battery overheated and this was prevention to avoid any damage. I would really appreciate if Toyota put some warning labels for these kind of situations as i coudn't find any in the manual. I will drive it today and post my results, i think this issue may happen to other people. Thank you guys.
     
    #4 Georgi Kostov, May 25, 2022
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  5. bisco

    bisco cookie crumbler

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    i have read about battery protection in hot weather, but i don't recall any down mountain stories. it is certainly a possibility though.
    idk why toyota can't display a message on the screen.
     
    #5 bisco, May 25, 2022
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I've a vague recollection, some 4th gen owner a few years back had weird stuff happening, after a protracted downhill drive. Think it was a regular occurrence for him, and the word "canyon" might be in the title.
     
    #6 Mendel Leisk, May 25, 2022
  7. PaulDM

    PaulDM Active Member

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    I had this issue in my 2016 driving through a hilly Yorkshire in july.
    All I can describe it as the engine “vented” the excess charge after the battery indicator reached “all bars full”. Settled down once 50% was achieved
     
    #7 PaulDM, May 25, 2022
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  8. alanclarkeau

    alanclarkeau Senior Member

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    I think it just happens - TOYOTA has set it up to protect the battery/inverter etc.

    Just drive it - if it seems odd, the car almost certainly knows what it's doing. TOYOTA puts a 10 year warranty on the battery - they're not taking any short-cuts.
     
    #8 alanclarkeau, May 25, 2022
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  9. Georgi Kostov

    Georgi Kostov New Member

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    The problem with me is my car is bought from and auction in California and it was salvage title (back bumper and taillights were not working,everything else is brand new) so for me there is no warranty, so i try to check if everything is ok with the car. So far there is no problem with car when i am driving on regular road, but i will take it to the dealer for oil change and bring the matter and tell you what they think.
     
    #9 Georgi Kostov, May 26, 2022
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  10. bisco

    bisco cookie crumbler

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    in that case, there could be something very wrong. unfortunately, with salvage cars, it's usually a bad rewiring job that can be very difficult to find, especially if tech stream shows no codes.
     
    #10 bisco, May 26, 2022
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