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Failed start up battery

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by alanwagen, Sep 30, 2022.

  1. alanwagen

    alanwagen Member

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    2018 Prius, it still starts but the battery test which I did myself shows 134CCA. It also reads around 12.2 volts.
    My local dealer is charging $181 for a True Start 84 month battery, 2 years, free replacement. So I am leaning towards that.
     
    #1 alanwagen, Sep 30, 2022
  2. JC91006

    JC91006 Senior Member

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    12.2 volts on a 4 year old battery, what seems to be the problem? It shouldn't need a replacement. At most, you might want to just charge it up, but it's not even that low.
     
    #2 JC91006, Sep 30, 2022
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  3. Mendel Leisk

    Mendel Leisk Senior Member

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    134 cca doesn't bode good.
     
    #3 Mendel Leisk, Sep 30, 2022
  4. Doug McC

    Doug McC Active Member

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    Which battery tester did you use and what settings did you use? Also, what numbers are on your battery. 12.2 volts is actually not that low for a Prius. I would put a charge on it (stay 5 amps or less) and test it again before I’d buy a new one.
     
    #4 Doug McC, Sep 30, 2022
  5. alanwagen

    alanwagen Member

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    I used a Konnwei Battery tester set for 295CCA.

    The 134CCA is not good. It would never get above 12.2 and it should be at least 12.5. It was on it's way out. It failed on their battery tester.

    So I went to the dealer in Fort Worth and with a coupon, I bought a 84 month True Start, with 470CCA for only $162 out the door installed.
    Cheaper than my local Auto Supply stores. I tested it when I got home and it was 471 CCA. They even greased up the terminals to curb corrosion.

     
    #5 alanwagen, Sep 30, 2022
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  6. Doug McC

    Doug McC Active Member

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    I think you made a wise choice (FWTW). And that price and service are great. You seem to have a good dealership to work with.
     
    #6 Doug McC, Sep 30, 2022
  7. alanclarkeau

    alanclarkeau Senior Member

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    CCA is irrelevant in a PRIUS. Was it showing signs of failing? Mine is almost 6½ yrs old and going fine.
     
    #7 alanclarkeau, Oct 1, 2022
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  8. alanwagen

    alanwagen Member

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    Low voltage and only 134 CCA out of 295. Failed several battery tests.
     
    #8 alanwagen, Oct 1, 2022
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  9. Doug McC

    Doug McC Active Member

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    CCA IS relevant to battery health, though. Couple that with high internal resistance and what energy is left in the battery drops quickly when any load is put on it.
     
    #9 Doug McC, Oct 1, 2022
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Not really: it still indicates a failing battery.
     
    #10 Mendel Leisk, Oct 1, 2022
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  11. BiomedO1

    BiomedO1 Senior Member

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    Yes, the battery wasn't in peak condition - but it's only used to close relays and power accessories. The starting motor, in the transmission, is powered by the traction battery.
    IMHO: If the battery started getting below 12VDC and/or there was weird sensor errors - then I would've replaced it. The battery on my dirt/camping truck is more than 7 years old and always around 11.75VDC when I put the charger on it. I don't drive it much, because of gas prices, but I have started it at that voltage and throw a jump pack into it, when I'm in a hurry.
    I do take care of my batteries and check electrolyte levels annually.

    Just my 2 cents......
     
    #11 BiomedO1, Oct 1, 2022
    Last edited: Oct 1, 2022
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  12. alanwagen

    alanwagen Member

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    I'm glad I replaced it as it will effect gas mileage and why wait to be stranded.
     
    #12 alanwagen, Oct 1, 2022
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  13. alanwagen

    alanwagen Member

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    But you would think the dealer had a battery saver to keep my settings. I had to set the clock and calendar plus a few other settings. Not a big deal but they should of done it.
     
    #13 alanwagen, Oct 1, 2022
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  14. bisco

    bisco cookie crumbler

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    dealers :rolleyes:
     
    #14 bisco, Oct 1, 2022
  15. alanclarkeau

    alanclarkeau Senior Member

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    Interested - how would it affect fuel mileage?
     
    #15 alanclarkeau, Oct 2, 2022
  16. alanwagen

    alanwagen Member

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    Because the car would be trying to charge it constantly which uses more electricity. If fact, our last trip we got over 70 mpg, before it was less.
     
    #16 alanwagen, Oct 2, 2022
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  17. alanclarkeau

    alanclarkeau Senior Member

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    I suspect that would be negligible - but you've got a new battery - so should be right for 6 or so years now.
     
    #17 alanclarkeau, Oct 2, 2022
  18. alanwagen

    alanwagen Member

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    You would think but the Prius is so optimized and sensitive that wind, rain and cold effects the mileage. Back when I had a 2010 Prius and the battery failed, after replacement, the mileage increased. A bad battery is a constant drain as the computer thinks it needs charging but never tops off.
     
    #18 alanwagen, Oct 2, 2022
  19. Doug McC

    Doug McC Active Member

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    The system is designed to maintain a full charge status of ~12.5 volts, charging at a maximum ~14.1 volts. If the 12 volt battery cannot hold that charge, then the system continually tries to get it there via the hybrid battery, thus requiring the ice to run more frequently to charge the hybrid battery. The more frequent draw and charging of the hybrid battery increases the temperature of the hybrid battery, resulting in the system limiting the use of the EV mode to reduce the load on the hybrid battery to minimize its temperature, resulting in the ice running more frequently to move the vehicle, resulting in an increase in gasoline use. The health of that little 12 volt box is more critical than most of us realize.
     
    #19 Doug McC, Oct 2, 2022
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