jumpstart a dead Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by highmilesgarage, Feb 2, 2025.

  1. highmilesgarage

    highmilesgarage Active Member

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    car wasn't driven for more than 2 weeks, tried starting it and all the dash lights are on like a Christmas tree with the RTOD. Very dim and I said, "crap battery is finally gone".. several attempts and turned the dash into nothing.. no lights are on.. time to jumpstart. If you use another car to jumpstart you don't need to crank/start the car. The 12v will boot up the computer on the Prius and the HV battery will take over..

    https://youtube.com/shorts/xrtWWgxt4q4
     
    #1 highmilesgarage, Feb 2, 2025
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm guessing this works better than incantations, prayers and burning incense. I'll have to give it a try.
     
    #2 Mendel Leisk, Feb 2, 2025
  3. pasadena_commut

    pasadena_commut Senior Member

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    If you can, read the voltage on the 12V before you jump start it. If it is 10.0 V or something dreadful like that (below 0% charge on the AGM SOC table), it tells you that buying a replacement battery ASAP would be a good idea. They are not hard to install yourself. The only tricky part is the bolt head for the ground lead at the negative terminal, which is awkwardly located (faces the rear of the car) and requires a very small ratchet or similar device.
     
    #3 pasadena_commut, Feb 2, 2025
  4. highmilesgarage

    highmilesgarage Active Member

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    Battery is fine after driving for 30 mins, just shows that starting it up for 5 mins doesn't really maintain the charge on the 12v battery especially on cold weather days.
     
    #4 highmilesgarage, Feb 3, 2025
  5. dolj

    dolj Senior Member

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    In reality, just starting it for five minutes probably does more harm than good.
     
    #5 dolj, Feb 4, 2025
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  6. highmilesgarage

    highmilesgarage Active Member

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    took a long vacation and battery is dead again... sign that I need to replace my 12v battery.

     
    #6 highmilesgarage, Mar 19, 2025
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    How long?
     
    #7 Mendel Leisk, Mar 19, 2025
  8. Brian1954

    Brian1954 Senior Member

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    How old is your 12v battery?

    It may be time to replace it.
     
    #8 Brian1954, Mar 19, 2025
  9. highmilesgarage

    highmilesgarage Active Member

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    almost 2 weeks
     
    #9 highmilesgarage, Mar 19, 2025
  10. highmilesgarage

    highmilesgarage Active Member

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    no idea no sticker on when it was bought (I bought the car last year) I will start fine if used within a week.
     
    #10 highmilesgarage, Mar 19, 2025
  11. dolj

    dolj Senior Member

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    2 weeks is not long for down time. Your 12 V battery is toast.
     
    #11 dolj, Mar 19, 2025
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  12. MAX2

    MAX2 Senior Member

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    For a 12V battery, in addition to voltage, I recommend using the concept of "internal resistance of the battery".

    The lower the internal resistance, the better the battery copes with its duties.

    This is due to Ohm's law. U = I * (R + Rin)

    U = I * R + I * Rin

    In this formula, the first product is the useful load, the second product is the parasitic part, which is uselessly spent and only heats the battery from the inside.

    And since the initial voltage of the battery will not change, the second part takes away the battery capacity, preventing the car from starting.

    Internal resistance is the health of the battery.

    The lower its value, the better the battery.

    On the market, testers allow you to show the battery voltage and its internal resistance.


     
    #12 MAX2, Mar 19, 2025
    Last edited: Mar 19, 2025
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