Do I need a new 12v battery?

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by BlueV15, Sep 7, 2025 at 11:30 AM.

  1. BlueV15

    BlueV15 Junior Member

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    I've read some stuff about checking the 12v battery and I did a test over 3 days with the car off.

    After 24 hours - 12.2v
    After 48 hours - 12.2v
    After 72 hours - 12.18v

    I can't find a date on the battery, but it's a Toyota battery, so it may be the original battery. The car starts and runs normally and nothing seems out of the ordinary. Do I need a new one or can I stretch this one out longer?
     
    #1 BlueV15, Sep 7, 2025 at 11:30 AM
  2. rjparker

    rjparker Tu Humilde Sirviente

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    10 years is stretching it a bunch. The problem is an old battery on a Prius is not obvious with signs like slow cranking. As a result you could drive it 5 miles and park it at the grocery store or mall only to find yourself with a no start 1 hour later.

    But there is a test and it is not voltage readings over time. It is a load test free at most auto supplies.
     
    #2 rjparker, Sep 7, 2025 at 11:39 AM
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  3. ColoradoBoo

    ColoradoBoo Senior Member

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    Yep, visit your dealer and buy a Toyota TrueStart....comes with an 84-month warranty! (Last year, I spent $208 for one for my daughter's 2017 Prius.)
     
    #3 ColoradoBoo, Sep 7, 2025 at 12:13 PM
  4. BiomedO1

    BiomedO1 Senior Member

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    Yep, get it load tested at any auto parts store to confirm it's validity.
    Keep an eye out for future sales and maybe buy a cheap jump-box, just in case you get stranded some place.

    Good Luck....
     
    #4 BiomedO1, Sep 7, 2025 at 12:52 PM
  5. BlueV15

    BlueV15 Junior Member

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    I'm not sure if the battery is original or if it was replaced by the previous owner, I'm unable to see a date sticker. I don't want to waste money on a replacement if the battery is still usable. The voltages are in the acceptable range for what I could find online. Where, on the battery, should the date be?
     
    #5 BlueV15, Sep 9, 2025 at 12:44 PM
  6. BiomedO1

    BiomedO1 Senior Member

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    There's a date/manufacturer code stamped into the plastic somewhere.
    Voltage is only ONE parameter to check on a battery - again, it needs to be load tested - see post #4........
     
    #6 BiomedO1, Sep 9, 2025 at 1:20 PM
    Last edited: Sep 9, 2025 at 1:27 PM
  7. rjparker

    rjparker Tu Humilde Sirviente

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    Voltage is a worthless measure of a batteries health. Load testing will tell you if it can hold a charge for a day, a week or month.
     
    #7 rjparker, Sep 9, 2025 at 1:26 PM
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