12 volt battery questions

Discussion in 'Gen 4 Prius Main Forum' started by Chris Wolfgram, Sep 12, 2025 at 4:41 PM.

  1. Chris Wolfgram

    Chris Wolfgram Active Member

    Joined:
    Oct 20, 2019
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    Location:
    Sacramento CA
    Vehicle:
    2019 Prius
    Model:
    LE
    So I hopped in my car 15 minutes ago, pressed the brake pedal, and hit the start button, and I got the pop up > 12 volt battery low. Then it wouldn't let me start the car.

    First time I've ever gotten this with either of my two Gen 4's.

    I remember seeing stuff about this....
    Like the Toyota Prius OEM batteries were rediculous expensive, but some folks adapted cheaper batteries..
    I don't remember all those details ?

    Any 12 volt battery advice for my 22' XLE ?

    Oh, of course I could throw a charger in it...
    But even if it gave it enough juice to start one time, it might only get me to my next destination and strand me there ?
    At least this happened at home....
     
  2. BiomedO1

    BiomedO1 Senior Member

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    check the electrolyte levels and recharge it.
    Take it to any chain auto parts store for a free scan/load test to see where it is.
    It's a H4 or 140R group size battery configuration - but batteries are expensive these days. You can check stock at Sam's & Costco too, for convenience.
    My 21 Prime battery needs a recharge about once a year; I find it below 12VDC every once in a while and throw a charger on it for an hour @ 6A. It's never failed to start, but I did get the FOB battery low message earlier this year.
     
    #2 BiomedO1, Sep 12, 2025 at 4:50 PM
    Last edited: Sep 12, 2025 at 4:57 PM
  3. Chris Wolfgram

    Chris Wolfgram Active Member

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    Location:
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    Vehicle:
    2019 Prius
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    LE
    Thank you Bio.
    I found a 3 yr replacement at my local Walmart, for $159....
    Not bad + I don't want to risk the battery charging "just enough" to get me a long ways from home, then failing again, and if I kill this one in 2 or 2 1/2 yrs, I'll just grab another, free of charge .... Well not really free, I'm just paying for it now
     
    BiomedO1 likes this.
  4. jdenenberg

    jdenenberg EE Professor

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    Location:
    Trumbull, CT
    Vehicle:
    2020 Prius
    Model:
    LE AWD-e
    Our Prii tend to not charge the 12v battery sufficiently if you do short trips. Besides, these days you can have a rechargeable lithium jump starter in you glove box. Then you don't have to worry about a weak 12v battery. My 2020 12v gets flagged as weak by the dealer every 6 months (Low Cold Cranking Amps). I may replace it when we get into cold weather as it will be about 6 years old.

    JeffD