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No voltage measured across "12V" battery after recharging

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by gdowdy3, Sep 1, 2024 at 1:17 PM.

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  1. gdowdy3

    gdowdy3 New Member

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    Hello folks,

    Last weekend, I tried to use my Prius after it sat idle for a month and a half. However, I found that the car was utterly unresponsive: the door locks wouldn't work, the ignition button did nothing, no dash lights, and so on. I thought that the "12V" battery might be dead as a result of the prolonged period of inactivity. I tried to measure the voltage across this battery with my voltmeter. It reported no voltage.

    So, I tried to charge my battery with a "DieHard 71219 6/12V Shelf Smart Battery Charger". The charger showed that it was charging for about 2 hours, then declared the battery to be fully charged. However, still the car is unresponsive. Furthermore, when I try to measure the voltage across the terminals of the battery, I am again seeing 0 V.

    The battery is pretty new. I bought just late last year. Furthermore, I bought it from a local Toyota dealer, so it's not like it's some sketchy off-brand.

    Anyone have any analysis of the situation? Do I just have a bad battery? Are there any other tests you recommend before coming to this conclusion?

    Feel free to ask follow-up questions. I'm happy to provide additional details that might help you diagnose the problem.

    Garrett
     
    #1 gdowdy3, Sep 1, 2024 at 1:17 PM
  2. ChapmanF

    ChapmanF Senior Member

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    Sounds like the month and a half without charge has done in the battery.

    If it was from a Toyota dealer late last year, you may be eligible for at least a pro rata and possibly full price toward a replacement if you take it back to them. Before covering it, they will put it on their own tester to see if it's really kaput.
     
    #2 ChapmanF, Sep 1, 2024 at 1:23 PM
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  3. mr_guy_mann

    mr_guy_mann Senior Member

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    I would check that your meter actually reads (DC) voltage correctly.
    Many "smart chargers" won't work correctly if the target battery is completely dead.

    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Sep 1, 2024 at 2:42 PM
  4. rjparker

    rjparker Tu Humilde Sirviente

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    Agree. Also make sure your voltmeter is not on AC. It will read zero dc in that mode no matter what. Simply check a 1.5 or 9v battery that you have in a drawer or a remote.
     
    #4 rjparker, Sep 1, 2024 at 2:48 PM
  5. gdowdy3

    gdowdy3 New Member

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    Thanks for weighing in, guys!

    Fortunately, my wife has a Prius with a working "12V" battery, which allows me to take comparative measurements. If I try to measure the voltage of her "12V" battery with the same voltmeter, it reads 12.4 V, and also reports "DC". So I don't think my voltmeter is the problem.
     
    #5 gdowdy3, Sep 1, 2024 at 2:57 PM
  6. gdowdy3

    gdowdy3 New Member

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    Any other suggestions for what I should check before I take the battery back to the Toyota dealer?
     
    #6 gdowdy3, Sep 1, 2024 at 3:24 PM
  7. rjparker

    rjparker Tu Humilde Sirviente

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    If it’s a true zero volts it has an open connection internally.

    I would swap batteries to know for sure. But you should get a new battery from the dealer.
     
    #7 rjparker, Sep 1, 2024 at 4:39 PM
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