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12v issue... I think

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by OldlinePrius, Aug 5, 2021.

  1. OldlinePrius

    OldlinePrius New Member

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    so I posted a question a few days ago about an issue with the 12v battery. after I got it towed back to my house and spoke to AAA , I decided to replace the battery in the back my self. Before I bough at new battery I removed the "old" one and tested it with a multimeter it came up 11.45 volts so I took the battery back out to the car and reinstalled it until I order a new one. Once I was done I hit the key fob to lock out of habit, surprise to me it locked went over and checked and the car started right up. I tested the onboard battery tester (by holding display and turning the lights on and off about 3-4 times) and while it was off and it was changing between 12v and 11.9 volts , with the Prius on it was 14v.

    could the issue have been that it wasn't secured that well , I didn't notice anything that was alarming when removing it , and the battery is only from 3/19
     
    #1 OldlinePrius, Aug 5, 2021
  2. sam spade 2

    sam spade 2 Senior Member

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    Yes.
    But now it needs to be fully charged and you can't trust the car to do that for you.
    You need to buy or borrow a small charger.
     
    #2 sam spade 2, Aug 5, 2021
  3. SFO

    SFO Senior Member

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    How many hours per week are you currently driving?
     
    #3 SFO, Aug 5, 2021
  4. OldlinePrius

    OldlinePrius New Member

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    I work 4 days a week and my job is 52 mins away
     
    #4 OldlinePrius, Aug 5, 2021
  5. dolj

    dolj Senior Member

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    +1 to Sam's advice, get that battery fully charged.

    Leaving a lead/Acid battery in a discharged state (which at 11.45 V, it is) will drastically shorten its service life. So, get that battery on a charger now.

    When it is fully charged (which could take 12 - 18 hours depending on the charger), get it tested with a 12 V battery load tester. You can then make a decision about replacing or whether you can live with this battery for a bit longer.
     
    #5 dolj, Aug 6, 2021
  6. edthefox5

    edthefox5 Senior Member

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    How many times have you had to jump start this battery?

    With your multimeter lets do a quick load test. With car off Measure the dc volt at the front jump point. Remember that.
    With car off turn on the headlights in high beam. Leave them on for 5 minutes. Shut them off wait 1 minute then measure the dc volts at the front jump point. What's that measure?

    And as far as the battery not being secured or bad connection you could have tested that easily just measure the front jump point and then compare to the battery itself. Should not see more than .5 volt drop difference to the front.

    That 12 volt battery has to go through 8 connections and a big long cable before it gets to the front main fuse box to do its job. That long cable from the battery is bolted to the front jump point. Never measure the battery always measure the FJP.

    It only matters what it measures there.
     
    #6 edthefox5, Aug 6, 2021
  7. SFO

    SFO Senior Member

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    8 hours per week should be enough driving to keep the 12v alive.

    FYI : your posts are being moderated until you've posted 5 times.
     
    #7 SFO, Aug 6, 2021
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