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12v battery fully charged, not starting

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Brian Udell, May 6, 2017.

  1. Brian Udell

    Brian Udell New Member

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    May 6, 2017
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    Location:
    Minnesota
    Vehicle:
    2007 Prius
    Model:
    ----USA----
    It ran fine just a couple days ago. I came out the next morning and it looked like my wife may have left one of the doors slightly ajar over night. I tried starting it and the dash lights flashed so i figured the 12v battery was drained. I tried jumping it with no luck, had to get to work so I took our other car.

    That night I took a multimeter to the battery. It read 7.9v. I gave it a full charge using a plug-in battery charger. Inspected the terminals, reconnected it, still the same problem.

    Some details
    - battery was replaced 2.5 years ago and seems to hold a charge decently.
    - prius is 2007 and has 115k miles on it. Had an oil change and inspection a couple months ago, no big problems detected.
    - this is exactly what happens when i press Power with the brake pedal depressed:
    1 - dash lights up, appears normal for a few seconds.
    2 - all the dash lights begin to flash (transmission, gas gauge, etc) ICE NEVER kicks in. Touch screen never turns on. Radio never turns on.
    3 - after several flashes, all of the dash lights turn off except for Check Engine. I am able to operate the power locks and Windows, but not for very long.

    The Red Triangle NEVER turns on throughout this.

    Any ideas?
     
    #1 Brian Udell, May 6, 2017
  2. RobertK

    RobertK Member

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    Location:
    Norfolk, VA
    Vehicle:
    2007 Prius
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    N/A
    What was the battery voltage after you charged it? What charging rate does your charger provide? It is possible that you didn't give the charger enough time to fully charge the battery. You also might have some shorted cells, in which case the battery will never fully charge. You should also check the battery connections at the battery and the negative battery cable connection to the car body.

    If you are using a charger that plugs in to the 12V accessory socket, I don't think that will charge the car while it is off, since those outlets are switched. I don't have first hand experience with that, so I could be mistaken about that. I always connect a charger to the jump point under the hood.
     
    #2 RobertK, May 6, 2017
  3. Sam Spade

    Sam Spade Senior Member

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    Vehicle:
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    Four
    Not only possible but likely, I think.
    To get a full charge on a battery that low would require about 10 hours, with a small charger that is common in most people's garage.

    BUT......having it THAT low probably means it is SHOT. Since you have a voltmeter, why did you stop checking the voltage ??
    It probably goes way back down when subjected to a load.
     
    #3 Sam Spade, May 6, 2017
  4. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
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    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV
    Is it accepting amperage when charging?

    7v usually means serious damage from extended period being drained.. How long was door agar? Even a dead battery still has voltage in the 11's or very high 10's.
    If drained and left drained for a few days it really sulphates the plates to prevent future proper charging.

    If you do have a short the battery will get hot when charging... Starting from that bad cell.

    Regardless you should have some warranty left if only 2 years.

    Just how small is your charger? What's the max amperage it can do?

    SM-N910V ?
     
    #4 windstrings, May 6, 2017
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Vehicle:
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    Yes, this is the big question. 7.9 volts at the outset doesn't sound good.
     
    #5 Mendel Leisk, May 6, 2017
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