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dead 12v battery, 2007 Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Laura105, Apr 5, 2020.

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  1. Laura105

    Laura105 New Member

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    I've been a happy second-hand Prius owner for about 6 months. Today, it wouldn't start; no lights. No warnings of a dying battery - it was as if I'd left the headlights on overnight, but I hadn't. The key was on the seat - so maybe it was running a warning signal? Consulting Youtube, I used my battery booster and it started. I'm hesitant to park it away from home without any idea of what happened. Do I need a new battery? Thanks!
     
    #1 Laura105, Apr 5, 2020
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  2. bisco

    bisco cookie crumbler

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    welcome!
    the only way to find out is to test it. most auto parts stores offer free testing. or you could buy a volt meter and check it, or a charger, and see if it holds.
     
    #2 bisco, Apr 5, 2020
  3. Laura105

    Laura105 New Member

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    Thank you, bisco! That makes sense. I think the back flap wasn't quite latched, so there might have been an overhead light on for a day or two - perhaps that drained the battery. I couldn't get AT the battery directly because the flap wouldn't open when the battery was dead - could you test it from under the hood?
     
    #3 Laura105, Apr 6, 2020
  4. sam spade 2

    sam spade 2 Senior Member

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    The 12 V battery in a hybrid often does not give the early indications of failure like in a conventional car.
    Yes, it is likely that you need a new battery.
    And you are right to be concerned that is will fail to start again soon without being charged and tested or replaced.
     
    #4 sam spade 2, Apr 6, 2020
  5. PriusUkTech

    PriusUkTech Junior Member

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    Remove the 12v battery fully charge it leave it to stand for 2 days then check the voltage if it's dropped to less than 11v new battery time go for a Optima yellow top
    Posted via the PriusChat mobile app.
     
    #5 PriusUkTech, Apr 19, 2020
  6. sam spade 2

    sam spade 2 Senior Member

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    Absolutely NOT necessary to remove the battery to do that test.
    Just disconnect one of the cables to it.

    And the Optima likely is NOT the best choice......regardless of their marketing claims.
    They seem to have some quality problems and many early failures have been reported.
     
    #6 sam spade 2, Apr 20, 2020
  7. PriusUkTech

    PriusUkTech Junior Member

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    yes this is also possible but some owners only have on street parking and do not wish to charge with cable's running into the street or from there fifth story apartment widow as for the Optima Battery i have been fitted them to all my cars and customer's since 2010 Total 86 battery's and zero faults I do not work for or am sponsored by Optima
     
    #7 PriusUkTech, Apr 25, 2020
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  8. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    You can test the 12v from under the hood. Connect the red lead of the multitester to the jumppoint (look in the manual) and the black to some nearby large bolt or other ground.

    you can open the hatch if the 12v is dead. Again, instructions in the manual.
     
    #8 cyberpriusII, Apr 28, 2020
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  9. MoffettMotors

    MoffettMotors New Member

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    Replace the battery
     
    #9 MoffettMotors, May 12, 2020
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