New 12v battery? "Check Hybrid System"

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Dan0, May 1, 2017.

  1. Dan0

    Dan0 Junior Member

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    We have a 2010 prius we bought new. Never had any problems. The other day, it lost power and died just driving down our steet. Emergency start does nothing. Getting the Check Hybrid System message. Code reader says P0A94.

    Before I take it to the dealer... Should I replace the 12v battery? Who has the best deal? Voltmeter says 12 volt but... might that be deceiving?

    Thanks
     
  2. bisco

    bisco cookie crumbler

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    i was under the impression that the 12v is unnecessary to continue driving. it wouldn't to replace it at 7 years though.
    shop around, prices keep changing. internet, auto parts, dealer and batteries plus bulbs.

    a decent 12v should read at least 12.4 after everything has been off overnight.

    POA94 is inverter related, i believe, but a wonky 12v can cause the computers to act up and throw false codes.
    was your car part of the icm recall?
     
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  3. tankyuong

    tankyuong Senior Member

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    make sure the intake intake hose to throttle body is secure, and have the battery tested
     
  4. Former Member 68813

    Former Member 68813 Senior Member

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    sounds like the inverter died. it's covered by extended warranty. get it fixed.
     
  5. xliderider

    xliderider Senior Member

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    +1 on inverter failure. Try to get a flat bed tow to the dealer.
     
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  6. Dan0

    Dan0 Junior Member

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    Thanks for the replies! I'll get it to the dealer.
    I'm curious though... what's the life expectancy of that original 12v battery? We bought the car in late 2009... October I think.
     
  7. Former Member 68813

    Former Member 68813 Senior Member

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    yeah, probably not much life left. depends how lucky you feel. mine is 7 year old and still strong. never discharged much (it helps a lot).
     
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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. What does "emergency start" mean?
    2. DTC P0A94 usually means that the DC/DC converter within the inverter has failed.
    3. The usual reason that the DC/DC converter fails is after a botched jumpstart. However if your inverter is covered under an extended warranty that would be great.
    4. If you cannot make the Prius READY, you could try replacing the 12V battery as it sounds like it hasn't been previously replaced. However the battery replacement will probably not take care of the root issue.
    5. The Toyota dealer parts dept price for a replacement 12V battery is around $200. You might be able to get an Optima online for less, however it will be difficult for you to claim the Optima battery warranty from an online reseller because you'll have to ship the failed battery back, wait for a replacement to arrive, and accept the time lag associated with that process.
     
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  9. Dan0

    Dan0 Junior Member

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    Thanks again for the replies...
    We've never tried to jump start it...

    "...never discharged..." What exactly does that mean? I've read it in other posts but...

    If a dealer can sell me one for $200... that's close enough... well... we'll see...
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Don't confuse the parts price of $200 with an installed price which includes technician labor. Might be up to $300 or more.
     
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  11. Dan0

    Dan0 Junior Member

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    To swap out the battery... should I hook up my old battery to the terminals to keep from having to reprogram the radio, etc...
     
  12. bisco

    bisco cookie crumbler

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    it might be a little tricky to do that without zapping something. if you really want to save the memory, you can put 12 volts to the jumper under the hood.
     
  13. Dan0

    Dan0 Junior Member

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    20170502_190921.jpg a regular ol battery charger ok?
     
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    See whether that charger will produce 14V when it is *not* connected to a battery. If it does not, then it will not help to keep the ECUs powered up.
     
  15. bisco

    bisco cookie crumbler

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    there is a limit on the prius battery. 2 amps maybe? will that charger shut off when finished?

    edit: sorry, i thought you were gonna try and charge the battery.:oops:
     
  16. bisco

    bisco cookie crumbler

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    patrick,why do you need 14, when the car battery is 12?
     
  17. jdenenberg

    jdenenberg EE Professor

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    When you charge a battery, you need to push current into it. Therefore the "charger" must output a voltage higher than the present battery voltage, but not too high or the current will exceed the battery's ability to handle it without problems.

    JeffD
     
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  18. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The battery charger should produce a max voltage of 14.4V, although the charger is current limited; hence the actual voltage will start at a lower value.

    If it did not, it would not be able to charge a 12V battery. Recall that when an AGM 12V battery's voltage is at 12.0V, it is considered discharged. Hence a higher voltage must be applied to bring the battery up to 13.0V where it is considered 100% charged.

    An older charger may produce a slightly lower voltage as it was designed for use with a regular 12V battery where 12.6V is 100% charged.
     
  19. bisco

    bisco cookie crumbler

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    thanks! why do the ecu's need to be powered up?
     
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    They don't need to be. However the OP asked about keeping the radio presets etc.
     
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