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2005 and 2006 prius 12v battery problems

Discussion in 'Gen 2 Prius Main Forum' started by Mike Thomas Bourque, Sep 30, 2017.

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  1. Mike Thomas Bourque

    Mike Thomas Bourque New Member

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    2004 Prius
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    i have 2 prius that have been parked for awhile and were only started once every two or tree weeks for the past year. so i came home ,they are both dead. the 2006 i boosted, it started runs fine but if its stopped for more than 1-2 hours its dead and wont start again.. need to re boost it (i havent had it running for more than an hour and did that twice, it started up fine after, but once it was turned off for a while it wont start, i did check and the battery reads 13.9 to 14 v on the prius screen.

    the other one will not go passed accesery when boosting mode and has a battery sign logo that says main on top left of screen, what could this be?
     
    #1 Mike Thomas Bourque, Sep 30, 2017
  2. SFO

    SFO Senior Member

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    Sounds like you are having 12v battery issues.
     
    #2 SFO, Sep 30, 2017
  3. dolj

    dolj Senior Member

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    If this is with the car showing READY or just after switching off, then it doesn't really tell you much. Read the voltage at the battery using a voltmeter after the car has been off for at least 2 hours. if it is less than 12 V, replace the 12 V battery with a new one. If it is above 12 V use an automatic multi-stage battery charger with an AGM setting to charge it overnight or until the charger indicates it is fully charged. Wait 2 hours after disconnecting the charger, then test again. If the voltage is less than 12.4 V replace the 12 V battery.
    For this car, I would say that in addition to your 12 v battery dying, your HV battery may have self-discharged to the point the car can longer start. You will need to have the HV battery charged externally either at the dealer using their HV battery charger or by buying a grid charger such as the one sold by Hybrid Automotive. Just a guess, but retrieving the DTCs using a Prius aware scanner will give you a better idea on this one.

    There is fuel in the car, right?
     
    #3 dolj, Sep 30, 2017
    Last edited: Sep 30, 2017
  4. fotomoto

    fotomoto Senior Member

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    You (most likely) have bigger problems than the 12v issues. Letting those old HV batteries sit unused for long periods of time is very bad for their lifespan.

    GOOD LUCK!
     
    #4 fotomoto, Sep 30, 2017
  5. Mike Thomas Bourque

    Mike Thomas Bourque New Member

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    Location:
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    Vehicle:
    2004 Prius
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    So the 2006 (one that the 12v battery seems to be the only problem) seems like its just the 12v battery

    the 2005 (one that wouldnt go passed accessory mode ) it started when i first started it yester day left it on for awhile, only the engine ran, then i drove off, and i stopped to check something in the back, as soon as i pressed the "Park" button, it shut down completly, then when boosting it again wouldnt go passed accesory mode with the "battery sign, the little red light that looks like a 12v battery , on the top left corner of the screen )
     
    #5 Mike Thomas Bourque, Oct 1, 2017
  6. JC91006

    JC91006 Senior Member

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    You would need to fully charge the batteries and load test them. Replace if necessary. This is the only solution
     
    #6 JC91006, Oct 1, 2017
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