1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Is 12.3v at the battery terminals low enough to cause trouble?(?Yes?)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Salvage09, Sep 11, 2015.

  1. Salvage09

    Salvage09 Junior Member

    Joined:
    Apr 29, 2012
    37
    11
    0
    Location:
    Pasadena CA
    Vehicle:
    2009 Prius
    Model:
    II
    My daughter across the country just bought an 05 Prius, drove it 2-3 hours home and two days later it died w the red triangle, ABS, and battery symbol lit.
    Pushing start button => can only go from Park-Neutral. Same after removing 12v ground from battery & replacing, but 12v.battery at terminals, car OFF reads 12.3v which is about half charge, for what should be a fully charged battery. Is that low enough to cause problems (so it's the 12v, not the hybrid battery?)
    From other places on PC, I get
    12 volt battery:
    Open voltage at 68 °F (20 °C):
    12.6 ⎯ 12.8 V Fully charged
    12.2 ⎯ 12.4 V Half charged
    11.5 ⎯ 11.9 V Discharged

    I know for sure that <12v is DEAD, but wasn't completely sure about 12.3.

    I think I answered my own question. If it only hits 50% when it should be fully charged, it's likely enough for the 12v battery to be the problem that it's worth replacing it first, especially since the car is throwing the ABS code as well.
    I'd still appreciate other opinions. What do the experts think?
    Thanks!!


    ANSWER!!!

    Yes, 12.3v at the battery is TOO LOW!! Replaced the 12 v battery and everything resolved immediately!
     
    #1 Salvage09, Sep 11, 2015
    Last edited: Nov 21, 2015
  2. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,463
    8,377
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    no, the 12v is not the problem. You need to get a code reader to see what's wrong with it.

    Just having purchased the car, I suspect the previous owner can probably point you to the problem (but will deny knowing anything about it).
     
  3. Beachbummm

    Beachbummm Senior Member

    Joined:
    Sep 12, 2013
    1,160
    392
    0
    Location:
    Florida
    Vehicle:
    2008 Prius
    Model:
    Five
    replace the 12 volt battery with a good quality one then reset the error codes and the lights should go out, while you have the battery out push out the rubber drain plug in the bottom of the car as sooner or later all these cars leak into that area.
    good luck
     
  4. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,463
    8,377
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    resetting the car and getting rid of the lights, does not fix the existing problem.
     
  5. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

    Joined:
    Jul 29, 2011
    3,159
    988
    0
    Location:
    Tucson, AZ
    Vehicle:
    2005 Prius
    Model:
    Four
    Yes, I agree with JC. Do not reset the car without reading the codes first. Then if they come back, you can read them again and check for consistency. There is really no way to know what the problem is without the codes.
     
  6. dorunron

    dorunron Senior Member

    Joined:
    Jul 17, 2011
    3,318
    1,103
    0
    Location:
    Houston, TX
    Vehicle:
    2013 Prius
    Model:
    Three
    I too vote with the majority on this one. 12.3 volts is weak, but still should work. It sounds like there is a issue elsewhere that needs to be addressed first.

    I would get the offending system that is causing the abs light/red triangle etc. to come on fixed, then consider whether or not I want to invest in a new 12 volt. Based on age alone, it would not surprise me if you will need to work on the traction battery, but again the codes are what you should go by. Anything else is just a guess.

    Best of luck to you.
     
  7. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,463
    8,377
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    I think you should first check to make sure all the recalls on the car are completed. If not, that could easily be the cause and it wouldn't cost a dime to fix.
     
  8. stockdaddy

    stockdaddy Member

    Joined:
    Feb 27, 2015
    208
    56
    0
    Location:
    Missouri
    Vehicle:
    2006 Prius
    Model:
    II
    You reading the 12v battery under load such as with lights on?\
    Ya the previous owner could have known there was issue. You can get a code reader for far less that it would cost for a shop to read the codes.
     
  9. Salvage09

    Salvage09 Junior Member

    Joined:
    Apr 29, 2012
    37
    11
    0
    Location:
    Pasadena CA
    Vehicle:
    2009 Prius
    Model:
    II
    ANSWER!!!

    Yes, 12.3v at the battery is TOO LOW!! Replaced the 12 v battery and everything resolved immediately!
     
  10. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,463
    8,377
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    12.3 volts is not that low where it would create problems for the Prius. Replacing the battery will not do anything
     
  11. andrewclaus

    andrewclaus Active Member

    Joined:
    Sep 15, 2009
    993
    323
    0
    Location:
    Golden, CO
    Vehicle:
    2007 Prius
    I've been keeping a close eye on my aging 12V battery and have been seeing voltages as low as 11.9 no load, 11.7 accessory mode (no fan or lights), and haven't had a problem yet (I'm replacing the battery next week). I've heard here of voltages as low as the high tens and the system still boots up. 12.3V is a good day in my car.
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,467
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    11.9 volts is what I saw, after forgetting the driver's door open for about 18 hours. I'd hazard a guess a battery at that voltage for some time would be deteriorating rapidly.