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12 volt batt.diagnostic mode readings ???

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by CLUBGUY, Jul 17, 2017.

  1. CLUBGUY

    CLUBGUY Member

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    Five
    2012 v 64 months old, original 12 volt....

    Put screen in diagnostic mode....

    power button without pressing brake...12.2 v
    pressed power button second time 12.0 v
    put in "ready mode" 14.5 v

    Do these readings fall within an acceptable range..?
     
    #1 CLUBGUY, Jul 17, 2017
  2. rdgrimes

    rdgrimes Senior Member

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    Why do you ask? At 64 months the 12v needs replacing just on spec. Voltage doesn't tell you much of anything.
     
    #2 rdgrimes, Jul 17, 2017
  3. CLUBGUY

    CLUBGUY Member

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    Five
    Thanks for your input......"Why do you ask?"
    Seeking friendly advice...so replacement is based on the age of the battery and not the readings gleaned from the "diagnostic menu"
     
    #3 CLUBGUY, Jul 17, 2017
  4. rdgrimes

    rdgrimes Senior Member

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    Voltage readings are just a snapshot, they don't tell what it is capable of under a load, or for how long.
    "Why do you ask" is a serious question. If you have the slightest reason to think it may be weak, replace it.
    Put the system into "On" mode and run the windows up and down a few times, turn on the lights, etc.
     
    #4 rdgrimes, Jul 17, 2017
  5. rjparker

    rjparker Tu Humilde Sirviente

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    They are acceptable voltages. What voltages do not tell is how many 12v amp hours are available under load. Since the Prius does not use a 12v starter it is harder to do an in car load test. A good shop or auto supply can load test the battery when removed. You can try turning on the headlights, rear window defroster and ac blower to check the voltage drop without going to Ready mode. 11.3v under these loads is like new, below 10.3v definitely is bad. When in Ready 13.6 to 14.8 is normal but comes from the inverter not the 12v battery. Others have reported lower mpg with failing 12v batteries, but the mechanism that would cause this is not clear unless more of the HV battery is being used up feeding 12v loads.
     
    #5 rjparker, Jul 17, 2017
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