12V Battery is running at 14.0 - 14.1?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Ryan R, May 13, 2019.

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  1. Ryan R

    Ryan R Junior Member

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    My car died today, I guess. Lights would turn on, beeps were made, but car wouldn't start. Got a jump, and seems fine. I got it into diagnostic mode, and see the smaller battery is running at 14.1V ? Does that mean it's like overflowing with voltage? Is it on its way out? Is there something fucked?
     
    #1 Ryan R, May 13, 2019
  2. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Check the voltage with the car off, with a multimeter.
     
    #2 Mendel Leisk, May 13, 2019
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  3. fuzzy1

    fuzzy1 Senior Member

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    I don't remember if the Gen2 inverter is multi-staged, but the Gen3 definitely is. For the later, that voltage simply means that the 12V battery has a low charge level, so the voltage is boosted for faster charging. This happens a lot, after sitting a while or just running short trips that don't adequately charge the battery.

    So this voltage, by itself, does not mean that the battery is effed. Though it might be, but this system voltage won't give you an answer.

    As Mendel suggested, check the voltage when the car is off (and has been off overnight or for many hours), or in ACC mode without the car going into READY. That will give you more useful information.
     
    #3 fuzzy1, May 13, 2019
  4. exstudent

    exstudent Senior Member

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    Your observed 14.1V is in the normal range (14-14.5V) when the Prius is READY. This is equivalent to a conventional car running with the engine on, and the alternator producing 13.5V, to recharge the 12V battery. The Prius obviously does NOT have an alternator. The Prius 12V battery gets recharged slowly from the 12V bus via the HV Battery. The Prius engine will cycle on/off to make sure the HV battery is sufficiently charged.

    Is my inverter coolant pump slowly failing? | PriusChat
    Read Post #5 (how to apply a load for a more meaningful measurement of 12V battery health)
    Read Post #8 (Battery SOC (State of Charge) chart and 12V AGM compatible smart chargers to consider buying).
    ​
    As you should know, nothing lasts forever. The automotive 12V battery is no exception. It has a finite life span. Some 12V batteries will last longer than others, depending on operating climate and how many sever discharge events it has experienced.
     
    #4 exstudent, May 14, 2019
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  5. GrGramps

    GrGramps Active Member

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    Ryan, I had a similar situation recently with my Camry. Resting voltage using my multimeter showed over 16V. I've never seen it that high before, so I suspected the meter was at fault. A new battery in the meter and everything is back to normal, The meter is several years old and I had never replaced the battery.

    I wonder if anyone else has had a similar experience?
     
    #5 GrGramps, May 14, 2019
  6. bisco

    bisco cookie crumbler

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    definitely. just like prius ecu's, when the meter brain doesn't get proper voltage, it doesn't give proper readings. gigo
     
    #6 bisco, May 14, 2019
  7. Skibob

    Skibob Senior Member

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    How old is your 12v battery? How much and how far do you drive? Have you checked the battery voltage before you start the car yet?
     
    #7 Skibob, May 14, 2019
  8. Ryan R

    Ryan R Junior Member

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    Not sure on the batteries age. bought the car used. I had Midas check it, and it was loosing charge quickly, so I had it replaced. Will keep posted if issues remain and car keeps dying.
     
    #8 Ryan R, May 14, 2019
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