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12 V battery dead after one hour with clicking noise in engine compartment

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by ewilhelm, May 1, 2023.

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  1. ewilhelm

    ewilhelm New Member

    Joined:
    May 1, 2023
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    Location:
    CA
    Vehicle:
    2012 Prius
    Model:
    V


    My 2012 Prius V's 12 V battery was dead after just an hour of being parked. Do you have any suggestions for tests or ideas? Here are the details:

    - Car was driven without issue in my normal commute the day before, ~20 minutes each way.
    - The day of, the car was driven ~ 2 miles for a kid activity drop off and then parked at home.
    - One hour later, the car would not start. The security light was blinking and the door ajar light was illuminated. Pushing the power button did nothing.
    - I measured 6 V on the battery at the fuse box, and heard a faint clicking from the engine compartment, approximately underneath the inverter coolant reservoir.
    - With a 12 volt charger applied to the fuse box, I measured 9 volts, and the faint clicking turned into a hum, like a pump that was stuck on.
    - I disconnected the battery in the trunk and directly charged the battery overnight. After reconnecting the battery, the car started as normal.
    - The 12 V battery has been replaced within the past 2 years. The car has ~80 K miles.
    - The 12 V battery has been exhausted once during the past two years when we left the trunk ajar and didn't drive the car for a week. Disconnecting it and charging it got the car to start without further issue.

    The 12 V battery isn't in perfect new condition, but discharging in an hour is a problem. Are there pumps or other systems that can occasionally get stuck in an energized condition? I'm lucky this happened when the car was parked at home, and we had other transport available.

    Thank you for your help and/or suggestions on other, better places to post this question!

    Eric
     
    #1 ewilhelm, May 1, 2023
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
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    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    it is possible that you have a drain higher than spec when the car is off.

    it is also possible that the battery is bad. get a free load test at auto zone and go from there.

    you can also do some measuring yourself, like measuring overnight voltage drop with the battery connected vs disconnected.
    and measuring voltage drop with the car off and the headlights on for 15 minutes
     
    #2 bisco, May 1, 2023
  3. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
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    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    A parasitic drain test is available to verify the car is not draining it too fast.

    Typically a parasitic draw somewhere in the neighborhood of 25 mA is normal. With a good battery it should last three or four weeks and still have enough charge to Ready the hybrid system.

    Draining a battery in one hour is almost always a worn out battery. So it's a given you need a new battery again. An auto supply or mechanic will run a simple and usually free Load Test to verify you need a battery.

    The smart thing to do after you get a new battery is to get a Parasitic Draw Test to ensure your car is not responsible for ruining the 12v battery. A mechanic can run that test.
     
    #3 rjparker, May 1, 2023
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