2010 Prius 12-Volt Battery Dead Again

Discussion in 'Gen 3 Prius Main Forum' started by Yaesu, May 16, 2019.

  1. Yaesu

    Yaesu Junior Member

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    I replaced the 12-volt battery 16 months ago and it is dead. The car is stored for six months (in Florida) at a time with a battery maintainer connected. This year the maintainer would not bright the battery up to charge and when the battery voltage was checked it was at 8.7 volts. There was no indication of a faulty battery before it went into storage. The battery is from NAPA. Fob is more than 15 feet from the vehicle.
    My concern is that the battery is loosing charge while the vehicle is in storage.
    Any suggestions?
     
  2. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    What's the charger? Maybe it's defective?
     
  3. ASRDogman

    ASRDogman Senior Member

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    Was it fully charged before storage? Are you SURE you had power all the time to the charger?
    Maybe you just have a defective battery. It happens. And it should be a free replacement since
    it's under 2 years.
     
  4. bisco

    bisco cookie crumbler

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    in the future, store it with a disconnected 12v negative, and the maintainer on it.
     
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  5. Grit

    Grit Senior Member

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    If 16ft then car and fob may have kept talking to each other the entire time. You should remove fob battery and or disable SKS on the car to stop battery drain if not operating car for months.
     
  6. Yaesu

    Yaesu Junior Member

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    Thanks for the comments.

    Unless the maintainer was drawing power from the battery, I don't think it was malfunctioning, since the dead battery was discovered about two weeks after the vehicle was but into storage.

    I will be sure to disconnect the negative lead from the battery when I store it.

    As far as I know it was normally charged when the vehicle was stored. Two weeks later, after twenty-four hours on a 15 amp. charger with the battery disconnected the battery showed 100% charged, but had only 5.7 volts. Obviously the battery is defective.

    My concern is that something is drawing current from the battery while being stored. I will check the current draw when the new battery is installed.
     
  7. SFO

    SFO Senior Member

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    Though gen3 specs are different, 15 amps might be excessive when trickle or fast charging a 12v AGM battery.
     
  8. frodoz737

    frodoz737 Top Wrench

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    Any vehicle stored this long should have the battery completely disconnected and removed.
     
  9. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    And the charger is not really up to the task either. What was the charger. FWIW third gen Owner's Manual recommends 3~4 amp charge rate max. I'd recommend looking into smart chargers in that range. CTEK 4.3 is good.

    1. Long term, secure storage (locked garage), leaving the battery continously connected to smart charger, you'd be fine, even with the battery connected.

    2. Long term non-secure storage, say parked in a driveway or on the street, fully charging and then disconnecting, then disconnecting the negative battery connection, you'd also likely be fine. Say for up to 6 months.

    3. Doing #2 but in secure storage is a good ploy too, and a little safer than #1, just in case something goes awry with your charger.
     
    #9 Mendel Leisk, May 18, 2019 at 1:32 PM
    Last edited: May 18, 2019 at 1:38 PM
  10. Yaesu

    Yaesu Junior Member

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    The maintainer I have been using is a Deltran Battery Tender. After over a week on the maintainer the battery wouldn't come up to charge. Then I tried the larger (smart charger) and it wouldn't bring the battery up to full charge either.

    I think it's best to disconnect the battery from the vehicle for long-term storage, in case the maintainer fails.

    There are volt meters available that connect to the Internet allowing for long distance monitoring of battery charge. Unfortunately there is no WiFi where I store the Prius.
     
  11. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    That doesn't sound good. Maybe get something like Solar BA5 to verify? And/or to monitor the replacement? Long term storage is going to require some strategy, likely #2 option above, to avoid a repeat.
     
  12. Yaesu

    Yaesu Junior Member

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    Over the course of a year I store and maintain almost twenty batteries. I use a timer (four to six hours on per day) on some of the battery maintainers. There doesn't appear to be a problem when used part time every day.
     
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  13. kc5dlo

    kc5dlo Member

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    I know that many battery maintainers are not parasitic when unplugged from the wall but the one I have from Harbor freight will discharge the battery when the power supply is off or unplugged. It works fine for what I use it for but could see where it might be an issue for some applications.
     
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