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Why did my battery go flat so quick ?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by maggotdrowner, Jun 16, 2020.

  1. maggotdrowner

    maggotdrowner Junior Member

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    I accidently left the key turned on in the ignition and one door was open for about an hour last week.

    When i noticed it i thought it would be ok but it was flat.

    I thought it would only use a tiny bit of power with one internal light lit and the dashboard lights on.

    Any ideas why ? Thanks
     
    #1 maggotdrowner, Jun 16, 2020
  2. bisco

    bisco cookie crumbler

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    tiny battery that is probably close to worn out anyway. very typical for prius, how old is the battery?
     
    #2 bisco, Jun 16, 2020
  3. jzchen

    jzchen Newbie!

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    Deleted... Let others answer...
     
    #3 jzchen, Jun 16, 2020
  4. fuzzy1

    fuzzy1 Senior Member

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    I'm not clear just what you mean by "key turned on in the ignition". But just leaving a door open keeps some electronics awake, much more than a single internal light. Then add in the accessory or non-Ready On mode, and far more electronics is turned on behind that dashboard. The lights you see turned on are just the tip of the electric load iceberg.
     
    #4 fuzzy1, Jun 16, 2020
    Last edited: Jun 16, 2020
    jzchen and Ed Beaty like this.
  5. sam spade 2

    sam spade 2 Senior Member

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    How old was your 12 V battery at that point ?
    If it is the original one, you are WAY lucky that it lasted that long.
    Most don't come anywhere near to 9 years.
     
    #5 sam spade 2, Jun 16, 2020
  6. maggotdrowner

    maggotdrowner Junior Member

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    Thanks for the replies.
    The battery is 4yrs old.
     
    #6 maggotdrowner, Jun 16, 2020
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  7. sam spade 2

    sam spade 2 Senior Member

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    While not the total cause, that likely is a factor.
    Especially if it has ever been run down before.
     
    #7 sam spade 2, Jun 16, 2020
  8. bisco

    bisco cookie crumbler

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    just put a smart charger on it, or leave it 'ready for 8 hours, and you'll be fine
     
    #8 bisco, Jun 16, 2020
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