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Battery going flat every couple of days

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by oneian, Nov 4, 2015.

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  1. oneian

    oneian Junior Member

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    Was wondering if anyone could please help me. Prius was running wonderfully until a few weeks ago. Recently, about 2 months ago, bought a new 12v battery.
    Everything was working fine.
    About two weeks ago, the car wouldn't start. Jump started all good. Drove fine.
    If left unstarted for a day, it goes flat the next day.
    If driven every day, car will start fine.
    Battery volt reads 14.1V whilst driving. I checked on the MFD screen.
    Any suggestions / ideas please? Thank you in advance.
     
    #1 oneian, Nov 4, 2015
  2. JC91006

    JC91006 Senior Member

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    what type of battery did you buy? have you had it tested? There might be something draining the battery, do you have anything non oem installed in the car?
     
    #2 JC91006, Nov 4, 2015
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  3. oneian

    oneian Junior Member

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    it was a standard 12v battery called Power Crank with 2 years warranty. Nothing non oem - all stock. I even left the car unlocked in the garage so as to save battery from being used by the alarm/immobilizer. I had a look at the battery just then and it isn't that secure. Moves around a bit. I will fasten it down. Would that cause the drain? Thanks for your reply.
     
    #3 oneian, Nov 5, 2015
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Is it their "D51 T1"? That one is described as "exact fit".

    See if you can get a digital multimeter, measure (and post) what the voltage reads when the car's off?
     
    #4 Mendel Leisk, Nov 5, 2015
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  5. oneian

    oneian Junior Member

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    Yes, i believe it is. The battery person made sure it was for the Prius.
    Ok I'll get some digital read outs soon and advise. Thank you...
     
    #5 oneian, Nov 5, 2015
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  6. fuzzy1

    fuzzy1 Senior Member

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    The while-driving voltage doesn't matter, that is forced by the charging system. What matters is the voltage when the car is not in Ready mode, or is in just Accessory mode. This is best checked when the car has been turned off overnight, or at least for several hours, and before the car goes into Ready mode.
     
    #6 fuzzy1, Nov 5, 2015
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  7. oneian

    oneian Junior Member

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    ok, thanks - just getting a digi meter and i shall be sure to check it out :) Thank you.
     
    #7 oneian, Nov 5, 2015
  8. bisco

    bisco cookie crumbler

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    i would go back to the installer about the fit.
     
    #8 bisco, Nov 5, 2015
  9. dorunron

    dorunron Senior Member

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    Try what fuzzy1 suggested. Use the MFD, but don't have the Prius in "Ready" mode. Accessory mode will give you the voltage reading. Check it after the Prius has set over night BEFORE you start driving it. Post the reading that you see here.
     
    #9 dorunron, Nov 5, 2015
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    I recent put in an Optima replacement. It was spposedly identical dimension, but I needed to use a shim washer under the hold down bracket. That bracket design is poor, intolerant of even slight height variation. The more typical used long bolts with hooked ends are better in that regard.
     
    #10 Mendel Leisk, Nov 5, 2015
    Last edited: Nov 5, 2015
  11. fuzzy1

    fuzzy1 Senior Member

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    As dorunron mentioned, a separate digital meter is not required, the Gen2's built-in MFD should work. Just be sure to use it from Accessory before, before turning the ignition fully on.

    Those of us with Gen3s need the separate meter.
     
    #11 fuzzy1, Nov 5, 2015
  12. oneian

    oneian Junior Member

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    hi everyone, i did a battery check before starting the car - left overnight and the reading before start was 12.1V. I noticed the positive cable was quite loose, so I tightened both clamps to be sure. It is working well so far :)
     
    #12 oneian, Nov 20, 2015
  13. Lucifer

    Lucifer Senior Member

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    Exactly, you weren't charging the battery much at all, now you want to fully trickle charge it for a day or two, then after properly securing the wires to and from it and clamping it down, use it, twice a year trickle charge it full again.
     
    #13 Lucifer, Nov 20, 2015
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  14. oneian

    oneian Junior Member

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    Thank you - I shall do that :)
     
    #14 oneian, Nov 21, 2015
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