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Brand new 12 volt battery not reaching 100% state of charge

Discussion in 'Gen 2 Prius Main Forum' started by GTW, Aug 7, 2018.

  1. GTW

    GTW Junior Member

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    Yesterday I took the first Prius battery to O'Reilly's, their tester indicated the battery was bad. I asked them if they could try to charge it and I was told to come back in a couple of hours. After the allotted time, they again told me that the battery was bad. Nothing more specific than that.

    I placed the CTEK charger in the 3rd mode (for Yellow Top battery), and left it to do its thing. Right away the charger Advanced to the fourth of eight steps. After a few hours the charger got all the way to the Float stage( stage 7). That's where it is now.

    The charger went through stage 5 (Analyze) and it continued on to Float. I take that to mean that it is holding some kind of a charge, at least temporarily.

    Should I let the battery remain in Float for 10 more hours or should I disconnect it, wait 10 hours and then meter it?

    Thank you.

    PS. The Yellow Top is still in the car. I want to see if the first battery will hold a charge in the Prius, now that it has gone through the proper full charging cycle.
     
  2. dolj

    dolj Senior Member

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    You give the impression that this battery charged up from flat (discharged; 11.2 V) to full in a short time. This is not necessary a good thing.
    Yes, do this, but no need to let it stay on trickle. Just remove the charger and measure the voltage when you disconnect the battery charger, and then measure it again after 2 hours. After this, apply a 60 - 100 W load for 15 mins and then measure the voltage again after the 15 min and while still under load. Finally remove the load and leave it to rest for 2 hours. Take a final measurement after resting for the 2 hours.

    Note all those measurements and post here for comment. Also, mention what the load was (as in how many Watts load).

    PS, if you don't have a load, let it sit for 24 hours instead of load testing and then measure before and after sitting 24 hours.
     
  3. GTW

    GTW Junior Member

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    Thank you. Since I don't have a predictable DC Load, I'll be back in 24 hours with the next measurement. The 1rst reading (off of Float) was 13:.54 V, but the meter immediately displayed a downward trend. We'll see where it lands after a day. Thank you so much.
     
  4. dolj

    dolj Senior Member

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    That is normal, it is called surface charge and will bleed of and stabilise within 2 hours. That is why I want you to wait 2 hours and then do another reading. Then wait for 24 hours to do the next reading.
     
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  5. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    This is not the Yellow Top battery I assume? Yeah drive the car for a day or two, then check the Yellow Top voltage first thing in the morning. In precisely that scenario, ours read about 12.75 volts. It was brand new, charged with CTEK 4.3, then a day or so later, with a bit of driving.

    Note that O'Reilly is likely testing with an electronic load tester, a pro version of something like the Solar BA5 or BA7. These can read the voltage, plus: you enter parameters about the battery, whether it's AGM or regular acid-flooded type, the specificied Cold Cranking Amps, then test, and it tells you the actual CCA, and gives a verdict, either "ok", "charge", or "fail". I think the verdict is a combo of the measured CCA and voltage.

    I have the Solar BA5, think it was around $70. The BA7 is more prevalent now, about the same price, and there are a number of other DIY level testers on the market now as well. The Solar product works but is fairly rudimentary, so maybe you would want to research.

    I appreciate getting a DIY load tester is a bit of a stretch, but when you think about it, the myriad battery questions here invariably boil down to "what is the status of my battery". The voltage is part of the story, but these electronic load testers really clear up the mystery.

     
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  6. GTW

    GTW Junior Member

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    The 2 hour reading was 12.92 V
     
  7. bisco

    bisco cookie crumbler

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    so far, so good!
     
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  8. GTW

    GTW Junior Member

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    After 24 hours, the voltage reading is 12. 78 V, and statically is holding steady.
    Just to be clear, this is the battery which came with the car, and O'Reilly's Auto Parts had tested as being bad.

    The Yellow Top battery (currently in the Prius) is receiving an umbilical charge via the fuse box points. It is still in stage 4.
     
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  9. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    Now that you've got the bug, I think you'll be needing a Solar BA5 or equivalent. :whistle:
     
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  10. GTW

    GTW Junior Member

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    I'm back from work. So just about 36 hours after taking the first battery off of float, the voltage measures at 12. 76. I will put it back in the car and see how it does.
     
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  11. bisco

    bisco cookie crumbler

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    sounds fine.
     
  12. GTW

    GTW Junior Member

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    The battery measured with mixed results. After install, Diagnostic mode (car off) showed 10.4V .
    The
    However, the car started normally, no warning lights. I drove about 20 miles. At the end of the drive (car off), I measured directly off the battery, it reads 12.48 V . I'll let it sit for a couple of hours, and measure again.

    After 3 hours, the voltage at the battery is 12.38. Wondering if the Recondition mode on the smart charger would help?

    BTW, the Yellow top, after a full charging cycle, is holding 13.28V.
     
    #52 GTW, Aug 11, 2018
    Last edited: Aug 11, 2018
  13. sam spade 2

    sam spade 2 Senior Member

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    There is something funny going on here.

    You NEED to measure the voltage with the car "running".
    It needs to be at least 13.4.

    Also, you might have a loose or corroded cable connection at the OTHER end of one of the main battery cables.
    You have switched the battery often enough that the connections AT the battery should be good......probably.
     
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  14. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    All of this has me thinking your battery is indeed a dud. A freshly charged brand-new battery should be reading over 13.0, due to "surface charge". After a bit of driving and a rest, it might settle down around 12.7~12.8. And an electronic load test (possibly what O'Reilly's did??) would test it's Cold Cranking Amps capacity, basically going beyond just measuring voltage, measuring the "health" of the battery, it's capacity.

    Have you posted where you got this battery, was it local or mail order. I would get an electronic load test, either DIY with something like Solar BA5, or back to O'Reilly's (if in fact that's what they're doing), get some proof, even a photograph of the Solar BA5 displayed CCA and verdict for example, and get back to the seller, for a refund.
     
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  15. bisco

    bisco cookie crumbler

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    no point to doing all this measuring with the car on or driving. if it is holding 12.76 after 36 hours, then dropping way down with a load, it's toast.
     
  16. dolj

    dolj Senior Member

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    Agreed. Your Yellowtop sounds like it the better one. Give that a good charge and the drop it in.

    Also, check the connection of the negative cable to the car body (in the back) is clean and tight. Ensure the battery positive and negative connections are clean and tight too.
     
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