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12v battery voltage?

Discussion in 'Gen 4 Prius Technical Discussion' started by rosencrantz, Nov 9, 2018.

  1. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah maybe I'm over-reacting. An electronic load test would clear up the mystery. If done by pros, I'd maybe go to a battery retailers to get such a test, say Pep Boys for example. They usually do them for free, hoping to sell you a battery. It'd be interesting to see the outcome of such a test. 12.25 volts seems really low to me though, especially for a brand new car.

    The 12volt Side of Life (Part 1)

    [​IMG]
     
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  2. alanclarkeau

    alanclarkeau Senior Member

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    Don't forget that's not for a Hybrid Vehicle's 12 volt battery - which is very different from a normal cranking battery, or an RV battery. PRIUS, as the video I posted indicated, has it's own testing procedure.
     
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  3. rosencrantz

    rosencrantz Member

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    Yeah.... as much as I’d like to get a definitive answer about the battery now, I’m not highly motivated to take the car to a pep boys or similar. With my luck, someone would somehow hook up their battery checker incorrectly and void the warranty. What I really need to do is take it into the dealer and have them evaluate it - a (IMHO) hassle.
     
  4. rosencrantz

    rosencrantz Member

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    I’m in California. Fairly moderate temperatures....
     
  5. rosencrantz

    rosencrantz Member

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    Update - I tried a second voltage meter and it read the same voltage as the first. I took the car by my local dealer hoping they’d be able to do a quick battery evaluation - no way....dealer was a madhouse. Service writer said they’d need it for “at least half the day”. I then thought I may as well try the local pep boys (thanks Mendel). Pep boys hooked my 12v up to their machine and the results indicate it’s fine.

    READINGS:
    Rated at: 295 CCA
    Measured: 463 CCA
    Measured voltage: 12.66v
    State of health: 100%
    State of charge: 80%

    I’m still a bit confused as to why the state of charge is below 100% ...... but the tech at pep boys didn’t seem concerned. Based on his test, he thinks the 12v “is absolutely fine”.

    Thanks to everyone for their input and advice. Rosencrantz
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Good Christmas present, to yourself, if that's what it takes:

    IMG_9592.JPG

     

    Attached Files:

    #26 Mendel Leisk, Nov 10, 2018
    Last edited: Nov 10, 2018
  7. rosencrantz

    rosencrantz Member

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    Good point. That video on this tester seems pretty compelling. Plus I'm ALWAYS looking for a reason to buy more tools
     
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  8. Fester

    Fester Active Member

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    I use my ScanGauge to monitor Aux and Main Battery voltage and currents. The voltage can range considerably during drive condtions, from above 14v when charging, to basically a rest voltage around 12.5v when the Aux battery is charged and happy.
     
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  9. bisco

    bisco cookie crumbler

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    prius doesn't really charge the battery well, just maintains it. you could try charging it and seeing where it holds.
     
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    I don't think I'll buy another "new" car without bringing along my Solar tester: cars sit on their lots for months, their 12 volts taking a hit.

    Dealership margins are slim; they they just want you smiling and on your way, and replacing the 12 volt is something they'd like to avoid.
     
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  11. bisco

    bisco cookie crumbler

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    i don't think it was a big problem until prius came along...
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    I noticed a VW dealership near us had little solar panel in the windshield of most cars on the lot. And in a Honda showroom, all the cars have the 12 volt neg cable pulled off.
     
  13. bisco

    bisco cookie crumbler

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    interesting. i wonder if 12 volts are getting smaller to save weight?

    or is it the plethora of constantly on electronics?
     
  14. rosencrantz

    rosencrantz Member

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    Good idea. I may try this. When I was at the madhouse dealer this morning, the service writer seemed to think that anything above 12v was good .... that was the acceptable number from from that Weber U video too. Is it possible that the car was engineered to charge the 12v battery to around 75-80% ? I’d be curious to know what the overnight resting voltage might be on another gen4
     
  15. bisco

    bisco cookie crumbler

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    a new battery will measure 13+ volts when fully charged. how long it will hold there, idk. you need to get a voltage to the computers that is within their operating parameters.
    many factors go into that, and no one can say what battery voltage under load will suffice, without all the information.
     
  16. rosencrantz

    rosencrantz Member

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    The dealer that I bought the car from wasn’t that clever. I had the impression the car wasn’t on their lot very long...but that was probably salesman talk.
     
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  17. bisco

    bisco cookie crumbler

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    they don't sit that long in cali, do they? but it doesn't take that long for a prius battery to discharge if it is left hookedup. there is a lot of draw going on all the time.

    still, with all the reports of bad ones, maybe they are just defective
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah both of the above.

    Any day ours isn't going anywhere (and that's more often than not), on goes the smart charger, and it stays on till text time the car is used.

    I'll continue to do this, will see what it does for it's longevity.

    IIRC yours have a pretty good record, with lots of abuse and neglect lol.
     
  19. bisco

    bisco cookie crumbler

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    but pip has the advantage of getting a charge every time i charge the hybrid battery, which is almost everyday except for 2 months in winter. maybe that's enough to keep it healthy?

    i keep thinking i'll get a maintainer for when we're away, but i kinda wanna see how it does without it.
     
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  20. rosencrantz

    rosencrantz Member

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    Well I’m going to, initially, monitor the battery voltage on the same schedule as checking the dipstick. Pep boys seemed to think 100% health...we’ll see....
     
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