12v Battery Is Discharging, Re-Charge Now !

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Rob43, Apr 18, 2020.

  1. Salamander_King

    Salamander_King Senior Member

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    Is 11.5 volt considered "deep discharge"? Rob's chart shows that's slightly below 20% SOC.

    [​IMG]
     
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  2. thymara

    thymara Junior Member

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    Interesting video on Prius 12-volt battery, my 5.1 km, EV only, trip added 0.38V to my battery
     
    #62 thymara, Apr 23, 2020
    Last edited: Apr 23, 2020
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  3. Salamander_King

    Salamander_King Senior Member

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    Yeah, I watched the video on Gen4 threads. I want three Fluke 87 V multimeter @$395 each. My $20 Craftsman multimeter is not going to cut it. lol
    Screenshot 2020-04-20 at 2.45.26 PM.png
     
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  4. Rob43

    Rob43 Senior Member

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    I would Not recommend disconnecting the negative terminal on your 12v battery for trickle/maintenance charging. I would tell you to install the Ring connector that most of these small chargers supply, this way you'll always have a quick and simple connection.

    On a side note: If everyone were to "occasionally" (once every ~1 to 2 months) charge up their Prius Prime 12v battery with their trickle/maintenance charger, their 12v battery should last much longer.


    Let us know what you end up buying,

    Rob43
     
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  5. Rob43

    Rob43 Senior Member

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    Your 0.12 volt drop seems to be relatively inline with Salamander_King's 0.09 volt daily loss. I believe stopping your testing at ~11.90 volts (40%) is safe, but stop your low voltage testing where you are personally comfortable. Then of course, re-charge your 12v battery at your earliest convenience.

    Your contribution is appreciated.


    Rob43
     
    #65 Rob43, Apr 23, 2020
    Last edited: Apr 23, 2020
  6. Rob43

    Rob43 Senior Member

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    As mentioned by others including Mark57, we are concerned that if you actually get your Prime to a low enough 12v battery voltage where it does not start up, you'll throw multiple codes requiring you to visit your local Toyota Dealer.


    Rob43
     
  7. bisco

    bisco cookie crumbler

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    why wouldn't a jump, recharge or new battery fix that?
     
  8. Rob43

    Rob43 Senior Member

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    That of course is the goal, but it unfortunately does not always workout that way.


    Rob43
     
  9. Salamander_King

    Salamander_King Senior Member

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    I saw on a Gen4 thread Low 12 Volt Battery warning shown on dash. I can't find the thread. Does PRIME have similar warning display when 12v is low but not dead? I looked up the manual, but could not find it.
     
  10. Rob43

    Rob43 Senior Member

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    Yes, 11.5 volts would Definitely be considered a "Deep Discharge" on a 12v car battery. The truth is any of these numbers below 12.4 volts is not a good thing because something called Sulfation begins, just as it sounds, sulfation is basically cancer to a car battery.

    Length of time* & how low the voltage gets per cell (6 cells on a 12v battery) is your important consideration. Luckily our testing here is Very Short Term with daily monitoring of total voltage. Once any testing is finished, your 12v battery needs to be re-charged like already mentioned which will burn off any minor sulfation.


    Rob43

    * Very long periods of time at very low voltages are a 12v batteries enemy.
     
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  11. Salamander_King

    Salamander_King Senior Member

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    OK, I will stop the test before the voltage reaches 12.0 volt. I have set my Battery Monitor Power Alarm to 70% first and then again at 40%. If the 0.1 v/day discharge continues, it should be near 12v at a week mark. But, the fact that I had my car parked for a week at a time for the past month, and the battery before this testing began was never charged before, yet still showing ~12.5 v makes me think, it may not reach that low of SOC in a week.
     
    #71 Salamander_King, Apr 23, 2020
    Last edited: Apr 23, 2020
  12. bisco

    bisco cookie crumbler

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    this thread reminded me to put the tricle charger on my wifes hycam. 6 hours later, it's still charging. thanks for the reminder before we had a no start.
     
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  13. Rob43

    Rob43 Senior Member

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    Stop your testing wherever you feel comfortable, your testing is appreciated.


    Rob43
     
  14. Salamander_King

    Salamander_King Senior Member

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    Yeah, I will go at least two more days. That's a full week since I drove my PRIME last time, but 6 days since a full charge last Sunday. A weekly ~30 miles drive on Sunday is my current routine COVID-19 schedule.
     
    #74 Salamander_King, Apr 23, 2020
    Last edited: Apr 23, 2020
  15. Hicksite

    Hicksite Junior Member

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    I ordered the Battery Tender 4A charger. It’s going to take a couple of weeks to get it. In the meantime I’m going to monitor the battery and try to keep it fairly close to a full charge by taking it for a drive a couple of times a week and charging the traction battery when it gets down to about 30%.

    Yesterday, after no traction battery charging for a couple of weeks and no driving since Monday, I checked tha 12v battery with a voltmeter and got 12.55 volts. I checked it today and got 12.44 volts. Took it for about a 30 minute drive (half EV to run the traction battery down some and half HV to burn some gas from the original tank full) and the 12v was at 12.67 volts, which was a bigger gain than I had expected.

    I will test again tomorrow and if it is back down to around 12.5 I will charge the traction battery (got it down to 31% today) and see how much that brings up the 12v.
     
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  16. Mendel Leisk

    Mendel Leisk Senior Member

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    Fresh after a drive the battery will have a bit of surface charge (read high). Sitting overnight it'll settle back some. Still, driving helps. (y)
     
  17. Dael

    Dael Junior Member

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    damn, add some distilled water :), so called sealed batteries pfffft :) (I'm gonna get it) don't do this at home
     
  18. Salamander_King

    Salamander_King Senior Member

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    5th day after a full charge. The 12v battery is now at 12.58V or 95%. During 24 hours period on day 4, it changed from 12.64v to 12.62v, only 0.02v loss. But, during day 4, the battery monitor is reporting some increase of 12v SOC up to 12.67v. The battery may have stabilized.

    I don't think it is going to get much lower than the initial pre-full charge 12.56v 91% SOC. I will let it park longer by not driving the PRIME tomorrow. I just want to see, if it goes below 12.56v.

    Screenshot 2020-04-24 at 8.12.56 AM.png
     
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  19. thymara

    thymara Junior Member

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    The battery used in this video is European, according to the professor. My 2020 does not have the EN indication which he claimed indicated Europe, while mine is partially obscured by a sticker placed on top, most of the indication appears to be USA.
     
  20. Salamander_King

    Salamander_King Senior Member

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    My understanding is that EN is for the size group specification of Gen4 and Prime 12v battery. At the time Gen4 first came out on the US market, this size group 12v flooded lead-acid battery was very hard to find. But now, there are size spec available in aftermarket batteries. In any case, it is the same good old flooded lead-acid 12v battery.

    BTW, I just checked the photo I took of my 2020 Prime 12v battery. Mine is EN specification battery made in Japan by GS Yuasa. See the photo 20HR 45Ah CCA295A(EN).

    Screenshot 2020-04-24 at 10.15.34 AM.png
     
    #80 Salamander_King, Apr 24, 2020
    Last edited: Apr 24, 2020
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