maintaining 12v Batt while using Techstream

Discussion in 'Gen 2 Prius Technical Discussion' started by RC-Pilot232, Jul 9, 2017.

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  1. RC-Pilot232

    RC-Pilot232 Junior Member

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    What is the the minimum voltage I need to maintain the 12v battery with the car, on in not-ready mode.
    So the HV Battery doesn't get depleted charging the 12v. While I learn Techstream? I have a server PSU that I have modded to output 13 volts 65 amps [for RC chargers]. I can change a resistor to get that up to 13.5v, amperage will drop, but shouldn't be an issue using it this way. Is 13.5 volts enough? And all lights & climate
    controls off.

    Thanks,
    Ned
     
    #1 RC-Pilot232, Jul 9, 2017
  2. dolj

    dolj Senior Member

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    You need to output 13.6 V @ 2.5 - 4 A to effectively create a trickle charger.

    4 A is the maximum recommended current for the 12 V OEM AGM battery.
     
    #2 dolj, Jul 9, 2017
    Last edited: Jul 10, 2017
  3. edthefox5

    edthefox5 Senior Member

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    Just buy a battery charger there not expensive and it's a good idea to maintain the 12 volt battery. I put mine on my 12 volt battery at least once a month to check its health.
     
    #3 edthefox5, Jul 10, 2017
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  4. Fred_H

    Fred_H Misoversimplifier

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    Maintaining at least 12.8 Volts will prevent the battery from discharging. That is not high enough to do any significant charging, but high enough to maintain the existing state of charge.
     
    #4 Fred_H, Jul 10, 2017
    Last edited: Jul 10, 2017
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  5. Mendel Leisk

    Mendel Leisk Senior Member

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    ^ This. Any half decent smart charger can be left on indefinitely. It'll run through a charging session, then revert to giving just slight, periodic charging, if and when needed.
     
    #5 Mendel Leisk, Jul 10, 2017
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  6. RC-Pilot232

    RC-Pilot232 Junior Member

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    Thanks everyone, but no one answered my original question.

    Ned
     
    #6 RC-Pilot232, Jul 10, 2017
  7. bisco

    bisco cookie crumbler

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    12.8v per fred h in post #4?
     
    #7 bisco, Jul 10, 2017
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  8. edthefox5

    edthefox5 Senior Member

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    How come you can mod power supplies but you don't know what voltage it takes to charge a 12 volt battery?
    That's a 5 second google if you really don't know.

    It takes 13.8 volts. Either at trickle 2 amp or fast charge 4 amp.
     
    #8 edthefox5, Jul 10, 2017
  9. RC-Pilot232

    RC-Pilot232 Junior Member

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    Per the original post, I am not trying to charge the battery. I want to maintain it. While the
    car is ON in NOT READY MODE, and I am messing around with Techstream, for a few hours. Which will deplete the HV battery. Which I do not want depleted. And I have found my answer elsewhere, 13.8 volts.

    Thank You,
    Ned
     
    #9 RC-Pilot232, Jul 10, 2017
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    What I don't get: a smart charger will do the job, and is good to have around, but that's not good enough? (n)
     
    #10 Mendel Leisk, Jul 10, 2017
  11. Kevin_Denver

    Kevin_Denver Active Member

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    Ned,

    It's known that the 2nd gen Prius in IG-ON (foot off brake, power button twice) mode will draw about ~200-250W to drive all of the car's ECU's (with all accessories off - obviously if you have headlights or other things on this goes up). I'm not sure what is in ACC-ON mode (foot off brake, power button once), but it should be the same or lower. So to stay in ACC-ON mode continuously, you'd need minimum 20A; I'd go for at least 25 or 30A to be safe. Anything from 12.8 to 13.8V should work great. Your 13V, 65A power supply is ideal really.
     
    #11 Kevin_Denver, Jul 10, 2017
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  12. RC-Pilot232

    RC-Pilot232 Junior Member

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    Thanks Kevin, I will try at 13v & see if the HV batt gets drained.
    Next time I get some time off work that is.

    Ned
     
    #12 RC-Pilot232, Jul 10, 2017
  13. ChapmanF

    ChapmanF Senior Member

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    That's because you asked a trick question, and nobody noticed. ;)

    Nothing will happen to the HV battery, which is fully isolated in not-ready mode, and isn't charging anything.

    You already got answers about the minimum output needed to prevent the 12 volt battery depleting (i.e. anything higher than its own open-circuit voltage) and that's all there is to worry about.

    -Chap
     
    #13 ChapmanF, Jul 10, 2017
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  14. edthefox5

    edthefox5 Senior Member

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    Oh yeah 65 amps is very ideal.
     
    #14 edthefox5, Jul 10, 2017
  15. edthefox5

    edthefox5 Senior Member

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    You really don't understand anything about a 12 volt battery. Your only maintaining if it's at it's full 13.8 volts...fully charged. That's maintenance mode. Any other state below that voltage and it's charging.....it's drawing current.
     
    #15 edthefox5, Jul 10, 2017
  16. ChapmanF

    ChapmanF Senior Member

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    I wonder how long additional posts will keep piling up without noticing the question was about the HV battery.
     
    #16 ChapmanF, Jul 10, 2017
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  17. Fred_H

    Fred_H Misoversimplifier

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    Paraphrased:
    What is the the minimum voltage I need to prevent the 12v battery from being discharged, while the car is in ACC mode? (not in ready mode)
    again: 12.8 Volts

    [​IMG]
    https://priuschat.com/attachments/battery-soc-chart-jpg.59644/
     
    #17 Fred_H, Jul 11, 2017
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  18. dolj

    dolj Senior Member

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    If you read the question properly:
    The answer is the HV battery does not get depleted charging the 12 V battery when it is in ACC or IG-ON mode. So any trickle charger at 13.6 V @ 2 A will do the job as current drain in either of those modes will be minimal while playing with Techstream.
     
    #18 dolj, Jul 11, 2017
  19. bisco

    bisco cookie crumbler

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    was this one of those 'when did you stop beating your wife?' questions?(n)
     
    #19 bisco, Jul 11, 2017
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  20. Kevin_Denver

    Kevin_Denver Active Member

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    Well at least it wasn't another: "Go get your codes read" repeated x100 threads.:eek:
     
    #20 Kevin_Denver, Jul 11, 2017
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