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12v battery voltage?

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

  1. Andyprius1

    Andyprius1 Senior Member

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    That’s something Iv never liked, bending metal.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    I can barely bend copper tubing, lol. I was in the drafting office.

    Most places just an office, working for fabricators elsewhere, usually in the States. But I did work in one place that was directly connected to the fabrication plant; that was definitely the most interesting experience.
     
  3. Andyprius1

    Andyprius1 Senior Member

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    Actually a lot of electronic hobby enthusiast are constantly fabricating boards, circuitry etc but with more and more solid state wizardry that may falling by the wayside. Most of the factory boards are genuine works of art and should be displayed in museums. Now there’s a collection idea.
     
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  4. bisco

    bisco cookie crumbler

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    that's a pretty good drop, especially when you're in the 12.4 arena
     
  5. padroo

    padroo Senior Member

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    As long as your battery doesn't go below 12V I wouldn't worry about it. JMO
     
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  6. Andyprius1

    Andyprius1 Senior Member

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    That's 18/100 of ONE volt or less than two tenths of one volt, that's nothing. And Im sure in the next sojorn the converter will bring it up. considering that battery and its relevant converter are capable of putting out over 100 amps, on a steady basis, is pretty amazing!
     
  7. Andyprius1

    Andyprius1 Senior Member

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    Keep in mind that The definition of Voltage is Force, it is capable of current flow along with currents opponent, or ally RESISTANCE. So if your battery reading is anywhere between 12 and 13 its fine. Is also capable below these voltages as there is no starting motor involved.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah next time we're in similar scenario, I'll pop the hood when we pull in, avoid the need to open the passenger door.

    Oh I do not know: the lowest I've seen a battery on our Prius was after 18~ hours of having left a passenger door open. When I spotted it the battery was down to 11.9, and IIRC the car wouldn't even boot.

    I'm not that cavalier with battery voltage: anytime it drops below 12.5 and stubbornly returns there within a day or two of recharge, I would slate it for replacement.
     
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  9. Andyprius1

    Andyprius1 Senior Member

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  10. Andyprius1

    Andyprius1 Senior Member

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    I agree, I said that in my post. However, if there is actually a problem, one may want to do the Battery and converter test. Or have the Dealer do it.
     
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  11. jerrymildred

    jerrymildred Senior Member

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    My '05 was still starting at about 8.5 volts. Which really surprised me.
     
    #91 jerrymildred, Jan 14, 2019
    Last edited: Jan 14, 2019
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  12. Andyprius1

    Andyprius1 Senior Member

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    “starting” ? I hate it when a car stares at me! That’s amazing. Don’t be so cheap, let that current flow.....
     
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  13. jerrymildred

    jerrymildred Senior Member

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    Typo fixed. Thanks. Reminds me of the signature line a member used on a motorcycle forum I used to frequent: "Never anthropomorphize your motorcycle. They hate it when you do that." :D
     
  14. Andyprius1

    Andyprius1 Senior Member

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    I never did talk to or pet my motorcycles, I used to curse them out a lot.
     
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  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Drove yesterday, and getting back I did pop the hood release, checked this morning:

    12.99 volts, prior to opening driver's door
    12.67, after opening driver's door

    I swear cars (and bikes) know, when if ditch them in a trade-in. It's painful to look back, see them forlorn on the dealership lot. :cry:
     
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  16. ChapmanF

    ChapmanF Senior Member

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    I could start my Gen 1 down to about 8 volts or a bit lower, if I pulled the ABS relays first so the hydraulic pump wasn't the first thing to come on and tank the voltage.

    Below 7 it was pretty much hopeless though.

    Imagine my surprise finding I could bend rigid steel conduit! (Using a conduit bender, of course.)
     
  17. Andyprius1

    Andyprius1 Senior Member

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    8 Volts, that’s amazing!
     
  18. jerrymildred

    jerrymildred Senior Member

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    I've mentioned several times that the battery on my '05 was still starting up the vehicle at about 8 volts.
     
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  19. ChapmanF

    ChapmanF Senior Member

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    When you consider that the ECUs are likely using 5 volt logic circuitry, and contain their own regulators to produce a stable 5 from whatever's coming in, it's not really that amazing. The trick is to shed the biggest loads like the brake pump that might otherwise pull the open-circuit voltage even lower before the hybrid system comes online. Once the converter's online, you've got your 13 or 14 volts and you're off to the races.

    Some of the ECUs (the skid ECU, and the transmission control ECU in the post-Gen 1 models that have electric park, at any rate) do have some DTCs they will log if they saw input voltage below 9 or so. Once the battery's charged again, you can just say "yup, that happened" and clear those codes.
     
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  20. jerrymildred

    jerrymildred Senior Member

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    Speaking of the big load of the brake pump:
    The 12V on my PiP shows about 12.8V at rest. If I get in quickly and power it up before the brake pump makes pressure and stops, I can hear the pump speed up when the hybrid system comes alive. That boost from the DC/DC converter makes quite a difference.
     
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