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Can 2004 be jumped and run safely without a 12V battery?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by richard schumacher, Jun 12, 2023.

  1. richard schumacher

    richard schumacher shortbus driver

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    My Optima Yellowtop from 2008 is apparently finally suddenly dead. Is it safe to remove it and try to jumpstart and run the car without a 12V battery, to see whether there is some fault other than a dead 12V battery? I'd hate to speculatively buy a new 12V battery and then find out that there's some other problem. So two questions:
    1. Can the car be jumped and run normally without the 12V battery?
    2. Will it need to remain connected to the other (jumping) car, or can/should the jumping car be disconnected?
     
  2. ChapmanF

    ChapmanF Senior Member

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    That was a thing I did with my Gen 1 and it wasn't a problem.

    I've seen other people post that it won't work with a Gen 2, though I haven't tried it myself.

    One thing that might be going on: some people have graphed the system voltage while driving, and shown a graph where the DC/DC converter output is normally around 13.5 to 14.8 volts, but every so often takes a little dip down to the voltage of the battery itself. I believe what the car is doing there is using those brief moments to gauge the current state of the battery's charge.

    So a key thing to know there is: when the car does that, is it commanding the converter "hey, reduce your output to slightly less than battery voltage for a moment, so I can see what the battery voltage is", or is it saying "hey, turn your output off for a moment, so I can see what the battery voltage is"?

    If it's doing the second thing, and there's no battery there, the car's going to go totally suddenly dark when that happens.
     
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  3. richard schumacher

    richard schumacher shortbus driver

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    That would be bad :_> At this point it needs a new battery no matter what else might be wrong, so I won't risk it. Thanks!
     
  4. bisco

    bisco cookie crumbler

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    you could try it with a jump pack. you should replace the 15 year old battery anyway, unless you might not keep the car depending on repair cost
     
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  5. Brucetafer

    Brucetafer Member

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    I jumped mine and used a 12v dewalt battery to move it 50 feet for 2-3 minutes and it didn't kill anything except my battery lol..
     
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  6. sam spade 2

    sam spade 2 Senior Member

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    1. NO you should NOT do that. Leave the battery in place.
    2. NO, once started, the jump needs to be removed.

    THEN......are you REALLY saying that you are reluctant to believe that a FIFTEEN (15) year old battery is bad ???

    Current production of the Yellow tops aren't lasting anywhere near that long.
    You got lucky.
    Don't negate that good luck by making a mistake now.
    Get a new battery and don't do anything strange while replacing it.

    The new one should be fully charged BEFORE installing.
     
  7. Mendel Leisk

    Mendel Leisk Luddite

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    A lot don't do that, and it charges fine, with normal driving. A brand-new battery is quite resilient, and takes a charge readily, just from the car's charging system. Also, you could install it in a store parking lot in a pinch, drive it home, and put it on a charger (in car), if you want to be diligent.
     
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  8. sam spade 2

    sam spade 2 Senior Member

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    Part of that is because the "battery store" does it for them.
    A "mail order" battery which comes dry will have a charge of 50% or less.
    The point IS......that you should not blindly depend on the car to charge it up.
    AND the longer it stays low on charge, the more time will be taken off of it's life.

    Of course you can connect the cables in the car before you charge it.
    But people who do that and find that it actually works will be tempted to skip
    that step and it is NOT a good idea.

    That can result in the one or two posts a week from folks who say:
    I have an almost new battery and it has failed already.
     
  9. richard schumacher

    richard schumacher shortbus driver

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    I've installed a new Optima Yellowtop from O'Reilly and all is well. I asked Optima if they want the old one for a museum or an autopsy but got no reply. I'm glad that I kept the original Toyota negative cable, clamp, and vent fitting. (Anyone want an eLearnAid adapter kit for an Optima D51?)

    Thanks all!
     
    #9 richard schumacher, Jun 13, 2023
    Last edited: Jun 13, 2023
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  10. bisco

    bisco cookie crumbler

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    glad to hear it was just the battery, an amazing run! i doubt optima wants to promote that old tech, as their newer batteries have been greatly reduced in quality.
    all the best!
     
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  11. richard schumacher

    richard schumacher shortbus driver

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    Well that sucks. Maybe I should have bought the Toyota battery.

    [Well WTactualF? The posting software insists on correcting a spelling/grammatical error which I quite deliberately wanted to use. How does one shut off that feature?]
     
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  12. bisco

    bisco cookie crumbler

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    leave a space between letters?
     
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  13. fuzzy1

    fuzzy1 Senior Member

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    1. I have left the car running normally during a 12V battery change, and it worked fine during the time the battery was out. Not necessarily a best practice, but it typically works. I did it to preserve the volatile memories that would be erased when the car is off and the battery absent, though there are other ways to do this too.

    2. I'd disconnect as soon as practical, especially if the jumping car is not a Toyota Hybrid,. I'd also perform the jump with the jumping car turned off, to prevent potential conflicts between inverters or other 12V charging systems.
    Use alternate spellings or punctuation.

    Or just go with the flow. Certain 'corrections' are well enough known that many of us know what you meant. I sometimes even type in a modified version of the 'correction' the first time.
     
    #13 fuzzy1, Jun 13, 2023
    Last edited: Jun 13, 2023
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