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48 vdc to 12 vdc step down converter

Discussion in 'Gen 2 Prius Accessories & Modifications' started by sundy58, Sep 12, 2022.

  1. sundy58

    sundy58 Junior Member

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    I have been looking around the forums but could not find anything about using the traction battery for 12 VDC accessories. I use this amazon.com/gp/product/B07S9KDSQ5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 on my golf cart. I wonder if there is a convenient place to pick 48 volts off the battery pack to connect to the step-down converter?
     
    #1 sundy58, Sep 12, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    The battery is made up of 7.2 volt (nominal) modules, so you could, in theory, tap across six or seven of them, and have a nominal 43.2 or 50.4 volts, maybe up to 60 volts or so at higher states of charge. You'd have to check whether the input specs of your converter could cover such a range.

    But it would be a pretty terrible idea. The car itself is only able to charge or discharge the battery using a series current through all of the modules, so any tap you added to drain only some of them would lead to battery imbalance that the car could do nothing about.

    There is a large DC to DC step-down converter built into the car, which will produce 12 volts for you whenever the READY light is on.
     
    #2 ChapmanF, Sep 12, 2022
  3. sundy58

    sundy58 Junior Member

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    Thanks for the reply. So I assume the DC to DC converter is how the accessory battery is charged?
     
    #3 sundy58, Sep 12, 2022
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Exactly.



    Now, 5 of those amazon converters in series, with the outputs paralleled? Hmmm...

    No, I won't be trying it myself.
     
    #4 Leadfoot J. McCoalroller, Sep 12, 2022
  5. sundy58

    sundy58 Junior Member

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    Ah yes, the Rube Goldberg edition. :)
     
    #5 sundy58, Sep 12, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    You can buy Gen 2 inverter assemblies for a song. Buy one, take just the DC/DC converter out (it's in the bottom), wire it up to run your accessories when the car isn't READY and the one up front's turned off?

    It's designed to be water-cooled. But then, it's designed to source 1400 watts (it's running the whole 12 volt system of the car while in READY, not just charging a battery). If you're only planning to run, say, 100 watts of accessories from it, you might get by with adding an ordinary heat sink, and not fussing with a water supply.

    No, I won't be trying it myself.
     
    #6 ChapmanF, Sep 12, 2022
  7. sundy58

    sundy58 Junior Member

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    So that will use the whole traction battery?
     
    #7 sundy58, Sep 12, 2022
  8. ChapmanF

    ChapmanF Senior Member

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    That's what it's there for. It's a 201.6 volt to 12 volt DC/DC converter.
     
    #8 ChapmanF, Sep 12, 2022
  9. sundy58

    sundy58 Junior Member

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    Ouch! They are not singing my tune. The cheapest I see is $150 on eBay.
     
    #9 sundy58, Sep 12, 2022
  10. sundy58

    sundy58 Junior Member

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    I can just add a security system battery. I like to have key off 12 VDC, it's from diving Fords my whole life. I might just put my battery jumper under the seat. I have the older version of this

    Arteck 800A Peak Portable Car Jump Starter

    The link insertion thing is not working for me right now.
     
    #10 sundy58, Sep 12, 2022
  11. ChapmanF

    ChapmanF Senior Member

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    But then, what would 5 of the amazon converters run you?

    Plus, you'd end up with all the rest of a Gen 2 inverter for your miscellaneous parts drawer.
     
    #11 ChapmanF, Sep 12, 2022
  12. sundy58

    sundy58 Junior Member

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    I have 185K on the old girl and have not done much beyond change the fluids and mess with the HID headlights. No extra parts for me.
     
    #12 sundy58, Sep 12, 2022
  13. ChapmanF

    ChapmanF Senior Member

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    WIth 14 big honkin' IGBTs and the like, you could be well on the way to building your time machine, or whatever.

    Just need to find a flux capacitor.
     
    #13 ChapmanF, Sep 12, 2022
  14. Rmay635703

    Rmay635703 Senior Member

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    I would strongly recommend against grabbing 48v of your nimh string to do this, unless you like bricking your car.
     
    #14 Rmay635703, Sep 12, 2022
  15. sundy58

    sundy58 Junior Member

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    1.21 Gigawatts.
     
    #15 sundy58, Sep 12, 2022
  16. Another

    Another Senior Member

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    Just wondering. How many kWh of energy do you need? How frequently? Wouldn’t a portable lithium battery pack be a better option and recharge it as needed, even off the Prius?
     
    #16 Another, Sep 14, 2022
    donbright likes this.
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