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High Current Low Voltage Power Source

  1. Mar 29, 2009 #1
    I am in need of a high current low voltage DC power supply, around 8 volts and around 250 Amps would be ideal.

    A transformer could take a 110v 20a house line and using Pincoming = IPVP = Poutgoing = ISVS and
    get (110vx20a)/8v= and get 275a which is good.

    But how do I make that DC?

    I know that diode bridges are the norm for converting AC current to DC current but I have done a fair amount of browsing and found none that have the requirements that I need. I think the most I have seen are like 35 amp continuous and 400 amp surge.

    Anyone have any ideas?
     
  2. jcsd
  3. Mar 29, 2009 #2
    It would be helpful if you stated what you’re attempting to power, as well as the duration of time it must be continuously powered. Must you use 8 volts?
     
  4. Mar 29, 2009 #3
    Its for an electrolysis experiment and duration of time depends on amperage. I think a max of 10 volts needs to be established, if it is over 10 volts, other materials with a higher reduction potential could come out.

    http://www.cdupload.com/files/50887_syub2/curve.PNG [Broken]

    Anything under 50 amps will not be cost effective.
     
    Last edited by a moderator: May 4, 2017
  5. Mar 29, 2009 #4
  6. Mar 30, 2009 #5
    At these low voltages and high currents the best way to go is a switcher. Don't even try to build your own. Go on Ebay and look. I have seen supplies like this at reasonable costs.
     
  7. Mar 30, 2009 #6
    Do you have a price in mind? There's a lot of industrial power supplies out there that can do this no problem. However, they cost a small fortune and are very big and heavy.
     
  8. Mar 30, 2009 #7
    They also have efficiency levels high enough to pay for themselves after a long period of use in electroplating. The small ones (under 100A) aren't super expensive - roughly $3-$4/Amp, but are very efficient switching supplies with extremely stable output.
     
  9. Mar 30, 2009 #8
    I found this on eBay, it looks to be what I need and not too expensive either. The only thing that it needs is 220v...

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=400008509005 [Broken]
     
    Last edited by a moderator: May 4, 2017
  10. Feb 7, 2012 #9
    the voltage required for electrolysis is 1.24V only so wat i suggest u is that u connect 12V supply to 6 cells in series in this way u can avoid heat produced and generate more h2...the current drawn is dependent on the resistance of the cell u just need to take care of the voltage and heat generated...
     
    Last edited by a moderator: May 5, 2017
  11. Feb 8, 2012 #10
    That reminds me when I was 12 years old, with that cool new chemistry box, thinking "bah, who needs a battery, I'll get a faster electrolysis with a higher voltage!" and just dropping two wires into a cup of saline solution and then connecting them to a 110V power plug...

    ... ah, good times! :smile:
     
    Last edited: Feb 8, 2012
  12. Feb 8, 2012 #11
    Use a 1200 Watt ATX power supply. You'll get 12 volts, not 8 but even the really good ones can be had for under $300. You may have to plug it into a dummy motherboard to make it turn on but that's easy too. Tap your power off the lines that would go to the graphics cards.

    250 amps is asking too much. Even at 8 volts that's 2000 watts, too much for one standard US outlet to supply.
     
  13. Feb 9, 2012 #12

    Averagesupernova

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    So what's wrong with 220 volts? If you are not comfortable and capable enough to be working with 220 volt mains electricity then I don't think you should be messing with this project.
     
  14. Feb 11, 2012 #13

    NascentOxygen

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    Staff: Mentor

    As the original poster has not logged in since he asked about a high current supply, and that was 3 years ago, he may no longer be closely following this thread.

    Just wondering, what voltage are home electric welders?
     
  15. Feb 11, 2012 #14

    Averagesupernova

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    Oh jeez I hardly ever do that. I always look at the dates. Oh well...
     
  16. Feb 11, 2012 #15

    jim hardy

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    there are small ones that'll run from a 115volt 15 amp outlet and deliver sixty amps or so.

    the old standby cathedral shaped Lincoln 225 amp needs 230 volts.
    i run mine from a dryer oultlet.

    new microwave ovens have inverters - i'm curious if one could rewind the output transformer with a few turns of large wire.......
     
  17. Feb 12, 2012 #16

    NascentOxygen

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    But what is their open-circuit voltage? They are just a robust transformer, right? Or do electric welders include rectifiers?

    I'm thinking a welder might furnish the avid experimenter with a robust source of low voltage AC?
     
  18. Feb 12, 2012 #17

    jim hardy

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    Welders make perhaps seventy volts to strike the arc.
    Better ones have rectifiers and will say " DC "


    Hobbyists are using microwave oven transformers (aka MOT) to make low AC high current for spot welders. They remove the high voltage winding and replace it with a few turns of BIG wire.

    Four re-wound MOT's and something like these might make a versatile setup...
    http://www.ebay.com/itm/Bridge-Rect...935?pt=LH_DefaultDomain_0&hash=item1e67eb2a5f
    and there's usually 150 amp ones on Ebay.

    <<<WARNING>>> :: a microwave oven transformer with its high voltage winding still there is more dangerous than a handgun.
    NEVER enegize one until the high voltage winding is physically removed. And i mean removed with a hacksaw.
     
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