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Volts vs Amps.

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  • Volts vs Amps.

    on a Arc welding machine (DC) say 150-200amp range. Is it just the amps that are adjusted or also the volts? If the voltage is constant (or adjustable) what is the voltage?

    Just thinking about a project I might attempt

  • #2
    This is sort of a fun thought for me too.

    The inexpensive 800.00 and less welders use a transformer, rectifiers, capacitors and a coil. There is not a live electronic regulating circuit in them.
    The Stick welders use the arc length and transformer taps or a crank for regulating the output.

    Mig welders use the wire speed and varible transformer output to determine the current.

    The OCV "open circuit volts" tells a lot about a welder, stick and tig welders have a higher OCV about 60 to 90volts The higher volts is needed to extablish an arc easily. I had a real cheap SMAW that only had 45 volts on AC and it was always difficult to get an arc going.

    Mig has a lower OCV voltage about 25 to 30 volts. They use a skinny steel wire approx .030" that starts the arc by touching the base metal, melting off and starts arc, wire feeder pushes wire into base again and starts all over. Lower voltage works better in this case. Depending on the speed of the wire, will determine how much current is delivered. The expensive welders (which I do not own right now) have live electronic regulator circuits. In the case of CV, the welder adjusts the current to keep the voltage stable. In a CC welder, it adjusts the Voltage to keep the current stable.

    What kind of a project are you getting into?

    I hope I didn't give too much information.
    Last edited by Al T.; 11-08-2002, 12:34 PM.
    It's not an optical just looks like one


    • #3
      On most Stick welders you adjust the current only at the welder. The Voltage depends on your rod size and your arc length. Most of the time you are welding in the 18 volt range if you keep this arc length stable. Mig welders you set the voltage and the current is determanded by the wire dia and the speed of the wire.
      Dave Evans


      • #4
        Dave: so you're saying that stick welders are fixed somewhere around 18v and then the amperage is what's adjusted? a situation like that would be ideal for my project below.

        I've seen a couple articles on building welders out of old alternators. I was currious if I found one with big amps if 12v would be enough for if I'd have to modify it to run more volts also

        This would basically be 1) because it sounds like a fun project for old parts I have laying around. & 2) I have a Handler 135 that would be nice to have something that could weld slightly thicker metals on the rear occasion I need too.

        My thought would be if I used an old lawnmower engine to drive it I could have a gas driven welder and anything else I could hook up to it for cheap.

        Thanks. anymore thoughts are appreciated.
        Last edited by Bobby; 11-08-2002, 01:44 PM.


        • #5
          Here is an ebay page you might find interesting; the ready made "underhood" welder. Not near as much fun as DIY, but you might get some hints and ideas from their literature. I think the 150A version needed a 10-15 HP motor ... a little bigger than your standard push type lawnmower.


          Also, of possible interest, was a current ebay listing for a machine that would go 110V OR 220V, with greater welding capacity when hooked to 220V. Pix was too small to read the name, not cited in the add, but started with "S". Seems like a good compromise to the ever present debate of 110V or 220V machines.


          • #6
            Why not use 2 12volt batteries hooked in series to give 24 volts, you could use 1/8" to 1/4" rods if you get an arc started.
            It's not an optical just looks like one


            • #7
              welding with batteries can be done. I've seen it done several times. I'm curious to make a nice gas operated welder (if possible) . I've found several links on making generators out of lawnmowers and alts and several others about converting an alt to a welder so somehow combining the 2 I ought to be able to make this work


              • #8

                Let us know how it works out for you. Sounds like an interesting project. I just might try one.

                Arbo & Thor (The Junkyard Dog)
                The Next Loud Noise You Hear Is Me!


                • #9
                  I've welded with batteries in the field. It does work. It also tends to overheat the batteries and cause them to rapidly create too much hydrogen and explode. Blowing battery acid all over the place. Here's a link to making a DIY underhood welder out of an alternator. I know this works. I do not know, however how long the alternator will work. However, since they run under $50 for most GM ones I'm not overly concerned.


                  • #10
                    By using a heavy duty alternator, with the field coil jumped (unregulated) you can get up to 18 volts depending on the rpm.

                    There are lots of these variations in the 4x4 world. Premiere power welders is the one off the shelf setup that comes to mind. The pirate bb guys have alot of info there. Heres an example:

                    Let us know more about what your doin! PICS!



                    • #11
                      Bobby, I have done exactly what you have been contemplating. A homemade engine driven alternator welder, mine is built from 2 100A Caddy alts and 2 big Ford rectifiers and a 11 hp Briggs to drive them. It works quite well the OCV is around 80vdc I mainly use it to strike a 3/32 6013 it has decent bead characteristics. However the noise made from the engine is too loud to weld with long without earplugs (even with a muffler). Most of the parts are from the local Upull it junkyard so I dont have that much money in it but I do have a lot of time in it.

                      Also I have a big case Ford under the hood of my Chevy truck that drives off of my existing alt. both are quite handy and have used both a lot.
                      good luck

                      p.s. I think Pinhead might have some good information on this subject....


                      • #12
                        I was wondering if 2 alts might give a better performance than 1. How did you wire them? any types of diagrams. I'm rather ill-knowledged when it comes to much electricity type stuff but would always love to learn more.

                        Did you try to weld with just one alt? Do you feel that the 11hp is just enough or is more than enough?