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Thread: Question about ocv

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    Question about ocv

    OCV is obviously important when welding, so how is it that you can weld with a 12 volt battery that puts out about 13.6 volts? Is it because of the amperage available??
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    Re: Question about ocv

    As long as the welding voltage stays high enough, and enough amperage is available, the arc will stay lit.

    As I recall, people usually use two batteries at 24 volts to make it easier.
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    Re: Question about ocv

    The higher OCV will help strike an arc but once you have established a load/arc the OCV is on longer there... I never found one 12 volt battery enough for what I needed and always use 2 of them in series or a 6 volt and a 12 volt seems to works best for some of the thinner remote welds with my ready welder. Amps are key to welding but like anything power related it takes both volts and amps to make power

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    Re: Question about ocv

    I was curious because as of late there has been a lot of talk about OCV. Amperage would be controlled by arc length, correct?
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    Re: Question about ocv

    Quote Originally Posted by CAVEMANN View Post
    I was curious because as of late there has been a lot of talk about OCV. Amperage would be controlled by arc length, correct?
    Arc length is voltage, but amps would reduce as the arc lengthens in general.

    That's provided using a battery follows the same type volt/amp curve as a transformer machine.
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    Re: Question about ocv

    Ok, thanks guys. I've been watching ALASKAN BUSH PEOPLE and one of their current commercials where Matt is attempting to weld with a battery. I've never done it or seen it done but an old rancher friend used to talk about doing it in a pinch, actually there was 2 friends that talked about it, gonna give it a shot some day.
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    Re: Question about ocv

    Is it only the nature of magnetic transformers? no current on the secondary, voltage is high. Complete the circuit, voltage plummets to a point where magnetic field strength equals power measured in watts.


    Travis Field did a you tube video on voltage. He mentions the relation of ratio of volts to amps, totaling watts. A given level of heat requires a specific number of watts. He describes low voltage, high amperage being a digging arc. This is important vertical welding where the filler is deposited in a pocket with low voltage, or on the surface with high voltage. Low volt/ high amperage buries the molten filler in a hole, where it quickly freezes. high voltage/low amperage deposits on the surface where it freezes more slowly.

    I wonder if a big part of the great arc characteristics of Lincoln SA 200 welders is low voltage.

    Welders without voltage control can me manipulated with arc length. Short arc/ low amperage causes sticking. Short arc, high amperage gives lower voltage.

    Battery systems usually involve even numbers of batteries arranged for 36, or 24 volts output. Theoretically, battery welders should be great stick welders with good batteries, and enough of them. There is a very eccentric fellow in Rutland VT running around with an old pickup freighted with batteries, and welder lead. He is a talker!!!! I'd like to ask more, but can't spare a whole day.
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    Re: Question about ocv

    I have 2- 12v in series on my Hobart welder. Maybe I'll give it a try with my heavy duty jumpers and 1/8" 7018.
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    Re: Question about ocv

    Want to weld with batterys?
    2 choices, learn from someone who knows how to do it and will stand next to you as you try; OR wear a rubber suit like SCUBA divers do and a Full Helmet. Not a bad idea to have somebody standing by with a connected & pressurized water hose too.

    Yes, it can be done, BUT you damn well better know how to regulate the current the battery can deliver or you stand a good chance of turning the battery into a BOMB.

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    Re: Question about ocv

    Worthwhile reading on why dedicated stick machines – with their classic "drooper" volt-amp curves – are often easier to stick weld with than TIG machines that also do stick:

    https://www.millerwelds.com/resource...ining-purposes

    The article explains it a lot better than I ever could, but in general:

    When you want a lot of "dig" like with 6010, you want a machine that puts out more amps as the arc voltage decreases. This allows you to poke the rod into deep crevices (or gouge holes if you want) without sticking.

    When you want a more "buttery" arc like with 7018, you want a flatter volt-amp curve, so that the amperage doesn't change as much with changes in arc voltage (arc length). The advantage here is that the arc is more forgiving of changes in arc length, except when you get the arc length too short – which can cause sticking.

    On an engine drive welder like a SA-200 or my 251D, you can change "gears" (amperage ranges) which allow you to use power at a flatter, or steeper, portion of the V-A curve. On mine, and I believe most machines, when you want more dig, you want a higher "gear" and a lower "fine adjustment." When you want less dig and a more buttery arc (like for 7018) you would choose a lower gear and a higher "fine adjustment." An easy way to remember this is, when you're burning low-hy (low-hydrogen – 7018) you use "lo-hi" as in "low range, high fine adjustment." And vice-versa for a cellulosic rod where you might want more dig, as in a tight root where you want the keyhole of full penetration.

    On my Miller 251D, the "fine adjustment" changes the OCV from about 58 to 88VDC. This makes the machine want to stick 6010 more on startup (since OCV is lower) but the advantage is more dig and less "stickiness" once you get the arc going. On the other hand, with the fine adjustment turned up (like with 7018), the rod has less tendency to stick on startup (because OCV is higher), but more of a tendency to snuff out and stick if you get your arc length too short. But in the sweet spot, it gives a more buttery, less angry/digging/gouging arc.

    It's all a trade-off, but it's nice to have that level of adjustability in a non-iPhoned machine.
    Last edited by Kelvin; 08-26-2018 at 08:59 PM.
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    Re: Question about ocv


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    Re: Question about ocv

    Quote Originally Posted by Virgil5 View Post
    Want to weld with batterys?
    2 choices, learn from someone who knows how to do it and will stand next to you as you try; OR wear a rubber suit like SCUBA divers do and a Full Helmet. Not a bad idea to have somebody standing by with a connected & pressurized water hose too.

    Yes, it can be done, BUT you damn well better know how to regulate the current the battery can deliver or you stand a good chance of turning the battery into a BOMB.
    Yep, I have a great respect for batteries after having one blow up in my face many years ago. I just hate acid in general, I spent a total of about 17 years working in and around sulfuric acid plants, The last had drying towers that were in piss poor shape and allowing wets gasses to the blowers which were raining acid fumes and chunks everywhere, the blower was badly out of balance and we were monitoring it every 4 hours, we left the balancing equipment connected and closed up in a plastic bag, we went in wearing an acid proof suit , full face respirator and all skin protected, somehow I missed a spot and got a chunk of crap on my neck, I still pack a scar from that day, just nasty stuff.
    Last edited by CAVEMANN; 08-26-2018 at 08:55 PM.
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    Re: Question about ocv

    Quote Originally Posted by mla2ofus View Post
    I have 2- 12v in series on my Hobart welder. Maybe I'll give it a try with my heavy duty jumpers and 1/8" 7018.
    Mike
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    Re: Question about ocv

    Quote Originally Posted by Kelvin View Post
    Worthwhile reading on why dedicated stick machines – with their classic "drooper" volt-amp curves – are often easier to stick weld with than TIG machines that also do stick:

    https://www.millerwelds.com/resource...ining-purposes

    The article explains it a lot better than I ever could, but in general:

    When you want a lot of "dig" like with 6010, you want a machine that puts out more amps as the arc voltage decreases. This allows you to poke the rod into deep crevices (or gouge holes if you want) without sticking.

    When you want a more "buttery" arc like with 7018, you want a flatter volt-amp curve, so that the amperage doesn't change as much with changes in arc voltage (arc length). The advantage here is that the arc is more forgiving of changes in arc length, except when you get the arc length too short – which can cause sticking.

    On an engine drive welder like a SA-200 or my 251D, you can change "gears" (amperage ranges) which allow you to use power at a flatter, or steeper, portion of the V-A curve. On mine, and I believe most machines, when you want more dig, you want a higher "gear" and a lower "fine adjustment." When you want less dig and a more buttery arc (like for 7018) you would choose a lower gear and a higher "fine adjustment." An easy way to remember this is, when you're burning low-hy (low-hydrogen – 7018) you use "lo-hi" as in "low range, high fine adjustment." And vice-versa for a cellulosic rod where you might want more dig, as in a tight root where you want the keyhole of full penetration.

    On my Miller, the "fine adjustment" changes the OCV from about 58 to 88VDC. This makes the machine want to stick 6010 more on startup (since OCV is lower) but the advantage is more dig and less "stickiness" once you get the arc going. On the other hand, with the fine adjustment turned up (like with 7018), the rod has less tendency to stick on startup (because OCV is higher), but more of a tendency to snuff out and stick if you get your arc length too short. But in the sweet spot, it gives a more buttery, less angry/digging/gouging arc.

    It's all a trade-off, but it's nice to have that level of adjustability in a non-iPhoned machine.
    I'm unclear if all Lincoln DC only welders have the same set of controls, are they are only labeled different? Some have one dial labeled voltage. Others use the two dials, as range, and gear. In either case, the ratios of volts, and amps can be manipulated.

    An ignorant observation: Big horsepower welders have a more stable arc than underpowered air cooled.
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    Re: Question about ocv

    To go onto what Kelvin posted my old Hobart engine drives do as he posted. A higher "range" with a low fine adjustment gives a good and smooth arc while a lower "range" and higher fine adjustment gets a good digging arc. This I find is very versatile once gotten used to. Been years since I've welded with an SA-200 and was unfamiliar with the machine but am certain they are close parallels in welding performance. My six cylinder GB-318 is actually smoother in arc quality than my four cylinder G-258 machine. Both are DC commutator based machines and I attribute the arc characteristics to power pulses exerted through the crankshaft of the engine delivered to the welding portion. Both machines are very smooth in operation however.

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    Re: Question about ocv

    If I remember correctly, wasn't the "voltage" knob on those Lincolns regarded as a "fine" setting?
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    Re: Question about ocv

    Slob, what you are saying about crankshaft pulses makes perfect sense.
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    Re: Question about ocv

    I would expect a flywheel to compensate for piston surges. Still, three power strokes per revolution surely is better than one.I wonder if small engine welders lug, then accelerate to compensate. They surge, and aren't very stable.
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    Re: Question about ocv

    Quote Originally Posted by Willie B View Post
    I'm unclear if all Lincoln DC only welders have the same set of controls, are they are only labeled different? Some have one dial labeled voltage. Others use the two dials, as range, and gear. In either case, the ratios of volts, and amps can be manipulated.
    Pretty sure the labeling is just different. I think they work the same way (on both, the "fine adjustment" or "voltage" adjustment changes OCV and the "coarse" or "gear" detents change which part of the V-A curve you're operating in).

    Quote Originally Posted by Willie B View Post
    An ignorant observation: Big horsepower welders have a more stable arc than underpowered air cooled.
    ...except when it's an air-cooled diesel with lots of torque and a 3-phase setup...or that's my understanding.
    Last edited by Kelvin; 08-27-2018 at 07:32 AM.
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    Re: Question about ocv

    The flywheels DO help compensate for combustion pulses and maintain a "perceived" smoothness in the engine.
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    Re: Question about ocv

    Quote Originally Posted by CAVEMANN View Post
    The flywheels DO help compensate for combustion pulses and maintain a "perceived" smoothness in the engine.
    I have two six cylinder engine drives, and two four cylinder engine drives which are all Hobart but the arc is consistently a tad smoother in the six cylinder powered units; but not much. It's more you can actually "see" the melting area than feel it. It's kind of like a favorite writing pen. Part of it is I'm comfortable with my machines and certainly not saying one welds any better than the next. The quality or appearance of welds from any of the machines is very close if any difference at all. Don't think I could tell which machine did what afterward for sure.

    Even my former G-213 welder which was a two cylinder Wisconsin powered, commutator based unit, welded smooth but not near what the four, and six cylinder units are like.

    And of course these are just my observations.
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    Re: Question about ocv

    Quote Originally Posted by Kelvin View Post
    Pretty sure the labeling is just different. I think they work the same way (on both, the "fine adjustment" or "voltage" adjustment changes OCV and the "coarse" or "gear" detents change which part of the V-A curve you're operating in).



    ...except when it's an air-cooled diesel with lots of torque and a 3-phase setup...or that's my understanding.
    You sir are splitting hairs.
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    Re: Question about ocv

    Quote Originally Posted by Willie B View Post
    You sir are splitting hairs.
    My point was that I don't think you can compare a Trailblazer with a lawnmower engine to an air-cooled Deutz diesel. The weedeater-engined welder might be wimpy ... the diesel, not so much.

    Mine barely even notices when you strike the arc, even at 250A. Just because it's air-cooled doesn't mean it's wimpy.

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    Re: Question about ocv

    That's why I referred to high horsepower in the initial post. A better choice might have been heavy iron engines, but there might be an aluminum diesel.
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