# DC welder. EV component?



## Gashog (Dec 23, 2007)

I have a couple of welders in various states of disrepair and since I got my nice Bobcat, I was tossing around the idea of using one of the others to power my moms car. It would make one big motor! Also might not be a bad thing to use in a hybrid. They usually put out about 70 volts open circuit DC at about 200+ Amps. My welders are all about the same power (from 200-250A) and all use an Onan 16-18hp engine. That's pretty good output for that little hp right? Get a little diesel to spin it and vouala! 100mpg right? 
Anyway....thoughts?

Also, one of my junkers will do AC. That bumps it up to 310Amps.

Edit: I might be way off on the output. I think my Bobcat is rated a 30V so at 70V, it would be more then twice the Amps. Not sure.


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## mattW (Sep 14, 2007)

18hp is 13.5kw but 70V @ 200 amps is 14kW so your mechanical to electrical conversion it greater than 100% efficient woo! hooray for breaking the laws of physics. I know they were just guesstimates (and the open circuit voltage will drop under load) but it sounds like it has a decent efficiency. Could you test the voltage with something like a big heating element off a stove between the terminals? Is the welder a generator or rectifier or just a DC-DC converter or what?


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## Gashog (Dec 23, 2007)

mattW said:


> 18hp is 13.5kw but 70V @ 200 amps is 14kW so your mechanical to electrical conversion it greater than 100% efficient woo! hooray for breaking the laws of physics. I know they were just guesstimates (and the open circuit voltage will drop under load) but it sounds like it has a decent efficiency. Could you test the voltage with something like a big heating element off a stove between the terminals? Is the welder a generator or rectifier or just a DC-DC converter or what?


I looked at schematics for my Bobcat and it looks like an alternator.


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## aeroscott (Jan 5, 2008)

I was just looking at one at the bone yard .it has wound rotor so would be good for low end torque. the wire looks big so 70 or so volts.would need to tap for 3 phase? it has 230 volt output,welding has 3 legs so 3 phase I think .2 of these end to end would be hot . im working with Tom on diy motor controller that can be made 3 phase or DC with small changes.i wish it had higher voltage but I rewound a alternator before not super hard. the shaft looks long and big for moding.not much frame on the motor .all said its looks like it would be good.


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## peggus (Feb 18, 2008)

Gashog said:


> ...
> They usually put out about 70 volts open circuit DC at about 200+ Amps.
> ...



70V DC OCV at 200 Amp is kind of a contradiction don't you think?


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## aeroscott (Jan 5, 2008)

older welders that only run stick only or constant current were made with a large air gap (stator to rotter) which gives high voltage to start the arc and slopes to about 40 ish volts during the weld.Now with constant voltage for wire welding ( mig, flux core ) we want cc and cv plus ac power 120/240 volts about 35 amps or 8400 watts. many makes and models, how are they wound.


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## aeroscott (Jan 5, 2008)

cv runs about 40 volts max this is a welding limit not machine limit.


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## aeroscott (Jan 5, 2008)

just picked up the bobcat alternator today .it's about a 160 lbs.,16" long,9.75" dia., 1.5" dia. shaft, cast iron fan / coupling , open frame , 2 pole armature with slip rings. I'll take it by the motor shop a.s.a.p. for more imput. might be better to get a brush less for oil cooling. John Stubbe


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## aeroscott (Jan 5, 2008)

checked on the welder this morning .winding are complex ,the iron in the stator has a lot behind the slots ( good for high rpm) , there is a large gap in the slots , not so good but don't know why.


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## piotrsko (Dec 9, 2007)

my $.02 (usd)

Duty cycle? last I recollect, the duty cycle on a welder is less than 50 %, which means you can run it at: way less than 50 percent power all the time or 100% power half the time. and the power levels are incremental because there are cooling issues to deal with.


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## ww321q (Mar 28, 2008)

duty cycle is different for each welder . My Lindy mig is 100% at full power
 but most fall in the 40 to 60 % at full power............J.W.


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