Welding off the Grid

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Welding off the Grid

Postby 470rigby » Sun Feb 28, 2010 9:38 am

I am looking for some advice on how to Weld when Grid Power is not an option.

My 3500W Inverter/Charger is not an option as a power source since I want to use the welder in remote locations, and frankly at $8.5K, I don't want to risk damaging it.

Of course, Generator/Welders are commonly available, but the prices are criminal.

I do have a 5.5kVA Honda Genset with AVR. No specs are forthcoming on the THD of the AC output, but I assume it is somewhere around 6%. Most appliances run quite happlily off it, except for the Digital Clock on the 'Fridge! I am getting mixed opinions from Welder dealers on Genset compatibility, both in AC Waveform requirements and KVA capability. Some of the new Inverter Stick Welders seem to be Genset compatible, but nobody seems keen to put it in writing specifically re my Genset, and I can't find anyone with actual experience with the Honda Alternator in welding applications. The Honda Genset is not a preferred option as power source though because it's weight (85 Kg) limits it's portability.

I have looked at other options including Automotive Alternator based units (Unipower/Mobi-Arc), but that means building a dedicated petrol motor driven system. This concept has some attractions though, in that the Unipower units would give the added benefit of having a high amperage Battery Charger and 2500W AC Power Supply (useful backup in the event that the Inverter/Charger goes down). But again, I can't find anyone with experience with these units?

Your thoughts would be appreciated.
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Re: Welding off the Grid

Postby KarenS » Sun Feb 28, 2010 11:32 pm

Gordon-Loomberah does welding off-grid - perhaps search the board, or PM him.
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Re: Welding off the Grid

Postby GeoffHammond » Wed Mar 03, 2010 8:24 am

Yeah.... I've read that Gordon does weld off his solar system. (Is there anything he *doesn't* do with his lecky??)

Before I bought a petrol chainsaw and became a Local, I used a mate's 2400W electric chainsaw a couple of times. I only did so on bright sunny days and it worked fine. Having said that, I am reluctant to buy a welder and then find out that, for some reason, ummm... The peak current I get out of my panels (with a tail-wind) is about 55Amps. I figure that if I am welding at 2.4kW, I would need to find another 50Amps from the batteries, which would - I guess - be okay if I wasn't doing long runs.

My current solution is to befriend someone nearby who welds and enjoys home-brew. If I was going to a lot of it, I would probably look at the dedicated welder gen-sets, but I would have to be doing a *LOT* of it.

Edit: Welder gen-set f'rinstance: http://www.dunlite.com.au/store/listIte ... tegory=110
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Re: Welding off the Grid

Postby Gordon-Loomberah » Wed Mar 03, 2010 10:00 am

I MIG weld using my Latronics 3kW inverter quite often, in fact I'll be starting on a large steel ramp for the house in the next week or 2. I generally use the 4kW setting, which the panels/WTG/batteries have no trouble keeping up with in good charging weather. The duty cycle of the inverter is greater than that of the welder at the 4kW setting, so if I get a bit carried away with too many long weld runs in a short period, it is the welder's thermal cutout that activates, rather than the inverter's. In the past I have welded using a Selectronics 2.5kW inverter and it has also performed very well with the large loads.

EDIT, the continuous output of the Selectronics inverter is 1800W.

I generally try to avoid drinking my home brew before welding though :lol:

I have done a bit of welding at 24VDC directly off the batteries in the past too. It works best with a 4mm stick, (and obviously, thick section steel) but it does quite a nice job. I have welded a couple of large WTG towers this way.
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Re: Welding off the Grid

Postby ratcat » Sat May 29, 2010 3:21 pm

I have an 5.5 KVA genset (Honda) and have used my small welder with it quite a few times without a problem, that was before we finished our solar system. Cant hurt to give it a go... well it can but its easy to replace the few electronic components which I think from memory is a diode and a couple of other parts. You should keep spares available just in case.
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Re: Welding off the Grid

Postby 470rigby » Mon May 31, 2010 11:05 am

ratcat wrote:I have an 5.5 KVA genset (Honda) and have used my small welder .


Hi ratcat,

Thanks for the info.
I have the same Genset but am unsure what maximum amperage it will handle from my Elletro Inverter Stick Welder to allow me to weld thicker steel sections. What type of welder do you have and what Amp settings do you you use?

Another issue with the Honda Genset is portability; it is just to heavy to lug around.

I would also dearly like to run a MIG so that I could weld thin wall RHS, but can't find one that will run on the Honda.
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Re: Welding off the Grid

Postby Gordon-Loomberah » Mon May 31, 2010 12:48 pm

470rigby wrote:I would also dearly like to run a MIG so that I could weld thin wall RHS, but can't find one that will run on the Honda.


My UNIMIG 165 manual says minimum suggested genset size is 9kVA, so it would need to be quite a small welder to run from a 5.5kVA genset at full power satisfactorily.... although I'd say it would work at lower power settings.
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Re: Welding off the Grid

Postby 470rigby » Mon May 31, 2010 5:16 pm

Gordon-Loomberah wrote:My UNIMIG 165 manual says minimum suggested genset size is 9kVA, so it would need to be quite a small welder to run from a 5.5kVA genset at full power satisfactorily.... although I'd say it would work at lower power settings.


Hi Gordon,
The problem is that various Welders run at different Power Factors and have preferences for AC waveform type. Even with non-inverter Gensets, Total Harmonic Distortion (THD) is an issue re compatibity with welders. But even getting THD specs on Gensets is problematic! Some of the newer Inverter Stick Welders are rated as "Generator Compatible"; presumably OK to use with square wave Gensets, but when you ask a dealer what that really means, you get that "what sort of a smart-arse are you look"! For some reason that nobody can explain, MIG technology doesn't seem to lend itself to running on "dirty" AC.

All a bit of a mystery really!
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Re: Welding off the Grid

Postby phmorrow » Mon Oct 25, 2010 10:08 pm

For those interested in welding, I have a 24V truck alternator set up with a 3 HP Honda motor.

I used it to charge my 24V battery set on my solar system before going to a larger system. The motor is too small for the job. The alternator can put out 50A at 24V, ie 1200W but the losses mean that it needs about 4.5 horsepower. to run it. Many of you would have one of these sitting around on a defunct pump unit. I set it up with a direct coupling to the motor so it should run at 3000 rpm which is the norm for a small Honda. So any motor with a bare output shaft would fit. I avoided V belts because of their losses are considerable. So this system should provide all the power needed for welding in the field with a compact engine/alternator easily moved to wherever it is needed, or charging solar batteries. I will supply the book "Build Your Own Direct Charging Plant" by Robert Sharman with the unit. He goes into the complications of welding at some length (p55) including some warnings.

You will find that buying a second hand truck alternator is expensive so this almost new unit is cheap at $400.
Contact me via the forum.
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Re: Welding off the Grid

Postby Photon » Sun May 01, 2011 9:00 pm

could I weld off my 1000AH 24v batteries? should i disconnect the fm80 when welding or leave it connected?
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