Welding off the Grid

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Re: Welding off the Grid

Postby Gordon-Loomberah » Sun May 01, 2011 9:31 pm

Yes. I've been welding off my current 840AH 24V batteries quite a lot recently, with a Latronics 4kW inverter and no problems, with FM80 still connected. You really want the charging to continue while welding if you can.

One slight problem you might encounter is this: I have found that when the battery voltage was a bit low with my previous 8yo batteries, ie when it is cloudy and the voltage gets down to 21 or 22 during welding with ~4kW or so load and not much charging, the FM80 display becomes garbled. If you try and reset it by turning the power (from batteries) off and on again, you lose the data for that day up to that time. If you leave it until the following morning (I assume just until after midnight) and reset it, the data is not lost and appears in the log as usual.
Apparently there is a fix for this, Outback techs in the US have told me, but the OB techs in Oz dont seem to know about it last I enquired, so I have not done anything about it. Its only been a very rare occurrence anyway, and I've worked out how not to lose the data from the log.
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Re: Welding off the Grid

Postby Photon » Mon May 02, 2011 7:08 am

So for welding directly off the batteries should be ok with the FM80 connected?

I would like to buy a mig welder that will work of my existing inverter. Would such a welder exist?

Specs for my inverter are:

TOTAL APPLIANCE RATING At 30 °C
Continuous: 1800W
30 Minute rating: 2700W
5 Minute rating: 3800W
1 Minute rating: 5000W
Surge rating: 6000W
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Re: Welding off the Grid

Postby Gordon-Loomberah » Mon May 02, 2011 11:13 am

Photon wrote:So for welding directly off the batteries should be ok with the FM80 connected?


Oh, I didnt realise you meant welding directly from the batteries... but I have done that before with success- 4mm rods worked best- a very nice way to weld actually. I only did that before I had the FM80 though, so cant comment on how it would perform, but I see no reason for there to be a problem.

I would like to buy a mig welder that will work of my existing inverter. Would such a welder exist?

Specs for my inverter are:

TOTAL APPLIANCE RATING At 30 °C
Continuous: 1800W
30 Minute rating: 2700W
5 Minute rating: 3800W
1 Minute rating: 5000W
Surge rating: 6000W


hmm, that sounds exactly like the specs on my old Selectronics (SE or SA22? from memory), it's stored away in a box as a spare in case of lightning damage to the 4kW Latronics inverter I now use.

A small MIG will work quite happily on that inverter, I did lots of welding with my Selectronics inverter and a 160A MIG.

The old welder which I acquired 2nd hand, eventually died after about 20 years of use, and these days I use a UNI-MIG 165- DC MIG welding is very nice. I'll look back through my data logger details and see if I can find some days when I was welding, so you can see what the FM80 and battery volts were doing.
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Re: Welding off the Grid

Postby Gordon-Loomberah » Mon May 02, 2011 1:31 pm

OK, here is a plot of what my system was doing during welding of RHS to pipe for the bars on top of the straw bale walls on the new chook house the other day, zoomed into 5 minutes of tacking and longer run action so you can more easily see the plots, which become a bit overcrowded when viewing longer periods with lots of activity at this resolution.
Green scale refers to the grey plot, which is the output current from 2 arrays added together. FM80 was in the absorb stage when I started earlier in the morning, but drops into bulk when the current draw drops the battery voltage. You can see the battery voltage recovers quite quickly and then the current starts to drop again at the constant absorb voltage, ~29.8V (cool morning so temp compensation of +0.2V over the usual 29.6V @25C).

welding20110422.gif
click to de-fuzz


Peak power use during this 5 min period was just over 5kW, and just under half of that was coming from the PV panels at the time. There were a few small clouds occasionally passing over the sun too, indicated by dips in the grey plot, when the voltage was below absorb level.
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Re: Welding off the Grid

Postby Photon » Mon May 02, 2011 2:10 pm

Phenomenal response Gordon, thanks!
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Re: Welding off the Grid

Postby shashmem » Thu Dec 20, 2012 9:55 pm

Hello
I was toying with the idea of solar powered welders and came across this post. The general process of DC arc welding is to step down the utlility mains supply to about 20 volt dc with an OCV enough to initiate an arc. A medium power spec would be with a weld current of about 100 amps. So electrically speaking a 2Kw source should do.
A solar panel array could be wired to give 2 to 3 Kw at 24 volt. I reckon a series buck converter could be designed to provide a constant current source. The entire design should be relatively simpler than an Ac / Dc inverter. The up side is that the power source is pure DC and hence would give a clean weld without the ripple ( associated with Ac/Dc Converters.) A small power step up converter could be used to provide the required OCV.
The down side is that solar panels are still frightfully expensive, which could come down to realistic levels in the future. There is also a practical difficulty in getting a consistent clear sky when we would want to weld. However this concept seems exciting for remote areas and low carbon footprint.
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Re: Welding off the Grid

Postby Privatteer » Fri Dec 21, 2012 11:10 pm

Have you considered a basic "buzz box" aka AC stick welder?
Still got a 30 year old 10amp classic in the shed that has seem much use on a generator. Just need to disable the idle mode on the genset if possible.
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Re: Welding off the Grid

Postby shashmem » Sat Dec 22, 2012 6:07 pm

I am assuming that you mean disable the genset during idle weld time. I have come across "energy saver" for welding machines some time back. This is basically a device that would sense idle current and shut down the weld machine if the idle current persists for a specified time duration. Hence the no load power is saved in between welds. To switch on the welder, the weld tip is touched to the ground and the power is restored to the machine.
The 'energy saver" can be wired to switch off a genset, however, switching on would require some clever electrical logic.
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Re: Welding off the Grid

Postby Privatteer » Sat Dec 22, 2012 6:30 pm

Was referring to the genset idle mode.
Depending on genset of course but the 2 I had in the past the volts would sag with the sudden load as you started the arc if it was idling. The drop would make it very hard to maintain an arc until the genset caught up.

The last Honda I had I extended the idle/non idle switch on cable to be on the welder handset.
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Re: Welding off the Grid

Postby lantern » Sat Dec 29, 2012 11:21 am

A 24V battery will strike an arc without any problems.
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