Energy Matters Forums

[Gordon-Loomberah]

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.

[Photon]

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

[Gordon-Loomberah]

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.

[Gordon-Loomberah]

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).

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.

[Photon]

Phenomenal response Gordon, thanks!