It's been a hectic few months since I started this thread, but I finally got back around to finishing the cart build.
I stayed with the EG4 3KW for the inverter but went with an EG4 Lifepower4 for the battery. It doesn't have the built in heater but I don't see that being a problem where it's going to live. It saved a few hundred dollars plus it matches the inverter. Too bad the logo is upside down but not a lot of choice on that. I ended up turning it around so if you lay the cart down on it's back the battery is still in a functional orientation.
Here's the finished build -
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I fabricated a battery box and welded it to the base of the cart, and a battery hold-down to keep it from flopping around.
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Next I fabricated a "plug plate" out of a piece of sheet metal to mount the outlet box, 20A AC breaker, and the male AC plug for AC In.
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I welded the plate to the cart but the rest of the stuff I just bolted. By the way, I had a discussion with a couple of y'all about MIG welders. I ended up going with an Eastwood 180 based on the reviews and warranty. Picked up a Lotos plasma cutter while I was in the buying frenzy. I didn't really need the latter for this project but I have some more projects on the board where it will come in handy. So far I'm pretty happy with the Eastwood.
Painted it all up so it wouldn't be quite as ugly.
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From there is was just put it all together and do the setup on the inverter. Easy peasy. Here's a front and back view where you can see the plug for the AC In and the back part of the battery hold down from the back.
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It turned into more work than I anticipated, what with the fabrication and figuring some of that out, but it wasn't bad. I tested it with a few power tools. I think I'll hook up the MIG in 120v mode and see how well it handles it. It's not nearly as pretty and doesn't have some of the bells and whistles but something equivalent in a factory built portable is something like $4k to $5k. I think my daughter and her husband are gonna like it.
If I was going to do it over again I might do it on one of the four wheel carts to make it a little less gangly, but then it would take more room to store so maybe not.