I'm trying to use a small welder in my shed. The welder doesn't work with a modified sine wave so I switched to a pure sine wave at 5000w 12v. The welder starts and sounds good but does not weld. Just get an overload signal on the inverter. The instructions state that if your device comes with more than two leads (1 positive and 1 negative), you must use all of them. I had 2 pieces of the 4th caliber. No chance! Nothing done. I ended up upgrading the cables to 0000 gauge (4/0) and adding four more batteries (8 total) to get the welder working.