I was OFF-GRID charging my ElecTrak the other day. Worked pretty good.
Today, I was using the shop vac to clean out an old tool box. There was a cloth liner that I was cleaning off. This of course pulls a lot more amps when the whole end of the vac hose is covered.
The power went out. I thought I blew a breaker. That's when I remembered that I was off-grid and was running the vac from batteries!
The UPS had shut itself down. The cable from the batteries to the UPS was warm. I had never run such a high load before. Time to upgrade the battery cables!
I gave it a minute, and then turned the UPS back on. Everything worked fine again.
The shop vac is the highest load I can think of, other than the welder (which I have NOT run on the UPS.)
Also, all I have to do right now to go from the UPS to the grid and back is to flip one breaker off, and the other one on.
If I have any issues with the UPS, it takes about 2 seconds to go back to grid power.