To start with, there's a big "Alien Breaker" problem
Your two main panels (with the red main breakers) are distinctly Murray. Your colored-handle breakers are all Murray MM type.
There is no doubt this is a Murray panel (albeit an early one).
Unfortunately with many of these 1" wide panels, many breakers will seem to fit each other's panels. But they don't, actually. The bus stabs don't fit properly.
These early Murray panels are a real tangle. It normally doesn't work this way, but apparently the panel is cross-listed to accept both breakers no longer made, and also Eaton BR type breakers, but not modern Siemens breakers.
So the Siemens is an alien!
Wow, you need a seeing-eye dog to navigate these breaker compatibility issues.
The colored handle ones are fine; there's never been a reason to doubt old Murray breakers.
Most places stock Eaton BR. Home Depot certainly has plenty. No idea if the COVID-driven renovation boom has wiped out their supply; if so try local family lumberyards.
Your pool panel is also a hoary mess of alien breakers. Identify whether this is an Eaton BR or Square D panel, and replace all the alien breakers with the correct family of breakers. Eaton does make a breaker specifically for Square D panels, but BR ain't it. It is called Eaton CL and it's a bit hard to find. Breakers cost about $5 per handle, so a duplex costs $10 and a 2-pole cost $10.
The GE micro-panel can't have holes in it
Your GE panel is all GE breakers, so that's fine. However, it has holes in the cover and that's not allowed. You know that 40A GE breaker you just ripped out of the Murray panel? Stick it in this panel just to replace the 30A. One hole filled. Since the welder has been successfully powered through it all along, it clearly is usable for the welder; so that's that.
What's left is a 50A 2-pole half-width that can only mount "in the middle" like that. It must have, on both sides, either half-width 1-pole breakers, or listed GE blanking plates: you cannot have a hole!
I suspect a blanking plate fell out; that's why I don't like the things. They're hard to find, expensive and flimsy. I prefer actual breakers for hole-fillers; they are easy to find, cheap, solid, and useful.
The 50A breaker is functionally only a disconnect switch, since the 40A (now Murray) breaker in the main panel is the limiting factor on current. But it could power something. Or you could just junk it and replace it with another full-width 40A breaker.
OK, that cleans up our panels.
You can't run the charger in 50A mode from this panel
You can't run a load continuously at max power. Continuous loads must be derated to 80% of rating, which means on a 40A breaker, you can only plan to pull 32A actually.
Aligned with that rule, a "50A" electric vehicle charger only pulls 40A. But you can't run that continuously since the 40A feed breaker (and wires in the walls) are only good for 32A continuous.
Many chargers have a programmable mode which allows them to be set to match the available power. If you can program this charger to run at "40A mode" (32A actual draw rate), then you can simply plug it into one of the breakers in the barn sub-panel.
Otherwise you have 2 options, none pretty:
- Replace the charger with a "40A" (read: 32A) charger.
- Replace the feeder wire from this panel with 1 AWG aluminum or 3 AWG copper. This can be fed from up to a 100A breaker, but limited by the bus ampacity of the tiny GE micro-panel. (For my money, I'd tear the thing off the wall and replace it with a nice 24-space panel. No more running out of spaces. Ever!)
This house had a serious case of the latte's. The upgrader could've bought a 12-space panel, but instead bought that GE micro-panel and a couple of latté's. Could've bought a 18-space pool panel but instead got that 6 and a couple of latté's. And now you're painted into a corner. Don't repeat that mistake. I'm not saying overspend on everything, but panel spaces in particular are cheap. Go big: go crazy big. Make sure you never run out of spaces.