All 4 battery boxes are welded up now. The last one with the extra corner in it was quite tricky again. Had to make whole constructions of wooden blocks to be able to support and keep them in place while welding. This one didn't turn out as good as the other boxes but it's still good enough.

Most important is that they're all done now. Just have to even out the welds on them all now and then I can finally continue with the next step for the battery boxes.

Meanwhile I also got something in the mail again. Had to search for a long time to find the right size for these and delivery took pretty long as well but I finally have them now and they fit perfectly.

They're all rubber vacuum caps. In the clamps for the batteries that I'll be making inside of the battery boxes there'll be quite a few rivet nuts to attach everything with bolts. Like here on my testplate.

Since these will be close to the batteries I don't want to take the risk of a short circuit. So on all rivet nuts I'll place one of these vacuum caps as isolation.

Fits perfectly as the inside diameter is slightly smaller than the outside diameter of the rivet nuts. So they will always stick on there which makes it a lot safer. And the rivet nuts will be really waterproof like this as well.