In case this is broken in the future: the video is basically a repair of a cheap solar float charger from Harbor Freight.
The positive lead and it’s solder pad had lifted away from the backing metal that the solar cells are built on. I couldn’t build up a new solder pad on the large piece of metal (Google searching indicates this normally takes a small spot welder or a special type of flux), but I had a roll of copper tape sitting around that ended up working well-enough.
So I stuck a small piece of copper tape to the larger metal surface, applied a small bit of solder, then reattached the positive wire. A test of continuity showed connection through whatever makes this tape stick. I vigorously applied hot glue, then tested it, and put it all back together.
It’s been a few weeks and this is still working fine.
