From the pictures I get the sense this guy knows what he's doing. Sure his shop's a little dusty, and that fume extractor is maybe a little ghetto (better than my aquarium filter duct taped to a fan though).

It's hard to tell what those grey cells are being used in the pack, which is probably most important factor, but the construction of it appears solid. It's also evident from photo that he is disassembling a damaged pack. See the missing row of cells at the top, and corrosion on the bottom in this photo: https://149346090.v2.pressablecdn.com/wp-content/uploads/202...