Interesting but why who the guy spot weld whole banks of batteries in parallel? Typical packs
are cells in series, with short nickel tab strips from + to - on the next cell.
I do like that he hot-glued the cells in place, keeps things lined up!
TIP: If you want to build replacement battery packs, it's a good idea
to put each cell thru a charge and discharge cycle, it's possible you'll get a new bad cell that
would spoil the entire pack from day one! Seen it happen!