So I've been in to building and repairing battery packs for a number of years and the whole time I've been doing it I've been using solder and a solder iron because for the longest time no one made anything smaller than a big ol bench tool that cost hundreds of dollars to buy. Well finally someone came out with a portable Lithium powered spot welder for batteries! No I can try and make my own LiPo pack next! I put my cordless drill next to the sport welder for size comparison. This thing works like a champ and its only $60!