I build packs using these batteries, usually buying them on sale during the Xmas holidays. I simply put paste flux on solder braid [bought from Radio Shack] and the battery ends. I then tin the braid, and by getting a nice drop of solder on the end of the iron, I place a drop of solder onto the end of the battery. To attach soldered braid to battery end, I first heat the soldered braid and place it onto the drop of solder at the battery's end. My packs have never failed, and I have been using some packs for three seasons.