I'm not melting batteries from drawing an arc, if that's what you're saying. I'm melting batteries because I'm running a hybrid on .09 builds. You do realize that the connections on the battery itself is not copper so you'll never have perfect conductivity. The SS people use to manufacture attys is usually mixed, same with most every metal used for APVs. They're alloys, like 302, 311, etc. By the way you'll never get your copper hot enough to emit toxic fumes, I do it all the time when I design 3 phase power to large commercial buildings.
to that post, donnt really think the o.p knows exactly what is going on here