Making sparks

I started spot welding the batteries. I'm using nickel-plated steel soldered to copper bus bars. I definitely like the square plastic pattern much more than the hexagonal RTV bonded cells. The plastic squares are just much more solid.  The plastic also gives some nice standoff for the bus bar to protect the cells from solder heat.  I used wooden sticks on the hexagonal to achieve the same. 

Finally, welding is very participants about the metals.  Aluminum and copper don't weld with settings on my spot welder.  Too low and nothing bonds, too high and it just obliterates the nickel strips.  I know they can weld, just need to find out how.