https://forum.esk8.news/t/pictures-and-nothing-else/30415/19824?u=pecos
I like that the pos and neg have different shaped tabs, gonna steal that idea 
Ya, looking kinda rough. Post up in the battery builders thread and maybe the group think can help get the kinks worked out of your process there. Imho itās too many close calls and mistakes in too few welds to get all the way through a big ass battery like that without doing something that will waste your efforts or make it fail early.
Battery building pedantry 2, the new gloo boo baroo
Immediately i would suggest using something to mark the centers of the welds. I like to use a sharpie or similar round plastic implement to burnish a dent into the nickel - weld once on opposite sides where itās easy to see the target the go over with the backside of the sharpie like making a charcoal or pencil print or an engraving to emboss the cell ends through the nickel. If that doesnāt make sense hit up the battery builders thread and ill make a tutorial for ya.
On very thick nickel or copper i have made a jig to align the welds. If thats too complicated or just a one off arrangement a plastic ruler works well to create center lines too.