You could also wet your fingers and stick them in there as a conducter.
I get that I am not the oldest hat in the woods here, however I have been in the world of electronics and engineering for like 20 years. I am here to assure you, using nickel is stupid. There are other options. I have *GREAT* success with my shitty vevor unit and a nickel/copper alloy that is pretty much industry standard for electronics exposed to high moisture content as in boats and road vehicles. It is a lil sparky when you hit it, but I am ok with little sparks. Just not the ones that turn into raging Battery fires.
If you are looking at that, odds on the spot welder you are gonna be working with will cap out just before that.15mm thickness, it will successfully hit a .13 all day long, but the .15 gets a little spotty, but with practice you can do it. The standard strips that are in use are 10mmx.15mm now it is a matter of how far beween cels. On an 18650 in square set spacing you are looking at about 20 mm center to center. However... that is *NOT* what you are gonna be doing. You are going to be running a line from one end of your set of cels to the other, and ods on you will lay these out like most the people say to.. and hang the wire off the end of the unit. So the distance covered oh say on a 3s7p cel (it is what I have on my desk sue me) would be 13.4cm so you are gonna need a bit of slack off that edge, call it an extra cm, you now have your maximum safe amperage conducted across that distance being a LOT thicker, and this has been argued around here
previously There is a chap on-line that made
this There is tonnes of resources out there for ya. Feel free to look at all of them and ultimately you are gonna do whatever it is you choose to. I just urge you to think twice and cut once. Or in other words, if you don't follow the math that is being laid out for you. Maybe you should just listen to the smarter people in the room.
Mind you, i am *NOT* saying I am one of them. I just have friends in the engineering world that I listen to, hell, I listen to the people here pretty assiduously. and they at least not that I know of, don't have engineering degrees. They just have 10-20 years experience playing with this stuff. My lame duck bum bought his first ebike in November. So far they have steered me right in playing with everything. The stuff I did not want to air in public was just how little I really knew about storage systems despite having installed and built like 200 of them (large scale corpo IT stuff) in the past 20 years. I am just happy we always had the sparkies do the final hookup, never thought of how close I came a couple times to bein an ex-retired soldier.