So soldering the 8AWG cable to the nickel strip, and then spot welding it to the battery was a bit of a headache. I had to, just like with the rest of the battery, solder several strips on top of each other, one after the other (as the spot welder can not spot weld more than one strip at a time) to have enough material for the 300 Amps that are going to flow through it.
This was sort of difficult, as soldering the 8AWG Silicone Wire to the bunch of strips was required first, to avoid destroying the cells with a hot soldering iron.
Here’s a picture of the result. I was not happy with it, so I tore it apart again (picture was taken after I tore it apart)
what I will do now is a build a bus bar with a flat piece of copper, to which I will attach the nickel strips by clamping them down with screws.