I am trying to build a 6S2P pack with BAK N18650CNP cells (ordered from liionwholesale.com). These are rated for 30A continuous discharge, but I only plan on drawing 15A from each individual cell for a total of 30A across the 2P packs, and maybe a few short current spikes up to 50A from the entire pack.
I previously made such a 6S2P pack by soldering together the cells using 14AWG wire, and the pack worked fine for about a year. I’m now experiencing serious voltage sag issues with that old pack, so I now want to build a new pack by spot-welding together some new cells.
The problem is that I’m using a spot welder which can only handle up to 0.12mm nickel strip. I chose to use 0.1mm x 9mm nickel strip, which seems like it can only reasonably handle ~8.5A for extended periods of time, with bursts up to ~11A. I saw online that it’s not a good idea to stack nickel strips when spot welding, since nickel-nickel adhesion is poor. I also considered soldering wires onto the nickel strips after spot welding, but that defeats the purpose of spot welding since a lot of heat will be transferred to the cells upon soldering, and the whole purpose of spot welding is to avoid heating up the cells.
What have other people been doing to connect high-current capable cells when building 18650 packs?