I’m building a molicel p42a 21700 pack with 13s6p configuration. These cells should be comfortable putting out 20A each, for 120A combined current output without getting too warm. I’m probably only going to use 30A most of the time on a tow boogie build, but it might be handy for towing. I’m going to stack it in a 13x6 grid with square cell spacers, to allow for short connections between parallel rows.
I’ll put a JBD BMS on for charge only, so that it doesn’t limit output. I’ll put fuses on each balance lead where it connects to the cell -ve terminal, and route the BMS cables without crossing them. There will be a big 200A fuse on the output.
I’m debating whether to solder the pack or get a k weld setup. If I solder it, I’ll use a TS100 iron which has pretty good grunt, and I’ll solder a thinner copper solid core wire along the parallel direction, with short pieces of say 16 AWG copper to make series connections for each cell. I won’t bother with individual cell fusing, ala flightjunkie, but his build has inspired me to consider soldering the whole pack - although being more time intensive.
If I decided to go with a spot welder, I’m not keen on using typical strips of nickel, as they won’t be ideal for 20A per cell. I’m interested in spot welding with a sandwich of nickel steel strips 0.1mm over copper 0.1mm sheet, but this will likely require a serious k weld power source. Another option might be to use wide nickel sheet, as the tidy looking kayak31 pics above.
I am stumped about the best power source to use for a k weld, if I did go that way rather than soldering. Not that keen on a lipo that will be stressed and expand due to the heavy load of k weld. A super capacitor setup looks expensive.