#21700 power-pack challenge

You only find out how many pitfalls there are once you build your own FPV drone packs: the negative side of tabless 21700s is really current-hungry — I had to push the UF20B to gear 52 to get full penetration. Paired it with a 40A BMS and measured every cell's internal resistance before welding; max spread 2mΩ. Flew three packs, and the shell wasn't hot when I touched it after landing. Happy. The recipe is attached to the project. Judges, please go easy on me.

Build a 21700 pack (≥4S) with any AWithZ spot welder and submit photos or video of the finished pack plus a recipe card. Judged on weld consistency, construction and safety (BMS, insulation). Prizes: 1st prize P60F ×1 · 2nd prize UF20B ×2 · 3rd prize welding-pin set ×10 Deadline: 2026-10-18 · 36 entries so far