#UF20B

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.

How should I set it for 0.2 copper stacked with 0.12 nickel? My UF20B is at gear 80 and it still won't hold — not a single mark on the copper side. Do I need to add flux first?

The wires in v1 were too thin and got hot, so this time I went with 2S 21700 plus a 30A BMS, and double-layer nickel strip. This machine is seriously small — it sits in a corner of the bench without taking up space, recharges in a few seconds, and I welded 40 spots in a row without ever having to wait. Best part when it was done: not a single spot needed re-welding.

Four 4S packs, under 60 apiece. Welding was the easiest step; getting the balance lead wiring order right was what really strained my eyes. My palms were soaked with sweat on the first flight. Crashed once and broke a prop, but the pack came through fine. To anyone wanting to get into it: learn spot welding first, and everything after that is just saving money.

AWithZ UF20B spot welder | Solid welds on 32140, copper stays put. Still struggling with copper welds that won't hold? The AWithZ UF20B supercapacitor spot welder — output steady as a rock, not fussy about materials. Smart voltage regulation, no more cold welds, consistent weld spots. Punches through 0.15mm copper with ease; tear the copper strip and the weld stays. Hand-built Li-ion packs, done in one go. #32140Cells #AWithZSpotWelder #UF20B #Battery