6S2P 21700 long-range pack, my entry for the #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.
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?
Converted a soldering iron to lithium power, pack welded with the UF20B — version 2
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.
Getting into FPV drones on a budget — welding my own packs cut the cost in half
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
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Before you browse
WeldWorld is an open platform for user sharing; content does not represent official advice.
Improper battery handling can cause fire, explosion, chemical burns and serious injury. Read the full AWithZ Safety & Usage Guidelines before any lithium battery assembly, spot welding or testing, and before using the community.
Community content is personal experience, not verified by AWithZ; where it conflicts with official documents, the official documents prevail.
Never apply someone else's settings directly; always start at a low level and test on scrap.
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Ep. 30 | One video teaches you how to build a 21700 pack — never worry about long-range battery againProjects519fpv
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