#FPV drones

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.

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.

Where's the next episode

Bilingual Chinese / English captions. Followers want to DIY FPV drone packs with a good discharge rate and long flight time, so first the prep: the pack body is 21700 or 18650 — the former has a higher discharge rate and more capacity but is bigger, choose to suit; fish paper; balance leads (pick a balance connector for however many S you need); power leads; copper and nickel strip; heat-shrink tubing for the outer protection. Tools: scissors, a soldering iron, and most important the spot welder — this AWithZ compact spot welder UF20B, which reaches welding condition in about 1 minute, much faster than the 20-plus minutes of other welders on the market; high power, up to 10.5kW, up to 1750A output; officially rated to weld 0.4mm nickel-plated steel strip, easily enough for drone packs; the welding pen has two modes: auto (press and it fires) and manual (pen trigger); preheat time selectable 1–10ms, 1 or 2 pulses selectable; screen reads 29°C. Assembly next episode. Comments: ‘it’s your fault, I bought the same one’; 18650s blow up easily, pouch cells are safer (creator replied); can pouch cells be used (creator: yes); only use it a few times a year so bought a P60F; does the welder go bang.

Creator TOP speaks to FPV pilots: field battery boxes, long-range packs and radio batteries are all built from cells, and he has already posted a welding tutorial, an internal-resistance test method, wiring diagrams and an open-source battery-box shell. The key piece of kit is a spot welder; this time he upgrades to the AWithZ UF20B and unboxes it while explaining how to use it. First he shows that a soldering iron struggles to tin a cell terminal, gives cold joints, and long heating is a safety risk, while the spot welder fixes it solid with a few small sparks. Nameplate: max output voltage 6V, max current 1750A, power 10.5kW. Feature-wise he likes the switchable trigger mode: in auto the weld fires as soon as the pen tips press down, in manual you can position first and then press the button to fire, which feels more assured; there are plenty of parameters (trigger time, multi-pulse) but he basically only uses the gear. Too high a gear burns through the strip, too low won’t hold; with 0.15mm nickel-plated steel strip folded double as the example: gear 1 is too shallow and pulls apart with one tug, gear 4 won’t pull apart but is shallow, gear 6 welds through to the back, gear 7 is thoroughly perfect — for 0.15, remember gear 7; gear 99 is for thicker material, up to 0.4mm. The settings menu has a page-by-page ‘experience sharing’ tutorial that is beginner-friendly. Closing: battery-shop bosses drive Ferraris, play with quads and never run short of pocket money, link in the showcase.

Field battery boxes, long-range packs and goggle batteries for FPV quads are all 21700 NMC inside; if you can build your own you save money for other parts. Tools: 21700 cells, a cell holder, nickel strip, copper strip, heat-shrink and a spot welder — a soldering iron can hardly get nickel strip to hold, and poor temperature control raises the internal resistance. The creator uses an AWithZ machine that welds nickel strip or 0.15mm copper strip with ease, max gear 99; the nickel + copper combination of about 0.3mm is usually around gear 25. First stick fish paper on the cell to insulate the outer rim; when welding, one pen presses the strip down while the other welds; on the other side, weld + and − separately — never weld them together; solder the balance lead and power lead to + and − (red positive, black negative); wrap in fibre tape, add flame-retardant foam, slide on heat-shrink, and a goggle battery is done. Reminder: lithium batteries are flammable and explosive, so take extra care while building.