r/21700masterrace

Hello!

I am currently in the process of designing and building a fixed-wing FPV aircraft, and I have gotten to the point where I need battery packs.

I am a complete newbie when it comes to building battery packs, but I have quite some general electronics experience.

My goal with this aircraft is endurance, and that has narrowed it down to Li-Ion cells, probably 21700s for capacity. My motor is rated for 25A, so I figured I will have to build my pack to handle 30A at least accounting for servos, VTX, FC etc.

For now, I have not made any purchases related to the battery pack, and that is what I wanted to ask about:

• I've read that a spot welder is a requirement. I'm currently set on buying a kWeld, but if I can get away with something cheaper I'd gladly take recommendations.
• What should I use to connect the cells in order to handle 30+ amps while being spot weldable? Copper nickel sandwitch? Stacked nickel strips? Something else?
• BMS or no BMS? Many commercial RC LiPo packs seem to lack a BMS, is it fine if I build my pack without one as well? I have a balance charger and I will of course integrate balance leads.
• I am currently planning to use 21700 cells due to their availability and capacity, but many commercial RC packs use pouch cells. Should I prefer one over the other for DIY packs?

I will gladly take any other tips and/or recommendations!