RE: Making my own battery
FWIW, a good commercially made pack has the tabs welded to the cells. That gives you a good electrical connection that is extremely durable. Soldered packs have been known to have their joints fail due to vibration, and of course if you aren't a skilled solderer there's always the worry about getting a bad joint that will fail. IMO, battery packs are just not a place to try to save money. You can't save much and still have the same quality, and a DIY job can put you in the dirt in a hurry. If money is tight and you don't mind investing time to save it, get wrecked airframes for cheap or free and repair them, ditto for gummy swap meet engines that still have good compression. That plus buying quality electronics and a good computerized charger so you can take proper care of your batteries can make the hobby remarkably inexpensive for you.