RE: Making my own battery
I've built many packs over the years, never had a solder joint come apart, but that was back when there wasn't as good a selection of high capacity packs as there is now. used to be if you wanted a 1200-1400 pack you paid through the nose or you built it yourself.
I just picked up some eneloop batteries at Costco,, I'm going to build Ignition packs with them,, I have 100% confidence in my skill to do it right.
But I will say this, Building a RX pack is not something you want to do if you have to ask how. Might want to experiment with soldering wire bracing for landing gear and other RC building tasks before you dive into build RX packs.
Good luck