So, I just got a new toy! A spot welder, and some 3500mAh 18650 cells and nickel strip. This is going to end up being a long stick, because it’s going inside a acrylic tube and I’m making another light-up cane.
I’m debating if I want to do 4s2p, or 8p, assuming I can fit all 8 cells in vertically along with controller, voltage buck (or boost) to 5v for the LED strips, BMS/PCB, fuse, power switch & charging port.
For 4s2p configuration, I got a BMS that can do balancing, and I’m trying to see if I should do that, or just do like the last one, all cells in parallel and keep it simple and easy. My reasoning to go for 4s2p is I can put in more power and charger quicker for the same amps (I’m figuring a 2a over a 3a rated small JST type connector). Fully charging might be a challenge at some points in time, if I want to use it multiple nights in a row in 8p, since I can only do 4.2v.
My questions on 4s2p configuration, is what AWG should the individual cell/balance line lines be? Can I get away with 24awg, to keep the extra wiring along the cells very small, and tight to the cells? Or do I actually need to go up to 20awg?
And also, I’d do 2p and put those cell groups into series, right? Thinking about physical configuration, I can put 2 cells (A) + to +, fold over into vertical orientation, then the next group is in (B) - to - configuration, and then I join A to B on A’s - to B’s +, and continue. And of course solder onto the nickel strip the balancing wire between each group. That should work out? I’ll have very short nickel strips, and I get the feeling I should pre-bend them to get the crease where I want, so after welding they’ll fold where I want, the way I want.