I did work like this on the main Leads and some series connections. It’s not a problem to solder first and then weld. Just make sure you don’t weld on solder 
you don’t want to weld on solder 
If you think there is no other way than first weld it and then solder it, you could do it like @glyphiks I think he use an alu plate under the nickel while soldering to get the heat away faster.
There should be some pictures somewhere here which show how he is doing it.
*Me about to solder together my first pack in 2017.
It hasn’t caught fire… Yet…
I have given up on the aluminium strip underneath. Too many accidental shorts 
I just use folded nickel and forceps now. The forceps are great as they hold the wire in place, stop solder from wicking too far, they act as an excellent heatsink, and they prop the folded nickel up off the cells.
I make the joint quickly, blow on it furiously and then cool the joint immediately with a damp rag.
I regret not getting those for my pack…
I’ve never heard of this nor seen any cell datasheet mentioning that.
Is it because there’s a tab welded inside to the middle of the negative/bottom side of the cell?
Are those 18650s? If so, can you tell me the height of this all wrapped up? Pcb+staggered DS 18650s + wires and wrap?
I’m planning similar battery build and want to know what size gasket I would need on my SS enclosure, and how much ground clearance it leaves me.
Yes.
Scroll up to an earlier post of mine, 16 hours before this post. That’s the VTC5A datasheet.
I thought were not supposed to blow on solder to cool it…
Why not?
Does anyone have proof it becomes more brittle? I understand the logic if you’re assuming it acts the same way as steels and such when looking at their hardness or toughness based on cooling curves, but I’m not sure I’ve seen evidence to quantify that cooling it faster is detrimental to the joint strength.
I would like to know as cooling with a damp rag cools it down pretty damn quick
I’ll search around. I know pipe fitters cool with rags sometimes and if you don’t allow it to cool enough before you put water through you can hear it pop. But thats also braising not soldering.
I’ve honestly heard both and I wish I had a definitive answer, but from my understanding the rapid temperature change when blowing on it doesn’t allow the atoms of the metal to form in its usual lattice structure which is inherently stronger but that could all be bullshit idk
I wish I knew tbh
I just did some quick reading, i think as long as it doesn’t crystalize its all good. Usually if it does crystallise i reflow it… but definitely something i will take into deeper consideration
I think the rag is so the wall near the pipe doesn’t catch fire.
I don’t bother with the cooling. the best way I’ve found to keep heat from wrecking my work is to keep everything squeaky-fuking-clean and work with a purpose. If the iron has to dwell on the work, that’s when the heat starts building up where I don’t want it. When the work and tools are clean, solder melts almost instanty
oh yeah, the braid gets heat sinks because I don’t want it to wick
What sites are the best to purchase cells from? (I’m in the US fyi)
would it be smart to make a like tp4056 cluster charger to charge up a 10-12s battery ? 
or any number of series lol
depends how many you need. BulkBattery is good if you can meet the MOQ.
I’ve scored some good deals on Battery Clearing house
and I use IMR or 18650Battery Store when I need them fast and can’t wait for a deal or don’t want 200 cells
These sites come to mind:
**Yes and battery clearing house
If anyone knows of any others I’d also like to know
