I try to avoid doing maths on a Sunday, but let’s do some here. assuming an average of 40 Amps to keep you on foil you’d need a 40aH pack. That’s a 10P of those nice 20700’s. Now we need the 12S part, so that’s 120 cells.
with the quantity discount that’s $907. Not too bad.
I don’t happen to have a 20700 in front of me but I do have an 18650 right . . . here, and it weighs 1.2 oz. So the 20700 is roughly 120% the size of the 18650, so that’s 1.44oz per cel, times 120 = 10 pounds in cells (alone, not including welding strip, wire, fuses, etc.). Also not too bad.
So assuming I did my math right I think you’re fine. In fact looking at those numbers the Turnigy pack is not such a good deal. Almost as much money and only 22Ah. Hmmm. Looks like I might be digging the ol’ battery welder out after all.
Of course I did say something about convenience, which still matters a lot, so I’ll likely stay the course, though my second pack might be a 1 hour pack.
The thing I have to do is design ahead of time so that all packs use the same size Pelican case and fit in the same cavity on the board.