Purely in the interests of experience, I've taken the plunge and ordered 14 cells plus related stuff for a 1P battery pack. This is intended as a small 'on bike' battery for my old mountain bike and my 48V TSDZ2 which has been in its box long enough.
My daily commute is 5 hilly rough miles return, which it will manage fine, and my shopping trips are 10 miles, which should also be OK.
For longer trips there will be a small trailer containing a larger battery, and the bike might grow small 20W or so front and rear horizontal solar fenders!
I may find 1P, about 200Wh, is too small, but it is the edges of a range where the most learning is to be had. I have not decided whether to go 12, 13 or 14S. An even number or a non-prime number packs best, but 13 is the nominal 48V!
I went to fogstar wholesale and bought Molicell P45b, because although the image does not say so, the nicely priced P42a are out of stock.
Slightly more trouble sourcing a spot welder. On all things battery build related, I look to
@Nealh's excellent detailed write ups, so I went straight for the Malectrics device, which comes from overseas with a minimum order value requirement that is more than the kit! A little head scratching later, I ordered two! So there may be a spare already imported one available in a while!
No promises on a build timescale.