I picked a 48v 20ah headway battery pack with the 38120 batteries.
The tabs are soldered, but at least i'd still be able to work on the pack if a single cell failed.

It comes with a 60amp max BMS, but this is only for hill climbing, so i'm not too concerned with hitting top speed anyway.

One of the issues i'd been dealing with is I have a good bit of money in my rear bike rack and bag, and I wanted to find something that would fit in it, and the space is very limited at 6.5"x6.5"x12".
My escape plan if I couldn't find a small battery, was to put a larger Topeak bag on the rear, and use my current rig up front.
Fortunately i'll be able to keep it the way it is. And the bag's side pockets are large enough to hold what I carry with me anyway.

It's not the prettiest job of assembly i've ever seen, but I like the small number of large batteries in these.





I got it from an ebay seller out of San Fransisco with the username of electronicstore.