I have a BBS-01 mid-drive on my 2003 Giant NRS-1 mtn bike, which I use to commute to work, 17 miles per round trip. I have an AllCell 36V 10.4 Ahr battery in a frame bag. I use about 150-180 Whr on my commute (10 miles/whr). I do enjoy pedaling and the occasional drink from a water bottle, but the bottle cage has been sacrificed for the frame bag. I am thinking about what the minimum battery I would need for the commute, which is the longest trip I usually make on the bike. What is the smallest form factor I could buy/make for this purpose? What if I used 3.7V 6800 mAh 26650 cells to make a 10S pack? That would only be 10 of those cells, which I probably could fit comfortably in a seat bag. That would give me enough whr to do my commute, even without charging at work. That would seem to be smaller than 20 3.6V 18650 cells.