Hi @Cephalotus. Inspired by your post, I'm going to build my own range extender for my bike Trek T700+ with Bionx system.
Original battery still working for some kilometers, this is TREK R320 - 39cells, 48V, I think 6.6 Ah (320Wh).
Look's like 13s3p battery pack.
My question is: as a range...