Well, after sitting in the corner of the workshop in pieces for more than a year, the electric NSR is back up and running again! I had planned to convert it to AC, but decided just to get it back together with the motor I had (Motenergy ME0709), and fix some of the old shortcomings.
Its main problem was the battery pack, which I'd assembled from a bunch of old K2 26650EV cells, which performed way under spec and resulted in a 35km range - just too small to be useful. Unfortunately the (conveniently) available space for batteries in the NSR is very small, so I wouldn't have been able to fit many Winstons / CALBs / Headways in the space. But after learning that Matt Lacey had a pile of surplus A123 20Ah pouch cells available, I purchased 44 cells from him to build a new pack from.
It's 44S1P, so approx 140V 20Ah, 2.8kWh, with Aegius termination/connection kit and 4 of my 12-cell BMS modules. Enclosed in a polycarbonate-lined steel frame, with 6mm polycarbonate plates top and bottom and clamping brackets+bolts for compression. (Matt informed me they're meant to have something like 150 pounds of compression to prevent cells swelling.)
It was a pretty labor-intensive little thing to build, but turned out quite well. Below are a few pics showing testing the BMS on the stack of connected cells, the complete pack in its enclosure, and installation in the bike. (Still fits under the hollowed-out fuel tank shell.)
Another shortcoming with the original build was the gear ratio of 3.3:1 being too low, making it hard on the poor little motor. So I replaced the 12-tooth motor sprocket with a 10-turn, giving it a somewhat-improved 4:1 ratio. This yields a motor speed around 2000rpm at 60km/h, which isn't too bad. After a 10km ride, the motor was about 60 degrees. Throttle response is noticeably peppier with the higher ratio too. A 5:1 or 6:1 would probably be better still, but I can't go any smaller on the motor sprocket and might have chain clearance problems with a much bigger rear sprocket.
I also finally got around to replacing the front forks, since the old ones had been slightly bent since I got the bike, which slightly compromised its handling. (Some previous owner must have had a nasty crash at some point!)
BMS testing of assembled stack of cells
Complete battery module
Installing new battery in bike
New 10-tooth motor sprocket
