Awhile ago I'd bought a new sprocket to install on my motor, the purpose being to up the gear ratio a bit. EV enthusiasts often rave about the flat torque curve of electric motors, but that's only true at low and moderate speeds. If you're supplying the motor with a fixed maximum voltage, there's a fixed maximum RPM that the motor will go, and the motor will provide zero torque at that RPM. Near that maximum, the available torque declines linearly. If you hook the motor to the wheel with a fixed ratio, as my bike does, you have the least torque available at the highest speeds, which is kindof a bummer since that's where the greatest drag is. It's not a problem if you have enough assistance at the speeds where you need it, but I was able to outpedal the motor at top speed, resulting in no assistance. Since the point of the motor was to go faster than I could by myself, this was no good. Thus, the new sprocket, to put the no load RPM above the achieved top speed.

I finally got it on a couple days ago....

...after two hours of swearing, mostly at the chain. Yes, it goes noticably faster, and in the way that matters, too: total trip time is now about 25 min, instead of 30. It sucks more power, of course, but that's the point. It wasn't supposed to increase energy efficiency, in the miles-per-gallon sense, but to use more energy, in exchange for a higher quality of life. The only question is whether it's efficient enough to make it to work without the batteries cutting out. Yesterday was fine, it cut out just as I was rolling into work (perfect!), but today was a problem, due to high wind. We'll see about the trip home.