Bike.1 performed magnificently yesterday; I went through 3 and a bit batteries, which means about 20 miles.
Today, I gave it a wash down (it was very muddy from the outing), and when I tested it again - nothing. Dead. I suspect that water has got into the works, either the motor or the electronics. I'll leave it to dry out for a while, meanwhile I'll use bike.2
... later ...
Bike.1 is working fine. I didn't do anything to cause that, so I think it just dried out!
I'll try to think of a way to really waterproof the controller and wiring. I don't think I can do anything about the hub motor.