I took bike.4 out for a test run today after reprogramming the controller to allow more current. Going up the hill at the bottom of my road, the ammeter said it was pulling 40 amps, continuous! And after a few dozen yards, it died. I knew immediately what the problem was.
I used 13 amp wiring for this, because I wasn't expecting to to take more that 10 amps, maybe 15 at most. 40 amps is just too much for the puny wiring, and too much for some of the connectors, too! So I've rewired it using much thicker cable; 4 sq mm, which ought to be able to carry 100 amps.
Here's what the bike looks like.
The first picture shows the bike overall. The new back rack is supporting a pannier, and the battery is in there. The controller is on top of the rack. There's four ugly wires going from the controller to the handlebars and back; that's only temporary, so I can see the current draw as I go along.
The second picture shows my view from the saddle. From left to right, compass, GPS holder bar, ammeter (that's temporary), speedometer, voltmeter and gear changer.