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A project log for Woody the Electric Four Passenger Bicycle

Woody is a scratch built quad wheel bicycle with four passenger capacity, with electric power to assist pedaling.

john-guyJohn Guy 10/31/2023 at 01:320 Comments

the electric system on Woody will be tricky. Two Bafang motors with their 9 signals, extending over a longer distance, to a a pair of controllers intended for dual drive use, but with sketchy documentation and random connectors.

The plan is to cut the connectors away and shorten the cable from the hub. These were about 16g wires for the phases, about 28g for the signal wires. I used 14g to splice into the phase wires near where they exited the hub. I used a piece of copper strand to tie the two wires together before soldering, see below. This picture is actually battery positive, not a phase wire, both about 16g. Batteries connect with XT90 connectors, to an X harness connecting the two batteries in parallel, then splitting out to two leads with XT90s to power the controllers.


next the phase wires were spliced to a multi conductor cable. Each splice was protected with heat shrink.


The motor had some sort of bullet plugs for the phase wires, I changed this to an MT60 connector.


for the Hall sensors and 5V etc the controller used this 3.8mm connector. I was able to buy a kit with 2,3,4,6,9 positions in each polarity, and a bunch of crimp on contacts.

The gauge was a bit small to be crimped so had to tin first, crimp, then solder.

One battery was a bit below the other, so 15 minutes of charging brought it within a couple milivolts. I then plugged they X harness which connects to two batteries to the two controllers, with batteries tied together in parallel.

So, does it work you ask? Well, somewhat. One motor functions but has very little power, the other had nothing. So next up, debug!

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