Velectrix fold throttle cut off after motor replacement.

[attic100]

This is my first time here. My sincerest apologies if I’ve unknowingly disregarded any rules/practices in posting this here.

Now to the matter at hand. I bought used a Velectrix fold here in Aus. It had its battery and motor removed, and was on its original wiring, throttle, controller, display and PAS sensor.

I threaded in a new Bafang G311 to the front wheel and put a new UPP (I realise now this was possibly an unwise choice) 36v battery. The new motor is an upgrade from 200w that the bike originally sold with to 250w. Both motor and battery are 36v units in accordance with the ratings on the controller.

Now, PAS works flawlessly, but the throttle cuts out after about a second or two. Lifting the front wheel reveals that the post cut out, the throttle does manage to spin the wheel but extremely slowly.

In addition to this the speed readings on the display are extremely overblown, I’m assuming at lest 5 to 6 times higher.

I have two questions:
1. I have a feeling the throttle cut off happens due to the inflated speed, because the stock controller/display (apologies I would like some clarity on this) has a built in speed limiter.
2. How on earth do I resolve this? From threading a wheel to working out the electrics, everything has been a first for me here, so saying I’m a newbie would be an understatement.

P.S. Yes PAS works fine, but it often causes the front wheel to spin out, which was fine till on a rainy winters night I took a bad fall on the pavement and busted my wrist cartilage. So I’m pretty hell bent on getting the throttle going at this point.

Resources:
Here is a link to the bike specs: https://www.99bikes.com.au/velectrix-foldaway-grey-2020
Please find attached, the picture of the bike controller. I think it’s the same one that came from Velectrix when it was bought by the previous owner.

 

[amberwolf]

THe original motor probably had a 1-magnet speed sensor in it, while the new one probably has a 6-magnet speed sensor in it.


If there is any way to get into the menus on the display to change the "number of poles" of the speed sensor, you can change it to 6 instead of 1.

If there is not, then there are at least two options:

--you can open the motor (take off it's side cover) and remove 5 of the six magnets embedded into it near the axle. They will be something like this:
https://endless-sphere.com/forums/download/file.php?id=308440
https://endless-sphere.com/forums/viewtopic.php?f=30&t=114480&p=1708281&hilit=dapu#p1692682



--you can open the cable to the motor, on whichever side of the motor/controller connector you prefer, and cut the (probably) white wire to the speed sensor, and expose the ground (probably black) wire as well but not cut it. Get a regular bike speedometer sensor with it's own magnet like this: https://ebikes.ca/ca-speedo.html and connect it's two wires between the ground wire and the controller end of the speed sensor wire. Mount the speed sensor per it's instructions to the frame or fork near the wheel spokes and the magnet to the spokes (per instructions).

In either case now the system has only one magnet for the sensor and will detect the correct number of wheel spins so the system will see the right speed, and shoudl then operate about the same as it did before.


If you don't mind building a small electronic circuit, you could make one that divides by six, so that you get just one pulse out of the six from the existing sensor sent to the controller. Can work out details if you want to do this, but it's more complex than either of the other options above that will likely "just work".


Alternately, if you want better PAS control (and throttle) and the ability to change settings via onboard menus to customize operation better, you could replace the orignal controller and display with a KT (kun teng kunteng) controller that comes with it's own display (displays are generally not intercompatible, so get a kit with both parts together), which uses "torque simulation" rather than speed for the assist-level control settings, making the power of the bike more controllable with the limited PAS control any of these systems have; it's more bicycle-like in operation.

 

[attic100]

Thank you so much! I’ll look into it and get back to you if it doesn’t work out. I think it should though. Hope that’s alright!