Pin plug - 8fun Bafang SWXK37

[acid6]

Hi guys and ladies.
I decided to improves max speed on my SWXK37 but have issue with 5pin plug.
Does enyone know where is PL, P+, GND, RXD, TXD?

View attachment 1

 

[d8veh]

Is that the only motor cable? If so, it's three phase wires and a thermistor.

Where did you get those designations from? (PL, P+, GND, RXD, TXD)

 

[acid6]

Its connector between display and main cable...
Here is displays serial nr, and 2 outgoing cables:



here is 5 pin connector going out from dispaly:

Where did you get those designations from? (PL, P+, GND, RXD, TXD)

Just googling a lot...
Any idea? How to check it?

 

[d8veh]

Show a picture of the top of the display so that we can see which one it is. Some are analogue and some are digital.

From the photo, the display can be disassembled (screws underneath and glued with silicone). The wires' designations will be marked on the PCB.

 

[acid6]

OK, Here is top of the "display":

I've tried to open it but it's glued all around...

 

[d8veh]

They normally use silicone to glue it, which is not very strong.

If you don't want to/can't open the display, you can look in the controller where the 5-way cable is soldered. Ground and battery voltage should be obvious. The battery return will go to the big resistor (probably blue wire). The Tx and Rx should be marked. Remember that they swap round between the controller and display (Tx sends to Rx)

 

[acid6]

OK, I got to the inside, was't easy, and this is what I found:

HR - yellow
OUT - green
GND - black
VCC - red
something - blue

 

[d8veh]

From what I can see, it smells of an analogue device. can you get some more photos of what's on the PCBs?

Another thing you can try is measuring the voltage between black and green wire at the different PAS settings. If you measure something like 1v, 2v, 3v, it's analogue. If you can't measure anything, it's digital.

While you have it open. you can check the continuity to the pins on the connector to find out which is which.
Red is battery voltage
Black is ground
Blue is switched battery to power the controller
Green is PAS signal - digital or analogue
Yellow is Rx if digital and probably redundant if analogue.

Where do the red blue and black wires go? Is there another connector?

 

[acid6]

Red, blue and black cables are going to the wheel speed "sensor".
Measured green and black and its 4,5V,that's mean it's analogue.... It's wrong? Possible to "tune" it?

 

[d8veh]

Those photos don't give me what I want. maybe what i need to see is the other two sides of both PCBs.

If the wheel-speed sensor is connected to this device, it changes things anyway. You need to measure the voltage on that green wire to confirm whether this gives an analogue signal to the controller. I suspect that it does and that this device is processing the speed signal and then using the yellow wire to give a yes/no to the controller for power.

If you have a normal wheel speed sensor with a magnet on the spoke, try removing the magnet from the spoke or sliding it away from the sensor. That works on some bikes, though others either default to 25km/h or go to sleep after 5 minutes without the speed signal.

 

[acid6]

View attachment 1




so, took new photos, but didn't separate this to plates, looks like they are "welded' toghether.
I've removed magnet from the wheel but see no different...
Than start measuring and accidenly make shortcut
So after booting starts blinking single LED on contorler and motor it's dead.
ufff

thats it.... he he

 

[acid6]

Desperate began to disassemble everything and this is what I found:



View attachment 4

View attachment 2

 

[d8veh]

That white wire with 4 pins (holes) is the programming lead, where you program the speed limit. If you'd shown that in the beginning, it would have saved some time.

Your LED panel carries battery voltage on some wires. If you shorted one of those to anything else in it, serious damage can happen, so it's probably finished now and would need to be replaced by exactly the same type, which I guess you'll only get from the original bike supplier.

You have one more choice, and that's to replace the controller and Panel with different ones, like a S06S and S-LCD3 from BMSBattery, though there's several complications:

All the connectors will need to be replaced (cut and solder wires)
Your present controller is wired directly to the battery connector, so you'd need to unsolder it and figure out which pins are the positive and negative. You can look in the battery to see which pins have wires on.
You need to find a place to install the new controller. I'd use a small tool-bag, like those that fit under the saddle or in the frame triangle.