Giant Twist Express RS2 - No Power

[Pointy]

Hi,

Whilst I am an eBike noob I am reasonably competent at electronics but could do with some help with this.

I just bought this bike 2nd hand, advertised for spares or repair as the battery wasn't charging, the seller stated the charger flashes red momentarily and then nothing. However upon getting it home the battery (26cv9ah) was reading 28v and when I connected the charger the red light came on as expected. (It just occurred to me that it might behave differently if charged on the bike?)

Anyway the long and short if it is that nothing happens when pressing the on/off button on the display. I am thinking it can only be the controller, wiring or display. The controller has 28v at the connector from the battery.

The controller looked like this to start with...

After chipping away at the silicone it now looks like this...


Back side...



I have managed to reverse engineer the display...



The display lights up when powered from my bench supply and the mode button changes the mode as expected, but no battery level lights are lit.

If anyone is familiar with these bikes can give me some pointers of where to look, I would very much appreciate it.

Regards,

Les

 

[Pointy]

I forgot to say there is no voltage going to the display, which looks like it is driven by Q10 on the controller. (near or, yel, red, gr, bk wires)I have not traced it any further yet.

 

[Pointy]

Sorry to keep replying to myself.

I am trying to see it it is cost effective to repair this bike. The battery charges to 28.7v and while I don't have a high power load to test it, I did run a led strip for 12+ hours overnight without issues.

I am guessing the display is ok because of the fact the mode button works, if the MCU was dead then it would not do anything.

So other than the controller the 2 unknowns are the motor and torque sensor.

I do have a 24v Apollo Phaze bike that I could maybe use to test the motor.

So how would I test the torque sensor? It is 3 wires, red, black and brown. I would assume to the red/black are DC and the brown is output. What voltage would it run on and what would it output?

Thanks again for any help.

Les

 

[Pointy]

I can answer my own question about the torque sensor voltage as I can trace it back to the 5v line.

Unfortunately I think the controller is fried as there is 26v on the 5v line now.

 

[docw009]

It's probably a cadence sensor, but it still should run on low power. Controllers are inexpensive, if you can locate the phase wires on the motor. Run it with a sensorless box for simplicity,

I didn't see any voltage reference circuitry on the LED schematic. Maybe it gets serial data transmissions on battery voltage from the controller? Unusual on a LED unit, but I have one that does that.

 

[Pointy]

The sensor is something like this and is not cheap! The motor phases are marked on the controller as A, (brown) B (white) & C (grey) and hall sensor wires are the same colors, but as I know nothing about brushless motors I am not sure if it helps for testing purposes.

 

[Pointy]

Today I made up a test cable from an extension cable I had bought to replace the damaged wires on my Apollo's motor. This would allow me to connect the Giant motor to my Apollo bike...



I powered the bike via my bench supply to I could monitor and limit the current.

It didn't work, although it did appear the motor was trying to go backwards and drawing way to much power. After swapping the yellow and green wires round the motor worked as expected.

Of course although the colors are the same in the extension cable, it doesn't mean they are in the same order. I need to double check when I replace the Apollo cable.

I then set about testing the torque sensor, which was outputting about 1.4v on the brown wire and didn't appear to change when turning the peddles. However when holding the back wheel and trying to peddle the voltage went up to about 2.5v, so I assume this is working.

 

[Pointy]

Having decided to replace the controller, display and torque sensor, I finally have all the parts...

BMS S06S Controller.
KT LCD4
KT-V12L

I hooked it all up, using the bench supply and it appears to be working, I just have one thing to sort out. The Giant speed sensor is just a reed switch/sensor (2 wire) can this be used with the controller? Is it just expecting a positive pulse, if so can I just connect the red/white wires?