Fault finding help

[iain85]

Help!

I've got a ku123 controller and bafang 500w hub. Left house today for a ride and bike rode beautifully up hill for about a mile and when I went to turn off into the woods I noticed the throttle had stuck on.i manged to get it stopped and pull the battery connections. I plugged it back in again and although there was lights on the throttle there was nothing when I twisted the throttle.
I had a look for a loose connection and found the yellow wire from the hub hanging from the connector with scorch marks. I remade the connection and retested but again, just lights and no power.

So multi meter is at the ready, any one got any advice where to start?

Thanks,

 

[iain85]

Ok, so with a quick search I've learnt that the controller supplies 5 v to the throttle which it does with the throttle connector unplugged. Although when plugged in this value goes down to 1.16v ( across red and green. I've tryed linking the throttle connector out across the red and green and still doesn't seem to want to know. Does the controller requires specific values to work?
what's next?

 

[103Alex1]

I had a look for a loose connection and found the yellow wire from the hub hanging from the connector with scorch marks. I remade the connection and retested but again, just lights and no power.

I'm sure someone more knowledgeable will help with the testing - but do you mean one of the 3 phase wires leading from the controller to the motor that come with bullet connectors covered in clear plastic covers ?

 

[Deleted member 4366]

We need to know what wire you're talking about and where it is, and what were the scorch marks on. If it was the yellow main phase wire at the controller that came out, and you continued to give it full throttle, you may have blown the MOSFETS in the controller.

You're cheching the throttle incorrectly. There should be about 5v between red and black.

If a phase wire becomes disconnected, It can't hold the throttle on. There's another yellow wire on the throttle switch. Is that the one that came out? If so, were you using the switch, and what for/how?

 

[iain85]

Hi,
Sorry if I was unclear. I tested the wires that comes from the throttle to the controller. I tested across the connector where they plug together. Across red to black and red to green from the controller measured 5 volts unplugged. When the throttle was plugged into the controller is only measured 1.16v which I across the same wires.
There is not voltage at the phase wires (large yellow wire coming from the controller) going to the motor. The scorch marks I think are from the connection becoming loose and are round the bullet connector rubber sheathing.

Is there any clues from the throttle sticking on before hand? Also the throttle loosing 4 volts somewhere?


The small yellow wire for the throttle power is fine and is wired directly to the battery. The battery power is showing 40.2v

 

[Deleted member 4366]

I can't help you if you don't answer my questions.

Which yellow wire became disconnected?

 

[iain85]

Sorry thought I did.

The yellow wire coming from the controller which I assume is the phase wire is the one that came out.

The yellow wire on the throttle wiring loom is the battery indicator right? That is fine and unaffected. There is no 'switch' I'm aware of.

 

[Deleted member 4366]

When a phase wire comes out, it can't directly affect the throttle other than melting the controller, which could cause an internal short.

You need to test the FETs. Use a meter set to resistance in the range kilo-ohms.
Measeue the resistance between each phase wire and the battery black wire in each direction, I.e. red probe to black battery wire and then black probe to battery black wire. That makes 6 results. Repeat the measurements to the battery red wire to get another 6 results. Post the results here. The controller should be disconnected for this test

When throttles run on, it's usually because they're broken. Test by connecting to the switched on controller. While connected, measure voltage between the black and red wires and then the black and third wire (not red).

If you can't wait, you should open the controller. Undo the screws on the wire end and side to slide out the pcb. Look for burned thick tracks to the FETs on the non-component side. It should be obvious if you have it.

 

[iain85]

Hi,
Sorry it's taken so long to get the results as I've had a hectic weekend.

I hope I've measured these correctly and understood your instructions, if not let me know and I'll go back and re do the tests.

Yellow phase to red = 9.6kohm Yellow phase to black = 7.56 kohm
Blue phase to red = 11.6kohms Blue Phase to black = 9.3 kohms
Green phase to red = 11.3kohms Green phase to black = 9.3Kohm

I know you said test with black probe then red probe but the resistance values stayed the same as above both ways of measuring.


Throttle red - black 68mv red - green 69mv


I'm hoping the high resistance values mean an intact controller?

 

[Deleted member 4366]

They should all be the same, so the yellow one is a bit worrying, especially as that's the one that disconnected. Time to open the controller. Check the thick tracks to the FETs and have a good sniff around the four yellow FETs

You're still measuring the throttle incorrectly. With it connected and powered:
Black to red =?
Black to green=?

 

[iain85]

Doh...

Amateur mistake, used to testing A/C stuff at work.

Yes the yellow is the suspect cable. Il take the controller apart and report my findings.

Probably tomorrow now.

Thanks,

 

[iain85]

Ok black to red = 68 mv
Black to green = 0.01 mv

I took the controller apart and there is no obvious damage to any components. I have taken a photo and would be happy to email it to you Dv8eh if you pm me your email address? One think I did notice upon disassembling the controller was the chip board was not located in the guide.

 

[Deleted member 4366]

How come you had 5v on the throttle before, but now it's only 68mv? You must still be measuring incorrectly.
No need to email the photos. Post them here following this instruction, post #3:
http://www.pedelecs.co.uk/forum/announcements-feedback-support/15268-does-forum-picture-upload-work.html

 

[iain85]

I did wonder that myself, when the throttle is unplugged at the connector block, the wires coming from the control box measure 5v when disconnected. and when connected the the throttle the measurement is 68mv.
The pics are on my phone and am away for a while now so navigating the photo upload process is beyond me!

 

[Deleted member 4366]

If the 5v drops to 68mv when you connect it, there's a dead short on it. Have a look where the wires connect to the hall sensor.

 

[iain85]

Ok great thanks, will the hall sensor be located in the throttle control or in the control box?

 

[Deleted member 4366]

In the throttle. Which throttle do you have?

 

[iain85]

It's the full width throttle supplied with the bafang kit from Bms battery.

 

[Deleted member 4366]

I can't remember whether they have a little inspection panel that you can remove. Even if it does, you probably have to pull the throttle apart, which is really tricky. Take it off the handlebar and look inside. There's three wide barbs that have to be held off while you pull it. You need something like thin flexible knife blades. You'll get the idea when you see it.

 

[iain85]

Ok thanks il report back.