Are these normal phase wire voltages?

[Vic Dupont]

Hi there!

As I am trying to troubleshoot a problem on my electric bike, and got stuck, I tried measuring the voltage on the phase wires, to know whether my controller is faulty.

I would like to know whether that looks normal or abnormal to you, since I have no idea what the correct values are, and I don’t know whether my methodology makes sense.

The way I measured is the following.​

In order to have something that might make sense, I disconnected the phase wires from the motor, so that it doesn’t move. I kept the hall sensors and speedometer wires plugged, so that the controller has the information coming from the motor. I disconnected the brake cutoffs and lamp, to avoid them interfering. I also opened the controller, to be able to measure voltage directly on the circuit board, to rule out potential wire issues.

Basically it’s a pretty normal setup, except for the phase wires that are disconnected and the controller that is open.

I turn the pedal when I want to measure, and then I use a basic multimeter to measure voltage on each phase wire’s solder point.

Again, note that the motor doesn’t move. The pedal movement just ensures that the controller gets the signal to kick off the motor.

In order to change the sensors value, I simply turn the back wheel backwards and measure the hall sensors wire solder points to know where it landed.

Let me know if you think this method of measurement is not usable.

If it's of any use, my controller is a Lishui EPAC Drive System, part number LSW06-90B1CF SB.

Here are my results:​

When idle, meaning pedal is not turning:

When turning pedal:

Some things to explain:​

- I made several experiments for each motor position, and noted the result of each measurement, separated by commas. I made sure to turn the wheel, and thus change the motor position, between each experiment.
- when I include an arrow, such as 0->9, it means that for a few seconds it was at 9, and after maybe 4 or 5 seconds it rose to 9
- twice I had results that were the same as when idle, and controller’s light was flashing differently, not regularly. After I turned the wheel it went back to « normal ». That’s what I indicated as « flashing ».

There are a few things I notice:​

1. when idle, meaning the pedal is not turning, the yellow phase wire has 13 V voltage when measured using DC mode on multimeter. I would have expected 0V.
2. my measurements when pedal is turning seem to hint that in a normal setting, each phase wire would be at either 0 or 35V, which is close to the battery’s voltage, and that the wire with the 35V would be a color that is at 3.3V in the hall sensor cables. This is just my guess, tell me if that’s how it’s supposed to be
3. It seems to me that the most abnormal measurements seem to be on the yellow phase wire, when it’s supposed to be at 35V, and is instead at 6 or 8V

But again, I am just guessing, I have no idea what the correct values are.

Do you know whether these values are normal or not?

I previously tested for shorts between the phase wires, ground and battery positive, to detect a blown transistor, but everything seemed normal.

For those who are interested in the whole history of this bike’s problem, here it is: https://forums.electricbikereview.com/threads/temporary-power-outages-and-motor-noise.57987/

Thanks a lot in advance for the help!

 

[harryS]

I feel you're wasting your time.

Best way to test a motor is to hook it to a good controller. Conversely, you test a controller by hooking it to a good motor. Here's two schematics for popular controllers that are representative of motor drives. You can examine the mosfet drive circuits,

 

[Vic Dupont]

Thanks a lot for the reply, and for these hints!

I agree 100%, I would love to be able to plug a known good controller. The thing is, I don't have any at hand. I could buy one, but apart from the money matter, I feel like it would also be a waste of many resources if my controller is not the problem.

Conversely, I feel like the methodology I came up with, if it turns out to be meaningful, could be very useful to many people who are not bike repair professionals. It would enable anyone with a multimeter to test the behaviour of their controller without having to buy another one, and even without having to wait for it to arrive.

Looking at the numbers I measured, do they seem normal to you?

Among other things, is it normal that the results are different for the three wires? I would have expected things to be symmetric. Is there usually an intentional asymmetry, which could explain that my yellow phase output doesn't look the same as other colors?

Similarly, is it normal that I measure a 13V voltage on the yellow phase even when everything is idle?

Again, thank you very much for the help, I really appreciate it.

 

[harryS]

It's all digital in the end. The controller only looks to see if the Hall signal is above its digital Vin, probably 2V. However, your Hall outputs, which I didn't look at, should be similar.

As for the 13V, you;re the circuit guy, I gave you two typical drive circuits to get you understanding it, Figure it out.

I saw your other thread. Summers almost gone. Your girl friend didn't have a bike to ride for months, WIth the right gear, someone could have figured out whether motor or controller in an afternoon,

 

[PCeBiker]

I personally think that the controller is at fault, be it a mechanical hardware/connection issue or a programming software issue

Your motor obviously works.
You got it spun up.

The motor is a much simpler device than all the inputs and software that controls it.
And a dual mode controller can spin up a wheel with no hall sensors at all.

I say Waste some money on a new controller and enjoy the rest of the riding season.

Your girlfriend may thank you for it.