Hub motor does not run at its rated power

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seba240698

100 mW
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May 10, 2019
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Hi, I bought a KT36/48ZWSRT-LCD-CAD controller for brushless motor via online platform. See attached diagram.

The package came with a LCD (LCD3, see attached user manual) and a PAS using a split magnetic disc and a KT D12L cable.

After I installed them into my e-bike, everything worked fine except that the motor ran at only 19W as shown in the LCD, even though the controller is rated at 250W. The hub motor in my e-bike is rated at 250W/350W and it was running well 2 weeks ago, except the old LCD was giving me intermittent problems (the screen would blank off and the display was distorted due to water seepage caused by rain). My old controller was doing well although it was already 4 years old. I was very worry that if I were to buy just a LCD, it might not be compatible to my old controller, that was why I bought a whole set (LCD + controller + PAS).

I communicated with the seller, he merely e-mailed me the KT LCD3 user manual which I managed to read all of it yesterday. I changed the motor power (C14) and maximum allowable current (C5) settings to maximum but still motor only run at 19W. I do not understand some of the settings like P2, wheel speed pulse signal setting and C1, power assist sensor and parameter select setting.

I was thinking to buy another controller but then worry that it may not be compatible with KT LCD display.

Do you suspect that this problem is due to LCD setting only or are there other possible cause of it?

Thank you.
 

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If you're just spinning the wheel in the air, the LCD3 will only show minimal watts, You have to be riding to see watts, I'm not sure there are any settings that will affect this, If you are riding and only seeing 19 watts .... I've never seen that and I have installed about 10 LCD3's.

P2 is either 1 or 6. Most Bafang motors use 6,
I have
C1 = 1
C2 = 0
C3 = 0, bike powers up in PAS 0,
C4 = 0, no throttle in PAS 0,
C5 =10. max power
C14 =1, max pedal assist,

The others don't matter, but leave C9 at zero. You don't want to enter a password every time you turn on the bike,
 
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docw009 said:
If you're just spinning the wheel in the air, the LCD3 will only show minimal watts, You have to be riding to see watts, I'm not sure there are any settings that will affect this, If you are riding and only seeing 19 watts .... I've never seen that and I have installed about 10 LCD3's.

P2 is either 1 or 6. Most Bafang motors use 6,
I have
C1 = 1
C2 = 0
C3 = 0, bike powers up in PAS 0,
C4 = 0, no throttle in PAS 0,
C5 =10. max power
C14 =1, max pedal assist,

The others don't matter, but leave C9 at zero. You don't want to enter a password every time you turn on the bike,
Click to expand...
Thank you.

The 19W was shown when I was riding the bike.

C14 should be 3 when we select maximum pedal assist as per the user manual. No?

Everything is new except the motor, and I don't suspect the motor fault as it was running well 2 weeks ago. Just check, what should the voltage between the 2 phase wires to the motor be? My battery is 36V and it is healthy. I will check it later to eliminate motor fault.
 
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docw009 said:
Is the bike running normally? Probably a bad display.

You're right about C14. I just set an LCD3 to 1 for my grandkid today to keep it tame, Lot of good that did. She just told my wife .."Granny, I'm on 5!" and I see her tearing down the street.
Click to expand...

The bike runs smoothly, just lack of power.

Ha, young kids should ride normal bicycles, to expend their excess energy. :)

Thanks anyway.
 
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Just now I went to try all possible solutions I could think of. When I was at the midst of giving up, I told myself maybe the 3 coloured phase wires from the controller to the hub motor were connected wrongly.

Without pinning much hope, as if it was the case the motor would likely not turn but for my case, it turned but slowly, only 19W, I swapped the yellow wire with the green wire (the original connection followed the correct colours). And voila, the motor turned with much vigor and speed!

I test rode it as it was as good as the old controller. At assist level 1, the power was 180W, level 5 was 400W.

I still don't understand why the motor could turn when the phase wires were connected wrongly previously.

:)
 
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Great work!

There's a few false positives in the 36 possible wire combos. They are characterized by noisy running and low power. Using KT controllers, I've been lucky and they've always worked by matching colors. Then again, most motors I used were either new or of a popular brand.

When motors don't spin, this flow chart is often suggested. It ileaves the hall sensor wires unchanged with an unknown motor/controller combo , and swapping the phase wires. Reduces the 36 possible combos to 4 at most. Looks like your combo was in the bottom left side.

W!hat's interesting is that false positives are said to take a lot of current, but the LCD3 registered low, so the controller must not be able to measure it in those situations,

phase.jpeg
 
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