New KT controller acting strange

MCF

1 mW
Joined
Mar 27, 2022
Messages
11
Hi everyone,

I'm having trouble diagnosing issues on my current upgrade.

About the bike: motor is a MXUS XF19r was origionally running it on a KT 12 mosfet 40a controller with a 15s battery for approx a year. Bike used for commuting, pulling trailer with pretty heavy loads, and errands. All on street no bike paths and no recreational riding ( for recreation I prefer my push bikes). Controller went bad burnt up a mosfet presumably from beating the snot out of it with loaded trailer.

So I decided to go with a 20S and a KT 18 mosfet 50a controller. Got everything installed went for a ride and it was slow (struggled to get to 35mph, it.) Glancing at display power is bouncing from 800 to 1700w ( so around 27 amps max no were near the 50amps). Figured the BMS was bad so I bypassed it, same thing.

Put it back on the bike stand and ran it with no load. It will spin up to full speed, but if you keep it there for like 20 seconds sound changes like its bogging down with a load and power goes from 440W to almost 900W unloaded.

It's the strangest thing I've seen. I'm at a loss for what it could be. Is it possible for the new controller to be bad?
 
I'm wondering 2 things. 1st is regarding some kind of restriction in the wiring between the battery and the controller. Controller can't deliver any more power than it's getting.

2nd, in the parameters, something might not be set correctly?
 
I've gone through the parameters a few times. They all look good. (Same as on previous controller, that worked well)

Didn't think about resistance in the wiring to the controller. It's 10 gauge from battery to controller. Will check it out tomorrow, thanks for the input.
 
MCF said:
Put it back on the bike stand and ran it with no load. It will spin up to full speed, but if you keep it there for like 20 seconds sound changes like its bogging down with a load and power goes from 440W to almost 900W unloaded.

No load means no load. With the wheel off the ground, you shouldn't be using more than 60W or so. If you're pulling 440W, then your phase/hall wiring combination is likely mismatched. You can fry both your motor and controller if you continue to run it that way.
 
E-HP said:
No load means no load. With the wheel off the ground, you shouldn't be using more than 60W or so. If you're pulling 440W, then your phase/hall wiring combination is likely mismatched. You can fry both your motor and controller if you continue to run it that way.

I just went out and tried all possible phase combinations. Only one combo works, issue still exists. It was a great suggestion, thank you.

On a side note, with the battery voltage down to 64v it runs well. Will top out at 41mph and is giving me 2000w (per display) so aprox 32 amps. Charged battery up some to 77V runs ok up to upper 20s mph then feels weak display shows 1700w so 22a.

IDK my gut feeling is there is something wonky with the controller, just don't know how to prove it without buying another controller.
 
MCF said:
I just went out and tried all possible phase combinations. Only one combo works, issue still exists.

Phase and Hall sensor wires, or only phase wires? There are 6 permutations of phase wires and 6 of Hall wires, but only one out of those 36 possibilities runs correctly in the forward direction, and one in reverse.

Unless you tried all 36 combinations, there's still a likelihood you missed the one you need.
 
https://electricbike.com/forum/forum/kits/golden-motor-magic-pie/110168-testing-bldc-motor-s-phase-wiring-hall-sensors-and-wiring
HRaeRi4.jpeg
 
Chalo said:
Unless you tried all 36 combinations, there's still a likelihood you missed the one you need.

I did all 36 combinations got 3 that would go forward smoothly, oddly those 3 all pulled the same wattage and sounded the same.

E-HP said:
https://electricbike.com/forum/forum/kits/golden-motor-magic-pie/110168-testing-bldc-motor-s-phase-wiring-hall-sensors-and-wiring

Thank you for this link. I stumbled on it when I first started with this problem and then couldn't find it again.

this section from that page:

"Note: If resistance to turning by hand is felt when the motor is connected to the controller, and NOT with the motor disconnected from the controller. This would indicate bad FETs, I.E problem with the controller. See an excellent tutorial on testing controller MOSFETS here... GRIN: Testing for Blown Mosfets
Also on a geared hub motor, wheel will have to be turned in reverse to engage the motor."

If I rotate motor by hand with the controller off its smooth. With the controller on its notch and resists, turn off controller and its smooth again. So next step would be to test the MOSFETs, correct?
 
MOSFETs test fine
10kohms from phase wires to ground
OL (out of limits/inifinity) from phase wires to power

I think the resistance I am feeling is the clutch for the gears.
 
MCF said:
MOSFETs test fine
10kohms from phase wires to ground
OL (out of limits/inifinity) from phase wires to power

I think the resistance I am feeling is the clutch for the gears.

You may need to go through the hall/phase wire combos again. It's difficult to go through all of the combos without missing one, but the chart provides a methodical approach, so might be helpful. The high current draw with no load isn't a good sign. I'd check the motor and controller temps while doing your testing to avoid overheating/meltdown.
 
E-HP said:
You may need to go through the hall/phase wire combos again. It's difficult to go through all of the combos without missing one, but the chart provides a methodical approach, so might be helpful. The high current draw with no load isn't a good sign. I'd check the motor and controller temps while doing your testing to avoid overheating/meltdown.

Went through all combos again, wrote down all possibilities and checked them off as I went. Ended up with 3 forward and 3 reverse, that didn't set errors or sound like a coffee grinder. Controller and motor are both cool.

short video of what its doing unloaded at full throttle/speed.
https://youtu.be/Z5_TWpLJXvc
 
Went back through and checked all the wiring.

Borrowed a generic 72v controller the kind with the 3 speed switch and no display and self learning.

Worked fine on speed 1 and 2, but on speed 3 it would break up.

Since my geared hub has 5.8:1 ratio is it possible for the erpm to be to high for these controllers?
 
MCF said:
Went back through and checked all the wiring.

Borrowed a generic 72v controller the kind with the 3 speed switch and no display and self learning.

Worked fine on speed 1 and 2, but on speed 3 it would break up.

Since my geared hub has 5.8:1 ratio is it possible for the erpm to be to high for these controllers?

That's what everyone kept telling me. The thing is, my off the shelf 35a KT controller has been working just fine on my 1000w+ MAC12t geared hub for the last 5 years. It's working perfectly from wide open starts to speeds well over 30mph.

No experience with the 40a or the rest of your setup.
 
:bigthumb:
AHicks said:
That's what everyone kept telling me. The thing is, my off the shelf 35a KT controller has been working just fine on my 1000w+ MAC12t geared hub for the last 5 years. It's working perfectly from wide open starts to speeds well over 30mph.

No experience with the 40a or the rest of your setup.

That's the thing it worked fine with the 52v kt sine wave controller. Now with the 72v square wave controller it's being a pain.

Is your kt controller sine wave? I wonder if a sine wave version can handle the higher rpms better.
 
In case anyone runs into a similar problem. Apparently the MXUS xf19r at 72v does not play nice with a squarewave KT controller (presumably the RPM is higher than it can keep up with as its a 1.6:1 geared motor).

Replaced with a sinewave controller and everything is working.
 
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