Is the replacement motor a PM motor or does it have a wound field? That makes a difference on how it gets connected and also the efficiency.
And please consider the option of a switch bypassing the control unit at maximum speed. That would protect the power transistors very well.

 

dendad,

I found a clear picture

 

MisterBill2,

I did not take the motor apart but I think the motor case just holds magnets and no windings, I believe it's a PM motor.

Is the replacement motor a PM motor or does it have a wound field? That makes a difference on how it gets connected and also the efficiency.
And please consider the option of a switch bypassing the control unit at maximum speed. That would protect the power transistors very well.

 

dendad,

I do not have the replacement Mosfets yet so testing with bulbs won't work for now

Stephen

Yes, indeed.
You can check the current limiting is working while running the motor on no load, then lower the current limiting ref volts with a resistor to see if the motor slows.

Can you please post a clear picture of the top and the bottom of the board as I'm trying to validate the circuit. There are some problems with it as shown.
EDIT: I have found a few more pictures, but a hi res one would help.

 

MisterBill2,

No I don't ride this thing, even as a clown car joke, The girl is 9 years old. I don't think I still have a oscilloscope I did 19 years ago somewhere, I moved twice since then, will take a look. The throttle is a 0-4 volt 3 wire type standard for these type controllers, probably is just a pot.
I think it actually is a 3 wire hall effect type throttle that outputs 0.8 -4.3 volts with a 5 volt supply it gets from the controller.

Stephen

OK, I was not certain that it was a kid's 4 wheeler. But the specifications now point to another non-electrical possibility, which is the disk brake. If that somehow sticks then certainly the load will be a lot greater. And since I have been bothered by sticking disk brakes many times on many vehicles I suggest investigating that possibility.
And I did not realize that the person in the picture was not the TS. I do not make presumptions about people based on their appearance. She could be a petite 15 year old genius writing here.
My 5 year old nephew has a tractor of a similar class , but it has two lead/acid gell cells and a High/low speed selector and the "go" pedal is a switch.
One option with your vehicle could be a switch engaged near full speed that bypasses the speed controller and provides a direct battery connection. That would allow smooth starts and slightly faster speeds and totally bypass the controller for the higher current operation. That might not even require a relay yo do the switching, unless the electrical part of the control is in the handlebars. Or is that a push/pull cable operating a variable resistor inside the unit?

 

It might be worth adding a reverse-biased beefy Schottky diode (>24V rated) between the drain and source terminals of the FETs, to assist the FET body diodes to clamp any negative going voltage spikes when the motor sparks or over-runs, and perhaps another reverse-biased Schottky across the battery terminals.
Does the motor have any suppression components wired directly to its terminals and casing?

 

OK, so the mtor does not have the field connections shown in that circuit drawing. That improves the efficiency and makes controlling easier. The fact that the throttle control is an electronic arrangement makes the controller bypass option a lot more complex. If it were a standard motorcycle mechanical cable driving an electrical controller inside it would be simple to add a controller bypass switch that removed the load from the control transducers at full speed. That might still be an option but it is not so simple as I had hoped.

 

This looks potentially useful, maybe Rev C of your controller with links to what looks to be similar versions for sale for only a few bucks. Some claim 800w, maybe going to a 60% beefier controller contribute to longer life?

https://usefulldata.com/yiyun-yk31c-controller-brush-motor-review-manual/#2

 

Alec,

No the only thing is two wires coming out of the motor and no brush spark or other supression.

Stephen

It might be worth adding a reverse-biased beefy Schottky diode (>24V rated) between the drain and source terminals of the FETs, to assist the FET body diodes to clamp any negative going voltage spikes when the motor sparks or over-runs, and perhaps another reverse-biased Schottky across the battery terminals.
Does the motor have any suppression components wired directly to its terminals and casing?

 

MrSoftware,

Following that thought I have burned out 1 motor and two controllers so far. The over current solution with these controllers obviously is set too low or just doesn't work, also from what I've read Mosfets are sensative and don't like voltage spikes. I guess a good quality Zener Diode could protect the Mosfets, I'm not sure. The Mosfets always burn up under load in my case or maybe deceleration ? Asking a 9 year old these details it's hard to get an answer! mostly just get "aww, dad why is my ATV smoking?"

Stephen

This looks potentially useful, maybe Rev C of your controller with links to what looks to be similar versions for sale for only a few bucks. Some claim 800w, maybe going to a 60% beefier controller contribute to longer life?

https://usefulldata.com/yiyun-yk31c-controller-brush-motor-review-manual/#2

 

MrSoftware,

Thanks, I left a comment at that website, waiting for an update

Stephen

This looks potentially useful, maybe Rev C of your controller with links to what looks to be similar versions for sale for only a few bucks. Some claim 800w, maybe going to a 60% beefier controller contribute to longer life?

https://usefulldata.com/yiyun-yk31c-controller-brush-motor-review-manual/#2

 

Does your 9-year old mostly drive at full speed? If that is the case then an analog signal actuated bypass relay may solve the problem.
And another option might be a thermostat on the heat sink to slow things down when the drive gets to warm. That could be a fully automatic function , either dropping the speed control voltage or just switching in a resistance in series with the motor power.

 

MisterBill2,

if you were a 9 year old what would you do? mostly full throttle. I'm guessing the failure is the random triggering of the gates on the FETs or that the gates are not triggered completely thus generating too much heat. Just a theory but controller was used for 90 hours without incident. This was not an immediate failure maybe that's why the controller design was considered a success by YIYUN. Also the FETs may be poor quality and just failed. The replacement Mosfets are NTE2996 description: MSFET-PWR N CH 60V 84A to replace the original Mosfet:
SIN6812 description: N-Channel Enhancement Mode Field Effect Transistor www.szmeilai.com 80A Typ General Features 1 Description: The SIN6812 is a new generation of middle voltage and high current N–Channel enhancement mode trench power MOSFET. High avalanche energy, 100% test Fully characterized avalanche voltage Application: Power switching application Absolute Maximum Ratings M Units te Parameter ax. ID@Tc=25ْ C Continuous drain current,VGS@10V 80 ID@Tc=100ْC Continuous drain current,VGS@10V 53 IDM Pul ① 200 A sed drain current Power dissipation 156 W

Stephen

Does your 9-year old mostly drive at full speed? If that is the case then an analog signal actuated bypass relay may solve the problem.
And another option might be a thermostat on the heat sink to slow things down when the drive gets to warm. That could be a fully automatic function , either dropping the speed control voltage or just switching in a resistance in series with the motor power.

 

OK, if most of the driving is at full speed then one solution is a bypass relay operated when the speed control is at maximum. That could be either a small switch attached to the control, or an electronic circuit with a comparator to operate the relay when full speed is set. With the FETs bypassed at full speed there should not be any more failures. That fix, either version, will solve the controller failure problem.

 

Why are you wanting to control the current at all? If your thinking that will control the top speed, it won't, it is going to do what your seeing, burning out the controller. The motor is going to draw only the current/amps it needs, so find the highest amp rated controller you can get.

Trying to strictly match controller to motor using the specs found for these things is going to drive you crazy. Googling the model numbers in the first post give so many varied answers, some from even the same seller.

 

Why are you wanting to control the current at all? If your thinking that will control the top speed, it won't, it is going to do what your seeing, burning out the controller. The motor is going to draw only the current/amps it needs, so find the highest amp rated controller you can get.

Trying to strictly match controller to motor using the specs found for these things is going to drive you crazy. Googling the model numbers in the first post give so many varied answers, some from even the same seller.

shortbus,

I have been trying that route and end up chasing my tail with various failures. First the controller then the motor, now the controller again, what next a battery fire? this is a toy and not a commuter vehicle (thank God) The design works fine for speed and power, just not reliably, that is my issue. Buying endless parts is not going to solve my problem, when the over all design has a flaw in it. I am not alone with this problem, making and selling these parts is an enterprise of it's own. I want to control the current to save the motor, controller and battery from self destruction. using the battery or the controller as a limiting resistor only creates smoke and fire! The design must be safe and reliable.

 

Alec,

I think there is already Schottky diodes used listed as T1 and T2. The part number on those is JILIN SINO-MICROELECTRONICS CO, LTD
FHP20100 Schottky barrier diode

It might be worth adding a reverse-biased beefy Schottky diode (>24V rated) between the drain and source terminals of the FETs, to assist the FET body diodes to clamp any negative going voltage spikes when the motor sparks or over-runs, and perhaps another reverse-biased Schottky across the battery terminals.
Does the motor have any suppression components wired directly to its terminals and casing?

 

Does my suggestion about bypassing the transistors completely at max speed seem reasonable to anybody? That is what some of the bigger industrial soft starters do. The motor current is limited to only the rated level until the motor gets up to speed, then the series devices are bypassed by a less expensive contactor that does not need to handle the across-the-line inrush current. The soft-starters save a lot of power plus they save a lot of brutal torque spikes, and they extend the motor life a whole lot. And for a 100HP motor that matters a bit.
So for this small 4-wheeler vehicle the same principle would take the heaviest and longest duration loads off of the transistors.

 

I harp back to the need to get the current limiting working reliably.
Obviously, it is not. That is #1 priority in my opinion.
If you bypass the motor controller then you also bypass the protection, but a fuse or circuit breaker will need to be added, as it should be anyway.

 

MisterBill2,

That is an interesting solution but it adds complexity to the existing design. The Mosfets are burning up almost arbitrarily. Something like brush spikes, emf noise or the circuit itself seems to be driving the Mosfets to be over driven and to self destruction with nothing that stops them from burning up, at least that's my interpretation of the events witnessed. Obviously I need an ammeter, a test rig and possibly an oscilloscope and a thermocouple to figure out what is actually happening before I can postulate a scientific solution. I was hoping that someone who has spent possibly 100s of hours doing this for a living could steer me with a cap or inductor to put in the right spot to solve my problems. This is a hobby for me and I do not design control systems.

Stephen

Does my suggestion about bypassing the transistors completely at max speed seem reasonable to anybody? That is what some of the bigger industrial soft starters do. The motor current is limited to only the rated level until the motor gets up to speed, then the series devices are bypassed by a less expensive contactor that does not need to handle the across-the-line inrush current. The soft-starters save a lot of power plus they save a lot of brutal torque spikes, and they extend the motor life a whole lot. And for a 100HP motor that matters a bit.
So for this small 4-wheeler vehicle the same principle would take the heaviest and longest duration loads off of the transistors.