Unsolvable gremlin. Odd issue that persists regardless of replication.

[double_wide_suprise]

Hello everyone at Endless-Sphere. Just wanted to say first and foremost how much I appreciate all of you for the knowledge that I have been able to gain just from reading through threads. I thought it was a good time to make my first post with an issue that I’ve been dealing with for almost a YEAR. I’m copying this post from a FB group as it’s a little long to re type out since I got no luck there. And it’s worth reading. I’m not inexperienced either in electronics or the sort. If anything this is more of my wheelhouse as I work with brushless motors a lot and build packs.

Something to note that may be the issue is either throttle and issues with the hall, or what I truly think it is is the joining harness that connects both controllers as “one” also on my brand of “5600w” Chinese scooter, the stock controllers are yunli, and do not have markings dictating an master or slave controller. And I proved this by swapping as you will
Read.

Post:

I bought this scooter a little under a year ago. It’s relatively the same as all the other “China” scooters. You can find this same frame and layout under many different names. It’s a 60v 5600w dual motor variant like most 1500$+ models. It comes with the same generic 60v 45A controllers with a harness to join them.

Thought I’d put that description out there for reference. To possibly help. Also im electronically inclined, and knew buying one of these was going to take a lot of DIY for maintence and diagnosis which is no problem as i am particularly experienced in BLDC motors and comteollers. And i like to think im fairly inclined in sourcing parts and schematics given these things are a PITA to find info on. Searching through aliexpress takes a language in itself lol. Even with my pretty extensive background, im STILL stumped on this issue. But with that said, any kind of ideas you guys might have, I’m not afraid to try and throw my meter on.

My issue is regarding throttle response. Particularly in single motor mode. And this issue persists through all 3 gears. (My model only has the three gear option). If I give it full throttle from a dead stop, the acceleration is very hesitant and “jerk” like. Not violent but almost like a car with misfiring issues. Best way I can describe it is like I’m metering my throttle back and forth from full the half. And continues this kind of “jerk” motion till it reaches speed of whatever gear I’m in. And to add the acceleration is very weak. Even in gear 2/3. It’s the same for all three.

Here is the weird part, when I put it into dual mode, it’s totally different. The scooter responds way differently and accelerates WAY better. But I notice the front motor seems to get more power. It will actually lose traction and such because the power is so much. And I can tell the rear motor is giving more power but still, the front motor is putting out way more power. Now this may be all in my head as more weight is on the rear motor but worth putting out there.

So naturally I tried a couple different things, first I was able to warranty a brand new motor. So I installed that. Then to try and prove my point more, I swapped the controllers around to change what’s controlling what. So I changed I moved the controller that was originally controlling the front to the rear, and vise versa. I did this to see if maybe it’s one of the controllers acting up.

So, brand new rear motor, controllers swapped around. All “P” setting correctly set in my throttle. (TF-100 type), hall wires and everything connected correctly, and a new learn procedure for the motors. Should at least prove my theory that the controller giving power to the front originally was performing better right? Wrong. Same thing. Rear motor seriously lacking in power no matter what, and very hesitant acceleration.

So the only thing I can think may be causing this is either, the harness that connects the two controllers into “one”, power is actually limited to the rear in single mode, or my throttle is acting up. Maybe the hall sensors inside the wiper or something.

I’ve dealt with this since only a month after getting it. Every thing else is great, it’s just I would actually like to be able to use single motor mode from time to time because right now it’s not really that usable.

Sorry for such a long post but the details are important.

 

[amberwolf]

Given that dual mode, which should use more power, doesn't cause the problem, it should eliminate the battery and the connectiosn from the battery to the controllers. But you can measure the voltage at each controller's battery input connection during various testing and see if it changes how much voltage drops under different conditions.

But if just one controller (either one) has t he problem (with either motor), it could be crappy firmware design. If the controller draws a certain amount of current, but the motor isn't spinning as fast as the controller thinks it should be for that much current, the controller then shuts down the motor thinking there's a problem. Then it immediately retries because it's still being commanded to by the throttle. If it happens less at lower throttle amounts or with less load on the motor, that's even more of an indication of this problem.


The "best" way to fix that is to replace the controllers with a type that either has better firmware design or gives the user more programming control over exactly what happens in various situations (none of them give total control); Phaserunner, VESC, etc.




The front/rear "imbalance" is almost certainly just weight distribution. Most of those scooters have identical front and rear wheels so you can swap them, and you've already swapped controllers, so you could also swap the wiring harness so the front wiring goes to the rear and rear to front, just to completely eliminate that...but I don't think that's necessary; I think it's just the weight imbalance.

A properly designed 2wd setup should allocate more power to the more loaded wheel (dynamically if possible, but that's a lot more complex, and probably only going to be seen on DIY systems). That can help reduce wheel slip (really eliminating it also is complex).

 

[double_wide_suprise]

Given that dual mode, which should use more power, doesn't cause the problem, it should eliminate the battery and the connectiosn from the battery to the controllers. But you can measure the voltage at each controller's battery input connection during various testing and see if it changes how much voltage drops under different conditions.

But if just one controller (either one) has t he problem (with either motor), it could be crappy firmware design. If the controller draws a certain amount of current, but the motor isn't spinning as fast as the controller thinks it should be for that much current, the controller then shuts down the motor thinking there's a problem. Then it immediately retries because it's still being commanded to by the throttle. If it happens less at lower throttle amounts or with less load on the motor, that's even more of an indication of this problem.


The "best" way to fix that is to replace the controllers with a type that either has better firmware design or gives the user more programming control over exactly what happens in various situations (none of them give total control); Phaserunner, VESC, etc.




The front/rear "imbalance" is almost certainly just weight distribution. Most of those scooters have identical front and rear wheels so you can swap them, and you've already swapped controllers, so you could also swap the wiring harness so the front wiring goes to the rear and rear to front, just to completely eliminate that...but I don't think that's necessary; I think it's just the weight imbalance.

A properly designed 2wd setup should allocate more power to the more loaded wheel (dynamically if possible, but that's a lot more complex, and probably only going to be seen on DIY systems). That can help reduce wheel slip (really eliminating it also is complex).

I very much appreciate your concise reply, you have been the most helpful yet. I’m starting to kind of believe the same that it is just cheap hardware and firmware mixed with a rats nest of wires.

One thing I do want to comment on, you make a great point about weight distribution, and how the front wheel will always have less weight. But this is something that I still believe is not quite right with my scooter. Because I tested different scenarios, redistributing weight. If I put my scooter on its stand (wheels off ground) and hit the throttle, both wheels will spin at pretty much the same speed. But the minute they hit the ground, the rear motor very much has significantly less torque. I’ve done a couple tests and really loose fine gravel, with an even load spread to both wheels, and even tested it with more load on the front wheel. And still it out performs of the rear.

I know that there is not going to be nearly the same amount of power going to the rear motor in single mode. My issue is that the power is so lackluster. Even though is only one “one” motor. It’s still a 60v 3000w motor. It should at least have some “umpf” but it has zero. Very little pick up. And thenonly
Difference I can create is between gear 1 and 2. There is a very slight bump in torque but I mean hardly any. And between 2 and 3 there is zero difference aside from the top speed difference. I’ve ridden 500w scooters with more get up than my scooter in single mode with its 3000w motor.

Weight distribution definitely has a factor like you said but something just ain’t right.

I will eventually be going to a vesc because that’s the best way to go of course but can’t do that at the moment. What are my options?

I was thinking about deleting most of the wiring (lights etc) and making my own joining harness. Throttle to controllers, split signal in parallel to the controllers etc. seen a couple guys do this, almost to the point of just wiring it where it’s permanently in single mode. Thoughts?

 

[amberwolf]

The front vs rear torque issue can be isolated to the real cause by the method previously described.

Making your own wiring harness that isolates the two systems from each other, with only throttle and battery and ebrake lever in common, would also do this. If you do, make sure you don't connect the 5v of both controllers to the throttle/ebrake, only use the groudn and the signal from one of them, and use all three from the other. (some brake levers only ahve two, as long as they are not 5v just singal and ground then youc an connect both to both controllers).

If you have to use a display with them to make them work as desired, you'd need to either switch between the two, or have the display's tx output line connect to boht controllers' rx input lines, but only one controllers' tx output line to the display's rx input line. (otherwise the display can't get valid data; it's even possible with a poor tx out buffer design to damage that line on boht controllers by connecting them together).

Also remember that autolearn on controllers ins't perfect, so it can come up with a false positive, causing incorrect motor behavior.