Newbie on a home made ebike. Can't set controller.

Hey people. How are y'all?

New guy in here and also new to this home brew e-bike thing.
Have made a build but there's a lot I can't make heads or tails of. So... I'm wondering if anyone here could lend a hand.
And, yes, I HAVE done my searches :wink:

My build is like this:
Take one 4 years old, but extremely low milage MTB.
Buy a 1500W rear wheel hub motor kit from SCS in China.
Throw on a 52v 20ah battery pack.
When the sparks and smoke has lightened a bit, take it for a spin..
Ok, so it does about 55km/h.
And it seems to be working ok, how ever, there's a bunch of things that I can't wrap my head around.

In a little more detail the setup is like this:
The motor is a rear wheel, 1500w hub motor from SCS with theese numbers stamped into the motor housing: kt w-01 2005 1773.
The controller is a Kunteng KT48ZWSRKT-SJT02L.
The display is a Kunteng KT LCD8H.
The battery is a semi good chineese 52v 20ah triangle pack.
I have a PAS, regen active and a twist throttle.

And now for the things that puzzles me.
First, even with 52v, the max speed I get is only a measly 55km/h with a fully charged battery.
The thing that doesn't seem to make any kind of sense, is that when I reach 50 or so and start going down hill, the wattage going to the motor seems to be dropping, the faster I go. I can read the use on my display.
The faster downhill, the less wattage. All down to about 50-60 watt. So, obviously there's a limiter somewhere. In my head it says the controller is limiting the power output. Can I be right?

Second, it seems that the controller and display have a default setup like this:

It would seem to me that this is just a general 48v setup and nothing specific for the hub motor I have. Am I right?
How do I find out the correct settings to fit the motor I have? I have tried to google the number I find on the motor "kt w-01 2005 1773", but with no luck at all.
Does anyone have any info on this motor?

And third, the controller setup is now for a 48v battery. How do I set up my controller for 52v? To make sure I get the best utilisation possible from the 52v battery.
One more, identical 52v battery is now on its way here. I'm thinking to parallell connect the two, on order to increase the riding distance.

Some help would be greatly appreciated

Have a nice day, y'all.

I think your expectations are a little high. 34 mph is a respectable speed for that combination.
Wattage consumed drops when going down hill because the motor is not doing much work. If you are coasting at or above the top speed of the motor only a small amount of power is used.

Downhill, the gravity does replace some power. Soon you are going faster than your system speed (volt-kv-wheelsize), hence the low power use, that does eventually reach the no-load power. Then, if you apply regen, your system will show power produced instead of power consumed.

Try that uphill, where you have to overcome the gravity. The power will raise with speed, then stabilize when it can’t accelerate anymore.

To achieve faster top speed, you need higher voltage, or faster motor Kv, or different wheel size, and eventually more power.

Here's my guess you hit the limit of kv and or emf keeps it from taking more watts or it's at its saturation point. You will hit your speed limit and your wattage will go down after you reach the motor speed limit and when it hits its speed limit it is saturated and the amperage and wattage will go down even though you're at Max speed on flat land.
Maybe someone can clean up my message.

999zip999 said:

Here's my guess you hit the limit of kv and or emf keeps it from taking more watts or it's at its saturation point. You will hit your speed limit and your wattage will go down after you reach the motor speed limit and when it hits its speed limit it is saturated and the amperage and wattage will go down even though you're at Max speed on flat land.
Maybe someone can clean up my message.

Click to expand...

Thanks for answering.
You know, that does make a lot of sense. The way I think is that because I can't seem to get any information on the motor, it's also hard to set up the controller.
Also, I think that the default controller setup isn't optimal for the motor. So I'm thinking it should be possible to squeeze out a bit more in the top end by optimizing.
I guess that's what's bugging me the most, that I can't find out if the system itself are properly tuned.
Chasing those few extra km/h isn't really a big deal at all

Thanks a lot for answering, guys.
I see there was one piece of info I left out. My wheels are 26".

But I see the same wattage drop on flat ground too. When the speed reaches a bit above 50 km/h, the wattage drop. So there has to be a limiter somewhere.
I see when I go uphill, the power can go as high as 1950w and the speed only at about 35km/h.
But why don't it deliver max pover all the time? Until the power isn't enough to increase the speed anymore?
I know I'm kind of comparing to a low hp motorbike now, but...
How ever, what I have notices it that when I reach speeds above 50km/h, it takes a LOT of power for each km/h increased, due to the wind resistance.
I kind of wonder, has anyone else got the same setup as I have?

I think your expectations are a little high. 34 mph is a respectable speed for that combination.
Wattage consumed drops when going down hill because the motor is not doing much work. If you are coasting at or above the top speed of the motor only a small amount of power is used.

Click to expand...

Thanks, so you think thats a ok speed for a 52v? Or do you think the controller are set up for 48, and makes the bike perform as a 48v rather than 52?
Sorry if I'm asking some rather dumb questions here, guys

Raider said:

Also, I think that the default controller setup isn't optimal for the motor. So I'm thinking it should be possible to squeeze out a bit more in the top end by optimizing.
I guess that's what's bugging me the most, that I can't find out if the system itself are properly tuned.
Chasing those few extra km/h isn't really a big deal at all

Click to expand...

Not likely. Up to about 20mph, motor speed is proportional to voltage. Past 20mph, friction/air resistance increasingly becomes a factor. 35mph takes about 1700W to maintain. 40mph will take 2400W, mainly due to air resistance.

What are the ratings on the label of your controller? At 52V, the controller would need to supply around 30 amps to maintain 35mph. If your controller label says that it can provide more than 30A, then you have sufficient "power" to maintain a higher speed, but not the voltage to get there. So, chances are, no fiddling with settings is going to result in more speed. If your limitation is power, then you need to get a controller than can provide it, or modify the current one (e.g. shunt mod) to provide it. If your limitation is due to voltage, then you can increase the voltage of your pack, or get a controller than has flux/field weakening to get the extra speed.

Raider said:

But I see the same wattage drop on flat ground too. When the speed reaches a bit above 50 km/h, the wattage drop. So there has to be a limiter somewhere.

Click to expand...

Nope. Nothing to do with the controller. The motor will draw as much power as it needs, and spin as fast as the voltage applied to it. The speed "limiter" is the turn count of your motor.

E-HP said:

Raider said:

Also, I think that the default controller setup isn't optimal for the motor. So I'm thinking it should be possible to squeeze out a bit more in the top end by optimizing.
I guess that's what's bugging me the most, that I can't find out if the system itself are properly tuned.
Chasing those few extra km/h isn't really a big deal at all

Click to expand...

Not likely. Up to about 20mph, motor speed is proportional to voltage. Past 20mph, friction/air resistance increasingly becomes a factor. 35mph takes about 1700W to maintain. 40mph will take 2400W, mainly due to air resistance.

What are the ratings on the label of your controller? At 52V, the controller would need to supply around 30 amps to maintain 35mph. If your controller label says that it can provide more than 30A, then you have sufficient "power" to maintain a higher speed, but not the voltage to get there. So, chances are, no fiddling with settings is going to result in more speed. If your limitation is power, then you need to get a controller than can provide it, or modify the current one (e.g. shunt mod) to provide it. If your limitation is due to voltage, then you can increase the voltage of your pack, or get a controller than has flux/field weakening to get the extra speed.

Click to expand...

Thanks.
My controller can supply a max of 45A. So then, if I understand you correctly, the 52v from the battery are not enough to get any speeds faster than what I already have?
But then, down hill, when the controller slowly shuts down the power with increasing speed is because the motor has a limit to rpm?
Otherwise, the motor would go faster down hill when it don't have to draw as much power?
My max down hill speed has actually been as much as 60km/h, but then the controller didn't deliver more than a few W.

Or am I way out on left field again :wink:

But how can I tell if my controller is optimized to the motor and the battery I have? Other than not getting any information on the specifics of the motor being a problem, of course

Just as a side note.. Even when going up hill, drawing over 1700W, the motor never gets much warm. I don't have a temp sensor inside the motor, but it has never been more than luke warm to the touch.

Raider said:

My controller can supply a max of 45A. So then, if I understand you correctly, the 52v from the battery are not enough to get any speeds faster than what I already have?

But then, down hill, when the controller slowly shuts down the power with increasing speed is because the motor has a limit to rpm?
Otherwise, the motor would go faster down hill when it don't have to draw as much power?

But how can I tell if my controller is optimized to the motor and the battery I have? Other than not getting any information on the specifics of the motor being a problem, of course

Click to expand...

I suspect that's a max/peak value and not continuous. If the controller can provide 45A, and the current settings aren't set below that (C5=10), and the battery is also capable of supplying 45A as well (what's the BMS rated at?), then the factor limiting speed is voltage (the motor is designed for a certain speed, where back EMF and forward cancel). You can either increase the voltage, or if you have a controller that support it, apply field weakening (usually resulting in a 20% unloaded speed increase). The stock KT controllers don't support field weakening.

How your bike performs downhill can depend on how your controller works, and how you are using your throttle. On your KT controller, if you let go of the throttle, the bike will just coast, picking up speed with gravity. On my old KT controller, if I had the throttle just slightly on, it would slow the bike when going downhill, and regen watts back to the battery, even without using the brake/regen lever.

Since the controller is made to operate at 48V, the main things impacting your are that are the battery level display won't be accurate, and you lose the low voltage cutoff protection, when you run your battery too low. You have to just live with the former, but you can set the display to show voltage and monitor it that way. For the latter, even if you crank the LVC up per what's allowed in the settings (C12?), it won't be high enough to protect your battery, so you will be relying on the battery BMS, and monitoring your voltage.

Since it's not a sine wave controller, I believe the open source firmware route isn't an option, but even that wouldn't get you more speed, since field weakening isn't part of the build last time I looked. You do get FOC though, so maybe more efficient.

Well, my battery BMS are supposed to give out max 40A.
And the display measures the battery voltage correctly, saying a bit above 58v, I think 58.2, when the battery are fully charged.
Then, the cut off are set at 42v by the battery BMS. So luckilly, the BMS will protect the battery even if the controller are set at 40v cut off.

On my old KT controller, if I had the throttle just slightly on, it would slow the bike when going downhill, and regen watts back to the battery, even without using the brake/regen lever.

Click to expand...

Yes, my electric scooter works like that. When the speed exeeds the maximum speed set by the controller, typically down hill, the regen slows the scooter down.

Since the controller is made to operate at 48V, the main things impacting your are that are the battery level display won't be accurate, and you lose the low voltage cutoff protection, when you run your battery too low. You have to just live with the former, but you can set the display to show voltage and monitor it that way.

Click to expand...

Trust me, I know the battery level are a tiny bit wrong, lol.. I wasn't thinking and trusted that the level was a bit above 50% but from there it dropped very fast to about 42-43v and everything went totally black.. And I had a hilly 34 km left to get home..
Yes, I DID kick my self that time. Litterarely :lol:
So now I keep an eye on the voltage instead, since I know when darkness and disaster comes to my bike.
Going to be a LOT better when the second battery arrives.
Right now, I have a range of about 110km in hilly terrain with a average speed of about 31km/h and on assist 1 with the occational assist 2 up hill. Not too bad really, but on full throttle continously I have a range of only about 40km. Way little, especially if I drive in the dark so I also have to use lights.
In general I like to pedal a bit. Good exersice. I generally use assist 1, or 2 if it's a bit up hill. On 2 it gives about 800W of help, and on one on average 300-350. And an average speed slightly over 30km/h takes you quite far, quite fast.

So, all in all, I should be rather happy with the performance of the bike? It performs pretty much as one can expect from a 1500W, 52v system, you think? And you think that getting 52v batteries over 48 volt has increased the over all performance like it is supposed to?
Honestly, I wouldn't know the difference, since I've never tested a 48v. And my el. scooter is a 36v.
But 55km/h max speed isn't too bad I guess. I can stay with the traffic in the villages around here. And it's quite strong uphill too. 1950W and no slower than 32-35 km/h.
What I DO know is that it's a LOT better than the measly 250W motors that are the legal max here in norway. And max legal speed is 25 km/h. It's like a joke

Controller parameter settings can give you better acceleration or better efficiency, but very unlikely to give you better top speed. The exception is controllers that are field oriented, for field weakening can be set on those controllers to increase top speed.

Cheap controllers can be tricked and upgraded to feed more power, but the battery must be up to the task. Right now, your battery does supply 40A and your controller 45A. It is useless to upgrade the controller to higher power, until you have a battery that can feed more.

Even then, you won’t have better top speed, except for the situations when speed is limited by resistance: strong wind, steep hill, heavy load.

As I said previously, better top speed does require higher motor Kv, or higher voltage, or a different wheel size. Or, a combination of those factors.

MadRhino said:

Controller parameter settings can give you better acceleration or better efficiency, but very unlikely to give you better top speed. The exception is controllers that are field oriented, for field weakening can be set on those controllers to increase top speed.

Cheap controllers can be tricked and upgraded to feed more power, but the battery must be up to the task. Right now, your battery does supply 40A and your controller 45A. It is useless to upgrade the controller to higher power, until you have a battery that can feed more.

Even then, you won’t have better top speed, except for the situations when speed is limited by resistance: strong wind, steep hill, heavy load.

As I said previously, better top speed does require higher motor Kv, or higher voltage, or a different wheel size. Or, a combination of those factors.

Click to expand...

I see. Well, that top speed is not really a big deal.
And it was because the battery could deliver max 40A I chose the 18mosfet, 45A Kunteng controller. And so far, I have not had any kind of heat problems with that controller.
I did manage to fry the main chip, but that was more from being too much experimental. And repeating that is not on the agenda at the moment
Efficiency is much more important. And more accelration wouldn't be all bad either, I guess. And also, there is a limit to how much I want to spend on this. It's more like an experiment than anything else. Somerhing I've never done before and wanted to try. It's a lot of fun, though
But in order to set the most efficient controller parameters, I have to know the parameters for the motor, right? And that is something I cant find anywhere.
I wonder if anyone in here has the same motor. " kt w-01 2005 1773 ". Don't know what is what in that number, though.

Next, there's a couple of questions I have regarding building a light system for this bike. But thats for another thread. Where should I start that thread?

This controller can feed much more than its rating, it can be set to limit current, and easy to mod. The controller is not a problem, and the optimisation of the settings for your motor and battery. is mostly a matter of try snd error, even if you knew the exact motor parameters.

MadRhino said:

This controller can feed much more than its rating, it can be set to limit current, and easy to mod. The controller is not a problem, and the optimisation of the settings for your motor and battery. is mostly a matter of try snd error, even if you knew the exact motor parameters.

Click to expand...

I see. So basically I need to take a deep dive into the controller/display manual to try to understand the settings then.
I have a feeling that there's a limit to the optimization that can be done in the standard settings, though.
And someone else mentioned that a firmware mod was not really applicable for the KT48ZWSRKT-SJT02L controller.
But after frying one controller, I'm kind'a catious about frying another one.. I mean, the cloud of smoke can be entertaining and all, but the smell and the cost not so much. And I'm not much of a electro tech wiz.
So, by trial and error, can I make more smoke? Or are there enough fail safes built into the firmware to prevent that from happening.

The software is very primitive. Everything in this controller is simple, with minimal features and protections. This has some downsides of course, but it does make it very simple to mod and upgrade. Frying many cheap controllers IMO, is more instructive than frying one very expansive piece of technical mastership. There will always be trial and error in performance development. We have to find the limit, to know how close we can safely push the game.

Hey again.
Yeah, chineese mainland fabricated stuff are usually primitive and simple. As a matter of fact, in China, chineese would rather NOT buy stuff made in mainland China. Simply because they know the stuff produced are no good

Oh, well. After poking around a bit online, trying to get a grip on 48v vs 52v, torque and speeds I have actually got a feeling I'm getting a raw deal here. And my setup with a 1500w motor and a 52v battery should be both faster and stronger than it really is.
And, I have established that my motor have a "max" rpm at 470.
Now lets see.. Is that unloaded or loaded? I would say that is with the rear wheel in the air.
So. Calculate this.. Engine speed, 470, times wheel size, 26, times 0.008 for mph or 0.0048 for km/h That would give me as answer 58.6 km/h. Not too far from current speed at 55km/h.. Seems ok, right.. Wrong. That is with a 48v battery. To find out what the difference would be, calculate this: 48v speed, 58.565, times 52v, divided by 48v is.... 63.5.. THAT should be my 52 volt speed. With the increase in torque too..
And I have seen, time and time again, that my 52v setup are a lot weaker and slower than way too many others..
And that is annoying the crap out of me..
Anyone else in here who has kit from CSC? And KT controller with KT LCD8H display?
It's very clear that something is off kilter here. But what...
BTW, I am a rather light rider.. Only about 75kg.

If that 470 rpm figure is the unloaded speed, then the motor has to slow down below that to make any power at all. Peak power usually occurs at about half of the unloaded speed (and it often overheats your motor if you do it for very long).

Increasing the voltage of your battery increases the maximum power of your motor in direct proportion to the increase in voltage. Actually going that much faster requires power to increase in proportion to the square of the speed. Bottom line is, increasing voltage by (for instance) 25 percent, won't increase your speed by 25 percent.

Balmorhea said:

If that 470 rpm figure is the unloaded speed, then the motor has to slow down below that to make any power at all. Peak power usually occurs at about half of the unloaded speed (and it often overheats your motor if you do it for very long).

Increasing the voltage of your battery increases the maximum power of your motor in direct proportion to the increase in voltage. Actually going that much faster requires power to increase in proportion to the square of the speed. Bottom line is, increasing voltage by (for instance) 25 percent, won't increase your speed by 25 percent.

Click to expand...

Hello and thanks for your input
Yes, I rather think that all the numbers vendors are operating with are unloaded speeds. Anything to boast those numbers :lol:
So, you think that the calculation method I was given are more theoretical than real? Or plain wrong? I don't know anything much yet. Just trying to learn.
But the thing is still, from what I can actually SEE, my bike doesn't match most other 1500w, 52v setups. Most of them seem to be in the 38 to 40 mph range. And more torky too..
And I'm still stuck in the low 48v range..
My bike isn't that heavy either. Maybe a bit over 20kg. Max. Motor is 6.2 and batterypack is 5.2. And I run with about 50psi in my tires. Should be ok, I think.
Of course, now I'm going to add another 5.2kg when my second battery pack arrives. That might slow it down a bit, but I'll get MUCH more range.
My motor don't get much warm either. Even under heavy load going uphill and the controller giving it about 1950W. The most I've felt is about luke warm to the touch. About skin temperature, or a tiny bit more.
So, I'm still wondering. Why are my homebrew slower than the average. Even with the exact same battery, of the same brand.
I'll do some more testing once I get things back together. Right now I'm building in a custom LED lighting system. Brake lights and all. So there's parts all over.
And also, I am quite sure that the KT48ZWSRKT controller with the KT LCD8H display have a very default setup to match any 1500W 48V motor.

Most of those Chinese controllers are built around an Infineon board, that is Japanese. They had produced over the years a very large variety of controller solutions, and their older boards are sold very cheap in mass qty. The software does make the difference between crap and good ones. Nevertheless, some that are basically cheap crap can be mod to make very powerful and reliable controllers, when you don’t need any fancy features.

Did you actually hold your wheel up in the air and measure it, or just going off a datasheet number?

MadRhino said:

Most of those Chinese controllers are built around an Infineon board, that is Japanese. They had produced over the years a very large variety of controller solutions, and their older boards are sold very cheap in mass qty. The software does make the difference between crap and good ones. Nevertheless, some that are basically cheap crap can be mod to make very powerful and reliable controllers, when you don’t need any fancy features.

Click to expand...

Hmm.. So the KT48ZWSRKT-SJT02L would somewhat fall under the "cheap crap" category? No supprise there, really. It is after all produced in mainland China.
But this being my first ebike build I didn't want to fork out too much money in case I got easilly fed up with the whole thing.
Still isn't all that cheap, though. I think I'm over $1000 by now. Not including my extra battery pack, or the MTB itself.

For the other bikes and bike projects I have seen and can compare too, I've not seen what kind of controller they use. Or the "brand" of the motors. What I DO know, is that they also are some chineese stuff. Only the size and type of battery, which are the exact same as I have. And judging by their builds, the bike weights also seem to be the same..
Of course, what I don't know is if they have a strong wind helping them along
But yeah, I have also been thinking about software. How to read the software on the controller, how to verify that it has the best possible setup for 52v, and how to modify.
None of the other comparable bike builds seems to have been modified, though. Several of them are just put together and test driven.
I don't think I need too mych fancy stuff. Mine has a cruise, regen from the brake handles, pedal assist and a throttle. All I need, really. Maybe except the cruise. And a completely useless light system built in. Can't ever use that circuit to drive a relay. Put's out 70mA I think.
But I'll try to get it all back together this weekend and do some more test riding.
Also, in the menu system of the KT LCD8H there are a lot of settings I have no idea what means. Or does.
So, basically, I'm thinking that since the controller settings are default 48v that is where I should start. To verify that the settings in there are optimal for 52v, ( don't think they are ) and change them to the best possible settings.
For me, that is the most logical place to start. Optimize what I have before starting to throw more money at it. I'm not looking for a racer, just the best possible optimization of the battery power I have.

Voltron said:

Did you actually hold your wheel up in the air and measure it, or just going off a datasheet number?

Click to expand...

What little data sheet info I have been able to find on this motor, basically only wattage and RPM I'm fully aware that the rpm can be overblown. That's usually the case from any vendor.
I have run it unloaded at some point, but I cant remember the km/h reading. And I have no way to read the RPM.
What I DO know is what I have tried myself.
Max wattage delivered to the motor, about 1950W (34-35km/h), on a steep uphill piece of road, and the absolute max speed on a flat road, with little to no wind and battery at a 100% was 54-55 km/h. 34mph.
But I'll do another unloaded test to check speed after I'm done connecting my dual batteries.

I use something like this... So cheap, like under $12. Comes with reflective tape to bounce the laser back... Ending up using it a bunch on figuring out the kv on random unlaced motors.

Thanks. I'll see what I can find here in Norway. Not that price, that's for sure
Norway is one of the shittiest and most expensive contries in the world.
From what I understand, the rpm will also increase a little from 48 to 52V.

But there's another little thing too..
I have noticed something weird when I apply throttle to the bike.
About 50% ot the time, when I start to apply throttle, the power skips for a fraction of a second. Then goes on. Like it is a snap disconnect and reconnect. No blinking of the display, though. Just that little hickup.
Compare it with a bicycle when you have the chain skip a tooth. That's what it feels like.
What could that be?
And it's the same regardless of battery charge. It's annoying.

If it's the controller playing up, it should be different now since I have replaced the controller, but that remains to be seen.
Right now I've just finished rebuilding my battery cases to be able to attach them side by side on the bike, but still have the chance to charge each battery separately. and, man, that thing feels heavy. 10.4 kg. But at least I'll have 40ah now. A lot longer range.

BTW. Tp something completely unrelated.
I don't live in Norway longer, really. I now live in SE Asia for most of the year. I'm only here in Norway for about 3 months every year.
What should I do with the batteries in my ebike and e-scooter when I put it in storage for 9ish months at a time. Disconnect them and charge them up to about 60% and leave them?