Ninja 250 "Clone" Made in China

[Dui ni shuo de dui]

Thanks for your info. I will be using contactor-controlled BMS (bypassing the BMS for discharge, but not for charge), so basically I just need something that has completely reliable LVC and HVC. Maybe balance too (it balances, right? As far as I can tell from Aliexpress page descriptions I am able to get some ANT models with active balance). I won't be using SOC, display, discharge current, ect.

A friend made experiments on using contactors and they weren't conclusive. The contactors tended to fail in a closed position, which entirely defeated their purpose (well known automotive brand contactors). I thought about using contactors before but decided against it for this reason.

As far as I know the ANT does passive balancing at 200mA per cell. It works well enough, I really don't think active balancing does much of a difference, the cells have stayed very much in balance for the past 6 years already so passive balancing seems to be more than enough.

The little display that comes with it is actually very nice, it does pretty much everything you could need. I integrated it in the dashboard of all my bikes, it works great.

 

[dominik h]

With well matched cells passive balancing with 200mA is enough.
The company I work sells Li-NMC batteries 160S250Ah with a passive balancing BMS with only 100mA current. The first ones have already done 5000 60% cycles, and now the BMS needs a little longer to get the cells to the same level, but it is still working fine.
You only need higher balancing current , when you have not well matched cells.

 

[harrisonpatm]

I don't leave balance on. I agree with both of you: well-matched cells don't need to be constantly balanced. I just would prefer the bms to have balance function available, for the 1-2 times per year I top balance.

 

[Dui ni shuo de dui]

Great news, I was able to find a longer road for top speed tests, so far it seems like the bike reaches exactly 150km/h (93mph)
The motor temperature didn't go over 82C, so that means it can probably take more power and go faster.

But to be honest 150 is already enough, I don't think it would be reasonable to go much faster with this lightweight frame.
I still have a little bit of tuning to do to the controller in order to get the best possible performance.

 

[Chalo]

Great news, I was able to find a longer road for top speed tests, so far it seems like the bike reaches exactly 150km/h (93mph)

That's very impressive.

My bike would need about 25 times as much power to go that fast as it does at its 52 km/h flat ground top speed.

 

[dominik h]

Great news, I was able to find a longer road for top speed tests, so far it seems like the bike reaches exactly 150km/h (93mph)
The motor temperature didn't go over 82C, so that means it can probably take more power and go faster.

I think 25kw are needed to reach that speed. Did you check the current draw or the amps from the battery at top speed?

 

[Dui ni shuo de dui]

I think 25kw are needed to reach that speed. Did you check the current draw or the amps from the battery at top speed?

I didn't check as unfortunately I made a modification on my BMS current sensor, so it is not accurate anymore. I'm lazy to correct it because I need to remove a lot of stuff to access the BMS. Now that I think about it I think it's possible to adjust/recalibrate the current reading in the app, maybe I'll try that instead.

Also I was a bit busy looking at the road ahead, haha

 

[j bjork]

I think a screen record of the phone while connected to the controller could give an idea.
Yes, it is not easy to look at a screen while going fast or accelerating fast

 

[harrisonpatm]

I think a screen record of the phone while connected to the controller could give an idea.
Yes, it is not easy to look at a screen while going fast or accelerating fast

(off topic) Tell that to whatever moron designed the interior of the Cybertruck. The giant touchscreen display is the only info that the driver has, and it requires you to look downwards and to the right while driving to see speed, battery life, ect...

 

[Dui ni shuo de dui]

I think a screen record of the phone while connected to the controller could give an idea.
Yes, it is not easy to look at a screen while going fast or accelerating fast

The problem is that the bluetooth on my phone is toast, I can barely connect for 2 seconds before it loses connection.
But the good news is that yesterday I just found an old phone that has a working bluetooth and was able to get the fardriver app working on it, so now that should be possible.
I think I'll need to work on a telemetry system at some point. I'd also ike to add some cameras to be able to record videos. Not 100% sure I'm gonna do it because I have other projects to work on, but I'm thinking about it.

 

[dominik h]

After switching the fardriver on, it does record for 50 Seconds in a chart, that should be enough to reach top speed
It records
Amps
Throotle
Weakening Field
Motor RPM

 

[Dui ni shuo de dui]

After switching the fardriver on, it does record for 50 Seconds in a chart, that should be enough to reach top speed
It records
Amps
Throotle
Weakening Field
Motor RPM

Problem is that those graphs are barely readable, at least on my phone the way they're displayed is pretty much useless.
Even on the screenshot you posted I can't really say what's what... like what's the green line representing? how come there are two sky blue lines superposed? What's the purple line? What's the scale? Are they talking about phase current of battery current? On the graph you posted I'm incapable of telling what was the maximum current reached.
It's even worse on my phone, I think there are some display bugs.

 

[dominik h]

I do not know what the green line is for , there are two sky blue lines because the I did not stop after 50 second, probably you can widen the graph and see also 2 minutes or more, but the manual says 50 seconds.
in the first 5 seconds you see the battery current (sky blue line starting at zero) rise to 400A (8x50a).
In the second 5 Seconds you see the current is dropping , as I rechead 100kph where I lowered the current in the controller settings. Speed is in ERPM. I have disabled weakening field, so you don´t see any chnages in the turquoise line, otherwhise you would see a 0 when fw is not activated and 1 when fw is need to be activated, the graph shows FW only when the throotle is closed, I think this is a reminder for the controller, and helps to not kill the mosfets with overvoltage. Black line is battery voltage.

Above a graph with the old 5kw motor and the ND72680, battery current setting was 280A, there I stopped after 50 seconds.

 

[Dui ni shuo de dui]

The rear brake of my bike always made a little scratching noise when riding at low speed. I always assumed it was my rotor that was slightly warped and didn't really bother solving the issue, since it wasn't dragging the wheel, it was just making some slight sounds at low speeds. But still, since the motorcycle is completely silent this always bothered me a little as it sounded a bit like a cheap tractor.

A few days ago I tried fitting another disk which I knew was perfectly straight.
Well it turned out to be even worse. Weird.
I took it out and measured the runout at the flange, and it was completely out of whack!
Turns out it has to do with the side cover, either it hasn't been machined correctly or it got misaligned somehow.

As I didn't have a big enough lathe to fit the cover, I though about a very sketchy method: using the motor itself as the lathe.
I used a zip tie on the accelerator to set the motor to the lowest speed I could. Braking it by rubbing my feet on the tire to keep a consistent speed.
Then I used a wood chisel to carve the flange to get rid of the runout as best I could, kinda the same way they carve wooden bowls in youtube videos.

That was super sketchy and really dangerous, even at low speed the motor has some tremendous force, I absolutely don't recommend anyone to do that, especially if you have no experience with a lathe. And doing it with the motor running at anything more than 60rpm would be suicidal.

That being said, it worked really well, now the brake rotor has zero wobble, which makes the brake power more consistent and I got rid of the noise entirely. Best of all, I didn't even lose a single finger in the process!

 

[A-DamW]

Nice work! I like this kind of out-of-the-box thinking, as a note, you can use something like an angle grinder instead of a chisel, much less overall force required.
I have some 20mm steel motor shafts I am going to reduce to 3/4" by spinning in place against an abrasive wheel.

 

[dominik h]

I took it out and measured the runout at the flange, and it was completely out of whack

My new QS72V10000W motor has the same problem, the two older ones did not had this issue.

That being said, it worked really well, now the brake rotor has zero wobble, which makes the brake power more consistent and I got rid of the noise entirely. Best of all, I didn't even lose a single finger in the process!

Nice idea how you solved this. Don´t know if I have enough experience for your solution,
I will try it with the angle grinder first.

 

[Dui ni shuo de dui]

My new QS72V10000W motor has the same problem, the two older ones did not had this issue.


Nice idea how you solved this. Don´t know if I have enough experience for your solution,
I will try it with the angle grinder first.

Yes, the angle grinder technique is undoubdtedly a lot safer. But I'm used to the lathe so I thought I could be a little more precise with the chisel. Also I was afraid to take too much material too quickly.
If you do this, really I insist on never getting the wheel spinning over 60rpm, it doesn't seem like it but it can rip off a finger without breaking a sweat.
If you're not shitting yourself the entire time then you're doing it wrong!

 

[Dui ni shuo de dui]

Small update, I pushed the phase amps to 950A.
Still working great, the motor heats a little bit more but it is still very much manageable so far. The heat rises slowly, but once its hot it takes a very long time to cool down, so maybe I'll add a bit of statorade someday.
The bike is very snappy, the rear tire is having a harder time sticking to the ground if the road isn't perfectly dry.

I think it can be pushed a little bit higher, I'll keep increasing the power slowly, maybe once a week, and monitor the bike's behavior.

Now that I found an old phone with a stable bluetooth it makes tuning a whole lot easier.
Still need to build some kind of support for it, so I can take measurements while riding.

 

[Eastwood]

Small update, I pushed the phase amps to 950A.

I say the more power and acceleration the better! As long as the motor can shed the heat, why not right!

Do you ever ride in wet conditions?
If you don’t, you could consider modifying the side plates with holes and using some type of screen or filter. I’ve always wanted to put fans in a hub motor with intake and exhaust holes for a street setup that doesn’t see rain. But yeah, even without fans, large holes that could allow airflow would be the best cooling technique besides water cooled motors.

Then, on the other hand talking about statoraid… It would help you greatly because of the mass of your hub motor. I wonder if the regular QS 273 hub motor fins could fit your motor or maybe some custom made heat sinks? I’m guessing you have a temperature sensor installed in the hub motor?

 

[Dui ni shuo de dui]

Do you ever ride in wet conditions?

Yeah, the bike is my daily, and it often rains here.
I even rode it in snow, took a while to get to work that day haha

If you don’t, you could consider modifying the side plates with holes and using some type of screen or filter. I’ve always wanted to put fans in a hub motor with intake and exhaust holes for a street setup that doesn’t see rain. But yeah, even without fans, large holes that could allow airflow would be the best cooling technique besides water cooled motors.

Indeed it would be nice but I really can't do that here, the laminations would rust in just a few days

Then, on the other hand talking about statoraid… It would help you greatly because of the mass of your hub motor. I wonder if the regular QS 273 hub motor fins could fit your motor or maybe some custom made heat sinks?

Yes, I used statoraid on the 3KW motor. This motor seemed to dissipate heat faster, but it was heating more in the first place because it was just a 3KW.
The problem with statoraid is I worry about the magnets, because they become the primary path for heat. Magnets have a lower temperature rating than coils, it could lead to a loss of torque if they ever get damaged.
For now I'll try without for a little while, but I'll experiment again with it in a near future.

Heat sinks would look a bit ugly in my opinion, so I'll try to avoid it. If I really were to have cooling issue I'd directly go for watercooling, as it's mostly a matter of making a custom side cover to fit a larger bearing.

I’m guessing you have a temperature sensor installed in the hub motor?

Yes, I installed another barbecue sensor in it so it still works with the dashboard screen display.