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My first High Speed crash ever and it was on the S22


Rawnei

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3 hours ago, Student4Life said:

fail with a reduced-but-not-zero power output mode.

You'll probably still end up on your face. Maybe not, but if you're leaning and it reduces power it's going to be a tough save. But personally, I always thought a gentle tilt forward (pedal dip) when you're approaching cutout would be more effective than tilt back... you'll def need to get used to it, but my reaction to pedal dip is to slow tf down, right now. There's a real temptation to try to power though tilt back that I don't think will be there if you're 3° tilted forward. Tilt forward won't reduce power demand BTW, maybe for an instant but then it has to try to balance you again.

Edited by Tawpie
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3 hours ago, Student4Life said:

My understanding is that the Battery Management Controller is prioritizing the battery and wiring and motor at the expense of rider safety

These 

3 hours ago, Student4Life said:

hard acceleration from a dead stop

lead easily to an overlean. No matter if one rides some antique 2017 wheel or a new high(er) power wheel.

It's not really 

3 hours ago, Student4Life said:

about system (battery, motor, controller) over-current

It's the combination of speed and burden.

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On 1/1/2023 at 3:28 AM, Tawpie said:

Tilt forward won't reduce power demand BTW, maybe for an instant but then it has to try to balance you again.

That’s the part of the suggested tilt-forward that gives me the shills. Since  you’re already leaning forward, a tilt-forward would inevitably increase the lean until the rider reacts, and recovering from it would take more power than a mere tilt-back in the first place, which doesn’t take more power than what it would take to start braking at that time anyway. 

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13 hours ago, mrelwood said:

That’s the part of the suggested tilt-forward that gives me the shills. Since  you’re already leaning forward, a tilt-forward would inevitably increase the lean until the rider reacts, and recovering from it would take more power than a mere tilt-back in the first place, which doesn’t take more power than what it would take to start braking at that time anyway. 

Having the option to adjust the tilt-back/tilt-forward behavior on an app would be amazing. True customization of safety features. 

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I wouldn't mind the option, but I think the tiltback as it is on the 18 XL is pretty good. I pretty much push the wheel's capabilities to the limit, but there have also been times when I misjudged the battery level. Due to a loose contact when charging, I accelerated hard more than once with an almost empty battery. Tiltback saved me every time. It's amazing how much power the wheel can still muster even with a relatively empty battery. A generous safety margin is important. That should also be possible with the S22.

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Personally I wouldn't want to mess around with tiltback settings, trying to figure out what is good and what is not and beta test them all, I would rather the manufacturers made a really good implementation, use @Freestyler custom firmware as a base aaaand done..

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On 1/2/2023 at 7:18 PM, mrelwood said:

That’s the part of the suggested tilt-forward that gives me the shills. Since  you’re already leaning forward, a tilt-forward would inevitably increase the lean until the rider reacts, and recovering from it would take more power than a mere tilt-back in the first place, which doesn’t take more power than what it would take to start braking at that time anyway. 

and yet, how many times have I read "and the pedals went soft, so I backed off and saved it"? I'm thinking "make the pedals soft while you still have a little bit of headroom", don't wait until you're so close to meeting the pavement that the power system isn't keeping up.

soft pedals are an oh sh*t moment. tiltback is at times, by some, mistaken for a challenge. Kind of like beeps.

Edited by Tawpie
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3 minutes ago, Tawpie said:

and yet, how many times have I read "and the pedals went soft, so I backed off and saved it"? I'm thinking "make the pedals soft while you still have a little bit of headroom", don't wait until you're so close to meeting the pavement that the power system isn't keeping up.

soft pedals are an oh sh*t moment. tiltback is at times, by some, mistaken for a challenge. Kind of like beeps.

don't do this, but would it be possible to set the tiltback at low speed and ride it backwards to get the feel of tilt forward. 

having learned on tilt back wheels, sounds like a nightmare to me. 

and i'm wondering if i can ride my s18 backwards, me facing the rear?

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13 minutes ago, novazeus said:

and i'm wondering if i can ride my s18 backwards, me facing the rear?

Wrongway Adam liked riding the S22 better that way...

but it won't affect tiltback... it tilts in the opposite direction of travel. I was doing a range test on my S18 and the battery pooped out, so I thought "I'll hike it home backwards...". Nah, it figured it out.

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1 hour ago, Tawpie said:

Wrongway Adam liked riding the S22 better that way...

but it won't affect tiltback... it tilts in the opposite direction of travel. I was doing a range test on my S18 and the battery pooped out, so I thought "I'll hike it home backwards...". Nah, it figured it out.

 

He's talking about riding (ASS forwards), technically his "heels" would go up. And toes dip down.

 

First time hearing about tilt forwards.. :confused1:

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Fun fact: the first s20 demo that arrived in NY (and Hsiang got) had a very strong tiltback. (sounds like the firmware you tested yourself @Rawnei)

They complained and it was "nerfed" to a much more subtle one which is hard to detect.

They purposely kept their silence and didn't report it to Kingsgong in order to achieve a "win" in their books. ("evil tiltback" defeated)

I remember all that conversation from the NY telegram chat. 

 

Not that it would make the difference in your case, since the tiltback was never engaged to begin with,

but goes to show you the impact one reviewer can have in the safety (or lack thereof) of the final product :)

Edited by Freestyler
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3 minutes ago, Freestyler said:

Fun fact: the first s20 demo that arrived in NY (and Hsiang got) had a very strong tiltback. (sounds like the firmware you tested yourself @Rawnei)

They complained and it was "nerfed" to a much more subtle one which is hard to detect.

They purposely kept that silent and didn't report it to Kingsgong in order to achieve a "win" in their books. ("evil tiltback" defeated)

I remember all that conversation from the NY telegram chat. 

 

Not that it would make the difference in your case, since the tiltback was never engaged to begin with,

but goes to show you the impact one reviewer can have in safety (or lack thereof) of the the final product :)

Funny, and right now they are tweaking tiltback based on my input, I am not sure if they have more riders giving them input or more beta testers but he who shouts the loudest..  A person on Facebook claimed they are releasing a new firmware with new tiltback any day now source EUCO, I hope it's not true and I hope it's not the strong one that would really suck. 😅

Maybe it would have helped in my case if it was PWM based. 😁

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On 12/30/2022 at 7:33 AM, Chriull said:

Here are both of your log snippets in a speed vs current diagram.

Battery current is unfortionately a bad measure for wheels burden. Just at 100% PWM it is equal to motor current - before it's "very off"

 

Overlean.png.b8de2f30efe8918817b27c583919c96a.png

 

Yup, always dangerous to show "current" in a graph without making clear where the current was measured. 
(Rawnei's data is battery current.)

A few more problems too:

  • At lower speeds, the EUC will not command 100% PWM, because the motor impedance is so low that motor current will reach the firmware's protection limit.
  • At higher speeds, battery current follows the shape of the motor's mechanical power curve. Parabolic. Not linear.

.02

 

Edited by RagingGrandpa
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59 minutes ago, RagingGrandpa said:

At higher speeds, battery current follows the shape of the motor's mechanical power curve. Parabolic. Not linear.

This parabolic peak power graphs is  motor output power (torque times angular velocity) and not battery provided power (Ub times Ib)

Battery current (almost) equals motor current at 100% duty cycle. And motor current is proportional to torque. So battery current limit is linear, too. Almost, at least. There are some effects which "push in" this linear limit line to follow some torque_equation.gif according to https://ebikes.ca/tools/simulator.html

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Ah, but motor output power is very directly related to controller input power.

Energy must come from somewhere, to be released in the motor output.
It's handy to talk about the rate of this energy flow as [Joules] per unit of time. That's how we define "power." 

Once we're into an efficient working range of the motor (e.g. not at very tiny forces or speeds), instantaneous power expresses the input needs of the motor nicely.

I agree with your comments about motor force and motor current... but we don't know them from Rawnei's data, so I think it's beside the point.

On 1/4/2023 at 3:01 PM, Chriull said:

Cool!

The interactive plot demonstrates my point well. Example below, for a system with no battery current limit (EUC's have none) and a high motor current limit (which EUC firmware enforces). 

  • Battery power is simply [motor output power] divided by [motor efficiency].
    That efficiency is between 60 and 80% during the 'normal speed range,' not changing much, and so battery power tracks motor power rather consistently, in the same shape as the red "Mtr Power" graph line.
     
  • Battery voltage changes only some 5% based on resistive drop. Let's ignore it. And so battery current tracks battery power nicely. 
    A small shame that the GUI doesn't plot battery power nor battery current, but you can mouse-over the graph to see it displayed beneath.

The result: for the motor's limit (e.g.: maximum output force) vs speed, the battery current will rise until the peak power point, then decay, the same as the red power line shows. 

And I won't object strongly to whether we call the final high-speed region "linear" or "parabolic" - it's falling quickly in both cases. 
The point I'm making is the low-high-low nature of the current-vs-speed plot. Overall, very nonlinear.

AIL4fc_9PgYbIGe3BOkaxOJE-KgljPGSwZ4CPSZx

On 1/4/2023 at 3:01 PM, Chriull said:

torque_equation.gif 

But they didn't describe the A-constants!
Fudge factors for the win :) 

Anyway, I think that won't be useful to us, because we don't record torques in EUC data logs. And Kingsongs don't even report Imotor.

 

Edited by RagingGrandpa
(img url)
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2 hours ago, RagingGrandpa said:

Battery power is simply [motor output power] divided by [motor efficiency].

In the motor plots (the first approximation) fir efficiancy is Pin = U motor(armature) x I motor and Pout = U back emf x I motor.

The difference is R coil x I motor²

2 hours ago, RagingGrandpa said:

But they didn't describe the A-constants!

Fudge factors for the win :) 

No explanation or link to any source. Didn't find any other paper describing this - anyway, the difference to a linear torque limit is not too big and the wheels reported values imho more inacurate.

2 hours ago, RagingGrandpa said:

Anyway, I think that won't be useful to us, because we don't record torques in EUC data logs. And Kingsongs don't even report Imotor.

As U back emf is proportional to speed by the factor kv, the torque is proportional to the motor current by km. km is the reciprocal value of kv. (With sone 2xpi, 60, etc if one does not use angular velocity in radians, m/s, etc)

The other needed relation is Ub x Ib = Um(armature)x Im with Ub/Um=Im/Ib= pwm duty cycle.

As with some more "unnecessary details" in https://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/?do=findComment&comment=100560

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On 12/30/2022 at 2:57 PM, Ben Kim said:

You failed to mention one key piece of information: ambient temperature. 
 

I did some digging which indicates you live in Sweden; it appears you don’t exactly have warm temperatures out there, so your overlean cutout is due to the batteries not being able to deliver the current requested due to colder operating temperature. 

 

rule of thumb: hard accelerate 7-10 kph less in colder temps (under 5C) than you would in warmer temps. I learned this the hard way as a new rider myself. Glad you’re okay though! 

 

On 12/30/2022 at 4:43 PM, Rawnei said:

Yesterday wasn't so cold maybe around 10c and this was also not long after leaving home so I doubt ambient temperature was a big factor.

I was looking at the s22 today, as some are with nice discount and I friend says it is what wants to get. I could not help to look up that they seem to come with 21700 50LT battery and I was wondering how good they would be for me, someone who often rides in colder weather too.

One source I found said that the 50LT had amazing 14A output possibly on good temperature conditions! Obviously I was very interested at that point but wanted to know what was this "good temperature", turns out they listed below 10 celsius as low output as 2,4A.. I mean what the.. maybe that source was wrong but..

Anyway so I come here and see you fall, somewhat weird conditions, made me wonder. Could your battery temperature been low? Did you have long period outside, and maybe lot of pauses?

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24 minutes ago, Tasku said:

 

I was looking at the s22 today, as some are with nice discount and I friend says it is what wants to get. I could not help to look up that they seem to come with 21700 50LT battery and I was wondering how good they would be for me, someone who often rides in colder weather too.

One source I found said that the 50LT had amazing 14A output possibly on good temperature conditions! Obviously I was very interested at that point but wanted to know what was this "good temperature", turns out they listed below 10 celsius as low output as 2,4A.. I mean what the.. maybe that source was wrong but..

Anyway so I come here and see you fall, somewhat weird conditions, made me wonder. Could your battery temperature been low? Did you have long period outside, and maybe lot of pauses?

Already answered, no, not remotely the reason I crashed.

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3 hours ago, Rawnei said:

Already answered, no, not remotely the reason I crashed.

Right I should have phrased my question better.. As i was curious to know about some of the safety features in the wheel regarding temperature.
I think you have encounterd some restriction to the wheel at some lower temperature? I hear s22 has temperature measurement but could you explain your experience and some rough temperature that behaviour changes in the wheel? If cold -> then max 25km/h or something? How cold=?

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6 hours ago, Tasku said:

Right I should have phrased my question better.. As i was curious to know about some of the safety features in the wheel regarding temperature.
I think you have encounterd some restriction to the wheel at some lower temperature? I hear s22 has temperature measurement but could you explain your experience and some rough temperature that behaviour changes in the wheel? If cold -> then max 25km/h or something? How cold=?

When any of the temperature sensors on the cells hit 5C the wheel will start throttle the top speed, i.e. dynamically change the top speed as temperatures goes down, throttling is progressive and gradual and since firmware 2.25 it throttles less than before, I don't know the lowest temperature point on the curve but from previous experience (earlier firmware) the lowest speed was 30kmh, it also goes back up as cells gets warmer.

Edited by Rawnei
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@Rawnei , hey man, I just read your thread, I’m glad you are OK! Your protection equipment did a good job and you were lucky your body took the impact well :) (just a small reminder for all of us, I guess, of how important gear is at all times).

    (Hmmm, didn’t we knew that KS S22 has torque issues in general, people complaining about that, like a general fact about the wheel??- a thought passing through my head)

    I think your accident just shows how important it is for the unicycles to have more reserve power stored in capacitors. This was big factor also in the Veteran Abrahams cutouts, and probably in many similar cases where nobody was aware of this. Kevin, euc upgrades, did a nice capacitor mod video on his Abraham. It would also benefit if high discharge batteries would be available instead of the long range ones.

   Kevin’s video with the Abraham mod: 

https://www.youtube.com/watch?v=jPzxm3Fa_LI

    IMHO the beeps or tilt backs would make no difference, as others noticed before, if there is no more power available for motor.

    We should put a little more pressure on the EUC producers to install more capacitance on the boards - @KingSong European Hub, @LeaperKim, @Inmotion Global, @Begode, so these kind of cutouts, with no time left for warnings and with no time left to react, will not happen anymore.

    I must notice here that @Inmotion Global did some noticeable improvements in the design of the V13 in this respect. It is a pity that they went again with their “complicated enough and unnecessary” design philosophy that can be seen in the suspension system.

    Now, I don’t know if there is enough space on the S22 board to put more capacitors and maybe manage to partially alleviate the issue with some DIY effort 🤔.  And the thing is we should not do this! This should be done by @KingSong! They should take in the problem, upgrade the boards as necessary, and send them to users together with a Sorry letter. The same for @LeaperKim, and the other ones. Does LeaperKim pay Kevin for doing the upgrades to their boards? I doubt, but they should, because it’s their faulty product, many people around the world had the cutouts, even had bad injuries- we know that from safe sources, and LeaperKim just pretended it was raining.

    In my own case, I checked and re-checked many times the space available on my V12 board (and was a lemon waiting to be repaired, for an epoch) and I might be able to add two more capacitors of the same size as the existing ones to increase the power during braking, that’s because I had issues with it and I don’t wanna end up under a car’s wheels.

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23 minutes ago, Paul g said:

to install more capacitance on the boards - @KingSong European Hub, @LeaperKim, @Inmotion Global, @Begode, so these kind of cutouts, with no time left for warnings and with no time left to react, will not happen anymore.

Sorry - that's not how EUC's work. BLDC motors always have a maximum torque over speed limit. Every EUC can be overleaned. One just can make the wheel more powerfull and the overlean happen at higher speeds/burdens.

Capacitors are no solution against overleans.

They can improve a bit the behaviour and release a bit the battery pulse burden.

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25 minutes ago, Chriull said:

Sorry - that's not how EUC's work. BLDC motors always have a maximum torque over speed limit. Every EUC can be overleaned. One just can make the wheel more powerfull and the overlean happen at higher speeds/burdens.

Capacitors are no solution against overleans.

They can improve a bit the behaviour and release a bit the battery pulse burden.

So you’re saying practically that wasn’t enough margin left to max speed and that’s why the cutout happened? That is still a KingSong issue, right?

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1 minute ago, Paul g said:

So you’re saying practically that wasn’t enough margin left to max speed and that’s why the cutout happened? That is still a KingSong issue, right?

I leaned too hard when there wasn't enough power margin left, same would happen on any wheel.

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  • 2 weeks later...
On 1/8/2023 at 3:28 PM, Paul g said:

@Rawnei

    I think your accident just shows how important it is for the unicycles to have more reserve power stored in capacitors. This was big factor also in the Veteran Abrahams cutouts, and probably in many similar cases where nobody was aware of this. Kevin, euc upgrades, did a nice capacitor mod video on his Abraham. It would also benefit if high discharge batteries would be available instead of the long range ones.

   

Ah.... I think it just shows you to STOP MAX SPEED RIDING like an idiot... How many time it has to be said on an unicycle...'DON'T GO TO MAX SPEED LIMIT'??? 

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