Ninebot random shutoff :(

[musk]

27 minutes ago, Shoe73 said:

Except there are no gears in the wheel. The wheel and the motor are the same thing.

For clarity, the rubber tire is distinct from the wheel in that description.

8 minutes ago, Chris said:

..and chriscalandro is misstaken about the batteries... they will not output the same current as these are not single batteries but battery packs. Bigger battery = more batteries = more amperage

Thats what I thought too.  If you're achieving a larger capacity (WH) by adding more cells in parallel, the individual drain rate of each sell is lower with the larger capacity pack.  No?

 

 

[Chris]

Yes, that's correct. Leaves more room for peak loads when you need it

[Keith]

1 hour ago, chriscalandro said:

I don't know how many times I have to repeat this but BATTERY SIZE DOES NOT EQUAL MOTOR POWER OUTPUT. 

 

Stop spitting your gibberish. A 100wh battery at 24v will output the same as a 600wh battery at 24v. 

 

A 100wh battery will deplete faster, but until then it will still provide the same current!

 

STOP!

 

In response to the above video, that sounds like stripped gears on a motor.

 

I haven't seen the falling video but it sounds like if you hear the motor RPM rise and the wheel doesn't go faster, the tire became disconnected from the motor.  That is the ONLY way that could happen. 

 

I do remember someone recently saying their bot didn't power on and the wheel spun loose like a bicyce. That would be the same situation. 

With all of this put together I would suggest the problem is a assembly one. Nothing else. Nothing to do with electronics or batteries or the alignment of the planets, but a simple assembly issue involving poor gear meshing. 

Nonsense, cells have internal resistance which is very significant at the sort of currents these wheels take, that resistance lowers the voltage at the motor which, in turn, lowers the current. Battery packs of greater Wh have multiple cells in parallel. In any situation where resistors are in parallel the total resistance is lowered, indeed halved for two equal resistors in parallel. As a result a larger Wh battery will deliver more current and a higher voltage at the same state of charge. It will also, of course stay at a higher voltage for longer so the reduction in power will be less for a given mileage as well.

[Chriull]

1 hour ago, chriscalandro said:

I don't know how many times I have to repeat this but BATTERY SIZE DOES NOT EQUAL MOTOR POWER OUTPUT. 

No. Its not the motor thats limiting the output power but the battery for EUCs

1 hour ago, chriscalandro said:

Stop spitting your gibberish. A 100wh battery at 24v will output the same as a 600wh battery at 24v. 

???? Thats real gibberish  - in regard to how battery packs are build in real life EUCs:

1 hour ago, chriscalandro said:

A 100wh battery will deplete faster, but until then it will still provide the same current!

Only if the internal resistance and the other internal chemical processes would be the same, BUT in EUCs, like the other posters already stated its different. There are normaly 15-16 li-ion cells in series, depending on the modell.

This gives the around 130 Wh battery pack. Models with around 260 Wh have two of this packs in parallel, higher Wh EUCs then have 3,4 and more of this in parallel.

This CHANGES the behaviour - two packs in parallel have half of the internal resistance and can deliver double the current than one pack, three have one third of the internal resistance, can deliver three times the current, and so on.

With the same current deliverd you have less voltage drop, the more packs are in parallel.

And additionally - imho on of the biggest benefits of the more packs you have in parallel is, that you can be sure to operate them within their specification and you have no overly voltage drops that leads to cut outs you experience with single battery packs. Imho single battery packs are at the limit or just overchallenged by typical EUCs.

1 hour ago, chriscalandro said:

STOP!

Agreed. Stop this

 

[Cranium]

7 hours ago, chriscalandro said:

I don't know how many times I have to repeat this but BATTERY SIZE DOES NOT EQUAL MOTOR POWER OUTPUT. 

Stop spitting your gibberish. A 100wh battery at 24v will output the same as a 600wh battery at 24v. 

A 100wh battery will deplete faster, but until then it will still provide the same current!

You are not completely correct.  Motor ratings and battery ratings are indeed two different things.  But if the motor wants power and the battery can't give it because it doesn't have the capacity, it will be beneficial to have a larger pack because of parallelism in battery packs.

If the 130Whr pack referred to is a 16S pack then it would have a 2.2Ahr rating (130Whr / 59.2V).  This means each cell is ~2200mAH (although I've seen mention it is only 2000mAH).  2200mAH is achieved by a single battery so it would be a single string of batteries in a 16S/1P configuration.  The max amps of this battery pack would be the same as the max amps of a single battery in a series arrangement and probably around 10A whcih means the max power of the battery pack would be about 592Watts nominal (10A * 3.7V * 16 cells).

If you double the capacity of the battery pack, double the other numbers.  So you have a 4.4Ahr battery and you need 4400mAH for each cell in series.  Since they don't make them at this capacity, you put two 2200mAH batteries in parallel and you end up with a 16S/2P configuration.  The max amps are now double because you have batteries in parallel so it would be 20A which means the max power of the battery pack would be 1184Watts nominal (20A * 3.7V * 16 cells).

So if the limitation is due to the motor being starved of the power it needs (which is the case many times), larger batteries will produce more power for the motor because of parallelism.   But if you exceed the motor ratings, a larger pack will do nothing at all. 

[esaj]

Hmm, I'm not so sure on all of your points @Cranium, although I think chriscalandro is wrong about the amperages.

3 hours ago, Cranium said:

You are not completely correct.  Motor ratings and battery ratings are indeed two different things.  But if the motor wants power and the battery can't give it because it doesn't have the capacity, it will be beneficial to have a larger pack because of parallelism in battery packs.

If the 130Whr pack referred to is a 16S pack then it would have a 35Ahr rating (130Whr / 3.7V).  This means each cell is ~2200mAH (although I've seen mention it is only 2000mAH).  2200mAH is achieved by a single battery so it would be a single string of batteries in a 16S/1P configuration.  The max amps of this battery pack would be the same as the max amps of a single battery in a series arrangement and probably around 10A whcih means the max power of the battery pack would be about 592Watts nominal (10A * 3.7V * 16 cells).

Are you perhaps mixing up parallel and series configurations here? 130Wh / 16S pack would have 2.2Ah rating, since the cells are in series (the amp hours don't go up, the voltage does). So it's still the amp hours of a single cell, but the nominal voltage is 16 * 3.7 = 59.2V. If you placed 16 cells in parallel, you'd have the same voltage as a single cell (3.7V), but 16 times the amp hour capacity: 16 * 2.2Ah = 35.2Ah.

From my understanding, the "rated" continuous and maximum currents are manufacturer recommendations for safe limits. The discharge current ratings for the cells used typically in EUCs are something like between 10A-20A continuous / 20-30A max, but the packs could happily give 100A (for example) for a short while if short circuited (ie. if the resistance of the circuit is low enough, that is internal resistance of the cells + other stuff in the current path) and the BMS doesn't cut out due to overcurrent. For the total watt output, it doesn't matter whether the cells are in series or parallel. If a 16S pack could give out 10A for example, 16P pack would be able give out 16 * 10A = 160A:

16S: 10A * 59.2V = 592W

16P: 160A * 3.7V = 592W

As for the max output, regardless of the rated amperage, assuming a short circuit with 20mOhm internal resistance for a cell plus 20mOhm for connections & wire connecting the terminals of the battery (I pulled the latter number from my hat and it's probably too large for wire, but many 10A continuous / 20A max Li-ion cells have internal resistances in the 20-30mOhm range, some even lower), you'd get a total resistance of 40mOhm (0.04ohm). If the voltage wouldn't sag, the current would be:

I = U/R => 3.7V / 0.04Ohm = 92,5A

for nominal 3.7V voltage and for fully charged (4.2V) cell:

I = U/R => 4.2V / 0.04Ohm = 105A

As there's no BMS or anything else there to limit the current in this hypothetical situation, the cell will give out huge currents in short circuit, regardless of what the cell max output was "rated" for. If the wire resistance was less, the currents would go even higher. Of course in real life the voltage would probably drop in an instant and so would then the current, but the cell would still overheat and catch fire or explode. Don't try this

 

3 hours ago, Cranium said:

So if the limitation is due to the motor being starved of the power it needs (which is the case many times), larger batteries will produce more power for the motor because of parallelism.   But if you exceed the motor ratings, a larger pack will do nothing at all. 

I think @Mystamo or someone else who's been dealing with e-bikes said that they've "overvolted" many motors, and they can work above their rated max continuous / burst wattages. So again the rating is probably a manufacturer recommendation for safe operation of the motor (above that, it could get damaged due to coils melting or such?). Except for the internal resistance of the motor, there isn't anything to limit the max current / voltage and thus power?

[SlowMo]

On 1/26/2016 at 4:41 AM, esaj said:

I'm definitely not recommending a Ninebot to anyone anymore  

EDIT: And it's not because of this incident (alone), but it has become a recurring theme in the forums that people have random shutoffs, fried mainboards due to bad firmware and generally the wheel is starting to seem really unreliable. Of course any wheel can fail any time, but Ninebot has clearly taken the lead in incidents. Of course that's also probably partially due to them being so common.

I have 6 wheels including one Generic X3 clone. I haven't got any problems. No shut down or malfunction with any except for my Ninebot.

[OliverH]

43 minutes ago, SlowMo said:

I have 6 wheels including one Generic X3 clone. I haven't got any problems. No shut down or malfunction with any except for my Ninebot.

You don't count as a light weight rider

[SlowMo]

23 minutes ago, OliverH said:

You don't count as a light weight rider

I only weigh 65 kilos 

[Cranium]

2 hours ago, esaj said:

Are you perhaps mixing up parallel and series configurations here? 130Wh / 16S pack would have 2.2Ah rating, since the cells are in series (the amp hours don't go up, the voltage does). So it's still the amp hours of a single cell, but the nominal voltage is 16 * 3.7 = 59.2V. If you placed 16 cells in parallel, you'd have the same voltage as a single cell (3.7V), but 16 times the amp hour capacity: 16 * 2.2Ah = 35.2Ah.

You are absolutely correct.  I rushed through calculations to get to the end point.  I didn't check my work and divided by an individual cell voltage rather than the pack voltage.  To be fair, I messed up showing some of my work but the final answer was right.   (1/2 credit?)

 

2 hours ago, esaj said:

As for the max output, regardless of the rated amperage, assuming a short circuit with 20mOhm internal resistance for a cell plus 20mOhm for connections & wire....

Now you are just trying to bust my balls here!  LOL  I included what you would see on a typical manufacturers spec sheet for this type of battery.  I think for this type of general discussion, you have to pick the level of detail you want to discuss based on the general audience.  Otherwise it will just add to the confusion and is certainly not that important to gain an understanding of how parallelism effects the current capacity of a battery.  Just like when learning electronics and doing basic calculations for power, voltage, current and capacitance, you didn't take wire losses and component tolerances into account to calculate the right answer.  When you start talking too technical and have too much information, a certain portion of your audience tunes out and just sees blah, blah. blah. 

2 hours ago, esaj said:

I think @Mystamo or someone else who's been dealing with e-bikes said that they've "overvolted" many motors, and they can work above their rated max continuous / burst wattages. So again the rating is probably a manufacturer recommendation for safe operation of the motor (above that, it could get damaged due to coils melting or such?).

I interpret your statement as suggesting that since you know of someone that has "overvolted" some motors it must be OK to do this to all motors because every manufacturer builds in lots of headroom in their specifications?   I know of someone that claims shunting is a great thing and everyone should do it.  But that doesn't make it the right thing for everyone to do.  And certainly not a safe thing to suggest as a general practice.  We don't really know where each manufacturer draws their line when coming up with their specs.  

2 hours ago, esaj said:

Except for the internal resistance of the motor, there isn't anything to limit the max current / voltage and thus power?

Why yes, there is! Look up iron loss (or Eddy current and hysteresis heating) and how it relates to increased current.  Discussion here.  Section 7 here.  General discussion here  Unless I am totally wrong (which most certainly could be the case ), the efficiency of a motor drops very quickly at a certain point and more amps does not help. 

 

[esaj]

 

18 minutes ago, Cranium said:

Now you are just trying to bust my balls here!  LOL  I included what you would see on a typical manufacturers spec sheet for this type of battery.  I think for this type of general discussion, you have to pick the level of detail you want to discuss based on the general audience.  Otherwise it will just add to the confusion and is certainly not that important to gain an understanding of how parallelism effects the current capacity of a battery.  Just like when learning electronics and doing basic calculations for power, voltage, current and capacitance, you didn't take wire losses and component tolerances into account to calculate the right answer.  When you start talking too technical and have too much information, a certain portion of your audience tunes out and just sees blah, blah. blah. 

Sorry if you got that impression, the point was to show that even when the specs say the max discharge is X amps, there's nothing (in unprotected cells) that actually would prevent the amperage from going above that value in case of short circuit or if the mainboard/bridges allows the motor to draw more amps than the rated amperage. Just so that people don't assume that the output can't go above that figure in any situation.

 

18 minutes ago, Cranium said:

I interpret your statement as suggesting that since you know of someone that has "overvolted" some motors it must be OK to do this to all motors because every manufacturer builds in lots of headroom in their specifications?  

No, I wouldn't suggest trying to "overvolt" a motor, especially in an EUC, again just saying that the rated / max powers seem more like recommendations made by the manufacturer, and shouldn't be crossed, but I don't think there's anything in the motor that would actively prevent that? I was just mostly referring to the " But if you exceed the motor ratings, a larger pack will do nothing at all."-part. I believe you could short-circuit a motor over a battery, letting it draw much more power than it was designed for, and it would probably burn (well, it wouldn't work with 3-phase motor like that, but I think you get the point), not just magically stop drawing more power when it reaches the maximum rated wattage. But I could be wrong on this point, as you next mention:

 

18 minutes ago, Cranium said:

Why yes, there is! Look up iron loss (or Eddy current and hysteresis heating) and how it relates to increased current.  Discussion here.  Section 7 here.  General discussion here  Unless I am totally wrong (which most certainly could be the case ), the efficiency of a motor drops very quickly at a certain point and more amps does not help. 

Electromagnetic phenomenons like that go way beyond my knowledge  I think back in the day there was some circuit analysis -course mentioning eddy currents and some calculations related to them, and all I remember is that it was hard   But would the motor then automatically limit the maximum power it draws? Of course the efficiency probably goes down the toilet after certain point ("diminishing returns" and all that), but would that actually prevent the motor from drawing more power, even though it's useless?

[esaj]

While I've underlined that I'm not an expert of any sort in these things on many occasions, and urged people to always be careful when dealing with these things (especially electronics or batteries), I felt it best to add a small disclaimer in my signature:

While I discuss things like batteries, motors, electronics, physics etc. in these forums, I'm not qualified in these areas in any way (except for software engineering). I'm an amateur and a hobbyist, and my "knowledge" and conclusions (more like "best guesses") comes mainly from reading and studying about these subjects, not that much from real world experience, and I could be wrong about things. I take no responsibility of any wrong information I may have (unintentionally) written or wrong conclusions I've made based on my limited knowledge or misunderstandings.
 

 

[lizardmech]

To me it looks like the motors are losing synchronization. presumably the EUC reacts to the sudden loss of torque by increasing current which doesn't help because the motor is out of sync then shuts down due to over current. This would be likely to be an issue on faster models with larger wheels. By increasing the top speed of the motor they reduce torque making it more likely to stall and desync with the controller. It might be somewhat fixable via controller design but it's likely that direct drive ebike hubmotors are  mainly suited to 12-15kmh models.

[OliverH]

4 hours ago, esaj said:

While I've underlined that I'm not an expert of any sort in these things on many occasions, and urged people to always be careful when dealing with these things (especially electronics or batteries), I felt it best to add a small disclaimer in my signature:

While I discuss things like batteries, motors, electronics, physics etc. in these forums, I'm not qualified in these areas in any way (except for software engineering). I'm an amateur and a hobbyist, and my "knowledge" and conclusions (more like "best guesses") comes mainly from reading and studying about these subjects, not that much from real world experience, and I could be wrong about things. I take no responsibility of any wrong information I may have (unintentionally) written or wrong conclusions I've made based on my limited knowledge or misunderstandings.
 

 

Don't say you're not an expert: https://www.youtube.com/watch?v=BKorP55Aqvg

[esaj]

21 minutes ago, OliverH said:

Don't say you're not an expert: https://www.youtube.com/watch?v=BKorP55Aqvg

Actually, that's not so far from reality in software-business at times...

[Blunzn]

1 hour ago, OliverH said:

Don't say you're not an expert: https://www.youtube.com/watch?v=BKorP55Aqvg

sorry for OT - one solution https://www.youtube.com/watch?v=B7MIJP90biM   

 

[Cranium]

7 hours ago, esaj said:

While I've underlined that I'm not an expert of any sort in these things on many occasions, and urged people to always be careful when dealing with these things (especially electronics or batteries), I felt it best to add a small disclaimer in my signature:

While I discuss things like batteries, motors, electronics, physics etc. in these forums, I'm not qualified in these areas in any way (except for software engineering). I'm an amateur and a hobbyist, and my "knowledge" and conclusions (more like "best guesses") comes mainly from reading and studying about these subjects, not that much from real world experience, and I could be wrong about things. I take no responsibility of any wrong information I may have (unintentionally) written or wrong conclusions I've made based on my limited knowledge or misunderstandings.
 

 

Excellent idea.  I'm taking your idea and making it my own!

 

[chriscalandro]

7 hours ago, lizardmech said:

To me it looks like the motors are losing synchronization. presumably the EUC reacts to the sudden loss of torque by increasing current which doesn't help because the motor is out of sync then shuts down due to over current. This would be likely to be an issue on faster models with larger wheels. By increasing the top speed of the motor they reduce torque making it more likely to stall and desync with the controller. It might be somewhat fixable via controller design but it's likely that direct drive ebike hubmotors are  mainly suited to 12-15kmh models.

I have done a bit if research and it appears ibwas wrong. The above quoted comment is 100% correct. 

 

It sounded like gears, so I thought gears. A out of sync brushless motor WILL make this sound. 

[jer]

On 1/25/2016 at 11:50 PM, adhermes said:

Here is the upload:

https://youtu.be/hSWyCxrE2Uw

 

Happens pretty quick. We have slowed it down to frame by frame in 1080P and the pedals go complete limp all within one frame. Really hard to recover. 

I am new to this, about 1 week, just getting the hang of going along, but the exact same thing happened to me.  I went over an expansion joint in a concrete road and it just gave up the ghost, conked out and sent me flying.  I had been going up and down this  same bit of drive all afternoon just to get used to things and the joint itself was nothing that you would consider slowing down for.  I wasn't trying to go fast, just to have sufficient speed to be stable.  Fortunately I wasn't particularly hurt, but it was pretty instantaneous.  Firmware version is 1.35 and the machine is  brand new Ninebot 1e +.  Contacted the supplier but haven't had an answer as to if there is an issue.  

Now I am focusing on going really slowly all the time.

I think the Ninebot may be over sensitive to small ruts or changes in  the road surface.

A bit more robustness in this area would be appreciated.

 

Jeremy

 

[Gil]

During my Sunday Ninebot trip, I was thinking about all these incidents and was wondering whether the fact that most rider set the 'riding mode' to 0 could explain some shut-offs.

First, '3' is the default setting. It lets some margin for the 9B1 to react in case of a bump.

Secondly, you can be sure that the firmware is more thoroughly tested with the setting at '3' (default value) rather than '0' (extreme value).

I know that these thoughts are subjective and many of you will say that every 'ride mode' value should be safe. Please, don't shout ;-)

For my part, as I experienced two face-plants (pushing the machine to its limits with facing wind) and a complete burning of the PCB (during an emergency braking) with an other brand, I ride very quietly, avoiding strong accelerations and slowdowns. On advice of my reseller, I have set the riding mode at 3 which is a good trade-off between reactivity and comfort.

9B1 are not competition machines but urban mobility tools. Let them some reaction margins in case of any event.

[ToniG123]

Geez @Gil, just today I was considering changing from ride mode 3 to 0.

It's been three months since I started with my 9B1 and I think I'm getting good at it (still plenty of room for improvement though).

Your argument seems solid enough for me, I think I'll just leave it at 3 for the moment.

 

[OneWheel]

Ninebot needs to

1. remove ride mode 0

2. change the board design or software update (downgrade)

Ninebot lack the skilled engineers to react quickly like KingSong , under qualify Ninebot people in the wrong position or over qualify Ninebot people in the wrong position, the positions need to swap or get new people to do the job right.

[Rotator]

Just to let you know...

I did my first 1000km in ride mode 0.

Then, from 1000 to 2000 in ride mode 3.

And from 2000 to 3000 in ride mode 6.

Never experimented a shutdown. And I have done a lot of hard accelerations and brakes.

I have a ninebot E (240w).

Until we know the reason for unexpected shutdowns, it will be difficult to give a workaround (like change ride modes).

[Gil]

@rotator: the more you master your wheel, the more you raise the 'ride mode'. Interesting because many experienced rider choose 0. Could you explain why you go the reverse way ?

[Rotator]

Now I feel confortable with any mode between 0 and 6. Sometimes I change it with no any reason. Only to change it as if was a different euc.

I find 9 the more difficult to ride. In mode 0 the euc is very stable, horizontal like the ground, so when I started to learn I found this mode 0 the easier.

Now I ride a few kms. in mode 9 only for fun, but it reacts very slow. I find it a little dangerous to hard brake, so ride in this mode only when I am alone, and there are not people around.