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Ninebot one e+: uphill worrying cut-out


LEO_LEO

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my ninebot one e+ is dead while I was going uphill.

The atmospheric temperature was certainly high, I was almost at the top, after warning beeps, I waited a few minutes then I started again, after around 100 meters it suddenly turned off and now no longer gives signs of life.


I have not yet disassembled, but in this cases, is it recoverable? what I have to check?

(thanks)

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1 hour ago, LEO_LEO said:

my ninebot one e+ is dead while I was going uphill.

The atmospheric temperature was certainly high, I was almost at the top, after warning beeps, I waited a few minutes then I started again, after around 100 meters it suddenly turned off and now no longer gives signs of life.


I have not yet disassembled, but in this cases, is it recoverable? what I have to check?

(thanks)

Could be a bms cut-off. if so plugging the charger in or disconnecting the batteries should reset this

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Yesterday I took the screwdriver and I placed the 9bot on the table to disassemble the battery. Before I started, I tried again to press the power button: the 9bot started! I do not know how to explain this thing, I'm sure I tried several times to turn it on the day of the faceplant and the button did not work: Maybe I was shaken by the faceplant, but mistakes several times to push a button seems strange. Anyway, all is well what ends well, the 9bot works again, I connected it to the app and I checked the battery level was 32% ( I thought 55-65 %)

 

What I learned from the experience:
1) The electric motor is not like the combustion engine, there are no intermediate stad, it switches from working normal to not working at the light speed, there is no time to guess if it is going to yield, then check the parameters is really very important
2) if it has low battery, my friend 9bot changes character and becomes much less patient, if I stress him, he gets angry and goes away without warning... and let I pay the bill in full

 

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17 hours ago, Chriull said:

Could be a bms cut-off. if so plugging the charger in or disconnecting the batteries should reset this

The BMS problem is due to the discharge protection which cut if one cell is under 3V (or around this voltage).

Disconnecting the battery pack can't solve the problem but you'd better to make few cycles of load with a long time to equilibrate cells (if your BMS still done is job). And to avoid a new cut-off it's possible to make a shunt on your BMS. 

 

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5 hours ago, smallexis said:

The BMS problem is due to the discharge protection which cut if one cell is under 3V (or around this voltage).

Disconnecting the battery pack can't solve the problem but you'd better to make few cycles of load with a long time to equilibrate cells (if your BMS still done is job). And to avoid a new cut-off it's possible to make a shunt on your BMS. 

 

There is also an over current cutoff by the 9b1 bms - this can be reset by disconnecting the battery.

the undervoltage cutoff only by reconnecting the charger.

maybe there is also some overtemp cutoff which resets itself over time?

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1 hour ago, Chriull said:

There is also an over current cutoff by the 9b1 bms

which can be solved by a shunt

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2 hours ago, Chriull said:

 

maybe there is also some overtemp cutoff which resets itself over time?

I think you're right, at least I rememer reading about something along those lines...

But could very well be what @smallexis said about cells being underpowered.

@LEO_LEO Are you using a Charge Doctor by any chance? That could be the reason for cells to never getting the chance to balance...

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9 hours ago, smallexis said:

The BMS problem is due to the discharge protection which cut if one cell is under 3V (or around this voltage).

Disconnecting the battery pack can't solve the problem but you'd better to make few cycles of load with a long time to equilibrate cells (if your BMS still done is job). And to avoid a new cut-off it's possible to make a shunt on your BMS. 

I thought Ninebot BMS doesn't have balancing at all?

This is not necessary for batteries (for example original Ninebot) without a balancer circuit. (These batteries have limited durability by saving this necessary balancer circuit)

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Last night I forgot to unplug the charger before going to bed.  So it was on the green light for about 9 hours I would guess, it had already showed fully charged before going to bed, but I wanted to leave it balancing (if it does balance) for a little longer and then forgot to unplug it.  This morning saw it plugged in, disconnected the charger, turned on the wheel and opened the app.  It showed 62.07 volts, slightly higher voltage than when unplugging soon after going to the green charger light.  The most I ever saw before was less than 62 volts, something like 61.7 or thereabouts.  @dpong once wrote that he charged fully every day and rode about 17 miles a day, and never had a problem.

@LEO_LEO my ninebot feels weak at 50%, that's about 55 volts, 32% might not be enough voltage to climb hills but is plenty for driving on level ground.   Have you charged it fully and does it work better now?  I'm glad that it started working the next day.

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9 hours ago, esaj said:

I thought Ninebot BMS doesn't have balancing at all?

This is not necessary for batteries (for example original Ninebot) without a balancer circuit. (These batteries have limited durability by saving this necessary balancer circuit)

Ninebots bms has a balancing circuit integrated, but as far as i remember @1RadWerkstattstated that it only uses the internal switches of the controll ic and has no external mosfets, so only very limited balancing currents can occur.

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Ok thank you all... but I understand little more than nothing
I did not understand what i do with the batteries, what should I check and how to do it, I do not know the technical terms, can you explain how to explain to a child :innocent1:  or if it is too long with some educational links?
 
( The cut-off happened on Saturday, Sunday and Monday to lick my wounds. I still have a wrist that hurts me, but nothing broken.
Last night I reloaded the 9bot and I went out for some simple trick of reconciliation, the wheel and the rider seem all right. )
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2 hours ago, LEO_LEO said:
Ok thank you all... but I understand little more than nothing
I did not understand what i do with the batteries, what should I check and how to do it, I do not know the technical terms, can you explain how to explain to a child :innocent1:  or if it is too long with some educational links?
 
( The cut-off happened on Saturday, Sunday and Monday to lick my wounds. I still have a wrist that hurts me, but nothing broken.
Last night I reloaded the 9bot and I went out for some simple trick of reconciliation, the wheel and the rider seem all right. )

First you have the BMS cut-offs from:

- over-current: The BMS cuts off once too much current flows. can be reset by plugging in the charger or disconnecting the battery. As @smallexiswrote one can also shunt the battery ( see http://forum.electricunicycle.org/topic/459-electric-unicycles-bms-problem-and-solution/ )

- under voltage: if one or more cells get under a certain voltage the bms cuts-off. Could happen with an low charged battery in combination with an big voltage sag (high load - much amperes), by some aged/depriciated cells (old pack - many charging cycles or just bad luck with some cells). Can be reset by plugging in the charger or sometimes the cells just regenerate and the wheel can be turned on after some time - but the next cut-off is about to happen with the next higher load.

If just some cells have lower charge=voltage then balancing can help - thats happening once normal charging (red light) is finished and the green light is on. Takes quite some time and as written before, the balancing system of the ninebot bms should not be very effective...

If some cells are really aged and low voltage the only solution is a replacement.

- over-temp: the BMS ?could? cut-off once it measures too high temperature around the cells - should not happen. Normally the motherboard sensor gets high temp before and starts to beep/tilt-back/etc. If really the bms cuts-off for high temp just waiting should reset it?

Overleans: One fell but the wheel is still on (not bms cut-off - Although the bms could cut-off due to an over-current cut-off while the wheel bounces around...)

Happens once the rider asks for more the wheel can deliver - so no more balancing and if one leans forward there is suddenly no "resistance" anymore and a faceplant likely.

This is related either to the max-torque over speed curve of the electric motors:

bldcfig5.jpg

(could be also maybe a nice introductionary reading on bldc motors at http://www.edn.com/Home/PrintView?contentItemId=4406682 - but did not look at this page in detail)

In this graph you see that the maximum possible torque the motor can deliver decreases with increasing speed. So going uphill could ask for too much at 15 km/h while at 10 km/h one still has nice acceleration and does not feel the limit coming closer...)

The other limiting factor are the batteries. Espcecially the 2p (2 cells in parallel as used for the 9b1 e+) can be the limiting factor. The current through the windings is proportional to the torque produced - so if the battery cannot deliver the needed amps -> overlean.

 

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@Chriull  thanks,  if I understand well, the reasons of the cut off that I have to consider dangerous, is that some cells of my battery are not good.

@Vik's  porposes a charge doctor, I haven't, it is possible to have an idea of the battery health with a more simply home made way? 

Is there a sequence of operations can help the battery to stay better? 

(... I read that if the problem was the overload energy flow required, I can solve it with the BMS shunt, I searched also on Google but I have not found explicit instructions for Ninebot, only other brands. )

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@steve454 , thanks for the information, I usually look at not reaching the 20 km/h, I never watched the volts :pooping:, do you think checking the volts during use, I can understand if the battery is in good condition?

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8 minutes ago, LEO_LEO said:

@Chriull  thanks,  if I understand well, the reasons of the cut off that I have to consider dangerous, is that some cells of my battery are not good.

If you can load your battery to ~62V and have normal range your cells should be ok.

Quote

  @Vik's  porposes a charge doctor, I haven't, it is possible to have an idea of the battery health with a more simply home made way? 

Is there a sequence of operations can help the battery to stay better? 

(... I read that if the problem was the overload energy flow required, I can solve it with the BMS shunt, I searched also on Google but I have not found explicit instructions for Ninebot, only other brands. )

The charge doctor can help you to prolong battery life by only charging to 80-90%. This decreases a bit the range but increase the life-cycles of your battery. Also storing at ~40% charge increases the lifetime. (www.batteryuniversity.com)

http://hobby16.neowp.fr/2016/02/06/charge-doctor-v2-10a-3/

From @hobby16 also come the BMS shunt explanations - but also on his homepage many pictures are missing ;(

In the thread i linked above is for sure somewhere the explanation on how to shunt the 9b1...

Edit: But imho on two 9b1's i know as good as no (at least i could not identify or remember one) overcurrent shutoff happened.

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1 hour ago, LEO_LEO said:

@steve454 , thanks for the information, I usually look at not reaching the 20 km/h, I never watched the volts :pooping:, do you think checking the volts during use, I can understand if the battery is in good condition?

I don't know, but like @Chriull said, if it will charge to about 62 volts, the batteries are probably good.  

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5 hours ago, LEO_LEO said:

I read that if the problem was the overload energy flow required, I can solve it with the BMS shunt, I searched also on Google but I have not found explicit instructions for Ninebot, only other brands. )

Ok I will show you how to make a shunt :

59554dcca115e_shunt9b1bms.jpg.2a31bd0f5c2600be655d406d6c7c86a5.jpg

On your 9B1 's BMS, le black wire (for power) is solder at the V- place (see inside yellow rectangle)

If you solder a wire (which need to be as big as power wires) between V- et B- place (see inside orange rectangle), the output protection is shunted.

100_0946.JPG.e082d98cf790a6192c5c2de512b2221b.JPG

It's very easy and simple to do it. But you need to remove the heat shrink.

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17 hours ago, LEO_LEO said:

@steve454 , thanks for the information, I usually look at not reaching the 20 km/h, I never watched the volts :pooping:, do you think checking the volts during use, I can understand if the battery is in good condition?

Imho cells go not bad within an instant! That should be a "slow" process - so watching the voltage while driving should be way overdone. You'll notice it once the "performance" of your wheel decreases faster from a fully charged battery.(1) Last stage is that you cannot fully charge the pack anymore (this around 62V - depends on the calibration of your charger) - then it's time to replace the bad cells/the whole pack.

So after ~300 full charge cycles (from 0%-100%, add partially charges up to full charges!, wheels do not discharge the cells to 0%) the capacity of the cells should drop to ~70% - so they are still not dead! They just became old and you'll notice the lower range.

If one drives 2-4 times a week with ~2 full charge cycles this will take ~3 years. If one takes a winter break (too cold for driving) this increases to ~5-6 years - so as sayed before aging should be a very "slow process". Most probably one upgraded already to a new wheel before really noticing battery degradation!

(1) if you log your drive with gyrometrics(former 9bmetrics) or wheellog you could calculate the load behaviour of your cells (~internal resistance) and determine the "deteroriaton state". But one would have to get the load situation, temperature, previous load history, etc... for this - did not invest too much time into this till now, but i think it's not really trivial. Especially with the 9bot updating the voltage values too slow to really get numbers for this...

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I checked the parameters today: I loaded the wheel to the maximum and marked 62.75 volts just loaded. Today I came to the office with the wheel, I made about 3.5 km of which an uphill part, the app reports that I am still charged to 100% but the voltage dropped to 60.42 volts,  this numbers makes me think that the battery works pretty well

 

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Nice news if cells are OK but BMS output protection keep still dangerous

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