Well just had an unavoidable faceplant

[Wheelie]

It was unavoidable because there was no way for me to know that my Inmotion V3S would randomly shut off on me while I was barely reaching the max speed and weight. Nothing was in my way and I was riding on smooth concrete sidewalk tonight when it suddenly decided to shut off and I scrapped my knee and upper lip. The battery was at 96% and I just filled the tires before that run too so I dont know what's the problem. I've only had it for 10 months now and the orange tool icon lights up when I turn it on then it automatically shuts off. I checked with the app and did a diagnose and it showed 100%.

[Hunka Hunka Burning Love]

I wonder if it could be a bad cell in the battery pack.  Something similar happened to @noisycarlos with his Ninebot One E+.  When charging, do you sometimes allow the charger to stay plugged in for a while after the LED turns green to help balance the cells?   Maybe during higher current draw (high speed/hill climb), the bad cell isn't able to pull its weight so the normal performance limits take a hit.

Also could be bad BMS shutting things down when it shouldn't be?   Loose connection from vibration over 10 months?

[Wheelie]

Could be. I sometimes charge it overnight but it does cut off the power at 100% so that shouldn't be an issue. I did have to get the tires changed a few times during those 10 months and I put nearly 700miles on it.

[noisycarlos]

In my case, the pack on my Ninebot had bad cells (8 out of 30 btw). It would turn on and balance, but as soon as you put weight on it, it would shut off. I bought a new pack and that fixed it. Not ideal, but I did have over 1300 miles on it, and i was out of warranty.

[Paddylaz]

Is there any way to tell if your wheel has a 'bad cell(s)' without opening it all up??

Ps. Im constantly impressed by the electrical knowledge of some of the people on this forum! Way over my head!

[Carlos E Rodriguez]

58 minutes ago, Paddylaz said:

Is there any way to tell if your wheel has a 'bad cell(s)' without opening it all up??

Ps. Im constantly impressed by the electrical knowledge of some of the people on this forum! Way over my head!

If you can bench charge possibly. 

Lets say get a DVM and measure the charge voltage. Record. It will look lower during the current mode phase of charging. Towards the end it will go to voltage mode 4.2*16cells should read 67.2.

the power supply should then go green when the current level falls below 250ma. 

Remove the battery. 

Connect a 120v incandescent light bulb to the battery and monitor the voltage. Record every 30 seconds for say 10 minutes. Maybe longer if the voltage does not drop too much .

The resistance of an 60watt,120vac lightbulb is about 240 ohms when it gets hot. So 67.2/240 is about 280 mull amps.

now be careful  these battery packs can push out 10amps easily for a 1P fully charged.

ideally it is easier to do say 4 light bulbs in parallel and track the voltage for 60 minutes. That would be approximate 1 amp for 1 hour . It should give a good pass fail approximation to determine if your pack is defective. mah is milliamp hour.

 

[Vik's]

2 hours ago, Paddylaz said:

Is there any way to tell if your wheel has a 'bad cell(s)' without opening it all up??

Ps. Im constantly impressed by the electrical knowledge of some of the people on this forum! Way over my head!

More often than not, bad cells leads to EUC not getting 100% charge even after a few hours. So checking the app once in a while after full charge is an essential thing to do.

[Rehab1]

Glad you just walked away with a few scraps!

It is interesting the amount of data we acquire as members are putting higher mileage on their wheels!  

The fact that a single cell can go bad and cause a shut down is disturbing! I was brought up to respect preventative maintenance! So where does the preventative part enter into this equation? ( I am not a battery expert either).

[Rehab1]

5 hours ago, Paddylaz said:

Is there any way to tell if your wheel has a 'bad cell(s)' without opening it all up??

 

I was just researching this subject at Battery University. High-voltage battery packs require careful cell matching especially when drawing heavy loads or when operating at cold temperatures. With multiple cells connected in a series, the possibility of one cell failing is real and this would cause a failure. To prevent this from happening a solid state switch that would  bypass the failing cell and allow continued current to flow is an option.

Multi-cell battery protection systems are not new. If single cell failure can disrupt the entire battery pack why not incorporate IC technology that would cut the defective cell out of circuit if the cell is being overcharged or over-discharged?

http://www.eedneurope.com/news/multi-cell-battery-pack-monitor-smallest-li-ion-pack-designs

 

 

 

[noisycarlos]

PS: In case it's helpful. Here's the video of me tearing down and checking the voltages of the defective battery pack: 

 

[esaj]

13 hours ago, Rehab1 said:

I was just researching this subject at Battery University. High-voltage battery packs require careful cell matching especially when drawing heavy loads or when operating at cold temperatures. With multiple cells connected in a series, the possibility of one cell failing is real and this would cause a failure. To prevent this from happening a solid state switch that would  bypass the failing cell and allow continued current to flow is an option.

Multi-cell battery protection systems are not new. If single cell failure can disrupt the entire battery pack why not incorporate IC technology that would cut the defective cell out of circuit if the cell is being overcharged or over-discharged?

http://www.eedneurope.com/news/multi-cell-battery-pack-monitor-smallest-li-ion-pack-designs

The BMSs usually have special protection ICs that oversee the battery status, but mostly that's exactly what causes the wheel to just shutdown in case voltages drop too much. For example, Cranium tore down his Ninebot back in the day, and found out that the BMS uses SH367004-lithium battery protection/balancing chips, unfortunately the datasheet's in Chinese, here's a google translate of the overview:

Switch between 3/4/5 tandem applications via the SEL0 / SEL1 pin 
High-precision voltage detection function: (for single-cell batteries) 
  -Overcharge protection threshold voltage: 3.3V - 4.5V (50mV a file) Threshold voltage accuracy: ± 25mV 
  -Overcharge protection release voltage 1 : 3.2V - 4.5V Threshold voltage accuracy: ± 50mV 
  -Over discharge protection threshold voltage: 1.8V - 3.0V (100mV a file) Threshold voltage accuracy: ± 50mV 
  -Over discharge protection release voltage 2 : 1.8V - 3.4V Threshold voltage accuracy: ± 100Mv 
  
Two-stage discharge overcurrent detection function: 
  - discharge overcurrent 1 protection threshold voltage: 0.05V - 0.3V (50mV a file) Threshold voltage accuracy: ± 15mV 
   - discharge overcurrent 2 protection threshold voltage: 0.2V - 1.0V (100mV a file) Threshold voltage accuracy: ± 100mV 
  
Two-stage charge overcurrent detection function:
   - Charge overcurrent 1 Protection threshold voltage: 0.05V - 0.3V (50mV first gear) Threshold voltage accuracy: ± 15mV
    - charge overcurrent 2 protection threshold voltage: 0.1V - 0.5V (100mV a file) Threshold voltage accuracy: ± 40mV 
 Charge and discharge temperature protection function: 
  - Charging Low Temperature Protection Threshold Temperature: -20 ° C, -10 ° C, 0 ° C Threshold temperature accuracy: ± 2 ° C (typical) 
  - Charge and discharge High temperature protection threshold temperature: 50 ° C, 60 ° C, 70 ° C Threshold temperature accuracy: ± 2 ° C (typical) 
Balance function 3 : 
  - balanced open threshold voltage: 3.1V - 4.4V (50mV a file) Threshold voltage accuracy: ± 25mV
Wire break detection function 
External capacitor can be set to overcharge protection delay, over discharge protection delay, discharge Overcurrent 1 protection delay and charge overcurrent 1 protection delay 
Charge / discharge overcurrent 2 protection delay and temperature protection delay Internal fixation 
CTLC / CTLD pin gives priority to CHG / DSG pin output 
Wide operating voltage range: 3V - 26V 
Wide operating temperature range: -40 ° C to 85 ° C 
Can be used in cascade 
Low power consumption: 
  - Normal operating current consumption: 25µA (typical) 
  - Low power consumption current consumption: 4uA (typical) 
Package: 24-pin TSSOP

Overdischarge status 
When the arbitrary section of the cell voltage is less than the overdischarge detection voltage (V DV ), and this state duration exceeds the overdischarge detection delay (t DD ), the SH367004 series The DSG pin outputs a GND level to turn off the discharge MOS tube.
The above state is referred to as an overdischarge state. When the SH367004 is used as the master chip, the overdischarge status is released (the system does not enter the low power state) when any of the following conditions are met:  
  (1) The CHSE pin voltage of the SH367004 is higher than GND (not connected to the charger), and the voltage of the overdischarge protection is higher than the overdischarge Pressure (V DRV ) 
  (2) The CHSE pin voltage of the SH367004 is less than GND and the CHG pin is output high (charging the charger and charging current), and all batteries The voltage is higher than the overdischarge detection voltage (V DV ); 
  
When the SH367004 is used as an auxiliary chip, the overdischarge status is released (the system does not enter a low power state) when any of the following conditions are met: 
  (1) Trigger over discharge protection The cell voltage is greater than the overdischarge recovery voltage (V DRV ) 
  (2) When the BALI pin of the SH367004 is input low (charging the charger and charging current), and all the cell voltage is higher than the overdischarge detection voltage (V DV )

So apparently no bypassing, the overdischarge protection will just shutdown the battery pack output via the discharge mosfets ("The DSG pin outputs a GND level to turn off the discharge MOS tube") if the cell voltage(s) drop too low. Don't know if there are ICs available with the possibility of bypassing a faulting cell, probably? That would at least keep things powered and assuming the firmware could detect the cell failure, it could then at least warn you with some beeping or whatever, and with enough power, tilt-back to tell you to stop...

EDIT: Actually, the original Firewheel packs had an extra wire coming to the mainboard, when it was disconnected, the mainboard would start to play a message saying something about "bad cell in battery" when turned on... don't know what would have happened if there really was a bad cell and it would detect it during riding, I only tested it with the mainboard out of the shell, but at least it apparently could detect cell failure. Maybe I could some day open up the heatsink of the BMS and check what chip(s) it used for monitoring.

[Carlos E Rodriguez]

I would just do a charge and discharge test. Much simpler to tell if the pack is good or bad. 

If you find the pack is bad then you can get fancy about figuring out specific issue. 

But before you open the pack you need to know what you are doing. 

First determine if it is defective by measuring actuall capacity by fully charging, measure unloaded volts after one hour resting, then discharge with proper load or test tool.

[Rehab1]

2 hours ago, esaj said:

The BMSs usually have special protection ICs that oversee the battery status, but mostly that's exactly what causes the wheel to just shutdown in case voltages drop too much. 

Unfortunately as you stated the BMS shuts the whole wheel down with a voltage drop. Bad outcome! The more I research this subject the more I am elucidated on the ongoing R&D in this area.

AMS, an Austrian provider of analog ICs and sensors, has introduced a simpler and more robust method of monitoring and balancing cells in lithium-ion battery systems.The company has implemented the new architecture in a highly integrated chip called the AS8506, that performs distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) checks and passive or active cell balancing. It’s designed to work with all lithium-based cell chemistries, as well as EDLCs (aka supercaps or ultracaps).

We know that In conventional systems, a complicated algorithm running remotely on a microcontroller decides which cells have to be balanced. The new architecture supported by the AS8506 can control individual cell balancing locally enabling designers to implement a more streamlined cell management system that eliminates the host controller, complex software and vulnerable serial communication links.

 An analog circuit in the AS8506 compares up to seven cell voltages ( IC would need to be enhanced/modified to monitor all the cells in our EUCs) contained against an internal or external reference with an accuracy of 1 mV, to support cell balancing and cell monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5 mV and reported to a host controller.

“The AS8506 marks a breakthrough in cell monitoring – not an incremental improvement on previous cell monitoring ICs, but a completely new approach”, said Product Manager Manfred Brandl. “By offering local cell and temperature monitoring, the AS8506 gives system designers a simple and robust means to implement a battery management system, with just a simple microcontroller required for basic system functions.”

I am certain that the AS8506 or similar ICs would inflate the cost of EUC production models. The question is: Would members be willing to pay an additional premium for increased safety?

[US69]

18 hours ago, Rehab1 said:

Glad you just walked away with a few scraps!

It is interesting the amount of data we acquire as members are putting higher mileage on their wheels!  

The fact that a single cell can go bad and cause a shut down is disturbing! I was brought up to respect preventative maintenance! So where does the preventative part enter into this equation? ( I am not a battery expert either).

Yip! thats disturbing....and the reason why i like multiple parallel/daisy chained packs..8p,6p,4p.....and see the the adding of more and more cells to a seriell system (16->20->24 on monster 100volt???) very scepitcal, as this highers the chance of a one batterie fault...

The V3....afaik, in the low version only has a ONE seriell 20s system...so when one batterie dies.....not so good!

 

But if that here is the case...nobody knows, could be nearly all imaginable faults!

To be on the safe side, i would try to simulate some hefty amp draws by leaning, kneeing on the standing wheel, when it is in full charge state...to see if it can handle that power draw!

It is not as easy to reach the cells as on the Ks or GW's....when i remember correctly!

And just to say it: as you see Inmotion can have cutouts like all other brands to....in the end all wheel run on the same cells!

[US69]

5 minutes ago, Rehab1 said:

Unfortunately as you stated the BMS shuts the whole wheel down with a voltage drop. Bad outcome! The more I research this subject the more I am elucidated on the ongoing R&D in this area.

AMS, an Austrian provider of analog ICs and sensors, has introduced a simpler and more robust method of monitoring and balancing cells in lithium-ion battery systems.The company has implemented the new architecture in a highly integrated chip called the AS8506, that performs distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) checks and passive or active cell balancing. It’s designed to work with all lithium-based cell chemistries, as well as EDLCs (aka supercaps or ultracaps).

We know that In conventional systems, a complicated algorithm running remotely on a microcontroller decides which cells have to be balanced. The new architecture supported by the AS8506 can control individual cell balancing locally enabling designers to implement a more streamlined cell management system that eliminates the host controller, complex software and vulnerable serial communication links.

 An analog circuit in the AS8506 compares up to seven cell voltages ( IC would need to be enhanced/modified to monitor all the cells in our EUCs) contained against an internal or external reference with an accuracy of 1 mV, to support cell balancing and cell monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5 mV and reported to a host controller.

“The AS8506 marks a breakthrough in cell monitoring – not an incremental improvement on previous cell monitoring ICs, but a completely new approach”, said Product Manager Manfred Brandl. “By offering local cell and temperature monitoring, the AS8506 gives system designers a simple and robust means to implement a battery management system, with just a simple microcontroller required for basic system functions.”

I am certain that the AS8506 or similar ICs would inflate the cost of EUC production models. The question is: Would members be willing to pay an additional premium for increased safety?

there is a little fault, when you think that would help at all...

We have multiple parallel packs....when ONE of this packs has a dead cell...it HAS TO be taken out of the complete daisy chained or paralled system! Because All Parallel packs have to be on the same voltage, otherwise you could end up with a bomb or real desasterbecause to much difference in voltage of the packs...

 

Thats also why i warn, just to use simply parallel batterie packs in a simple DIY y-cable way...as you may then not have all BMS protections anymore....and a dead cell(ergo pack) could then lead to desaster fault of whole system!

 

[Rehab1]

4 minutes ago, KingSong69 said:

there is a little fault, when you think that would help at all...

We have multiple parallel packs....when ONE of this packs has a dead cell...it HAS TO be taken out of the complete daisy chained or paralled system! Because All Parallel packs have to be on the same voltage, otherwise you could end up with a bomb or real desasterbecause to much difference in voltage of the packs...

 

Thats also why i warn, just to use simply parallel batterie packs in a simple DIY y-cable way...as you may then not have all BMS protections anymore....and a dead cell(ergo pack) could then lead to desaster fault of whole system!

 

Logical! I emailed Battery University yesterday to inform them about some of our BMS and LiPO concerns in the EUC community. I know they are very busy. Will be interesting to see if they personally respond. Would be great to have an open channel to their talent!

[US69]

Just now, Rehab1 said:

Logical! I emailed Battery University yesterday to inform them about some of our BMS and LiPO concerns in the EUC community. I now they are very busy. Will be interesting to see if they personally respond. Would be great to have an open channel to their talent!

Imho....these problems are adressed in our wheels!

A dead cell leads to the shutdown of one pack, but not the whole wheel...Here on the V3 with only one seriell system its bad...

 

but on our ACM, mSuper v3, Monster , ks16/18...all is fine..

[esaj]

48 minutes ago, Rehab1 said:

Unfortunately as you stated the BMS shuts the whole wheel down with a voltage drop. Bad outcome! The more I research this subject the more I am elucidated on the ongoing R&D in this area.

AMS, an Austrian provider of analog ICs and sensors, has introduced a simpler and more robust method of monitoring and balancing cells in lithium-ion battery systems.The company has implemented the new architecture in a highly integrated chip called the AS8506, that performs distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) checks and passive or active cell balancing. It’s designed to work with all lithium-based cell chemistries, as well as EDLCs (aka supercaps or ultracaps).

Active cell-balancing sounds better, currently it seems that all the BMSs use passive balancing with bypassing the cell once it reaches full voltage (so no balancing unless you charge all the way "to the brim").

 

Quote

We know that In conventional systems, a complicated algorithm running remotely on a microcontroller decides which cells have to be balanced. The new architecture supported by the AS8506 can control individual cell balancing locally enabling designers to implement a more streamlined cell management system that eliminates the host controller, complex software and vulnerable serial communication links.

It would seem that in most "conventional EUCs", there is no microcontroller on the BMS-boards, or any serial- or otherwise data transfer to the mainboard (except that one line in the Firewheel BMS & mainboard), it's just a few ICs (if that) and "basic" components  

I took a peek at the Firewheel-BMS I have, no MCUs there, actually it uses a lot of smaller circuits made from some smaller chips (apparently one per cell), although I didn't start looking for the codes right now. The "upside" of having no programmable logic on the board would be that there's no chance of firmware bugs   The "bad cell" -"information" sent to the mainboard is just voltage-level signal.

 

Quote

 An analog circuit in the AS8506 compares up to seven cell voltages ( IC would need to be enhanced/modified to monitor all the cells in our EUCs) contained against an internal or external reference with an accuracy of 1 mV, to support cell balancing and cell monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5 mV and reported to a host controller.

The SH367004 -chip mentioned above (used in at least older Ninebots) only supports up to 5 cells per chip, so probably they used 3 of them to monitor all of the 15 cells in series that Ninebots use. Don't know if that can be done with the AS8506, I would need to read through the datasheet, but at least right now don't have the time for that...

 

Quote

I am certain that the AS8506 or similar ICs would inflate the cost of EUC production models. The question is: Would members be willing to pay an additional premium for increased safety?

Even if the chip itself wouldn't be very expensive, of course it would push up the price at least somewhat (new design and testing, manufacturing changes etc). And that specific chip isn't from the cheapest end ( https://www.digikey.com/products/en/integrated-circuits-ics/pmic-battery-management/713?k=as8506  about $6-7/piece, when ordering 1000 or more). 

 

 

35 minutes ago, KingSong69 said:

there is a little fault, when you think that would help at all...

We have multiple parallel packs....when ONE of this packs has a dead cell...it HAS TO be taken out of the complete daisy chained or paralled system! Because All Parallel packs have to be on the same voltage, otherwise you could end up with a bomb or real desasterbecause to much difference in voltage of the packs...

Didn't actually think of that, you're right. If one of the packs drops about one cells' worth of voltage, the rest of the parallel packs will try to charge it, and since there's very little resistance between the packs, that's going to be bad...

Actually, I shouldn't be using words like "try to charge it" or "something decides to do this and that" or whatever, since they're just circuits working under laws of physics, they don't "think" or have any "smart behavior"...  At least as long as there's no programmable logic involved.

 

Quote

Thats also why i warn, just to use simply parallel batterie packs in a simple DIY y-cable way...as you may then not have all BMS protections anymore....and a dead cell(ergo pack) could then lead to desaster fault of whole system!

That was my logic when going with separate packs each having their own BMS for my custom packs... The packs are individual, can be separated, and the failure of a single pack won't affect the others (at least as long as the BMS is working correctly )

 

27 minutes ago, KingSong69 said:

Imho....these problems are adressed in our wheels!

A dead cell leads to the shutdown of one pack, but not the whole wheel...Here on the V3 with only one seriell system its bad...

but on our ACM, mSuper v3, Monster , ks16/18...all is fine..

True, as long as there's more than one BMS (some wheels seem to stack multiple packs behind a single BMS, probably paralleling them on cell-level?), preferably one for each parallel series. Unfortunately, for example the KS16 cannot fit my custom packs because the separate BMSs and their heatsinks make the packs too thick.

[US69]

24 minutes ago, esaj said:

That was my logic when going with separate packs each having their own BMS for my custom packs... The packs are individual, can be separated, and the failure of a single pack won't affect the others (at least as long as the BMS is working correctly )

About this i had a discussion with Chris from 1rad....

His statement was, even with own BMS for each pack, the only "safe" solution then is to "daisy chain" the packs...

Just parallel them by y-cable....would bypass the BMS protection and in case of a "one pack failure" could lead to dangerous situation/disaster.... 

Thats also the reason why newer GW's have an seperate and exclusive connection beside the normal y-cable. This extra connection is for communication between the BMS's .....

Please dont ask me for exact reasons, why this would 'bypass'....i am just quoting Chris...my knowledge ends here....