SAFETY ADVISORY: Faulty charger may lead to risk of 16X battery fire

[Chriull]

15 hours ago, JZT-Colorado said:

Could it be that the rapid charger just isn’t communicating properly with the BMS?

There is no communication between charger and the wheel - the charger just has some voltage and some current thresholds to change his behaviour. These of course could at wrong values.

Quote

Here’s a clue:

I noticed with my own 16X that when I set my rapid charger to charge to only 80%, it kept charging all the way to 90%+... at which point I just unplugged it as I didn’t want to charge to 100%.  But if it kept charging past 100%, it would probably lead to a similar result. 
 

Hmmm...

 

1 hour ago, RetroThruster said:

Mine did the same thing, I had it set to stop at 80% but when I checked WheelLog it stated that it was at 92%, at this point, I stopped charging, I'm a little fuzzy on what the charger was reading at at that time but it seems like it was just barely over 80% but had stayed there for quite some time, I wonder if it's a combination of the charger charging at 88v and the BMS not recognizing the issue and stopping it AND the charger not stopping at the selected percentage, if at all.  

Charging with cutting of at a certain voltage always shows too much charge while charging. THe correspondance battery voltage to battery charge is only correct if one lets the battery settle some time.

From https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Charge V/cell	Capacity at cut-off voltage*	Charge time	Capacity with full saturation
3.80 3.90 4.00 4.10 4.20	~40% ~60% ~70% ~80% ~85%	120 min 135 min 150 min 165 min 180 min	~65% ~75% ~80% ~90% 100%

Table 2: Typical charge characteristics of lithium-ion. Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high voltage.

 

So if one charges up to 4.2 volt, the app shows (wheel reports) falsely 100%, but the battery voltage will settle to something around this 85% charge after some time.

So if one charges up to 4.1 volt, the app shows (wheel reports) falsely ~90%, but the battery voltage will settle to something around this 80% charge after some time.

...

Edit: As all of this stuff could be almost way too Simple, EUCs show some (quite big) range as 100% - from 4.2V downto somewhere not to far from 4.1V. (don't remember exactly - maybe 4.13V?)

So when a battery has in reality 90% (4.1V) the wheel/app just started to leave the 100% area...

Edited October 16, 2019 by Chriull

[JZT-Colorado]

1 hour ago, RetroThruster said:

Mine did the same thing, I had it set to stop at 80% but when I checked WheelLog it stated that it was at 92%, at this point, I stopped charging, I'm a little fuzzy on what the charger was reading at at that time but it seems like it was just barely over 80% but had stayed there for quite some time, I wonder if it's a combination of the charger charging at 88v and the BMS not recognizing the issue and stopping it AND the charger not stopping at the selected percentage, if at all.  

I completely agree.

Although the charger outputs at a constant voltage (the “size” of the electron pipe, which should remain at 84.2V and can be see on the charger readout when the charger is on but not yet plugged into the EUC), it does vary the amperage (the rate of “flow” of electrons inside the pipe) depending on the current output voltage of the batteries.  The EUC's BMS controls the output voltage of the batteries, and thus “controls" the output amperage of the charger.

This leads us to postulate that there are two probable reasons a fire like this could have occurred:

1. The BMS had a fault in output voltage and thus incorrectly "communicated" to the charger that the batteries achieved full capacity, and thus allowed the charger to overcharge the pack and cause the battery damage that could lead to a fire.

2. The charger either had a fault or for some other reason did not lower its output amperage when the batteries reached their maximum voltage threshold, thus overcharging the batteries and leading to the battery damage and fire.

In my opinion, and based on my and @RetroThruster's observations, the problem appears to be #2, as the charger when plugged into a 16X does not automatically shut-off when the charger is set to 80% and the 16X's battery pack then reaches 80% capacity, and thus it is likely it also does not lower it's output amperage when it reaches 100% either.  In the case of the user who experienced the fire, if his charger kept charging after the battery reached 100% rated capacity, the output voltage of the battery (not the charger) would then exceed the rated voltage of 84.2V, which would readout on the charger (the 88V the user saw), and cause the damage and subsequent fire.

My 2-pence…

Edited October 16, 2019 by JZT-Colorado

[Jason McNeil]

Sorry I've been away from the forums for so long, it's been difficult just to keep up managing the email workload. 

Wanted to address some of the obvious concerns raised here: 
- Normal charging procedure for this JR-T450 charger,  when plugging into an outlet, the LCD display will show the charger's registered voltage, which should be 84.2v +/- .3v. Once charging is complete, it will wind down displaying 0.00v, pressing either the reset button, or disconnecting from the outlet, will reset it. The addition of the LCD display was considered a safety feature, providing the Operator with information about the current state-of-charge & for troubleshooting charger problems.   
- Partial charging: this charger is programmed to have a termination point of 4.05v @ 80%, or 81v & 4.1v @90% 82v, as @Chriull has pointed out, there's a subsidence effect where the voltage will drop off by about 0.5v @ 5A charging current
- 5A Current Safety: The failure is almost certainly not attributable to the current; in the 20s6p configuration, the pack itself is capable of charging at 10A & still be well within the 'normal' charging spec. Recall that when the 16X was first released, KS advertised the max rate of charge of 10A. I have always tried to stay on the side of caution recommending charging not exceed <5-6.5A rapid + standard charger 
- Charger Abnormalities: whatever had caused this particular charger to go psycho (it had been functioning perfectly normal for 3 weeks), it had exhibited a couple abnormalities—'1  . ' readout, clicking sound, overshooting past the 84v. The lab results will reveal if this is a one-off manufacturing error, or a design fault, where all these chargers are at risk.  
- Why didn't the BMS prevent the overcharge?: KS sent me a video of their battery pack testing procedure, evidently, they do perform over-charge testing, but this is a couple volts over the 84.2v. It's just a supposition, but if the charger was pumping out an irregular pulsed DC output, perhaps the BMS requires a min_time threshold to shunt the charge input, or the voltage exceeded the BMS MOSFETs max voltage, this may have blown with the gate open, similar to what we see when the in a controller failure where the motor has a lot of resistance when rotated by hand.   

  

Edited October 16, 2019 by Jason McNeil

[Seba]

2 hours ago, RetroThruster said:

Mine did the same thing, I had it set to stop at 80% but when I checked WheelLog it stated that it was at 92%, at this point, I stopped charging, I'm a little fuzzy on what the charger was reading at at that time but it seems like it was just barely over 80% but had stayed there for quite some time, I wonder if it's a combination of the charger charging at 88v and the BMS not recognizing the issue and stopping it AND the charger not stopping at the selected percentage, if at all.  

Don't look at the percents. They differ from app to app and are only very rough information about battery charge. Always look at the battery voltage! Voltage is the key parameter that will let you know of battery state of charge. When your battery voltage is 84 V it's near to full charge. If battery voltage goes above 84.5 V you should immediately disconnect your charger and inspect its output voltage with precise multimeter. Why? Because even voltage measurement made by wheel mainboard may be off. So wheel may read battery voltage as 84.5 V but real voltage will be just 83.9 V.

Pro tip for every EUC owner: buy a decent multimeter. It's a very valuable tool for inspecting and checking your electrical things. I think having decent multimeter and basic knowledge how to use it is a good thing. Multimeter is far more versatile than Charge Doctor or any other tool. You can inspect wiring, check resistance/shorts/open circuits, measure currents, voltages, temperature etc.

[Chriull]

3 minutes ago, Seba said:

Pro tip for every EUC owner: buy a decent multimeter.

Just some info what "decent" could mean:

 

[RetroThruster]

3 hours ago, Seba said:

Don't look at the percents. They differ from app to app and are only very rough information about battery charge. Always look at the battery voltage! Voltage is the key parameter that will let you know of battery state of charge. When your battery voltage is 84 V it's near to full charge. If battery voltage goes above 84.5 V you should immediately disconnect your charger and inspect its output voltage with precise multimeter. Why? Because even voltage measurement made by wheel mainboard may be off. So wheel may read battery voltage as 84.5 V but real voltage will be just 83.9 V.

Pro tip for every EUC owner: buy a decent multimeter. It's a very valuable tool for inspecting and checking your electrical things. I think having decent multimeter and basic knowledge how to use it is a good thing. Multimeter is far more versatile than Charge Doctor or any other tool. You can inspect wiring, check resistance/shorts/open circuits, measure currents, voltages, temperature etc.

I learn something new every day here, I really appreciate that and will keep an eye on the voltage as well!

[mrelwood]

14 hours ago, Chriull said:

- Charger output and mainboard is behaving fine, but some cells are dead. I have no idea how this will behave?

The two occasions when cells died on my 16S, both times the BMS succesfully interrupted every single charging event once the 15 healthy pairs had reached the overvoltage limit, which was about 63.0V for the 67.2V wheel.

 

[Chriull]

4 hours ago, mrelwood said:

The two occasions when cells died on my 16S, both times the BMS succesfully interrupted every single charging event once the 15 healthy pairs had reached the overvoltage limit, which was about 63.0V for the 67.2V wheel.

Yes! Should be some CC up until the first cell reaches cut-off threshold - should be easily detectable to warn the user.

[esaj]

On 10/16/2019 at 6:22 PM, JZT-Colorado said:

I completely agree.

Although the charger outputs at a constant voltage (the “size” of the electron pipe, which should remain at 84.2V and can be see on the charger readout when the charger is on but not yet plugged into the EUC), it does vary the amperage (the rate of “flow” of electrons inside the pipe) depending on the current output voltage of the batteries.  The EUC's BMS controls the output voltage of the batteries, and thus “controls" the output amperage of the charger.

This leads us to postulate that there are two probable reasons a fire like this could have occurred:

1. The BMS had a fault in output voltage and thus incorrectly "communicated" to the charger that the batteries achieved full capacity, and thus allowed the charger to overcharge the pack and cause the battery damage that could lead to a fire.

I'm fairly certain that the above is wrong, but if I'm wrong, somebody please do correct me, always happy to learn.

In King Songs, the BMS does not "output" voltage towards the charger, there's a reverse polarity protection in the charging side which as a side-effect also prevents reading the battery voltage from the charge port with a multimeter (you might see a few volts as the mosfets leak a tiny bit of current "backwards", but not the actual voltage). On the other hand at least some older Gotways, if not also all the new ones, don't have reverse polarity protection, and you can read the voltage from the charge port.

However, the charger does not "use" this voltage reading whether it's there or not, instead, the charger drops its own output voltage if the current limit (like 5A) is hit until the current stays at that limit. It cannot "directly" control the output current, but the control is done through altering the output voltage. This is the CC (Constant Current) -charging phase. Once current stays within this limit when hitting the maximum output voltage, the CV (Constant Voltage) -phase begins, where it just keeps the output voltage at the maximum (like 84V), and the current dies out slowly as the battery charges and the battery voltage goes up towards the charger voltage (the difference between the charger output voltage and battery voltage drops, since the resistance between the two is more or less constant, the current drops:  I = U/R).

 

Quote

2. The charger either had a fault or for some other reason did not lower its output amperage when the batteries reached their maximum voltage threshold, thus overcharging the batteries and leading to the battery damage and fire.

In my opinion, and based on my and @RetroThruster's observations, the problem appears to be #2, as the charger when plugged into a 16X does not automatically shut-off when the charger is set to 80% and the 16X's battery pack then reaches 80% capacity, and thus it is likely it also does not lower it's output amperage when it reaches 100% either.  In the case of the user who experienced the fire, if his charger kept charging after the battery reached 100% rated capacity, the output voltage of the battery (not the charger) would then exceed the rated voltage of 84.2V, which would readout on the charger (the 88V the user saw), and cause the damage and subsequent fire.

My 2-pence…

I'd speculate (like others have before) that in this case the faulty charger output voltage has raised high enough to destroy the BMS charging-side protection mosfets. Never seen the KS BMS, but I'd guess they're using something like 100V max mosfets there, and a high enough voltage spike from the charger has fried the protection, allowing the cells to overcharge. They might have gotten severe damage at this point, but not enough to cause a fire. Once the badly damaged cells were charged using the normal charger, an internal short circuit inside a cell or such caused the temperature to raise beyond the critical "thermal runaway" -point (something like 125...150 Celsius), at which point the cell catches fire that keeps feeding itself. But that's all just guesswork.

Edited October 19, 2019 by esaj

[JZT-Colorado]

3 hours ago, esaj said:

... if I'm wrong, somebody please do correct me, always happy to learn.

...

Me too!  🙂

[Planemo]

On ‎10‎/‎16‎/‎2019 at 4:31 PM, Jason McNeil said:

 or the voltage exceeded the BMS MOSFETs max voltage, this may have blown with the gate open,

....making it a completely pointless overvoltage safety feature. Mechanical or solid state fuses could easily deal with this, maybe also run an RCD while you're at it. Anything to deal with an unusual voltage situation. At no point should this issue have to cause damage to the BMS or, god forbid, the battery. There are more than enough electrical solutions to prevent an input overvoltage causing damage to other components.

[EvoKnvl]

Update from an email that I received  from eWheels.  Basically it looks like the charger was exposed to rain and water causing it to fail. 

Good afternoon, 

 

I have just received the lab results back for the defective charger investigation: the conclusion that the Engineers reached, was that because the charger used on a boat & exposed to rain/wash, component corrosion deterioration built up, resulting in this over-charge situation (full lab results attached).

 

The charger's circuit-board is elevated to offer some primary protection against water, but is not designed to be left in an outdoor environment. 

 

Conclusion:   

It ought to be safe to continue using the charger. Prior to use, please always check the display that the voltage is showing ~84v, after pressing the reset button, but before plugging into the Wheel. If the voltage is elevated beyond 84.5v, NOT USE the charger & let use know immediately; keep the charger in a dry environment.   

 

Thank you & have a good day,

 

Jason 

 

 

Edited November 11, 2019 by EvoKnvl

[RetroThruster]

That makes me feel better, now I'm not gonna hover over mine while charging:)

[EUC Custom Power-Pads]

2 hours ago, EvoKnvl said:

The charger's circuit-board is elevated to offer some primary protection against water, but is not designed to be left in an outdoor environment. 

Good to know , then I don't take my 16X into the bathtub anymore while it's just being charged. But luckily nothing has happened to me yet.