Begode 900Wh Battery Recall Options

[Jason McNeil]

First off, I wanted to thank everyone for their support during this difficult period. The immediate priority is to work on building up the parts supply, reestablish some sort after-service capability, but it's going to take time—air-freight costs are triple the 'regular' rates, while containers are taking an extra 1-2 months to arrive.

A related activity to this event is pushing forward the Begode RS/MSP/Nikola+ battery recall project. Initially the plan was to recall the existing 900Wh 21700 M50LT packs, establish the individual cell IR baseline values, dispose of packs with out-of-range cells, install the LiTech BMS with enhanced short protection, 30A fuses, temperature probes, but the concerns are that after undergoing all this work the risks may still be present without exhibiting any direct failure to fully charge symptoms—Adam outlined this topic in his video from this morning.  

With the previous incidents, I believe the scope of the recall is going to have to be to recommend that Customers dispose of their existing 900Wh packs for the Nikola+, RS, MSP [the risks are too great] then await for a replacement packs with better preventative measures in place, in tandem with trying to push for Begode to finally implement some maximum output current limiting in their firmware—this can be done through a firmware updating tool if the previous generation do not have over-the-air updates.  

 

 

Edited November 8, 2021 by Jason McNeil

[Bumblebees]

Should the Monster Pro be added to this list of wheels needing a battery recall?

[Ronin Ryder]

What about the Begode Mpro , EX and EXN? To sum up, even the newest wheels with 900wh packs potentially need to see their packs recalled? Thanks. 

Edited November 8, 2021 by Ronin Ryder

[FlyboyEUC]

I would think that any wheel with a 900Wh 21700 M50LT pack would be at risk but maybe the newer wheels: EX(.N) and MP24 have some recent changes that have been made? Clarification on this would be nice.

 

Edit: I now recall that in Wrong ways video, he says the bigger wheels are safer because they have more packs in parallel, and thus less stress on the batteries.

Edited November 8, 2021 by FlyboyEUC

[Jason McNeil]

1 hour ago, Bumblebees said:

Should the Monster Pro be added to this list of wheels needing a battery recall?

There is less risk for the 3-4x battery pack EX.N/EX & MonsterPro, the stress per/cell should be substantially less in the 24s6p/24s8p configurations. For the moment, the priority is the Nikola+, MSP, & RS series. 

Also, there are no historical incidents of the 18650 800Wh packs, more cells in parallel; it could also be that certain cell types are more vulnerable than others, all the cases have been with the LG M50LT cells, which are what Begode use exclusively in the 21700 format. 

[meepmeepmayer]

Do you believe that a too high current is the cause for battery fires starting? Is there any information supporting this idea?

[conecones]

33 minutes ago, meepmeepmayer said:

Do you believe that a too high current is the cause for battery fires starting? Is there any information supporting this idea?

I doubt we will ever get anything more than circumstantial evidence given how difficult this would be to prove, but it is safe to say stressing a battery beyond its specified parameters will result in early failure.

But then again, so would any one or combination of the following:

• water intrusion
• regularly charging to 80%-90% (i.e. not properly balancing)
• regularly draining to low battery %
• previously shorted out/damaged motherboard causing unknown damage to battery
• poor QC cells, faulty wiring, malfunctioning BMS

Before everyone that owns a Nikola+/MSP/RS just dumpsters their wheel, it would be good to self-evaluate your risks with the Bathtub Curve in mind. If you haven't been abusing your wheel regularly, it runs fine and charges to 100%, then personally I am not losing any sleep over it. If you ARE a self-identified EUC abuser, then accept the risk or change your ways 

I feel for the distributors/repair shops because that's where the highest risk for fires are located.  I mean these are the places where batteries/wheels that are KNOWN to be damaged/acting weird are sent! 

[RagingGrandpa]

4 hours ago, Jason McNeil said:

 

 

Adam's a good dude.

But, he speculates a lot on youtube, on topics outside his professional experience.

He raised the point that the continuous discharge rating of LG M50T is 7,275mA, or 29A for a 4p system. That's 2,610 W @ 90V.
He failed to consider how the pulsed discharge capability can be many times the sustained rating.
4p M50T, in an EUC whose controller overheats beyond 2500W sustained, is "within spec."
 

4 hours ago, Jason McNeil said:

Initially the plan was to recall the existing 900Wh 21700 [M50T] packs, establish the individual cell IR baseline values

How do you measure cell IR without breaking down the pack?
Perhaps you would measure the resistance of each parallel group?
 

4 hours ago, Jason McNeil said:

install the LiTech BMS with enhanced short protection, 30A fuses, temperature probes

You would retrofit the BMS to Gotway's existing pack assembly?
It would be concerning to desolder, bend, and re-solder all their nickel strips to the BMS PCB... especially as Gotway uses the cheap nickel-plated steel strips (risk of fatigue cracking).
 

4 hours ago, Jason McNeil said:

the concerns are that after undergoing all this work the risks may still be present

Right: a cell-internal fault can't be "made safe" by the BMS. As a best-possible outcome, the temperature would rise slowly, activate the BMS beeper, and the user would move the EUC outside before the inevitable runaway happens.

 

4 hours ago, Jason McNeil said:

push for Begode to finally implement some maximum output current limiting in their firmware

Hmm, I think they already do limit output current. To about 200A.

Adam was proposing that the controller should also limit input current. Today, Gotways do not.

The electrical design of the motor, and the (200A) motor current limit, effectively define the maximum possible battery current.
Reducing this input current further will directly reduce the safety margin of the EUC, and mostly at moderate-high speeds. This is the area of operation where we need the most power, for rider safety. Better to choose a battery system that can support the maximum theoretical power, than to cripple the performance using firmware.

 

Ultimately, my feeling is: LG M50T is an unreliable cell. Most of the time, it performs according to expectation; but there are some 5-10ppm of cells that get sold with internal defects that become catastrophic during their lifetime.
(...but we don't have root-cause evidence in any of the EUC pack fires, so my feelings can't be regarded as factual conclusions, just educated theory.)
As Adam mentioned, there are many competing models of cell. Hopefully EUC mfr's (and/or Ewheels) can source them in the necessary volumes at acceptable prices sometime soon.

Samsung 21700 50S is just amazing. I'd pay an extra $500 [per 1800wh EUC] to have it. But not an extra $2000!

[YourAubsome]

4 minutes ago, RagingGrandpa said:

Adam's a good dude.

But, he speculates a lot on youtube, on topics outside his professional experience.

I couldn't agree more.
 

Quote

Ultimately, my feeling is: LG M50T is an unreliable cell. Most of the time, it performs according to expectation; but there are some 5-10ppm of cells that get sold with internal defects that become catastrophic during their lifetime.

LG M50T cells are in the V11, S18, and S20. We don't see these wheels blowing up. I don't think we can say that the cells are unreliable. I think the Gotway is using them is unsafe. 

[RagingGrandpa]

8 minutes ago, sevin7 said:

LG M50T cells are in the V11, S18, and S20. We don't see these wheels blowing up.

A fair point!

It leads me to consider:

1. V11
   I think many shipped with Samsung 50E instead?
    
2. S20
   Does not exist as a consumer product yet
    
3. Volume
   I think the total number of cells used in V11's and S18's is much lower that the total number of cells used in [Nik MSP RS EX MonPro] to date. So we should expect lower frequency of occurrence in the lower-usage models.
    
4. Culling
   LG's distributor drops off a few thousand cells in a box.
   High-rigor pack assemblers test the cells themselves, before putting them into packs.
   If they're especially rigorous, they will reject cells outside a specific range of measurements (such as capacity, resistance/sag, even mass!).
   It could be that Gotway's pack builder isn't culling, or isn't culling as stingily as the competitors.
    
5. Good results with Gotway 18650 packs
   The Gotway BMS and controllers in the 18650 designs work nearly identically to the 21700 designs. There were no extra protections afforded to the 18650 packs, the firmware current limits are practically identical, and they've had a much better track record.
   So if the causes were truly "something Gotway is doing wrong," it would have to be a detail directly involved with 21700 pack assembly, that was somehow different than 18650 pack assembly...

.02

[RetroThruster]

Any idea of when the replacement packs will be available?    Looks my 8 month old Nik+ would be.  Anyone want a $2,100 paper weight:/  I'm gonna cross my fingers and hope that nothing happens, I'm easy on my wheels so here's hoping...

Edited November 9, 2021 by RetroThruster

[supercurio]

 

2 hours ago, meepmeepmayer said:

Do you believe that a too high current is the cause for battery fires starting? Is there any information supporting this idea?

Please correct if I'm wrong.
High drain scenarios tend to increase the amount of imbalance between cell groups, as the difference in capacity & internal resistance are amplified by the higher currents.

Trying to understand the cause of recent fire in Stockholm and another MSP HT pack that stopped charging to nominal voltage for another local rider, my own theory is currently:

• Generally powerful wheels and advanced riders: high drain rides increasing the cell group imbalance
• A portion of BMS in the Begode 900 Wh packs tend to fail to activate the safety mechanisms expected: cell group overcharge protection (charging), cell group low voltage (riding)
• The 900 Wh packs have no feedback mechanism:
  - They let users continue not only draining, but even riding with faulty cells, with the risk of discharging at high current to unsafe voltages (low) damaged cell groups
  - They let users attempt charging with cell faults.
  - They let users charge/discharge packs with the BMS itself being damaged.
• A typical failure of the 900 Wh pack BMS seem to break balancing. Speculating here but on Sherman it returns an error code (BT LOW), whereas on Begode packs the error is silent and the pack gradually becomes more unbalanced.
• The Begode packs typically are poorly sealed, still today, leading to water damage (original problem with the wheel that burn the house before its pack's repair)

All in all, we have various factors increasing the risk combined with lacklustre BMS features which makes them less resilient to failures.

IMO think the worst part is the lack of effort in implementing any kind of user feedback mechanism, which would help to make the system more tolerant to faults by informing the user of the pack's cells and BMS health.

 

Edited November 9, 2021 by supercurio

[YourAubsome]

1 hour ago, RagingGrandpa said:

Good results with Gotway 18650 packs
The Gotway BMS and controllers in the 18650 designs work nearly identically to the 21700 designs. There were no extra protections afforded to the 18650 packs, the firmware current limits are practically identical, and they've had a much better track record.
So if the causes were truly "something Gotway is doing wrong," it would have to be a detail directly involved with 21700 pack assembly, that was somehow different than 18650 pack assembly...

I'm not sure exactly which 18650 cell Gotway wheels your referring to (I know most new Gotway's use LG M50T), but I do know that basically every 18650 cell used in a PEV that I've seen has a higher discharge rate (per watt hour, since more 18650s are used than 21700s to get the same watt hour rating) than LG M50T cells.

The LG MG50T cells are simply not designed for high discharge. I've put about 400 miles on my S18, about 800 on my V11, and about 200 on my RS19 HT. I think I'm uniquely experienced in how much I've compared these wheels, especially with my high weight (210 lbs) and living in an area with extreme hills. These 3 wheels are very important for this comparison, because they all use the same LG M50T cells, but each uses a different number:

- S18: 60 cells

- V11: 80 cells

- RS19 HT: 96 cells

 

The S18 and V11 both use 20S (84v) and the RS19 uses 24s (100v). The S18 has the best safety protection by far. It has dynamic beeps that tell you when your going to overpower the wheel. The beeps kick in even at very low speeds any time your about to overpower the wheel, and the wheel is much easier to overpower when the battery is below 80% (and its easier to overpower as the battery goes  even lower). These beeps must be based on a combination of the current power output and the current battery level (or voltage). I have not seen such beeps in the V11, RS19, Sherman, mten3, or EX.N (these are all the wheels I've tested). All of the other wheels only beep based on speed and battery level, which is total BS, as I consume massively more power going up a 25* incline at 20 MPH weighing in at 210 lbs than your average 160 lbs rider on flat road.  Any ways, that is sort of off topic, but in order for KingSong to understand exactly how much power the wheel can put out at any given time, they had to test the battery cells extensively to see what they could put out at any given charge level. However, the S18 is actually the least safe wheel of the V11 and RS19 in terms of overpowering because its just way too easy to overpower when its battery is low (especially below 50%), and the beeps are often too slow of warning to stop you from overpowering the wheel (I've done it on accident many times at low speeds). Also, we can conclude that S18's lack of power is caused by the battery, because when its 100% charged, its a pretty nice wheel that I don't have to worry about overpowering too easily. 

The V11 has far more low end power than the S18. I find that I don't have to ride very cautiously to avoid overpowering the V11. This increased power must be possible because of the jump from 60 to 80 cells (obviously the controller and motor are more powerful too). I can still somewhat easily overpower the V11 at any given moment by just leaning into it really hard (the motor makes a sound and I can feel it giving out, if I push harder I will face plant). This ability to overpower the wheel also increases as the battery goes down in charge level. The V11 top speed is 5 MPH higher than the S18; they run the same voltage but the V11 has more power because its battery pack is capable of providing more power. 

The RS19 has more low end power than the V11, but surprisingly I wouldn't say its far more. I can still overpower the RS19 if I lean into it extremely hard (note: I have Clark pads on all my wheels), and its given out on me a few times when trying to do some pretty extreme off-road hill climbs, but I tried the same climbs side by side on the V11 and the RS19 only had a little more power (both were charged to about 90%). The RS19 has 96 cells vs the 80 in the V11, and its using a higher voltage. That higher voltage allows the RS19 to have a higher top speed than the V11 (38ish MPH vs 34ish MPH) without loosing its torque advantage throughout the power range (torque advantage granted mainly via the larger battery with corresponding controller/motor).

The youtube video in the first post basically says the reason for the recall is the Gotway wheels are consuming more power than the cells can safely provide. From my riding experience, the V11 appears to be providing roughly the same amount of power per LG M50T cell as the RS19 HT. Now this is something that is nearly impossible to measure, but I'm a little obsessive with my side by side testing of devices, and I tried the RS19 HT vs V11 side by side over and over again on many extreme hills, including tests where I rode the wheels until they gave out because the hills were so extreme (at low speed). I also found that the V11 has serious overheating issues and appears to have no built in safety measures to stop it from cooking its self (which Gotway wheels surprisingly have). Ultimately the wheel that has felt like its the best engineered product is actually the S18 (out of the wheels I've owned), which is surprising given how much I don't like the wheel 😂. 

[Gadgetfann]

If our Nikola batteries were replaced during the first recall in May, 2020 do we need to participate in the new recall too?

[Patrick Robert]

So, each cell/parallel pack of LG M50T can only deliver 7.3A, thus in a 4p configuration it means 29.2A max. Is that it? 
(The S18 with its 3p can reach no higher than 21.9A? Ouch!)

Now I understand why Veteran went with the Panasonic NCR18650GA for the Sherman, with its max discharge rate of 10A. In its 10p setup, it means 100A max? Wow. Interesting to be able to compare not just Wh, but also max amperage between wheels. 

For the Abrams they went with another 10A cell, the Samsung 50E if I'm correct. In its 6p setup, it means a max discharge of only 60A. Should be enough for me, but it's far from the Sherman's. 

I was wondering where the 7.3A was taken from exactly. Looking at the cell's datasheet, at section "4.2.4 Max. Discharge Current (Continuous)", the following figures are listed :
-20 ~ 10℃  0.5C (2,425mA)
10 ~ 25℃   3.0C(14,550mA)
25 ~ 55℃   1.5C (7,275mA)

So I see that Adam went with the "worse" case of 7.275A.

But what about riding in cold weather, if the batteries get below +10C, they could only deliver 2.425A max? So not even 10A for a 4p???

Edited November 9, 2021 by Patrick Robert

[Chriull]

8 hours ago, RagingGrandpa said:

especially as Gotway uses the cheap nickel-plated steel strips (risk of fatigue cracking).

 

8 hours ago, RagingGrandpa said:

Hmm, I think they already do limit output current. To about 200A

Imho these two points could easily be enough reason for the battery fires. 

Too high current peaks and/or overheating nickel strips should be enough to destroy/degrade the separators within the cells leading to (retarted) internal shorts and thermal runaway.

Other wheel manufacturers (maybe) just have better (firmware) current limits and/or stronger strips?

 

7 hours ago, supercurio said:

Please correct if I'm wrong.

High drain scenarios tend to increase the amount of imbalance between cell groups, as the difference in capacity & internal resistance are amplified by the higher currents.

High drain scenarious down to low charge states would be my assumption. Once single cell groups go below the ~3.3V average showing as 0% charge state.

Afair i read that different cell temperatures can support imbalances too. Which could be caused by high drain and insufficient/inequal cooling?

Quote

Trying to understand the cause of recent fire in Stockholm and another MSP HT pack that stopped charging to nominal voltage for another local rider, my own theory is currently:

From the reports in the fire & smoke topic there were imo also relatively new packs and i can't remember any report with mentioning of imbalanced packs or charging problems.

Also with quite regular post/reports of wheels of all manufacturers not charging to 100% about none of them was reported starting a fire!

As it seems imbalanced packs degenerated enough to pose a real fire risk already restrict riding performance enough to be discarded/replaced?

Quote

• Generally powerful wheels and advanced riders: high drain rides increasing the cell group imbalance

Imho not if wheels are nicely charged until green charger led shows up and not discharged too low! Just downto ?30/40? %

Quote

• A portion of BMS in the Begode 900 Wh packs tend to fail to activate the safety mechanisms expected: cell group overcharge protection (charging),

Any reports to back up this assumption? Serious cell overvoltage imho was only seldomly reported after serious s damage... Afair nothing GW specific?

Quote

•  
•  cell group low voltage (riding)

No wheel has this kind if warning. Maybe Inmotion/ninebot have?

Latest BMS report of a S18 showed just an IC to check cell overvoltage.

Quote

• The 900 Wh packs have no feedback mechanism:
  - They let users continue not only draining, but even riding with faulty cells, with the risk of discharging at high current to unsafe voltages (low) damaged cell groups
  - They let users attempt charging with cell faults.
  - They let users charge/discharge packs with the BMS itself being damaged.

Same with KS Bms. Likely too for other manufacturers, but not too much/all details are imho really known for all of them?

Quote

• A typical failure of the 900 Wh pack BMS seem to break balancing. Speculating here but on Sherman it returns an error code (BT LOW), whereas on Begode packs the error is silent and the pack gradually becomes more unbalanced.

According to 

(Report of ewheels statement) Bt low signifies that the voltages of the left and right pack are different, and not that there are imbalances within a pack. Edit: After rereading this post, i'm not so sure anymore - could mean internal pack imbalance reporting, too?

Quote

• The Begode packs typically are poorly sealed, still today, leading to water damage (original problem with the wheel that burn the house before its pack's repair)

Afair wet conditions/humidity was under suspucian with other begode fire reports, too?

Edited November 9, 2021 by Chriull

[Chriull]

1 hour ago, Patrick Robert said:

So, each cell/parallel pack of LG M50T can only deliver 7.3A, thus in a 4p configuration it means 29.2A max. Is that it? 
(The S18 with its 3p can reach no higher than 21.9A? Ouch!)

No, these are the maximum specified _continous_ currents from their datasheets.

6 hours ago, sevin7 said:

These beeps must be based on a combination of the current power output and the current battery level (or voltage

KS wheels have the 88% alarm, based on pwm duty cycle %. EUC World calls this value safety margin (100% - this duty cycle) showing 12% for this 88%.

[mrelwood]

 

6 hours ago, supercurio said:

• A portion of BMS in the Begode 900 Wh packs tend to fail to activate the safety mechanisms expected: cell group overcharge protection (charging), cell group low voltage (riding)

No EUC has cell group low voltage warning in any situation, not even a warning in the app. (Oh, except for the deceased Z10.) Your cells can get  lethally out of balance before you even know about it. If you don’t monitor the total voltage after a charge, a cell group can even die all the way to 0V and you might not know about it.

 That’s why I’m so much against undercharging (80%, 90%, whatever), since the only thing we can do to prevent the above, is to balance the cell groups blindly and religiously. And the only way to balance is to charge until the charger turns green. Preferably an hour or a few more.

6 hours ago, supercurio said:

• The 900 Wh packs have no feedback mechanism:
  - They let users continue not only draining, but even riding with faulty cells, with the risk of discharging at high current to unsafe voltages (low) damaged cell groups
  - They let users attempt charging with cell faults.
  - They let users charge/discharge packs with the BMS itself being damaged.

The V11 (and maybe some other modern EUCs as well) does have a bit more advanced BMS, but in general the above points apply to all EUCs, GW and others alike.

 Unless the latest models are different, no GW battery has any communication with the mainboard. Same goes for most of the other wheels.

 Getting truly smart BMS units in all wheel models would be a very important step forward in safety. But manufacturers won’t do it until they have to. So far Jason@Ewheels’ actions are the only notable ones I’ve seen pushing manufacturers in that direction.

6 hours ago, supercurio said:

• A typical failure of the 900 Wh pack BMS seem to break balancing. Speculating here but on Sherman it returns an error code (BT LOW), whereas on Begode packs the error is silent and the pack gradually becomes more unbalanced.

I’m not familiar with Sherman’s warning mechanism, but it is unlikely that it’s BMS would be markedly different from the rest. If it doesn’t have individual cell group voltage monitoring, it can’t warn about the individual voltages either.

6 hours ago, supercurio said:

IMO think the worst part is the lack of effort in implementing any kind of user feedback mechanism, which would help to make the system more tolerant to faults by informing the user of the pack's cells and BMS health.

I agree.

 

6 hours ago, sevin7 said:

I'm not sure exactly which 18650 cell Gotway wheels your referring to

GW mostly used the Pana/Sanyo 18650GA.

 

6 hours ago, sevin7 said:

All of the other wheels only beep based on speed and battery level

The V11 does have a wattage (among others) based tilt-back and warning beep. How the limit is calculated has varied a bit per firmware version, but it does attempt to behave a bit like the KS 88% warning. 

6 hours ago, sevin7 said:

in order for KingSong to understand exactly how much power the wheel can put out at any given time, they had to test the battery cells extensively to see what they could put out at any given charge level.

I’m not sure they did, seeing how blatant oversights we’ve seen from them as well along the years.

 Going by the spec sheet alone is my best guess. Even that would put them way above GW though… But that could also explain the early beeps, if they warn already when the continuous discharge level is close.

 

6 hours ago, sevin7 said:

the V11 has serious overheating issues and appears to have no built in safety measures to stop it from cooking its self

Has your V11 forced you to stop because of overheating, or are you only comparing temp values with other wheels? If the latter, are you aware what the designed temperature ranges for the V11 are?

 

55 minutes ago, Patrick Robert said:

So, each cell/parallel pack of LG M50T can only deliver 7.3A, thus in a 4p configuration it means 29.2A max. Is that it?

No, that’s not it. 7.3A continuous. How far the continuous value can be exceeded and for how long, I don’t know. I should check the spec sheet though.

55 minutes ago, Patrick Robert said:

But what about riding in cold weather, if the batteries get below +10C, they could only deliver 2.425A max? So not even 10A for a 4p???

No. It’s not like the battery behaves any different at +10•C and +9.99•C, that is just a simplified and very imprecise method of describing a continuous curve. -20•C and +10•C are worlds apart in what the batteries can actually produce. My guess is that the 2.4A is for -20•C, going up to 14.5A at +10•C.

 And again, they are only the ratings for continuous discharge.

[YourAubsome]

5 hours ago, Patrick Robert said:

Now I understand why Veteran went with the Panasonic NCR18650GA for the Sherman, with its max discharge rate of 10A. In its 10p setup, it means 100A max? Wow. Interesting to be able to compare not just Wh, but also max amperage between wheels. 

The Sherman's power is not limited by its batteries, its limited by the controller and the motor. Only wheels with powerful motors and smaller battery packs (approximately 2,000 watt hours or less) are limited by their batteries (note: I'm ignoring old wheels that are not very powerful and have tiny battery packs). 

The 240 Panasonic GA 18650 cells in the Sherman have a combined continuous power output rating of roughly 8,640 watts. 

Veteran could have used LG M50T cells and been fine because 3,200 watt hours worth of LG M50T cells (about 176 cells) can safely handle about 4,600 watts of continuous power. 

Edited November 9, 2021 by sevin7

[YourAubsome]

3 hours ago, mrelwood said:

Quote

the V11 has serious overheating issues and appears to have no built in safety measures to stop it from cooking its self

Has your V11 forced you to stop because of overheating, or are you only comparing temp values with other wheels? If the latter, are you aware what the designed temperature ranges for the V11 are?

off topic, so don't worry about replying here, but see 

 

[Darren0128]

I believe one of my packs is on the verge of being unusable.  RS19-C30 (1st batch) with 2900 miles on it currently.  I noticed lately that when riding the battery voltages drop significantly after the about 40% discharge.  A single quick burst of speed can cause the pack to go from about 40% to 15% rather quickly setting off my warning alarms.  I have still been using it, but have been cautious since I have noticed this behaviour, not discharging below 40% and trying not to accelerate too quickly.  Wheel still charges normally to 100.8V and shows 100% charge after.

 

  What would be the steps required to get my packs upgraded/replaced?

Edited November 9, 2021 by Darren0128

[Jason McNeil]

What's really worrying about a couple of the cases that have been reported, is that there's no prior warnings/symptoms before it goes critical, leading to a chain reaction in the pack.

Besides the lack of safety mechanisms in either the board, BMS, or these LG M50LT cells, there seems two main factors at play: the accelerated aging/dendritic formation by operating outside the operating spec & pack manufacturing issues. Those in the latter group would explain instances of brand new Wheels catching on fire, as well as the battery container fire from earlier in the year.         

With the LiTech battery project, we had to work on premise that Begode were not going to accommodate the request to add CANBUS, or other BMS communication channel to the controller, the packs needed to be self-contained for providing independent alerting for elevated operating temperatures, cell failure, or other malfunction. 

Compared to the LG M50LT, the Samsung 50E offers a 25% performance margin (~7.5A vs 10A sustained), running cooler, without any nominal capacity loss; even on cost grounds, the two cell types are pretty comparable.

Manufacturers like King Song  & Inmotion are probably able to use the LG M50LT, because they have better current rate limiting in their firmware. Pushing beyond the limits of a particular cell's spec might be fine in a lab setting, or single use operation, but in a machine where the expected life-span is several years, microscopic cell damage is insidious & accumulative; it might be fine weeks, months, possibly even years later, the trouble is that no-one knows just when it will go critical.      

I asked our LiTech contact, Henry, to provide a video demonstrating the packs thermal performance under conditions that are well outside the normal operating envelope 60A sustained....    

1. Keep discharging with 60A current on 24S4P, battery can run about 10 minutes, then fuse blew and high temp. rised and triggered the buzzer,
   So the result is current from 30A-60A is safe on 24S4P pack, but more than 60A the BMS will be easily trigger the over temp protections and fuse could be blew away if more than 10 minutes drawing.
2. Current more than 102A, in a few seconds the fuses blew, that measn any current more than 100A in a few seconds our fuses could be below

 

 

Edited November 9, 2021 by Jason McNeil

[Patrick Robert]

6 hours ago, Chriull said:

No, these are the maximum specified _continous_ currents from their datasheets.

 

5 hours ago, mrelwood said:

No, that’s not it. 7.3A continuous. How far the continuous value can be exceeded and for how long, I don’t know. I should check the spec sheet though.

I understand that this is the *continuous* max discharge current, in the sense of a sustained draw from the batteries. The peak output might be higher.

However that's the only mention of a maximum discharge current in the datasheet for the LG, if I'm not mistaken.

* LG M50T datasheet: https://www.batteryspace.com/prod-specs/11514.pdf
* In comparison, the Panasonic NCR18650GA datasheet mentions discharge rates up to 10A: https://www.batteryspace.com/prod-specs/11259-NCR18650GA.pdf
* And the Samsung 50E (used in the Abrams) states at "3.9 Max. Discharge Current" values of 9.8A (continuous) and 14.7A (not continuous), so a bit more detailed: https://ecocell.com.au/mx-m/bat-21700/bat-21700-sam-50e-specs.pdf
 

What I'm trying to do is make sense of Adam's video, and how I can setup a current alarm in EUC World to protect against this. The best figure I see to support this is 7.275A per pack.

[Paul A]

Just glad to hear that eWheels is continuing.

 

[Chriull]

45 minutes ago, Patrick Robert said:

 and how I can setup a current alarm in EUC World to protect against this. 

I don't see any sane way to protect against this with an EUC World alarm, because

- begode wheels report no battery current but motor current which is something completely different.

- nothing bad is happening immedeately once one draws more than this max continous current.