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Begode 900Wh Battery Recall Options


Jason McNeil

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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 by FlyboyEUC
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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 by RetroThruster
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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 by Patrick Robert
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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?

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  • 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? %

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  • 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?

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  • 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 by Chriull
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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%.

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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 by sevin7
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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 

 

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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 by Darren0128
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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.

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