Leaperkim Lynx 2700wh: 151V, 20" tire, suspension, 89lb

[techyiam]

Although, it is overcharging a little bit, it should drain back to 4.2 V or below quite quickly, if the BMS is working properly. There is a min / max difference of cell voltages of about 20 mV. Some cells will be above and some cell will be below the 4.2 V threshold.

On my S22, if some cells don't go above 4.2 V in the battery pack, not much cell balancing would be done. With the BMS on my S22, the over voltage condition doesn't last long.

Also with the latest firmware V 2.35, there is an error message if any cell group goes above 4.22 V. 

 

[RagingGrandpa]

3 hours ago, Cobaltsaber said:

wrongway's Lynx
I think I much prefer the v13 and begode wheels only charging up to 4.18v just for a bit of leeway.
Whats you guy's thoughts on this?

Charging to 4.18V vs 4.22V makes nearly no difference, in terms of cell health. It's splitting hairs.

The small benefit of exceeding 4.20 is ensuring that top-balancing circuits are triggered during every charging cycle. The pack will be more perfectly balanced. Which still doesn't matter much, compared to allowing an extra 17mV of imbalance (which won't hurt). 

I bet it's natural variation of the charger setpoint. Some are calibrated tightly to 151.2V. Others are off a little. This one seems to be 151.8. If you really care about it, open the charger and adjust it. But there should be no difference in cell life.
 

2 hours ago, The Brahan Seer said:

how accurate can the motherboard actually measure

These voltages are measured inside the BMS at the single-cell level. Accuracy for such IC's is rated +/-25mV, with typical values much closer than that.

But yes, "17mV overcharged" is within the margin of error.
 

24 minutes ago, techyiam said:

it should drain back to 4.2 V or below quite quickly, if the BMS is working properly

Agreed.
 

3 hours ago, Cobaltsaber said:

"no wonder veteran boards blow under hard braking at full charge"

It's a relevant point, given the history... because we've observed BMS that shutoff the pack output if any cell exceeds 4.25V, so if you begin closer to that limit, then brake hard, it's more likely that you can reach the magic number 4.25V and trigger it.

But this +17mV from a charger set a little high... should be gone in the first 30 seconds of riding. 
 

1 hour ago, Rawnei said:

they already changed it in factory long time ago now

Oh cool, news to me! 

Is there more information about what they changed, and when? 

Thx

Edited December 15, 2023 by RagingGrandpa

[Rawnei]

13 minutes ago, RagingGrandpa said:

Oh cool, news to me! 

 

Is there more information about what they changed, and when? 

Thx

They removed the over current protection on the BMS (keeping it only on the motherboard) from batches produced in early August and forward:

 

[RagingGrandpa]

On 8/17/2023 at 8:01 PM, travsformation said:

You can download the full report here 

Ah.
Lost in translation... it has nothing to do with overcurrent. It's the 4.25V/cell overvoltage protection. 
LK modified the BMS to remove the pack shutoff behavior for cell over-voltage. 
The PCB rework looks dubious, slicing into a trace to make a new pad... hopefully newer batches will get new PCB's. 

They must have delegated the charging shutoff for overvoltage to the main controller then... because LK BMS has communication with the main controller (unlike classic Gotway). Ok.

[zaft]

With these smart bms per cell voltage regulation, it’d be handy to have a 70% balance option for longer storage etc 

Edited December 16, 2023 by zaft

[Rollin-on-1]

1 hour ago, zaft said:

With these smart bms per cell voltage regulation, it’d be handy to have a 70% balance option for longer storage etc 

I would like to see a balance-on-demand that can be initiated by an app or from the wheel's display at any state of charge.  

[Uras]

9 hours ago, zaft said:

smart bms per cell voltage regulation

does it really regulate voltage per cell or does it just show you how each cell is going? Smart bms isn't active bms - maybe there is some confusion here? I'm guessing it still charges with passive bms? Yeah, from the LK blurb: "a Smart BMS that diligently reports the health of individual battery cells. This includes details such as cell voltage variance/drift, monitored by half-a-dozen independent temperature probes strategically placed across various cells and components on the BMS."

Edited December 17, 2023 by Uras

[RagingGrandpa]

10 hours ago, Uras said:

does it really regulate voltage per cell

Probably not, because the typical method we've seen in EUC's is using standalone cell management IC's to engage and disengage bleed resistors at a fixed voltage threshold. 

(I think there is no published teardown showing the Lynx BMS PCB yet?)
 

10 hours ago, Uras said:

does it just show you how each cell is

I think yes.
 

18 hours ago, Rollin-on-1 said:

I would like to see a balance-on-demand

Resistive balancing without control of the charger's CV setpoint, or without a charger connected at all, is rather tricky... that's a big ask. 
 

Edited December 17, 2023 by RagingGrandpa

[Rollin-on-1]

37 minutes ago, RagingGrandpa said:

Resistive balancing without control of the charger's CV setpoint, or without a charger connected at all, is rather tricky... that's a big ask. 
 

Fair enough...I'd still like it

[Funkymonk7]

So what does everyone think about the difference between the Kenda knobby tire and the Longxin tubeless street tire? I have no reference points whatsoever. Please help me decide. I will be doing mainly street riding but would like to do some offroad adventuring eventually. 

[Rawnei]

1 hour ago, Funkymonk7 said:

So what does everyone think about the difference between the Kenda knobby tire and the Longxin tubeless street tire? I have no reference points whatsoever. Please help me decide. I will be doing mainly street riding but would like to do some offroad adventuring eventually. 

Depending on what you are used to from before can take a while to get used to a new tire but I like the Kenda 262, specially on a wider rim, feels very good on the Sherman S.

[wstuart]

19 hours ago, Rollin-on-1 said:

Fair enough...I'd still like it

Balance charging can be done, but I think it would require a connection between each cell group and the charger.  With RC car and flight Lipo packs we do this with a balance plug that is a collection of wires (one wire from each cell).  

I've seen this done on an EUC.  I met a rider who modded his Sherman Max in a way that had balance plug coming out of the euc, allowing him to balance charge. 

[zaft]

3 hours ago, wstuart said:

Balance charging can be done, but I think it would require a connection between each cell group and the charger.  With RC car and flight Lipo packs we do this with a balance plug that is a collection of wires (one wire from each cell).  

I've seen this done on an EUC.  I met a rider who modded his Sherman Max in a way that had balance plug coming out of the euc, allowing him to balance charge. 

I assumed this was what was meant with 'smart bms' otherwise it's not 'smartly managing' anything really. I immediately thought of hobbyist RC charging of multi cell packs. I guess I should find a smart-bms thread on here because I now am wondering how each company/model smart bms implementation actually works and are likely not identical.

That's awesome about the sherman, great idea.

[RagingGrandpa]

7 minutes ago, zaft said:

I am wondering how each company/model smart bms implementation actually works

For all such EUC's thusfar, the term "smart BMS" means: "reporting individual cell voltages to a smartphone app." 
It's for diagnostic purposes. 
It doesn't substantially change the way the pack is charged or balanced.

Separate from this, many EUC's include 'smarter' functions in the BMS, such as temperature monitoring and fault communication with the main control board. Models like SherMax and V11 cannot tell you individual cell voltages, but they still can report if a pack is operating normally, or has a problem. 

The basic protections of over-voltage stop-charging, and over-current interruption, are present in every full-size (>1kWh) EUC today. 
Smaller EUC's may be a different story... I haven't seen detail for the MTen4 BMS to confirm it. MTen3 had no over-current protection, relying on the fault to melt open by itself :/  
 

3 hours ago, wstuart said:

rider who modded his Sherman Max in a way that had balance plug coming out of the euc

For 100V SherMax and two separate packs, it would mean at least 46 extra wires being mounted and exposed at a connector. 
That's 46 additional safety hazards, because these cell monitoring wires are capable of over-discharging cells and starting fires. 

Far safer to make the cell monitor circuits as small as possible, like we do with most EUC's today that solder a PCB directly to the weld strips, with no "wires" at all.

[Jason McNeil]

LK provided a pack of compliance testing reports on the Lynx this morning 

LK Lynx- CE Certification
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-CE-Certification.pdf
LK Lynx- IP X6 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-IP-X6-Test-Report.pdf
LK Lynx- Battery IEC 62133-2 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-Battery-IEC-62133-2-Test-Report.pdf
LK Lynx- FCC 15 RF Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-FCC-15-RF-Test-Report.pdf

 

[Duster]

44 minutes ago, Jason McNeil said:

LK provided a pack of compliance testing reports on the Lynx this morning 

LK Lynx- CE Certification
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-CE-Certification.pdf
LK Lynx- IP X6 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-IP-X6-Test-Report.pdf
LK Lynx- Battery IEC 62133-2 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-Battery-IEC-62133-2-Test-Report.pdf
LK Lynx- FCC 15 RF Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-FCC-15-RF-Test-Report.pdf

 

Gotta appreciate the money Leaperkim is putting into that. I've been somewhat okay with the "trust me bro" quality of their wheels up to this point, but this makes me feel like they are listening to riders' safety concerns. Nice to have another company doing this. Hopefully they'll develop a good reputation like Inmotion!

[Rawnei]

55 minutes ago, Jason McNeil said:

LK provided a pack of compliance testing reports on the Lynx this morning 

LK Lynx- CE Certification
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-CE-Certification.pdf
LK Lynx- IP X6 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-IP-X6-Test-Report.pdf
LK Lynx- Battery IEC 62133-2 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-Battery-IEC-62133-2-Test-Report.pdf
LK Lynx- FCC 15 RF Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-FCC-15-RF-Test-Report.pdf

 

Interesting, what conclusions can we draw from the IP X6 test?

[Robse]

59 minutes ago, Jason McNeil said:

LK provided a pack of compliance testing reports on the Lynx this morning 

LK Lynx- CE Certification
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-CE-Certification.pdf
LK Lynx- IP X6 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-IP-X6-Test-Report.pdf
LK Lynx- Battery IEC 62133-2 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-Battery-IEC-62133-2-Test-Report.pdf
LK Lynx- FCC 15 RF Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-FCC-15-RF-Test-Report.pdf

 

just for the record, the "ce certification" is nothing else than a standard document of conformity. Not to state anything bad about LK or the rest of the EUC manufacturers, but i do not believe that any of them has done a true testing of their products in order to obtain and evaluate results versus whats required to stay within all legal boundaries regarding emc emission.

[Robse]

20 minutes ago, Rawnei said:

Interesting, what conclusions can we draw from the IP X6 test?

Test personnel in urgent need of working glasses.

or

Bribe amount correct...

 

[Rawnei]

52 minutes ago, Robse said:

Test personnel in urgent need of working glasses.

or

Bribe amount correct...

 

Well to be fair, I don't think water will drip in from the solid plastic on top, it would come in from the seems or sip slowly into the display, my guess is it's from removing the cover, a bit sloppy.

[stizl]

Having managed some offshore contract manufacturing in China myself, there is certainly some seeminigly ubiquitous element of ‘greasing the wheels’ of certification throughout the industry there. This even occurs with UL certifications, which have very high traceability requirements compared to others. 

Still, in this case, I feel pretty good about the Lynx’s water resistance. Considering the intensity of the testing water jet (100L/min for 3min claimed), the drops of water in the screenshot above are pretty minimal. Also, I’m assuming the Lynx’s PCBs are coated with waterproof coating like the Patton’s are. 
 

[stizl]

Just now, Rawnei said:

my guess is it's from removing the cover, a bit sloppy.

I was thinking/hoping the same. 

[RagingGrandpa]

2 hours ago, Rawnei said:

what conclusions can we draw from the IP X6 test?

Don't spray your EUC with the garden hose! 

Their Lynx survived their 3-minute spray test. But the test did not show evidence of disassembling the battery packs to confirm no ingress.
The batteries are the most sensitive part of the EUC with regard to water safety, and we can't say anything about them from a brief test like this. 
 

Edited December 19, 2023 by RagingGrandpa

[Ronin Ryder]

1 hour ago, Rawnei said:

Well to be fair, I don't think water will drip in from the solid plastic on top, it would come in from the seems or sip slowly into the display, my guess is it's from removing the cover, a bit sloppy.

There's the top cover and inside there's another cover that protects the motherboard of the Lynx. I would be very surprised to see water ingress there. Noticed this during a tear down of the wheel.  Imo all the latest new wheels are good enough ish for rain riding. Ive ridden extensively the lynx in the rain and so did Hsiang. As always check your wheel after a rain ride and dry up the wheel asap. 

https://youtube.com/shorts/kKSzZtSc3go?si=UbeneF5DWjsodArw

Edited December 19, 2023 by Ronin Ryder

[RagingGrandpa]

3 hours ago, Jason McNeil said:

LK Lynx- Battery IEC 62133-2 Test Report
https://www.ewheels.com/wp-content/uploads/2023/12/LK-Lynx-Battery-IEC-62133-2-Test-Report.pdf

Impressive that the 50S cells can survive cell-top shorting! (Reached 119°C temperature but did not burst.) The cell-internal safety devices (CID+PTC) seem quite effective. 

The test also mentioned baking the pack at 130°C, which is the rated temperature of the separator film inside the cells. No fire, great! 

They teased us with an unreadable blurry schematic though 

Quote

At least we got some nice pictures of the BMS from it: 

Quote

Small gripe that there's no beeper...
While the controller is involved and can beep for overtemperature during recharging, a beeper in the pack itself is the only way to become alerted of a temperature rise during storage (e.g. resulting from corrosion damage discharge paths). 

Overall, seems nice.