Is Wrongway right about V8S BMS?

[Mono]

On 2/2/2023 at 10:17 AM, Chriull said:

Passive top balancing has a similar logic controlling the balancing, not just fixed resistors.

Typical aliexpress passive balancing bms have the logic in hardware which means voltage thresholds are fix.

I am curious, what is the reason to not set the fixed threshold to 3.7V instead of 4.15V?

[Funky]

5 hours ago, Mono said:

Do you have a reputable source for this claim? It neither matches with what I have read or heard elsewhere (and I try hard to select sources by competence) nor with my personal experience.

Sure, most (all?) EUC packs only balance far above 80% charge state. The trade off is between fewer balancing cycles versus more cycles up to 100% charge state and sitting (much) longer at 100%. All these are (to some extent) bad for battery cells. To decide which is worse requires, AFAICS, a reasonable amount of empirical data.

No source just logical thinking. - Balancing happen at full charge - you charge it full. Duh..

 

Yes keeping battery pack at 100% for long time is bad - we all know that.. (3 months in winter storage - keep it around 50%.) You do understand 1 cycles is 1 cycles. Doesn't matter if you charge 80% every day. Or 100%

Yeah fewer balancing cycles.. Isn't that kinda bad also? I get that pack is healthiest/strongest as the weakest cell in the pack. Charging to full every time you would "overburden" the weakest cell. But same thing can happen, if you balance it fewer timer.. As that "weak" cell gets lower voltage and so on.

Luckily - you can't overcharge the "weak" cell.. But you can undervolt it. (Wheel "bleeds" the top charged cells - that got first to 4.2v, if i got that right. So the most empty ones charge fully to 4.2v)

But doing "fewer" balacings to 100%. You are kinda hurting the weakest cell. By making it more empty - no? You get what i mean?

 

 

Edited February 6, 2023 by Funky

[Paradox]

5 hours ago, Mono said:

Do you have a reputable source for this claim? It neither matches with what I have read or heard elsewhere (and I try hard to select sources by competence) nor with my personal experience.

 

[Chriull]

2 hours ago, Mono said:

I am curious, what is the reason to not set the fixed threshold to 3.7V instead of 4.15V?

If the charger provides fixed 4.2V per cell I see no real use to start bleeding already at 3.7V. that's still in the constant current phase and of low impact. Starting bleeding at 4.2V and then discharging to 4.2V again gives normaly enough balancing. If not, such different cells are likely not to be  "passive top balanced" anymore.

Otherwise, like the S22 has a selectable charge stop below 4.2V, after charging the cells could be "passive top balanced" by bleeding all cells to the voltage of the lowest one. So balanced 80% charging would be possible.

[mrelwood]

21 hours ago, Mono said:

Good to know. I did/do the same with three InMotions batteries from the V8 series and they seem all perfectly fine after 5000, 6000 and 8000km, respectively.

And I’m sure that there are 16S units that have more than 4k or even 8k km on their batteries as well. This was only my single experience. Perhaps the balancing currents on the 16S are on the low side of things, don’t know.

21 hours ago, Mono said:

Isn't the 16S sometimes bleeding down the battery even when off?

I haven’t noticed for it to do so.

[v8nice]

3 minutes ago, mrelwood said:

Et je suis sûr qu'il existe des unités 16S qui ont également plus de 4 000 ou même 8 000 km sur leurs batteries. Ce n'était que ma seule expérience. Peut-être que les courants d'équilibrage sur le 16S sont plutôt bas, je ne sais pas.

Je n'ai pas remarqué qu'il le fasse.

On 18l xl ,s18 ,16x when the wheel bip after long time charging after green light charger,the wheel is not completly off,and eat battery.For really off the wheel ,we need to ON and OFF the wheel .

On 16s i dont know if it same problem.

[v8nice]

I have open my v5f.

First i have check the real voltage battery.I see it have difference of 1v with the motherboard informations on apps 

The app see 1v more the real voltage.

I have open battery and write voltage of each cell ,on a paper.

Is not big unbalancing ,but it s not good.

I have make down each cell around 4.04v .

After i have charging the battery with original charger.it go at 85v ,green light and after it up voltage slowly around 85.1v ,and it rest a this voltage.

Before this work, the charging go at 84.56v and after it down around 81.8v ....

I have win 3v !

I confirm another time ,the inmotion bms of v5 ,v8,v10 not balancing !it shit bms.

 

[alcatraz]

The goods news is that your pack isn't dead. Balancing doesn't work though.

4.035v to 4.127v is a pretty big difference. 

Yeah your wheel's voltage meter isn't accurate but that's not a big problem. 

I would manually balance the pack to 4.20v and then remember the resulting voltage readout in euc world. Then you know what to aim for, or what 100% ACTUALLY is. 

[v8nice]

7 hours ago, alcatraz said:

La bonne nouvelle, c'est que votre meute n'est pas morte. L'équilibrage ne fonctionne pas cependant.

 

 It s not possible to balancing beceause it dont have balancing circuit in inmotion Bms.

 

I open 3 battery inmotion in 3 week always the cell is unbalancing.

[alcatraz]

8 hours ago, v8nice said:

 It s not possible to balancing beceause it dont have balancing circuit in inmotion Bms.

 

I open 3 battery inmotion in 3 week always the cell is unbalancing.

"manual" balancing means you do it yourself with a single cell charger or external balancer. 

The cells don't go out of balance super fast. You can manually balance every couple of months or maybe once a year if you'rr lucky.

Attach balance leads if you want to simplify. If you attach five 4s balance leads you can use a super cheap 4s balance charger and move it over the five cables every 1-2 hours. Then everything is perfectly balanced, and you can ride the wheel until it's time to do it again. 

[rcgldr]

43 minutes ago, alcatraz said:

Attach balance leads

V8F | V8S battery pack already has the leads (21 wires, pads labeled B-, B1 to B19, B+). However, each pair of cells supposedly has a voltage limiter circuit, which will limit the voltage per cell pair, but at least you can get them all even.

Edited February 8, 2023 by rcgldr

[alcatraz]

37 minutes ago, rcgldr said:

V8F | V8S battery pack already has the leads (21 wires, pads labeled B-, B1 to B19, B+). However, each pair of cells supposedly has a voltage limiter circuit, which will limit the voltage per cell pair, but at least you can get them all even.

Yeah? Do you have a picture of those leads? I can't see them in OP's pictures. 

He would need a way to connect a balancer onto those leads.

To the OP. A balancer like this, perhaps.

[v8nice]

I have check the v5f ,all seem ok but when i up in hill after 10/20sec ,the battery screen become red and the wheel say battery low and i need to stop...I think the cell is old and shit ...the drop voltage is too high...

And i drive very slowly for the check.

2 years ago i have another v5f and no problem with the same hill   .I need to upgrade this cell,or just replace the bms of v8 batterie with bms of v5f .

Edited February 8, 2023 by v8nice

[alcatraz]

Only you can determine if the cells are too degraded. Any older wheel will lose power. Be it 10% or 20% depending on the resistance in the cells. That's normal and acceptable to me.

If your loss is much higher then I find it odd that the cells are still relatively in balance. Is it possible the pack already got worked on? Are they the original cells?

Then there's the issue of outgrowing a wheel. If you want to use a wheel long term then it would be good if there was a bit of power headroom. I ride an older Tesla v1. I only ride it up to maybe 35km/h. The pack degrading doesn't really influence me. I know all the cells are perfectly balanced because I check every year. I open up the heatshrink and measure. On my MSX I already attached balance leads. It's also perfect. (I noticed that Panasonic cells fail less than LG/Samsung, at least back in the days of 18650)

Another reason to have a power headroom is to be able to ride in all seasons. It stresses the packs a lot more to ride in sub zero temperatures, with lots of extra sag, and reduced mileage. If your pack only did 4000km and feels weak it could perhaps have been only winter ridden.

Edited February 9, 2023 by alcatraz

[v8nice]

I agree with you about the extra power, but for that I already have bigger wheels. My first wheel was a new v5f in 2019, I drove it 1000 km and sold for a v8 because the autonomy was a bit low and the speed a little light. But I live at the top of a hill. I remember well that I had no particular problem going up. This v5f comes from a 55 kg girl who was riding quietly. I live in the south of France, here in the coldest winter it is 8/10° celsus, and most of the year it is rather 20°. The wheel is 6 years old now. The 4000km represents in my opinion between 150 and 180 cycles. wheel seems normal in autonomy on flat, I think so 10 to 20% have been lost, but it rolls well and I have all the safety alerts. On big hills it stops between 50 and 200metres at 12% elevation depending on the battery level. age really badly and have lost in discharge current...I have also noticed that the voltage display in third-party applications (euc world and wheelog) only updates every 30sec, as well as the display of the battery on the wheel, which can therefore go from 4 bars to 1 flashing red bar all of a sudden when climbing a hill. And it is impossible to see live how the voltage drops. I tried yesterday to bring the battery voltage down very low while driving several km in the garage (it was windy outside) I still had a current peak of 35 Amps, the wheel gave the impression of diving forward for a brief moment... But in these conditions with not long sides I was able to play hard enough without the wheel forcing me to go down. In fact I need it to climb a little better because I live on top of a hill. After I took this wheel to learn a little freestyle, so good ... it's just to know if it has a real problem or not ... Last night I recharged the battery from 32% to 100% seeing green in 2h10, but I have the impression that from 84 to 85v (the voltage displayed in the application is +1v higher than the real one) this put 1 hour! Results balance ok I disconnected the charger at 85.08v. Unfortunately I cannot do a range test while driving quietly today there is still too much wind for a test.

[alcatraz]

Maybe you have a damaged capacitor on the control board. I say that because the battery pack seems pretty ok.

As you said you were able to get up the hill before on a same model wheel.

Even with my older V8 battery packs I have never seen 4 bars go to a blinking bar at once. That's the problem really.

[alcatraz]

(A bad capacitor causes pedal dipping and tons of voltage sag.)

[v8nice]

2 hours ago, alcatraz said:

(Un mauvais condensateur provoque une chute de la pédale et des tonnes d'affaissement de tension.)

Thanks, that's a good point to check! But it seems to me that the wheel would turn off sooner? I also have an external 84v 20s1p battery, I could connect the 2 sets and test to climb the hill. If the problem is the same it will confirm a dead capacitor!

v8 with this external battery is very cool.Now i have 18xl and v8f ,and the small v5f for initiating freestyle.

Edited February 9, 2023 by v8nice

[Mono]

On 2/6/2023 at 5:21 PM, Funky said:

You do understand 1 cycles is 1 cycles. Doesn't matter if you charge 80% every day. Or 100%

It does, actually, even pretty big time. IIRC, it's about like cycling 1000 times 0-100% gives about the same battery depletion as cycling 6000 times 25-75% (which "are" 3000 full cycles instead of 1000). Additionally, the part from 75 to 100% produces more depletion than the part from 0 to 25% (which we anyway never use). That's indeed another reason to cycle to 100% as scarcely as possible.

Edited February 9, 2023 by Mono

[Funky]

1 hour ago, Mono said:

It does, actually, even pretty big time. IIRC, it's about like cycling 1000 times 0-100% gives about the same battery depletion as cycling 6000 times 25-75% (which "are" 3000 full cycles instead of 1000). Additionally, the part from 75 to 100% produces more depletion than the part from 0 to 25% (which we anyway never use). That's indeed another reason to cycle to 100% as scarcely as possible.

I meant.

If you understand it doesn't matter from what %%% you charge be 25% to 50% - That's 25% charge... Do it 4 more times and that's 1 cycle.  25%x4 = 100%. Same thing if you charge one day 35% next day 20% and then 45% = again 100%. 

(1 cycle is when you have done 100% together - no matter from how empty/full battery you have started to charge.)

Example: You like to charge to 80% often - right. Let's say you charge your wheel when it drops down to 45%.

From 45% to 80% that's 35%.. Do the same for 3 charges and it will be 105%. Now you have done 1-100% = 1 cycle and 5% already in next cycle.

 

Also you are wasting 20% of battery capacity. I personally don't need the range. But i still charge to 100%. When ever my battery drops down ~50%. Once or twice a week.

 

Yes i know one cell and only ONE is good if you charge it to 80%. But we are talking about PACK. -You need to throw that 80% knowledge in trash. When we are talking about EUC's.  Everyone is charging their EUC to 100%.. (Everyone can choose how they charge. If you like to do it till 80% do it. It's your wheel..) Who cares about cycle number anyways? You can do even 5000 cycles. Your battery pack doesn't suddenly die at 1000x cycles.  You only lose some capacity over time.

 

All i know - balancing is important. If everyone is charging to 100% - more users would had problems already.. Most cases with problems are from people who don't balance the packs enough.

 

Edited February 9, 2023 by Funky

[Mono]

Edited February 9, 2023 by Mono

[Robse]

Whatever is best for the battery means absolutely nothing to me. What matters is how far and how long I can ride safely.  Safe for me is anything over 35% charge. Whether I can charge 1000 times or 2000 times (cycles in total) is completely irrelevant. For example; My KS 16X has done 4000 Km in a year - as I typically ride 50 - 70 Km on a trip, and I always charge to 100% when I get home, this means that I have probably charged approx. 85 times last year.....  85 times I have mounted the charger and let it reach 100% and balance.   These 85 times do not even = complete cycles,  as the wheel is typically at 40%.   But regardless of this, my batteries have an expected lifetime of much more than 1000 cycles. All other things being equal, this means that I have to ride 4000 km a year and charge 100 times a year for 10 years to reach maybe 700 complete cycles. I won't have that wheel in 10 years. Probably not even in 5 years. The Chinese shit simply does not last that long.  I go for 100% charge each time, everything else is complete nonsense, especially because it is one of the most important things for the safety to have enough voltage on the battery.

[Mono]

14 hours ago, Funky said:

But i still charge to 100%. When ever my battery drops down ~50%. Once or twice a week.

This means you actually do not balance your cells as often as possible (after each usage) and that's the right thing to do to preserve your batteries.

[Funky]

39 minutes ago, Mono said:

This means you actually do not balance your cells as often as possible (after each usage) and that's the right thing to do to preserve your batteries.

Yeah - i don't go for a ride and charge it every time.

Let's say i use daily 10%. And each time i don't charge to 100%... That would be just stupid.... Because wheel would sit at 100% most of the time. (Which is also bad.) I only charge when my battery drops around 50%. Normally every 3rd/5th day of usage.

 

I said - i charge to 100% every time i connect the charger to the wheel.   (Each time the charger is connected to wheel, i charge to 100% +2hrs of balancing.)

Edited February 10, 2023 by Funky

[v8nice]

I charge at 100% and for a long time each time, my new v8f arrived with a maximum charge of 83.7v, after 2 years it was 82.8v. I opened 3 batteries and shared them here, there were always look at the number of complaints about inmotion v5,v8,v10 about low battery, battery not charging enough, you don't want to admit that there is no balance in these wheels.