Is Wrongway right about V8S BMS?

[mrelwood]

 

2 hours ago, Funky said:

I can see it going down from 50W to ~2.5W. At those ~2.5W my wheel normally beeps 6 slow times - letting me know it has finished balancing the cells. So naturally i thought it was balancing the cells then..

I’m pretty sure that the 18XL just monitors the overall charge current and beeps when it gets low enough. There is no communication line like that between the BMS and the mainboard, so the mainboard (or the charger) don’t have the slightest clue of what’s going on with cell balance or balancing.

Edited February 1, 2023 by mrelwood

[Funky]

1 hour ago, mrelwood said:

 

I’m pretty sure that the 18XL just monitors the overall charge current and beeps when it gets low enough. There is no communication line like that between the BMS and the mainboard, so the mainboard (or the charger) don’t have the slightest clue of what’s going on with cell balance or balancing.

Yeah it's kinda funny. Charger was green 2 hrs ago. But wheel beeps ~2hrs later.

[Mono]

4 hours ago, Funky said:

Worst thing one can do is to charge to 80%..

There are many more worse things. Charging to 80% in 80% of the time is most likely much better (for battery life) than charging to 100% in 100% of the time. I have checked various sources and can't remember any piece of evidence that would call in question this insight.

 

5 hours ago, mrelwood said:

I get that you are angry, but that is just simply not true. My Inmotion had all cell groups closer to each other than my multimeter can measure (under 0.01V deviance) after 4000km. That is simply not possible without a well operating balancing function.

Same here, I never checked individual cell voltages, but all my InMotion batteries charge to (at least) 83.9V after thousands of km.

Maybe the battery of @v8nicehas a specific and somewhat uncommon problem or defect?

Edited February 1, 2023 by Mono

[mrelwood]

1 minute ago, Mono said:

Charging to 80% in 80% of the time is most likely much better (for battery life) than charging to 100% in 100% of the time. I have checked various sources and can't remember any piece of evidence that would call in question this insight.

Based on my experiences and what I’ve read on this forum and others, I don’t think you are correct in your assumption. There are very few other instances that use passive top balancing BMSs with large series packs, so guides from other sources don’t usually apply. Knowledge in EUC batteries is also unfortunately small for most YouTubers.

 Out of the issues on this forum that don’t charge to 100% anymore, majority of them have either only ever charged to 80%, or mostly charge to 80%.

I balance charged my 16S about every 10th charge while otherwise charging to 80-90%, and the first pack died at 4000km, second one at 8000km. I then balanced my MSX every time, and the pack was still in good health at 14000km when I sold it. My V11 is in good battery health at 7000km with the same charging habit.

 The balancing currents and the balancing voltage window on many EUCs are simply not large enough to keep the balance if only done so occasionally. And the battery packs are often not matched up well enough to begin with, or at all.

 

[Funky]

1 hour ago, Mono said:

There are many more worse things. Charging to 80% in 80% of the time is most likely much better (for battery life) than charging to 100% in 100% of the time. I have checked various sources and can't remember any piece of evidence that would call in question this insight.

If balancing happens at last ~5% of charge.(Random number.) You don't really balance the cells in those 80% of times.. Because you are charging them to 80% most of times. (If it was one big cell, not groups of small ones.. Then yes 80% is good for life of cell. But because EUC's packs are made of many small cells - that get balanced only near 100%.. You want to charge 100% as often as possible.) Because some cells get to 4.2v, but some may be at 4.1v - because of 80% charging. They get balanced only at those 20%, when you charge to 100%. Over time the difference will get bigger. And that's how pack dies.

That alone says everything you need to know. More and more the cells become unbalanced. Resulting in premature death of battery pack.

 

But if one charged to 100% every time. All cells are balanced. (I personally fear more of not balanced cells..) Than losing some capacity over time. As i don't care about range much.. I want healthy as possible battery pack, so i can keep it for 3-4 years without change. At that time i will be buying new EUC..

 

Edited February 1, 2023 by Funky

[v8nice]

Sorry but its not 4.18 max.

See my check list .

 

[Chriull]

7 hours ago, mrelwood said:

The V13 has active balancing, which has a tiny software in the BMS constantly monitoring the cell group voltages, and actively by itself balances them out whenever the voltage is above 3.5V or something like that.

Active balancing means that charge from any cell with more charge is used to charge the lower charge cells.

No EUC uses this by now.

Passive balancing in contrary means that "just some bleeding resistor" is used.

Cell voltage monitoring is no criterion to distinguish between active and passive balancing.

 

[mrelwood]

1 hour ago, Chriull said:

Active balancing means that charge from any cell with more charge is used to charge the lower charge cells.

No EUC uses this by now.

Passive balancing in contrary means that "just some bleeding resistor" is used.

Cell voltage monitoring is no criterion to distinguish between active and passive balancing.

 

I don’t know if the V13 will charge up the low cells, or if it will just bleed out the high ones. I thought that active means that there is a piece of software logic controlling the balancing, versus only fixed resistors like we have in top balancing. But it is definitely different from top balancing, and a very welcome addition.

[Chriull]

8 hours ago, mrelwood said:

I thought that active means that there is a piece of software logic controlling the balancing, versus only fixed resistors like we have in top balancing.

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.

Others have more sophisticated ic's where different thresholds can be changed and monitored cell voltages can be read/reported to a supervising μC. Afaik ninebot always used such bms with integrated circuits controlling the balancing. With the S1 (or the Z series?) they started to have μC's with own firmware on the BMS.

8 hours ago, mrelwood said:

But it is definitely different from top balancing, and a very welcome addition.

It's the same logic/"algorithm" - just using different thresholds and controlled/supervised by an μC.

Like used now by KS for the S22.

The only thing we know by now is that this passive top balancing for the V13 is active during charging, starts already at lower voltages (not "just at the very top") and "finishes" to some 4.185V per cell.

Some settable charge end voltage like the S22 is afaik not implemented (by now).

I put the report from @SquallLHeartinto an own topic 

so it's not burried in the v13 megatopic.

[Chriull]

On 1/27/2023 at 5:06 PM, v8nice said:

I removed a v8f battery. Since I got it (2000 miles) it showed between 83.5 and 83.7v after long recharges. Recently it had dropped between 82.8 and 83.3v.  post a photo. as you can see I had 5 cells around 4.2v and all the rest around 4.15v.

This could either occur by a bit too low charger voltage, so that imbalances cannot be balanced as the cells cannot be charged high enough - this was excluded by you as you measured high enough charger output voltage.

Second possibility is that these 5 cells degraded and have lower capacity (or by some temperature difference, bms malfunctioning/fault, too deep discharge, whatever else got discharged some more than 0.05V more than the other cells).

While charging with classic passive top balancing at 4.2V the resistors are activated for the corresponding cells to slow their charging a bit.

Once a cell reaches some 4.25V the BMS cuts off charging completely to not overcharge this (likely already a bit degraded) cell.

Every cell still above 4.2V gets discharged by these resistors downto some 4.2V again.

On 1/27/2023 at 5:06 PM, v8nice said:

I discharged the 5 cells to 4.15v, reassembled the battery, drove a little and let it recharge for a long time. Now it goes up to  83.9v.  Much better but not perfect. I don't really understand why it doesn't exceed 84v when I balanced everything and the bms seems to be blocking the cell charge around 4.2v or even a little more.

83.9V versus a bit above 84V is a very miniscule difference! Battery charging to less than the charger no load output voltage is normal. There are losses in the charge input protection cirtuitry (against short circuit and reverse polarity) and the charger provides still a bit less voltage under the slight load at the end of charge.

If charging voltage is above 4.2V per cell and cells are nicely balanced each cell will get charged above 4.2V. But after charge discharged again to 4.2V. So immediately after charging they could have had some voltage above 84V.

Voltages after your short ride, immedeately after charging and some time after charging would be interesting.

On 1/27/2023 at 5:06 PM, v8nice said:

I also opened a v8 battery with  in autonomy problem (only 6 miles before the pedals which lift). 5500miles.  This one had a cell at 3.66v, one at 4v and the other around 4.15v I rebalanced and I am testing it, but it is obvious that there is no active or passive balancing.

Some ~0.4V difference is out of scope for balancing.

Especially such batteries with low parallel count get heavily burdened and can degrade their cells unevenly. In these series configurations the weakest cell gets beaten hardest.

If such battery packs are ridden downto low percentages such weaker cells can likely be discharged to dangerously low voltages degrading them even further.

It would be interesting to have the voltages from your 5x4.2V 15x4.15V pack once the battery is empty/at low charge!

19 hours ago, v8nice said:

Tb1....Tb19 ,these cables are only used to check the charge of each cell and cut the use of the wheel when a cell is too low voltage or too high voltage. Also the charge stops completely when a cell reaches approximately 4.2v.

No balancing on this shit bms.

What you reported until now does not justify this conclusionb- that could all be explained by normal top balancing functionality. And if course faulty bms...

Although i have seen no reports that would prove to opposite.

[v8nice]

I buy this day inmotion v5f with problem of range km.When i have the time i open the battery and tell you.I think is just balancing.

[v8nice]

look at the charging behavior of this v5f.

 

it charges very quickly, it goes up very high voltage (more than 84.5v) and as soon as the charger light turns green it goes down immediately.

 

What do you think?

[v8nice]

It stabilize around 82v .

I need.to open this shit...

[Chriull]

1 hour ago, v8nice said:

look at the charging behavior of this v5f.

 

it charges very quickly, it goes up very high voltage (more than 84.5v) and as soon as the charger light turns green it goes down immediately.

 

What do you think?

Degraded cells can have increased internal resistance. So their voltage can rise quite immedeately without taking real charge. So the bms cuts off once the voltage reaches about 4.25V of these cells.

With cut off (led turns green) the voltage goes down fast. Once the resistors are still discharging and no charge current is flowing anymore, which would keep the voltage up.

Could be a reason. If so the battery or some cells should be replaced.

Edited February 2, 2023 by Chriull

[alcatraz]

I wasn't aware the V5F had bluetooth active during charging. The V8 didn't. 

[alcatraz]

A quick drop in voltage could be a normal sign of aging. Resistance has built up. To fully charge it needs lower amperage and more time.

Similar thing happens with fast charging. 

[alcatraz]

If the cells are balanced it's still safe to ride, but know you're heating up the cells more, and will experience a lot more sag. So ride more carefully, especially if you try to ride outside the cell "comfort zone" meaning cold/hot weather, climbing/emergency braking, heavy rider etc.

[alcatraz]

My v8 BMS was faulty so it's kind of a waste to invest much effort into it. If your V5 bms is ok, it's a nice little project to swap out the cells. The wheel should feel like a different wheel. Swap out fkr 21700 cells perhaps and get a nice range boost.

I recommend Panasonic/Sanyo cells over LG/Samsung simply because they degrade slower. (at least in older tests)

[rcgldr]

I get the same effect doing a 3 amp charge on my V8F. Most of the time I charge to 76 volts, the storage voltage. During a 3 amp charge, EUC World reported voltage is 1.1 volts higher than what I see right after I stop charging, so I charge to a reported 78.0 volts, which is 76.9 volts just after I stop charging. The voltage decreases over time, and by the next day, it seems to hold at just a bit over 76 volts. I bought my V8F back in August 2021, and have a bit over 1000 miles on it now.

I also track voltage sag (minimum voltage versus displayed voltage) versus reported peak current. Based on battery tests for the MJ1 battery, at 10 amps per cell (20 amps for the pack) voltage drop should be 8.4 volts, but the actual voltage drop is more like 5 volts, so the reported peak current and reported peak power are higher than what the actual battery current is. My longest and fastest ride on my V8F was 8.4 miles for a bit over 33 minutes, 15 mph average speed (most of the time speed around 17 mph), so range hasn't been an issue yet.

https://lygte-info.dk/review/batteries2012/LG 18650 MJ1 3500mAh (Green) UK.html

 

Edited February 3, 2023 by rcgldr

[alcatraz]

I think that the cells heat up more when you do that. When they cool to room temp the voltage settles lower.

Similarly to how healthy cells drop in voltage in winter etc.

[v8nice]

Nous 

6 hours ago, alcatraz said:

I wasn't aware the V5F had bluetooth active during charging. The V8 didn't. 

The v8 have bluetooth active during charging .

 

6 hours ago, alcatraz said:

A quick drop in voltage could be a normal sign of aging. Resistance has built up. To fully charge it needs lower amperage and more time.

Similar thing happens with fast charging. 

But i charge with original charger v5f .

I have checked it at 84.5v .

[alcatraz]

23 hours ago, v8nice said:

Nous 

The v8 have bluetooth active during charging .

 

But i charge with original charger v5f .

I have checked it at 84.5v .

Oh, really? My v8 shuts off when charging. I don't remember being able to connect, but it would be great. I'll check.

Yeah, original or not. I mean when the cells become a little warm (because of resistance) the voltage settles lower after charging.

New cells and fast charging ~ old cells and slow charging. 

To completely charge you need very slow charging. Maybe even slower than the original charger. Or, you just leave it on the charger a while after it shows 100%. It's still charging but slowly.

The resistance is literal resistance. It means that an 82v pack is "resisting" to take a charge even with the charger at 84.5v. So it's trying not to charge. But after a long time it still charges. The key word is just "slow".

Edited February 4, 2023 by alcatraz

[Mono]

On 2/1/2023 at 10:23 PM, Funky said:

You want to charge 100% as often as possible.)

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.

On 2/1/2023 at 10:23 PM, Funky said:

Because some cells get to 4.2v, but some may be at 4.1v - because of 80% charging. They get balanced only at those 20%, when you charge to 100%. Over time the difference will get bigger. And that's how pack dies.

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.

[Mono]

On 2/1/2023 at 9:27 PM, mrelwood said:

I balance charged my 16S about every 10th charge while otherwise charging to 80-90%, and the first pack died at 4000km, second one at 8000km.

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.

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

[alcatraz]

I've got a V8 battery that did over 10k. Still perfectly balanced. 

Then I bought a second V8 and that battery was bad after only 4000km. I ended up attaching balance leads and went from 40 cells to 60 cells.