Is Wrongway right about V8S BMS?

[v8nice]

I search pictures of v8s battery.Outside and inside.

I would like to use the bms v8 that I have with 40 samsung 40T or molicell p42A cells. I would like to see how they placed my cells to copy identically.

[rcgldr]

On 2/10/2023 at 7:32 AM, v8nice said:

I charge at 100% and for a long time each time, my new v8f arrived with a maximum charge of 83.7v

83.7 is similar to what the V13 (which does have cell balancing) limits charge to, 4.185 volts per cell. I got my V8F in August 2021, but only have a bit over 1000 miles on it now, and I see 83.6 volts. I'm not sure if I ever saw 83.7 volts when I first got it, mostly 83.6 showing, with intermittent display of 83.7 volts.

[rcgldr]

2 hours ago, v8nice said:

I would like to use the bms v8 that I have with 40 samsung 40T or molicell p42A cells. I would like to see how they placed my cells to copy identically.

Molicel has P45B cells now, only 7% more capacity, but less internal resistance for less voltage sag under load. 

[v8nice]

17 hours ago, rcgldr said:

Molicel has P45B cells now, only 7% more capacity, but less internal resistance for less voltage sag under load. 

I need less voltage sag!

it s the best solution for 20s2p battery!

But for me,3500mah (v8f battery i have actually) + 20% = 4200mah

Or with samsung 40T is 14% more capacity.

[v8nice]

17 hours ago, rcgldr said:

83.7 is similar to what the V13 (which does have cell balancing) limits charge to, 4.185 volts per cell. I got my V8F in August 2021, but only have a bit over 1000 miles on it now, and I see 83.6 volts. I'm not sure if I ever saw 83.7 volts when I first got it, mostly 83.6 showing, with intermittent display of 83.7 volts.

See the voltage i have check on the v8f battery :limit charge seems 4.20/4.21v ...

[rcgldr]

8 hours ago, v8nice said:

See the voltage i have check on the v8f battery :limit charge seems 4.20/4.21v ...

The 83.6 | 83.7 volts is the voltage reported to Inmotion App or EUC World. I don't know if this differs from the actual voltage.

[v8nice]

it s little balancing problem .

But with time the cell is more unballanced and you see the voltage down ...

mine v8f have 2 years .When i have buy reported voltage by application is 83.6/83.7 ,long time is around 83.5v (and i have check with multimeter and is the same) ,and in january sometimes the maximum voltage is around 82.8v .

with balanced manually now is around 83.8/83.9v .

I don t understand why is not 84 /84.4v but its more good .

[alcatraz]

14 hours ago, v8nice said:

See the voltage i have check on the v8f battery :limit charge seems 4.20/4.21v ...

These values look better than before.

[alcatraz]

Overcharge protection is a seperate feature from balancing. It's the reason you can't hit 84.0v. You should get close to 84v because your deviation is "only" 0.05v thereabout. 16x0.05 = 0.8v. 84-0.8v = 83.2v end voltage.

The slightly low cells are likely the healthy cells here. The ones that reach 4.20v+ first have lost capacity somehow. Check for corrosion?

Group 1,2,3,4 are the bad groups basically. It's interesting that they're all close together. That could indicate an external factor like moisture or some kind of contamination. 

Or, you charged those manually, and charge them too far.

What's interesting is to identify the cells that deviate over time. Don't focus on the majority.

Edited February 13, 2023 by alcatraz

[v8nice]

I have informations about new v8f,jist battery change with 21700 4000mah lishen cell max continus rate 12A .

It s good news!

 

For my v5f,now it s more good after 3 cycles i climb more of my hill.I think IR is not perfect with external température 5/10° celsus,but with more than 15° is ok and range test confirm good battery with more than 20km .

[rcgldr]

So if the V8F | V8S don't have passive cell balancing and at best, a voltage limiter that shuts off charging once any pair of cells reaches some max voltage, is there any point to charging 100%, even occasionally?

 

[Chriull]

6 hours ago, rcgldr said:

So if the V8F | V8S don't have passive cell balancing and at best, a voltage limiter that shuts off charging once any pair of cells reaches some max voltage, is there any point to charging 100%, even occasionally?

Until now i did not see any proof that there is no passive balancing.

Here were many reports of ks and begode/gw wheels with unbalanced cells as reported here for the v8 too.

The bms of the v8 with the unbalanced cells were not checked for malfunction/faults/defects.

Some reports of peoples chats with chinese inmotion engineers could be just lost in translation, too.

[rcgldr]

8 hours ago, Chriull said:

Some reports of peoples chats with chinese inmotion engineers could be just lost in translation, too.

I sent an email to service @ imscv.com (inmotion world), and they replied there was no passive balancing. It could still be a translation issue between their techs and China.

 

[Chriull]

42 minutes ago, rcgldr said:

I sent an email to service @ imscv.com (inmotion world), and they replied there was no passive balancing. It could still be a translation issue between their techs and China.

 

Or maybe there really isn't and bms with balancing are overrated?

There are not strikingly many reports of bad v8 battery packs compared to other models.

That's somehow confusing.

[mrelwood]

9 hours ago, rcgldr said:

I sent an email to service @ imscv.com (inmotion world), and they replied there was no passive balancing. It could still be a translation issue between their techs and China.

Did you describe what you meant by passive balancing?

I chatted with Cecily of Inmotion in Telegram. I described what I mean with cell balancing. She checked from the engineers, and replied that yes, there is a cell balancing function in their wheels.

[supercurio]

I don't think we'll get a good answer from Inmotion since they don't know themselves and said different things depending how you ask.

I talked about it with Adam and he asked again not long ago and they confirmed one more time that all wheels until the V13 had no cell balancing in the BMS.

Pretty sure it's up to us to figure it out, somehow.
Or maybe we can ask different people, that will task that to competent personal able to answer the question authoritatively using the circuit diagram.

[redfoxdude]

Agreed, I'm still getting the feeling that they think when we say passive, we mean passive even when not charging, as opposed to passive meaning top balancing with bleed resistors.

[rcgldr]

2 hours ago, mrelwood said:

Did you describe what you meant by passive balancing?

I chatted with Cecily of Inmotion in Telegram. I described what I mean with cell balancing. She checked from the engineers, and replied that yes, there is a cell balancing function in their wheels.

I first asked if there was passive cell balancing, got a reply that there wasn't. So rather than describe what I meant by passive cell balancing, I asked what the 21 wires are for, since they are setup to sense the individual voltage of each parallel cell pair, and haven't received a response back.

1 hour ago, redfoxdude said:

Agreed, I'm still getting the feeling that they think when we say passive, we mean passive even when not charging, as opposed to passive meaning top balancing with bleed resistors.

From another source, the statement was that all charging stopped once a parallel cell pair reached some voltage threshold, but this could be a translation issue and that charging is only stopped via a bleed resistor for the parallel cell pairs that have reached some voltage threshold, while the other cell pairs continue to charge until all cell pairs reach the voltage threshold, at which point all bleeding resistors are enabled. If this is the case, then based on my V8F reported max voltage of 83.6 volts when charging, each bleed resistor is enabled for any cell pair that reaches 4.18 volts. I see intermittent peaks of 83.7 volts, but it mostly shows 83.6 volts. The V13 is claimed to cap charge voltage to 4.185 volts per group of parallel cells, which on the V8F would be 83.7 volts.

Edited March 4, 2023 by rcgldr

[v8nice]

Depuis l'équilibrage manuel since the manual balancing that I performed on my v8/v8f batteries, the charging voltage reached 83.8/83.9v. As I showed in a photo, my charging stopped when a cell reached 4.22v on MY multimeter,  but that but says that it must be done to stop at 4.2v, there may be a small deviation in the inmotion card or in my multimeter. I do not know why you insist so much on saying that there is a balancing then  that the 3 inmotion batteries that I recently balanced are working correctly for the moment, I think that the imbalances must be created when the wheel is stored or little by little since the inmotion bms does not take care of it. For the moment since 15 charges on  the v8 battery the max charge voltage is 83.86v, the max voltage on the v5f battery is 84.07v. The v8f battery is not used at the moment because I am testing the v8 battery which had a big imbalance when I  I recovered it and it works very well now,  almost 9000km (30km) The v5f battery (6 years and 4000km) allows me to do 23km on the flat while driving at 20/25km/h with my weight of 80kg dressed, it is just a little weak on the hills and displays 1v more  on the application. These 2 batteries were less than 10km before intervention. It is a pity that we have to do it ourselves. Every 2 or 3 years seems good, especially important to monitor the total charge, the voltage of the charger. Also when  the cells are quite well balanced you can drive on the flat slowly until 0%, 1%, 2% of battery remaining. On my v8f the wheel prevented me from going up under 9%/8%, enough to do  km more at low speed.

[supercurio]

Great job with the manual balancing @v8nice and thanks for showing us what were the actual voltages measured.
As V10F owner I'm wondering how the pack is doing.

Since the BMS stops the charge when some cell groups are getting too high, there's are two methods that tells us that a pack needs balancing

1. Voltage when fully charged is lower than when it was new. But you might not remember.
2. Charge is interrupted earlier and that can be observed with a energy meter. Instead of stopping at drawing 6W from the wall, it would stop at 20W, 40W or more - before reaching 84V: a clear indicator!

[Chriull]

2 hours ago, v8nice said:

Also when  the cells are quite well balanced you can drive on the flat slowly until 0%, 1%, 2% of battery remaining. On my v8f the wheel prevented me from going up under 9%/8%, enough to do  km more at low speed.

With older battery packs with some degraded cell (groups) it's imho such an emptying of the batteries that could caus such "huge" imbalances which a top passive balancing bms cannot balance anymore.

These weakest cells have less coltage compared to the healthy ones - so going to some 0-9% could easily discharge them well below 2.5-3V.

2 hours ago, v8nice said:

4.22v on MY multimeter,  but that but says that it must be done to stop at 4.2v, there may be a small deviation in the inmotion card or in my multimeter.

0.02 is ~0.5% of 4.2V - very likely is your multimeters and inmotions measurement accuracy worse.

[mrelwood]

10 hours ago, v8nice said:

The v8f battery …  almost 9000km (30km)

The cells are at about 300 full charging cycles. They are expected to have about 70% of their original capacity left. 

10 hours ago, v8nice said:

The v5f battery (6 years and 4000km) allows me to do 23km

That would be nearing 200 cycles, but 6 years is a long time. So the cells are expected to be at 80% or less of their original capacity.

 Each cell doesn’t age at exactly the same time. Some of them may be at 68%, some at 72%. One of the parallel groups may have only 68-69% cells, another only 71-72%.

 That creates a large imbalance pretty fast. It’s well known that the balancing currents on EUCs are very small, and that they can’t salvage large imbalances. Even if the batteries were handled with good care, they are at an age where one of the 40 battery cells may age faster than expected. There’s a good chance to get one lemon in a full pack.

 We don’t even know whether the batteries have been balance charged properly for their lifetime to take full use of the balancing function. To me it sounds normal to have some batteries drift too far for the BMS balancing to work at that age.

 

My 16S battery failed at 4000km. That’s only around 100 full charge cycles. I balanced the pack religiously every week, from new. The 16S does have a cell balancing function, just like the rest of them. STILL, it wasn’t enough, despite my best efforts at the time.

A failing pack is not a proof of the existence nor the lack of the balancing function.

[v8nice]

My v5f charges at 85.07v since my manual balancing. Except the first time it went up to 85.14v. The charger was tested at 84.5v. I have a difference of 1v between the application and the real voltage Yesterday I saw 84.8  maximum v after a long charge. I opened the charger and only 84.2v came out. The adjustable knob inside was covered with glue.  I lowered the resistance by turning counterclockwise. The voltage is now 84.6v. I reconnected the wheel, I now have 85.2v at maximum charge. I don't understand why these inmotion chargers  goes wrong on its own. It's not the first time I've had this problem with inmotion chargers which change the maximum voltage on their own, without the internal screw moving... Also I notice that the battery charge is lower  at the maximum voltage of the charger, about 0.4v less...

[v8nice]

On 3/8/2023 at 12:24 AM, mrelwood said:

The cells are at about 300 full charging cycles. They are expected to have about 70% of their original capacity left. 

That would be nearing 200 cycles, but 6 years is a long time. So the cells are expected to be at 80% or less of their original capacity.

 Each cell doesn’t age at exactly the same time. Some of them may be at 68%, some at 72%. One of the parallel groups may have only 68-69% cells, another only 71-72%.

 That creates a large imbalance pretty fast. It’s well known that the balancing currents on EUCs are very small, and that they can’t salvage large imbalances. Even if the batteries were handled with good care, they are at an age where one of the 40 battery cells may age faster than expected. There’s a good chance to get one lemon in a full pack.

 We don’t even know whether the batteries have been balance charged properly for their lifetime to take full use of the balancing function. To me it sounds normal to have some batteries drift too far for the BMS balancing to work at that age.

 

My 16S battery failed at 4000km. That’s only around 100 full charge cycles. I balanced the pack religiously every week, from new. The 16S does have a cell balancing function, just like the rest of them. STILL, it wasn’t enough, despite my best efforts at the time.

A failing pack is not a proof of the existence nor the lack of the balancing function.

on my v8f buy new, I got maximum charge of 83.6v for 2 years and 3000km.  I have always left a long balancing time.  It was getting more like 83.5v which wasn't too bad.  But one day it went to 82.8v.  I opened and showed you the imbalance. So it wasn't due to old age or not doing long loads. If it had had a balancer, I should have raised the max voltage and not  drop little by little. The fact that there is no balancing means that the gap between the cells worsens over time. After manual balancing, I am more on 83.8/83.9v. I am giving you the photo of this battery which has not suffered  only long loads, which has never been loaded just after a run or rolled just after a long load.

[Silver]

 

Edited March 9, 2023 by Silver