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Is Wrongway right about V8S BMS?


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On 7/13/2022 at 1:43 AM, lagger said:

Without detail this is only my guess.

Missing from that image is 21 wires. In the images below, there are 10 white wires and 1 black wire. Looking at the other side of the board (second image below), there are 19 connectors labeled TB1 to TB19, plus B- and B+ for a total of 21 wires, that would be used to independently sense all 20 voltages from the 20 pairs of cells in the 20S2P pack. At 4:17 into Wrong Way's review of the V8S is an image of the V8S BMS, and those 19 BMS connectors are labeled B1 to B19, and all have wires, for a total of 21 wires.

 

v8fbmsf0.jpg.b936d16ce7bd602290790cab1a52f46c.jpg

 

v8fbmsb0.jpg.a76d3ee5d2f11648380897c2ffd49fa7.jpg

 

Edited by rcgldr
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  • 3 weeks later...

I bought my V8F back in August 2021, and have about 895 miles | 1440 km on it now. The fully charged voltage was and is still 83.6 volts, which is 4.18 volts per cell pair. Assuming the BMS includes passive balancing, this would make sense. The passive balancing logic would have 20 voltage triggered switches that enable resistors at 4.18 volts to hold the voltage of any fully charged pair while the remaining pairs continue to charge. (Paired cells will self-balance.) Once all cells are fully charged, then all the switches are enabled, limiting the pack voltage to 83.6 volts.

Edited by rcgldr
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  • 5 weeks later...

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. 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. 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.

PXL_20230112_122429013~2.jpg

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27 minutes ago, v8nice said:

it is obvious that there is no active or passive balancing.

Based on what you wrote, there’s nothing that would claim that there isn’t. Why exactly did you come to that conclusion?

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9 minutes ago, mrelwood said:

D'après ce que vous avez écrit, rien ne prétendrait qu'il n'y en a pas. Pourquoi exactement êtes-vous arrivé à cette conclusion ?

I showed you on the photo, written on the paper the beginning of the imbalance. Little by little, the battery becomes unbalanced. I solved the problem as soon as I observed the battery was charging less than before. No cells, no batteries.  is absolutely identical, with regular balancing it will not pose a problem, on the other hand without regular balancing, cells will have an increasingly low voltage with the numerous charges and discharges.

I'm thinking about integrating a 20-cell balancer soon.

there is a place to pull out the 20 wires easily from the battery.

PXL_20230126_134939863.jpg

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1 hour ago, v8nice said:

I showed you on the photo, written on the paper the beginning of the imbalance. Little by little, the battery becomes unbalanced.

Did you also measure the voltage of your charger? The most common reason for not charging to 84V is that the charger does not delivering the specified voltage (anymore, under load). That would also lead to a failure of balancing the cells.

Edited by Mono
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il y a 13 minutes, Mono a dit :

As-tu aussi mesuré la tension de ton chargeur ? La raison la plus courante de ne pas charger à 84 V est que le chargeur ne fournit pas la tension indiquée (plus, sous charge). Cela conduirait également à un échec de l'équilibrage des cellules.

Of course, I measured the voltage of the charger before opening my battery.

 

 84.4v at charger output

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2 hours ago, v8nice said:

Of course, I measured the voltage of the charger before opening my battery.

 

 84.4v at charger output

That's without load and doesn't necessarily mean it will charge a perfectly healthy battery to 84V, unfortunately. I guess you will find out when you charge the recovered battery.

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I set the original charger to 84.6v but actually on my 2 batteries (v8 and v8f) it does not really charge at more than 83.9v. I can still set the original charger a little higher, do you think it is?  is a good solution?

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1 hour ago, v8nice said:

I set the original charger to 84.6v but actually on my 2 batteries (v8 and v8f) it does not really charge at more than 83.9v. I can still set the original charger a little higher, do you think it is?  is a good solution?

If it charges to 83.9V that looks perfectly fine to me.

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5 hours ago, v8nice said:

I set the original charger to 84.6v but actually on my 2 batteries (v8 and v8f) it does not really charge at more than 83.9v. I can still set the original charger a little higher, do you think it is?  is a good solution?

You do know that batteries lose their capacity over time.. Yeah they are 84v, but after time, or some driven distance it will drop...

Like new pack will be 84v, but after time it will be 83.9v, then 83.8v, 83.7, 83.6, so on.. You can't recharge them to 84v ever again. Because of lost capacity.

Same as my 18xl out of box it was 84.5v, 1 year later it's now 84.3v.. Losing 00.1v over some time is normal.

 

If now you have 83.9v - it's the best you will have.

 

Also your difference between packs where max 0.05v.. And you even saw some cells where 4.2v, some 4.15v. I personally would start to worry, if the difference in packs would be 1v - 1.5v, because 0.05v as "whole" pack is almost nothing. Easily could have done 5000miles, before you need to start thinking about manual balancing.

SORRY - I said watt-hour(Wh) and voltage(V) - in same manner.. You can forget anything i said. :D 

 

Also by setting charger "higher" you are somewhat risking damaging batteries. Because battery is rated 84v.. Yet you are giving them more volts. (Luckily BMS will stop charging cells at 4.2v, so setting charger "higher" is pointless.) As i said before. Older batteries - less capacity. You won't have 84v ever again.

 

 

(Someone whos more intellectual about these matters could chime in? If what i'm talking about is even right?):D

Edited by Funky
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2 hours ago, Funky said:

Like new pack will be 84v, but after time it will be 83.9v, then 83.8v, 83.7, 83.6, so on.. You can't recharge them to 84v ever again. Because of lost capacity.

No, don’t confuse voltage (V) with capacity (Wh). One doesn’t say practically anything about the other. A battery can have barely any capacity left in it at all, yet still provide a full healthy voltage under no load.

 The total voltage of a battery pack is a sum of 16-32 cell groups, and it can fluctuate due to the charger’s voltage drift, battery cell voltage imbalance, EUC measurement component drift, etc. It’s common to have +- 0.5V or even 1V differences in the wheel reported total voltage by just replacing the mainboard.

1V difference in cell voltages would be catastrophical, I think active balancers keep it under 0.05V or 0.1V or something.

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4 minutes ago, mrelwood said:

 

No, don’t confuse voltage (V) with capacity (Wh). One doesn’t say practically anything about the other. A battery can have barely any capacity left in it at all, yet still provide a full healthy voltage under no load.

 The total voltage of a battery pack is a sum of 16-32 cell groups, and it can fluctuate due to the charger’s voltage drift, battery cell voltage imbalance, EUC measurement component drift, etc. It’s common to have +- 0.5V or even 1V differences in the wheel reported total voltage by just replacing the mainboard.

1V difference in cell voltages would be catastrophical, I think active balancers keep it under 0.05V or 0.1V or something.

Ahh yeah.. Voltage doesn't change. Wh did.. Wh was the one that gets lower over time/distance driven. Somehow completely let that fly bay.. - UPS. :D 

Doh i also have noticed that over year i have lost about 0.02v.. How? Because completely new i had 84.5v / 84.4v. But now it's normally 84.3v /  84.2v. (Yeah i know 0.02v isn't anything worth talking about. But i noticed it and like to know why it went down..) Did the packs settle down after some use or something? Did me adding extension cord for charger did something. Who knows. :D Or simple ~0.05V misread, so called "error" can be made in app, when reading wheel voltage.

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7 hours ago, Funky said:

Doh i also have noticed that over year i have lost about 0.02v.. How? Because completely new i had 84.5v / 84.4v. But now it's normally 84.3v /  84.2v. (Yeah i know 0.02v isn't anything worth talking about. But i noticed it and like to know why it went down..)

The difference is 0.2V. Not 0.02V!

7 hours ago, Funky said:

Did the packs settle down after some use or something? Did me adding extension cord for charger did something. Who knows. :D Or simple ~0.05V misread, so called "error" can be made in app, when reading wheel voltage.

0.2V of 84V is 0.2% difference.

Over a year with possibly different temperatures, humidity and whatever that's within normal drift/aging of electric measurement devices.

Anyway way beyond normal multimeter accuracy.

Edited by Chriull
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On 1/28/2023 at 3:46 PM, mrelwood said:

 

No, don’t confuse voltage (V) with capacity (Wh). One doesn’t say practically anything about the other. A battery can have barely any capacity left in it at all, yet still provide a full healthy voltage under no load.

 The total voltage of a battery pack is a sum of 16-32 cell groups, and it can fluctuate due to the charger’s voltage drift, battery cell voltage imbalance, EUC measurement component drift, etc. It’s common to have +- 0.5V or even 1V differences in the wheel reported total voltage by just replacing the mainboard.

1V difference in cell voltages would be catastrophical, I think active balancers keep it under 0.05V or 0.1V or something.

What is active balancers?

For the moment my v8 battery works little good on my v8F ,small différence with v8f battery .It have 6000miles and after my manually balancing ( 1 cell 3.66v ,1 cell 4v others 4.15v ). After 10 cycles i check the cells and make a real return here.

 

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7 hours ago, v8nice said:

What is active balancers?

For the moment my v8 battery works little good on my v8F ,small différence with v8f battery .It have 6000miles and after my manually balancing ( 1 cell 3.66v ,1 cell 4v others 4.15v ). After 10 cycles i check the cells and make a real return here.

 

If you arrange balancing wires you can monitor and adjust voltages easier than opening up the pack like that. You can also get a 3A single charger to charge the low cells faster.

I don't think there's space for a 20s balancing board. You could attach a smaller board like 3-5s to only the weak cells. It would pull down the voltage of the cells around the weak group, and give you more time before you need to manually balance. 

Most inexpensive third party balancers out there are based on the same circuit. It starts balancing at a 0.10v difference, and stops at 0.03v. That means the result isn't going to be perfectly even voltages. It's good enough to not have to worry about the voltages for a longer time. As long as the wheel charges to nearly 84v you know the balancer is doing its job.

Edited by alcatraz
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I've contacted Inmotion service via email, and they state there is no passive cell balancing, but have yet to offer a reason for the 21 wires connected in series with the 20 series of cell pairs in the battery pack (the pads are labeled B-, TB1 to TB19, B+). They claim to be investigating what those 21 wires are being used for.

 

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13 hours ago, rcgldr said:

I've contacted Inmotion service via email, and they state there is no passive cell balancing

We’re you discussing the V8 or V8F?

 Some people had asked Inmotion earlier about balancing concerning the V11 and V12, and had gotten an answer that there is no balancing. When I asked, Cecily from Inmotion confirmed from the Inmotion engineers that there indeed is passive top balancing in these wheels.

 My guess is that the English terminology is not familiar to them, and unless explained in more detail like I did, the question is often misunderstood.

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4 hours ago, mrelwood said:

My guess is that the English terminology is not familiar to them, and unless explained in more detail like I did, the question is often misunderstood.

I have been suspecting this - passive balancing might be interpreted as, while not charging, passively balancing while the device is idle, but that's not what we mean.

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6 hours ago, redfoxdude said:

I have been suspecting this - passive balancing might be interpreted as, while not charging, passively balancing while the device is idle, but that's not what we mean.

It isn't?:huh::confused1: I thought by passive balancing it meant - that all cells while not charging, stay about same charge +/- 0.1v-0.3v? Because of passive balancing there isn't a chance for some cells to be more empty than others.. Like some being 4.2v, same time some being 4.15v, or 3.99v?

 

What the heck is passive balancing then. :D (One would think "passive" would mean that..) How does the "passive balancing" work then? If all other wheels have it and InMotion doesn't?

 

 

Do people mean when charging the wheel, charge slowly - slows down, as it gets fully charged? And then that "passive balancing" happens? The last 1-2% of wheels charge?

Edited by Funky
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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.

if a cell loses 0.01v at each cycle after 50 cycles it will have lost 0.5v, about 50% less autonomy. Whereas with balancing every 10 charges, for example, the battery would be "like new". there is a loss of capacity with each cycle, but it is negligible! The loss of capacity is due to cell wear, not to balancing problems, except at inmotion!

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16 hours ago, mrelwood said:

We’re you discussing the V8 or V8F?

V8F.

5 hours ago, Funky said:

charge slows down, as it gets fully charged?

Current is decreased as voltage reaches some set maximum value. For 84V volt EUC's the ewheels charger can be set for 80, 82, or 84 volts as the max charge voltage, and 1 to 5 amps max current, with the max at 3 amps for V8F 3500 mah battery pack. With a 100% 84 volt and 1 to 3 amp setting, current starts to decrease at around 82 volts, down to 300 ma to a reported 83.4 volts where it goes into standby and completely stops charging. If I then switch to the stock charger, voltage will slowly increase to a reported 83.6 volts.

 

5 hours ago, Funky said:

What the heck is passive balancing then.   

Passive cell balancing:

https://www.analog.com/en/technical-articles/passive-battery-cell-balancing.html

Going by the reported 83.6 volts for the 20S2P pack on my V8F, the voltage sensitive switches are set for 4.18 volts per cell pair, if there is passive cell balancing.  Note that cells in parallel self-balance all the time, it's only the cells in series where balancing logic is used. Inmotion support is investigating what those 21 wires are being used for, and will email me back when they have an answer, assuming they're actually investigating this.

Since the voltage sensitive switches are set to a fixed voltage, passive cell balancing only occurs with a 100% charge. Using the ewheels 80 or 82 volt settings is done to partially charge a battery pack, without having to constantly monitor the charge, since it will ramp down current and go into standby (stop charging) once the selected voltage is reached.

 

Edited by rcgldr
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5 hours ago, Funky said:

It isn't?:huh::confused1: I thought by passive balancing it meant - that all cells while not charging, stay about same charge +/- 0.1v-0.3v?

No. Most EUCs use “passive top balancing” mechanism. It means that each individual cell group gets it’s voltage lowered when it goes above about 4.18V. If one cell group is higher than the rest, it gets bled out at the end of the charge when the high group is the first one to reach and surpass 4.18V.

 What makes it “passive” is that there is no mechanism actively monitoring the cell group voltages. What makes it “top balancing” Is that it only activates a hair short of the maximum voltage. That’s why it’s usually recommended to leave the charger on for an extra hour or so after the charger turns green, since the balancing hasn’t been running for very long at that point.

 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.

5 hours ago, Funky said:

If all other wheels have it and InMotion doesn't?

Most wheels do, for example Inmotion V11 and V12. Not sure about V10, but I’d say it probably does have.

5 hours ago, Funky said:

Do people mean when charging the wheel, charge slowly - slows down, as it gets fully charged? And then that "passive balancing" happens? The last 1-2% of wheels charge?

Charging slowing down is a natural and unavoidable part of any battery charging process. If the cell groups are perfectly balanced, no balancing happens during the charge. If they’re badly out of balance, balancing can start well before reaching 100%.

 The issue with passive top balancing is that if the balance gets bad enough (always charged only to 80% for example), when the balancing starts the charging current is still high enough that the highest cell groups reach the charge cutoff voltage 4.25V before the cells are balanced. That’s when the charging is interrupted by the BMS, and the owner creates a topic here asking why their wheel doesn’t charge to higher than 94% or something. And they’ll only learn then that they have actually ruined their battery by trying to lengthen the battery life by only charging to 80%.


 

51 minutes ago, v8nice said:

The loss of capacity is due to cell wear, not to balancing problems, except at inmotion!

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.

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35 minutes ago, mrelwood said:

No. Most EUCs use “passive top balancing” mechanism. It means that each individual cell group gets it’s voltage lowered when it goes above about 4.18V. If one cell group is higher than the rest, it gets bled out at the end of the charge when the high group is the first one to reach and surpass 4.18V.

 What makes it “passive” is that there is no mechanism actively monitoring the cell group voltages. What makes it “top balancing” Is that it only activates a hair short of the maximum voltage. That’s why it’s usually recommended to leave the charger on for an extra hour or so after the charger turns green, since the balancing hasn’t been running for very long at that point.

 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.

Most wheels do, for example Inmotion V11 and V12. Not sure about V10, but I’d say it probably does have.

Charging slowing down is a natural and unavoidable part of any battery charging process. If the cell groups are perfectly balanced, no balancing happens during the charge. If they’re badly out of balance, balancing can start well before reaching 100%.

Yeah i already figured that out myself. My charger has turned green and app shows already full battery. (But same time it's still drawing ~50W from wall.) As i normally keep charger connected for another ~2hours. 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.. 

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

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