Is Wrongway right about V8S BMS?

[Tawpie]

2 hours ago, rcgldr said:

peak voltage remained at 83.4 volts

Do keep in mind that 83.4 V total means the average voltage of each cell group is 83.4 / 20 = 4.17 V

The maximum safe voltage for a cell is 4.2 V, you're (on average) 30 mV from the "do not go higher than this" point... I wouldn't worry about it.

Edited March 17, 2023 by Tawpie

[Chriull]

5 hours ago, rcgldr said:

waited a few minutes,

That's way to short for abything to happen. The bleeding resistor of 1kOhm could nedd 1-2days to bleed a full cell groups overvoltage.

5 hours ago, rcgldr said:

I tried @v8nicesuggestion of charging | short ride | charging | short ride | ... for about 6 cycles. Didn't seem to make any difference, peak voltage remained at 83.4 volts with intermittent display of 83.5 volts.

Discharge lowers all cell voltages about equal - so by a short ride the voltage delta to be lowered by a bleeding resistor is kept.

For slowing the charge the cells detoriation state seems to be too much for the bleeding resistor to notable reduce charging current.

So nothing changes with this strategy.

[rcgldr]

5 hours ago, rcgldr said:

3 hours ... 82.5 volts ... I disconnected my V8F from the charger, waited a few minutes, the connected the charger again

 

33 minutes ago, Chriull said:

That's way to short for anything to happen. The bleeding resistor of 1kOhm could need 1-2days to bleed a full cell groups overvoltage.

After the V8f disabled charging, and during the next 3 hours while connected to the charger and monitoring voltage with EUC World, the pack voltage had decreased from 83.4 volts to 82.5 volts. At this voltage, connecting the charger would normally result in the LED turning red, but it remained green, as the V8F remained in charge disabled mode, and the voltage continued to slowly decrease. By comparison, I could charge to 83.4 volts, do a very short ride to decrease pack voltage to the same 82.5 volts, and connecting the charger resulted in the LED turning red indicating it was charging, and I could see the voltage increasing back to 83.4 volts. My guess is once the V8F disables charging, it needs to be turned on, and possibly has to be ridden in order to enable charging again.

Edited March 17, 2023 by rcgldr

[rcgldr]

2 hours ago, Tawpie said:

Do keep in mind that 83.4 V total means the average voltage of each cell group is 83.4 / 20 = 4.17 V

Worst case, although not realistic, 83.4 volts could be 19 groups at 4.2 volts, 1 group at 3.6 volts. A more reasonable case could be 8 groups at 4.2 volts, 12 groups at 4.15 volts. 

[v8nice]

we agree that it does not balance and that little by little the wheel takes less load ... I tried for 2 years to balance my new v8f, despite everything, little by little I had less maximum load. I increased the voltage of the charger from 84.4v and 84.6v, and it did not change. When I received the wheel I charged up to 83.6 and 83.8v, then quickly it became 83.6v maximum. Then 1 year after 83.5v. and then 83.4v and suddenly I had loads sometimes 82.8v and sometimes 83.4v. I opened and showed you, 15 cells of around 4.15v and 5 cells about 4.2v. The bms has therefore never managed to restore balance in 2 years with only long charges. At best, always doing long charges allows you not to unbalance too quickly, or rather unbalance slowly ....

[rcgldr]

On 1/27/2023 at 8:06 AM, v8nice said:

v8f ... recharge for a long time.

Can you repeat this with a stock charger, letting it run for 4 or 5 hours? Using a stock charger on my V8F, the V8F detects an overvoltage of one of the cell pairs and charging stops, but it continues to communicate with EUC World, and I can see the voltage slowly decline. I disconnected the charger at around 83 volts (2 to 3 hours, not sure) and don't know if it would have continued to decrease voltage below 83.0 volts if left connected to charger for another hour or two. I was wondering if there is some logic that slowly discharges all cell pairs down to 4.15 volts using those 1000 ohm resistors, and then stops using those 1000 ohm resistors, or if the slow decrease in voltage is just due to blue tooth and other circuitry running and there is no balancing logic at all. I have to disconnect the charger from the V8F in order for the V8F to shut down and not slowly decrease the voltage.

On my V8F (received July 30, 2021), once overvoltage stops the charging, I have to do a short ride (half a mile is good enough) before it re-enables charging.

Wrong Way made another video about Inmotion EUCs having overvoltage detection, but not passive cell balancing except for the V13:

https://www.youtube.com/watch?v=2DUyKsftD0c

 

Edited April 14, 2023 by rcgldr

[v8nice]

on my v8F currently it charges up to 83.9v since I did the balance. On the v5f that I had, it charged up to 83.6v, then stopped and went down to 81.5v and I stopped charging  .There was a very small imbalance on the battery, I did the manual balancing and now it charges well up to 84.2v and even leaving the charger plugged in for 1 night, it still remains at 84.2. For the moment everything is fine  for about 2 months with the batteries repaired. The day it becomes unbalanced, I will open the battery and do the same thing again.

[rcgldr]

3 hours ago, v8nice said:

For the moment everything is fine  for about 2 months with the batteries repaired. The day it becomes unbalanced, I will open the battery and do the same thing again.

If either becomes imbalanced again, I 'm wondering if you could try leaving the EUC on a stock charger for about 8 hours, to see if there is any balancing during the very slow discharge that I see on my V8F after the V8F shuts off charging due to overvoltage detection, but remains awake as long as the charger is outputting voltage, with the V8F only drawing enough current to detect a charger is present (if using eWheels charger, it shows 0.00 amps, so I assume less than 0.005 amps). If this doesn't work, then there is no balancing during charge or discharge.

Edited May 3, 2023 by rcgldr

[v8nice]

here, the problem of discharge after the load reappears on the v5f whose cells I had rebalanced. The charger charges up to 84.2v, then then, the charger is green the voltage drops slowly. After 1 hour the voltage is 83.25v , even if the charger is plugged in. The charger is checked at 84.4v. The wheel has traveled 400km since the manual rebalancing, and I have only made total and long charges. I checked my voltage at each complete charge, it was always between 84.1 and 84.2v. These BMS are crap that disrupt the cells instead of balancing them...

[rcgldr]

9 minutes ago, v8nice said:

here, the problem of discharge after the load reappears on the v5f whose cells I had rebalanced. The charger charges up to 84.2v, then then, the charger is green the voltage drops slowly. After 1 hour the voltage is 83.25v , even if the charger is plugged in.

On my V8F, with charger connected, after reaching a peak voltage, voltage will slowly decrease over the next 8 hours or so until it goes below 82.6 volts, after which it will start charging again, for maybe 20 minutes before it halts charging and goes through another 8 1/2 hour cycle. What I don't know is if there is some type of slow balancing going on during the slow 8 hour or so discharge. I kept track of elapsed time versus voltage:

elapsed time - reported voltage (using EUC World):

00:00 - 84.0 - charging disabled, voltage declines

01:00 - 83.5

02:00 - 83.3

03:00 - 83.1

07:00 - 82.7

08:10 - 83.3 - charging re-enabled, charger led changed to red

08:30 - 84.0 - charging disabled, voltage declines

09:30 - 83.5

12:30 - 83.1

15:00 - 82.8

17:00 - 82.6

17:10 - 83.3 - charging re-enabled, charger led changed to red

17:30 - 84.0 - charging disabled, voltage declines

 

Edited May 18, 2023 by rcgldr

[v8nice]

2 days ago the charge after long charge fix at 84.1v and never go down.Why it s different now. 

[v8nice]

Ok,i have fix the problem.

the problem is related to the voltage of the charger. Like all inmotion chargers that I have had, the voltage varies a little. It was at 84.5v which was very suitable for the v8f, charged closer to 84v with this setting.  On the other hand the v5f emptied slowly once reaching 84.1v with this setting....I lowered the charger to 84.4/84.3v. The v5f now rises to 83.9v, charger turns green, then it continues to rise slowly  up to 84.05v. On the other hand the v8f with this setting only charges at 83.65v....I only have a charger for the 2 wheels with an adapter...

[v8nice]

in the end, it doesn't really work any better, it rises slowly to 84.05v but after, it goes down again. When even .... for 2 months it didn't do that at all, it remained in charge even if it didn't go any further.  I think the charging socket gets stuck but the motherboard stays on standby, because it detects the charger although it no longer supplies the battery...I think the charging system on these wheels, at least the v5 models/  v8/v10 is made by idiots.

[UniCycler]

I recommend to put a power meter between the charger and the power outlet to monitor how long charging really takes place. Forget the green light. ;-) When the charger stops charging it uses only 1 W. Whenever there is any minimal DC output current the charger will take more than 1 W. With this method you can monitor when the first cell gets to 4.25V and the overvoltage cutoff stops charging. The overall voltage at this moment gives information about the imbalance of the pack. A perfectly balanced pack will come very close to the output voltage of a charger until it really stops.

My observation with a 6 year old V8 which I recently bought as "defective" because it only has 3 km range, is the same as @v8nice described. One cell cluster has had only 3.5V while the others have had around 4.1V on a fully charged battery. After manually rebalancing the cells, almost the original range could be restored.

As a rule of thumb, a 100mV imbalance in the battery pack will reduce range by 10%.

I agree with the assumption of wrongway that totally no cell balancing is implemented in the BMS of the V8 and V10. The 1 kOhm resistors on the BMS are in my opinion just for measuring the cluster voltages by the AFE chip (analog front end) and not for bleeding any top balancing energy. For that case they would be much to small and would have to much resistance. For effectively balancing a battery like from the V8 or V10 a balancing current of at least 50-100 mA would be needed.  With a 1k resistor you would get in best case 4 mA which is nothing.

Edited May 23, 2023 by UniCycler

[mrelwood]

7 hours ago, UniCycler said:

The 1 kOhm resistors on the BMS are in my opinion just for measuring the cluster voltages by the AFE chip (analog front end) and not for bleeding any top balancing energy.

Could be.

7 hours ago, UniCycler said:

For that case they would be much to small and would have to much resistance.

Then how come the V11 and V12 are balancing through 1K resistors?

[UniCycler]

10 hours ago, mrelwood said:

Then how come the V11 and V12 are balancing through 1K resistors?

How do you know that they do? 

I am meanwhile 100% sure that the BMS of V8 and V10 don't do cell balancing, because I found out the names of the chips. The used circuits which measure the cell voltages are called SH367108 (38-pin) and SH367105 (20-pin). The first is responsible for monitoring 15 cell voltages and the second one for 5 cell voltages. They are used cascaded and only able for protecting measurements. So the dream of cell balancing (at least for the V8 and V10) is over, sorry guys ;-)

https://datasheetspdf.com/pdf-file/1354829/SinoWealthMicroelectronic/SH367108/1

I don't know which chips are used in the V11 and V12 because I've never had a BMS of them in my hands, but I strongly doubt that they use different ones.

[mrelwood]

6 hours ago, UniCycler said:

How do you know that they do? 

Because I measured my V11 cells after 4000 km, and the differences were less than 0.01V. The odds for that without balancing are simply too small. Also, the battery packs generally last for much longer than they would without balancing. People who only charge to 80% have had their packs die (unbalanced too far to be safe to ride) as soon as 2000km.

Edit: Also, a few people have had Inmotions (V10F and V11 iirc) that won’t charge to full (because of an unbalanced pack), but after charging to full + a few hours and discharging only a little, then repeat, the batteries have started to charge to full again. There hasn’t been an explanation how that could’ve happened if the cells didn’t balance.

Edited May 24, 2023 by mrelwood

[v8nice]

you are stubborn to think that these bms balance, in any case for my part v5/v8/v10 does not balance, or badly which is the same result. Each time someone a little more serious on the subject comes demonstrated that it does not balance you find a reason, Unicycler has to control the components of the bms, and technically it cannot balance cells, those who are lucky enough to have batteries from the same series will have less imbalance, on the other plus.I am almost certain that batteries are assembled with batteries having imbalances from the factory outlet that the bms will never be able to correct, which leads to the premature "death" of the battery. Another problem noticed on many inmotion chargers, the components seem to be of poor quality, the charging voltage can vary from day to day, which will also affect the charge. The 1k resistor can only restore imbalances of 0.01v for example and the batteries having 0.05v difference, the balance is never restored by the bms, you can try to play with several light charges and discharges to rebalance but it will only be luck that can rebalance the cells, not the bms...And I can't understand why this v5 discharges when fully charged when it hasn't since the manual rebalancing, as well as the 20 times I left the charger overnight. throw in this charging system everything! As I said many have no problem because it does not check the charge, does not use all the battery so do not realize anything, if it rolls can the problem will happen in a long time and they will throw the machine away if they don't know anyone competent.

[mrelwood]

1 hour ago, v8nice said:

you are stubborn to think that these bms balance, in any case for my part v5/v8/v10 does not balance, or badly which is the same result.

All the evidence I’ve seen for V11 and V10F does suggest that they do balance the cells. They behave in a way that would be practically impossible if they didn’t.

 Based on what I’ve heard from you and @rcgldr, it does sound like your older model V8 units wouldn’t balance the cells at all. The V8S BMS layout for example did look distinctively different though, and it had the similar resistor groups that the V11 has.

There’s a tragic difference whether a BMS balances extremely slowly or not at all though. With a healthy pack “extremely slowly” is enough to keep the pack balanced.

1 hour ago, v8nice said:

Each time someone a little more serious on the subject comes demonstrated that it does not balance you find a reason

I haven’t seen anyone bring up evidence that the V10F, V11 and V12 wouldn’t have cell balancing. Only the V8 and V5.

1 hour ago, v8nice said:

Another problem noticed on many inmotion chargers, the components seem to be of poor quality, the charging voltage can vary from day to day, which will also affect the charge.

I only have experience with two V11 chargers, and they have been working fine for the three years I’ve had them. Haven’t heard of issues on other V11 chargers either.

1 hour ago, v8nice said:

The 1k resistor can only restore imbalances of 0.01v for example

The 1K resistor would balance very slowly, but it wouldn’t specifically set a limit to the amount of inbalance it would handle.

 Though even if it did, in normal usage it wouldn’t have to balance higher discrepancies than that. I don’t think a healthy pack would get more imbalance than that during a single discharge.

1 hour ago, v8nice said:

you can try to play with several light charges and discharges to rebalance but it will only be luck that can rebalance the cells, not the bms...

Luck doesn’t balance the cells though. Neither does prayer. It requires electronics to do that.

1 hour ago, v8nice said:

And I can't understand why this v5 discharges when fully charged when it hasn't since the manual rebalancing

That’s how the individual cell group’s overvoltage system usually works. But instead of bleeding just the overvoltage cells, yours seem to bleed down the whole pack.

[v8nice]

My Friend have a v10f for one years.Buy it with 0km and the max charge never go more than 83v ,and long charge (48h)never change that and charger it ok with 84.3v .

My expérience with 4 inmotion wheel and charger.

My charger v8d dead after 2years .

With my old v8 ,tension varie sometimes 84.4v sometimes 82v.

With the v5f charger ,i tune to 84.2v monday  i check it tuesday ok.After 1 week i re check it s 84.5v now ...it s not possible the screw tune, turn alone in my garage...

[avevo]

25 minutes ago, v8nice said:

After 1 week i re check it s 84.5v now ...it s not possible the screw tune, turn alone in my garage...

Inmotion will re-calibrate the internal voltmeter for free, as long as your original shop/distributor can contact them and provide the serial number; they will only do it "on-line" (that is, wheel fully charged/balanced, Inmotion app running and connected to internet, and some Inmotion engineer from China will send the software recalibration command). I think they're right to not to let the end user recalibrate, because if something wrong happens while riding...

I had a similar problem with my V10F, the charging reported 85V, 86V, 87V at the end of charging, getting worse and worse over several months, then the error "Overload please get off" while still charging. The battery, measured with a digital tester, correctly reported 82-83V. That is, the internal voltmeter inaccuracy was several volts. Funny enough, I once was able to do 12+ kilometers before the battery indicator dropped from 100% to 99%, that's insane.

And I had to get back home before the charge went below 40-50%, because the voltmeter error would hide the "battery voltage very low" condition (it said "77V" and I knew that it was 7 volts lower, actually 70V, that is, almost empty... the battery pack would get damaged if I kept riding).

Also, I had to seriously watch out my braking habits because regenerative braking would have pushed the voltage past the 87.1V limit (the wheel goes "hard tiltback" and keeps repeating "Overload please get off" for hours, you have to physically disconnect the battery to reset the error).

The remote re-calibration wasn't enough because the internal voltmeter kept drifting over the following weeks. I eventually had to buy a new Inmotion v!0f mainboard.

[mrelwood]

2 hours ago, avevo said:

Inmotion will re-calibrate the internal voltmeter for free …

They will, but @v8nice was talking about the charger’s output voltage.

[rcgldr]

8 hours ago, avevo said:

Inmotion will re-calibrate the internal voltmeter for free, as long as your original shop/distributor can contact them and provide the serial number; they will only do it "on-line" (that is, wheel fully charged/balanced, Inmotion app running and connected to internet, and some Inmotion engineer from China will send the software recalibration command). I think they're right to not to let the end user recalibrate, because if something wrong happens while riding...

Inmotion did that with my V8F, but I'm not sure how accurate the "re-calibration" is. I'm wondering if the "re-calibration" just assumes a "fully charged" EUC is at 84.0 volts, and just sets the voltmeter to 84.0 volts regardless of what the actual pack voltage is. The issue is at full charge,the pack is at a steep part of the voltage versus state of charge curve, and even a slight discharge could drop pack voltage .1 or .2 volts, and I suspect my V8F voltmeter is about .2 volts high.

[rcgldr]

On 5/26/2023 at 6:11 PM, mrelwood said:

With a healthy pack “extremely slowly” is enough to keep the pack balanced. The 1K resistor would balance very slowly, but it wouldn’t specifically set a limit to the amount of inbalance it would handle. ... instead of bleeding just the overvoltage cells, yours seem to bleed down the whole pack.

A 1k resistor translates into a max discharge current of 4.2 mA. It seems very unlikely that charging current for the pack would drop below 4.2 mA, so the highest voltage cell group will continue to charge at only a slightly slower rate than the rest of the cell groups, reach overvoltage threshold, at which point charging stops. As I posted in my prior comments, during the 8 hours or so of slow discharge after overvoltage stops charging, and while still connected to stock charger, my V8F could be balancing during the slow discharge, but I don't have any way to know if this occurs or not. 

[ursi]

Is there a conclusive answer to the titular question somewhere in these 8 pages?