bms Do Inmotion battery packs perform cell balancing? Yes!

[RagingGrandpa]

  

20 hours ago, Silver said:

 

4 hours ago, v8nice said:

There is no balance system at inmotion before v13.

3 hours ago, mrelwood said:

So, you have examined old V5 and V8 batteries, and because the cells are not well balanced, you are certain that they, V10, V11, and V12 series of wheels don’t have a balancing feature? Your definition of proof is humorous.

It triggered me too. 

Here's V11's BMS, showing the array of small resistors near their management ICs: 

Quote

 https://ecodrift.ru/2020/12/08/inmotion-v11-izmeneniya-v-dekabrskoj-partii/

And here's V12's BMS, with its even more distinct array of 24 bleed resistors:

Quote

 

It's resistive top-balancing.

Evidently, modern Inmotion EUC's include the same type of cell balancing electronics as their competitors.

It's "case closed" for me... if you're not convinced, feel free to discuss below  

Edited March 10, 2023 by RagingGrandpa

[lagger]

I think that it should have BMS. I hate this controversy.
The community is actively discussing this for year while all it takes is someone to analyse the PCB of controlboard and especially google search the IC used around these resistor arrays. Yes the layout doesnt look so distinctive and the resistors used are quite small but it could be. All it needs is this and instead of doing it everyone is just keeping the fire of this confusion. I wont be openning my pack but I am certain there are people with packs available and it needs just like 10 minutes of research to get the IC name and search for it.
Anyway I looked on some photos of V5F V10F and all have the resistor arrays. What was Adam showing is just back side.

[Chriull]

30 minutes ago, lagger said:

Yes the layout doesnt look so distinctive and the resistors used are quite small but it could be

1/4W as normal for 0805 smd resistors is more than enough.

Like an 100 Ohm resistor at 4.2V dissipates ~170mW. An 140Ohm resistor around 1/8W.

[mrelwood]

Found it in an old conversation:

[redfoxdude]

I hope someone at InMotion understands the damage to their brand Adam is doing here. This probably could have avoided with some better translators - I still feel like this was largely a language barrier thing, with things getting mixed up with representatives translating and playing telephone with the engineers. It would be nice to get the markings on the top of those ICs so we could pull up the datasheets, too.

Quote

This image^ has decent resolution for a closer look...
But certainly, it is possible to use very compact resistors with higher resistance for lower power dissipation. I see a lot of 1Ks around those ICs... Seems like they are using fancier balancer ICs with integrated shunt control, if I had to guess.

Edited March 11, 2023 by redfoxdude
formatting

[supercurio]

Thanks @RagingGrandpa for the further evidence presented in a very clear way!

@redfoxdude I agree that there's damage to the brand, but I believe it is all Inmotion doing it to themselves by fairly consistently giving bad information. I talked about the topic with Adam and he confirmed asked them several times and in different ways. And Inmotion has been insistent in answering that there is no balancing.  

Since it's again in the center of the attention, I'll try to get Inmotion to make a public official statement on that, with a clear, correct, checked list of

• which Inmotion wheels have balancing capability
• which Inmotion wheels don't have balancing capabilities
• what are the limitations of these if any (like minimum voltage that engages balancing)

We can't expect manufacturers to say whatever and the community to reverse-engineer their products in order to correct false statements. In one direction or another.

Edited March 10, 2023 by supercurio

[lagger]

5 hours ago, mrelwood said:

Found it in an old conversation:

Its funny. Even ChatGPT is certain that inmotion wheels have cell balancing capability:

Edited March 10, 2023 by lagger

[mhpr262]

Did anyone truly think they didnt have a BMS/cell balancing  system? It is just unthinkable and impossible to build a big battery pack like in an EUC, with so many cells connected in series, without some form of battery balancing. It would be a recipe for disaster otherwise. Li-ion cells dont work like the old Ni-Cd or NiMH cells where you safely overcharge some cells a bit to let the others "catch up".

[Mono]

9 minutes ago, mhpr262 said:

Did anyone truly think they didnt have a BMS/cell balancing  system?

Are you suggesting that Wrongway is lying (that is, deliberately misinforming his thousands of viewers)?

See also

 

Edited March 11, 2023 by Mono

[mhpr262]

Just now, Mono said:

Are you suggesting that Wrongway is lying?

He may not really know what he is talking about, or he made some innocent mistake/drew the wrong conclusion, or the individual wheel he examined was defective or something similar. I dont know. At any rate he was obviously wrong.

[Mono]

17 hours ago, mhpr262 said:

He may not really know what he is talking about, or he made some innocent mistake/drew the wrong conclusion

to be fair, Wrongway is not the only one. So the answer is "yes", several people (who opened up motherboard and batteries) truly believe that some InMotion wheels do not have cell balancing even if it may seem unthinkable to you.

Edited March 12, 2023 by Mono

[rcgldr]

If there is passive cell balancing in the V8F, it's not enough to prevent overvoltage of one or more cell pairs which stops all charging. 

The tech guy in Wrong Way's video mentioned the same issue with a V10 BMS. It stopped charging once a parallel cell group reached some maximum voltage, before the remaining groups had enough time to fully charge.

If there is passive | resistive top cell balancing, I assume there are two voltage levels: a voltage that enables bleeding resistors for balancing, and a slightly higher voltage that shuts down all charging. For example, 4.185 volts would trigger bleeding resistance, 4.2 volts would trigger charge shutdown.

If the passive | resistive top cell balancing worked as it should, then the bleeding resistors would hold or drain voltage to prevent any group of cells from reaching charge shut down voltage, and eventually all groups of cells would reach the bleeding resistor voltage, at which point the voltage would remain fixed (or nearly so), with nearly all of the current going through the bleeding resistors, no matter how long the pack was charging. If there are bleeding resistors, then they are only slowing the rate of voltage increase, not holding it or draining it, and eventually a group of cells reaches the shut down voltage before the rest of the groups have had enough time to reach the bleeding resistance voltage.

The other issue is that I have emailed service@imscv.com multiple times related to this, and twice they replied there is now passive cell balancing, but that could be a translation issue. I then asked what the 21 wires are used for, but have yet to receive an explanation.

With the stock charger, the LED changes from red to green once current drops below 400 mA, but it continues to output some current, and then I see voltage slowly decrease, about .4 volts per hour. To prevent the voltage decrease, I have to monitor voltage or watch the charger to disconnect it once the LED turns green. With the ewheels rapid charger, it goes into standby at 84.1 volts, 300 mA on the display, shutting down all charging, and the V8F shuts down about 10 seconds later, so I don't have to monitor it.

Edited April 12, 2023 by rcgldr

[mrelwood]

 

5 hours ago, rcgldr said:

It stopped charging once a parallel cell group reached some maximum voltage, before the remaining groups had enough time to fully charge.

Exactly.

5 hours ago, rcgldr said:

If there is passive | resistive top cell balancing, I assume there are two voltage levels: a voltage that enables bleeding resistors for balancing, and a slightly higher voltage that shuts down all charging. For example, 4.185 volts would trigger bleeding resistance, 4.2 volts would trigger charge shutdown.

Yes. Usually the voltage thresholds are 4.18-4.2V and 4.23-4.25V, but not many of the BMSs have been investigated this closely. The cutoff threshold is high, but since the cells are to be bled down to 4.18-4.2V right away anyway, I guess it has been decided not to do too much harm to the cells.

5 hours ago, rcgldr said:

If there are bleeding resistors, then they are only slowing the rate of voltage increase, not holding it or draining it, and eventually that group of cells reaches the shut down voltage before the rest of the groups have had enough time to reach the bleeding resistance voltage.

The rate at which the balancing resistors bleed the voltage is fixed, but as the charging is nearing the end, the charging current drops. If the pack is badly unbalanced, the balancing resistors only slow down the charging at first, but hopefully the charging current will slow down enough to match the bleeding current before the high voltage cells reach the cutoff voltage. In that case the pack would get balanced pretty well during a full charge + a little extra time for balancing. But again, if the pack is badly unbalanced, the charging will cut off before much balancing gets to happen.

5 hours ago, rcgldr said:

The other issue is that I have emailed service@imscv.com multiple times related to this, and twice they replied there is now passive cell balancing, but that could be a translation issue.

I’m making a video about this, and I’m including a superficial circuit analysis on most Inmotion wheels.

5 hours ago, rcgldr said:

I then asked what the 21 wires are used for, but have yet to receive an explanation.

Even if it didn’t have balancing, the BMS needs to monitor each cell group in order to be able to cut off the charging in an overvoltage situation.

5 hours ago, rcgldr said:

Fortunately for me, I have rapid charger that shuts down once current drops below 300 ma, which occurs at about 83.4 volts on my V8F, so I don't have to monitor it. I can then switch to the stock charger and monitor it so I can stop the charge once I see it start to decrease.

What baffles me in your situation is that the charging gets cut off at such high total voltage. 83.2V would still be considered a normal maximum charging voltage, and could easily be caused by imperfect voltage measurement system. But to have the charging interrupted just a few decimals short of 84.0V one would think that balancing should indeed be able to take care of the imbalance. I guess it can be possible that the BMS fails to balance the cells for some reason.

Another explanation could be that it’s the balancing resistors that are bleeding the voltage down to 83.0V (+/- measurement error). 83.0V / 20 = 4.15V, which does sound like a plausible lower balancing threshold voltage.

Have you tried to start charging again after the voltage drops down to 83.0V? 

Edited March 12, 2023 by mrelwood

[mrelwood]

In this video I'm analysing the rumor with superficial circuit analysis on V8, V8F, V10F, and V11, battery measurements on a 4000km old V11, experience with V10F charging behavior, discussion with an Inmotion engineer, and other arguments:

 

[lagger]

I just got my Hand on an Inmotion v10 that charges only up to 81.5V according to the wheel measurement. It is not the charger problem because when I charged my v10 it got charged to 83.5V (my usual voltage). I havent checked by voltmeter.

[mrelwood]

40 minutes ago, lagger said:

I just got my Hand on an Inmotion v10 that charges only up to 81.5V

I hope you didn’t pay much for the wheel, since that might be beyond what a cell balancing function can salvage.

 

[rcgldr]

12 hours ago, lagger said:

I havent checked by voltmeter.

Is there any way to check battery voltage without removing a shell to access the battery pack connector(s)?

[Chriull]

2 hours ago, rcgldr said:

Is there any way to check battery voltage without removing a shell to access the battery pack connector(s)?

By the reported voltage of the wheel (app) itself or if one makes an charge adapter were one can measure the voltage during charging. Or ones charger has a voltage display. Voltage at the plug during charging is more or less the battery voltage - the lower the charging current the more accurate.

[rcgldr]

4 hours ago, rcgldr said:

Is there any way to check battery voltage without removing a shell to access the battery pack connector(s)?

 

2 hours ago, Chriull said:

By the reported voltage of the wheel (app) itself or if one makes an charge adapter were one can measure the voltage during charging. Or ones charger has a voltage display. Voltage at the plug during charging is more or less the battery voltage - the lower the charging current the more accurate.

The reported voltage on my V8F may have been off before or it may off now that Inmotion increased the displayed voltage. Before Inmotion did a online "calibration", a 100% charge would show peak voltage of 83.4 and briefly 83.5 volts. After the Inmotion online "calibration", it shows a peak voltage of 84.0 volts and briefly 84.1 volts.  I don't know if this was an actual calibration or Inmotion just increased the displayed voltage.

I have an ewheels charger that displays voltage and current. For testing, I set it to 1 amp max charge, less than the stock charger 1.5 amp charge. The ewheels charger shuts off once current drops below 300 mA. Just before shut off, the charger displays 84.1 volts at 300 mA, and my V8F is showing 84.0 volts. When the ewheels charger shuts off, my V8F displays 83.9 volts, so the calibration may have resulted in my V8F reporting the actual voltage or close to it.

Note if using the ewheels charger on a V8F, the current can be set to 1, 2, or 3 amps, but do not set it to 4 or 5 amps, as that would be too much for 3500 mah batteries.

If I use the stock charger, and leave it running for more than 10 minutes after its LED turns green, rather than balancing the battery pack,my V8F shuts off charging due to what I assume is an overvoltage detection of one of the cell pairs, and my V8F voltage slowly decreases, about .4 to .5 volts per hour, due to the small amount of current used for blue tooth (I have EUC World running), and whatever other circuitry is active after V8F shuts off charging. With the stock charger, I have to watch the voltage display via EUC World and disconnect the charger from my V8F once it reaches full charge to prevent the slow voltage decrease. If I use the ewheels charger, it shuts itself off, which avoids the slow voltage decrease.

[rcgldr]

On 3/11/2023 at 8:27 PM, mrelwood said:

What baffles me in your situation is that the charging gets cut off at such high total voltage.

Another explanation could be that it’s the balancing resistors that are bleeding the voltage down to 83.0V (+/- measurement error). 83.0V / 20 = 4.15V, which does sound like a plausible lower balancing threshold voltage.

Have you tried to start charging again after the voltage drops down to 83.0V? 

Two days ago, my V8F was "calibrated". Following instructions I received in an email from Inmotion service, I charged my V8F until the stock charger LED changed to green, and with the new Inmotion app, clicked on diagnose | triple dot | online diagnose, sent an email to Inmotion service, which then did the calibration. This increased the reported voltage after a full charge from 83.4 to 83.9 volts. With the ewheels charger, the charger displays 84.1 volts, 0.30 amps, EUC World displays 84.0 volts just before charger shut off, and EUC World displays 83.9 volts just after charger shut off.  Prior to calibration, EUC World would display 83.4 volts just after charger shut off.

Before "calibration", if I left my V8F on the stock charger for 3 hours after the charger LED changed to green, the reported voltage was 82.5 volts which could be 83.0 volts after "calibration".

I don't know if reported voltage was more accurate prior to calibration than reported voltage after calibration, but 84.1 volts at 0.30 amps seems like it would be closer to 83.9 volts than 83.4 volts. It's possible that the pre-calibration reported full charge voltage decreasing from 83.6 volts when new (August 2021) to 83.4 volts a few days ago is due to some drift in the reported voltage as opposed to an actual decrease in full charge voltage. 

On 3/11/2023 at 8:27 PM, mrelwood said:

Have you tried to start charging again after the voltage drops down to 83.0V? 

Yes. Once the V8F stops charging due to overvoltage, it seems that regardless of the reduced voltage, it disables charging until I do a short ride. I tested before "calibration" so the voltages are relative, and may not be accurate. What I saw was 82.5|82.6 volts after leaving my V8F on the stock charger for 3 or so hours, and charging was disabled, even if I turned V8F off and on, then connected to charger. If instead I 100% charged to a reported 83.4 volts, did a short ride down to 82.8 volts, the V8F re-enabled charging.

On 3/13/2023 at 4:30 AM, mrelwood said:

In this video I'm analyzing the rumor with superficial circuit analysis on V8, V8F, V10F, and V11, battery measurements on a 4000km old V11, experience with V10F charging behavior, discussion with an Inmotion engineer, and other arguments:

The ewheels charger has been consistently going into standby and shutting off when the display shows 84.1 volts, 0.30 amps. This occurs whenever the current drops below 0.30 amps (at 80%, 90%, or 100% charge).

I did a test where I cycled the ewheels charger off and back on again after it went into standby. The LED immediately switched to green, and the display immediately showed 83.9|84.0 volts, 0.00 amps, which would normally indicate standby mode, but my V8F was able to sense the voltage, did not shut down and went into it's slow voltage decrease mode. I was using EUC World to monitor voltage, and saw it decrease to 83.8|83.7 volts, but the ewheels charger was still displaying 83.9|84.0 volts 0.00 amps, and I wasn't sure if this would harm the V8F, so I disconnected the charger, the V8F shut down and out of slow voltage decrease mode. 

It's possible that the slow decrease in voltage is some type of balancing, but I've tested this 3 times (leaving V8F on stock charger for 3+ hours), and I never saw an increase in full charge, but that could mean that my pack was already very close to balanced and already reaching max voltage (based on post calibration reported voltage of 83.9 volts), even though I mostly kept it at 76 volts and only did 100% charge every 1 to 2 months. 

If those 1000 ohm resistors are the bleeding resistors, then it would take a very long time to balance batteries at 0.042 amps. When the Inmotion EUC appears to stop the charging due to overvoltage as reported in Wrong Way's video, I saw 0.00 amps reported by the ewheels charger in slow voltage decrease mode, so if was balancing, it was drawing current from the battery pack itself for the balancing.

For the two people that took out V8 battery packs, and measured voltage at 4.2 volts for some cells, and 4.15 volts for most of the cells, I wonder if they had left them charging in slow discharge mode for a long time (8 to 10 hours) would have balanced the battery pack.

Edited April 12, 2023 by rcgldr

[rcgldr]

It's possible that the V8F BMS only discharges cells to 4.15 volts using the 1000 ohm resistors to discharge the cells with a discharge current of 0.0415 to 0.0420 amps. If this is true, then the slow discharge I see should stop once the battery pack is down to 83.0 volts. 

If anyone has a V8F, a stock charger, and EUC World (the current version of Inmotion App doesn't display voltage, only percentage), with EUC World running and the V8F charging overnight (or 4 to 6 hours after charger LED changes from red to green) with a stock charger, I'm wondering what the voltage ends up at and|or if the V8F shuts down and no longer communicates with EUC World.

The same test might work for V10F or V11, a slow decrease in voltage after a long time connected to a stock charger after the LED changes to green.

 

Edited April 12, 2023 by rcgldr

[mrelwood]

4 hours ago, rcgldr said:

The same test might work for V10F or V11, a slow decrease in voltage after a long time connected to a stock charger after the LED changes to green.

On the V11 with dual stock chargers, the voltage doesn’t drop, and the current keeps going down until it only powers the charger’s losses (and the Bluetooth circuit). The chargers never turns off, and the Bluetooth connection is kept alive.

[rcgldr]

1 hour ago, mrelwood said:

On the V11 with dual stock chargers, the voltage doesn’t drop, and the current keeps going down until it only powers the charger’s losses (and the Bluetooth circuit). The chargers never turns off, and the Bluetooth connection is kept alive.

Do you know what the actual voltage versus reported voltage is after a full charge with the stock chargers on your V11?

[mrelwood]

8 hours ago, rcgldr said:

Do you know what the actual voltage versus reported voltage is after a full charge with the stock chargers on your V11?

My V11 was voltage calibrated in 2020, and I think I recall it getting as close as 0.1 or 0.2 V, not sure. But this is unique to each V11 due to the individual calibration.

Edited April 13, 2023 by mrelwood

[rcgldr]

7 hours ago, mrelwood said:

My V11 was voltage calibrated in 2020, and I think I recall it getting as close as 0.1 or 0.2 V, not sure. But this is unique to each V11 due to the individual calibration.

I used the ewheels charger set to 80% charge (target voltage ~81 volts, ~4.05 volts per cell). It goes into standby once current drops below 0.30 amps. Cycling the charger's power off and back on again causes it to continue but with it's cooling exhaust fan off, so I used a small computer fan (AC Infinity AXIAL 8038, 7 watts) to blow air into the charger's vent holes on the other side of the charger. The current slowly decreased until the display showed 80.8 volts, 0.01 amps, EUC World displayed 81.0 volts, so one of the voltages is off by 0.2 volts. With nothing connected to charger, at 80%, it shows 81.0 volts, 0.00 amps. I cycled the charger power off and on again, and charger quickly displayed 80.8 volts, 0.01 amps, EUC World displayed 81.0 volts. I didn't see a slow decrease in voltage, so it's not taking very much current to run blue tooth, the blue battery SOC LEDs, ... .  My guess it that the actual current is less than .01 amps.

With a stock charger after the V8F shuts off charging, the stock charger continues supplying a small current and the V8F remains "awake" (blue tooth), and voltage slowly decreases. Post-calibration, probably down to 83.0 volts in 2 or 3 hours (not sure). If no one else tests this, I might leave the stock charger connected for longer to see if the voltage continues to drop below 83.0 volts or if the V8F re-enables charging once all cell pairs are down to 4.15 volts per pair, as a crude form of balancing.

 

Edited April 13, 2023 by rcgldr