How important is a smart BMS?

[Samantha_C]

Hi everyone,

 

Can someone explain in lay terms why a smart BMS is so important for an EUC?

I know many will claim it is a safety issue due to battery degradation etc, but does the smart BMS actually prevents and fixes degradation?
Or does it just tell you something is wrong (i.e. unbalanced cells) but you gotta fix it with your wits?

I'm asking because there's been a lot of push towards this, but not many wheels have it, especially the smaller ones. I heard the battery might blow up in my face, or the wheel would suddenly cut off without a smart BMS, which has never happened to me, thankfully, but it curtailed my enthusiasm for smaller and older wheels. 

Is a smart BMS reserved for enthusiasts? As an average rider, I certainly wouldn't know what to do with the information I glean from it. All I do is let the passive cell balancing do its job and hope for the best. Should I be worried? 

 

Thanks...

[rcgldr]

Begode Falcon is one of the few small EUCs that supposedly has a a smart BMS. Passive cell balancing should be good enough if the firmware reports an issue with a weak cell group. The Inmotion V8 and V10 series don't have passive cell balancing, instead once some cell group reaches overvoltage, they just shut off charging and slowly discharge. In the case of my V8F 8 hours for a slow discharge down to 82.5 volts before it reenables charging, which lasts for 15 to 20 minutes before reaching overvoltage again and repeating the cycle. I don't know if V11 and V12 also lack true passive cell balancing. Some of the high end EUCs have active cell balancing.

 

[Samantha_C]

28 minutes ago, rcgldr said:

Begode Falcon is one of the few small EUCs that supposedly has a a smart BMS. Passive cell balancing should be good enough if the firmware reports an issue with a weak cell group. The Inmotion V8 and V10 series don't have passive cell balancing, instead once some cell group reaches overvoltage, they just shut off charging and slowly discharge. In the case of my V8F 8 hours for a slow discharge down to 82.5 volts before it reenables charging, which lasts for 15 to 20 minutes before reaching overvoltage again and repeating the cycle. I don't know if V11 and V12 also lack true passive cell balancing. Some of the high end EUCs have active cell balancing.

 

Which wheels have active cell balancing? I'd love to know.

[rcgldr]

3 hours ago, Samantha_C said:

Which wheels have active cell balancing? I'd love to know.

According to Wrong Ways' video, Begode ET Max, Begode Extreme, Inmotion V13, Veteran Lynx. There may be others.

[alcatraz]

A smart bms is basically just useful to display the individual voltages without having to take the battery packs apart.

Kind of like a spare wheel on a car. If you know how to use it, it can help you. If you don't know how to use it it isn't that important to you. Ideally we try not to have to use it but the longer you drive, the greater the chance you could find it useful. 

Cells are matched at the factory so they behave very similarly at first. No bms needed basically. Then as they age they diverge more and more. The older they get the more monitoring and management you need. This is unavoidable. Then for impacts and cell damage, those are situations when you can see a sudden change in the readings.

The most important is the overcharge protection and all bms have that. If you have a smart bms you can confirm that the protection works (although noone does). A dumb bms with a faulty overcharge protection will also charge to 100% but be a fire hazard. It's extremely unusual for that to break. Most bms problems are balancing malfunctions or blown fuses. 

So for peace of mind, seeing that the voltages are stable, and all cells are within normal range. It gives the owner confirmation that at that point in time, the cells are safe.

Also, REAL smart bms aren't supplied in the wheels because we don't have access to all settings yet, if any really. A smart bms allows the user to set temperature, voltage, current ranges. Set balancing at 80% charge etc. Initiate manual balancing. Activare storage mode etc. So lets say they getting "smarter" but they aren't quite like the big boys'.

[alcatraz]

10 hours ago, Samantha_C said:

Or does it just tell you something is wrong (i.e. unbalanced cells) but you gotta fix it with your wits?

That's it. It tells you there's something wrong with the cells or the cell management.

Would you rather know or not?

You still have to open the app and have a look. If you don't then you're basically just using it as a "dumb bms": waiting for the wheel to complain first.

[alcatraz]

Some people simply don't trust the wheel software with their house/apartment. When you wait for the wheel to complain you're trusting the software to alert you.

Edited July 18 by alcatraz

[alcatraz]

I don't trust it but I open my packs once in a while (once every 1-2 years) and measure the cells. If they're balanced I'll reset the clock. Done.

[alcatraz]

Opening the packs and doing a visual inspection has certain advantages. You could catch heat spots, melted heatshrink or cables, or corrosion, contamination, water ingress. Until a problem starts to affect the cell voltages a smart bms is unaware of it and can't alert you of it.

[Samantha_C]

 

2 hours ago, alcatraz said:

A smart bms is basically just useful to display the individual voltages without having to take the battery packs apart.

Kind of like a spare wheel on a car. If you know how to use it, it can help you. If you don't know how to use it it isn't that important to you. Ideally we try not to have to use it but the longer you drive, the greater the chance you could find it useful. 

Cells are matched at the factory so they behave very similarly at first. No bms needed basically. Then as they age they diverge more and more. The older they get the more monitoring and management you need. This is unavoidable. Then for impacts and cell damage, those are situations when you can see a sudden change in the readings.

The most important is the overcharge protection and all bms have that. If you have a smart bms you can confirm that the protection works (although noone does). A dumb bms with a faulty overcharge protection will also charge to 100% but be a fire hazard. It's extremely unusual for that to break. Most bms problems are balancing malfunctions or blown fuses. 

So for peace of mind, seeing that the voltages are stable, and all cells are within normal range. It gives the owner confirmation that at that point in time, the cells are safe.

Also, REAL smart bms aren't supplied in the wheels because we don't have access to all settings yet, if any really. A smart bms allows the user to set temperature, voltage, current ranges. Set balancing at 80% charge etc. Initiate manual balancing. Activare storage mode etc. So lets say they getting "smarter" but they aren't quite like the big boys'.

Thanks alcatraz, for all the tips and advice! 

You are much more hands-on with your wheel and more knowledgeable than I am. I haven't peeked inside my battery packs nor conducted a manual voltage check, but I occasionally use EUCworld to check the volts and range. I've gone as far as replacing my tyre and shock, but I'd rather leave the battery alone if I can help it because I don't want to risk breaking a watertight seal. Also, I wouldn't know what to do with damaged batteries anyway, other than replacing them, I guess.

Do I trust my wheel? Lol.

It's like asking if I trust my boyfriend. He's reliable so far, but I wouldn't know if he intends to cheat on me. A smart BMS sounds like a threat detection system, like a smartwatch with a heart rate monitor, or a spy app installed on your boyfriend's phone. Maybe some people feel at peace monitoring their heart rate constantly, but that is too neurotic for me. I'd rather wait till I have symptoms before seeing my doctor. I guess the same applies to my wheel. Too much checking and monitoring ruins the experience. 

Maybe I'm weird that way. 

Edited July 18 by Samantha_C

[Samantha_C]

2 hours ago, rcgldr said:

According to Wrong Ways' video, Begode ET Max, Begode Extreme, Inmotion V13, Veteran Lynx. There may be others.

Thanks! Although I heard even the ET Max had trouble charging to full (in Dawn Champion's videos)... 

[alcatraz]

Your analogy was way better than my spare tire analogy.

[Seba]

22 hours ago, rcgldr said:

According to Wrong Ways' video, Begode ET Max, Begode Extreme, Inmotion V13, Veteran Lynx. There may be others.

With all respect to Adam, he's not a technical guy. He probably though of active balancing as opposite to passive top balancing. Actually, none of wheel has BMS with active balancing. Active balancing works by redistributing charge from cell group that has more charge to another that has less charge. So during active balancing, cell groups may be discharged and charged as well (of course without charger connected). Passive balancing only discharges more charged cell groups using bleed resistors, to equalize their voltage with other groups. Top balancing happens only when the cell group goes over some fixed voltage, say,4.22V or similar. This only happens when the battery is full, so usually needs charger to be connected for top balancing to happen. What people are calling "active balancig" is actually a passive balancing that may happen also at lower voltage levels (thus also lower charge levels). This type of passive balancing may also happen without charger connected.

[RagingGrandpa]

15 hours ago, Seba said:

With all respect to Adam, he's not a technical guy. He probably though of active balancing as opposite to passive top balancing. Actually, none of wheel has BMS with active balancing.

Exactly.

On 7/18/2024 at 3:22 AM, rcgldr said:

According to Wrong Ways' video [certain models have active cell balancing]

He's Wrong.
It's in his name tho... so we're not supposed to complain about it. 
 

On 7/17/2024 at 4:48 PM, Samantha_C said:

does the smart BMS actually prevents and fixes degradation

Great question!
It does not.

On 7/17/2024 at 4:48 PM, Samantha_C said:

I heard the battery might blow up in my face ... without a smart BMS

Li-ion cell hazards are always present, even when used with Bluetooth BMS. 
Never get your batteries wet. 
Stop using the EUC and store it outdoors if you experience any abnormalities with charging. 
Even 'dumb' BMS include protections from over- and under-voltage. The protection is: it stops the recharging process. So that's your first sign of trouble.

Bluetooth BMS is lovely because you can inspect cell voltages at any time, and so you don't have to attempt recharging the battery to determine its health. But otherwise, it does the same things as traditional BMS.

[Punxatawneyjoe]

15 hours ago, Seba said:

also happen without charger connected.

Thanks for the detailed explanation and the reminder to renew my premium account with you. I really appreciate how helpful you are to the community and that you have an amazing product that is well worth the money.

[kintips]

On 7/18/2024 at 1:32 AM, alcatraz said:

I don't trust it but I open my packs once in a while (once every 1-2 years) and measure the cells. If they're balanced I'll reset the clock. Done.

Hey can you write how to do that? Or make a video (since you take you open your pack every year to check). I would love to learn how to do it. It would save so many v8f v5f wheels from unbalanced cells. I sold all my inmotion wheels because of that. 

[rcgldr]

2 hours ago, kintips said:

Hey can you write how to do that? Or make a video (since you take you open your pack every year to check). I would love to learn how to do it. It would save so many v8f v5f wheels from unbalanced cells. I sold all my inmotion wheels because of that. 

You have to be able to get to the BMS. You'll need some type of resistor (around 100 ohm) connected to probes to drain the higher voltage cells groups. On V5F | V8F BMS, you have + and -, and 19 pads labeled 1 to 19 (maybe with a prefix) for a total of 21 pads. Test the voltage first for + or - to pad 1 or 19 and between pads to see which pair of pads correspond to 1 cell group versus multiple cell groups, which can be up to 19 cell groups.

Edited July 20 by rcgldr

[alcatraz]

3 hours ago, kintips said:

Hey can you write how to do that? Or make a video (since you take you open your pack every year to check). I would love to learn how to do it. It would save so many v8f v5f wheels from unbalanced cells. I sold all my inmotion wheels because of that. 

You need to get to the bms pcb, expose the terminals that connect to the nickel between the cell groups. Take out a multimeter and in VDC mode measure between each terminal. A 100.8v wheel has 24 groups (4.2v x N = wheel voltage) so make sure you have 24 different probe location readings that are all within normal range. Ideally perfectly balanced = same value across all 24 measurements. 

My packs are just heatshrinked and taped into the wheel chassi. I made an incision in the heatshrink and carefully removed it. I then put it back and tape the gap shut. My packs use two layers of heatshrink in two directions.

On some of my wheels I've attached balancing wires meaning the probe points are available for measurement outside the pack. It takes a bit more work but it certainly is doable and wise IMO for a wheel you intend to keep.

As I mentioned above. Most wheels show no imbalance because the cells are still quite new and the bms is working normally. When the wheel ages the cells REALLY start to put pressure on the bms's systems. It's a good idea to see if it all balanced out or if perhaps you need to do something like leave it on the charger for longer than you used to, or manually balance once every couple of months.

Something as simple as that could save that wheel from the landfill or fire department.

Edited July 20 by alcatraz

[kintips]

6 hours ago, alcatraz said:

You need to get to the bms pcb, expose the terminals that connect to the nickel between the cell groups. Take out a multimeter and in VDC mode measure between each terminal. A 100.8v wheel has 24 groups (4.2v x N = wheel voltage) so make sure you have 24 different probe location readings that are all within normal range. Ideally perfectly balanced = same value across all 24 measurements. 

My packs are just heatshrinked and taped into the wheel chassi. I made an incision in the heatshrink and carefully removed it. I then put it back and tape the gap shut. My packs use two layers of heatshrink in two directions.

On some of my wheels I've attached balancing wires meaning the probe points are available for measurement outside the pack. It takes a bit more work but it certainly is doable and wise IMO for a wheel you intend to keep.

As I mentioned above. Most wheels show no imbalance because the cells are still quite new and the bms is working normally. When the wheel ages the cells REALLY start to put pressure on the bms's systems. It's a good idea to see if it all balanced out or if perhaps you need to do something like leave it on the charger for longer than you used to, or manually balance once every couple of months.

Something as simple as that could save that wheel from the landfill or fire department.

Thank you for the information. Yes if they can keep the cells balanced we would not have these issues. And these batteries are crazy expensive they wanted $600usd to replace my v8f battery thats almost more than the euc. 

[rcgldr]

If you can find one, you can buy a 2023 V8S for $639 to $699, depending on dealer and discount, but it doesn't have the side LEDs and the finish is matte instead of gloss.