Ordered a 280ah SFK v3 kit.

[Alkaline]

Ok, I'll admit I have a bit of a bias. I have several of these, and had decided they were a good thing to add to my Overkill 8S BMS, and to have spares.. I was testing the system over a few weeks, including in cold temps. Then one day I opened the battery box to find that the cells were WAY out of balance. That is to say, one (or maybe two?) cells were dropping dangerously low, below 2.8V with the rest above 3.2V. Then I found that about half of the caps on the Hultec 8S capacitor balancer were rapidly approaching 100°C, too hot to touch. Yikes! I pulled the whole thing. That board had clearly failed and was taking my battery (and maybe my house) with it. Suffice it to say, I would *NEVER* trust these cheap little boards to be plugged into my battery without me checking multiple times per day.

So I am NOT a fan of these $2.99 active balancers (cost of parts, not what we pay) because it almost wrecked my battery. Besides that, there were two other things I realized, back when I thought they might be good:

1. Balancing all the time is just a bad idea. If you have top-balanced cells, the balancer will work like hell to bottom balance them when the cells are low, and then work like hell to top-balance them the next time you charge. Meaning, it will be meaninglessly moving energy all day long as you cycle. Since those moves are clearly less than 100% efficient, you are losing energy from your battery. Moreover, it will defeat your careful top-balance the first time you get the cells towards the bottom end of the discharge curve. This was the crux of what Off-Grid Garage showed, if anyone wants to go watch his videos.
2. They will virtually never balance at a meaningful current. The "2A" rating is assuming that there is a *HUGE* misbalance between cells. I measured less than1A when I intentionally created a 0.8V imbalance between two adjacent cells (2.5V and 3.3V). For smaller differences, the amount of current is proportionally smaller. This means that the passive balancing in something like the JBD/Overkill BMS is probably more effective.

So, I'm not judging them harshly for no reason. To each his own.

Do you have pics of your setup? I don't understand what you are saying is even possible, the active balanace is actually pretty stupid as in it has no idea which cell is high or low, it simply gets the voltage form all 8 cells averages them out inside the capacitors and then makes it available. Any cells whose voltage is above the capacitor voltage, it will send voltage to the caps, any cells voltage who is below the capacitor will get voltage from the capacitors.

This thing is essentially a parrallel bus bar, so I would like to see how you set it up. ALSO are you sure you were using the ones with the red/silver caps or were yo uusing the ones that just burn off power, like the 1.2 AMPS that look like they have squares?

 

[Alkaline]

These things do get HOT AF: https://www.amazon.com/Inductive-Equalizer-Balancer-Balancing-Protection/dp/B09MSDLD2Q

But these do not, I had 3 of them and left them plugged in whole time: https://www.amazon.com/Equalizer-Balancer-Titanate-Transfer-Capacitor/dp/B096NNRSMV

My 8s AB worked great and were the only thing keeping my 8s xuba 280s in check. They also worked well with the Basen.

The only ones that I took off were the 8s 280K from Luyuan as I could not tell if I needed them.

So yeah, in my book the active balancer with your BMS balancer works well, I checked with my xiaoxing app and they were dead on usually 3.445 all across the board.

NOTE: 1 thing I did notice, when under load the xuba 8s pack would cause all types of ruckus, as 2 cells would be like 3.05v vs the others that were like 3.21v under like a 70 amp load (and no this was not a connection Issue I sanded the crap out of the terminal and made is smooth as glass, i'm taking 3000 gritt smooth, no difference the cell was just bad). I think this caused the unbalance issue because if you kept the load for long it would cause an imbalance as the AB would keep running.

So if you have grade B (my xuba & basen) there is a potential for you to get an imbalancement if you draw a large amount of power from your cells and there voltages drop.

That being said, once you charged them back up it would balance them back up again. Usually with in 2-3 hours all cells perfectly balanced.

 

[Nobodybusiness]

dexter seems to move mountains for his customers

He does indeed..

 

[Horsefly]

Do you have pics of your setup? I don't understand what you are saying is even possible, the active balanace is actually pretty stupid as in it has no idea which cell is high or low, it simply gets the voltage form all 8 cells averages them out inside the capacitors and then makes it available.

I don't know what kind of "pics" would tell you anything. If you mean a schematic, it wires up in parallel with the BMS, one-for-one each wire connecting with the balance leads. Doesn't seem possible? Based on what? I'm an EE, and I am certain this is possible given that it has components - that can fail - between the positive and negative leads on each cell.

it simply gets the voltage form all 8 cells averages them out inside the capacitors and then makes it available. Any cells whose voltage is above the capacitor voltage, it will send voltage to the caps, any cells voltage who is below the capacitor will get voltage from the capacitors.

I'm not sure I agree with you on how it works. From what I've seen, it doesn't do anything with an average. It compares each cells to the next. If the first cell is higher than the second cell, it charges a capacitor, and on the next cycle it discharges that capacitor into the second cell. This repeats on down the line. But I guess it doesn't matter that much: It works until it doesn't.

These things do get HOT AF: https://www.amazon.com/Inductive-Equalizer-Balancer-Balancing-Protection/dp/B09MSDLD2Q

But these do not, I had 3 of them and left them plugged in whole time: https://www.amazon.com/Equalizer-Balancer-Titanate-Transfer-Capacitor/dp/B096NNRSMV

The first one is the inductor-based balancer, and my testing of it in 2020 showed that it effectively was junk. Didn't do any balancing at all. The second one is what I had. I still have a spare, but I'm not going to use it.

So if you have grade B (my xuba & basen) there is a potential for you to get an imbalancement if you draw a large amount of power from your cells and there voltages drop.

When mine failed, I was doing temperature tests and logging of my heated battery box. Aside from the heater that was on periodically (1.2A drawn when on) there was no charging and no other loads.

 

[Alkaline]

The AB with the red/silver does not go cell by cell it literally draws power from all connected cells and charges the up the caps. The caps have the average voltage of the cells. I confirmed this and that video I showed shows the same thing.

I think you have a different Ab, so I asked for the pics this heltec style one doesn't do any comparing at all or goes cell by cell. I tested with clamp its sending voltages to 4-5 cells simultaneously. The speed of the balancing depends entirely on the voltage difference, if you have very little difference it does nothing.

Its also not limited to 5 amps when I was building my pack before I top balanced the cells I saw as much as 7 amps being moved around. Andy from off grid garage showed this.

I think people are blaming the AB for the IR imbalance in the cells where by when underload if the cells have different voltages than the AB makes the situation worse by trying to balance a cell while it is being discharged. So potentially you can have a situation where it is drawing power form other cells to raise the voltage of the weak cell where by making all the other cells become unbalanced.

So when you charge them up the weak cell is going to be fully charged first while the rest will not be charged... BUT on the same token since it is a an AB it is going to also do this in reverse where it will take voltage from the fully charged cell and send it to the lower cells.

So I guess you could say its Good and Bad.

Ideally the AB would only work on voltages 3.3 or higher ONLY when it is IDLE, and not when it is underload.

 

[Horsefly]

I think you have a different Ab, so I asked for the pics this heltec style one doesn't do any comparing at all or goes cell by cell. I tested with clamp its sending voltages to 4-5 cells simultaneously. The speed of the balancing depends entirely on the voltage difference, if you have very little difference it does nothing.

No, I don't have a different type. It was the same one. My description of how I thought it worked was based on what other people have posted here. But if you have actually measured currents I'll take your word on it. I threw the thing away when I pulled it out. I know it had - besides the capacitors - what I would expect were some FET-based comparator chips. I would think that a failure in any one or more of those chips could cause the failure I witnessed.

Ideally the AB would only work on voltages 3.3 or higher ONLY when it is IDLE, and not when it is underload.

That I can say for sure is not how this capacitor-based Heltec balancer works. I know in some early experiments I did I could see it doing balancing when one cell was at 2.9V and the rest were at 3.1V. Hence my statement that it will attempt to do bottom balancing even if you want a top balanced battery. I also don't think the balancer has any real way to know when the battery is under load or not. It's only measuring voltages of the cells.

 

[Alkaline]

Yeaht he AB does not know if its under load or not. Not sure what happened to yours, but it worked for me, I know they have different versions and despite looking a like they do function differently for starting/ending voltages.