Hello! Once again, I'm playing with my Uh 4S sodium ion battery and there have been a couple of changes on here. One thing I've done is put these little LEDs with resistors onto or across the balancing resistors on these two Bms's because I wanted to see when the Uh passive balancing circuits came on all controlled of course by this Byd chip here. But the other thing that you probably saw on the top here is this: active balancer. This is a flying capacitor active balancer and this one is branded 100 Balance.

Now this active balancer is on and running. You can probably see that from the little green light there. Let's have a little look at what it says on here: Active Balance Module uh, Lithium Ion or Life Po 4 strings 4S So it's got a five way connector in this rather fetching matching blue color and it says Uh current Max 1 amp and then Dongan balanced Manage Technology Company Limited Now the reason I bought Uh, this active balancer and a few more Besides pricing error on these um was because there are two types that they sell. Uh, this one which is an active balance module and this one which is a smart active balance module again 4S Uh With the five-way cable and the fact that this cable fits both balancers both the smart one and the Noto smart one Uh, makes it very easy to switch between these.

Now just very briefly. watch this I run the app and for a fraction of a second it's red and then turns blue and I suspect that the reason for that is that you can also get these branded as uh Dar or daily um and also something High BMS I Think it is, but that uses the daily app and it looks to me like um The Daily app has been uh, what's the word skinned with this blue color for 100 balance? it's all part of one Ecos system. Now just briefly before I take these two devices apart and that that's really what this whole video is about. It's about these two, uh, different types of active balancer.

Um, this one that I bought first is slightly different. It doesn't have the plus and minus symbols all the other ones I bought do and also the older one says Max one amp whereas all the others say 1 amp. And of course Max 1 amp is much more accurate because as the difference between cell voltages decreases, so the transfer current of these capacitor active B balancers also decreases. So current 1 amp? Yeah, not so much.

It's Max 1 amp and you probably won't see 1 amp uh unless you have. And of course this is what sodium ion cells are good for. Unless you have a very large dist difference between the voltage of one cell and another cell, right? Let's take apart one of the not smart active balancers. uh, just a well I hesitate to use the word dumb but non-int ENT uh capacitor active Balancer Let's get these screws out and inside We have this uh, some mosfets and a couple of other chips and we'll go through those in some detail.

and then on the top, there are seven of these. um, uh, what are they Electrolytic capacitors? 10vt th000 microfarads and they've all been gunked with silicon sealant and I think I know why because when you have a large difference in voltage between two cells, uh, this thing is pushing a large current and these capacitors actually squeal. they make a high frequency, uh, squealing noise and I assume that this sealant is to damp them down a little bit. Uh, now there's one tiny component on the top of this board.

It's just in there. it's a little green LED and in the lid there's a light pipe which takes it up to this, uh, little plastic dot which you see on the top right? I'm going to get some more of these capacitor active balancers. So here are a few that I've bought recently. Um, this is actually a 3s.

It's got four wires. Uh, bought in error. It's very easy on AliExpress to pick the wrong item. so then I had to reorder the four S which is this one.

It has five wires and there are a couple of others here I'll unbag them. Um, this one is probably most similar to The 100 balance Unit Seven Capacitors uh, four dual mosfets, a mosfet driver, and a little well I say oscillator chip. but I Got a feeling it might be a microcontroller. We'll come back to that.

Uh, this one has everything on the top surface, but essentially it's the same circuit. the same layout. Well, almost. Uh, this one looks like it's got more mosfets, but that's I think because these are single mosfets, there are eight of these eight pin packages here where all the others have four.

Um, there's the mosfet driver chip and there's this little six pin so 23. And the reason I think that's a microcontroller and not a dedicated chip. um is because it's got these four pads which I believe are for programming that microcontroller. Now, this microcontroller is interesting.

Let's have a closer look at it. so it is very tiny. Uh, it's a So 23 six pin, but you might be able to see on there. It has a branding of Fmd which I believe is Fremont Micro Devices and the code is B30 khh Now I Can't find anything on this chip online, but um the there are microcontrollers and there is specifically a six pin So 23 microcontroller in Fremont Micro Devices lineup These four pads the one with the hole in is ground.

There's also VCC and I believe clock and data. Um, look like they're for programming this device in circuit or in system programming. Uh, so that's why I believe this is a microcontroller and it's the same microcontroller on all these boards except this one which is the 100 Balance one and I'll show you what that's got instead. Now, hopefully this Uh has all the markings intact.

So there we are. We have an ICM 7555. Well, that's a 555 timer Seos flavor. We also have this one an EG 2104.

Well, that's I think compatible with the IR 2104 which is a mosfet driver. And then we have these four dual mosfets and you can sort of see from the circuit that they're dual mosfets because you've got two drains up at the top. Here you've got two Uh sources down the bottom where the thick tracks go to, and there are two gates which are obviously on this bottom, right hand corner and two pins along. and these are AGM 31 1 MN It's just two side by side mosfets in an eight pin.

uh, soy. I Believe that is and I believe that the way these work is simply that you've got an oscillator. I Think this microcontroller does very little more than just provide an oscillator output which uh feeds into the mosfet driver. Now, this has high and low driver outputs and it is possible to follow these tracks.

I Believe these two lines here which run around here and then go to alternate Gates of the six mosfets it is. So what what they're doing is they're switching on first the leftand three mosfets and then turning those off and turning on the right hand three mosfets. and I think the idea here is that these this is a 3s Uh active balancer. These three capacitors hold the equivalent voltage or a copy of the voltage Vol AG of the three cells.

and then they put these two capacitors first across uh, the left hand side and then they move them to the right hand side and they're just moving them backwards and forwards to equalize the charge between Uh a cell and its neighbor. And of course, by doing it on all the cells. Eventually, it equalizes all the charge Uh charges or voltages on the cells to be the same. Now, of course, Um, as the Uh difference in cell voltage reduces, the balancing current reduces.

so it's a sort of uh, classic exponential decay kind of curve. Now in the spec for the 100 balance unit, it says that it turns on and the green light comes on. Um when now I Think it's when any cell gets to 3.1 volts and and it turns off when now I Don't know whether it's all cells or a cell or the lowest cell or the highest cell. Uh gets down to 3 volts.

so there's a little bit of hysteresis, but there is a mechanism for turning this thing off and then it's Uh current. Its usage current goes down to tens of microv volts. it's very low. Now on this one we have the the battery type is NCM Lfp and Lto and Lto is interesting because this is Lithium Titanate and I Believe those cells only go up to 2.4 volts.

So this one works to balance very low voltage cells whereas its counterpart this one doesn't because if you look on the back of here it only says NCM and Lfp and it says that it's operating Voltag is from 2.7 volts to 4.5 Now, if an Lto has a maximum voltage of 2 .4 this thing would never function. So this one has been tweaked to operate at a lower voltage and to cut off at a lower voltage than this one. And the only way that I can see that they've achieved that is by using one some part of the microcontroller, possibly an analog input pin to monitor a cell voltage or perhaps the pack voltage or some sort of voltage and go into shutdown on this one at a at a much lower voltage which includes Lto, and on this one at 2.7 volts, which of course doesn't include Lto. And that's possibly what the microcontroller is doing.

Now the 100 balance Uh, blue one has this 7555 and you'll see that pin Four, which is the reset pin is connected to something. It's connected to that diode. Uh, so possibly they're using the reset pin of the 555 measuring a voltage somewhere. and perhaps the reset pin of a 555 has a threshold with some hysteresis I can't remember I'd have to look at the data sheet and so this one they've set it so that it triggers at this.

turn on at 3.1 turn off at 3.0 volts. but that wouldn't be adjustable. that wouldn't be programmable on this unit. So this is fixed at that threshold voltage.

And here's a manual. It's a single sheet of paper that came with the Uh 100 balance uh, dumb active balancer and right at the bottom it says uh, the balance is turned on when the first series voltage is greater than 3.1 plus or minus .1 The active balancer. Uh oh, hang on. The balance is turned off when the first series voltage.

Oh, I Wonder whether that means the voltage of the first cell that's possible is less than 3.0 plus or minus .1 right? Let's tidy all this stuff away and take a look inside. The Smart active balancer.