Each cell has a capacitor (C) assigned to it and a two-way (solid state) switch. The switch positions (Q) are dictated by an embedded controller which has input from voltage sensors:

In one switch position charge is taken from a cell into its capacitor. The ladder of switches is then changed to connect that capacitor to the cell with the lowest voltage. Typical current flow is 2-5A, dependent on the ΔV between the cells. There are algorithms discussed in various sites online.

When ΔV reaches a minimum level set by the user, the balancing operation should stop. That's one of the features which users of the Neey active balancer say isn't happening.

These 'stand-alone' active balancers are equipped with WiFi. The only control settings available must be set by the App released by the manufacturer. There is also no other way to monitor what is happening.

Compare that with an Active BMS, like the one manufacture by JK. It's a fully-fledged BMS which has inbuilt active balancing. Its operation is discussed here on the blog from Off-Grid Garage.

Please correct me if I am wrong, but I assume that an active balancer moves charge from higher voltage cells to lower voltage ones, until all cells are at approximately the same voltage.

If so, does the balancer do this by looking at the voltage of each cell and then deciding where to move the charge from A to B, or is there individual balancers between each pair of adjacent cells, that moves charge from the higher voltage cell to the lower voltage one?

I'm not anti-Chinese companies or China. But they've effectively cornered this market whilst the rest of us were enjoying lower energy prices.

So either we prevail upon these manufacturers to 'get things right'...

... or we put the work in and do it ourselves.

If it's going to be the latter, then we need a shout-out to some enterprising engineers who'd like to develop a new product.... which is the message I feel can be instigated from within this forum.

We need to pass the word around. Age doesn't matter. I'm pretty sure there would be good positive technical encouragement from members here, whether the 'applicant' was still at school or 'considering early retirement'. 🙂 

From past experience I have found that many electronic devices manufactured by Chinese companies are poorly designed and use components with specifications lower than would normally be acceptable.

For this reason I try, wherever possible, to avoid such equipment. Whilst re-branding of equipment may be permitted, I feel that the nameplate should also state the original manufacturer.

My investigation started from this thread where we noted that the Off-Grid Garage YT videos suggested deficiencies in the balancing operation inbuilt to the Seplos BMS. (Note that video link takes you to the 1st of 5 videos covering two Mason Box builds).

I also noted the comments from @simonstengineer here where he described the preference for active balancing.

The Off Grid Garage did indeed add a separate Active Balancer unit to overcome imbalance issues during construction of the Mason Box. He used two types imported from China, one generic, sold under several names, and the other marketed as Neey.

So now let me draw your attention to this discussion on the DIY Solar Forum about the Neey unit. The correspondents are debating the inability of the Neey unit to switch on balancing at the prescribed voltage and switch off again at another set-point. That seems quite a fundamental requirement for a product sold as a balancer 🤔 

As stated yesterday, I've corresponded with the manufacturer of the generic active balancers offered for sale on ebay and AliExpress. I asked for details of the on-board pads/links which suggest that their design can be turned on/off by an external signal.

However, they've informed me overnight that the 'enable' feature is inoperable. 😣 

This whole solar/storage market seems beset by products which have been sold for a considerable time, but don't appear to work.

Consequently, if manufacturers (in the Far East) won't or can't complete their design to a standard which includes full operational capability, then anything we attempt here which uses these products seems doomed to fail. That has serious implications for how we might resolve the energy-crisis.

If there are any other electronics/software/micro-controller engineers are reading this, perhaps you could make yourselves known. I can now identify a number of essential products which self-builders of energy products require, but lack the required functionality.

1. BMS with active balancing
2. Off-grid storage inverter which isn't based on a 10-year-old design using lead-acid batteries
3. State of Charge (SoC) system with better than 10% accuracy

Yes, all these are available via proprietary routes from the likes of Victron (Netherlands) and Batrium (Australia). But their approach relies on them supplying all the kit and linking it via their software.

That strategy gives them a secure share of the market. But just try getting it to assimilate incoming data from your Energy Supplier, your Smart Meter or the electricity grid! Unless/until they incorporate such features into their software, you're stymied.

I think you still need a DC fuse, and also a mechanical disconnect switch.

https://www.aliexpress.com/item/1005003104573871.html?pdp_npi=2%40dis%21GBP%21%EF%BF%A160.06%21%EF%BF%A142.64%21%21%21%21%21%400b0a3bb916677520992023667e2aa2%2112000030977333522%21btf&_t=pvid:d8e9c100-e3be-4960-a019-3eed1a718ae3&afTraceInfo=1005003104573871__pc__pcBridgePPC__xxxxxx__1667752099&spm=a2g0o.ppclist.product.mainProduct

However, can I suggest that you don't buy without 'checking in' again here. I've just filed a technical query with the company who I believe actually manufactures that unit. I'll explain more once I receive a response.

I've watched the same Off Grid Garage video re the Seplos BMS' ineffective balancing feature.

My hope is that the lack of significant BMS balancing won't have have much of a real-life impact if I do an initial top balance of the cells and generally only pull 7-10kWh daily from their supposed 14kWh capacity.

I think I remember Will from DIY Solar suggesting in one of his videos that an active balancer is unlikely to be required in a situation such as mine...

Worst case an active balancer can be added at a future date.

Posted by: @transparent

In my experience, the final expenditure on tools, cabling, connectors, fuses, trips and enclosures cannot be described as 'smaller purchases' 🤣 

Additional expenditure currently at £80 🙃 (wheeled dolly to sit battery on, torque wrench, adjustable DC power supply).

I suggest @korwraith and @batalto might want to see what's being said about the Seplos BMS units in their Mason boxes.

...approx £3380 so far with some smaller purchases of tools/cabling/misc. to follow.

In my experience, the final expenditure on tools, cabling, connectors, fuses, trips and enclosures cannot be described as 'smaller purchases' 🤣 

In fact it's very much the case that what you do by way of the interconnections and safety devices is precisely what we'd appreciate you sharing here on the forum.

Anyone can buy a pallet of hardware to satisfy their energy requirements. It's how you then implement it which everyone else wants to hear about!   ... preferably with photos.