Hi PosplayR and thank you for sharing so much. Since you seem so knowledgable on this would you like to comment on how important would it be to get matched cells if I'm buying lets say 200 cells to do banks of 16, 32 and 48 cells at 48v the way you've done them for solar house storage? Couldnt we just organize them by capacity in groups of similar capacity and also min-max to further optimize? I understand some of my banks will be higher and other's lower capacity but are we talking about a 10% max in capacity? some prices for matched cells seem to cost much more than that. Trying to see the big picture here. I sell solar panels and I have many inqueries for battery banks and I would like to proceed in an efficient manner; my clients wouldn't care about a 10% capacity difference when switching from lead, and I can just charge according to the real capacity, there are always bargain hunters who will take the lower bank at a discount. I would appreciate your advice, thanks in advance.
I very highly recommend that you look at larger capacity cells, and use fewer than 200. You are introducing a lot more points of failure, bus bars, wires, fuses, multiple BMS, etc. You can buy 1000Ah cells, so I would start with that. 16s or even 16s2p of 1000Ah is going to be a whole lot better than 5x as many 200Ah cells.
As a simple comparison between matched and unmatched cells. I bought 12 100Ah cells, though official channels not alixxx. Yes, they were expensive. They all tested at 115-117Ah. The IR was nearly exactly the same as well. No swelling. Those same cells, grade B from alixxx, could be between 80-100Ah, with very different IR, and varying degrees of swelling. I didn't test the self discharge rate, but that is likely the same across my cells as well. With Grade B cells, if they are within 20% of rated capacity, they will still sell them as that capacity. With Grade A, the factory specs include a margin, that the cells will be over the rated capacity.
Min-Max matching as PosplayR describes will maximize the capacity of the batteries built with Grade B cells. You won't get 100Ah per cell, because some cells are less than that. But, you will get more than 80Ah. Lets say you get 90Ah. I have 115Ah with Grade A cells.
Min-Max matching will do nothing to ensure that the cells stay in balance. If/When that happens, capacity of the battery will drop. There will be no damage, and you can top balance again to get that capacity back. You can add active balancers to continually balance the cells and prevent needing to top balance again later. Otherwise, unmatched grade B cells will likely go out of balance. However, matched and balanced grade A cells, properly installed with good connections, equal length wires etc., can go years without any balancing needed. Not even the passive balancing that BMS's include.
Also, the life expectancy of grade B cells is not known. Grade A cells are known to last (barring something happening to damage them) for 10-20 years.
Not sure if that answers your question. In summary, there isn't going to be cell damage if you connect unmatched cells, but they may require more maintenance and balancing in the future. They also may prove unreliable in the long term. That is an unknown, and you can read many posts about people that are unhappy with their grade B cells, but also as many that were very pleased.
I will respond separately RE: 2p16s vs 16s2p