failed EVE LF280 after 150 cycle!

[Alexander B]

We purchased 100 cells of EVE and test all of them for capacity! All are above 280Ah , good shape and no major scratch, all relatively new and their production date in first quarter of 2023 ! their named A- grad! ( cells not directly bought from factory or kept more than 3 month without company testing results catagorized in A- ) we first top balanced cell in 3.65V and kept them parallel for a while! but after assembling them in battery packs and used them in low speed traction application just after about 150 working cycles dramatically cells capacity and voltage differ from each other!
one of the cells in 4S pack reach to 3.65 V during charging while other 3 cells are only 3.35V, from capacity point of view three cells have 75% capacity after charging is interrupted by bms because of over voltage of the first cell! while one cells reach its 100% we test again all cells individually all of them still have capacity above 280Ah !

but cells suffer from different internal discharge rate I think! although their internal resistance seems to be close to each other atleast with method of measurement by a multimeter equipped with internal resistance measuring function!

so it no matter how much a cell can keep its initial capacity after cycling but cells unbalancing after cycling is the most problem of the lithium battery issues ! even they're working for multiple thousand of cycle but after a hundred cycles the capacity of the battery packs limited to the lowest battery cell soc!
anyone here has same experience, what do you recommend?

This has nothing to do with the battery,you should rebalance them, or add an active balancer

 

[OffGridForGood]

The BMS won't know the difference but the packs under load will have different resistance in the cables, thus the problem of imbalance as a result.

perhaps - we can't actually know, until the size, length, material properties of the cell bus bars and the pack cables are all known. With the packs close together and careful selection of the pack 1 to pack 2 to pack 3 cables - there could be negligable difference in resistance. That would be a design issue for the OP's team to determine.
We all agree a single 12s pack is the best solution, what we are trying to find in a work-around is the OP's desire for three separate drop in packs to suit his customers' ability to do the swap without a tech from the factory.