syseng68k:
The focus of the issue!
...difficult to ensure that individual cells within the pack match in terms of charge / discharge characteristics. If there is mismatch, either in capacity or self discharge, some cells discharge faster and will take differing times to recharge. Over time, some cells become overcharged, while others never reach full capacity. This is exacerbated by high charge current and discharge loads, in relation to battery capacity.
Indeed requiring a quite "complex" management. (algorithms)
The best way to solve this is to have separate monitor and charge circuits for each individual cell, but his becomes expensive for large groups of cells. Users like telcos do monitor in this way to maximise battery life, but typically in groups of 3 or 6 cells.
and why not to separate better each cell from adjacent? The weight could be similar and the volume would compensate for the better safety under higher temp cell operation, an usual condition.
On a 28v system, there are typically 14 cells in series,...
8 cells of 3,7 V ea.
Yuasa are a world class manufacturer and my guess is that there is a problem with the charging / monitoring electronics, or cooling. That or the batteries are being driven too close to their design limit to save weight...