BMS AE-LMD17 REV A1
Seen a 24 cell capacitive balancer for less than $200. 60 amp discharge, Capacitive is a lot more efficient than resistive, it basically uses a capacitor between adjacent cells and mosfets to shuttle charge from higher potential to lower potential:
and it should be able to operate while the vehicle is driven or charging (or just sitting, but that might lead to excessive discharge over time, lotsa leaky caps). IIRC it is like %50 efficient, depending on the distribution of imbalance of course. If you could alternate weaker cells and stronger cells it would work very well
but the cells on the end still don't get refreshed at the same rate.
There should be an inductive version, that takes pack voltage to bring up the low cells too.