I know what it does, but how? Does it allow all the cells to charge fully and then when and if one of them reaches 4.2v it starts dumping current or does it attempt to keep all the cells at the same level as they charge?
Most typical
BMS units used in eBike batteries use the "Top balance" technique which only begins balancing the cells when the battery is almost fully charged and any one of the individual cells reaches ~4.2V
(~3.65V for LiFePO4 cells).
As the first cell reaches its maximum target voltage of ~4.2V, a resistance is automatically placed in parallel with the individual cell to bleed off excess current and prevent the cell from being overcharged.
Unfortunately, due to size limitations and limited heat dissipation, the resistance can only absorb a very low current
(usually around 85mA) so the
BMS has to limit the available charging current to a constant 85mA or less to ensure the maximum cell voltage isn't exceeded.
As further cells reach their 4.2V target voltage, the process continues until all of the cells reach their target voltage.
It's around this stage that the constant voltage charging cuts in and the current slowly decreases until it falls below a certain level where the
BMS then completely disconnects the charging current
(usually accompanied by the green LED lighting up on the charger).
Unfortunately, the only way the
BMS can fully balance the 14 cells is to charge them to the target voltage of 4.2V per cell from a 58.8V power source.
You could set your power supply to 58.8V and use 3 diodes in series to drop the voltage to ~57V
(~4.07V per cell) for the majority of charges and simply bypass the diodes to perform an occasional fully balanced charge if required.
You could also occasionally balance them to 4.1V per cell with your iMax B8 charger by selecting "LiIo 3.6V" instead of "LiPo 3.7V" and charging half the pack at a time
(or both halves in parallel if you disconnect the bms 
).This might balance them a lot quicker as the iMax B8 has a much higher 300mA balance current.
Alan
