if you have charged each cell to 4.2v then put the batt together then thats a bad idea as 1 short connecting the bms the hole lot could go bang.I haven't yet connected up the charger or the output, but the cells were fully charged before i assembled them - could it be the BMS reading an imbalance (or overcharge) of those cell groups, and then doing a balancing of them.
Only the cell group 4 LED is on now.
No not yet, i have just created the pack and connected the BMS, the wires are attached ready for the load and charger - that is/was this weekends job.Have you tried a load on the output