i had an m12 pack that would not charge, found that the lead from the thermistor had broken where it meets the PCB. Resoldered it and it came back to life. Proves that there's something you can check on these.
again m18 doesnt have these problems
yeah ive done it on two packs. Soldered a jst-xh to the pcb tap points, works fine. Just remember the order, very easy to reverse it and pop something.
if I add the jst-xh balance lead like you mentioned, do I need to disconnect it before putting the pack on the milwaukee charger or can I leave it dangling?
the lack of documentation for these M12 packs is somewhat annoying since a few loyal enthusiasts have reverse engineered the M18 to hell and back with github repos and what not but the M12 packs nobody seems to care about since they are relatively cheaper.