@ Lyman,
I did not see the pin coupler, the battery was too fried. Again, though, re: the BC-1300 monitor/ is it dedicated to LITHIUM Ion?
The BC-1300 series are for both Ni-Cad and Securaplane Lithium-Ion batteries.
The Battery charger BMS 50 pin connector J1 is connected to its complementary J1 connector on the Battery pack case. This should be obvious when viewing this
exemplar pack courtesy NTSB.
P.S. The original link I posted of the front of the damaged JAL battery pack, was just that, the one under investigation by the NTSB.