Hiya Mac.....
There is no dedicated vent tube to the exterior. (From the Battery enclosure).
To me, that signals that any venting or discharge is reliant on gravity, pressure differential, and a strategically located scupper (venturi).
All very
passive and not in tune with flaming electrolyte migrating about the decking of the EE Bay.
The Bay is pressurized, and conditioned, the Battery needs warmth to function, though not too much....
The enclosure must not be tightly sealed, one would think it must have the same pressure as the rest of the volume of the E/E Bay?
I agree with the white expansive plug, and posit that it faces inward, away from the enclosure sides, where it might conflict with its own migration out of its hole.
I am speechless that Boeing have come up with these "fixes", each and every one requiring substantial design and engineering, not to mention approval, (Self approval perhaps not in the mix this time
).
The whole set-up presents as a too passive design/fail chain.
I am likewise surprised that there does not appear to be sufficient caution to protect the composite structure from burning fluids, and hot gases. The fuselage is
flammable...
The lack of an active pressure/venting system being the giveaway....