Originally Posted by Lyman
No monitoring can arrest a thermal runaway. Monitoring was intended to prevent Propagation. Boeing prepared for that, per the regulations.
It didn't work as designed. Because the design was insufficient?
NO. It did not work because something happened that exceeded the design's limits.
Did Boeing ever test the propagation in a battery installed in an actual airplane? As in, remove all safeguards from one cell, short circuit that cell so that it explodes/burns, then see what happens?
A cell only contains a very fixed amount of chemical energy in it, so it's difficult to imagine that "something happened" and emitted way more energy than expected.