The inside of the battery case, the BMU sensing wiring harness, and the lower and upper
fixation trays showed the most thermal damage in the areas near cells 5, 6, and 7. The insulating
material between the cells was the most damaged in the areas adjacent to cells 5 through 8.
Further, cells 5 through 8 vented, and the petals of their vent discs were splayed out, indicating
that the cells vented under high pressure. Cells 1 through 3 also had ruptured vent discs, but they
remained mostly in the same plane as the vent opening, indicating that the venting occurred with
less force than the venting for cells 5 through 8. This evidence showed that the initiating thermal
event and subsequent thermal runaway of additional cells began on the right side of the battery
where cells 5 through 8 were located.