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First, one cell overheated.

When a cell overheats, electrolyte fluid inside the cell vaporizes into white vapor (fumes), which is released outside the cell, and subsequently, the cell no longer functions.

Heat is transmitted to other cells and they also overheat.

The cell is designed so that it does not affect the other cells in the event of overheating. But in the battery failures that occurred, it was found that when one of the cells overheated and lost its function, it might have affected the other cells. For example, it might have short-circuited and transmitted large electric currents or heat to other cells. U.S. and Japan transportation investigative agencies have stated that overheating of one cell initially occurred in the battery failure.

Mechanism of battery failure that was identified in the investigations

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