The battery fire aboard an All Nippon Airways Boeing 787 passenger jet in January has been traced to thermal runaway inside the unit as per Japanese government investigators. The Ministry of Land, Infrastructure, Transport and Tourism’s Japan Transport Safety Board (JTSB) also found that the battery’s grounding wire had been severed. The JTSB performed a CT scan on the battery unit and disassembled it to figure out what caused the Jan. 16 fire to force the ANA 787 to make an emergency landing at Takamatsu airport in Kagawa Prefecture. According to the safety board, all eight lithium-ion battery cells in the unit suffered heat damage. Of those, six had internal deformations and black burn marks caused by overheating, while a major electrical discharge also melted the aluminum wiring.
Of the two cells in the worst condition, the positive electrical contacts on one were also damaged. Of the two least damaged cells, one had holes a few millimeters in diameter in its steel casing. The accident has led to the grounding of virtually every Dreamliner across the globe.
