Investigation reveals cause of battery fire on Boeing 787 Dreamliner

Via Ars Technica, which has links and more detail:

Investigators at the National Transportation Safety Board have determined the cause of the battery fire in the Japan Airlines 787, saying that the fire was caused by a short circuit in one of the battery’s cells leading to a thermal runaway which led to the other cells catching fire. The NTSB said that temperatures inside the battery exceeded 260 degrees Celsius (500 degrees Fahrenheit).