"Evidence of short-circuiting" producing a chemical reaction which caused an increase in temperatures, according to federal accident investigators from the National Transportation Safety Board (NTSB), plagued lithium-ion batteries in two Boeing Dreamliners this month forcing planes to be grounded. The battery problems caused FAA to ground all Dreamliners in the U.S. and aviation agencies throughout the world followed suit, grounding a total of 50 Boeing Dreamliner 787 airplanes.
A recent Associated Press article noted that it was not obvious to investigators which came first, the short-circuiting or the chemical reaction known as a "thermal runway".
In the first instance, a Japan Airlines 787 caught fire after landing at Logan International Airport in Boston, January 7. NTSB investigators continue to examine the insides of the battery which burned. The fire occurred in the aircraft’s rear auxiliary power unit. (AP, 1/24/13) The second incident of battery failure forced a Dreamliner to make an emergency landing in Japan. While there was no fire in the second incident, there was smoke in the cabin.
Although Boeing had received orders for 800 new Dreamliner planes, it has stopped delivery of all planes until the problem of the batteries is corrected. Boeing continues to manufacture the planes, however. The 787 is made from lightweight composite materials and utilizes electronic systems, rather than hydraulic or mechanical systems to a greater degree than previously manufactured airplanes. (AP, 1/24/13)
Even though the lithium-ion batteries have been known to catch fire when they overheat, the FAA certified the 787 battery system and Boeing claims to have installed safeguards to prevent such accidents from happening. One problem may be a type of battery charger unit that was designed for the Boeing 787 with which the designing contractor, Securaplane, had problems as well.
A recent inspection in Japan has focused the investigation from the batter maker to the manufacturer of the battery voltage and temperature monitoring system.