Plane battery theory ruled out

Hiroko Tabuchi / New York Times News Service /

TOKYO — The Japanese investigation into a battery that overheated and prompted the emergency landing of a Boeing 787 airliner last week has found no evidence that the battery was overcharged, a top aviation safety official said Wednesday, casting doubts on one recent explanation put forward by Japanese investigators and clouding the U.S. aircraft maker’s efforts to get its planes back in the air.

Regulators around the world have grounded the advanced 787, called the Dreamliner, after a battery malfunction and smoke caused pilots aboard an All Nippon Airways flight to make an emergency landing last week, and a similar battery aboard a parked 787 operated by Japan Airlines ignited at Logan Airport in Boston on Jan. 7.

Japanese investigators who retrieved the charred and disfigured battery pack from the All Nippon plane initially suspected overcharging, a dangerous condition where a battery is charged beyond its electrical capacity and becomes susceptible to overheating and fire.

But data retrieved from the All Nippon jet suggested that the battery had not been charged beyond its maximum design voltage, 32 volts, Norihiro Goto, chairman of the Japanese Transport Safety Board, said.