TOKYO — U.S. investigators said Wednesday that they asked Boeing to provide a full operating history of lithium-ion batteries used in its grounded 787 Dreamliners as Japan's All Nippon Airways revealed it had repeatedly replaced the batteries even before overheating problems surfaced.
National Transportation Safety Board spokesman Peter Knudson said the agency made the request after becoming aware of battery problems at ANA that occurred before two recent incidents involving the planes' batteries. Boeing has already collected some of the information, he said.
All 50 of the Boeing 787s in use around the world remain grounded after an ANA flight on Jan. 16 made an emergency landing in Japan when its main battery overheated. About a week before that, a battery caught fire in a 787 parked at Boston's Logan International Airport.
ANA said it had replaced batteries on its 787 aircraft about 10 times because they didn't charge properly or connections with electrical systems failed, and informed Boeing about the swaps. Japan Airlines also said it had replaced 787 batteries. It described the number involved as a few but couldn't immediately give further details.
The 787 is the first airliner to make wide use of lithium-ion batteries. They are prone to overheating and require additional safeguards to prevent fires. However, ANA spokeswoman Megumi Tezuka said the airline was not required to report the battery replacements to Japan's Transport Ministry because they did not interfere with flights and did not raise safety concerns.
Boeing said Wednesday that replacing the batteries on a plane is not uncommon. The company said that it has not "seen 787 battery replacements occurring as a result of safety concerns."
Laura Brown, a spokeswoman for the U.S. Federal Aviation Administration, said in Washington that the agency was checking whether the previous battery incidents had been reported by Boeing.
GS Yuasa, the Kyoto, Japan, manufacturer of the batteries, said it could not comment.
The battery problems experienced by ANA before the emergency landing were first reported by the New York Times.
Japanese and U.S. investigators looking into the Boeing 787's battery problems shifted their attention this week from GS Yuasa to the manufacturer of a monitoring system. That company, Kanto Aircraft Instrument Co., makes a system that monitors voltage, charging and temperature of the lithium-ion batteries.
On Tuesday, the NTSB said it was conducting a chemical analysis of internal short-circuiting and thermal damage of the battery that caught fire in Boston.
The inquiry is also analyzing data from flight data recorders on the aircraft, the NTSB said in a statement on its website.