The lithium-ion battery at the center of the investigation was not overcharged, the National Transportation Safety Board said in a statement Sunday. The NTSB has not determined the cause yet in that 787 fire.
A second 787 experienced battery trouble in Japan on Jan. 16. Together, the incidents prompted aviation authorities around the world to ground Boeing 787s until the jet maker can prove the batteries are safe to operate.
The concerns over the 787 have put battery maker GS Yuasa Corp. of Japan at the center of attention. In the year ended March 2012, GS Yuasa's lithium-ion batteries business had an operating loss of $36 million, according to the company's annual report.
The company spent 75 percent of its total capital investments on the segment last year, according to its website. GS Yuasa's multi-year, multi-million dollar contract, announced in June 2005, to supply its batteries to Thales SA for the electrical system of the 787 was an opportunity to offset losses from sales to carmakers.
While GS Yuasa announced in 2009 that lithium-ion batteries for vehicles will become a core business for the company, the battery maker since then hasn't turned the technology into profit.
"They had been hoping to make up for the lack of sales to carmakers by selling to Boeing," said Jun Yamaguchi, a Credit Suisse AG analyst in Tokyo. "Any inability to sell in the aviation market is going to make the lithium-ion battery business even more unprofitable for GS Yuasa."
Boeing said last week it won't deliver more 787s until the U.S. Federal Aviation Administration instructs it on how to prove the Dreamliner's flammable lithium-ion batteries are safe. The world's biggest motorcycle-battery maker, GS Yuasa's shares have slumped 9.7 percent since the Jan. 7 fire aboard a Japan Airlines Co. 787 in Boston.
GS Yuasa is cooperating with the authorities on the investigations and the probe may take months to be completed, spokesman Hiroharu Nakano said Jan. 17.
"We'll first look at the battery, but we have to check if battery is the only problem or there's an entire electrical system issue," Nakano said in a phone interview. "We need to fully investigate the system."
The investigations are ongoing, and the company has nothing to comment about its batteries, Yasushi Yamamoto, a spokesman for GS Yuasa, said by phone Jan. 18.
U.S. officials and Boeing are investigating whether defective batteries from the same batch caused failures in two 787 Dreamliners that triggered the plane's worldwide grounding last week, according to two people familiar with the incidents.
If proven true, flaws may be confined to a small number of 787s, rather than indicating a systemic fault with the plane's design or manufacturing, and could speed resumption of flights on the jet. The people, who weren't authorized to speak publicly, said the information is preliminary and investigators haven't yet ruled out other causes.
Electrolyte was found to have leaked from the battery box of the All Nippon Airways Co. plane that had an emergency landing at Takamatsu airport on Jan. 16., according to Japan's transport ministry. The interiors of the battery box were found to be damaged.
All Nippon owns 17 Dreamliners, while Japan Air has seven. The 787 is Boeing's most technologically advanced jet, featuring a body made of composite materials instead of the traditional aluminum. It conserves fuel by using five times more electricity to power its systems than other planes, and is Boeing's first model to rely on lithium-ion batteries.
All four plants that GS builds lithium-ion batteries are located in Japan and the batteries supplied to the Dreamliners are made at a factory in its Kyoto headquarters. The electrical system, which the battery is embedded into, is manufactured by Thales, Europe's biggest defense-electronics maker.
Boeing chose lithium-ion batteries for the 787 because they hold more energy and can be quickly recharged. Boeing got regulators' permission to use lithium batteries in the jetliner in 2007, three years after U.S. passenger planes were barred from carrying non-rechargeable types as cargo because of their flammability.
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