TEXT SIZEReutersJanuary 23, 2013TOKYO/WASHINGTON — Japanese regulators have joined their U.S. counterparts in all but ruling out overcharged batteries as the cause of recent fires on the Boeing 787 Dreamliner, which has been grounded for a week with no end in sight.Solving the battery issue has become the primary focus of the investigation, though the head of the U.S. Federal Aviation Administration said on Wednesday there are still no firm answers as to the cause and no clear timetable yet for returning the plane to flight.Regulators grounded the Dreamliner on January 16 after a series of safety incidents, including battery fires on planes in the United States and Japan. The Japanese incident forced a plane to make an emergency landing.
