Boeing has said that various technical problems are to be expected in the early days of any aircraft model.
The 787 relies more than any other modern airliner on electrical signals to help power nearly everything the plane does. It's also the first Boeing plane to use rechargeable lithium ion batteries, which charge faster and can be molded to space-saving shapes compared to other airplane batteries. The plane is made with lightweight composite materials instead of aluminum.
In Wednesday's incident, Japan's Kyodo News agency quoted transport ministry investigator Hideyo Kosugi as saying that electrolyte from the plane's main battery had leaked through the electrical room floor to the exterior of the aircraft.
GS Yuasa Corp., the Japanese company that supplies all the lithium ion batteries for the 787, had no comment as the investigation was still ongoing. Thales, which makes the battery charging system, had no immediate comment.
During the flight, a cockpit instrument showed a problem with the 787's battery and the pilot noticed an unusual smell, the airline said. The flight requested and was granted permission to make an emergency landing at Takamatsu airport.
Aviation safety expert John Goglia, a former National Transportation Safety Board member, said the ANA pilot made the right decision.
"They were being very prudent in making the emergency landing even though there's been no information released so far that indicates any of these issues are related," he said.
But much remains uncertain about the problems being experienced by the 787, said Masaharu Hirokane, analyst at Nomura Securities Co. in Tokyo.
"You need to ensure safety 100 percent, and then you also have to get people to feel that the jet is 100 percent safe," Hirokane said.