An ANA Dreamliner sits on the tarmac after an emergency landing at Takamatsu Airport in western Japan on January 16.

Story highlights

ANA: 787's main battery failed to start normally on three occasions last year

Batteries have become a focus of the Boeing Dreamliner 787 safety investigation

An inspection of the Japan firm that makes the batteries found no serious problems

Authorities worldwide continue to ground the aircraft amid safety concerns

A Japanese carrier has revealed that it replaced faulty batteries on its Boeing 787 Dreamliner fleet last year, as aviation authorities worldwide continue to ground the aircraft amid safety concerns over the devices.

In an interview with the New York Times, All Nippon Airways (ANA) said the aircraft’s main battery failed to start normally on three occasions and had to be replaced along with the charger. In other cases, one battery showed an error reading and another, used to start the auxiliary power unit, failed. All the events occurred from May to December of last year, the report said.

Megumi Tezuka, spokeswoman for ANA, told CNN Wednesday that 10 lithium ion batteries on its 787s were replaced in 2012, with a low charge being reported on some of the devices on board the aircraft.

READ: ‘No big problems’ with battery maker

However, she said the problems were discovered during maintenance and therefore categorized as minor troubles. She added the airline was not required to report the faults to regulators.

Why the FAA grounded Dreamliner
02:47 - Source: CNN