US safety investigators confirms it is reviewing the history of battery replacements on Boeing 787s to determine if there is any relation to the battery failure and fire on board a parked Japan Airlines 787 last month.
Boeing provided fleet information on the GS Yuasa-supplied lithium-ion batteries early in the investigation, the National Transportation Safety Board (NTSB) says.
The previous battery replacements have been described by Boeing officials as not safety-related and routine, although they were required at a "slightly" higher frequency than the company expected.
Boeing also says that it replaces 2,000 batteries on aircraft every year as part of routine operations.
The battery fire on the JAL 787 and a subsequent in-flight failure aboard an All Nippon Airways 787 raised safety concerns about the lithium-ion chemistry. The 787 was the first commercial aircraft to propose lithium-ion batteries as a starter for the auxiliary power unit and main emergency back-up power source.
The NTSB's seventh update on its ongoing, nearly month-old investigation offers no further clues about a root cause behind the 787 battery failures that have kept the fleet grounded more than two weeks.
The investigation next week will begin "soft short" tests on an undamaged lithium-ion battery, the NTSB says. The goal is to reveal any localised shorts within one of the eight cells inside the 32V-rated battery. Another investigator will examine a component called a battery contactor, which connects a wiring bundle that interfaces with the battery, the NTSB says. The contactor will be examined at the manufacturer in France. Thales is the supplier for Boeing's electrical power conversion unit, which supplied the battery and the battery charger unit for the 787.