Mitsubishi Motors Corp. said it has suspended the manufacturing and shipment of electric vehicles that use a lithium-ion battery made by a subsidiary of GS Yuasa Corp. after two recently caught fire.
The move escalates problems facing the beleaguered Kyoto-based company, which manufactured the lithium-ion battery that led to the grounding of Boeing 787 Dreamliner passenger aircraft.
The latest problems concerned lithium-ion batteries for the Mitsubishi i-MiEV electric vehicle and the plug-in hybrid model of the Outlander sports utility vehicle.
The batteries were manufactured by Lithium Energy Japan, a joint venture set up by Yuasa, Mitsubishi Corp. and Mitsubishi Motors.
The battery in the i-MiEV caught fire at Mitsubishi Motors' Mizushima plant in Okayama Prefecture on March 18 when it was being charged during a test before installation in the vehicle.
Although the battery and cable were charred, no one was injured.
The Outlander battery gave off a bad smell on March 21 when it was being charged at an auto dealership in Kanagawa Prefecture in preparation for delivery. Overheating led to the evaporation of the organic electrolyte fluid inside the battery, which had partly melted.
At a March 27 news conference, Ryugo Nakao, a Mitsubishi Motors executive, said the problems appeared to be caused by a malfunction during the manufacturing process.
Both batteries were produced at the same LEJ plant.
The Outlander battery, which was taken apart, showed signs of a short circuit in the interior wiring. In the past, defective batteries were discovered on the same production line after impurities became mixed in the battery interior.
Nakao said it would take between one and two weeks to get to the root cause of the problem and decide if recalls of similar vehicles are warranted. The company has already reported the problem to the transport ministry.
Nakao added that it was difficult to say if there was a connection with the battery problems linked to the Dreamliner since the production site and battery structure are different.
A Yuasa official said the batteries in the Mitsubishi vehicles were totally different from the ones used in the aircraft.
Meanwhile, the Japan Transport Safety Board said on March 27 that it will focus on the battery in the Dreamliner to determine the cause of smoke filling an All Nippon Airways Co. aircraft, which led to an emergency landing in January, at Takamatsu Airport in Kagawa Prefecture.
The board said there was a strong possibility that a large current surge in the battery caused sparks to fly. Because no irregularities were found in the external equipment connected to the battery, board investigators will focus on the battery in their future study.
Board officials said there were 12 areas within the stainless steel case used for the eight cells in the battery that showed signs of scorching from electric sparks. Areas in the case were peppered with 10 holes.
Although no problems were found in the external equipment, including a charger, there is the possibility of a mismatch between the battery and the charger.
The investigation will continue to seek the root cause of the problem.
(This article was compiled from reports by Ryuji Kudo and Ayako Nakada.)
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