* Problematic batteries show signs of short circuit
* Batteries may have experienced excessive shock in testing
* Mitsubishi Motors still trying to find cause
By Sophie Knight
TOKYO, April 10 (Reuters) - Mitsubishi Motors Corp will extend its production and shipment stoppage of its Outlander plug-in hybrids until it finds the cause of an overheating lithium-ion battery in one of the vehicles, the automaker said on Wednesday.
The company stopped production and shipments in late March as lithium-ion battery technology faces heightened scrutiny after problems with batteries in Boeing Co 787 Dreamliner jets.
Batteries on the Outlander are supplied by a venture called Lithium Energy Japan, owned by Japan's GS Yuasa Corp, Mitsubishi Corp and Mitsubishi Motors. Kyoto-based GS Yuasa is also the battery maker for Boeing's Dreamliner.
Ryugo Nakao, managing director of Mitsubishi Motors, told reporters there were two other cases in which Outlander batteries had signs of short-circuits and where abnormal battery voltage was detected - one where a customer in Tokyo could not start running the vehicle, and another where a car in a dealership in Gifu prefecture would not charge properly.
In the first case, the battery also short-circuited and emitted a strange odour, he said. The company found that a part of its battery pack had emitted heat and a resin part around that had melted.
Mitsubishi Motors was exploring the possibility that the batteries may have experienced excessive shock when they were being placed onto a testing machine, he said.
The executive could not say when the automaker will resume production because it will not do so until it has found the cause. While the company aims to finish the investigation by the end of April, Nakao could not confirm when it would be completed.
Separately, a lithium-ion battery fire in a i-MiEV electric vehicle at a Mitsubishi factory may have a similar cause to the problems in the Outlander battery, but Mitsubishi had been unable to confirm the exact cause in either case, Nakao said.
Two companies supply batteries for the i-MiEV - Lithium Energy Japan and Toshiba Corp. Mitsubishi Motors has stopped using the Lithium Energy Japan batteries but is continuing to produce and ship i-MiEV vehicles by using Toshiba-supplied batteries, a company spokesman said.
He added that the pace of production and shipments had slowed significantly but declined to give the specific production and shipment figures.
Mitsubishi Motors has sold 4,000 Outlander plug-in hybrid cars to date and has received 4,000 more orders. The vehicle is only sold in Japan, although it plans to sell the hybrid in Europe starting in July.
By end-February, it had sold 8,400 i-MiEVs in Japan and 6,600 overseas.