Mitsubishi Motors Development Engineers Reveal Their PHEV Problems

How has Mitsubishi improved the reliability of its batteries and software?

Jun 20, 2014
Naoshige Shimizu, Nikkei Automotive Technology
Fig. 1 The Outlander PHEV’s appearance
Fig. 1 The Outlander PHEV’s appearance
[Click to enlarge image]
Fig. 2 An overheated and combusted Li-ion secondary battery after shipment
Fig. 2 An overheated and combusted Li-ion secondary battery after shipment
[Click to enlarge image]

Mitsubishi Motors released the “Outlander PHEV” plug-in hybrid electric vehicle at the end of January in 2013 (Fig. 1). The electrodes of the vehicle’s Li-ion secondary battery cell short-circuited, causing the battery pack to erode and combust. (Fig. 2). Independent of this battery problem, numerous defects also surfaced with regard to the vehicle's control software; so far, Mitsubishi has reported two recalls to the Japan Ministry of Land, Infrastructure, Transport and Tourism (MLIT), and has initiated three service campaigns. The company held two press conferences in April 2013 to explain the background and causes of the incidents after they found the battery defects. In July, the company invited the public to observe the operations replacing the recalled batteries.

In March of 2013, Mitsubishi Motors reported four defects related to the Li-ion secondary battery. One defect occurred in the electric vehicle (EV) “i-MiEV,” with the remaining three occurring in the Outlander PHEV. All four cases had been found before the vehicles were sent to customers.

Every case involved overheating and combustion while charging the batteries, as well as overheating post-charge. Mitsubishi Motors, along with Lithium Energy Japan (a joint venture formed by GS Yuasa, Mitsubishi Corporation, and Mitsubishi Motors, hereinafter referred to as LEJ), who manufactures the battery cells, have jointly investigated the vehicles and batteries where these four cases were found. This research discovered the distinct possibility that the cathodes and anodes of the battery cells had short-circuited.

>> Continue to Japan Technology Report