Li-ion Batteries from GS Yuasa Involved in Two Overheating Incidents in Mitsubishi EVs

March 27, 2013 by Jeff Shepard

Mitsubishi Motors Corporation (MMC) has reported two separate instances of problems with Li-ion batteries in its electric vehicles. In both cases the batteries were supplied by GS Yuasa, the supplier for Boeing Company 787 jets, which has also had battery problems. MMC reported one instance of a fire occurring in one of the drive battery packs used for MMC's electric vehicles (EV) on March 18 at its Mizushima Plant in Okayama prefecture in Japan. Two days later, on March 20, MMC reported an instance of a melted area in a part of the drive battery pack of an Outlander PHEV (plug-in hybrid electric vehicle) caused by an overheating battery cell.

At this time, MMC suggests that Outlander PHEV drivers refrain from using external charging or Charge Mode until the cause is found. In addition, dealers will be contacting Outlander PHEV customers regarding use of their vehicle as well as responding to customer inquiries.

In the first occurrence, at around 8:15 pm on March 18 at the company’s Mizushima Plant, one of the 16kWh drive Li-ion battery packs used in the i-MiEV overheated in the battery inspection room at the EV assembly factory at the Mizushima Plant. The drive battery pack started to smoke, and then ultimately caught fire after one hour. The battery pack was charging connected to charge-discharge inspection equipment as part of final inspection. Although the cause has yet to be fully determined, possibilities include a change in the manufacturing process of the battery supplier, resulting in defects.

In both cases, MMC is moving forward with continued investigations along with GS Yuasa to determine the root cause. The number of applicable Japan-specification vehicles, which employ the same drive battery pack totals 68 units, used by fleet customers. Another 45 drive battery packs have been shipped as spare parts.

The Outlander PHEV that was involved in the second battery meltdown had just been fully charged from a standard outlet then stored at a dealership in Yokohama. The next day, the dealer personnel attempted to move the vehicle from storage for delivery to a customer when it was found that it would not move. In addition a strange odor was detected around the vehicle. Upon checking the underbody of the vehicle, signs of melting were observed on the part of the drive battery pack.

When the battery pack was examined by the supplier, it was found that one of the battery pack's 80 cells had overheated, melting adjacent cells. The 80 cells in the drive battery pack are divided and set into three "blocks" within the drive battery pack. Examination found that only one of the three blocks sustained any damage. No damage to the dealership facilities nor injuries occurred. Outside of the drive battery pack itself, there was no damage to the vehicle.