1. Description of Occurrence

At around 8:15 pm on March 18, one of the 16kWh drive battery packs used in the i-MiEV (lithium-ion battery) 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 one hour after. The battery pack was charging connected to charge-discharge inspection equipment as part of final inspection. The plant contacted the fire department and the fire was extinguished at around 9:53 pm on the same day.

2. Effect/Damage

No injuries were caused. Although one drive battery pack and a charging cable for the inspection equipment were burned out, there was no damage to the building or to the inspection equipment itself. However, per instruction by the fire department, equipment involved in the fire (charging/discharging testing equipment) have currently been shut down.

3. Investigation into Cause

Although the cause has yet to be fully determined, a possibility includes a change in the manufacturing process of the battery supplier, resulting in defects. MMC is decisively moving forward with continued investigations along with the supplier to determine fully the root cause. The number of applicable Japan-specification vehicles, which employ the same drive battery pack assembled in the aforementioned modified manufacturing process totals 68 units, used by fleet customers. Another 45 drive battery packs have been shipped as spare parts.

4. Further Investigation

MMC is currently conducting further investigations to determine the root cause.

MMC will contact its fleet customers with vehicles that contain the same drive battery packs to explain the situation and also check their vehicles. MMC will also investigate the usage of the drive battery packs for spare part use.