The first incident involved drive battery for the i-MiEV electric vehicle, which overheated in an inspection room at the Mizushima plant and caught fire an hour later. Mitsubishi said there had been no damage to the building or the charge-discharge equipment it was connected to, and no injuries as a result of the incident.

An investigation is underway, and while no cause has been found yet the manufacturer said it could be a result of a change in the manufacturing process for the battery. Vehicles fitted with the same battery unit are all in Japan, totalling 68 units in use with fleet customers and 45 batteries shipped as spare parts. Mitsubishi has begun contacting owners to arrange vehicle testing.

A second battery fault occurred at a Mitsubishi dealership in Yokohama, where an unregistered Outlander Plug-in Hybrid battery pack overheated following its first full charge. Damage was limited to one of its three blocks of battery cells, with no damage to the rest of the car, or the dealership where it was stored, and no injuries caused.

Mitsubishi said it was working with the battery supplier to investigate why the battery had overheated, and that to date this was a unique incident, but has advised owners to avoid external charging until the investigation is complete. The Outlander Plug-in Hybrid has been on sale in Japan since last December, and launches in Europe at the end of this year. 

European versions of the i-MiEV, and forthcoming Outlander PHEV, are unaffected.