KINOKAWA, Japan (Reuters) - The energy unit of Japan's Panasonic Holdings ( PCRFF ) has finalised preparations for the mass-production of its 4680 electric-vehicle batteries, the company said on Monday, as it seeks to start supplying the cell to automakers.

Panasonic Energy's renovated plant in the western prefecture of Wakayama will serve as the main factory for producing the cells, which the Tesla supplier says have five times the capacity of its smaller 2170 cylindrical batteries.

The bigger 4680 cells will allow automakers to extend the driving range of electric vehicles and use fewer cells to achieve the same battery pack capacity, Panasonic Energy said in a statement.

The company held a ceremony to mark the completion of preparations to start mass-producing the batteries and showed an inspection line where trays stacked with the silver-coloured cells could be seen running through.

The company has sent samples of the 4680 batteries to some of its automakers to which it is already a supplier and intends to kick off production of the new cells after getting the green light from them, a Panasonic ( PCRFF ) spokesperson said.

The company had previously said it planned to start production of the 4680 cells in the first half of the current business year that started in April.

The Wakayama plant is expected to employ roughly 400 staff in the development and production of the new batteries by March 2025, and serve as a site for trying out processes that it could implement at other battery factories around the world, the company said.

Panasonic Energy already makes 2170 and 1860 cylindrical EV batteries at its Suminoe and Kaizuka plants in Japan.