Mitsubishi Heavy Industries Ltd, Japan's biggest heavy-machinery maker, on Wednesday said it plans to start mass-production of industrial-use lithium-ion batteries in late 2012.

Demand for heavy-duty, rechargeable lithium-ion batteries, which can be used in buses and wind power generators, is growing fast amid environmental concerns.

Mitsubishi Heavy said the company is also interested in a scheme planned by Better Place, a California-based company building a global network of charging stations for the electric car industry.

Shares in Mitsubishi Heavy finished up 4.9 percent at 389 yen after the news on Wednesday, compared to a 1.4 percent rise in the benchmark Nikkei average.

Mitsubishi Heavy, which is also expanding capacity in its nuclear power business, said it would spend 10 billion yen ($100 million) to build a test plant for the production of lithium-ion batteries for use in products like fork-lift trucks, wind power generation and solar panel systems in 2010.

The plant, to be located in the company's Nagasaki shipyard in southern Japan, will have an annual output capacity of 400,000 medium-sized cells.

The company said it aims to start operating a mass production plant in late 2012 with an annual output capacity of 1.2 million cells.

Mitsubishi Heavy expects global demand for heavy-machinery use lithium-ion batteries to more than double to around $30 billion by 2015.

Some analysts, however, are skeptical whether the business will raise Mitsubishi Heavy's bottom line, a giant machinery maker with its product lines ranging from tanks to air conditioners.

I don't think the high stock price is sustainable. The business' impact on its earnings would be limited, said Mitsushige Akino, Ichiyoshi Investment management Co's chief fund manager.

Mitsubishi Heavy plans to use the cells mainly in its own industrial machines, but is also interested in the swappable car battery business, senior executive vice president Ichiro Fukue told a group of reporters on the sidelines of a news conference.

We are in talks with Better Place on several business plans, Fukue said.

Better Place plans to offer electric transportation by building a network of charge spots and battery swapping stations.

Producers of car-use lithium-ion batteries include Hitachi Ltd, Toshiba Corp, GS Yuasa and U.S.-based A123 Systems.

(Additional reporting by Taiga Uranaka; Editing by Joseph Radford)