BROWNSTOWN TOWNSHIP, Mich. – General Motors Co. chief Fritz Henderson says a new $43 million plant in Michigan will assemble battery packs for the company’s upcoming rechargeable electric car, as the automaker continues relying on suppliers for key elements of the batteries.

GM’s president and chief executive held a news conference Thursday morning at the plant site in Brownstown Township, 20 miles southwest of Detroit. Production will start in the fourth quarter of 2010, employing about 100 people, GM said.

“Developing and producing advanced batteries is a key step in GM’s journey to become the leader in advanced vehicles,” Henderson said.

Most automakers are working on similar designs, but GM would offer the first mainstream plug-in with the Chevrolet Volt.

Unlike the Toyota Motor Corp.’s Prius and other traditional hybrids, the Volt can run on batteries alone within a 40-mile range. It has a small internal-combustion engine that kicks in after the battery runs out of juice.

The Volt’s battery pack can be recharged from a standard home outlet.

South Korea’s LG Chem Ltd. is making the lithium ion battery cells, and Henderson said he expects to continue looking outside GM for key technological elements of its battery powered cars.

“We’re not a chemical company, so the advanced chemistry of the cells, I don’t see us being in that business,” he told reporters after the announcement. “We will work with a network of suppliers as they develop alternative chemistry.”

The announcement ceremony took on the air of a Michigan pep rally, with Democratic Sens. Carl Levin and Debbie Stabenow, and veteran Democratic U.S. Reps. John Dingell and Sandy Levin touting the plant and the Volt itself as keys to the state’s drive to revive its hard-hit economy.

“As we put the nation on wheels, we are now going to help wean the nation off oil,” Carl Levin said.

Dingell said the U.S. auto industry is moving to retake the technological lead he said was “stolen” by its overseas rivals.

“We need to tell these foreigners, ‘Get out of the way, we’re coming through,”’ he said, to laughs from the audience.

A 12-year, 50-percent personal property tax abatement from Brownstown was only part of a government support package topping $100 million for GM’s electric car program.

Government and industry “are not enemies,” Sandy Levin said. “This shows what happens when we work together.”