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.

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

Unlike the Toyota 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. 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. Mr. 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 said. "We will work with a network of suppliers as they develop alternative chemistry."

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.

Whether buyers will go for plug-in electric vehicles remains uncertain, according to a new report by the forecasting company IHS Global Insight.

"Hurdles include cost considerations and 'charge anxiety' -- consumers want to plug in and top off the battery whenever the vehicle is parked, day or night," the report said.