DETROIT – General Motors today confirms plans to invest $384 million in its Detroit-Hamtramck, MI, assembly plant, as well as $65 million in a nearby lithium-ion battery facility, to support production of the next-generation Chevrolet Volt extended-range electric vehicle.

“These two investments represent the next chapter in General Motors,” says Gerald Johnson, vice president-North America Manufacturing for the automaker.

According to WardsAuto data, the next-generation Volt will come in 2015 as a ’16 model. Among the upgrades to the plug-in EV, it is expected the Volt’s all-electric range will see an increase from an average of 38 miles (61 km) in the current model.

Johnson says only that GM customers will be “very pleased” with the next Volt.

The investment in Detroit also will support two new products the automaker has yet to announce. The investment at its 3-year-old Brownstown Township, MI, battery plant will fund output of the Volt’s next-generation Li-ion battery, as well as future batteries for other products.

Johnson does not say how many extra jobs the automaker expects to create with the investments, despite long-circulating reports it plans to add a second shift at the Detroit assembly plant.

“We expect a job (number) increase,” Johnson tells a meeting of the Automotive Press Assn. here. “But ultimately, it will be driven by the market. The market will tell us what to do.”

The investments will begin immediately, Johnson says, and continue over the next two years.

In the past five years, GM has poured $1 billion into the 29-year-old Detroit assembly plant to fund production of the Volt, its Opel Ampera and Cadillac ELR sister EREVs, and the Chevy Impala and Malibu sedans. Since emerging from bankruptcy in 2009, GM has invested $5.4 billion in vehicle-technology-related facilities in five states.

The Volt entered the market four years ago with much publicity, but sales of the $35,000, 4-passenger sedan have not met expectations. Last year, it sold 23,094 units in the U.S., WardsAuto data shows. So far this year, sales are down 15% to 3,606. Its best year was 2012, when 23,461 were delivered.