General Motors Corp. will invest $449 million to upgrade manufacturing processes at two Detroit-area automotive assembly plants to support the next-generation Chevrolet Volt battery-electric hybrid, the company has announced.

GM pledged to spend $384 million at the Detroit-Hamtramck Assembly for new body shop tooling, equipment, and additional plant upgrades to build the next-gen Volt and two future products. GM will spend $65 million at its Brownstown Battery Assembly to support the next generation of lithium-ion battery production and future battery systems.

The Detroit-Hamtramck Assembly plant produces extended-range electric vehicles such as the Volt, Cadillac ELR and Opel Ampera for 33 countries. Detroit-Hamtramck also builds the Chevrolet Malibu and Impala sedans and is home to a 264,000-square-foot photovoltaic solar array that can generate up to 516 kilowatts of electricity, or enough to charge 150 electric vehicles per day.

Brownstown Battery Assembly’s 479,000-square-foot, landfill-free facility south of Detroit produces the lithium-ion battery packs for GM’s extended-range electric vehicles. It started mass production in October 2010 and is the first high-volume manufacturing site in the U.S. operated by a major automaker for automotive lithium-ion battery production. The site was made possible with the help of American Recovery and Reinvestment Act funding through the U.S. Department of Energy.

Since 2009, GM has announced more than $5.4 million in U.S. facility investment for vehicle technologies, including $2.8 billion in Michigan-based facilities.