DETROIT -

General Motors will invest $449 million to upgrade manufacturing processes at Detroit-Hamtramck Assembly and Brownstown Battery Assembly plants.

The investment, announced at the Automotive Press Association, is the largest to date at both facilities -- and includes $384 million at Detroit-Hamtramck for new body shop tooling, equipment, and additional plant upgrades to build the next generation Chevrolet Volt and two future products. This brings GM’s total investment at Detroit-Hamtramck to more than $1 billion over the last five years.

GM’s $65 million investment at its Brownstown Battery Assembly will support the next generation of lithium-ion battery production and future battery systems.

The Detroit-Hamtramck Assembly Plant is the world’s only automotive plant that mass-produces extended-range electric vehicles – including the Volt, Cadillac ELR and Opel Ampera – for markets in 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.