NEW YORK --- Volvo Car Corp. has chosen American-made lithium-ion battery systems, designed and produced by Ener1 Inc., to power a pair of plug-in hybrid V70 demonstration cars being put through their paces across Europe this fall. 

The vehicles are part of a development program leading up to the planned 2012 commercial launch of a production plug-in model. The project is a joint venture between Volvo and Vattenfall, one of Europe's largest electric utility companies and a leading proponent of electric vehicle infrastructure build-out. 

With a single charge from an ordinary household socket, the cars can run up to 31 miles (50 kilometers) using only battery electric power, more than meeting average daily commuting needs for the vast majority of drivers. Beyond the electric-only range, a fuel-efficient diesel engine kicks in to power the vehicle without interruption. 

"These cars and the battery systems constitute a tremendous engineering achievement and a major step forward in the commercial evolution of electric drivetrain technology," said Ener1 CEO Charles Gassenheimer. 

Made by Ener1's manufacturing arm, EnerDel, the batteries were custom built for this test program. A standard production car was deliberately chosen as the platform in order to prove broad applicability of the technology in otherwise conventional automobiles. The diesel engine will eventually run on renewable biodiesel as well as standard blends. 

"Efficient, durable high-performance batteries are a vital element in plug-in hybrid and electric drive vehicles. They have to work year-in, year-out under harsh conditions and extreme temperatures, which means engineering and design are absolutely critical," said Anders Bjornberg, hybrid vehicle specialist at Volvo Cars Hybrid Center. 

The cars will be used to gather information and experience about the driving habits and performance expectations of everyday motorists using the new technology, as well as their actual charging needs. Vattenfall will test different concepts for high-speed home charging, as well as charging stations in public places, where owners pay to fuel with electricity instead of liquid fossil fuels. 

The partnership between Volvo and Vattenfall began in January 2007, and has been advancing on a fast track. The goal is to produce plug-in hybrid vehicles and introduce them on the market as early as 2012. 

Vattenfall is Europe's fifth largest generator of electricity, with operations in Denmark, Finland, Germany, United Kingdom, Poland and Sweden.