DETROIT – General Motors will build the Cadillac ELR extended-range electric vehicle at its Detroit-Hamtramck facility, North America President Mark Reuss announces at the SAE Convergence conference here.

The Detroit plant already builds the Chevy Volt upon which the ELR is based, so the disclosure is not a surprise.

However, the auto maker is sinking an additional $35 million into the plant for ELR production, bringing GM’s total investment in the assembly facility to $561 million since December 2009.

While the ELR is based on the Volt, it will be significantly different inside and out, Reuss tells reporters on the sidelines following his prepared remarks.

The highly sculpted 2-door coupe will feature more aggressive driving dynamics thanks in part to larger tires and wheels, plus “the interior will be spectacular,” Reuss promises, including the brand’s new Cadillac User Experience (CUE) human-machine interface.

Reuss declines to discuss the new car’s pricing or expected volume, but does say he expects the ELR customer to be significantly different from the typical Volt buyer.The Volt’s $40,000 price tag has been a hurdle for the car, and the ELR certainly will command an even steeper sticker.

Production of the ELR has been an on-again, off-again proposition at GM for several years. Former GM product boss Bob Lutz said shortly after the ELR bowed in 2009 as the Cadillac Converj concept that adding necessary luxury items and performance to the platform would diminish the car’s battery range too much. GM’s 2009 bankruptcy also put the car on hold for awhile. Reuss brushed off the range issue when speaking with reporters.

Production is expected to begin in late 2013, with the car going on sale in early 2014. It will be the first coupe built at the plant since the ’99 Cadillac Eldorado.

The facility also makes the Volt-based Opel Ampera and Holden Volt EREVs that are exported to 21 countries.