Chrysler LLC uses the North American International Auto Show in Detroit to introduce a fourth electric-drive concept vehicle, the Jeep Patriot EV, ratcheting up suspense over which one it will build.

The auto maker has said it would market one of three previously unveiled electric-drive concept vehicles starting in 2010.

The Patriot EV “is just one more example of what is possible through the technology Chrysler is developing,” says Lou Rhodes, President of ENVI and vice president- advance vehicle engineering.

ENVI, known internally as “Envision,” is the auto maker’s advanced-technology vehicle-development enterprise.

When the Patriot EV’s lithium-ion battery is depleted, it benefits from a “range-extender” setup that consists of an onboard generator fueled by a small gasoline engine. Total range: 400 miles (644 km), including 40 miles (64 km) of zero-emissions, all-electric operation.

It joins a pair of range-extender models in the ENVI stable, along with an all-electric sports car. They are the Chrysler Town & Country EV minivan, Jeep Wrangler Unlimited EV and the Dodge Circuit EV 2-seater.

Unveiled for the media in September, they join the Patriot EV on display in Detroit.

All benefit from new paint, while the Circuit has been restyled to reflect Dodge-brand cues.

The Patriot and Wrangler feature front-wheel and rear-wheel drive, respectively, though Chrysler says it is exploring a 4-wheel-drive layout for the Wrangler, using in-wheel motors.

The minivan and Wrangler boast ranges equal to that of the Patriot EV, while the Circuit is said to run up to 200 miles (322 km) on a single charge. Like the Patriot, they employ Li-on batteries.

While Rhodes tells Ward’s Chrysler’s EV plans are “on track” for the planned 2010 launch, he concedes Li-ion technology for automotive powertrains still is evolving.

“To ensure that you can get 10-year (battery) life, you want battery packs that have been tested for 10 years,” he says during a media preview of Chrysler’s auto show offerings. “Right now, most of the chemistries we’re dealing with are two to three to years of testing.”

But projections indicate the 10-year bogey is achieveable.

The first Chrysler EV, which he does not divulge, will be a low-volume product. “Our real focus is to get to ’11, ’12 and beyond,” Rhodes says.

Chrysler expects to introduce three additional EVs by 2013.

Meanwhile, Rhodes says Chrysler is leveraging the resources and potential buying power of its “neighborhood vehicle” manufacturer, North Dakota-based Global Electric Motorcars LLC.

Neighborhood vehicles are low-speed, all-electric vehicles sometimes found in gated communities and college campuses.

“When we looked at electric drive as a powerpack, we said, ‘Let’s align GEM to ENVI for the benefit of the evolution of next-generation motors, batteries – even lithium – power controls,’” Rhodes says, adding the learning curve is “flowing both ways.”

GEM has a customer list with some 40,000 names. This provides a ready source of data for real-world examination of issues, such as charge-station performance and service, Rhodes says.