One of the most limiting factors about an electric vehicle — outside of its price — is its range. Interested consumers are often worried about running out of power mid way through their journey and not having a way to get back home.

Though it is being slowly rolled out, public charging infrastructure isn’t everywhere — and that adds to the fear.

As a solution, Electric Motors and Vehicles Company (EMAV), a global technology, product development and production company has come out with the EMAV PRU trailer, a self-propelled electric vehicle power charging system that extends the range of your car.

The PRU (“Power Regeneration Unit”) is essentially a trailer, which will allow EVs to go on much longer trips by providing back up electricity.

Think of it as a generator for your car.

The car range extender is expected to hit the market in the second half of 2011 and is hoping to be utilized over the next 10 years as the government and transportation industry build charging station infrastructure.

“For electric cars to be truly viable for a mass consumer audience, we need to bridge the gap between low-range electric vehicles that can travel moderate distances to electric vehicles which can truly become the sole family vehicle,” said Wil Cashen, founder and President, EMAV reported Clean MPG.

“JD Power says that sales of electric vehicles will hit only two million in 2020 — that is slow adoption, much due to the current range of these vehicles. Our goal is to move the marketplace beyond the first generation of electric vehicles to more powerful and rugged cars that also have endurance. This will evolve the electric car paradigm from a supplemental to a primary car for consumers.”

Since the trailer needed to be self powered and couldn’t be towed, the company has designed something called a Smart Hitch, which “sends a signal to the speed controller based on the pulling, tugging or tension that’s delivered to the hitch when the host vehicle moves,” Wired reported.

The Pru then propels itself with an internal 240V DC motor to follow the car’s speed.

The PRU’s lithium-ion batteries and four-cylinder, 750-cc diesel generator could provide a range of 700 miles on six gallons of gas, to a 100 mile range EV. The PRU can also be used as a standalone charging unit.

Of course not everyone is going to want to haul a camper around every time they take a road trip — but think about the benefit of never having to run out of power. As of now, the PRU is estimated to cost $15,000.