A diagram of AFS Trinity's technology, which uses ultracapacitors to store energy for short periods of time, releasing it in quick bursts to give the engine extra power.

A Bellevue company that has developed a way to preserve battery life in plug-in hybrid vehicles, extending their range of travel, has won a patent on its underlying technology.

The company, AFS Trinity Power Corp., is now asking Congress to create a new way for people who buy plug-ins to qualify for a federal tax credit of as much as $7,500. The credit is now based on the capacity of the vehicle’s batteries; the idea is to expand the options for meeting the requirement to take into account the distance a car can travel on a charge.

AFS is seeking to license its technology to major automakers for use in plug-in hybrid vehicles. Its approach uses a combination of batteries and ultracapacitors, which store energy for short periods of time, releasing it in quick bursts to give the engine extra power.

The company was awarded a U.S. patent on its technology in June.

The tax credit is next on its list of challenges to tackle. The company says that amending the requirements for the credit could create incentive for efficient technologies regardless of battery size, with the potential to spark innovation more broadly across the industry.

The current credit’s focus on battery capacity penalizes more efficient approaches, said Ed Furia, AFS Trinity CEO and chairman. For example, a prototype developed by the company can travel 40 miles or more using batteries with capacity of 8 kilowatt hours — as far as General Motors’ Chevy Volt can travel on its capacity of 16 kilowatt hours. But Volt buyers would be eligible for the full $7,500 tax credit, while buyers of cars using AFS technology would receive a smaller credit.

AFS doesn’t want to reduce the benefit for Chevy Volt buyers, Furia said, but rather create an additional means of achieving the full credit. Other energy-efficient vehicle technologies that might also benefit would include low-resistance tires, advanced aerodynamics and lightweight carbon-fiber materials.

“Good tax policy and good energy policy would be to have a tax credit be technology-neutral, so that the tax credit would tie into something you can measure no matter the technologies employed in the car,” Furia said. “The whole idea is to get as much electric-only range as you can. The highest and best use of a plug-in hybrid-electric vehicle is how far it can go on electric-only mode, and you use the fuel side of the plug-in hybrid really as a range extender.”

Furia wrote last month to Senate Majority Leader Harry Reid, House Speaker Nancy Pelosi and other congressional leaders calling for such a change in the legislation. The argument has merit, said Robert Kellar, spokesman for Rep. Jay Inslee (D-Bainbridge Island).

“The way the tax is structured now, obviously it rewards a particular technology,” Kellar said. What’s important, he said, is the goal of getting polluting vehicles off the road, regardless of the specific technology used to achieve that goal.

Previously: Electric vehicles: The distribution challenge for utilities