Honda also will install lithium ion batteries in a new two-motor hybrid system debuting next year in the United States for mid-sized plug-in hybrids.
Honda hasn't said what car gets it first. But engineers are testing the system in an Accord. A suitcase-sized lithium ion battery pack sits behind the back seat, eating trunk space.
An engineer involved with the project said testing is expected to continue through year end, and the company must decide if the 15-mile range in electric-only mode is sufficient. If user feedback suggests more range is needed, Honda will have to make the battery bigger or cut the car's weight, he said.
"We think a 15 mile range satisfies about 70 percent of the users," he said.
Already, Honda has tweaked the plug-in version of the Accord with an aluminum hood and other weight shavings. But the plug-in still weighs 330 pounds more than its gasoline counterpart.
Honda is rolling out the new hybrid system to counter criticism that its current technology is too weak to provide extended electric-only travel. The Integrated Motor Assist system used in the Insight, Civic and CR-Z hybrids uses the electric motor mostly to assist the gasoline engine.
The new system uses one traction motor to move the car and one generator motor to recharge the battery. The former, a 120-kilowatt motor, is combined with a 2.0-liter, four cylinder engine and continuously variable transmission.
The car has a top speed of 62 mph in electric-only mode, but a big question will be how far it can travel at that speed. The Accord plug-in hybrid can recharge in four hours from a 100-volt source or in 1.5 hours from a 200-volt source, the engineer said.
Honda President Takanobu Ito said last fall that the new hybrid system for larger vehicles will give electric-gasoline drivetrains a bigger slice of Honda's global sales -- pushing hybrids to around 10 percent of global sales by 2015, from less than 5 percent in 2009.
The electrified powertrains also will feature prominently in the Acura lineup, Ito said, reinforcing what he calls the "smart premium" image to which the brand aspires.