Plug-In Supply, a one-year-old company, has lined up dealers and begun selling its plug-in hybrid conversion kits, owner Robb Protheroe told Greentech Media this week.

The Petaluma, Calif.-based company is selling conversion kits based on advocacy group CalCars’ open-source technology. Plug-In also unveiled its Toyota Prius plug-in hybrid kit at the Plug-In 2008 conference in San Jose, Calif. this week. 

Plug-In Supply has already shipped 30 systems since the beginning of the year – to customers as far flung as Italy and Australia – and is now working to build a second batch of 100 kits, Protheroe said.

The company sells two different 5-kilowatt kits that it claims can increase fuel economy to up to 100 miles per gallon. The first one uses lead-acid batteries, which can travel 10 to 15 miles on the electric motor alone, and cost $4,995. The other one uses lithium-iron-phosphate batteries, which deliver an all-electric range of 20 miles, and cost $11,000 each.

The lithium-ion-phosphate battery has an expected life of more than 11 years, while the lead-acid battery has an expected life of more than two years. Both kits fit 2004 to 2008 Prius models and are fully charged in six to eight hours using a standard 110-volt wall outlet.

Plug-In Supply has been signing up dealers across the United States. The company has inked contracts with eight companies in locations that include San Francisco, Tampa, Chicago and Detroit. The company expects to add another four or five in Seattle, Portland and elsewhere, Protheroe said (see a dealer list here).

“We’re just keeping a low profile,” he said. “But now we’re in our final configuration and we’re ready to do higher volume.”

The company plans to increase its production in the beginning of August so that it could make about 40 per month, depending on demand, Protheroe said.

Plug-In Supply already has a backlog of about 50 orders, he said.

The company does face some challenges, including an increasing number of competitors and a proposed state policy that would increase the cost of plug-in conversion companies to do business in California (see Will Emissions Testing Stifle Plug-In Hybrids? and Can Hymotion Convert the Auto Industry?).

Plug-in conversion advocates hope they will get more support from Congress, which is considering a farm bill that originally included provisions to provide tax credits for converting hybrid vehicles.

Although the latest version of the bill no longer contains the tax credits, plug-in conversion supporters are working on bringing the incentives back,” said Genevieve Cullen, vice president of the Electric Drive Transportation Association, at a Plug-In 2008 panel Wednesday.