Even as the big automakers start making plug-in electric vehicles, ALTe PowertrainTechnologies is one of many companies seeking to carve out a business converting fleet vehicles to plug-in hybrids.

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The Auburn Hills, Mich.-based company said today it has signed a partnership with Manheim, which sells autos through online auctions, to market retrofit trucks and vans to be extended-range electric vehicles.

ALTe Powertrain Technologies plans to convert trucks, such as a Ford F-150, into a hybrid and increase fuel efficiency by as much as 200 percent. The major components of its powertrain are a 20 kilowatt-hour lithium ion battery pack, generator, and hybrid controller.

The company projects that a truck can go 30 miles in all-electric mode and another 275 miles on charge-sustaining mode without loss of performance and increased torque compared to a V8 engine. It can be charged in 8 hours in a normal 110-volt outlet and 4 hours in a 220-volt outlet.

The partnership with Manheim will allow it to market the conversion service to fleet operators, ALTe Powertrain said in a statement.

Electric-vehicle conversions are considered a more costly way to make an electric vehicle. But fleet operators can save a substantial amount of money on fuel by going with alternative powertrains. Another company called XL Hybrids has developed a hybrid conversion kit for fleet operators with sedans.

Plug-in conversions are also important because sales of consumer electric vehicles will likely only be a small percentage of overall auto sales this decade. With 250 million vehicles on the road in the U.S. and 900 million globally, it will take 15 to 20 years for production plug-ins to replace the existing stock in significant numbers, said plug-in advocate Felix Kramer from CalCars.