Volvo has revealed plans to start testing extended-range electric cars in early 2012.
Range-extenders such as the Vauxhall Ampera and Chevrolet Volt are powered by an electric motor, but have a combustion engine that kicks in and powers the motor when the battery runs out.
Two of the Volvo development cars are based on the Volvo C30 electric car, which is due to go on sale in 2012.
The first test vehicle has a three-cylinder 60bhp combustion engine mounted under the boot floor. This is connected to a generator that powers a 110bhp electric motor and charges the battery. Volvo says that the car has a range in theory of up to 690 miles.
The second C30-based concept car has a turbocharged 187bhp engine, which primarily drives the rear wheels via a six-speed automatic transmission. In this model, the combined power of the combustion engine and electric motor is more than 300bhp, and blasts it from 0-60mph in less than six seconds.
Volvo's third range-extender car is based on the V60 and has both its petrol and electric motor mounted at the front of the vehicle. In this version, power from the combustion engine drives the front wheels and recharges the battery pack whenever necessary. The car is powered solely by electricity at speeds up to 31mph. The battery pack is mounted under the boot floor and gives a range of 31 miles on electricity alone.
'Battery cost and size means that all-electric cars still have a relatively limited operating range,' said Derek Crabb, vice-president of powertrain engineering at Volvo.
'With the range-extender, the electric car has its effective range increased by a thousand kilometres yet with carbon dioxide emissions below 50g/km.
Development and testing of the cars is being supported by the Swedish Energy Agency and the European Union, with funding worth more than 1 million.