While there have been huge strides made in battery technology in recent times, the limited range of electric vehicles remains one of the main barriers to their general adoption. While maybe not an ideal solution, Volvo is producing a few electric test vehicles with range extenders - combustion engines that increase the effective range of the electric vehicle by effectively turning it into a hybrid. The project, which is supported by he Swedish Energy Agency and the EU, will test three different electric motor/combustion engine combinations.

The three different technology combinations will all involve the installation of a three-cylinder combustion engine that can run on both petrol and ethanol (E85) and will complement the electric motor, which drives the front wheels. Two of the configurations being tested are based on the Volvo C30 Electric, while the third is based on the Volvo V60 Plug-in Hybrid. Volvo says all three concepts increase the vehicles' range by up to 1,000 km (621 miles).

Volvo C30 with series-connected Range Extender

The first concept sees a three-cylinder 60 hp (45 kW) combustion engine installed under the rear load compartment floor of the C30 Electric. The combustion engine is connected to a 40 kW generator with the power generated primarily used to drive the car's 111 hp (82 kW) electric motor. However, the driver can also choose to let the generator charge the battery pack, which has been reduced in size to make room for the combustion engine and its 40-liter fuel tank. The vehicle's battery pack alone provides a range of 110 km (68 miles).

Volvo C30 with parallel-connected Range Extender

The second concept fits the C30 Electric with a more powerful turbocharged 190 hp (142 kW) three-cylinder combustion engine at the rear. Unlike the first concept, the engine is connected in parallel to primarily drive the rear wheels via a six-speed automatic transmission when cruising on the highway. The engine can also be used to charge the battery via a 40 kW generator. The electric motor is the same 111 hp (82 kW) unit found in the first concept, which combines with the combustion engine to provide a total of more than 300 hp (224 kW), giving it the ability to accelerate from 0-100 km/h (62 mph) in under six seconds. The electric-powered range of the vehicle is 75 km (47 miles).

Volvo V60 with parallel-connected Range Extender

The third concept sees the entire drive package installed under the front bonnet. A 111 hp (80 kW) electric motor is supplemented with a three-cylinder petrol turbo engine producing 190 hp (140 kW), a two-stage automatic transmission and a 40 kW generator. Power from the combustion engine drives the front wheels via the gearbox and recharges the battery pack when required. Up to 50 km/h (31 mph), the vehicle is powered solely by electricity with the combustion engine kicking in at higher speeds. The combustion engine will also charge the battery pack when the charge level drops below a predetermined level. The battery pack located under the rear load floor provides a range of 50 km (31 miles), while the fuel tank is slightly larger than the other concepts at 45 liters.

"This is an exciting expansion of our increasing focus on electrification. Battery cost and size mean that all-electric cars still have a relatively limited operating range. With the Range Extender, the electric car has its effective range increased by a thousand kilometers - yet with carbon dioxide emissions below or way below 50 g/km," says Derek Crabb, Vice President Powertrain Engineering at the Volvo Car Corporation.

"These three projects allow us to evaluate the Range Extender's various possibilities. As with the C30 Electric and V60 Plug-in Hybrid, the goal is to make the cars exceptionally CO2-lean without compromising on customer requirements such as comfort, driving pleasure and practicality," added Crabb.

Volvo is due to begin testing of the various concepts in the first quarter of 2012.