At launch time, BMW i3 is also available with a range-extender engine, which maintains the charge of the lithium-ion battery at a constant level while on the move as soon as it dips below a certain value. Performing this role is a 650cc two-cylinder gasoline engine developing 34 hp/25 kW, which is mounted immediately adjacent to the electric motor above the rear axle. Specifying the range extender has no effect on luggage capacity: the 2.4 gallon (nine liter) fuel tank is located in the front section of the car.
The combustion engine drives a generator to that produces electricity. It is brought into play as required, responding optimally to match the load and running extremely efficiently. Driving in ECO PRO mode or ECO PRO+ mode can increase the range of the BMW i3, in each case by up to approximately 12 percent. And if the range extender is specified, the BMW i3 will be able to travel more than 60 miles (100 km) further before refueling. The BMW i3 is the world’s first electrically powered car to offer the option of a range extender engine used exclusively to generate electric power.
Here is how the BMW i3 with Range Extender behaves on the road:
On quicker A-roads, the i3 has a very impressive pace under full acceleration. Long uphills are demolished in fine style, with a seamless stream of torque (thank the combination of an electric motor and a single-speed transmission). The i3 also has remarkable stability, as a series of driving exercises at Brands Hatch prove. Sharp lane changes and even a stretch of hilly circuit in the pouring rain fail to ruffle the i3, even though it has 155/70 tyres at the front and 175/70s at the rear.
On the return leg to central London, the range extender activates, allowing it to cut in and out as required by the conditions. It is just about possible to hear it running – the sound is of a very distant thrum – and then probably only because the cabin of the i3 is so very quiet. The i3 also has pre-set levels of regenerative braking. It’s quite an aggressive setting that slows the car quickly once the driver lifts off the accelerator.
In terms of low-pollution fossil fuel running, the use of this small petrol engine is a masterstroke with, for example, emissions of unpleasant NoX gas at just 0.0009 g/km. You have to wonder whether the electricity created by the i3’s range extender is ‘greener’ than what the average power station can manage. With a full battery and fuel tank of fuel, BMW predicts a real-world range of between 150 and 186 miles and claims CO2 emissions of 13g/km.
There are downsides to the i3. After the price (although the standard spec in ‘Standard’ trim is pretty comprehensive), the main one is probably the restricted space in the back (and tight boot) and the fact that the rear suicide doors cannot be opened without the front door being opened first. Many will find this problematic on the school run. The tiny fuel tank means that long journeys will mean refueling as often as every 80 miles. Otherwise front seats are also rather flat and need bolsters considering the i3’s handling abilities.