At 3845mm in length, 2011mm in width and 1537mm in height, the five-door i3 is 120mm longer, 326mm wider and 132mm higher than the Mini One. It rides on a platform boasting a 105mm longer wheelbase at 2570mm and wider tracks. Therefore the i3 has a larger footprint than its Mini stablemate, yet it’s still smaller than any existing BMW model.
BMW claims the i3 boasts a “comparatively small turning circle” and keenly describes its handling as being “agile at typical city speeds”, both in keeping with its urban driving brief.
By mounting the new car’s liquid-cooled battery - a lithium-ion unit of unspecified weight and capacity - within the central section of the floor, BMW claims the i3’s centre of gravity is lower than all current 1-series models.
Unlike the petrol-electric, hybrid-powered BMW i8, the i3 relies on a pure electric driveline currently undergoing durability testing in a fleet of 1-series Active-E prototypes.
At the heart of the new plug-in system is a compact electric motor mounted over the rear axle. It draws energy from the battery to provide drive to the rear wheels via a single-speed transmission.
Development of the i3 kicked off in 2009 when trials of the Mini E (a testbed for the i3) began. The size of the electric motor has been reduced by 40 per cent since trials started and the trials have allowed the mounting of the i3’s drive unit – motor, power electrics, transmission and differential – to not impact on the interior.
With 168bhp and gutsy 184lb ft of torque, the brushless motor is claimed to propel the i3 from 0-37mph in 3.9sec and from 0-62mph in 7.9sec – acceleration roughly equivalent to the 118d. It is also claimed to possess 50-75mph rolling acceleration of just 6.0sec.
Maximum speed is limited to 93mph to protect the charge of the battery. “We could gear it to achieve a much higher top speed, but in the interests of range we have decided to cap it at a level we think will be sufficient for most needs,” a BMW insider told Autocar.
The i3’s dynamic properties have yet to be revealed, but expect a drag co-efficient of well below 0.30 as the i3 gets skinny low-resistance tyres and does without drag-inducing cooling ducts.
BMW claims a total recharge time of the battery pack in six hours on a conventional 220 volt mains charge. An 80 per cent capacity in one-hour fast charge is also available. A heavy-acting brake-energy recuperation system also features, as does a ‘coast mode’ that can be used for periods of energy-neutral freewheeling.
An overall range of between 80-100miles is expected for the i3, which BMW believes is sufficient for 90 per cent of journeys. But BMW has revealed for the first time, the i3 will be offered with an optional range extender powertrain (called REx by BMW) to satisfy those wanting to undertake longer journeys.
The unspecified petrol engine will be packaged alongside the electric motor with the rear-axle assembly. It will be used to power a generator to maintain the battery charge. Unlike the i8, the combustion engine does not provide direct drive to the rear wheels, serving only to create electricity to run the electric motor.
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