August 11, 2014
At first glance, there's little that's attractive about the BMW i3, unless one is into simply being different. It's an awkward looking little beast that evokes images of a liaison between an AMC Pacer and a Pontiac Aztek.
It continues the theme inside, metaphorically beating one over the head with the fact that it is different, simply for the sake of being different. (To be fair, it's not the only new-technology leader to take this approach: witness the Toyota Prius!)
But get past the aesthetics and it becomes clear that the i3 is a very well designed car – so much so that it was the winner of the prestigious World Car Design of the Year award, as well as several other honours.
As it should be for it is a significant car. A very important car. A car that just may be the blueprint for the car of tomorrow, in concept if not in detail.
The i3, which arrived on the Canadian market earlier this year, is the vanguard of BMW's thrust to electrify its vehicles. But it is much more than just another electric car; an existing template to which an electric powertrain has been adapted.
In creating the i3, BMW's engineers took a holistic approach to addressing the challenges of the next decade and beyond, considering both the advantages and opportunities electric power presents and the disadvantages and constraints that work against it.
As a result, the i3 is designed in every respect both to exploit those advantages and to ameliorate the negative characteristics that often accompany them – a process that took seven years and more than 32-million kilometres of testing, involving more than 1000 people.
Freed from the constraints of an existing architecture and a conventional powertrain configuration, the i3 shares almost nothing beyond a philosophy with its BMW kin.
The differences start with the powertrain, of course. Motive power comes from a BMW-built synchronous electric motor with maximum output of 125 kW (170 hp) and peak torque, at start-up, of184 lb-ft.
Instead of being up front, where an internal-combustion engine (ICE) would normally sit, the motor is in the back, integral with the differential gear, where it does drive the rear wheels in traditional BMW fashion.
The transaxle offers only a single gear-ratio, effectively eliminating any form of conventional transmission.
Energy is stored in a high-voltage lithium-ion battery pack with a capacity of 18.8 kWh, located beneath the floor of the passenger cell. The battery pack, which comprises eight separate modules, each of which can be replaced individually, is kept at an appropriate operating temperature via the car's air-conditioning refrigerant, thus solving one of an electric vehicle's biggest challenges – battery overheating.
Another common EV challenge is the see-saw relationship between performance and weight.
Performance, of which driving range is an important component, can be improved by increasing motor and/or battery capacity. But doing so adds more weight, which then has a negative impact on performance. It's a catch 22!
To address that dilemma, BMW attacked weight as the enemy in every aspect of the i3's design.
Its chassis module, which contains the complete powertrain, steering, suspension and brake systems, is aluminum based. The passenger cell, in a break from common practice, is a separate structure rather than being built as a unit with the chassis – like the body on frame construction of days gone by, in principle if not in end result.
The passenger cell's core structure is made of lightweight, high-strength carbon-fibre-reinforced plastic (CFRP), similar to that used in Formula One and many other race cars. About a dozen plastic body panels are attached to that core structure, giving the car its form.
Differing from body and frame structures of the past, which were mechanically joined and isolated from each other via rubber body mounts, the i3's chassis and body units, though built separately, are then adhesively bonded together into an integral unit.
Once the BMW-proprietary adhesive is cured, which is said to take about 20 minutes, the two components cannot be separated. The resulting vehicle has a mass of just 1297 kg, as delivered in Canada – about the same as that of a Mini.
With its lightweight design and the instant torque delivery of its electric motor the i3 can accelerate from 0-to-100 km/h in just 7.2 seconds and complete an 80-to-120 km/h merging or passing maneuver in 4.9 seconds – numbers that make it more than competitive with most conventional vehicles.
Being battery powered, there's still the matter of driving range between recharges, however. BMW says is about 160 km, depending on conditions and that's more than most Canadians drive each day, the company says.
For those who drive further, or simply don't want to deal with range anxiety, there's a range extender option – similar in principle to that of the Chevrolet Volt.
Rather than using a normal automobile engine, however, the i3 adds a modified 650-cc, two-cylinder motorcycle engine that does nothing but drive a generator to keep the batteries charged in true series-hybrid fashion. The engine has no mechanical connection to the wheels.
Rather than being a different model, the range extender is offered as an optional add-on to what is otherwise a purely electric vehicle. With a 9-litre gas tank, it extends the driving range to about 300 km – not as far as most conventional vehicles will go but much closer to what is likely to be a customer-acceptable range.
Beyond the i3 itself, the holistic concept it represents is almost certain to be adopted by other automakers as well. Just think of the possibilities.
Instead of a motorcycle engine, what about using a compact rotary engine, or maybe a little gas turbine. Or replacing the batteries with a fuel cell in a similarly lightweight structure.
Yes, the i3 just may represent the default configuration for the mainstream car of tomorrow. I wouldn't bet against it.
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