By Christopher A. Sawyer
The Virtual Driver

(July 14, 2013) The i3 is BMW’s first ground-up electric vehicle for public sale. Whether or not it will be a commercial success is something that the future will decide. However, the level of technology to be found in this rear-engine/rear-drive EV surpasses anything on the road, and brings structural carbon fiber to volume automotive production in concert with both aluminum and magnesium.

BMW used its electrified Mini and 1 Series lease programs to develop the drive technology used by the i3. Not only were the engineers able to prove-out the mechanical pieces involved, they developed a “single pedal control concept” that uses the idiosyncrasies of electric drive to get the greatest efficiency possible out of the charging system. And despite it’s accuracy, it’s still an odd name for a car that has two pedals.



In a nutshell, software sets the regeneration and braking levels based on vehicle speed and need. Regeneration is the heaviest in the city, with an aware driver able to coast to a stop without ever having to touch the brake pedal. At higher speed, a lift off the throttle causes a light “drag” that slows the i3 at a much less aggressive rate, but still puts energy back into the batteries through regenerative braking.

Should demand warrant, the driver can use the brake pedal to activate the power-assisted four-wheel disc brakes, and increase the vehicle’s retardation rate. Based on a drive in an electrified Mini, the in-city regeneration rate can be dramatic, though you can soften its response by easing out of the throttle gradually as you coast to a stop.

The brake pedal is then used only to hold the car in place at a stop. Based on the Mini’s energy gauge, the amount of energy returned to the battery as the electric motor switches from drive to generator mode is greater than a driver could expect to consistently attain with a more driver-oriented, passive system. Switching between Comfort, EcoPro and EcoPro+ modes adjusts the regeneration rate, with each getting progressively greater. When this reaches a level equal to that which would be provided by the braking system, the brake lights illuminate.

The lightweight structure that holds everything together is divided into two sections, the Life module and the Drive module. Hence the silly run-together name. Basically, the four-seat upper structure, with its conventional front and suicide-style rear doors, is made from carbon fiber, and the lower unit from aluminum. Together their weight reduction compensates for the weight of the 22 kWh battery pack located under the passenger cell. Even the bodywork is lightweight, made from fiberglass-reinforced injection moldings said to be 30% lighter than sheet steel panels. This, however, is just the beginning:

    By placing the power electronics and electric motor in the rear, the length of the cabling required to connect these elements was reduced. This cut the overall weight of the drivetrain by three pounds.
    The use of forged aluminum for the suspension links cut their weight 15%.
    Making the driveshaft hollow reduced its weight by 18%.
    The standard 19-in forged aluminum wheels are 36% lighter than comparable steel rims, and weigh only 15 lb each.
    Magnesium is used for the instrument panel’s support structure, dropping part weight by 20%, and allowing a reduction in the number of components. This cut another 10% off instrument panel weight.
    To the chagrin of future restoration buffs, many of the screws and bolts are made from aluminum.
    Force-flow geometry was used to optimize the geometry and weight of the cast-aluminum windshield wiper mount, and the wiper blades have a honeycomb inner structure to further reduce weight.

The i3 is built on a relatively long 101.2-in wheelbase, which gives more than enough room between the aluminum Drive module’s rails to place the 96 cells of the 450-lb, 22 kWh lithium-ion battery pack. This weight is carried low and within the wheelbase, the ideal place for vehicle responsiveness and handling. It also eliminates the need for a central tunnel, and gives the i3 a flat floor.

By placing the motor in the back, between the rear wheels, the engineers were able to make the i3 rear-drive, and cut front overhang. The smaller front structure provides greater room for crash energy absorption than would be possible if the motor was placed up front. In addition, the rear mounting places the optional range-extender two-cylinder gasoline engine from BMW’s CT650 GT scooter behind the passenger compartment where noise and heat are easier to control. With that engine in place, the range for the i3 increases approximately 60 miles. A 2.4-gallon fuel tank is carried in the nose of the vehicle to feed it.

    The BMW-developed hybrid synchronous electric motor produces 170 hp and 184 lb-ft of torque, and has an 11,400 rpm redline.
    Motor weight: 110 lb.
    The liquid-cooled BMW-produced 22 kWh lithium-ion battery pack has eight modules of 12 cells each, and a rated voltage of 360 volts.
    Damaged cell modules can be replaced individually in case of fault or failure.
    Optimum operating temperature for the battery is 70˚F.
    Battery lifetime: Life of the vehicle (est.).
    An available heat pump-style interior heating unit uses up to 30% less energy than conventional electric heating.
    Charging is via a home BMW-sourced charging station, public charge port with a SAE J1772 connector, or public DC fast-charge (50 kW)unit.
    The optional rear-mounted 650 cc, 34 hp range extender gasoline engine drives a generator to produce electricity, but does not drive the car directly.
    Estimated performance:

0-60 mph: 7.2 seconds.
50-70 mph: 4.9 seconds.
Top speed: 93 mph.

The suspension is fairly conventional with a single-joint MacPherson strut front mated with a five-link independent rear suspension that mounts directly to the Drive module. What really stands out are the 19-in alloy wheels carrying 155/70R-19 tires. Compared to what most cars carry today, these things look like they belong on a Conestoga wagon! The tires are narrow to cut both air and rolling resistance, two important items when more energy isn’t right around the corner at the next filling station. However, BMW says that the wheel diameter more than compensates for the lack of width and gives the i3 a contact patch that is similar to that found on a conventional vehicle. To keep everything right-side up, the i3 comes with BMW’s DSC electronic stability control system, ABS, Cornering Brake Control, Brake Assist, Brake Standby, Start-off Assistant, brake Fading Compensation and Brake Drying, as well as Dynamic Traction Control.

Though this is a lot of electronics looking over the driver’s shoulder, it’s doubtful they will be used in any other manner than sparingly. That’s because the i3’s low center of gravity, long wheelbase and wide stance should make it feel very stable. Coupled with an electric motor that produces 184 lb-ft of torque the minute it starts to turn, electro-hydraulic steering with 2.5 turns lock-to-lock and a solid base to which the fully independent suspension is attached, the i3 should feel like a rear-drive Mini Cooper. Especially with its 32.3 ft turning circle.

Connectivity and Range Anxiety

Driver assistance and mobility services will be offered through BMW ConnectedDrive, including ways for drivers to create mobility plans that ease range anxiety. These can be accessed via a SIM car that is built into every i3, and include Concierge Service as well as an Intelligent Emergency Call function. Customers can use ConnectedDrive to guide them to their destinations along the most efficient path, plot routes from home to a parking space, ask for assistance in changing to the correct public transportation, and even help with directions if the driver completes the trip on foot.

The optional navigation system also includes specially developed ConnectedDrive services. These include a Driving Range Assistant for both route planning and the current journey. If the destination you select in the navigation system lies beyond the vehicle’s current range, it suggests switching to the ECO PRO or ECO PRO+ mode, as well as calculating a more efficient alternative route. If the battery has to be recharged at a public charging station, it gives the driver a choice of available stations nearby. By taking into account a number of factors (route, distance, driving style, battery charge, electricity use for comfort functions, driving mode, topography, current traffic conditions and outside temperature), the navigation unit is capable of providing a dynamic display of the vehicle’s range as you drive. The dynamic range is shown as an overlay on the navigation system’s map, taking the current location as the starting point, and displaying all of the points that can be reached arranged in the form of a spider chart overlay.

ConnectedDrive services can pinpoint suitable and available charging points along the route or near your destination on the map, much as points of interest are currently displayed. It also can tell you if a charging station will be available when you get there, and calculates the charging time required before you can make a return trip or carry on to a new destination.

Android and iOS-equipped smart phones can use the Remote app to access vehicle data and route planning information at any time. In addition, you can search for charging stations that are either full or have spaces, and see if they are located within your current driving range. If plugged into a BMW or public charging station, the app can be used to control charging either remotely or through a timer. If it is, the car can be pre-heated or cooled. This makes for optimal range when the charging is complete. Also, the app can be used to set off-peak charging.

Though pricing has yet to be announced, you can expect the i3 to start at $35,000. This places it in direct competition with Ford’s slow-selling Focus Electric, a car that has a 24 kWh battery pack, many similar functions and a near 90-mile range. It is built on the same line as the rest of the Focus lineup, and uses steel instead of aluminum and carbon fiber for its structure.

The Nissan Leaf, which takes the front and rear of Nissan-Renault’s B platform, grafts it to a flat-floored center section containing the batteries, and clothes it in unique bodywork, is several thousand dollars cheaper. Neither, however, has the technical or social cachet of BMW’s little electric. Whether that results in a sustainable sales volume remains to be seen.

The Virtual Driver