BMW unveils the production i3 in New York, London and Beijing; efficiency, dynamics and a supporting ecosystem of services
|The production version of the i3. Click to enlarge.|
In a simultaneous—and video linked—unveil in New York, London and Beijing, BMW introduced the production version of its i3 battery-electric vehicle on Monday. (Earlier post.) The i3 is the first series-production vehicle out of BMW’s i brand, and is purpose-built around an electric powertrain to serve needs of megacities customers, said Dr. Norbert Reithofer, Chairman of the Board of Management of BMW AG, during his remarks in New York. With its new architecture, use of carbon fiber reinforced plastic, and premium mobility service offerings, the “i3 marks the beginning of a new mobility age,” said Dr. Reithofer.
On a full lifecycle basis, with an average European electricity mix, the i3 offers approximately a 30% lower carbon footprint over 150,000 km (93,200 miles) of use than the fuel-efficient diesel-powered BMW 118d, said Dr. Julian Weber, head of Innovation Projects e-Mobility at BMW. With a renewable electricity mix, that increases to about 50%. EVs in general currently have a larger carbon burden in the production phase than conventional vehicles (e.g., earlier post), but gain their advantage in the use phase. The crossover point for the i3 vs. the 118d is at about 50,000 km (31,000 miles), Dr. Weber said.
(In addition to being extremely fuel-efficient, the 118d is produced on the next line over to the i3 in Leipzig, making it a good reference baseline, Dr. Weber said.)
The i3’s architecture is based around the LifeDrive structure with a carbon-fiber reinforced plastic (CFRP) passenger cell and aluminum module encompassing the powertrain, battery and chassis. The passenger cell is attached to the aluminum drive frame (giving a more modern slant to body-on-frame design). A robust thermoplastic outer skin is attached onto this compartment, allowing extensive freedom in design. This two-way split (passenger cell and drive frame) is reflected in the design of the BMW i3—both the exterior and interior make a feature of this structural characteristic through the visible layering and intertwining of different surfaces.
The use of lightweight, durable and crash-safe CFRP on this scale is unique in volume car production, BMW emphasized, underscoring its commitment to developing the material as an advanced, light-weight option for vehicles. (At the launch event, BMW had representatives from SGL, its carbon fiber partner, and Boeing, which uses carbon fiber extensively in the new 787, participating in a general discussion on the benefits of the material.)
By using CFRP, BMW was able to offset the additional 230-250 kg (507-551 lbs) of weight from the i3’s battery pack—its DIN curb weight stands at 1,195 kilograms (2,635 lbs).
The use of CFRP in the construction of the passenger compartment allowed BMW to dispense with B-pillars, making access to the two rows of seats extremely easy via the “coach” doors.
eDrive. The BMW i3 uses the BMW eDrive rear-wheel drive powertrain previously found on the BMW ActiveE (but the i3 is significantly lighter). The electric motor, power electronics and high-voltage Li-ion battery pack (except from the component cells, which are sourced externally) were developed internally by the BMW Group under its eDrive program.
The electric motor generates a maximum output of 125 kW/170 hp and peak torque of 250 N·m (184 lb-ft), delivered to the rear wheels via a single-speed transmission. The electric motor and transmission unit are located in direct proximity to the driven rear axle.
The motor has power consumption of around 0.129 kWh per kilometer (0.21 kWh hours per mile) in the New European Driving Cycle (NEDC); with the range extender, this figure increases to 0.135 kWh/km. (Although not a solid comparison due to drivecycle differences, the new Chevy Spark EV is EPA-rated for electricity consumption of 0.28 kWh/mile.) The i3 accelerates from 0 to 100 km/h in 7.2 seconds, and 0 to 60 km/h in 3.7 seconds.
The 22 kWh Li-ion pack is integrated below the floor—the i3 has no tunnel or center console. The lower center of gravity of the i3 and 50:50 weight distribution make an additional contribution to the car’s handling. The battery gives the car a range in everyday conditions of 130 – 160 kilometers (81 – 99 miles) when fully charged from a conventional domestic power socket, BMW i Wallbox or public charging station. The i3 will also offer the SAE combo fast charger; when the BMW i3 is plugged into a modern public fast-charging station (50 kW) it takes about 30 minutes for the battery to reach 80% capacity.
The design principle behind the electric motor (earlier post) in the BMW i3 helps it to run extremely effectively across a wide load band. The motor’s average power consumption of around 0.13 kWh per kilometer (0.21 kWh per mile) in the New European Driving Cycle (NEDC) plays a key role in optimizing the car’s range.
The high-voltage battery in the BMW i3 consists of eight modules (each with 12 individual cells), which together produce a rated voltage of 360 volts and generate approximately 22 kWh of energy. The battery management system controls both the charging and the discharging processes, as well as the operating temperature of the cells. When the vehicle is on the move all the cells are used equally to supply energy. However, it is also possible to replace individual modules in the event of a fault.
The air conditioning coolant cools the high-voltage battery, and this fluid can also be warmed using a heat exchanger. All these characteristics enable the optimum operating temperature of around 20 ° Celsius to be reached before a journey begins, even when the ambient temperature is low.
The BMW Group has planned and developed this battery to last for the full life of the vehicle. The battery warranty is valid for eight years or 100,000 kilometers (62,000 miles).
The high-voltage battery also benefits from the deformation properties of the CFRP Life module. In the side crash test, the pole does not penetrate as far as the battery. The mix of materials used and the intelligent power distribution in the LifeDrive module ensure that the high-voltage battery is optimally protected even in the side sill area.
A range of systems and measures have been implemented in the vehicle that ensure safety in normal operation and in the event of accidental fires. The high-voltage system is designed to cope with accidents beyond the legal requirements, with the high-voltage battery including features that ensure its safe reaction even in situations such as this.
To ensure maximum safety in a crash scenario, the high-voltage battery is disconnected from the high-voltage system and the connected components discharged when the passenger restraint systems are triggered. This safely prevents the possibility of a short circuit, which could lead to electric shocks or cause a fire.
The power electronics, also developed in-house by BMW, serve both as an inverter for the power supply from the battery to the electric motor and as a voltage transducer interacting between the high-voltage battery and the 12-volt onboard power system. The battery charging systems is also integrated into the power electronics, which regulate charge outputs of between 3 kW and 50 kW, depending on the electricity source.
Range extender. The 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 mounted immediately adjacent to the electric motor above the rear axle. Specifying the range extender has no effect on luggage capacity—the nine-liter (2.4 gallons US) fuel tank is located in the front section of the car—but it does add about 330 lbs (150 kg) to the vehicle curb weight.
The combustion engine develops maximum output of 25 kW/34 hp and torque of 55 N·m (41 lb-ft) and only drives a generator. It is brought into play as required, responding optimally to match the load and running extremely efficiently. Battery-electric driving in ECO PRO mode or ECO PRO+ mode can increase the range of the BMW i3, in each case by around 20 kilometers (12 miles). If the range extender is specified, the BMW i3 will be able to travel more than 100 kilometers (more than 60 miles) further before refueling. Maximum range stands at approximately 300 kilometers (186 miles). The BMW i3 currently is the first electrically powered car in series production with a range extender engine used exclusively to generate electric power.
A version with the range extender was not on display at the launch. (As a visual cue, the pure battery-electric version only has the recharging port; an i3 with the range extender will also have a fueling port on the front quarter.)
More on lightweight design. In addition to the LifeDrive architecture, the principle of lightweight design also governs the aluminium drive module and the connection between the two elements. The body structure—shaped by its LifeDrive architecture—enables the use of a trailing edge element made by glass-fibre-reinforced plastic injection moulding. And that contributes a 30% weight saving compared with a conventional sheet steel solution. The direct connection between the power electronics and electric motor in the rear of the BMW i3 reduces the length of cabling required and cuts the overall weight of the drivetrain by around 1.5 kilograms (3.3 lbs). Weight-minimizing construction also sets the tone for the chassis components of the BMW i3.
For example, the forged aluminium suspension links weigh around 15% cent less than in a conventional design, the hollow drive shaft is 18% lighter than a conventional equivalent, and the standard 19-inch forged aluminium wheels of the BMW i3 are 36% lower in weight than comparable steel rims of the same size.
Using a magnesium supporting structure for the instrument panel saves weight on two fronts. Superior material attributes over conventional sheet steel allow these components to boast optimized geometry, which results in a weight reduction of some 20%.
In addition, the high composite rigidity of the magnesium supporting structure lends it a strengthening effect, which allows a reduction in components and lowers weight by a further 10%. The door trim panels are made from renewable raw materials and tip the scales around 10% lighter than conventional equivalents. And the application of the lightweight design strategy also extends to screws and bolts made from aluminium.
Production. The production of the BMW i3 consumes around 50% less energy and around 70% less water in comparison with the current average figures for production in the BMW Group. One reason for this is the elimination of the metal stamping process for body components (due to the use of the CFRP passenger cell) and the elimination of the painting phase of production. All the electricity used to produce the BMW i models at the Leipzig plant is wind-generated. (The production of the i3 marks the first time an automobile manufacturing plant in Germany has installed wind turbines on site to directly power production.) The SGL carbon fiber plant at Moses Lake, Washington, uses 100% hydropower.
Production of the carbon fibre raw material for the i3 takes place at a BMW/SGL joint venture plant in Moses Lake. This plant is integrated into the BMW i production and value chain and provides the BMW Group with a secure supply of high-quality, sustainably produced raw materials for the production of CFRP components. Around US$100 million has been invested in the Moses Lake carbon fibre plant to date. To make sure the BMW i3 can go into production on schedule at the end of 2013, the plant has been producing fibres ever since the end of 2011. The two production lines in Moses Lake currently each have a capacity of 1,500 tonnes a year – which means the plant already accounts for around 10% of global CFRP production today.
The factory in Moses Lake produces carbon fibres from a polyacrylonitrile-based thermoplastic textile fibre precursor. In a complex multi-stage process, the various constituent elements of the fibre are removed by gasification, eventually leaving a fibre that consists of virtually pure carbon with a stable graphite structure.
The resulting carbon fibres are seven microns thick. For automotive application, approximately 50,000 of these individual filaments are bundled into so-called rovings or heavy tows and wound on reels, prior to further processing. In addition to automotive applications, fibre bundles of this thickness are also used, for example, in large rotor blades for wind turbines.
The rovings are sent to the joint venture’s second site, at the Wackersdorf Innovation Park in Germany, for industrial processing into lightweight carbon fibre laminates. In contrast to a woven fabric, in these laminates the fibres are not interlaced or interwoven, but all lie in the same plane. Weaving would kink the fibres and detract from their special properties. The fibre orientation in the laminate is crucial to achieving optimal quality in a CFRP component.
Following an investment of €20 million (US$27 million), several thousand tonnes of carbon fibre laminates can be manufactured annually at the Wackersdorf site. These laminates form the raw material for the manufacture of CFRP parts and components at the BMW plants in Landshut and Leipzig.
At the CFRP press shops in Landshut and Leipzig, the carbon fibre laminates supplied from Wackersdorf are processed into CFRP body parts. Over the past 10 years, the BMW Group’s CFRP specialists have steadily refined and automated the CFRP production process at the Landshut plant so that, for the first time, it is now possible to mass-produce CFRP body components cost-efficiently to a high quality and with high process stability. CFRP roofs for the BMW M3 and M6 models and the bumper supports for the M6 have already been in mass production in Landshut for some time.
Following an investment of €40 million (US$53 million) and the start of carbon component production in March 2012, the Landshut site is now the key innovation and production center for CFRP components.
The new press shop in Leipzig is equipped with technology for the manufacture of CFRP automotive components; here, BMW now produces its own carbon fibre composite materials. Properties such as the formulation, strength and geometry of the CFRP parts can be adapted to suit design requirements.
At the initial “preforming” stage, the pre-cut carbon fibre laminate supplied by the Wackersdorf plant begins to acquire a shape. During this process a heat source is used to give a fabric stack a stable, three-dimensional form. Several of these preformed stacks (preformed blanks) can then be joined to form a larger component. In this way CFRP can be used, for example, to produce components with a large surface area that would be difficult to manufacture from aluminium or sheet steel.
Preforming and preform joining are followed by the next stage in the process: high-pressure resin injection using Resin Transfer Moulding (RTM). This technique, used in the aerospace industry, shipbuilding and the manufacture of wind turbine rotors, involves high-pressure injection of liquid resin into the preforms. As the fibres and the resin bond, and in the subsequent hardening process, the material acquires the rigidity which is key to its outstanding qualities.
Working to precisely defined time, pressure and temperature parameters, the CFRP presses apply a clamping force of up to 4,500 tonnes, until the resin and hardener are fully cross-linked and the resin is hard. BMW’s own special manufacturing process eliminates the need for an additional time-consuming hardening process in a separate oven, which would normally be required for newly formed CFRP parts.
This new press shop, specially designed for CFRP, has little in common with a conventional sheet-steel press facility. It enables a leaner production structure which is also reflected in terms of investment costs. For example, construction costs are significantly reduced by the fact that a conventional paint shop and cataphoretic immersion priming are not required. Newly formed parts can leave the press in less than 10 minutes.
The new CFRP composite components produced in the new Leipzig press shop and the CFRP components supplied from the Landshut press shop then make their way to the new car body shop. The basic structure of the Life module of a BMW i3 comprises around 150 parts, a third of the number required for conventional sheet-metal architecture.
In a BMW-developed assembly process, the individual components are positioned 1.5 millimeters apart at the bond line gap in order to ensure optimal strength of the resulting joint. This precision ensures perfect transmission of forces between the individual CFRP components and therefore the highest level of volume production quality. The total length of bonded joints per vehicle is precisely predetermined, at 160 meters (20 millimeters width).
The newly developed adhesive used in CFRP production in Leipzig is workable for only 90 seconds after being applied to a component, before adhesion begins. An hour and a half later it is hard. This represents a tenfold acceleration of conventional adhesive hardening times. In order to further reduce the hardening time to below 10 minutes, BMW has developed a supplementary thermal process. This involves heating specific points on the CFRP parts to be bonded, thereby further accelerating the hardening process by a factor of 32.
The high-strength CFRP passenger cell (Life module) produced in Leipzig then passes from the body shop to the new assembly shop where it is united with the aluminium Drive module. The basic Drive module supplied by Dingolfing and built up in Leipzig is now bolted and bonded inseparably to the Life module. Only then is the CFRP Life module fitted with its outer plastic skin. The painted multi-piece skin consists mainly of injection-moulded thermoplastics such as those also used in conventional vehicle manufacturing (front/rear apron, side sill etc.). During final assembly, the colored plastic moldings are bolted to the inner cell of the Life module at special mounting points that cannot be seen from the outside.
The BMW Group production network builds the BMW i3’s electric motor and battery. At its Dingolfing and Landshut plants in Lower Bavaria, the BMW Group has created a “competence network” for electric mobility. The BMW plant in Dingolfing produces the battery, the transmission and the aluminium Drive module structure, while the BMW Landshut plant produces CFRP components for the Life module, plastic exterior parts, castings and the cockpit of the BMW i3.
Closed-loop CFRP recycling. In the course of development work on the BMW i, the BMW Group devised a world-first commercial-grade recycling concept for CFRP components, body components and segregated production waste. Using various methods, high-grade materials from the production process and even from damaged or end-of-life vehicles are reused, being either fed back into the vehicle production process or used in other applications.
In the recycling process, a distinction is drawn between “dry” recycling of non-resin-impregnated carbon fibre and “wet” recycling of resin-impregnated components. Dry carbon offcuts from the production process can be reprocessed into high-grade non-woven fabrics and reused in the manufacturing cycle. Secondary (recycled) material already accounts for around 10% of the carbon fibre used in the BMW i3. This process is the first of its kind in the global automotive industry.
For the recycling of resin-impregnated carbon fibres, CFRP is first separated industrially from the other plastics and processed in a pyrolysis facility. The process heat from the breakdown of resins is used to separate the undamaged carbon fibres. These fibres can then be used to manufacture new components, thereby reducing the consumption of new fibre. The rear seat pan, for example, is made from such recycled carbon fibre. It fully meets the BMW quality standard and weighs 30% less than a seat made from conventional fiberglass matting. Ground or cut into short fibres, the recycled CFRP or carbon fibres are also used in many areas outside the automotive industry, for example in the textile and electronics.Driver assistance systems and mobility services. The launch of the i3 also represents the launch of a supporting ecosystem, multiple BMW speakers emphasized at various times during the presentations. This includes BMW Connected Drive and the 360° ELECTRIC services, some of which are options.
Navigation services have been purpose-developed with the demands of electric mobility in mind for the BMW ConnectedDrive portfolio unveiled in 2013. These include mobility services, such as the Concierge Services for information and the Intelligent Emergency Call function, along with driver assistance systems that make an effective contribution to enhancing the convenience and safety of urban mobility. Access to the BMW ConnectedDrive services is ensured by a SIM card that comes built into the vehicle as standard.
The Driving Assistant Plus that is optionally available for the BMW i3 comprises Collision Warning with brake priming function, which is activated at speeds up to 60 km/h (approx. 37 mph) and is able to respond to both moving and stationary vehicles ahead, as well as to pedestrians. It also comes with Active Cruise Control including Stop & Go function. In addition to visual and audible warnings, the system is furthermore capable of braking the vehicle by itself, if required, with up to maximum stopping power.
The Parking Assistant can likewise be found on the list of optional extras and performs the steering manoeuvres at the same time as controlling accelerator, brake and gear selection, enabling fully automated parallel parking of the BMW i3.
There is also the option of a rear view camera for the BMW i3 to supplement the standard Park Distance Control (PDC) with rear sensors. Another optional extra is the Traffic Jam Assistant that allows drivers to delegate the tasks of pulling away, braking and steering to keep the vehicle in lane. Meanwhile, the Speed Limit Info system is also offered in conjunction with the navigation system.
The various mobility services from BMW ConnectedDrive and 360° ELECTRIC that have been specially developed for BMW i focus on the aspects of navigation and energy management. The exchange of information between driver and vehicle allows the current mobility requirements to be checked against the available energy resources.
Drivers can use the BMW i Remote app to share information with their car at any time using their smartphone. The pedestrian navigation function guides the driver from parking place to final destination and back, while BMW ConnectedDrive also offers intermodal route guidance as a first, which incorporates local public transport connections into journey planning. The aim of this intelligent networking is to enable maximum driving pleasure (Freude am Fahren) in a car emitting zero local emissions.
The BMW i3 can be optionally equipped with a navigation system the functionality of which has been extended to include the BMW ConnectedDrive services developed specifically for BMW i. The Driving Range Assistant supports both route planning and the current journey. If the destination selected in the navigation system lies beyond the vehicle’s current range, it comes to the driver’s aid by suggesting switching to the ECO PRO or ECO PRO+ mode, as well as calculating a more efficient alternative route. And if the battery has to be recharged at a public charging station, the driver is given a choice of available stations in the neighborhood.
A further key element of the linked-up navigation unit is a dynamic range display, which delivers remarkably precise, up-to-date and reliable information by factoring in all the relevant variables. The battery’s charge status, the driving style, activity of electric comfort functions and the selected driving mode are all taken into account for the calculation, along with the route’s topography, current traffic levels and the outside temperature.
The system is therefore able to make allowance for the extra energy required for an upcoming climb, stop-start traffic or a traffic jam on the selected route, and lower its range calculation accordingly. The up-to-the-minute and detailed real-time traffic information provided by the RTTI system is also added to the equation. The information is analyzed and evaluated centrally by the BMW ConnectedDrive server that is in permanent communication with the vehicle.
The dynamic range display is visualized on the central information display in the BMW i3 as a peripheral contour within the navigation map. Taking the vehicle’s current location as a starting point, all points that can be reached in the various driving modes are displayed in the form of a range spidergram.
Apart from the information required for the route guidance currently in progress, the navigation system also helps drivers to plan mobility requirements beyond their present destination. For the purpose of energy management, not only are the current battery capacity levels taken into account, but the various options for recharging are also considered.
In the same way that points of interest such as restaurants, hotels and tourist sights are visualized, charging stations and parking facilities can also be shown in the information display if desired. The driver can see which car parks and charging stations are full or have spaces, and the information is constantly updated via the connection to the BMW server. In the future, drivers will be able to reserve a space at a charging station from their vehicle. The complete connectivity concept also gives customers the option of booking these and other products from BMW ConnectedDrive after taking delivery of their vehicle.
The BMW ConnectedDrive server additionally provides up-to-the-minute data indicating whether potential charging stations will actually have spaces available on arrival. For instance, drivers can call up a station located close to the journey’s destination in advance. The system also notifies them of the charging time required before commencing the return journey or the onward journey to the next destination.
Remote app. The mobility planning information provided is made available on the customer’s smartphone as well as in the vehicle. This connectivity is provided by an application developed especially for BMW i for mobile phones with the iOS and Android operating systems. The app is an enhanced version of the remote services offered by BMW ConnectedDrive.
The Remote app for BMW i allows drivers to access vehicle data and relevant information on route planning at any time. The driver is also able to use the app to call up a display of charging stations that are either full or have spaces, and see whether they are located within the vehicle’s current driving range.
To this end, the range contour is also displayed here just as it is in the vehicle’s navigation system. A real-time overview of charging stations and parking facilities can also be found online by visiting the BMW ConnectedDrive customer portal. The recharging facilities provided by the ChargeNow network of charging stations are also shown.
If the vehicle is plugged into a public charging station or the BMW i Wallbox, the charging procedure can be controlled both remotely and using a timer function. A range calculation graphic identical to that in the vehicle can be viewed on the smartphone too. The BMW i App can also be used to search for and select a navigation destination or a free charging station and then import it to the vehicle’s system.
Besides this, the available charging stations along the route and in the vicinity of the destination are likewise visualized in the BMW i App, just as they are in the vehicle’s information display. This enables the driver not only to plan the upcoming journey in good time and with foresight, but also to make adequate preparations for further mobility requirements beyond the immediate future.
Drivers also have the ability to control not just the charging process remotely but also the advance preparation of the vehicle. If the BMW i3 is plugged into a charging station or the BMW i Wallbox, the energy supply can be controlled from the smartphone. The vehicle’s air conditioning and heating of the high-voltage battery can likewise be activated remotely. Pre-heating the battery ensures optimum operating status for performance, range and battery durability, even at low ambient temperatures. There is also the option of programming the charging process using the app so that charging takes place when electricity is cheaper, for example using off-peak tariffs at night.Sales model. In selected markets, sales of BMW i products and services will be handled via an innovative multi-channel sales model. In addition to dealerships, this model will also comprise a mobile sales team, a Customer Interaction Centre (CIC) and Internet sales. All the new platforms are interlinked. Whichever sales channel a customer chooses, and regardless of whether they buy or lease the vehicle, their contract is always with BMW AG and not with the dealer, as would normally be the case. BMW expects that at launch, more than 10% of European BMW dealers will also be handling sales of BMW i models.