| e-Golf. Click to enlarge. |
Volkswagen of America, Inc. announced details of the e-Golf, its first fully electric vehicle to go on sale in the US, prior to its debut at the Los Angeles Auto Show. Volkswagen earlier this year introduced the production version of the e-Golf and e-up! at the Frankfurt show.
The e-Golf is available in five-door form only and is immediately recognizable by its unique aluminum-alloy wheels and by its LED headlights, the first time they have been used as standard on a Volkswagen vehicle. The e-Golf is due to go on sale in select states in the fourth quarter of 2014.
Powertrain. The e-Golf is powered by an 85 kW EEM-85 synchronous permanent-magnet AC motor which develops 199 lb-ft (270 N·m) of torqueT. The e-Golf accelerates from 0 - 25 mph (40 km/h) in 4.2 seconds and from 0-60 mph in approximately 10.4 seconds. Top speed is electronically limited to 87 mph (140 km/h).
| Top transparency of the e-Golf. Click to enlarge. |
The high-performance 12,000-rpm motor and the single-speed EQ270 transmission form a compact unit: the EQ270 also incorporates an integrated differential and an electro-mechanical parking brake. The motor and transmission was developed in-house and is made at Volkswagen’s components plant in Kassel, Germany.
Depending on driving style and charging behavior, the average range for the e-Golf is between 70 and 90 miles (113 to 145 km). Helping ensure optimal range in cold weather is a newly developed heat pump. The pump uses both ambient air and heat from the drive system components to heat the cabin rather than relying solely on the high-voltage heater, helping to reduce on-board electrical consumption significantly, especially in winter driving.
Lithium-ion battery. The Golf A7 was developed from the outset to be a Battery Electric Vehicle. As the Modular Transverse Matrix (MQB) architecture that underpins the new Golf A7 is so flexible, Volkswagen was able to integrate the lithium-ion battery in a space-saving frame in the vehicle floor, under the front and rear seats and in the center tunnel. Like the electric motor and the transmission, the battery was also developed in-house at Volkswagen and is made at the company’s facility in Braunschweig, Germany.
The liquid-cooled lithium-ion battery accounts for 701 pounds (318 kg) of the e-Golf model’s 3090-pound (1,402 kg) curb weight. It comprises 264 individual prismatic cells, which are integrated into 27 modules (each with six or twelve cells). Collectively, the cells have a nominal rating of 323 volts, with an overall capacity of 24.2 kWh.
A battery management controller (BMC) performs diagnosis and monitoring functions and also regulates the temperature balance in the battery junction controller (the interface to the motor’s energy supply). When the car is not in use or in the event of a collision, power from the battery is automatically cut off.
A central element of the drive system is the power electronics module. This controls the flow of high-voltage energy between the electric motor and the lithium-ion battery, depending on the battery voltage, which runs between 250 and 430 volts. During the process the power electronics module converts the direct current (DC) stored in the battery into alternating current (AC). The power electronics therefore have the following interfaces: the traction circuit connection to the battery; the three-phase connection to the electric motor; the plug connection from the DC/DC converter to the 12-volt power circuit; and a connection for the high-voltage power distributor.
Charging concept and equipment. There are several different ways of charging the e-Golf’s battery via the car’s standard 7.2 kW onboard charger. The most optimal solution is the available 220-volt wallbox for a garage or carport: this charges at 7.2 kW, enabling a completely flat battery to be fully charged in less than four hours. If a 220-volt connection is not available, the most cost-effective and easiest alternative is to plug the standard charging cable into a 110/120-volt electrical socket, which will take around 20 hours to charge the battery.
The standard Combined Charging System (CCS) plug gives the e-Golf the capability to also take advantage of DC Fast Charging infrastructure. In this case the car can be recharged at CCS-equipped DC fast charge stations at levels of up to 40 kW, allowing the battery to be charged to 80% in around 30 minutes. For added flexibility, the charging process can be activated—immediately or programmed for later—by pressing a button next to the charging socket under the “fuel cap” or through an available iPhone or Android app.
Driver control. The e-Golf features two technologies that allow the driver to control the vehicle’s energy use: three driving profiles designed to preserve energy (‘Normal’, ‘Eco’, and ‘Eco+’); and three different levels of regenerative braking (‘D1’, ‘D2’, and ‘D3’/‘B’).
The car automatically defaults to ‘Normal’ mode upon start up. To extend the range, the first option is the ‘Eco’ mode, which pares back the electric motor’s maximum power output to 94 hp (70 kW) and the starting torque to 162 lb-ft (220 N·m). In parallel, the electronics reduce the output of the air conditioning system and modify the response curve of the accelerator pedal. In Eco mode, the e-Golf is limited to a top speed of 72 mph (116 km/h) and 0 to 62 mph acceleration is increased to 13.1 seconds.
In ‘Eco+’ mode, the electronics limit the power output to 74 hp (55 kW) and the starting torque to 129 lb-ft (175 N·m), further flatten the accelerator pedal response curve and the air conditioning is switched off. The e-Golf now reaches a top speed of 56 mph (90 km/h) and accelerates at a correspondingly slower rate. Nevertheless, full power, maximum torque, and the 87 mph top speed can be obtained if the driver depresses the accelerator pedal fully down in either ‘Eco’ or ‘Eco+’ mode.
| Driver profile settings | ||||||
|---|---|---|---|---|---|---|
| Setting | Power output | Torque | Top speed | |||
| Normal | 85 kW | 270 N·m | 87 mph | |||
| Eco | 70 kW | 220 N·m | 72 mph | |||
| Eco+ | 55 kW | 175 N·m | 56 mph | |||
Regenerative braking settings. In addition to the driving modes, the regenerative braking system can also be used to manage range. There are three driver-selectable levels available: ‘D1’, D2’, and ‘D3’/‘B’.
To switch to ‘D1”, ‘D2”, or ‘D3”, the driver taps the “shift” lever to the left once, twice, or three times. Tapping the knob to the right moves sequentially back to ‘D’. If the lever is pushed to the right and briefly held there, the electronics switch straight back to ‘D’. The driver activates regenerative braking level ‘B’, which is the same as ‘D3’, by pulling the lever backwards.
In an electric car this amount of flexibility can lead to a different way of driving. It is possible to use regenerative braking consciously to slow the e-Golf down. Level ‘D1’ regenerates energy and slows down the car the least, while level ‘B’ has the strongest effect. At levels ‘D2’, ‘D3’ and ‘B’, the deceleration via regenerative braking is so strong that the brake lights come on automatically. However, if the battery is fully charged, no energy regeneration takes place.
Aerodynamics. Volkswagen took very specific measures to lower the e-Golf model’s coefficient of drag (Cd). Among these were: reducing the volume of cooling air via a radiator shutter and partially enclosed radiator grille; new underbody paneling; a rear spoiler and C-pillar air vanes to better manage airflow at the tail of the car; and cleaning up the airflow around the wheels, largely by ensuring they are flush with the wheelarches.
Acoustics. Electric drive systems present an acoustic challenge because the noise from an internal combustion engine is absent and thus different sources of sound become noticeable, while wind and tire noise become even more apparent. In addition, barely perceptible yet very specific electric drivetrain noises are joined by the sounds and vibrations of the electrically powered auxiliary components. To help ensure pedestrians can hear this almost silent vehicle coming, the e-Golf has a low-speed sound system installed.
Volkswagen specifically tailored the acoustics of the e-Golf for an electric vehicle, making it an almost silent cruiser. As an example, the powerplant’s subframe was changed to a pendulum mount: despite the electric motor’s high torque build-up when accelerating, this greatly enhances the acoustics. The motor housing unit was also specifically designed to achieve an extremely low level of noise emission. Finally, the interior uses highly sound-absorbent and yet very lightweight materials to produce a vehicle that is quieter than many luxury cars, Volkswagen says.
Design. Visually the e-Golf is distinguished by its energy-efficient LED headlights, used here for the first time on an American Volkswagen model. Compared to Bi-Xenon lights, the LED system produces more light despite consuming less power. Going forward, Volkswagen electric cars will feature a C-shaped LED DRL signature in the redesigned front bumper.
The lack of tailpipes at the rear of the car is an obvious clue that this is an EV, along with the badging and blue highlights on the VW logo. Other e-Golf design features include aerodynamically optimized 16-inch aluminum-alloy wheels with low rolling resistance 205-section tires.
| Instrument panel. Click to enlarge. |
Interior. The e-Golf has a new instrument layout. The tachometer, which normally lives on the left-hand-side of the instrument cluster, is replaced by the power display which indicates if the motor is ready, the battery is being charged via regenerative braking, or power is being drawn off and an indicator of available output.
To its right, there is a conventional speedometer. The lower section of the speedometer now has an indicator showing the high-voltage battery’s state of charge. The color display between the power gauge and the speedometer now indicates the driving range, the current level of regenerative braking, and the remaining charging time and the type of charging connection. In a separate LED field at the lower segment of the multifunction display, the ‘READY’ message also appears after starting the motor.
The touchscreen in the center console is also equipped with additional functionality, such as a range monitor; energy flow indicator; and e-manager. The e-manager enables drivers to pre-program up to three departure and charging times. At the defined time, this helps ensure that the vehicle has the air conditioning level set and the battery charged.
Driver Assistance Systems. The e-Golf features as standard a new assistance system called the Automatic Post-Collision Braking System. Studies in accident research have shown that about a quarter of accidents that involve personal injury are of the multi-collision type.
The APCBS automatically slows the vehicle when it is involved in an accident in order to significantly reduce its residual kinetic energy. The system is triggered based on detection of a primary collision by the airbag sensors. Vehicle braking by means of the system is limited by the ESC control unit to a maximum rate of 0.6 g.
The driver can override the system at any time; for example, if the system recognizes that the driver is accelerating, it gets disabled. The automatic system is also deactivated if the driver initiates hard braking at an even higher rate of deceleration.
Connectivity. The e-Golf will have its own dedicated “VW Car-Net e-Remote” app that will allow owners to adjust vehicle settings via a compatible smartphone or the VW Car-Net website. The app will contain the following functions:
- Climate control
- Charging the battery
- Accessing vehicle data
- Vehicle status queries
Source: Green Car Congress
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