Mercedes SLS Electric Drive
Mercedes SLS Electric Drive is the latest super car to come out of Mercedes AMG factories, but it hasn’t a V8 under the bonnet. It has four electric motors on top of each of the wheels that make it faster the actual SLS V8.
The most powerful AMG high-performance vehicle of all time has four electric motors producing a total output of 552 kW and a maximum torque of 1000 Nm. As a result, the gullwing model has become the world’s fastest electrically-powered series production vehicle: the Mercedes-Benz SLS AMG Coupé Electric Drive accelerates from zero to 100 km/h in 3.9 seconds. Oh and don’t worry about the lack of noise. AMG has developed an artificial system that makes great V8 noises.
The Electric Drive will be celebrating its market launch in 2013. The price in Germany will be 416,500 EUR, which is fair enough considering how advanced it is.
Technical details in Mercedes press release below:
Advanced Formula 1 technology: high-voltage lithium-ion battery
Battery efficiency, performance and weight: in all three areas Mercedes-AMG is setting new standards. The high-voltage battery in the SLS AMG Coupé Electric Drive boasts an energy content of 60 kWh, an electric load potential of 600 kW and weighs 548 kg – all of which are absolute best values in the automotive sector. The liquid-cooled lithium-ion high-voltage battery features a modular design and a maximum voltage of 400 V.
Advanced technology and know-how from the world of Formula 1 have been called on during both the development and production stages: the battery is the first result of the cooperation between Mercedes-AMG GmbH in Affalterbach and Mercedes AMG High Performance Powertrains Ltd. Headquartered in Brixworth in England, the company has been working closely with Mercedes-AMG for a number of years. F1 engine experts have benefited from its extensive expertise with the KERS hybrid concept, which made its debut in the 2009 Formula 1 season. At the Hungarian Grand Prix in 2009, Lewis Hamilton achieved the first historic victory for a Formula 1 vehicle featuring KERS hybrid technology in the form of the Mercedes-Benz KER System. Mercedes AMG High Performance Powertrains supplies the Formula 1 teams MERCEDES AMG PETRONAS, Vodafone McLaren Mercedes and Sahara Force India with Mercedes V8 engines and the KERS.
The high-voltage battery consists of 12 modules each comprising 72 lithium-ion cells. This optimised arrangement of a total of 864 cells has benefits not only in terms of best use of the installation space, but also in terms of performance. One technical feature is the intelligent parallel circuit of the individual battery modules – this helps to maximise the safety, reliability and service life of the battery. As in Formula 1, the battery is charged by means of targeted recuperation during deceleration whilst the car is being driven.
High-performance control as well as effective cooling of all components
A high-performance electronic control system converts the direct current from the high-voltage battery into the three-phase alternating current which is required for the synchronous motors and regulates the energy flow for all operating conditions. Two low-temperature cooling circuits ensure that the four electric motors and the power electronics are maintained at an even operating temperature. A separate low-temperature circuit is responsible for cooling the high-voltage lithium-ion battery. In low external temperatures, the battery is quickly brought up to optimum operating temperature with the aid of an electric heating element. In extremely high external temperatures, the cooling circuit for the battery can be additionally boosted with the aid of the air conditioning. This also helps to preserve the overall service life of the battery system.
Quick charge function via special wall box
Ideally the Mercedes-Benz SLS AMG Coupé Electric Drive is charged with the aid of a so-called wall box. Installed in a home garage, this technology provides a 22 kW quick-charge function, which is the same as the charging performance available at a public charging station. A high-voltage power cable is used to connect the vehicle to the wall box, and enables charging to take place in around three hours. Without the wall box, charging takes around 20 hours. The wall box is provided as an optional extra from Mercedes-AMG in cooperation with SPX and KEBA, two suppliers of innovative electric charging infrastructures for the automotive industry.
Eight-stage design for maximum safety
To ensure maximum safety, the SLS AMG Coupé Electric Drive makes use of an eight-stage safety design. This comprises the following features:
- all high-voltage cables are colour-coded in orange to prevent confusion
- comprehensive contact protection for the entire high-voltage system
- the lithium-ion battery is liquid-cooled and accommodated in a high-strength aluminium housing within the carbon-fibre zero-intrusion cell
- conductive separation of the high-voltage and low-voltage networks within the vehicle and integration of an interlock switch
- active and passive discharging of the high-voltage system when the ignition is switched to “off”
- in the event of an accident, the high-voltage system is switched off within fractions of a second
- continuous monitoring of the high-voltage system for short circuits with potential compensation and insulation monitors
- redundant monitoring function for the all-wheel drive system with torque control for individual wheels, via several control units using a variety of software
By using this design, Mercedes-AMG ensures maximum safety during production of the vehicle and also during maintenance and repair work. Of course the Mercedes-Benz SLS AMG Coupé Electric Drive also meets all of the statutory and internal Mercedes crash test requirements.
All-wheel drive with AMG Torque Dynamics enables new levels of freedom
Four motors, four wheels – the intelligent and permanent all-wheel drive of the SLS AMG Coupé Electric Drive guarantees driving dynamics at the highest level, while at the same time providing the best possible active safety. Optimum traction of the four driven wheels is therefore ensured, whatever the weather conditions. According to the developers, the term “Torque Dynamics” refers to individual control of the electric motors, something which enables completely new levels of freedom to be achieved. The AMG Torque Dynamics feature is permanently active and allows for selective distribution of forces for each individual wheel. The intelligent distribution of drive torque greatly benefits driving dynamics, handling, driving safety and ride comfort. Each individual wheel can be both electrically driven and electrically braked, depending on the driving conditions, thus helping to
- optimise the vehicle’s cornering properties,
- reduce the tendency to oversteer/understeer,
- increase the yaw damping of the basic vehicle,
- reduce the steering effort and steering angle required,
- increase traction,
- and minimise ESP® and ASR intervention.
The AMG Torque Dynamics feature boasts a great deal of variability and individuality by offering three different transmission modes:
- Comfort (C): comfortable, forgiving driving characteristics
- Sport (S): sporty, balanced driving characteristics
- Sport plus (S+): sporty, agile driving characteristics
AMG Torque Dynamics enables optimum use of the adhesion potential between the tyres and the road surface in all driving conditions. The technology allows maximum levels of freedom and as such optimum use of the critical limits of the vehicle’s driving dynamics. Outstanding handling safety is always assured thanks to the two-stage Electronic Stability Program ESP®.
“AMG Lightweight Performance” design strategy
The trailblazing body shell structure of the Mercedes-Benz SLS AMG Coupé Electric Drive is part of the ambitious “AMG Lightweight Performance” design strategy. The battery is located within a carbon-fibre monocoque which forms an integral part of the gullwing model and acts as its “spine”. The monocoque housing is firmly bolted and bonded to the aluminium spaceframe body. The fibre composite materials have their roots in the world of Formula 1, among other areas. The advantages of CFRP (carbon-fibre reinforced plastic) were exploited by the Mercedes-AMG engineers in the design of the monocoque. These include their high strength, which makes it possible to create extremely rigid structures in terms of torsion and bending, excellent crash performance and low weight. Carbon-fibre components are up to 50 percent lighter than comparable steel ones, yet retain the same level of stability. Compared with aluminium, the weight saving is still around 30 percent, while the material is considerably thinner. The weight advantages achieved through the carbon-fibre battery monocoque are reflected in the agility of the SLS AMG Coupé Electric Drive and, in conjunction with the wheel-selective four-wheel drive system, ensure true driving enjoyment. The carbon-fibre battery monocoque is, in addition, conceived as a “zero intrusion cell” in order to meet the very highest expectations in terms of crash safety. It protects the battery modules inside the vehicle from deformation or damage in the event of a crash.
The basis for CFRP construction is provided by fine carbon fibres, ten times thinner than a human hair. A length of this innovative fibre reaching from here to the moon would weigh a mere 25 grams. Between 1000 and 24,000 of these fibres are used to form individual strands. Machines then weave and sew them into fibre mats several layers thick, which can be moulded into three-dimensional shapes. When injected with liquid synthetic resin, this hardens to give the desired structure its final shape and stability.
Optimum weight distribution and low centre of gravity
The purely electric drive system was factored into the equation as early as the concept phase when the super sports car was being developed. It is ideally packaged for the integration of the high-performance, zero-emission technology: by way of example, the four electric motors and the two transmissions can be positioned as close to the four wheels as possible and very low down in the vehicle. The same applies to the modular high-voltage battery. Advantages of this solution include the vehicle’s low centre of gravity and balanced weight distribution – ideal conditions for optimum handling, which the electrically-powered gullwing model shares with its petrol-driven sister model.
New front axle design with pushrod damper struts
The additional front-wheel drive called for a newly designed front axle: unlike the series production vehicle with AMG V8 engine, which has a double wishbone axle, the SLS AMG Coupé Electric Drive features an independent multi-link suspension with pushrod damper struts. This is because the vertically-arranged damper struts had to make way for the additional drive shafts. As is usual in a wide variety of racing vehicles, horizontal damper struts are now used, which are operated via separate push rods and transfer levers. Thanks to this sophisticated front-axle design, which has already been tried and tested in the world of motorsport, the agility and driving dynamics of the Mercedes-Benz SLS AMG Coupé Electric Drive attain the same high levels as the V8 variant. Another distinguishing feature is the speed-sensitive power steering with rack-and-pinion steering gear: the power assistance is implemented electrohydraulically rather than just hydraulically.
AMG ceramic composite brakes for perfect deceleration
The SLS AMG Coupé Electric Drive is slowed with the aid of AMG high-performance ceramic composite brakes, which boast direct brake response, a precise actuation point and outstanding fade resistance, even in extreme operating conditions. The over-sized discs – measuring 402 x 39 mm at the front and 360 x 32 mm at the rear – are made of carbon fibre-strengthened ceramic, feature an integral design all round and are connected to an aluminium bowl in a radially floating arrangement.
The ceramic brake discs are 40 percent lighter in weight than the conventional, grey cast iron brake discs. The reduction in unsprung masses not only improves handling dynamics and agility, but also ride comfort and tyre grip. The lower rotating masses at the front axle also ensure a more direct steering response – which is particularly noticeable when taking motorway bends at high speed.
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