Combine the electrical engineering know-how it takes to make the best driver's cars in the world even better with a full electric powertrain and you have one special green sports car.
The eRUF Concept Model A is only at the prototype stage, but unlike start-up companies that make bold promises for full electric sports cars only to string along potential buyers and the media, RUF has produced a turn-key, fully working electric Porsche with some serious performance specs.
Lithium Ion Batteries and a Powerful Electric Motor
The eRUF Concept Model A uses the newest generation of lithium ion batteries, which are still too expensive to be viable in fuel-frugal hybrids like the Toyota Prius and upcoming Honda Insight.
The advantages to lithium ion batteries, the same basic technology that powers cell phones and laptops, are greater charge density and longevity than the nickel hydride batteries used in the current generation of hybrids and electric cars.
The powerplant comes in the form of a 150 kW electric motor similar to those used in the Tesla Roadster. Electric vehicles have some performance advantages, most notably the fact that all 650 Nm of torque are available from 0--yes, zero--rpm. Imagine the tire smoking capabilities!
The eRUF is still a long way from being viable for production even in small runs, but RUF has one thing going for them: they are already in the business of charging well north of $100,000 for their Porsche-based super sports cars. Making an electric Porsche still leaves them with a huge profit margin to operate with.
Drivetrain
Layout Electric RWD
Transmission Modifed 6 Speed maintaining feel of standard gear ratios
Differential Electronically Controlled LSD
Engine
Type: Brushless three phase alternating current with permanent magnets
Batteries Lithium-Ion, iron-phosphate base
Engine & Transmission
Power bhp (kW) at RPM: Power + 150 kW to -150 kW (peak level) + 204 hp to -204 hp
Torque lb-ft (Nm) at RPM: Max torque + 650 Nm to -650 Nm
Redline at RPM: Rpm level max 5000 rpm
Exterior
Body Type 2 door, 2 seat sports car
Performance
Acceleration 0-60 mph s: Less than 7 seconds
Emissions Just smiles.
Charge Time 10 hours to max. charge
Range 245-320 km, depending on driving style
eRUF Concept Model A 2008
Official RUF Automotive GmBH Press Release
"Emotion without Emission"
Ruf Automobile GmbH, internationally well known manufacturer for high performance
automobiles and the producer of the famous CTR-series is now introducing the first
electrically powered sports car from Germany.
The fundamental ideas that lead to the development of the eRUF concept vehicle came from Alois Ruf. The car maker from the Bavarian town of Pfaffenhausen had a vision of a simple energy transfer concept: his hydroelectric power plants, which feed 35 million kW hours of electricity annually into the German electrical network, could also more or less directly power modern autos. 35 million kWh is enough energy to power one of the prototypes eRUF as described below for 3500 journeys around the globe – or 3500 of the cars one time around the world each.
The idea seemed even more inspiring, as it would be possible for him to connect cars directly to the emission-free power plants for charging and drive away on the water-generated power. The eRUF Model A concept car is the first prototype to lead the technical development away from the combustion engine.
Actually, for the first time an electric motor is being used which comes to fitting into the Ruf model range.
The three-phase AC motor's performance easily puts many conventional conbustion engines to shame. It produces its maximum 650 Nm torque output from 0 rpm onwards. This power rips into the drive shafts so impressively during acceleration, that one is immediately reminded of the extremely powerful Ruf Rt 12.
It is actually enough simply to put the car in 6th gear and press down the accelerator pedal (an "amp pedal", not a "gas pedal" in this car!), and drive off. The eRUF Model A has such impressive acceleration that the project goal of 0-100 km/h in under 7 seconds was achieved.
The maximum power output is around 204 hp if you translate it into combustion engine terms. In direct connection to Volt and Ampere the maximum output level of 150 kW is a useful figure.
A short discourse regarding efficiency might be helpful at this point: a highly-developed, modern petrol engine uses around 75 percent of the energy in its tank to heat the engine coolant and exhaust gas and only 25 to 30 per cent for actual propulsion. A diesel manages to convert a respectable 35 to 40 percent of its fuel energy into motion. The permanent magnet electric motor, on the other hand, is a model of high efficiency: it offers over 80 percent efficiency over the majority of its power range, extending 90 per cent in the upper end of its power range.
Ruf engaged CALMOTORS in Camarillo, California, specialized in the implementation of hybrid electric and electric only power train designed to combine the latest generation of lithium-ion batteries with its motor.
Since the 150 kW electric motor unit is very compact, there is a lot of room for batteries in the Ruf's bodywork.
The Axeon iron-phosphate, lithium-ion batteries currently in use weight 5.6 kg and deliver 160 Ah each. This means each one could theoretically deliver 160 amperes of electricity for one hour under normal temperatures or 1 ampere for 160 hours.
The generation of batteries available from Axeon represents by no means the end of the developmental curve. Current performance improvements in battery technology indicate that end of this improvement spiral is nowhere near.
The driving current in the eRUF is regulated by an electric "drive-by-wire" accelerator pedal. It is not the first electrical accelerator in a Ruf model. Other Ruf models also provided load control via potentiometer-pedals, nicely dosed for their powerful engines.
The power and torque produced by the 3-phase motor can be used to recover just as much power as it can put out. When coasting, the motor becomes a generator producing electricity to charge the batteries. The torque and electrical amperage ratings below are therefore to be understood as theoretical absolute maximums and minimums.
The 96-cell battery system is constantly monitored by an intelligent bus system from Axeon. Each individual cell is coupled with a sensor that sends critical information on cell temperature and voltage to the central control system. If irregularities appear during operation, the system can react within milliseconds to bring the values back in line, effectively preventing critical lithium-ion overheating behaviour during charging.
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