|The A-Class E-CELL. Click to enlarge.|
Mercedes-Benz is introducing the A-Class E-CELL, a compact five-seat battery-electric car with a range of more than 200 km (124 miles) (NEDC), targeted as a family EV for urban areas. The A-Class E-CELL is Mercedes’ second electric car to be built in series-production conditions, following on the Mercedes B-Class F-CELL hydrogen fuel cell vehicle. (Earlier post.)
A total production run of 500 A-Class E-CELL cars will be built at Rastatt, beginning in autumn 2010. The vehicles will be leased to selected customers in several European countries, including Germany, France and the Netherlands.
In line with the strategy used for hybrid development, Mercedes engineers have developed a modular system for electric vehicles with battery and fuel-cell. The benefits include the efficient use of shared parts in all the brand’s electric vehicles. All the key components of electric cars are appropriate for a modular approach—for example, the electric drive of the A-Class E-CELL is also used in the B-Class F-CELL. Both energy storage units in the electric A-Class are the same as the battery in the smart fortwo electric drive.
The electric drive of the A-Class E-CELL is a permanent-field synchronous unit developing a peak output of 70 kW (95 hp), a continuous power rating of 50 kW (68 hp) and a high maximum torque of 290 N·m (214 lb-ft). The A-Class E-CELL accelerates from 0-60 km/h (37 mph) in 5.5 seconds. A kick-down function is used to deliver maximum acceleration, according to the current charge level and battery temperature. Maximum speed is electronically set at 150 km/h (93 mph).
The E-CELL is powered by twin Li-ion battery packs with a combined capacity of 36 kWh. A special thermomanagement system keeps the high-voltage batteries cooled to within an optimum temperature window. The cooling system is based on a low-temperature cooling circuit. Fluid cooling with a water-glycol mixture ensures a stable operating temperature supporting the high degree of efficiency and the longevity of the energy storage. In very high ambient temperature conditions, the battery cooling system is boosted with the coolant circuit of the air-conditioning system.
The electrical drive system and two on-board chargers are cooled with a high-temperature cooling circuit. This circuit keeps the units working at optimum operating temperatures, with maximum power delivery from the drive system. The car’s power electronics supply the 12-volt vehicle electrical system via a DC/DC converter with electric current from the high-voltage system. The electronics system also controls other functions such as the heating and air-conditioning systems in order to minimize the load placed on the battery for this purpose.
A range of charging options are available, including single-phase 230-volt sockets, three-phase sockets in a household wall-box, and public recharging points. Using a single-phase 230V network, it takes around eight hours’ charging time to accumulate the energy required for a range of 100 km (NEDC). This time is reduced to three hours in the case of charging from a wall-box or at a roadside recharging point.
Like the smart fortwo electric drive in its category, the A-Class E-CELL is fitted with an intelligent charging management system based on “SmartCharge Communication”. Via the vehicle electronics system, all relevant information—such as the electricity supply contract identification data—is exchanged with the charging point.
Other features of the car include pre-start climate control. While the A-Class E-CELL batteries are being charged at home or at a roadside charging point, the interior can be pre-heated or cooled to a temperature set by the driver. Another function enables the driver to monitor charging progress and therefore the present range available, via the internet or a smartphone, for example.
The A-Class E-CELL electronics also provide for proactive control of the charging operation, such as time of charge. The interface in the A-Class E-CELL provides a range of billing, control and monitoring functions.
The EV offers the same luggage compartment volume as in the internal combustion engine A-Class (435 to 1370 liters), a 350-kilogram payload measured as per the relevant EC directive and high variability of the interior and luggage compartment.
With a low center of gravity, partly the result of the installation of the batteries under the passenger compartment in the “sandwich” structure of the vehicle floor, the car has excellent road-holding and sprightly handling characteristics.
Another benefit from this installation location is the provision of best-possible protection against the intrusion of structural components in the event of a head-on collision or impact from the rear; the batteries are located outside the vehicle body’s deformation zones. The high-stability characteristics of the sandwich structure of the floor also provide protection for both battery and passengers in a lateral collision scenario.