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Five doors, five seats, the same luggage compartment volume as in the
internal combustion engine A‑Class (435 to 1370 litres), a 350‑kilogram
payload measured as per the relevant EC directive and high variability
of the interior and luggage compartment: this is what makes the new
A-Class E-CELL a family car for everyday use. The sophisticated sandwich
structure provides both an extremely comfortable in-car environment and
maximum protection for passengers and components in the event of a
collision.
“Over our almost 125-year history, we have accumulated extensive
experience and knowhow in the area of electric vehicles, including both
battery and fuel-cell. This knowhow has already provided the basis for
getting two electric cars for everyday use onto the road: the smart
fortwo electric drive, and the B‑Class F‑CELL. The story now continues
with our third electric car, the A‑Class E‑CELL., whose start of
production is scheduled for autumn this year. The new car is a
battery-driven electric Mercedes that enlarges our portfolio and offers
our customers the kind of driving pleasure, comfort and safety that they
have come to expect”, says Dr Thomas Weber, the Daimler AG Board of
Management member responsible for Group Research and Development
Mercedes-Benz Cars.
Driving pleasure with zero emissions
Along with exemplary safety, optimum comfort and a high level of
suitability for daily use, the A‑Class E‑CELL also offers other
strengths not always to be found in contemporary electric cars: agility
and driving pleasure. The features are based on a low centre of gravity,
partly the result of the installation of the batteries under the
passenger compartment, in the “sandwich” structure of the vehicle floor.
This gives the car excellent road-holding and sprightly handling
characteristics – qualities that clearly set the A‑Class E‑CELL apart
from other electric cars, which often have heavy and bulky storage
batteries located in the boot or by the rear seat.
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. This is because the batteries are
located outside the vehicle body’s deformation zones. The high-stability
characteristics of the sandwich structure of the floor also provide
outstanding protection for both battery and passengers in a lateral
collision scenario.
High-performance electric drive with long range
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 Nm, as
expected for an electric drive, available right from the first
revolution. This makes the A‑Class E‑CELL an outstandingly assured and
dynamic performer on the road, taking just 5.5 seconds to accelerate
from zero to 60 km/h. 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.
The energy storage units are two high-performance lithium-ion batteries
based on high-voltage technology. The advantages of lithium-ion
batteries include their compact dimensions and significantly higher
efficiency in comparison with nickel-metal-hydride (NiMH) batteries.
They offer 30 percent more energy density than NiMH technology, and 50
percent more power density. Other benefits include high charging
efficiency and a long service life. The combined energy capacity of the
two lithium-ion batteries is a total of 36 kWh. With fully charged
batteries, the A‑Class E‑CELL has a range of over 200 kilometres (NEDC).
Efficient battery cooling system
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
minimise the load placed on the battery for this purpose.
Flexible charging options
The batteries of the A‑Class E‑CELL can be either replenished at public
charging points or plugged into an ordinary household power socket. 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 230-volt 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 just three hours in
the case of charging from a wall-box or at a roadside recharging point.
Daimler and a number of other European automakers and energy utilities
have agreed on standardised charging plugs and sockets, with an ultimate
aim of worldwide standardisation. This makes the technology more
customer-friendly, and is seen as a key prerequisite for the rapid
spread of electric mobility.
Intelligent charging management
Like the smart fortwo electric drive in its category, the A‑Class E‑CELL
is the world’s first vehicle in its class to be 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. Benefits include a
convenient, simple and totally reliable billing system.
Other intelligent 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. So if the electric car is parked for a long period,
recharging can be set to take place at times when electricity is
cheaper, for example during the night. The intelligent interface in the
A‑Class E‑CELL provides a range of billing, control and monitoring
functions, making electric mobility convenient and safe, and therefore
very customer-friendly. The vehicle is automatically immobilised on
connection of the charging cable to the socket, preventing any
possibility of driving off by mistake while charging is in progress.
This makes the recharging operation even safer and more convenient for
the user.
Everything under control” when out on the road
To make vehicle handling and control as easy, safe and transparent as
possible for the driver, the A‑Class E‑CELL has its own control and
display concept specifically designed for the requirements of an
electric car. The multifunction display in the vehicle shows the battery
charge status, trip data such as kilometres driven, travelling time,
average speed and average fuel consumption, along with the remaining
range and residual electrical energy capacity (SoC = state of charge).
Another detail specific to the system is a display of the currently
available drive power. Meanwhile, the rev counter normally to be found
on the instrument panel is replaced with an indicator showing the
instantaneous drive power demand or recovery power. Green, white and
red-coloured segments show whether the drive system is currently
operating in charge, economy or boost mode.
Modular system for electric cars
In line with the strategy used for hybrid development, Mercedes
engineers have also 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.
Photos: M-B
(Sept. 14, 2010)
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