BMW ActiveE Concept – fully electric 1 Series Coupe
By Gizmag Team
December 17, 2009
BMW will finally deliver the electric car everyone knew was coming at the NAIAS in January. The BMW ActiveE Concept is essentially an electric BMW 1 Series Coupe built using the knowledge gained from year-long MINI E fleet trials, and the resultant vehicle is bristling with ideas and well worth a look. The 125 kW motor is located in the rear axle, the lithium ion batteries recharge in three hours, offer a range of 160 km (100 miles) and an interesting variation on regenerative braking can add as much as 20% to the range. With an electronically limited top speed of …
BMW claims the ActiveE will hit 100 km/h in less than 9 seconds (0-60 mph in 8.5 seconds), with the 60 km/h mark being reached in less than 4.5 seconds and the maximum speed is electronically limited at around 145 km/h (90 mph).
Electrical vehicle components are usually much more space efficient than internal combustion-engined vehicles, as there is no massive engine and drive train to take up all the central space. Though the ActiveE doesn’t use in-wheel motors, it has avoided an internal space-claiming drive train by incorporating its 125 kW electric motor into the rear axle where the differential normally resides.
Accordingly, the batteries are neatly tucked away where a combustion engine, the conventional propshaft and fuel tank would normally be located. The largest portion of the battery pack in the BMW Concept ActiveE is located where and fuel tank would be in the lower section of the vehicle. In addition, a portion of the battery pack is located where the combustion engine would normally reside. Using lightweight components and the lithium-ion battery cells, vehicle curb weight is limited to about 1800 kg / 3900 lbs, and the positioning of the battery pack shifts the vehicle’s center of gravity downwards.
Also, the battery cell layout within the vehicle preserves the near 50-50 weight distribution characteristic of BMW vehicles.
The ActiveE uses a new, advanced lithium-ion battery pack developed jointly with SB LiMotive just for the ActiveE. The battery management system helps achieve a 160 km range largely independently of external climatic conditions. Additionally, the charging period required for the lithium-ion batteries on the European power grid, is just 3 hours at a wall box with a current of 50 ampere at 230/240 volts. In North America, using a high-current (32 ampere continuous) residential wall box, the charge time is about 4.5 hours.
The new synchronous electric motor produces 125 kW (170 bhp), but it’s the exceptionally broad torque of 250 Nm/184 lb-ft available over an unusually broad load range that makes it particularly effective. Maximum torque is available from a standstill as is typical for electric motors, but unlike asynchronous electric motors, the new power unit provides a high level of torque at higher engine speeds and with increased load, the torque only decreases gradually. The torque curve at higher engine speeds is therefore not dissimilar to that of an internal combustion engines.
In the purely electric powered BMW, the driver may control deceleration as well as acceleration through the movement of the accelerator pedal. As soon as the driver’s foot is removed from the accelerator, the electric motor performs the function of a generator, converting the vehicle's kinetic energy into electric power and storing it in the battery pack. Intensive use of this so-called energy recuperation process by the motor increases the range by up to 20%.
At the same time, a brake torque is created which results in effective deceleration of the vehicle. This response enables a very comfortable driving style, especially at medium and constantly varying speeds. In urban traffic, some 75 percent of all deceleration maneuvers are initiated without the need for the brake pedal. During Brake Energy Regeneration function, the vehicle’s brake lights are illuminated.
This brake effect acts on the rear wheels only. When the driver requires a higher level of deceleration, stepping on the brake pedal engages the conventional hydraulic braking system. If an emergency braking maneuver is required during braking, the Dynamic Stability Control (DSC) system applies selective braking and motor management measures to ensure that safe braking is always guaranteed.
The brake system is fitted with an electric vacuum pump which is activated on demand. Along with the Electric Power Steering (EPS) familiar from the production models of the BMW 1 Series, these features contribute to an increase in the overall efficiency of the vehicle.
The lithium-ion battery pack specially developed for this vehicle supplies energy to the motor and all other functions. The high-voltage battery units offer a particularly high storage capacity and durability. For the first time, storage cells are used which were developed especially for use in automobiles by the BMW Group in collaboration with the co-operation partner SB LiMotive. Powerful battery cells are key when it comes to designing production vehicles with electric drive. Through the collaboration of the BMW Group with a joint venture of the companies Bosch and Samsung SDI [SB LiMotive], leading expertise in the area of battery technology and electro-mobility has been brought together. The aim is to use the best available technology in the area of energy storage as part of the development of the Megacity Vehicle.
The lithium-ion batteries of the BMW Concept ActiveE have their own liquid cooling system and intelligent battery management system, which are key elements in increasing both the storage capacity and the durability of the battery cells. These systems also ensure that the long range can be maintained largely independent of external climatic conditions. The high storage capacity is the decisive factor in achieving as long a range as possible. The storage system developed for the BMW Concept ActiveE enables a real-world range of about 160 km/100 miles on a single charge, depending on conditions (FTP72 cycle range is calculated to be 240 km/150 miles in simulation).
The lithium-ion battery pack of the ActiveE can be recharged using a range of power sources. In addition to using a high amperage wall box – a supply system installed in the user's home optimized to reduce charging times– it is also possible to use conventional power outlets or publicly accessible charging stations made available in co-operation with energy suppliers.
In conjunction with the powerful battery technology, the concept of a purely electrically powered vehicle presents additional opportunities for the integration of innovative comfort features. For the BMW Concept ActiveE, a special heating and air conditioning system was developed which is supplied with energy from the high-voltage battery via the vehicle power network. The fact that the heating system and air conditioning compressor are electrically powered means that the desired temperature can be provided inside the vehicle even when it is stationary. The driver can heat or cool the interior before a trip using the auxiliary heating or air conditioning system – an option which is available when the vehicle is connected to a charging station and the battery is fully charged. This ensures that the range is not reduced by the comfort function, but in fact increased. The reason for this is that the energy required for heating or cooling the vehicle within existing connection to the power supply does not need to be drawn from the battery during travel.
The air conditioning systems developed for the BMW Concept ActiveE can also be activated via mobile phone. This option also includes a timer function so the driver can ensure that the vehicle is conveniently pre-cooled or pre-heated before getting into it in the morning.
In addition to the intelligent remote controlled operation of the auxiliary heating and air conditioning, BMW ConnectedDrive offers additional services specially developed for the BMW Concept ActiveE. The main focus here is on the user-friendly and practically oriented relay of precise information on the condition of the vehicle. No matter how far he is from the vehicle, the driver can obtain details of the charge status of the lithium-ion battery and the range of travel this permits. The remote control functions also provide support in searching for a nearby public charging station.
The configuration of the remote control functions is specifically oriented to use scenarios arising in everyday traffic. For example, the driver can go shopping or eat at a restaurant while the vehicle is supplied with electrical current at a charging station. Within a very short time the driver can obtain information on the current charge status of the batteries by mobile phone. The driver can also determine how much charging time is required for the batteries to achieve sufficient energy capacity for the trip home, thus allowing other activities to be planned.
As a next step, the BMW Concept ActiveE will now be used in a trial fleet of electric vehicles. These vehicles are likewise intended for everyday use by private and select fleet customers as part of a large-scale field test. The insights gathered in the process will be fed into the development of an electrically powered serial production vehicle which the BMW Group will put on the market under a sub-brand of BMW in the first half of the next decade.
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