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The lithium revolution
If the electric car has so far not really managed to make its presence felt against the thermic-engined vehicle, which is more energy efficient, it is
coming back in force at the beginning of the 21st century thanks to a major technological breakthrough:
lithium batteries (
Lithium-ion batteries, in particular). Originally used in the world of portable electronics, they made their first appearance in the car industry in 1996 on the
Nissan Prairie Joy prototype, developed with the Sony Corporation.
This new generation of Lithium-ion storage batteries was much more efficient and opened up new prospects for the electric vehicle. Concept-cars and small-scale testing consequently followed. As did general competitiveness. The greatest example was the very sporty
Tesla Roadster, fitted with Li-ion battery packs, and sold on the market since 2005 by the young American firm Tesla Motors. American stars adopted it; from then on, the electric car came out of the shadows and also stirred one’s imagination. Everyone had their eye on this future technology.
In China, the manufacturer
Byd made huge investments in this area, after having presented the F3DM, the first rechargeable hybrid vehicle fitted with Li-ion batteries, in 1998. This led to the American businessman Warren Buffet deciding, to general surprise, to invest $230m in the company, thus acquiring 10% of its capital.
The American group GM is also counting on Li-ion technology to produce its future hybrid model, the Volt, which is supposed to turn around the US motor industry and save the group from bankruptcy.
As for the
Renault-Nissan Alliance, it’s launching a large offensive on the
100%-electric vehicle front with several models to hit the market soon: in particular, the Nissan Leaf and the Renault Fluence. A new age is dawning.
Although the Lithium-ion battery seems to be establishing itself among the majority of manufacturers, alternatives do exist. The French battery manufacturer Bolloré is thus counting on the
Lithium-Polymer battery with its BlueCar.
The advantage of this type of battery: they are more stable (and therefore more reliable) and have a greater mass capacity (increased range of around 250 km). The only disadvantage is that they don’t withstand rapid recharging and have lesser tolerance for normal recharging cycles through their life.
In addition,
the old nickel-metal hydride (NiMH)
batteries are still in use in current hybrid vehicles, such as the Toyota Prius. This is because they cost less and improve the thermic engine’s power.
The advantages of Lithium-ionIn comparison with nickel-metal hydride (NiMH) storage batteries,
Li-ion batteries are improving across all levels (size, weight, power and performance). They effectively command a greater energy capacity and therefore a greater storage capacity. The outcome is that they allow an electric or hybrid vehicle to have a finally acceptable range, of
between 100 and 200 km (between around 62 and 124 miles), that is 2 to 3 times more mileage than previously.
Another advantage of Li-ion batteries is that
they don’t suffer from memory effect and are therefore not at risk of incomplete recharging cycles.
This is unlike previous batteries, which, in case of partial charging, demonstrated a sharp fall in capacity and thus premature wear and tear.
In addition, huge progress has been made in terms of
durability: a Lithium-ion battery is supposed to
retain 80% of its capacity after its sixth year of life and until its tenth year.
"A great general autonomy has been reached", assesses Bruno Monsuez, Professor-Researcher at ENSTA (Ecole Nationale Supérieure de Techniques Avancées*).
* - ENSTA is a top French engineering school Safety under control
Just like any energy storage system, a battery is not an inert object. On account of its
high energy density, it is capable of causing short circuits, which could provoke fires or even explosions. "
The higher the amperage, the higher the risk" points out Bruno Monsuez, of ENSTA. "
Therefore, one has to optimise the assembly and the positioning of the different elements, and ensure that they are isolated from each other".
Considered dangerous for a long time, Li-on vehicle batteries have become safe. "
Today, the majority of risks have been removed. Many crash-tests have been carried out over the past ten years and we now have good feedback from these." Much precaution is taken as far as the conception of batteries is concerned, particularly in terms of the materials (based on manganese), the structure (laminated to control the heat) and the process.
Conceived as a compact block that is isolated from the rest of the car, the battery has to be able to resist shocks and be protected as much on the outside as on the inside. So all the elements of the battery are assembled within the same metallic housing or in composite materials, and not distributed around the vehicle in order to facilitate their integration.
A
battery is solid but heavy, weighing
between 150 and 300 kg. It therefore necessitates specific installation. It is placed, in general, in a ventral and central position at chassis level, as low and as flat as possible in order to optimise dynamic behaviour and to avoid the risk of being turned around.
Normal and rapid recharging
The
complete charge of a standard Li-ion battery lasts around
4 to 8 hours.
The operation is simple and can be carried out anywhere from a mains socket (see next section), at home, at work, in the street, car parks or shopping centres. Potentially, there will be more charging points than there are stations distributing fuel.
Another advantage of lithium-ion is the
rapid charge, which can ‘fill’ the battery up to
80% in
20 minutes thanks to specific hardware and high-tension source (400 Volt, 63 Amp, three-phase).
However, according to experts,
almost 95% of requirements will be satisfied by the "normal" charge (230 Volt, 16 Amp, single-phased).
Nevertheless, the rapid charge will remain necessary to reassure the user or to provide help in case of breakdown. It could also be envisaged by means of complementary energy sources, such as
solar or wind. This is an interesting solution for companies capable of producing their own electricity as part of port infrastructures (bus terminals, large fleets…).
Standardisation of sockets, wireless technology and exchange platforms.
Car and parts manufacturers, and also energeticists, are currently working to define the normalised and universal electric sockets and bases in order to allow users to easily recharge their electric or rechargeable-hybrid vehicle.
Charging sockets for electric vehicles are different to standard domestic sockets and will therefore be "dedicated" and "specific" in order to withstand the high thermic and mechanical pressure (being plugged in and unplugged frequently).
They have to be able to adapt to both the slow and rapid charge, and also
be installed on any site (car parks, curbside, homes…) and all over Europe.
A Franco-German working party, led by EDF and Daimler, has already submitted its conclusions with a view to future European normalisation. In the meantime, there are already various connectors for electric vehicles on the market: the Japanese company Yazaki and the German company Mennekes both offer dedicated products.
In future, it will also be possible to
recharge an electric or hybrid vehicle without a direct connection, therefore wirelessly, by using the
principle of induction: a magnetic field that generates a current on a distant coil. Nissan is already working on this system and plans to offer it as an option on the Leaf.
As for the American company Evatran, which is based in Virginia, it intends to launch a
wireless recharging system that is compatible with several kinds of vehicles at the end of 2010.
The other solution and the alternative to manual battery recharging is
hire. The principle is to
replace one’s battery in a station instead of recharging it.
The removal-installation operation is completely automated and takes around three minutes. This solution, offered by the Californian company
Better Place in partnership with the Renault-Nissan Alliance, is already in operation in Israel. The project necessitates the installation of a large nationwide infrastructure, but could eventually
bring the cost of batteries down.
