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Electric Vehicles | Mitsubishi Motors: i-MiEV


Global warming, brought on by population increase and the destruction of the natural environment, is becoming an increasingly pressing problem. Coupled with this, the sharp rise in energy prices has prompted the development of eco-friendly cars which take in consideration the diversification of energy that we are already seeing. Demand for eco-friendly cars is also rising in the face of the environmental and energy circumstances of today.

Of all the eco-friendly models currently being developed, electric vehicles (EV) are of particular interest for one significant reason: they do not generate any CO2 emissions whatsoever while driving.

In an EV, the conventional engine has been substituted with an electronic motor and a battery used to power it. The EV also carries an onboard charger, a storage battery, and control devices. The car is powered by the electricity stored in the battery, instead of an engine that runs on gasoline.

The absence of a gasoline engine means no harmful gas emissions during driving. Compared to conventional vehicles, EVs generate less noise and vibrations. Perhaps the greatest advantage of EVs, however, is the fact that energy can be reclaimed under braking and reused to charge the vehicle’s capacitor.

Electric Vehicles Run On Batteries
Unlike a conventional gasoline-powered car, an EV uses electricity not fuel, uses an electric motor instead of gasoline engine as its power source. This means they generate no harmful gases or CO2 emissions while driving.

It seems that the ‘engine’ of an electric vehicle should be the driving electric motor, but the EV simply will not run if the battery power is low. However powerful the motor carried on an EV, its output is entirely dependent on the battery power. Improving the battery power, however, has associated cost-related problems and there is a need to reduce these costs.

The associated problems are not only to do with cost. The lithium-ion batteries required for EVs have completely different specifications from those used in computers and mobile telephones. This is partly because lithium-ion batteries for EVs must be extremely safe to use. That safety, however, is of a different nature than that required for computers. The battery of a laptop computer normally comprises 6 cells, but for an EV that number rises to nearly 80. As the connections between cells become more numerous, the risk that failure in one cell will adversely affect other cells also increases.

These problems, however, have been overcome with Japanese technology. Much of the technological advancement and diversification seen in electronic devices thus far have been made possible by the emergence of lithium-ion batteries, which have a higher energy density than nickel-metal-hydride batteries. In 1991, Sony Energy Tech was the first to successfully begin high-volume production. Today, Japan accounts for a significant portion of the lithium-ion battery market, with SANYO Electric, SANYO GS Soft Energy, Sony, Panasonic Energy, Hitachi Maxell, and NEC TOKIN among the principal market players. Now, Lithium Energy Japan has begun high-volume production of EV-use lithium-ion batteries, specifically for the i-MiEV by Mitsubishi Motors. Alongside battery manufactures, leading automobile manufacturers, including Toyota, Nissan Motors, and Honda, are committing significant resources to lithium-ion battery-related research.

Mitsubishi Motors: i-MiEV
① Driving range on one full battery charge
160 km on 10-15 mode. Cruising distances fully suitable for everyday general use have been achieved.

② Charging time
The i-MiEV can be charged with AC 100V or AC 200V power. It takes around 14 hours or 7 hours, respectively, to fully charge the battery from empty using a household power source.

③ Identical packaging to gasoline engine models
The i-MiEV body is 3,395 (L) x 1,475 (W) x 1,610 mm (H), making it almost identical to the conventional gasoline engine model (the i-MiEV is 10 mm taller). The cabin length, width, height, and cargo capacity are also identical to the conventional model. This has been achieved by installing the motor and inverter in the space that would otherwise have been used to house the engine and transmission. The 88-cell lithium-ion battery is fitted under the floor of the wheelbase.

④ Motor
The onboard motor is a permanent magnet synchronous motor with the following specifications: maximum output of 47 kW (66 ps)/3,000–6,000 rpm, and a maximum torque of 180 Nm (18.4 kgm)/0–2,000 rpm. The curb weight of the EV itself is 1,100 kg, which is 200 kg heavier than the conventional gasoline model, but it has recorded improved performance over the gasoline model due to the motor, which can produce maximum torque from 0 rpm onwards. The EV can accelerate from 0–80 km/h in 10.6 seconds (the i-Turbo gasoline model records 11.2 seconds) and from 0–400 km in 20.6 seconds (20.9 seconds for the i-Turbo). Its passing acceleration performance at 40–60 km is 2.8 seconds (4.0 seconds).

⑤ Battery
Contains a high-capacity lithium-ion battery pack as a traction battery, produced by Lithium Energy Japan, a company jointly established by GS Yuasa, Mitsubishi Corporation, and Mitsubishi Motors. The pack consists of 88 lithium-ion 3.7 V/50 Ah cells connected in series to deliver 330 V of total voltage and 16 kWh of total energy output.

Mar 11, 2011

About the author
Kaori Shimada is a reporter for Japanest NIPPON
(Special site in Mitsubishi Motors Corporation)