Fullscreen HTML5Med Res (??MB)HTML4

Perhaps the most remarkable thing about the Mitsubishi i-MiEV is that it is so unremarkable. It is a fully electric vehicle but more importantly, it is a compact hatchback that can transport four adults practical distances in comfort, after just a few hours of charging. We drive Mitsubishi’s i-MiEV Electric Car by Nicholas Vinen 10  Silicon Chip siliconchip.com.au D o you think that practical electric cars are still in the future? We had a ride in this one which has already been in use on Sydney’s streets for a few months. It is being evaluated by Roche Pharmaceuticals Australia, on a special lease from Mitsubishi Motors. Our demo ride was organised by Malcolm Faed, whom readers may siliconchip.com.au remember from the article on his electric ute conversion (SILICON CHIP, June 2009). Besides the lack of engine noise and the large lettering advertising the fact, you would be hard-pressed to tell that it is an electric car. Acceleration is comparable to that of a petrol engine of around 1.3L, as is typical for cars of this size. All the usual accessories are present: air conditioner, heater, radio and CD player, satellite navigation, anti-skid power brakes, power-assisted steering, HID headlights, keyless entry and so on. Other than to say that performance is perfectly adequate, two facts that you need to know about this car is its range (around 100km) and its charging February ebruary 2011  11 (Left): under the floor of the small boot lies the battery charger/inverter and motor controller. These are normally hidden by the boot floor. They do get rather warm in operation, hence the warning signs (we wouldn’t leave the ice cream in the shopping bags too long in the boot, either!). (Below): lifting the bonnet reveals . . .not a great deal! For a start, it’s tiny and there’s no motor under here. But what you do get are the various fluid reservoirs (just like a normal car!), the service battery (just like a normal car!), air conditioner (just like a normal car!) and so on. time, seven hours from a standard 230VAC 15A mains outlet or under an hour with an external 3-phase 50kW quick charger. For most city commuters, these figures make it a practical proposition. Impressions Riding in it for the first time, we noted good visibility all-around and a small turning circle. Internal space is adequate, with sufficient headroom for all but the tallest occupants although leg room is restricted. The boot is small but will fit a large suitcase or several bags of groceries. Mitsubishi have put in some nice touches such as motorised folding side-mirrors and a windscreen washer system which sprays water on the windshield from the single large articulated wiper arm. The dash is uncluttered and is dominated by the digital speedometer, battery gauge and large navigation/radio con- The multi-cell lithium-ion battery pack is rated at 16kWh and when charged, delivers 330V. It is located under the centre of the vehicle. 12  Silicon Chip trol screen in the centre. Not only is the electric engine very quiet but road noise is also kept well under control. We measured below 60dBA at 60km/h with the air conditioner fan at a medium setting. In fact the most obvious noise while driving is the occasional sound of the brake assist vacuum pump. It runs for a second or so after pulling up at traffic lights. It is not particularly loud but is noticeable, simply because the car is quiet. There are nowhere near as many readouts showing the state of the electric drive system as compared to the Toyota Prius or some other hybrid/ electric cars. We don’t think this is a disadvantage; the i-MiEV has displays for batsiliconchip.com.au The motor and transmission are somewhat hidden up under the rear of the vehicle on the rear axle, as this photo shows. There is no reverse gear as such. Immediately above the motor is the charger/inverter, with the battery pack forward. tery charge state and estimated range remaining. Anything more than this could be a distraction for some drivers! Our brief drive of the car was on a warm summer morning with temperatures in the high 20s. The air conditioning did provide some cooling but with the large windows we’re not sure how comfortable it would be on a hot sunny day. Since the AC draws around 1kW from the battery pack, it will reduce the range by 5-15%, depending on the outside temperature (ie, compressor duty cycle) and trip duration. Technical details The i-MiEV is externally quite similar to many other four-door compact hatchbacks and is in fact derived from a Japanese Kei car (“light automobile”), the Mitsubishi i. The main points of difference are the Lithium Polymer battery between the floorpan and seats, the electric motor and transmission on the rear axle and the battery charger and controller fitted under a hatch in the boot. The motor is a three-phase permanent magnet synchronous type which produces 47kW and 180Nm. It is driven from a variable frequency and voltage inverter for speed control, which is named the MCU or Motor Control Unit. There is no reverse gear; to go backwards the motor simply spins in the other direction. As can be seen from the graph below, while the motor is not particularly powerful, it has excellent torque at low RPM and this provides quite good acceleration from a stand-still. Top The dashboard would not be unfamiliar to anyone driving a conventional vehicle. The gauges might need a second look, though, especially the “fuel” gauge. In the centre of the dash is the large LCD display which is essentially GPS information (with a beautiful big map!) but it can also be programmed to display other vehicle information. siliconchip.com.au February 2011  13 There are two methods of charging. At left is the mode most people will use, from a standard 230V 15A power outlet plugging into the on-board charger. This takes about seven hours to charge the batteries to 100%. But if you’re in a real hurry and can find a 3-phase, 200V 50kW charging station (not here yet!), the socket on the right will charge the batteries to 80% in 30 minutes. speed is around 130km/h. The battery pack weighs 230kg and has a capacity of 16kWh at 325V. According to Mitsubishi the vehicle’s range is 160km but once traffic, heating and cooling, headlights and so on are taken into consideration, it will be closer to 100km. To get the fastest charge rate (from flat to 80% capacity in 30 minutes) you need a 3-phase, 200V 50kW “Japanese Quick charger” which connects to the passenger-side charging port. Since these will only be provided in major cities, most users will instead charge the vehicle from a 230V 15A mains outlet via the driver’s-side charge connector. Both connectors are covered by flaps just like those used on petrol or diesel cars. The controls are just like those of a regular automatic car. As well as the usual Park, Reverse, Neutral and Drive positions, the “gear” lever also has an Economy setting which limits motor performance to increase range and a Brake position which provides regenerative braking. This is comparable to engine braking in a petrol or diesel engine, with the added advantage that some of the vehicle’s kinetic energy is returned to the battery to charge it “on the run”. This will obviously increase the vehicle’s range. The heater and cooler are both driven from the main battery pack although the circulation pump for the heater runs from the 12V service battery (located under the bonnet). The electric element heats a fluid identical to internal combustion engine coolant (ethylene glycol and water) and this in turn heats air. Like the drive motor, the air condi- The electric motor is a permanent magnet, synchronous type rated at 47kW. It can produce 180Nm of torque for good lowspeed acceleration 14  Silicon Chip tioner compressor is also a permanent magnet brushless type, with its own inverter. Benefits While the most obvious benefit of having an electric car is never needing to go to a petrol station, there are other reasons to want one. One significant advantage is that it requires little maintenance. Occasional servicing is necessary as there are fluids to replace (transmission oil, heater coolant etc) but there are relatively few moving parts so maintenance costs should be low. The relative simplicity of electric motor drive also means there is far less to go wrong than a petrol car. There is no fuel pump, no gearbox, no radiator, no head gasket to blow and so on. Of course, it is possible that the inverter or controller (or some other And here’s another view of the on-board motor controller shown earlier, obviously out of the vehicle (in fact, on display at a show). siliconchip.com.au significant component) could fail but we doubt it will be a common occurrence. In fact the largest maintenance expense is likely to be the eventual replacement of the battery pack once its useful life has been exhausted. Testing by Mitsubishi shows that the battery pack retains over 80% of its original capacity after 1,000 charge/ discharge cycles. This suggests that the pack will last at least five years for a typical commuter and probably longer. Bottom line Some readers will be asking themselves: where can I get one and how much does it cost? We have some bad news for you. There aren’t many i-MiEVs on the road outside of Japan and they are all on special leases. That may change in a few years but for now, they are not available to the general public in Australia. As for the price, the vehicle costs around AUD $45,000 in Japan and we would expect them to cost at least that much when they are sold here. It isn’t all bad news, though. Competition is on its way to the plug-in electric vehicle market. As we are writing this article, Nissan are delivering the first production LEAF electric cars in Japan and North America. The LEAF has a similar size, range and cost as compared to the i-MiEV, with a more powerful motor (80kW). It costs $35,000-$47,000 (depending on where it is sold). While these new electric cars are definitely practical, their limited availability and high price are the biggest obstacles to widespread adoption. As time and technology marches on, that should change. SC SPECIFICATIONS • Electric Motor: (10.15 mode, gross weight 1,250kg) Permanent Magnet Synchronous, 47kW 180Nm of torque (from stall) Maximum Output (kW/rpm) 47/3000-6000 Maximum Torque (Nm/rpm) 180/0-2000 Power Consumption (W.h/km) 125 Range (km) 160km • Batteries High capacity 330V lithium-ion 16kWh capacity • Charging Time 230V (15A) Connection: seven hours to 100% 3 Phase 200V 50kW connection: 30 mins to 80% • Drive Modes: D – optimised performance E – optimised economy B – optimised regenerative braking • Dimensions & Packaging: Overall Length 3395mm Overall Width 1475mm Overall Height 1610mm Wheelbase 2550mm Front Wheel Track 1310mm Rear Wheel Track 1270mm Seating Capacity 4 people • Standard safety features: Reinforced Impact Safety Evolution (RISE) body construction ABS brakes Dual front airbags Traction Control • Claimed running cost: 1/3 that of a conventional (petrol) vehicle 1/2 that of a petrol HEV 1/9 that of a petrol vehicle when charged at off-peak rates Acknowledgement: thanks to Roche Products Pty Ltd and Malcolm Faed for arranging the demonstration. The basic configuration of the i-MiEV electrics. It relies heavily on the CAN bus and computer monitoring and control. With the i-MiEV, Mitsubishi have gone away from their earlier-favoured EV “motor in wheel” designs to this somewhat more traditional motor-driving-transmission configuration. Low-speed torque of the iMiEV compared to a conventional (petrol) engine. Maximum torque is at zero rpm. Battery capacity (and discharge) depends a lot on the way you drive and also the terrain (hills!) encountered. siliconchip.com.au Change in motor power as the battery discharges is affected significantly by temperature. (DOD= Depth of Discharge). February 2011  15