The aXcessaustralia Hybrid Electric Car Project

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concentration’, towards the tab during high-rate charge ordischarge. As heating within the battery is related to boththe square of the current and the resistance of the battery(i.e., Ι 2 R), high, localised current densities can result inlarge heating effects in these regions.The inclusion of a second current takeoff decreases thecurrent density at each tab and considerably reducesheating effects. The capacity and cycle-life under HEVand EV conditions is also much improved compared tocommercial designs. Once again, this is a direct result ofthe dual-tab design. Capacity increases are a result of thebattery plates operating at a uniform temperature, whichallows ‘even active-material utilisation’ throughout theunit.Improvements in cycle-life are a result of lower operatingtemperatures, which act to slow down normaldegradation processes, and also improvements in positivegrid design, which reduces corrosion within the battery.Overall, the Double-Impact battery is safer to use andprovides improved cycle life and capacity under bothHEV and EV duty, relative to that of current commercialunits.ENERGY SUPPLY UNIT (ESU)Figure 11: The Electric Traction Motor andReduction GearboxThe motor is water-cooled. It is controlled electronicallyand its characteristics are therefore programmable. Forthe aXcessaustralia car the motor is programmed to givea wide constant power characteristic, thus eliminating theneed for a mechanical gearbox.POWER CONTROLLERSThe ESU consists of a petrol engine connected to agenerator. The petrol engine is a CMC Power SystemsLtd Scotch Yoke (SYtech) engine. The advantage ofscotch yoke technology is the improved combustionefficiency and low vibrations. The pistons travel in asinusoidal motion that leads to improved fuelconsumption and lower emissions.Figure 12: Power ControllersPower controllers take up a large amount of space in theaXcessaustralia car. If the car were to be mass-produced,the power controllers could be designed to be muchsmaller (about the size of a small briefcase). For budgetreasons it was decided not to carry out the miniaturisationfor a one-off car.Figure 10: The CMC Power Systems Sytech engineELECTRIC TRACTION MOTORThe ETM uses CSIRO switched reluctance motortechnology that was specifically developed for traction(vehicle and train) applications. The features of the motorare very low cost, full torque at low speed, and a widespeed range.LOW ROLLING-RESISTANCE TYRESLow Rolling-resistance tyres are used on theaXcessaustralia car. At low speeds, say driving in the city,the tyre rolling resistance is the dominant loss in a car.The challenge for the tyre manufacturer was to produce atyre that combines the handling, braking and wearcharacteristics of a normal tyre with a reduced rollingresistance. This has been achieved using special rubbercompounds, tyre profiles and tread patterns.David Lamb6
REDUCED-MASS MATERIALSThe aXcessaustralia car uses a proven, crash-tested bodystructure dressed with steel body panels made from steelformed in innovative low-cost tooling. Carbon-fibrepanels are often cited as the ideal material for electric orhybrid cars, but steel was selected for the car becauselight-gauge steel was able to match the weight andstrength targets at the lowest cost for mass production.Utilising the latest in steel technologies, theaXcessaustralia car incorporates Australian BHP “BakeHardenable” steel, increasing the dent resistance of thevehicle and allowing down-gauging of the thickness ofthe panels while maintaining performance. Thickness hasbeen reduced to 0.7mm, saving more than 25% of theweight in the vehicles outer panels versus conventionalmaterial. These savings are crucial to achieve thestringent environmental and performance targets.Several other components were mass-optimised toillustrate CSIRO expertise in mass reduction using lightmetals. Figure 13 shows a sample of the optimisedcomponentry.the front. In the rear of the car is the Energy Supply Unit(internal combustion engine and generator) surroundedby the supercapacitor pack. The battery pack is locatedunderneath the rear seats.RESULTSMuch work has gone into modelling the optimumpatterns of energy management to achieve the objectiveof 50% reduction fuel consumption and greenhouse gasemissions and 90% reduction in pollutants.The battery pack provides enough energy storage toallow the car to complete an urban drive cycle underelectric power only. This means that the car gives therange and performance and low emissions of other hybridcars, but also will run in zero-emission, all-electric modein areas that are particularly environmentally sensitivesuch as city centres.In this way the aXcessaustralia car combines theperformance and very good emissions of other hybridvehicles with the zero emission of an electric vehicle.The car can also be charged overnight on low tariffelectricity to reduce running costs further. This is inaddition to the 50% saving in fuel compared with theequivalent non-hybrid car.SUMMARYThe aXcessaustralia car is a remarkable achievement onthe part of the automotive components industry inAustralia in partnership with CSIRO and Government. Itdemonstrates hybrid-electric technology and has helpedindustry learn about emerging technologies. The projectshows Australian industry’s best innovations in a uniqueshowcase for demonstration to the global automotiveindustry.Fig. 13: Aluminium and magnesium componentryLAYOUTFigure 14: aXcessaustralia LEV Powertrain LayoutFigure 14 shows the layout of components in theaXcessaustralia car, with drive motor and transmission atDavid Lamb7
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The aXcessaustralia Hybrid Electric Car Project

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