The Independent American Magazine for all Mini Owners
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battery is partially depleted, then the “range extender” fires up and starts generating electricity. No more fear of getting stranded, and one can fill ‘er up at any gas station! A Lighter, Cheaper Package Because the two largest barriers to adoption of electric cars is the fear of running out of juice, pure electric cars have large battery packs to give them a usable range. The battery pack in the Tesla is 900 lbs! Not only is it very heavy, but the battery pack is also very expensive. Because series hybrids can run on conventional fuels as well as stored charge, the manufacturer can choose to put in a smaller battery pack. This makes the batteries lighter, and saves a bunch of money. The Chevy Volt has an all- electric range of 40 miles, instead of the 200 miles that the Tesla can go, or the 100 miles (or so) that the MINI-e can go. In the case of the Tesla, this would give the design team almost 600 lbs of eliminated battery weight to play with, without increasing the overall weight of the vehicle. This is the approach that the Fisker Karma and Chevy Volt take. The Karma has an electric range of 50 miles, and the Volt 40 miles. Energy Efficiency If you look at where all the power goes in a conventional internal combustion engine (ICE) vehicle, a very small amount actually drives the wheels. Lots is lost to idle, driveline friction, exhaust heat and the rest. Another significant loss of energy is that the engine is rarely run at peak efficiency, as RPM are coupled to the wheels. In fact, the drive to keep the engine at a more efficient operating point is why Mercedes Benz introduced an 8-speed automatic transmission! Since the engine of the range extender only works at one RPM, no more hyper complex (and very expensive) transmission is required! The overall effect of this is a close to doubling of the energy efficiency of the entire driveline. The Fisker Karma uses a 260 HP turbocharged direct injection 2-liter 4-cylinder engine to supply power to the 406 hp of electric motors that can give the car its luxury, sport sedan performance. The AVL package is aimed at a very different segment indeed. One of the reasons that companies like MINI shy away from any type of hybrid is that they think of packaging the hybrid system to an existing small powerplant. On the new MINI, there just isn’t any room to put that extra stuff under the hood. AVL wanted to create the smallest package possible, so they chose the Wankel rotary layout. Their pure range extender has a single rotor Wankel coupled directly to a permanent magnet generator to create a very compact and light package. And yes, for higher energy demands, a second rotor could be used while still making the package significantly smaller than your typical inline 4-cylinder engine. When all these bits were put together, AVL created a series hybrid in a new MINI Cooper chassis that still retained the rear seats, delivered much better in town efficiency (where electric drive really shines), and yet wasn’t limited by the rather meager overall range that limits the MINI-E range and potential market. When I first learned of this car, I was really excited! I love efficient technology, and this seemed to hit the sweet spot: great chassis, even better efficiency, and for those that drive less than 30-40 miles a day, a running cost of a few cents a mile. I was really disappointed to learn that AVL only created this to show off what can be done as a showcase for the actual automotive manufacturers. However, even though I can’t buy one (it would be perfect for my wife’s commute to work, 11 miles each way), I do hope that the car manufacturers realize that the advantages of the series hybrid powertrain are no longer limited to larger cars. I think that if MINI were to build this car, it would be a great seller as a practical city car, giving the benefits of full electrics for the short hop around town, yet still allowing the owners that drive in the country that would cause an owner of a full electric to cringe. While this doesn’t look like any MINI made by BMW, the packaging here contains all the electronics: range extender generator and control electronics required. Even though there are a couple wires that don’t look factory, it shows that this technology could be delivered to the market quickly. A series hybrid doesn’t eliminate all the losses, but idle, standby and driveline losses are almost completely eliminated. Also about half of what is called “engine losses” can also be eliminated. The remainder of the engine losses are heat that escapes through the exhaust. Since the car has a battery pack, regenerative breaking can also recapture even more energy. :DLW WKDW ÀOOHU GRRU LV RQ WKH ZURQJ VLGH 7KH EDWWHU\ SDFN RQ WKH AVL demonstration vehicle can be charged by plugging in, or from the compact range extender package. The range extender runs on gasoline, VR WKH ÀOOHU GRRU RQ WKH GULYHU·V VLGH RI WKH FDU LV VWLOO WKHUH IRU IXHOLQJ XS DW DQ\ JDV VWDWLRQ 6D\ JRRGE\ WR UDQJH DQ[LHW\ VD\ KHOOR WR PXFK LPSURYHG DURXQG WRZQ JDV PLOHDJH Issue 29 MC2 Magazine 47