By on February 25, 2013

The Tesla vs. New York Times controversy has finally left the news cycle, forgotten in less time than it takes a Model S to juice up at a Supercharger station.  Meanwhile, BMW is ready to introduce its new range of “i” vehicles, which will conveniently dodge the whole question of range anxiety.

Select European outlets were invited for ride-alongs in BMW’s new i3 city car and i8 supercar. The impressions gleaned from ride-alongs are generally next to worthless, but the technology being used by BMW is worth examining. Rather than a pure EV, BMW will be adopting a three-pronged approach – a pure EV, a range extender and a plug-in hybrid.

The i3, a small hatchback meant for urban driving, will adopt the BMW ActiveE’s drivetrain, with an electric motor mounted in the rear, making 168 horsepower and 184 lb-ft of torque. Maximum range is said to be 140 miles, though 80-100 miles is a more realistic figure according to BMW. The i3 will be slightly bigger than a Mini Cooper, but will weigh just 2750 lbs and git 60 mph in 7.2 seconds. And unlike the Mini, it’s rear-drive.

But the most interesting aspect of the i3 is the range extender option. Unlike the plug-in hybrid option on the i8 supercar (which uses a three-cylinder turbocharged engine and an electric motor to power the wheels), the range extender in the i3 is strictly used to help maintain the battery’s charge if it falls below a predetermined level. It does not power the drive wheels under any circumstances. The 650cc parallel-twin could help increase the i3’s range to as much as 200 miles according to BMW, though specifics were scant.

As much as pure EV enthusiasts may scoff at the idea of any carbon-emitting technology sullying the zero-emissions dream, range extender technology could become prominent as a means of expanding the viability of electric vehicles. Small motorcycle engines (like the i3) and even rotary engines are being floated as possible solutions, while other more radical possibilities are being researched right now. Serenergy, a Danish firm, makes a fuel cell system based on methanol that could be adopted for this purpose. While methanol fell out of vogue in the 90s, the prospect of creating it from sources like solid waste has helped revive interest in methanol as a biofuel. On a broader scale, range extenders could alleviate one of the main psychological deterrents to EV adoption – the fear of running out of juice, rendering you totally stranded – by offering a reliable fail-safe in case of battery depletion. And if it’s a rear engine, rear drive compact, all the better for those of us who still enjoy the act of driving.

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69 Comments on “BMW: The Ultimate Range Anxiety Cure?...”


  • avatar
    KixStart

    ICE to wheels is more efficient than ICE to generator to battery to motor to wheels.

    I’m not saying BMW’s idea is bad or won’t work but the temptation is there to put the motor directly to work. Otherwise, you might just as well mount it on a trailer and then you don’t need to carry around an extra 300lbs when you don’t need it.

    • 0 avatar
      Brian P

      That’s the issue that has dogged every series-hybrid … too many energy conversions.

      A 650cc twin shouldn’t weigh 300 lbs, though – more like 100-ish, although the generator and so forth will add a bit more. I have one motorcycle with a 12 hp 125cc single, and I can carry the entire engine/transmission with one hand. The smart’s 3 cylinder engine only weighs about 50 kg (110 lbs).

    • 0 avatar
      Dr. Kenneth Noisewater

      Here’s a Q.. Would an accessory trailer with, say, a 2cyl boxer motor as a generator need to be emissions-tested?

    • 0 avatar
      ClutchCarGo

      The problem is that you don’t know when you’ll need the ICE generator. It has to be onboard in order to be available whenever needed. Overall efficiency is not the point of an onboard ICE, it’s only there for backup.

      • 0 avatar
        KixStart

        Clutch,

        Not necessarily. If this was a common enough solution, renting them would become a viable business model. AAA could bring you one on a truck. And I do think overall efficiency is important… getting out of town implies a lot of miles, which I’d hate to do at 30mpg, if I’ve shelled out for an EV.

        Doctor,

        I would expect so… In CA, anyway, it would.

        Brian,

        I may be overstating, it yes. However, in addition to the engine in its most minimal form, we need a fuel tank, exhaust system, radiator & venting for it.

        Then, to get it inside the vehicle body, we’ll want a firewall, I think and the overall vehicle must be bigger to allow for the room taken up by the engine, which makes the vehicle heavier.

    • 0 avatar
      MeaCulpa

      provided that the engines are identical yes. An engine optimized for a single load can be made more effective – especially diesels, diedel engine life is also greatly improved by running the engine at a constant and HIGH load 80-90% of max load/pressure, idling kills diesels – so the difference needn’t be large or even noticeable. Engines can also be made less complicated as VGT turbos or Vanos is not needed.

    • 0 avatar
      Vega

      No it’s not, because your internal combustion range extender can run at the most efficient point of it’s performance envelope and can be smaller than the comparable ICE. That more than offsets the inefficiencies of conversion. Remember: The I3 has 168hp and bags of torque (electric engine, the range extender is only a 650cc motorcycle engine.

  • avatar

    If anyone’s going to do it right, it’s BMW.

    They invent shit all the time.

    Trust.

  • avatar
    KixStart

    I hope they take a bit of extra trouble and use the Atkinson cycle tricks for higher efficiency.

    • 0 avatar
      carve

      since it typically will sit unused, maximizing efficiency should take a back seat to minimizing weight. Light weight will help maximize your efficiency under battery power- most of the time.

      • 0 avatar
        redav

        That’s a trade off that has to be made if the generator has to be on-board. If the generator is in a detatchable trailer, then weight is a much smaller issue because you would not lug it around except for long trips, which will likely be on the hwy, and weight isn’t a problem when driving at a steady speed. Also, since it would only be used to maximize range, it could then be optimized for efficiency.

  • avatar

    “range extender” implies that all you’re doing is extending the range, until you have to charge the damn thing again, and at 200 miles, the i3 isn’t going to do any better than the Tesla did. The trailer thing–who wants to have to have a trailer flopping around back there all the time? The specter of that just underlines the fact that BEVs aren’t ready for prime time. Which is what the editor of Green Car Journal said in the lead editorial of the latest issue.

    Now pass the petroleum, please!

    • 0 avatar
      Carlson Fan

      Right on! I pull trailers year round. The last thing I want is another trailer to store and maintenance. Put the back-up generator in the car where it belongs. A pull behind is an awful idea. Ever tow a trailer down wet, salty, MN roads in the winter?

    • 0 avatar
      redav

      Ready for prime time? A Corvette sucks for moving a sofa–it must not be ready for prime time. A Miata sucks for towing a boat–it must not be ready for prime time. An F-150 sucks on a race track–it must not be ready for prime time. Lots of cars suck at things other cars are good at. No one has ever claimed that EVs are good at cross country trips, but why should they be when other perfectly fine cars suck just as bad (or worse) at at other common tasks?

      “Range extender” removes charging from the equation. It doesn’t mean you now have xx mi to find a charger–rather you have xx mi to find a gas station. Sure, it’s a band-aid, but so is a luggage rack or tow hitch.

      No doubt trailers are not the neatest or most convenient solution, but they wouldn’t be back there all the time–only when driving long distances, which we’ve already established is not the purpose of EVs, anyway. (Using that against EVs is like saying you shouldn’t own a Civic because you have a boat–you just don’t use the Civic to tow said boat. Don’t use the EV for the family vacation.) Storage certainly is a pain, but why even own it when you can rent it? Again, since that’s not the purpose of EVs, they shouldn’t be used that way very often, so rentals become a viable option.

      • 0 avatar
        mkirk

        Owning multiple cars for multiple purposes is not a free ride. I have my wife’s family hauler, My Miata for commuting, My Land Cruiser for pulling my camper, and currently a bike that was my commuter before I got sent up North last tour. 4 vehicles don’t maintain, register, and insure themselves and parking and storing them are a pain and I don’t even live in an urban area. I won’t even get in to the fun of moving them all every few years.

  • avatar
    APaGttH

    Wait, I’m confused. Does this mean BMW has invented a Chevy Volt / Cadillac ELR?

  • avatar
    Mandalorian

    Why not just put a whole bunch of pin wheels on the roof?

  • avatar
    carve

    I’ve been advocating a high power-to-weight ratio engine of 10-50 hp for a long time- figure sufficient power to maintain 70 mph on level ground. You could even sacrifice emissions, durability and efficiency for weight, since it won’t be used often…perhaps 30,000 miles over the life of the car. Mount it to a receiver hitch, couple it to a generator, or maybe a reverse PTO to drive the wheels, or perhaps even a 5th wheel. When you want to do a long drive, just have it run at full-tilt anytime you’re moving, and use your electric power to aid acceleration. You could even set it up to have your electric drivetrain to go into regen-mode when there’s excess power available from the engine. This would give you a through-the-road hybrid effect, saving the large mass and expense of a seperate generator.

  • avatar
    gslippy

    BMW may get something to work, but I’m not sure people will want to pay BMW prices for it – subsidies or not.

    Also, I’m wondering how they achieved the combination of 168 HP, 2750 lbs, and 90 miles nominal range. Because that’s a power/weight ratio that’s twice as high as the Leaf – impressive.

    Answer: Carbon fiber body, £38,000 ($57600 USD). Now I get it.

    • 0 avatar
      APaGttH

      So BMW has essentially build a carbon fiber Volt, with, if it is a Euro city car a likely even more cramped interior, for base Tesla S and likely Cadillac ELR money? Somehow I am supposed to be awe struck by this??? I mean the carbon fiber body is cool and I get that British pounds do not translate 1:1 to US dollar price in all situations – but color me very underwhelmed and left even further confused on how BMW has come up with the all solving answer to range anxiety?

      Wouldn’t the correct answer continue to be General Motors in its maligned, over engineered, politicized, second attempt at an electric car that hate it as much as you want, even when you chafe out fleet sales is the top selling plug-in, series-hybrid or pure electric in America today.

      I realize to some that is like saying the Volt has limited eye sight in its right eye in bright light in a room of otherwise blind people, but it is on top and outsells a surprising number of makes/models.

      • 0 avatar
        Athos Nobile

        Toadster…

        Volt = Made in USA = bad

        i3 = Made in Europe = good

        Understand? o te lo explico con dibujitos?

        • 0 avatar
          CJinSD

          The Volt has 46% domestic content, which is far lower than the average Japanese car. Hating it for being American would be silly. Hating it for the numerous subsidies, for having four cramped seats, for weighing over 3,800 lbs, for getting the same gas mileage as an average compact, for its association with the Obama regime, for being a GM product, or for setting back ergonomics 45 years? Why not?

          • 0 avatar
            rnc

            “for its association with the Obama regime”, that would be the Bush regime, tied to the original $15 billion in loans, Obama’s task force wanted GM to dump it for a more realistic toyota/ford hybrid system (that would have meant admitting that all of thier “not built here” attempts had failed). But then again it hasn’t failed, Give it time, allow for improvements in the ICE used, propulsion methods, the batteries, wieght, and as production increases, costs will decrease and what the Bush Regime pushed for may just work out fine (the couple I’ve seen look cool and the people driving them seem quite happy). For a car put together quickly, it was done well, which is a good sign for GM.

          • 0 avatar
            CJinSD

            If you really haven’t been paying attention, google Obama and Chevrolet Volt. You’ll see that there is a strong association, including the emperor bragging about ignoring secret service edicts so he could take one for a drive, saying he’d buy one when he retired, and visiting the production line for photo ops. If he tried to kill the program too, it is just one more illustration of what a fundamentally dishonest narcissist he is.

      • 0 avatar
        Vega

        BMW didn’t use bailout money to build it. They can do what they want with their own capital. People pay over €35,000 for Minis Coopers all the time in more affluent cities in Europe, I don’t see why the i3 shouldn’t successfully tap that market…

      • 0 avatar
        Vega

        Maybe the i3 is not mainly geared towards the US market? Not everything revolves around North America.
        I live in Frankfurt and see high-content Minis all the time. People are paying €35k+ for compact status symbols around here…

  • avatar
    Scott_314

    So BMW says they’re developing an electric vehicle with an optional range extender, and you use this announcement to take a shot at all electric vehicles and their owners?

    Quote: “As much as pure EV enthusiasts may scoff at the idea of any carbon-emitting technology sullying the zero-emissions dream…”

    Derek, you’re better than this, and so is TTAC. The idea has merit, but it doesn’t come across in this article. Let me try again for you:

    Given the well-known limitations of electric vehicles, BMW is proposing a smaller, optional range-extender combustion engine for its upcoming i8. From what we can tell, the smaller engine would be under-powered for a vehicle its size, but the idea would be more of a ‘last resort to get to the charging station or home’ role than a full alternative backup such as the ICE in a Volt or Prius.

    • 0 avatar

      Scott, you are taking this too personally.

      • 0 avatar
        Xeranar

        Personal or not you seem to be lumping people who seek better fuel econ with environmentalists. I’m both but I understand as of now the bigger issue is industrial pollution.

        Regardless, the range extender motor is really what we should be doing right now. Pushing to switch to small motorcycle displacement sizes with a electrical generator design. 500cc in the majority of US autos would severely cut emissions and increase econ across the board dramatically.

      • 0 avatar
        Scott_314

        The anti-EV crowd has created a mythical ‘EV enthusiast’. But find one person who believes that EV’s are just as useful in all cases as combustion engines.

        I know that ‘misrepresenting another’s position or assertion’ is almost the definition of politics today, but we can be smarter and evaluate things on their merit.

  • avatar
    wmba

    It just amazes me how all these “solutions” cause everyone to run around in circles chasing some ridiculous idea or another. I know thermodynamics is a difficult subject, so much so that a lot of my mechanical engineering classmates avoided taking Engin 324 Energy Conversion Systems.

    The gist of it all is that you should burn the primary source of fuel where the energy released is going to be used. That means for vehicles, in the engine driving the wheels. Do not go through any conversions you really don’t need. You will just waste energy in the conversion.

    Range extenders are therefore disqualified. You lug around a motor generator set for no reason other than to waste energy on conversions and accelerating the extra mass to speed. Oh sure, you get a bit back with braking energy recovery, maybe 50%. But you are still left with an overweight vehicle which handles ponderously compared to how it could have been.

    The problem is, engines have wildly different efficiencies at different engine speeds, AND different loads. How to minimize that fact of life is the key to getting more miles per gallon. The parallel hybrid offers the basis for the solution.

    If you optimize a hybrid, you end up with a Prius system including the special transmission and a relatively small battery. Nobody else really has it sussed out like Toyota. Ford is in second place. Both use Atkinson cycle engines and only enough battery to power the bigger of its two electric motors to fill in the gap left by the engine when more power is required. The Prius engine is already constrained to operate most of the time at near its best efficiency. Very clever indeed.

    The system is so good that everyone else is flailing about trying to come up with a second best solution. The newest diesel engines are constrained by particulate emission standards and resultant filters, to lower efficiency than they could show. I predict ultimate disappointment with the new Mazda and GM diesels – one only has to read the internet to see what happens with these lash-up DPF systems. They’re good only for highway driving. Subaru and Honda diesels are also badly affected, so no hope there.

    BMW and all the rest of ‘em need to eat crow and buy a license from Toyota, just like Ford who came to an “arrangement”. Then see how good they are at engineering by out Toyota-ing Toyota.

    Avoid plug-in hybrids, even Toyotas, because in general use, they have too big and heavy a battery to be really efficient.

    The next step forward will be to combine the Prius system with the supercapacitors (as per Alex Dykes the graphene ones in time). These capacitors will weigh less than batteries, and allow even more energy storage with no weight penalty. At that point, you can really refine the Atkinson cycle engine to operate at its best minimum consumption for most mechanical energy output, and use the supercaps to fill in gaps for extra energy requirements.

    The supercaps effectively then become part of the virtual transmission that allows an engine operating at maximum efficiency over a limited rpm and load range to couple to a vehicle operating from stop to maximum speed and everywhere in between.

    In my opinion, the rest of this blah, blah, blah is hot air, not much different from publishing every silly idea put out at a late night brainstorming session and expecting hoorays from the assembled multitude – most of whom couldn’t recognize a good idea when it is staring them in the face, apparently.

    We shall see.

    • 0 avatar
      Beerboy12

      The 650cc twin would most likely not weigh enough to make any substantial or even measurable difference to handling or range. Also this solution does not require the hugely complex, heavy mechanical and electronic bits needed to make a true hybrid work.

      • 0 avatar
        Andrew Bell

        +1 @Beerboy12

        It appears in this case the range extender is used as more of a safety net though. The majority of energy will still come from the municipal power plant.

    • 0 avatar
      Scott_314

      Electric vehicles convert about 59–62% of the electrical energy from the grid to power at the wheels—conventional gasoline vehicles only convert about 17–21% of the energy stored in gasoline to power at the wheels.

      http://www.fueleconomy.gov/feg/evtech.shtml#end-notes

  • avatar
    DC Bruce

    Interesting concept. I have seen gas turbine engines come in tiny size (small enough to be attached to person in a jet pack). While turbines are not efficient at part load, it seems like a small turbine could be developed for this application and if operated intermittently, but at optimum load for efficiency, might be small and light. Of course, it would have to burn kerosene . . . which would be a problem.

    I think methanol — which can be made pretty easily out of wood — was rejected as an alternative fuel because it is super-toxic.

    • 0 avatar
      Brian P

      A turbine of the scale required will not touch the efficiency of a spark ignition piston engine, nevermind that of a diesel. There is a nasty little fluid dynamics principle called the “Reynolds number” that gets in the way of a low-powered turbine ever being as efficient as a large one. And that’s on top of other thermodynamic limitations. In a turbine engine on the scale of utility power generation, you can use 2 or 3 or 4 stages of intercooling and regeneration – necessary for the Brayton cycle to have decent thermal efficiency. On something the scale of an automotive power plant, that’s not going to happen.

      If the power plant only has one operating point, then it might have 100% duty cycle with the vehicle operating at top speed, but in city driving it might have 1% duty cycle … and then the theoretical efficiency will be thrown away because the engine will always be warming up while it is running and losing heat when it isn’t (most of the time).

  • avatar
    tbone33

    I’ve long liked the small gas-engine generator operating at maximum efficiency idea.

    If a compact 650cc engine is used (think of the super-compact and efficient engine in the Ninja 650) and you were to give the 45 MPG vehicle a 6 gallon rather than 12 gallon tank, wouldn’t the hybrid drive system be just as compact as the pure gasoline equivalent? Yes, this assumes the electric 160 hp engine is equal in size to a gas 160 hp engine, and the rest of the hybrid drive system isn’t bulky.

  • avatar
    daniel g.

    Hi everybody, it´s my first time writhing. A couple of ideas:
    Think outside of the box, use a 650cc engine for the bike, es litle, is bóxer, can be refrigerated by air or liquid, is bulletproof, is made in china (lifan factory make the engine for BMW) and is a sign of BMW, nobody use this like them. Your people now this engine, don´t need engineers to manteinance. Spare parts is available,plus maybe can sale the electric bike or gs 650 in the middle no? What is the cost of the entire bike? US$ 8000 maybe, the engine 50%?
    Adjust the engine to the optimum rpm to make the work for recharge the batteries, they work a constant regimen, put a tank capacity of the bike, use the same exhaust catalized. What more do you need? How many weigth?80 kg maybe? Need invent / test something new?
    Or the other extreme: talk with Toyota, what favor need to collect from mazda? I reed a few month ago that the rotary engine can be use with hidrogen (is the other line of work of BMW) the only problem is recharge hidrogen, now, it´s to dificult sale litle fuel cell no more big like a can of oil in any gas station? Again, use a rotary engine with gasoline to an specific rpm to make more fuel/emission eficcient. Again, weigth 100kg???less???
    http://www.thetruthaboutcars.com/2012/08/mazda-boss-reveals-more-about-rotary-range-extender/
    BMW can make the next step, pay royalties, save the rotary and we are happy people!!!
    You don´t need the trasmission or other peripherical devices, only a generator. Can use other technology (rotary engine) or your technology (bóxer engine from bikes, they makes before WWII, something they learn from the years no?)

  • avatar
    Beerboy12

    That 650 motor should be very light. Quite a bit less than a passenger in your car. If your car goes from 40mpg to 25mpg just because you take a passenger with you, you have a serious problem. Batteries are heavy though but with a small, light motor to keep it topped up, the battery can be smaller and therefor lighter.

  • avatar
    Brian P

    This is a general reply to many of the proponents of series hybrids (“small engine running at a constant power” and similar variations of wording). IT DOESN’T WORK. There are too many conversion losses because the power output of the engine almost never matches the demand at the wheels, so now you are going engine -> alternator -> rectifier -> battery in -> battery out -> inverter -> motor => gearbox, and there is a loss at every single step. It very quickly becomes better to let the engine vary its output, even at the cost of a few points of efficiency, and drive the wheels through a gear-to-gear transmission, and only use the hybrid system for certain operating points where it makes sense to do so.

    There is a good reason why a Prius (non-plug-in) is designed the way it is, as a previous poster already explained. That is a very well optimized powertrain.

    I despise driving them, but that’s more the fault of Toyota steering and suspension calibration than anything to do with the hybrid powertrain itself.

    • 0 avatar
      Andrew Bell

      The Prius does have a very well optimized hybrid powertrain. No debate there.

      The point of the engine in this vehicle however is as a range extender for longer trips. The concept of a range extender is that it doesn’t try to match the power output at the wheels. It steadily converts fuel into electricity in order to slow/stop/reverse the drain on the battery once the battery charge drops below a specified point. If it is the sole means of charging the battery pack then it’s probably not a great solution. In this car, it appears the range extender is more of a safety net for longer trips.

      To reduce conversion losses further, you can eliminate the internal combustion engine/generator entirely and use a fuel cell with built in reformer. Then you can convert chemical energy (liquid fuel) directly into DC electricity at much higher efficiency. Your only losses on the input side in this case are through a DC/DC converter.

      Serenergy has developed some very efficient fuel cell systems for this purpose. Methanol is converted into hydrogen (on demand, no storage issues) and is consumed in the HTPEM (CO tolerant) fuel cell at approximately 50% liquid fuel input to DC electricity output efficiency (theoretical maximum efficiency of approximately 68% through clever, and proprietary, re-use of waste heat).

      The use of methanol as a fuel is a separate issue but it does have some excellent qualities for use in fuel cell/reformer systems. It also should be noted that China is charging full steam ahead on using it as a transport fuel.

      Short answer -> The series hybrid is not even close to dead.

      • 0 avatar
        Dr. Kenneth Noisewater

        There’s also solid-oxide fuel cells that IIRC operate on hydrocarbons directly rather than reforming them, though apparently their operating temps are still rather high.

        (old-ish article: http://www.fuelcelltoday.com/news-events/news-archive/2011/december/gasoline-sofc-under-development-for-automotive-applications )

    • 0 avatar
      Brett Woods

      @ Brian P. Agree with your logic except that motor is DC so no inverter needed, and no gearbox needed because full torque @ 0 RPM. Also electric motor is (80% efficient?) So good to make the power, while ICE is 20% efficient…so if you kept that ratio….

      You would have to show the Math to convince me it doesn’t work.

    • 0 avatar
      Herm

      “IT DOESN’T WORK”

      Brian, this is a misconception that has been around since the Volt was proposed.. why is it not true?… because conventional ICE drivetrains are not 100% perfect either. Think about it.

      Another example, the Volt can choose to operate as a pure serial hybrid or as a more traditional parallel hybrid.. in some cases GM engineers use the serial mode* because its MORE efficient (they choose parallel at speeds higher than 70mph I think).

      *with all those conversion losses

  • avatar
    BryanC

    I’m a little disappointed this article doesn’t even mention the Volt, leaving the impression that BMW is pioneering a new solution to the range anxiety problem. =(

    The article also avoids mentioning that this car will have severely restricted power output when the range extender is running. You won’t be able to drive at freeway speeds if there’s a hint of a hill, and merging onto a freeway will be as slow as if the car were powered by a 0.5 L engine. Hardly the ultimate driving experience. BMW’s range extender is mostly a limp home mode, I can’t imagine actually using it much. BMW doesn’t seem to think much of it either – from what I have read, they expect most people to forgo the optional extender…

    • 0 avatar
      Scott_314

      Agreed – this idea has some merit but the article basically side-steps it. The issue should be ‘Volt – fully capable range extender’ vs ‘i8 – limp home mode’ but it doesn’t.

      I like the idea. We’re all too busy to deal with the hassle of being stranded, yet the current range of EV’s makes it a constant possibility. Even given a Nissan Leaf’s range of 100 miles and a 25-mile each way trip: add a really hot day and a couple of errands and bad traffic and you forgot to get something and the range keeps dropping, it would be stressful.

      A limp-home mode would be an enormous weight off the shoulders – yes your range is 20 miles and your house is 22 miles away. Should you set the cruise at 45 and hypermile yourself white-knuckle to the end? No, just drive normally and you’ll probably make it, and if you don’t the last bit won’t involve a tow-truck.

      On the other hand, the Volt already has covered the typical commuter range in EV mode, but if you want to drive to the next city, you can. It has enough power to drive like normal all of the time.

    • 0 avatar
      Herm

      Merging will never be an issue since BMW will not let the battery get to zero..

      a 35hp generator (25kW) should be enough to cruise at 75mph on a flat hwy with no headwinds.. you wont sustain that speed going up a hill but the light weight of the BMW should help with that. You will also be limited by the 2 gallon fuel tank.. but this all fine for an OPTIONAL small engine that you will seldom use, note this car will have 80 miles of range just on the battery, if you could recharge at work you would be able to travel 52k miles a year just by plugging in.

  • avatar
    Brett Woods

    I am two thumbs up for the 3 cylinder of i8. The Triumph Speed Triple motorcycle has proven Inline 3 has mojo. Enjoyable sound, nice vibration, good energy output. BMW is trying to make a special driving machine with i8.

    A trailer is only suitable for a one-off like Electric Plymouth Prowler or as a test-bed during development stage. No one could seriously propose that the finished product have an articulated trailer.

    As others here say, for an ordinary car, a scooter engine would be adequate (and light enough) for generator. Is so large as a 650cc twin really needed to create charge?

    • 0 avatar
      Herm

      BMW is not running this engine anywhere near maximum power, I guess they wanted a quieter, more efficient setup. I believe most small gasoline engines hit peak efficiency around 2500 rpm

  • avatar
    shaker

    I applaud this effort – the result being an extended city range EV – it merely makes travel across large metro areas possible with a reduction in “range anxiety”. If purchased with this limitation in mind, it should fit well with many consumers who don’t expect to make long road trips with (what is essentially) a daily commuter vehicle.
    The Volt is a vehicle that can make “American-Sized” road trips, though if it’s used for those exclusively, its efficiency advantage is lost.
    In other words, EV’s are still subject to the present state of battery technology, and this is an attempt to fill another use case that can maximize the efficiency for that scenario.
    Things will only improve when batteries improve, supercapacitors are added to gain even more efficiency (and to moderate the peak charge/discharge rates seen by the battery), and ICE’s (or fuel cells) are integrated into the mix to “fill the gaps”.
    As to “conversion efficiency”, keep in mind that cars like the Prius are always going to rely on carried fuel, and it could be argued that the (admittedly wonderful) Synergy Drive is pushing its theoretical boundaries for efficiency. It’s still “king of the hill” in regards to “gas” mileage, but it still relies on limited regen, and a moderate-performance Atkinson engine to drive the wheels – it’s essentially “locked”.
    An EV can have much better performance (when needed) but can also be switched to a more frugal mode of travel if required.

    And, to turn the argument “on its head”, assuming the possibility of a huge disruption of the fuel supply, I know what I’d rather have in my garage – a vehicle that would allow me to “git-er-done” within limits.

    We could go on about how we should keep gasoline flowing like water, no matter what the cost, but why be slaves to the stuff? Let’s use our best ideas in an attempt to move on.

    • 0 avatar
      mkirk

      In the event of your “huge disruption in fuel supply” I’ll take something that runs on veggie oil. Worst case scenario is that I have to fill up at the grocery store. If the fuel disruption is bad enough that the trucks can’t get to the grocery store than your vehicle isn’t of particular relevance.

      • 0 avatar
        Herm

        Look up the disruption of fat supplies in post WWII Europe and the resulting “fat starvation” or “rabbit starvation” (rabbit meat is very lean).. You can make electricity with just a few solar panels

  • avatar
    tjh8402

    As far as turbines go, the usefulness of a small turbine in an application like this is dependent on BMW’s answer to a question posed by several commenters, namely do they try to maximize efficiency under battery power at the expense of efficiency in range extension (hereafter RE) mode, or vice versa? While a small turbine is not as efficient as a small reciprocating engine (ie to generate a fixed amount of power in a given period of time will require more fuel in the turbine) and therefore not as effective as a RE, it does offer the advantages of being much more compact and much lighter than a reciprocating engine, which would help alleviate many of the concerns raised over the added weight and space required for the RE powerplant and its affect on the vehicles performance in electric mode.

    Turbines also do not require kerosene. Since they essentially are compression ignition engines like diesels, you can run them on a wide variety of fuels including diesel, natural gas, or everyones favorite tree hugger fuel, french fry oil. They are also simpler mechanically, with much better reliability, less required maintenance, and much longer lifespans. This fact, plus the aforementioned advantages in weight and packaging efficiency are why turboprops have replaced large reciprocating engines in aircraft. For example, the Conntinental IO-550 piston engine is supposed to be overhauled after 1700 hours of operation, whereas a Pratt & Whitney PT6A TBO is 3600 hours and many run fine far beyond that.

    I also have a question. Some commenters have noted that it is less efficient to have the gas motor provide power to either the electric motor or its batteries rather than a direct drive to the wheels. If this is the case, then why are diesel electric railway locomotives designed for the former and yet noted for their fantastic efficiency?

    • 0 avatar
      RJM

      I suspect the turbine whine might be hard to muffle. Otherwise, seems an excellent choice.

      Regarding the Diesel-Electrics locomotives – the difficulty of clutching and gearing the starting torque is the reason for using their hybrid system. Some of the smaller switch engines moving only a few cars at a time do have power train very similar to semi-trucks (it was weird to hear the one in my home town shifting gears as it brought 2 cars at a time to the cannery loading dock). Efficiency arises from low frontal area compared to the load, low resistance of steel wheels on steel tracks, and ability load 10 times as much coal into one hopper car than on one high-way legal truck. Also, no stopping for traffic lights and re-starting.

  • avatar
    corntrollio

    As if on cue, I saw a BMW 1-Series ActiveE parked on the street yesterday.

    I didn’t know much about the car, but apparently it’s a spin-off of the Mini E project. The car has liquid heating and liquid cooling for the batteries, which apparently is a result of the cold weather testing they did with the Mini E, re: range-anxiety. I wonder how this compares to Tesla’s experience.

  • avatar
    mkirk

    So does dropping a Harley V Twin in one of these now become the equivalent of dropping a 350 in a Jag?

    Also, is this a clean sheet motor or is it based off one of their bikes? The BMW 650 motorcycle engine is a single. I think the 850 is a twin and both are built by Rotax if I am not mistaken.

    Also, all of the “put the motor on a trailer” crowd need to drive around with a trailer. There are some simple logistics in play here…simply parking and backing up for example. Most posters here I’m sure have no issue backing up with a small trailer, but most drivers aren’t posters here.

  • avatar
    RJM

    A few years ago, a man hacked off the back half of a 1978 Volkswagen Rabbit, powered by a 52 horsepower diesel engine. It has a stock three-speed automatic transmission, axles, and CV joints, all connected to the front wheels as a front-wheel-drive vehicle. He attached a trailer tongue to it, and used it as a trailer that is towed behind the EV, (a converted 1981 Rabbit) just like an ordinary utility trailer.
    The emissions testing etc had already been done by VW. Probably not something one would want to drive on a snow-covered road with lots of turns, but for freeway touring in reasonable conditions, it worked well.
    http://www.mrsharkey.com/pusher.htm


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