How Much Of A Battery Pack Does Your Electric Car Need?

[Elon Musk] recently staged one of his characteristic high-profile product launches, at which he unveiled a new Tesla electric semi-truck. It was long on promise and short on battery pack weight figures, so of course [Real Engineering] smelled a rat. His video investigating the issue is below the break, but it’s not the link that caught our eye for this article. As part of the investigation he also created an online calculator to estimate the battery size required for a given performance on any electric vehicle.

It’s not perfectly intuitive, for example it uses SI units rather than real-world ones so for comparison with usual automotive figures a little mental conversion is needed from kilometres and hours to metres and seconds if you’re a metric user, and miles if you use Imperial-derived units. But still it’s a fascinating tool to play with if you have an interest in designing electric cars or conversions, as you can tweak the figures for your chosen vehicle indefinitely to find the bad news for your battery pack cost.

It’s very interesting from a technical standpoint to see a credible attempt at an electric truck, and we hope that the existing truck manufacturers will show us more realistic prototypes of their own. But we can’t help thinking that the overall efficiency of electric long-distance trucking could be improved hugely were they to make a truck capable of hauling more than one trailer at once. Any safety issues could be offset by giving these super-trucks their own highways, and with such dedicated infrastructure the power could be supplied from roadside cables rather than heavy batteries. In such circumstances these long trains of electrically hauled containers could be rather successful, perhaps we might call them railroads.

Sadly nobody has yet produced a semi-truck conversion to grace these pages. The closest we’ve probably come is a pickup-truck.

143 thoughts on “How Much Of A Battery Pack Does Your Electric Car Need?

    1. I agree but there are two factors:
      1. How many countries actually got a good railway system, which is electrified (looking at emissions).
      2. You cannot drop my packages to my house from the train as I live 5 miles away from it.

      In reality what needs to happen is: Improve on upon the track system and then get electric lorries (trucks for the Americans), to deliver it around the city. Europe is perfect for that test, where you have high density of populace in some cities.

        1. Yup.

          Sure, building good railroad tracks is expensive. But once you have the right of way, the ongoing maintenance cost is a fraction of the maintenance costs of highways.

          Trouble is, trucking is “free”; the trucking industry does not shoulder the entire cost of using highways to haul goods. There is an argument to be made that trackage should belong to the public and the railroads lease them.

          1. “Trouble is, trucking is “free” – maybe in the US.
            All EU states have some form of road tax, heavy freight naturally pays more. Also, the fuel is FAR more expensive, most of the difference between US and Europe is the tax, which is “supposed to” go towards maintaining the infrastructure.

        2. Germany pretty much shut down all their nuke plants and built several new coal-fired ones (not to mention the unstable nature of “renewable” sources, needing even more coal and gas fired plants), so electric trains in Germany aren’t as green as you might think.
          Most of ex-Soviet block states have the railway system poorly maintained and well past the days of it’s formal glory, road-bound freight is simply more flexible and newly built factories have rarely rails leading to them, because it’s expensive.
          That being coupled with the fact that there is no one standard on electric power for trains in EU (past the Ukrainian border even rail spacing is different), even in one state there’s usually 2 or 3 incompatible systems, generally several kV DC and around 20kV AC, as each has it’s pros and cons and also backwards compatibility issues.

          1. They had a item linked on Reddit a while back that during a windstorm the German wind farms produced more electricity than the entire country needed.

            Also I think your story about the Russian railroads is BS.

            Also there is an international standard for railroad spacing which currently the Chinese in particular are helping along with international railroad projects

            But sure, preach the whitehouse or CNN message, it’s the American way.

          2. This isn’t from CNN: A Russian friend of mine went back to visit recently, and when she came back she said it was very difficult to get around because none of the trains ran on time. Why? Because the trains were electric, and people would randomly go out and tear down trolley wires in the night to sell the copper for scrap.

          3. >”They had a item linked on Reddit a while back that during a windstorm the German wind farms produced more electricity than the entire country needed.”

            And that is exactly the problem, because for the vast majority of time, they don’t.

            Wind power has the property of producing 50% of the energy in 15% of the running time, due to the distribution of wind speeds over time. You get a lot of these “blips” of power that you can’t put anywhere because they exceed your grid capacity, while on average the turbines produce well below your grid demand.

          4. There are ways to store energy.

            My Grandfather donated some of the family farm property to be built into a nuclear energy (when price was low) pumped lake water storage facility to be later drained (when price was high) through a hydroelectric damn system that was never implemented due to if I understand correctly… fish being sucked into the other one in Ludington/Pentwater which adversely impacted the fishery industry.

            The system not being implemented actually angers me to this day because I believe this type of system can be implemented and improved upon with natural resources developed on top of and inside even. Basically, you can seal the system better to avoid leakage with more wildlife or farming in the perimeter if not development more domesticated.

            Let’s just say the community wants the area natural… then develop based on the geological assessment so all and larger volumes of what was existing as found is as left once the underground and what structure is needed above ground is implemented.

            Really dangerous people in my opinion deny facts of the matter when there are feasible man made structures that can literally clean up the existing natural resources situation to be more productive. Most naturalists seem to deny how much wild was planted at one time from Europe or elsewhere.

            Remediation and development would especially serve humanity if there were banned biocides (found in empty piles of trash dumped by unknowns) or cattle feed that was fire retardent used on the property which I am not aware of though have read bio-terrorism attacks may have taken place more in the U.S. than most realize.

            I speculate this may have caused issues with the family generations back then not being as productive/reproductive if not otherwise due to mafia related hostile take over issues that were more war crimes forensically clean operations by what looked official moving into the positions of the original U.S. Jurisdiction that didn’t disrespect or taint like Roman hoards or irregulars do.

          5. @dax

            Yeah and solar is only during the day, and tides is only when the sea is present and dams only work during the few hundred years a river runs, so let’s just fire up that coal and make everything glow with radiation, because radiation glows for free after all.

          6. Technically if solar thermal like a solar concentrating trough or maybe dish design using a heat exchange fluid not like a external combustion engine fluid but transfer and storage media… the energy can be stored in super insulated underground or sealed facilities with materials that are in a closed or open loop that can store the energy with advantages of phase change exothermic release later.

            I’ve never seen this before published… though wondered… why can’t we use a lithium salt or at least sodium acetate like hand warmers to store the energy and later release versus molten salts or metals methods.

            I even think water can be pumped back and forth also to store and later take advantage of gravity.

  1. I’ve never quiet worked out why large trucks exist for goods transportation. Apart from satisfying militant union mobs.

    There will always be special cases where the rail doesn’t suit but from what I see here in the part of Australia I live in most of the trucks on the highway go from one distribution center to another.

    Trucks should only be needed for short runs from regional distribution center to the consumers home which is the ideal situation for electric vehicles.

    1. Rail is only good if you have a large, monolithic load like coal, gravel and such, and you’re trying to send it over a long distance. And you can plan the transport in advance, sometimes months ahead. It works wonderfully when you want to transport several thousand tonnes of coal to a power plant on a regular basis. Not so much for small loads coming from a large number of suppliers, like consumer goods usually do.

      1. Load a truck on a train at one distribution hub near the starting point, unload it ad distribution hub near destination point. This combines cheapness and safety of trains with versatility of trucks…

        1. While in theory this sounds good there is a massive problem, frequently in the uk, locomotives are moved by road! Yes road,railway locos on semi trailers by road.
          When restoring the bluebell railway most of the imberhorn cutting land fill was taken away by trucks, because it was cheaper, a lot cheaper.

          1. I mean, that’s at least in part going to be because until the Imberhorne Cutting was cleared and track laid through it, there /was/ no rail link to use instead. It’ll probably also be because British freight rail isn’t great at small occasional shipments from private shippers, I guess – it’s somewhat more set up for intermodal and bulk loads these days.

        2. You can’t tell me with containerized shipping and a decent computer algorithm we couldn’t dramatically improve rail shipping times?? I think the current slowdown in USA train systems is that we don’t have a way to quickly shuffle which cars/containers are on which trains. There are few things with a little foresight can’t be delivered in a timely way on a much cheaper transport method. I see some variant of rail as the future for moving goods. What UPS/FedEx is doing with airplanes and massive distribution centers could be emulated in some form by rail making transport cheap, and fast(er).

          1. S. Blake: what century are you calling from? Have you looked at freight trains lately? Most cars are either built for specific cargo, or are inermodal. And do you think freight car routing is NOT being optimized by computers? It certainly is, and there are automated railyards that can reshuffle trains with little human intervention.

      2. Rail also has a problem with floods. A washed out track can’t be used until repaired. “Road trains” however, can go through flood water (within reason) and use unsealed dirt tracks.
        In some areas of outback Western Australia, that dirt track is all there is. If the cost of sealing the road can’t be justified, do you really see someone installing a railway line?

  2. “It’s not perfectly intuitive, for example it uses SI units rather than real-world ones so for comparison with usual automotive figures a little mental conversion is needed from kilometres and hours to metres and seconds if you’re a metric user, and miles if you use Imperial-derived units. ”

    *wink*wink*nudge*nudge* Merry Christmas, Jenny.

    1. I’ll take the clock-bait: SI *is* intuitive for 95% of the planet of course! Unfortunately, for a US article it’s the 95% of the planet that barely exists ;-)

      But, oh what an unintuitive nightmare they are, having to multiply and divide by powers of 10 all the time when you could be using a random assortment of base 12/16/8 whilst conjuring up those “British” horse powers; foot pounds per square inch or other ‘real-world’ hilarities ;-)

      1. I have to admit to thinking about distances and car-related stuff in miles or miles per hour. But that’s not the point, even if you use kilometers an hour you’ve got to convert that to get to meters per second which the calculator requires. It’s not a dig at miles vs kilometers, it’s hours vs seconds.

        1. It’s an easy factor to remember because it crops up everywhere: 3.6 kph per m/s

          And it pays to remember couple basic approximations. It’s 1-2-3 x 10
          Walking speed is 1 m/s, jogging is 2 m/s, running is 3 m/s.
          Cars go 10x faster:
          10 m/s is 36kph/22mph,
          20 m/s is around 70kph/45mph
          30 m/s is 108kph/68mph
          Those are close enough to common speed limits for the purpose of calculating the physics. In fact, it might be useful to have speed limits in meters per second – at least you’d become more aware of your braking distance.

        1. Yes we certainly do still use miles, we buy our fuel in litres but think in MPG doing the conversion in our heads.
          “US article. Written by a British author” with that in mind along wth someone elses “no country is fully metric” statment, do Americans still have imperial threads or have you converted to metric or, like us, are you mesing around with a few different imperial standards and metric all at the same tme.

    2. Most of the commenters here missed the point: the speeds for trucks going down a highway are expressed in meters/second in the OP — units that aren’t on any speed-limit sign in any country I’ve ever been to.

      It’s not a metric/imperial thing.

      1. Elliot: it kind of is: NO country that I know of is fully metric. None of them have metrified time, which is arguably the most important unit of measure there is. And there’s a reason for that: the second, which is the SI unit of time, is not a decimal subdivision of a day, nor of any other useful reference. Nobody cares how many wavelengths of what kind of light it is; a second is roughly equal to a heartbeat, but there are 86,400 seconds or so in a day, which doesn’t divide very well in decimal. If the second had been redefined when the other SI units were defined or redefined, to be 1/100,000 of a day, a second would still be roughly equal to a heartbeat, and there would be 100 subdivisions of a day, let’s call them “Huygens” after Christian Huygen, each of a thousand seconds, and then it would be easy to convert m/sec to km/Huygen, because they would be the same. But they didn’t, so we don’t, so they aren’t, and this leaves a whole bunch of measurements that involve time to be as awkward as all of the old systems of measurement. So there. Nobody is metric.

        1. There was a very good reason why the second was originally defined as it was, because the first proposals to standardize a metre were based on the seconds pendulum, with a half-period – one swing past the center and back – of one second. Handy for clockmakers, cartographers and physicists all around because they could produce their own metre to a reasonable accuracy without referring to a central authority.

          This is still accurate to 99.4 cm under standard gravity, if you ever need to produce a string of one metre, or in case you’re building a grandfather clock.

          1. The root of the problem is that the day is the one measurement that you can’t fudge, because cumulative error will mess up your day. And the problem with the Earth slowing down will just end up with leap seconds being added more and more frequently, until it becomes a problem. But by the time that happens, we’re either extinct or space-faring, so the time problem will need a more er.. universal solution.

          2. The point was; why the day wasn’t split into decimal time – although the French did try – is because it didn’t mesh up with the other definitions of the metre or have any other practical purpose as it would have resulted in the re-definition of all the derived units.

            A seconds pendulum works to within 1% of the correct answer (depending on local gravity/latitude) as long as the second is defined as 1/86400 part of the mean astronomical day, and the measurement can be refined easily where the local conditions are known.

            The English proposed the seconds pendulum as the definition of the metre because it would be a natural standard measurable by anyone. The French wanted it to be defined by the meridian through Paris, then made into a iridium-platinum prototype, because then everyone would have to go to the French to check their metre.

          3. Maybe that WAS the point, bu what IS the point is that it was deemed too inconvenient for the whole world to convert to metric time, so we continue to have difficult conversions, even in SI units, because of this.

          4. There will always be difficult conversions, because nature doesn’t care about being neat.

            Consider for example, if you change the second, you change the Coulomb, and therefore your definiton of a Volt and Ampere would change. Then, the standard Zn-Cu voltage pile would no longer produce 1.0934 Volts of potential and you’d have kicked the problem down the road.

            So it’s simply a matter of choice where you want the inconvenient conversion factor to be. It’s better that it exists in a more fundamental quantity rather than propagating down the line to a myriad of derived units.

    1. Yeah, any long distance truck in Australia will be a prime mover pulling at least 2, probably 3 trailers. They’re experimenting with a move to 4 trailers for some routes/loads.
      (Source: Co-founder on a side project works for Toll.)

  3. Whatever happened to the battery swap stations that were faster than a fill up?

    Tesla uses 70kWh batteries for the model S.
    The efficiencies aren’t identical, but 70kWh is what you get from 1.72 gallons of diesel fuel. Or put differently, one of those 5 gallon refill tanks of diesel contains the same energy as three Tesla batteries.
    I’m not sure if I would room left when replacing my Pickup’s diesel tank with 22 Tesla batteries.

    Also note that the initial version is not a city, start-stop application, but a long-haul railroad like application (also see self-driving trucks that need tens of thousands in technology that railroads don’t need).

      1. I have been reading around, but never found any EV drive train even close to 95% efficient.
        As a high efficiency motor is already at 98%, that isn’t taking into consideration things like reduction gears that are typically in the area of 80-95% in themselves. Then there were switching losses in drive circuitry, battery discharge losses (primarily heat) and resistiv losses in cables.

        If all of that comes out above 80% efficient in the end, then you have a really efficient electric vehicle.

        1. I’d expect the major loss in a modern electric drive to be the tires. They require friction with the road surface to work, and they have to constantly distort and flex to do their part for providing a comfortable ride.

          1. No. Rolling resistance is in the 3% range. Think about it, if most of the vehicles energy was being put into the tires as heat they’d get incredibly hot. Hotter than rubber could take very quickly.

          2. I_failed_Cpp: According to the U.S. Department of Energy, “It is estimated that 3%-11% of light-duty fuel consumption for conventional and hybrid electric vehicles is used to overcome rolling resistance.” (https://www.afdc.energy.gov/conserve/fuel_economy_tires_light.html.) So saying “in the 3% range” is being a little optimistic. Your assertion that if it was higher, tires wouldn’t be able to take the heat, ignores the fact that tires are air-cooled. And really, they just barely tolerate the heat as it is – most blowouts are due to insufficient inflation pressure, which causes higher rolling resistance, which causes overheating, which causes kaboom!

          3. You are correct. In a semi truck, because the weight is high, the rolling resistance becomes significant. This is doubly true for Tesla, as they’ve already made large strides in reducing drag which is normally the majority of the energy consumption.

            I’ve heard rumors that the Tesla Semi is supposed to be using super-single tires, which are lighter weight and have lower rolling resistance, I’ve seen as good as 0.004 or 0.0035, much better than the 0.0063 the article assumes. Tesla can significantly increase their profit margin by maximizing the efficiency of the tires.

            I’ve noticed a lot of articles making “conservative” assumptions like using tires that aren’t as efficient or assuming greater inefficiencies here or there… that’s not logical. Tesla has every incentive to wring every efficiency they can, as it reduces the cost and weight of the battery (which make up half the vehicle’s cost and weight) AND reduces the cost of the charging infrastructure needed for these beasts.

          4. Building a tire with reduced rolling resistance is easy. Just look at the front tires on a top fuel dragster, small and skinny. Building a tire that produces adequate grip is a whole other issue and contradicts reduced rolling resistance. Look at the rear tires on a top fuel dragster. Those are the tire that must produce grip and they are large and they flex and distort tremendously under the load they must handle. Watch a video of a top fuel dragster in slow motion and you’ll see this. It’s not just about providing a comfortable ride. As long as you are traveling in a straight line, on level ground, an don’t have to accelerate or decelerate, you could get away with tires that have greatly reduced rolling resistance, but as soon as you have to deviate from that you need grip and that means your going to need tires with more grip and thus increased rolling resistance or else you’re going to lose control of your vehicle.

          5. >”Tesla has every incentive to wring every efficiency they can, as it reduces the cost and weight of the battery ”

            Yes, but that does not translate to real world savings, as low rolling resistance tires are a compromize of other properties like traction, cost, noise and wear. You can almost view the issue of the tires as cheating the test, because the real customer won’t necessarily use them for various reasons. Most likely reason being cost, so from the owner’s perspective, it’s picking the least of two evils – either pay too much for the batteries, or pay too much for the tires.

            That’s always been a problem with electric cars, because they can be optimized extensively, and they are optimized especially as it comes to passing some arbitrary performance metric they can put on the sales brochure. They even pick the arbitrary performance metrics to make it more appealing, such as Tesla choosing to report the range of their cars at 55 mph instead of 65 mph – because it gives them about 25% “extra” miles for free.

            For another example, air resistance drops by 10% when you go from -5C to +25 C so by testing in sunny California, instead of New York or, say, Norway, they get to post more sunny figures. It’s cheating all around, because every %-point counts.

          6. Totally!!! Loved the excellent efficiency of the Prius in Tuscon… was getting almost 60 miles per gallon regularly when really careful driving. Now in Michigan with the 12 degree F weather this morning… I’m sure I am consistently around 47 or less miles per gallon.

            I’ve been wondered if having adjustable shingles that can close for the radiator grill and pre-heating the air intake will help with efficiency in colder climates. Even a heavier duty lower drag skid/bottom plate wouldn’t be bad that maybe is insulated.

            This post makes we want to look into rear wheel fairings, smaller rear mirrors (prefer a bullet style with cameras and dash mount LCD’s/OLED’s to display and a rear cargo container even lower drag tail. The first two designs and really an improved bumper were out on the market in Japan along with a camper. Maybe taking the hatch off and having more a solid elongated tail mounted with the hatch bolts and profile would be better too.

          7. Stefan:
            Super single tires actually ALSO have good grip because they have more rubber in contact with the road. Not everything in engineering is a pure trade-off. There are genuine improvements.

          1. Direct drive increases the amount of unsprung mass at the wheels, which makes the ride worse and the chassis needs to be built tougher. The in-wheel motors and their electrical connections are also more subject to dirt and water.

            Besides, a slow running direct drive electric motor at the wheel is less efficient because it produces torque via high magnetic flux, meaning high currents and high RI^2 losses in the coils, or alternatively, more turns at the coils which then perform poorly at high frequencies (speeds)… etc. bad compromizes.

            While electric motors can be driven by VFD from zero to beyond their design speed quite easily, this is not an optimal way for efficiency or mechanical construction. It’s a cheap way to do it, though. Tesla originally tried to have a two-speed gearbox in the Roadster to improve the mileage, but they didn’t have the competence to make it work.

        2. Because the truck is being sold by range and not by just battery capacity, and because about half the cost (and weight) of the vehicle is in the battery, there’s an enormous incentive to improve efficiency everywhere. Going from 80% to 90% (or even 95%) efficiency means they can use a battery that’s 10% smaller while also increasing the payload and thus increasing their margin on the vehicle by 5%. This is not the case for passenger vehicles where the battery is not as big of a proportion of the cost and weight of the vehicle.

          There’s a VERY strong incentive for Tesla to seek high efficiency drive circuitry (99% is feasible), and the fact they’re using a huge battery means the resistive losses in the battery are much lower than they would be for a smaller battery vehicle. 95% is possible for electric drivetrain.

      2. In this particular case issue is not about ICE efficiency, although it is terrible as it stands, it is about that ICE directly drives the drive train of the car, and for that it needs to be big. Big ICE requires, now with its inefficiency, requires a lot of cooling, and consequently a lot of thermal loss in the air. The the thermal waste gets handy thought in cold temperature, and so it is not coincidence that the people who understand the problem term the cars ( with ICE ), “moving stoves”.
        With EV, the best option would be to have a small liquid fuel generator, highly optimized for electric generation in the car, so that will extend immediately the battery range by and provide the so needed heating in sub freezing temperatures. In the summer the waste heat from the generator can be rerouted to mini (likely blameless, Nikola Tesla type, for increasing longevity of the system) turbine ( better to be a self contained ) system driving another mini electric generators that can be added to the car system on the needed bases.
        That modular design solves all the big issues with the EV market as increasing the range and making it highly useful in cold regions of the world as well. Of course such a solutions easily comes to mind, as long as we realize that it is not ICE efficiency issue that we have, but issue with not utilizing the thermal energy ICE creates, witch is 2-3x more (depending on design and so on) then the energy available for the drive train.

        The beauty of this line of thought is that the technology parts are all available we only need to optimize on the existing technologies and look at the problem as one for optimization instead of creating a new paradigm, by creating even more inefficiencies in some way.

    1. The battery is very expensive. (not to mention heavy, so changing it would also be expensive)
      Fancy car wheels are also expensive and relatively easy to remove, same for catalytic converters and or some radios/infotainment systems. Guess what parts get stolen the most…

      Would you want a car which has a part, that is responsible for over half it’s total cost, can be easily removed and will be very high in demand? Even if they wouldn’t be able to use it as a whole because of some BMS lockout, they could still rip out the individual cells and sell those.

      Bad idea.

  4. “for example it uses SI units rather than real-world ones”

    I prefer SI units a lot over re… “american”-units… maybe you should get used to them when authoring tech articles for an international audience…

    1. I think what they mean is that the measurements were in meters per second instead of kilometers per hour, or in the same order of magnitude as feet per second versus miles per hour. Not something you’d find marked on your speedometer dial, regardless of whether you were looking at the metric or hamburger part of the scale. In that sense, “real world” vs academic measurements applies to both standards.

      Also why don’t we have base-10 time measurement yet? Well I guess decimal time is a thing, but nobody uses it. That would make the conversion a lot more straightforward.

      Okay, I now resolve to quit contributing to the measurement system debate. I apologize to the HAD mods.

  5. The British govt have a plan, a few years ago diesel cars were the cleanest thing ever, in fact they left a trail of wild flowers wherever they went, so British people bought diesl cars, loads of them.
    Then a sciency type boffin did some maths, it went like this, oil is going to run out, battery cars are ok. battery trucks,diggers,tractors and everything else are not now and never will be ok, we can grow diesel, but not if we have this many diesel cars.
    So now diesel cars are the dirtiest thing known to man, except maybe pornhub, bit at least thats environmentaly friendly, being mostly electric.
    As an aid to those that dont know, 38tonne trucks carry roughly 24tonnes trucks that pick up from a rail head are allowed to weigh 44 tonnes, 27 .6 tonnes of cargo plus the container at 3.750 tonnes.
    An engine,gearbox and full tank of fuel weigh roughly 2 tonnes, the question is can you propel 42 tonnes around for 8 hours at 56 mph with a battery that weighs 1.5 tonnes?
    I’m assuming the electric moter and controller weigh 500 kgs.
    Sorry it’s all metric, but if you’re capable of solving the actual problem you’re more than capable of doing some faily badic maths.

  6. Ahem…”It’s not perfectly intuitive, for example it uses SI units rather than real-world ones”
    By “real world” do you mean “olympic size swimming pools”, “football pitches”, “human hairs”, and “double decker buses”?

    I’m waiting for the media to describe HMS Queen Elizabeth’s displacement not in tons but in “olympic size swimming pools”.

  7. Fake news.
    Battery calculated to be 8000 Kg, with current technology, not taking into account the ~11% projected energy density increase by the time the thing comes to market.
    Semi WITHOUT engine – 7000 Kg
    Conveniently forgot to mention that a semi engine has a mass of about 1300 kg
    Doesn’t need a transmission either, another 300 kg
    Doesn’t need a fuel tank, 400 to 600 kg
    All the cooling shit you need for an ICE we’ll just ignore for the sake of argument.
    Actual increase in mass – 5000 Kg give or take.
    How many times are semi trucks filled to mass capacity compared to volume capacity? Rarely. An electric Semi can carry 15% less mass? So? I’m not saying it doesn’t happen enough that being able to haul more mass is a pro, but it’s not THAT much of a pro, especially 15%.
    Not to mention it’s being designed from the ground up as an EV so it would be pretty easy to save mass in the design.
    I admit i’m a tesla fanboy and everything, so i’m a little biassed, but this article takes the mick.

    1. If a freight shipping company wants to stay in profit they’ll be using a system that arranges to have the trucks loaded by destination so that as often as possible they leave a depot or hub full or nearly full. For places with lower amounts of freight going in or out they’ll use shorter trailers. UPS and FedEX aren’t running those dual and triple trailer rigs half empty.

        1. By weight Bill, not sure on the US but in europe the loads are planned and rearranged on loading order so the weight over each axle is correct and as close to max loading as legally permitted. Its also common to be pulled over and weighed per axle on a weighbridge as running overloaded is a flybynight way to increase profits, a big cause of accidents when things break and big fines if caught.

    2. Because Tesla semi weight is currently not disclosed, we get get “facts” based on totally made up energy density and production cost of the Tesla semi battery, and a totally made up weight of the Tesla semi without battery.

      More interesting, is the 36.000kg limit with an empty fuel tank? In that case it would be fair to not include the battery content in an electric truck, or allow electric trucks some additional weight, similar to the diesel in the largest diesel tanks.

        1. It look like there is an extra 181 kg allowance if the truck is fitted with a system that reduces pollution when the main engine would be running idle. I think an electric truck would qualify for this.

        1. It only means what it means. It may be possible for it to carry the same weight, but if that makes it legally overweight, that’s not Tesla’s problem. Don’t read into it what isn’t there.

    3. I agree, it would still be great if all the semis carrying toilet paper and dog food and other not-so-dense stuff became electric. Sure, we’d still need diesel for trucks stacked to the brim with ingots of pig-iron, but this is still a big improvement.

  8. I dislike the “weight represented as volume (or area) on the figure as well.

    The only situation I encountered when a semi was weight-limited, rather than volume-limited, was when I’d order a few dozen lead-acid batteries for forklifts, amusingly.

  9. Probably the best avenue at this time… is to use diesel-electric technology.

    An engine is most efficient when run at its optimal speed: use that to turn an alternator to keep batteries topped up, then use that to power electric motors. Then, when more power is needed, it can discharge the battery. When decelerating, regenerative braking can be used. The diesel engine the whole time just runs fast enough to cover the “base load”, running at more-or-less constant RPM where it is most efficient.

    Diesels aren’t the only option either… the gas turbines that were popular in some experimental 1950s cars would do well in this application too.

    The concept does work at scale… I’ve seen big mining trucks with tyres that are several meters in diameter using a similar configuration: making a differential at that sort of scale is difficult compared to making large synchronous motors.

    Later, when the batteries are up to the job, the diesel engine can be swapped out for more batteries, the rest of the truck remains the same.

    1. I have read about this type of technology a bit, and yes, it has many advantages, especially in longer distance transportation.

      And one technically don’t need all too much power to keep a truck moving, same goes for cars. Most of the energy is used when accelerating or going up hill.

      Next advantage with electric propulsion systems is the hub motor, as it reduces the need for axles and gears and the idea of taking suspension into consideration when designing the axles, this also reduces drive train losses in these areas as a simple planetary gear between motor and wheel is all that is needed for this drive train. This increases the overall efficiency of the drive train, at the expense of flexible power cables to the motor.

      1. It would also be worth dumping the diesel engine and putting in a sterling enging, they have a similar power to weight ratio but are much more fuel efficient, I’ve never understood why we don’t have them in earth moving equipment,trains and agricultural machines.

        1. >”they have a similar power to weight ratio ”

          They don’t. Stirling engines have terrible power to weight ratio because of the bigger heat exchangers needed, as all the heat – including the waste heat – travels through the engine rather than being expelled through the exhaust. You have to sacrifice efficiency and power to save weight in a Stirling engine.

          If you want a properly efficient engine, you can use a compound turbine engine, with one turbine burning the fuel, and another turbine running on steam generated by the hot exhaust of the first. Properly matched, these reach 60% efficiency.

          1. Are there other external combustion engines that can be more efficient than the Sterling Engine? How will we drive implementations of new material science or new material science?

            The compound turbine engine seems impressive. My Dad swore by they need to use turbines with hybrids… that’s the future.
            Like that’s as close as you’re going to get to a flux capacitor. I do wonder about an ICP/Arc furnace distillation unit… though a blender and classifiers with a turbine can work.

            Maybe he knew what you were talking about because he never denied my solar visions… though swore up and down they have to get the volume of the turbines high enough to drive the price point down or just won’t be feasible since there is the existing infrastructure to compete with (or co-operate with). I’ve seen in a Hummer before.

          2. You’re spot on, my real world experience with Stirling engines is in submarines where there’s no immediate shortage of cooling water, my study experience extands to visiting a DAF factory and loking at a sterling engine that had been fitted to a bus but was unreliable, the cooling for the heat exchanger was apparently fitted into the roof, we didn’t get to see that as the bus was not “available” whatever that meant.
            I think if tesla were to perfect the drive and we accept the compromise of a battey for light trucks, (supermarket, parcels, insulation, and the likes of) and adopted compound turbines for the day to day stuff and keep the mechanical diesel combination for the extreme heavy stuff.
            it might even encourage suprmarkets to use a bit less packaging if they’re loosing space to batteries.

      2. Yes, that was what I was thinking. I’ve not read reviews on the diesel electric locomotives… however… seemed like not a bad idea. I wonder using a more denser fuel or getting the coal industry on board also with the turbines or with fuel additives for external combustion since that would make the militant mafias happy with more dangerous gases and even air mining operations that they probably don’t have the worst unions involved since more complicated processes that the most dangerous unions militants “don’t know what to do.” Seems heat form the electric could be piped/transferred to the external combustion engine. Would create low clearance labor jobs also and maybe less “drill holes and pump” operations.

        1. It is infact unbelievably important, I have a few trailed implements for agricultural use, they’re fine behind old sub 20mph tractors, not so fine behind a 50mph unimog!

    2. Swapping out or other upgrades likely wouldn’t happen. Chattanooga, TN has a fleet of shuttle buses providing free rides around the loop from the aquarium to the old railroad station, and from the aquarium across the river.

      The free shuttles are funded by a cut from the parking lots and garages and by donation boxes on every shuttle and at the two stations.

      The initial fleet used lead-acid batteries. A few of them are still in service. The next generation were made with nickle-cadmium batteries. Likely have or will soon be getting some with lithium-ion. What they haven’t done is upgrade any of the lead-acid ones. Not cost effective they say. They’d have to be majorly dismantled for refurbishment, motors and control systems would have to be changed.

      They have rapid charge systems or if a bus is needed ASAP the battery packs can be swapped in about 15 minutes in the service facility by the old railroad station.

    3. Hybrid drive for heavy trucks already exists, but much like that for hybrid cars that see a lot of highway time, it doesn’t make sense for long haul 18-wheelers. Today’s 18-wheeler is already designed to run its engine at it’s peak efficiency speed when going down the highway thanks to the advent of overdrive transmissions. The hybrid doesn’t really improve on this; where the savings come in is at low speed when starting and stopping a lot. Eaton’s current system delivers up to 30% better fuel economy in urban environments. And Cummins is already working towards releasing an electric delivery tractor, and a hybrid like what you’re describing that will extend the same tractor’s range from 100 miles to 300 miles.

      http://www.google.com/amp/s/www.forbes.com/sites/joannmuller/2017/08/29/take-that-tesla-diesel-engine-giant-cummins-unveils-heavy-duty-truck-

    1. Good call and I was wondering with the “drive by wire” lines embedded in the road way already planning to be implemented in some places… unless that got shot down and who knows.. I wonder how bad the losses would be to have a inductive transfer with the lines embedded in the road and also used as guidance?

    2. We have a few North American cities that have abandoned trolley buses in the last decade or two. They were functional and the overhead in place. Gone. And try to obtain a new right of way for a dedicated railway, busway or highway…. environmental assessments and NIMBY protests. Others have already mentioned Europe and it’s uncoordinated railway overhead power systems. Humans. A hundred people, a hundred surprises. It may take someone like Elon Musk to create a new standard by his shear scope, vision and ability to make a decision…. whatever it is… and then action it.

  10. The success of the tesla itself is built as much on providing infrastructure as well as vehicles. Superchargers are all over the US and Europe making long distance travel in a tesla possible. This is not possible in any other electric vehicle. No other company has done this. So what will Musk do? Superchargers, probably not, but quick change pre-charged batteries and the infrastructure to support them is more likely.

        1. Funny, I thought it was the other way around. Jenny (a Brit) implies the SI units returned by the calculator are not “real world” units because the calculator (which admittedly calls the conversion section “Metric Conversions for the Barbarians”) uses meters per second instead of the much more common vehicle-related units of kilometers per hour. To me, that impugns pedantic metric types because here using SI units does not magically make numbers clear and understandable; what does is using units that are reflexively intuitive because of familiar association.

  11. Maybe…I mean, just maybe…Eylon has his ear to the tracks much closer to the train than those commenting here??????
    I remember a couple years ago…a scientist found that nano-particles of lithium mixed with propylene-glycol was solid at atmospheric pressure…yet liquid at higher pressures. She in-turn used a high pressure nozzle attached to a 3d printer to print batteries 10x smaller at the same energy density….well, simple common sense would tell you that maintaining the current size would make the battery have 10x the energy density….hmmmm…couple that with the research into self healing cell structure that allows 50k more battery cycles…”Big picture”!

  12. Recharge time is a bigger problem than weight. Trying to go cross country on something that takes several hours to get a full charge only adds time to a distribution system that relies on just-in-time shipping. I don’t see this being viable for anything other than final stage deliveries from same city depots.

  13. Seems like another dimension needs to be added from W/kg to W/L when mentioning density. There needs to be volume versus mass considered more-so. Telsa (some days I’d like to say Edison though no one was serious enough there… the pirates won out to secure the bravest forward thinkers) can definitely improve on future potential battery options that charge faster, store more and therefore increase energy density and reduce charge times. Maybe carbon forms and titanates are a way. I’m not the expert on the subject. I personally feel for power distribution and ground storage… let’s use the heavy metals or barium or other not so much we want leaking around the planet on the road or trafficking materials sealed well. Lithium is excellent for on the road or maybe in the air. Even for boats… the heavy metals are good for ballast

    Another opportunity, If weren’t for heat exchange, maybe cracking of cells and existing manufacturing implements is to also consider rolling square cells versus cylinders may be an improvement to save volume and increase density. Density equals mass over volume. Not watts over mass.

    Now, my favorite note is the other sources of energy. Granted… Raney nickel, platinum or other hydrogen storage most likely is cleaner especially if produced by hydro, geo or solar power plants electrolysis or catalyst methods. . Then plutonium is just way awesome. Man, drive by wire thermonuclear external combustion hydrid electric Tesla anything can be the most awesome invention on the planet. Talk about a lot of jobs to secure and maintain nuclear systems. Albeit not low clearance jobs.

    I still think drive by wire to charge and monitor at least if not control is an option that needs to be seriously considered. I don’t like the wireless infrastructure. We need more hardwired and fiber optic. This wireless world of communications is getting insane fast. To much risk and endangerment in my opinion without electromagnetic crimes enforcement. Adding more hard lines where we can inductively charge using the losses from power lines can be accomplished and is a valid way to utilize losses on transmissions on the aerials. This needs to be highly considered versus waste into electromagnetic smog pollution.

    Finally, for charging a system where the mandatory sleep or break period is used to charge during resting is another option to log in an audit trail and assure rest occurs. This would be a way to increase public health and safety also. Great read and thought provoking.

    1. The more I think about the drive by wire coupled with inductive charging via integrating the power lines in the roadways underground maybe with a directional shielding to point in a more coherent direction where the vehicle can be for optimal charge, health can safety… I need to appoint myself as President and CEO of Utilities Loss Mitigation and Profit Sharing. I’m guessing this loss used will be considered free in some countries.

      People… do you realize how much energy we can harvest from the losses? Utilities companies… do you realize how much profit can be made in revenue from vehicle traffic and infrastructure implemented?

      Where’s my 7 digit check please? :-|)

    2. James Analytic: “Density equals mass over volume. Not watts over mass.” Not if you’re talking energy density. Then it can mean either energy (that’s Joules, not Watts) over mass, or energy over volume. Both of these are important when designing something that needs a lot of energy storage. And don’t even talk to me about kilowatt-hours as a measure of energy – I prefer SI units.

      1. Megajoules or Megajoules per liter! Does make life easier using standard units and glossaries for definitions.

        Man, science can be confusing when different scientific disciplines are involved.

        So then, Joules per meter cubed would be more appropriate for energy density. Anecdotally is more energy density using joules per meter squared to me still. Good call.

        So for 160km there can be up to 1% loss say using 1000MW power. Which 10MW losses per 160km. That a lot of megajoules per second (10MJ) lost to thin air or is that what is thinning my hair??? :-)

    1. Those are only legal on certain roads in certain states. Doubles (2x 26′) are the longest multi trailer rig you can have in the US that are legal in 49 states (Hawaii might be different).

  14. Despite the hype the Tesla truck is not intended as a long haul truck for starters it has one seat and lacks a sleeper so they’re not even intending it for long haul.
    Instead it’s actually intended for short range deliveries or for doing stuff such as shuttling trailers around a distribution center which it should excel at.

    1. But where do they sleep normally? I mean you don’t stop in the middle of the road to sleep, you do that at truck stops right? Which could then be recharging spots with Tesla supplied sleeping facilities too.
      I’m sure Tesla has a complex plan, because there was a lot of mention of side-service, like the promise of a fixed price for power and a included service contract I think.

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