So: What About Really Large EVs?

| September 5, 2020 | 48 Comments

Intro

Who says lightning never strikes twice?

Last week, I wrote an article regarding the difficulty of charging a hypothetical all-electric US vehicle fleet with today’s electric grid. But as before, part of a comment to that article made by longtime TAH reader rgr769 caught my eye – and made me wonder:

. . . . I would still like to see an EV Freightliner or Mack tractor pulling a fully loaded trailer uphill. Also, can anyone imagine the size of the battery packs to make that happen or how long it would take to charge them. . . . .

Well, longtime readers can probably see what’s coming – again. (smile) Yeah, I decided to take a reasonably “quick and dirty” look at that too, and also answer the questions rgr769 implicitly asked regarding such a hypothetical EV semi’s battery pack.

Consider yourself forewarned. And yes, as in the previous articles there’s some math involved. But just as before, the math again turns out to be pretty straightforward and simple.

And before anyone asks: no, I didn’t collude with rgr769 (or pay him a retainer) to induce him to make that comment. This is a legitimate pure coincidence; he just happened to raise another question that made me go, “Hmm?”

“Anyway, that’s my story and I’m stickin’ to it.” (smile)

BLUF (Partial): Yeah, We Could Likely Build It Today

So, could we build an EV semi-tractor (hereafter I’ll refer to either the semi-tractor or semi-tractor-trailer combinations as a “semi”) that would climb hills as well as a conventional diesel-powered one? Best I can tell, yes we could – and fairly easily. After all, we’ve been powering trains with electric motors for literally decades.

Here’s one possible way. Per Source 1, a conventional semi’s diesel engine typically produces between 400 and 600 horsepower (hp) and between 1,200 and 2,000 ft-lb of torque. Per Source 2 the motor in the original versions of the Tesla Model 3 produced 258 hp and 317 ft-lb of torque (later improvements raised that to 283 hp and 330 ft-lb of torque) – and those motors are not particularly large (the linked photo shows the motor/rear axle assembly from a Tesla S vice a Tesla Model 3).

Use appropriate multiples of variants of those motors (4 to 6) and synchronize them (easily done), and I’m reasonably sure such a design could generate the horsepower and torque needed. With some moderate redesign to up the horsepower to around 400 and the torque to around 450 ft-lb, you might even be able to mount four of them in or near the semi-tractor’s drive axle assemblies where differentials would normally be located and use one per drive axle, using electronics to precisely control speed and eliminate the need for differentials entirely.

However, those motors would require electricity to operate. Since we’re talking an EV semi, we’re talking stored electricity – and thus a battery pack. How much stored energy? Glad you asked. Let’s figure that out.

EV Semi: How Much Power Required?

How much power does a semi require to keep rolling at highway speed? At a constant speed on perfectly level ground in calm conditions, the power requirement for a semi is minimized. The weight of the load no longer is much if any of a factor; a heavy load might add a bit to drivetrain and axle friction, but I’d guess any such addition would be very small. Rather, the power needed for steady state operation on level ground when it’s calm is dominated by 4 items: aerodynamic load, rolling resistance, accessory load, and drivetrain load – with the first two being far larger than the last two. (If you’re interested, Source 3 explains each of those terms in some detail.) For a typical semi from about a decade ago, per Source 3 those loads were as follows:

Typical Semi Power Requirements, constant 65MPH, level ground/no wind, circa 2010

Aerodynamic load – 114 hp
Rolling resistance – 68 hp
Accessory load – 20 hp
Powertrain load – 12 hp

Total Power Required – 214 hp

As you might have guessed, these loads – which represent the power needed merely to keep rolling at constant speed on perfectly level ground with zero net headwind – are the primary reason why semis on average get around 6.5 MPG (Source 4).

You may have noticed more use of wind deflectors and skirting on semis over the past decade. Those are an attempt to reduce the aerodynamic load component, and thus save fuel.

Let’s assume our hypothetical EV semi achieves a 20% reduction in both aerodynamic load and rolling resistance (more streamlined design and better tires). Let’s assume a 50% reduction in accessory load (on-demand only vice constant drive by vehicle engine wherever possible – but I’d guess that’s about it in terms of a reduction; for an EV, heat/lights/instruments/AC also consume battery power, and drivers are going to need those regardless). And since the transmission and other drivetrain components are greatly simplified in an EV (Tesla uses a 1-speed 9:1 reduction gear in the Tesla 3), let’s assume a 75% reduction here too. That yields the following:

Hypothetical EV Semi Power Requirements, level ground/no wind, constant 65MPH

Aerodynamic load – 91.2 hp
Rolling resistance – 54.4 hp
Average Accessory load – 10 hp
Powertrain load – 3 hp

Total power required – 158.6 hp

So, what’s that in terms of kW – and, more importantly, in kWh, which is a measure of energy stored as battery capacity? That’s actually pretty straighforward to calculate.

One horsepower is approximately 746 watts. So 158.6 hp is equivalent to 118.315 kW, give or take a bit.

Unfortunately, this figure is somewhat optimistic. The power for three of the categories above (aerodynamic load, rolling resistance load, and powertrain load) is mechanical power, and would all be provided through the operation of the hypothetical EV semi’s drive motors – and while electric motors are quite efficient, like all other energy conversion devices they’re not 100% efficient. (The fourth, accessory load, would be a direct electrical load on the battery and therefore shouldn’t require much if any adjustment for electric motor inefficiencies with proper design.) Per Source 5, the highest laboratory demonstrated efficiency for an electric motor to date appears to be 96.5%. Let’s back off that a touch and assume 95% efficiency for the drive motors. (I’d guess this likely somewhat optimistic, but it could be pretty close.) This yields a total power requirement of

( ( (91.2 + 54.4 + 3) hp / .95 ) + 10 hp ) * 0.746 kW/hp = 124.15 kW

Again: this is the power required merely to maintain a speed of 65 MPH on perfectly level ground in calm conditions. It doesn’t account for hills.

At 65 MPH, traveling 1 hour means you go 65 miles. Since a kWh is 1 kilowatt used for a period of one hour, that means we’d need at least 124.15 kWh of stored electricity – that is, at least 124.15 kWh of battery capacity – for each 65 miles driven under those conditions. We’d need more if hills were involved.

How much more? Well, here we go. Now we need to consider the vehicle’s weight and just how much climbing is involved.

How Hills Affect Energy Usage

Climbing hills takes additional energy. This is because you’re adding gravitational potential energy to the vehicle and load by raising its altitude with respect to the earth’s center of mass.

However, electric (and hybrid vehicles with battery packs) can recover some of this energy when they descend by using what’s called regenerative braking. In regenerative braking, a portion of the vehicle’s kinetic energy otherwise lost during braking is used to generate electricity, which can then be used to recharge batteries. That means that some of the extra energy used during a climb can be later recovered during descent and used to recharge the vehicle’s battery. (Conventional vehicles also do this in a limited sense as well; they use far less fuel going downhill than they do on level ground to maintain speed, and in many cases gain speed. They just can’t store any of that excess energy for later use.)

Unfortunately, regenerative braking is also an energy conversion process. And like all other energy conversions processes it’s not 100% efficient either. Source 6 indicates that regenerative braking for the electric vehicles on the road today is between 16% and 70% efficient. So if an EV climbs a hill and then descends to its original elevation today, it will end up with a minimum net loss of somewhere between 30% and 84% of the energy it used to make the climb. And remember: this energy used to make the climb was in addition to the energy needed to keep moving at a constant speed. Further, the additional energy loss occurs each and every time an EV climbs and then descends; the amount of energy lost is determined by the total vertical distance climbed and descended and the efficiency of that vehicle’s regenerative braking.

As you might expect, there’s ongoing research in improving regenerative braking efficiency. Below, I’ll give designers the benefit of the doubt and use 85% for regenerative braking efficiency. That’s probably a bit high, but IMO it’s at least within the realm of the possible without making use of either pentagrams or unicorns. (smile)

Now, let’s consider a couple of examples and see how much energy loss we’re talking about.

Example 1: A single climb of 1,000’ elevation and a matching descent by an EV with 50,000 lb Gross Vehicle Weight (GVW). (FWIW: 50,000 lb is far below the maximum GVW limit for a semi in the US. Per Source 13, the minimum GVW limit for federally-funded highways appears to be 80,000 lb; some states allow far more.)

We’ll do this in three steps. First, we’ll calculate – in kWh – how much energy is required over and above constant-speed driving on level ground with no wind for the vehicle to climb the hill. Next, we’ll calculate 85% of that figure and assume that is returned to the EV’s battery pack (some additional energy might be lost if regenerative braking isn’t sufficient to keep speed under control and conventional friction braking also must be used). The difference between those two numbers is the minimum net lost energy due to the climb and descent.

This is easiest done if we first convert weight and altitude gained to metric units. 50,000 lbs is approximately 22,700 kg; 1,000’ is approximately 304.8 meters. Per Source 7, gravitational potential energy can be calculated as PE = mGh, where PE is the gravitational potential energy; m is the mass of the object involved; G is the Earth’s gravitational constant (9.81 m/sec^2); and h is the change in the object’s altitude (a negative value for h implies the object is being lowered vice raised and is thus is releasing gravitational potential energy vice acquiring it). Since we’re raising the vehicle (climbing a hill), the vehicle is gaining gravitational energy; we therefore must consume additional energy to make the climb. Allowing for 95% motor efficiency, the additional energy required is thus

( 22,700 kg * 304.8 m * 9.81 m/sec^2 ) / .95 ) = 67,874,997.6 J, or about 67.875 MJ

One kWh is equal to 3.6 MJ. So the additional energy required to make the climb, expressed in kWh, is 18.854 kWh.

Sidebar: How about the additional horsepower required? That can also be fairly easily calculated. For a 5% slope, at a constant 65MPH such a climb would take about 3.5 minutes. Expending 18.854 kWh over a period of 3.5 minutes would require an increase in power above the normal cruising power of

( 18.854 kWh / ( 3.5 min / 60 min/hr ) = 323.21+ kW, or about 433.26 hp

The four hypothetical 400 hp / 450 ft-lb torque electric engines on a EV semi would have more than enough horsepower reserve, and would collectively have around 1,800 ft-lb torque. That seems to be enough extra horsepower. I’m not going to check the torque, but 1,800 ft-lb is near the upper end of what conventional semis have today. I’d guess that would also be enough.

FWIW: since conventional semi engines typically have a power output of between 400 to 600 hp and between 1,200 and 2,000 ft-lb of torque, this additional power requirement for such a 5% climb explains why loaded conventional semis have difficulty on long hills.

Assuming that we now descend 1,000 ft and that regenerative braking is 85% efficient, a maximum of 16.026 kWh will be returned to the vehicle’s battery pack by regenerative braking. That means the net energy loss due to the climb and descent of the vehicle is at least the difference between these two figures, or 2.838 kWh.

No, that doesn’t seem like much. But when driving, you’re likely doing far more climbing and descending than you realize.

Example 2: Same vehicle driving over gently rolling terrain

OK, let’s take that same vehicle and drive it on almost – but not quite – level ground with no net change in altitude for one hour. Here, let’s assume the entire trip consists of alternating segments of 0.5% slope (e.g, a 6-inch elevation change every 100’) 2,000 feet in length going uphill followed by a matching 0.5% 2,000’ slope downhill for the entire 65 miles. This is terrain where one climbs and descends 10 feet roughly every 3/4 mile – very gently rolling terrain.

In one hour, the vehicle would drive (65 miles * 5,280 ft/mile) = 343,200 feet. Every 4,000 ft, the vehicle would climb – and then descend – 10 feet. It would therefore repeat the climb/descent 85.8 times in 65 miles.

That means the vehicle would climb and descend 858 feet – even though the net result is zero change in altitude. The vehicle thus would lose 85.8% as much additional energy (due to those repeated gentle climbs and descents) as a vehicle that had climbed, then descended a single 1,000 ft hill. For an EV semi weighing 50,000 lbs gross, that works out to the use of an additional 2.435 kWh of battery capacity during that hour’s driving. And that’s for 10′ high undulations with “ridge crests” (if you want to call them that) spaced about ¾ mile apart. Most roads have more pronounced hills than that, and many have them more frequently.

What happens if you double the slope in the above example? That doubles the distance climbed and descended – and thus doubles the amount of extra energy consumed. Ditto if the undulations are twice as frequent but have same altitude variation. Double both the frequency of undulation and altitude variation? That quadruples the extra energy consumed.

Let me put it in gambler’s language: when it comes to storing energy in a EV’s battery with regenerative braking, “You can’t win and you can’t break even. ‘Cause over time the house is guaranteed to take its ‘cut’.” (smile)

So, About That Battery Pack . . .

OK, so let’s look at a hypothetical example. Let’s use the same 50,000 lb GVW hypothetical EV semi from the above example. What would you need in terms of a battery pack to drive, say, 5 hours over (as defined above) “gently rolling terrain” at a constant 65MPH with no wind?

Turns out that’s fairly easy to calculate. From calculations done previously, driving this hypothetical EV semi at a constant 65MPH on level ground with no wind requires 124.15 kWh of battery capacity. To account for the gentle undulations in the roadway at the specified GVW, add another 2.435 kWh. That means the vehicle will consume 126.585 kWh per hour driven – or about 632.925 kWh of battery capacity is needed for 5 hours driving time. (You’d also need to accelerate the vehicle to 65MPH in the first place. But since the kinetic energy of the vehicle at 65MPH works out to be less than 1 kWh and we’re assuming 85% energy recovery due to regenerative braking, I’m neglecting that. Add in aerodynamic losses and rolling resistance during acceleration and I’d guess that getting up to speed would add maybe another 2 or 3 kWh max to the total energy required, and possibly only 1 kWh or so.)

Most likely, a modest amount of extra battery capacity would need to be included to account for the cumulative effect of larger hills, wind, and weather conditions as well as a general safety factor. I’m going to assume a roughly 15% overcapacity is provided – which means the battery pack would be about 750 kWh. I’ll thus use a battery pack of 750 kWh for the calculations that follow.

That’s equal to 10 Tesla Model 3 extended-range option batteries. (Per Source 2, these batteries have 75kWh capacity, weigh 1,060 lbs, and have a volume of approximately 0.4 cubic meters.). So yeah, you could build something like that. But would it be workable in the real world? And that leads to . . .

“Uh, Houston . . . We Have A Problem”

More precisely, we have three problems.

First problem: charging. A battery that size can be built, but if used for freight hauling it will have to be charged repeatedly; nearly daily would be my guess. And assuming even a 10 hour charge time, a battery with a 750 kWh capacity would require a huge amount of electrical power to charge it. How much? Assuming 92% efficiency for the battery charger (the rationale for that 92% figure is in my previous article concerning EVs linked at the beginning) and completely uniform charging over a 10 hour period, that works out to

( 750 kWh ) / (.92 * 10 hrs) = 81.5 kW

Assuming a power factor of 1 and assuming an invariant load from the charger (these conditions are the best possible case in terms of minimizing the charging current required), per Source 8 that means you’d need a 240v circuit capable of handling at a minimum 339+ Amps – or a circuit rated around 340 Amps, and probably larger to include some safety margin. Even using 480v 3-phase power, again per Source 8 you’d need 98+ Amps – or a 100 Amp circuit, and again probably larger to allow for some safety margin.

Oh, and that battery charger is going to get rather hot, too. With a power factor of 1, it’s going to be rejecting most of the energy it doesn’t deliver to the battery as waste heat (the batteries themselves and the conductors connecting the charger to the vehicle will reject some smaller portion of the charging loss). That’s a heat output of roughly 6.5 kW – or the equivalent of between 4 and 5 1500-watt space heaters all operating simultaneously at max output.

Now, large truck stops today have large parking areas. But I don’t think they’re typically big enough to handle 100 or 200 trucks parked, simultaneously, and staying there for 10 hours at a time each while charging their batteries. And I don’t think they’re typically serviced by multi-MW electrical feeds, either (81.5kW x 100 = 8.15 MW). Plus, with 100 trucks each of which is generating 6.5kW of waste heat while charging those huge batteries, well, if you liked summer in Kuwait . . . you just might enjoy walking around that charging yard. (smile)

Yes, you could charge those battery packs slower using far less power. But that means you’d have to swap the discharged battery pack for a fully-charged one daily – and would have to have spares on-hand. At a trucking company’s maintenance facility? That might be possible. (Whether it could be done safely or not is another question. Even a “discharged” 750 kWh battery pack still would contain enough energy to be deadly dangerous if mishandled.) Doing it at a truck stop or hotel parking lot during a nightly rest stop? “Good luck wit dat.”

Second problem: 750 kWh is probably less than half of what you’d really need for long-haul trucking.

Per Federal Motor Carrier Safety Administration (hereafter FMCSA) rules (see Source 10), long-haul truckers are allowed to drive 11 hrs daily within a 14 hour “duty day” window, followed by a mandatory 10-hour “off duty” period (there are numerous other limitations/restrictions/exemptions, but that’s the one that’s generally going to be pertinent here). Further, truckers must take a half-hour break from driving during their duty day; this break must occur NLT 8 hour after they begin driving during their duty day.

OK, so let’s consider driving 11 hours at 65 MPH. That’s a touch over 700 miles in one day.

Do long-haul truckers routinely do something close to that, particularly west of the Mississippi where speed limits are higher and traffic is generally less congested than in the Eastern US? That is, do they often drive 10 hours or so at an average speed of 65+ MPH in one day? I’ll go out on a limb here and say, “You betcha!” – though I really don’t know that with certainty. But If I’m wrong, I’m sure one of our readers with personal experience working in the field can (and will) correct me. For a long-haul trucker, more miles driven generally means more cash in their pocket.

Bottom line: 5 hours at 65MPH realistically seems to be about half of what would be required for a semi to be used in long-haul trucking. With a multi-hour recharge time, given the maximum 14 hour duty day followed by the 10 hour mandatory off-duty period imposed by FMCSA you’d need the battery capacity to go at least twice as far as that 750 kWh battery pack allows in order for the vehicle to be useful for long-haul trucking.

Third problem: weight. A 750kWh battery pack would be equivalent to 10 Tesla Model 3 extended range battery packs. As previously noted, a Tesla Model 3 extended range battery pack weighs 1,060 lbs and has a volume of 0.4 cubic meters, and probably represents about the best EV battery technology mankind currently can produce in quantity. So we could expect a 750 kWh battery pack to weigh roughly 10,600 lbs and have a volume of around 4 cubic meters (think a rectangular cuboid that’s 1m x 2m x 2m, or about 3’ 3½” h x 6’ 7” l x 6’ 7” w ).

A 1,500 kWh battery pack would be about twice that in terms of size and weight. It would have a volume of 8 cubic meters (e.g., it would have the same volume as a cube 2 meters on a side). That 1,500 kWh battery would also weigh around 21,200 lbs, or roughly 10.6 tons – far more than combined weight of the engine, transmission, fuel tank, fuel, and other fluids used in a conventional semi. (For the record, the 10,600 lbs estimated for the 750 kWh battery pack above also is heavier than the engine/transmission/etc . . . in a conventional semi today.) Since GVW limits exist, presumably for good reason, what do you think that battery weight is going to do to an EV semi’s maximum cargo capacity in terms of max allowable cargo weight?

Conclusions

IMO, we now have an answer to rgr769’s implicit questions. First: yes, it appears technically feasible to build an EV semi that could move loads and make substantial climbs. Building the batteries would be technically possible, and the motor technology (in terms of the required torque and horsepower) appears eminently do-able as well. We’ve been building diesel-electric trains for decades; building a suitable electric motor was IMO never the issue. Whether we could build a battery of sufficient capacity was the key question, and it appears we could.

However, whether such a vehicle would be useful or not is another question entirely. For long-haul freight, the answer today seems to be a firm “No”, and perhaps even “No way in hell.” While the battery pack required can at least in theory be produced, at 10.6 tons it would simply be too heavy to be practical. And the power distribution infrastructure to support charging large trucks on the scale required during the FMCSA-mandated 10-hour “off duty” time required for long-haul truckers after a maximum 14-hour “duty day” . . . simply doesn’t exist. Could it be installed? In theory, yes. But I’d guess serious proposals for installing same would likely produce a “You’re joking – right?” moment when those proposals were presented to utility company leadership.

Why? Because as demonstrated above, the amount of power required to charge 100 large EV semi’s each having only half the battery capacity needed for long-haul trucking simultaneously in 10 hours would be huge – as in approaching 10 megawatts. Since per Source 14 one megawatt of constant electrical power typically can power 400 or more homes, that means you’re talking the equivalent of s medium-sized town’s or small city’s electrical power supply for each 100-EV semi charging lot – and you’d need twice that if you had the batteries actually required for long-haul trucking.

Even a small facility that could charge only 10 trucks would need 1 to 2 megawatts of electrical supply, and possibly substantially more if charging EV semi batteries does not draw a constant load. (Real-world data on charging LiIon batteries from Source 9 indicates that the charging load is not likely to be constant.) EV semi charging locations would thus not be terribly common, at least initially. Large trucks would tend to congregate at the few facilities that would be available. And the waste heat generated during charging (around 8% of the power supplied by the electric grid to the chargers) would make such charging yards local “hot spots” – literally.

So, how can current semis do what they do today? Easy – it’s because of diesel fuel’s high energy density. Hydrocarbon fuels have hugely larger energy densities than LiIon batteries. As an example: per Source 11, diesel fuel has an energy content of 38.6 MJ per liter – or about 40.53 kWh per gallon. That means a bit over 18.5 gallons of diesel fuel, weighing around 125 lbs, has the same energy content as the electrical energy stored in the hypothetical five-ton-plus 750 kWh LiIon battery discussed above. Even if you only recover a bit over 1/3 of diesel fuel’s energy content in the form of mechanical or electrical energy, you’d still only need somewhere around 50 gallons of diesel fuel, give or take, to provide the same amount of usable mechanical or electrical energy as a 750 kWh battery pack can store.

Real-world data bears that out. As I noted previously, per Source 4 in the real world conventional semis average somewhere around 6.5 miles per gallon. That means that a hypothetical drive of 325 miles in a conventional semi would require about 50 gallons of diesel fuel – 60 gallons if you want a 20% safety factor. Assuming a weight of 6.65 lb per gallon, the former would weigh somewhat less than 350 lbs; the latter, around 400 lbs. Even after considering the weight of the conventional engine/transmission/fuel tank/other fluids/associated equipment needed, that represents a significant weight savings over an EV semi using the best current technology; that in turn allows more cargo to be hauled. Plus, replacing that 50 or 60 gallons of fuel (thus adding another 325+ miles of range) takes a few minutes, not literally hours. In fact, it can be done in conjunction with that mandatory half-hour “break” required NLT 8 hrs after a long-range driver begins driving for the day – or when the driver makes a longer stop for a meal. Then the trip can continue on until the daily driving hours limit is reached.

Oh, and did I mention you’d need to be able to drive twice that far – and thus would need twice as large a battery (e.g., around 1,500 kWh) – for a hypothetical EV semi to be usable for long-haul trucking? Which in turn means the battery would be twice as large, twice as heavy, and take twice as much power to charge (and reject twice as much heat) during that daily 10-hour “off duty” period? Well, if I didn’t before . . . I guess I just did. (smile)

. . .

Do EV semis (or somewhat smaller non-articulated EV trucks and buses) have a role? For local use, perhaps. Even that is questionable at present, though. Source 12 indicates that LA and other locations have tried pilot projects involving electric buses and found them to have serious reliability and range issues.

But for long-haul operations, given the current state of technology those hypothetical EV semis appear to be more like the original cast of SNL: “The Not Ready for Prime Time Players”. IMO it would take a major breakthrough in battery technology along with truly serious upgrades to the electrical grid – or a change to some technology that generates electrical energy on-vehicle vice storing same in a battery – to make electric semis/trucks/buses feasible for long-distance use.

Or, as country folks might put it: “Ain’t enough lipstick in the whole world today to make that pig look purdy.” (smile)

———-

Sources:

1 – Typical Conventional Semi Engine Power and Torque: https://www.internationalusedtrucks.com/semi-truck-horsepower/

2 – Wikipedia article, Tesla Model 3: https://en.wikipedia.org/wiki/Tesla_Model_3

3 – Semi Steady-Speed Power Requirements: https://www.nap.edu/read/13288/chapter/7#79

4 – Typical Semi Fuel Economy: https://www.arrowtruck.com/blog/2016/06/21/manage-your-semi-trucks-fuel-use-with-these-tips/

5 – Wikipedia article, Electric motors: https://en.wikipedia.org/wiki/Electric_motor

6 – Regenerative Braking: https://www.sciencedirect.com/topics/engineering/regenerative-braking

7 – CalculatorSoup Gravitational Potential Energy Calculator: https://www.calculatorsoup.com/calculators/physics/gravitational-potential.php

8 – RapidTables Kilowatts to Amps Calculator: https://www.rapidtables.com/calc/electric/kW_to_Amp_Calculator.html

9 – Battery University, BU-409: Charging Lithium-ion: https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

10 – FMCSA Interstate Truck Drivers Guide to Hours of Service: https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/Drivers_Guide_to_HOS_2016.pdf

11 – Wikipedia article, Energy Density: https://en.wikipedia.org/wiki/Energy_density

12 – Google Cached LA Times Article: “Stalls, stops and breakdowns: Problems plague push for electric buses” https://webcache.googleusercontent.com/search?q=cache:q9TtqnnFrToJ:https://www.latimes.com/local/lanow/la-me-electric-buses-20180520-story.html+&cd=1&hl=en&ct=clnk&gl=us&client=firefox-b-1-d

13 – US and Canada Semi Weight and Size limits: https://www.bigtruckguide.com/semi-truck-size-and-weight-laws-in-the-united-states-and-canada/

14 – Number of US Homes Powered by 1 MW – https://www.nrc.gov/docs/ML1209/ML120960701.pdf

Category: "Truth or fiction?", Economy, Global Warming Voodoo, Reality Check, Science and Technology

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  1. Wireman611 says:

    Picking 65 mph for the speed might b a tad low. During my commute, I’ve noticed the average speed of the semi’s to be 70 to 75 mph. this would dramatically affect the wind and rolling friction losses. Also, wouldn’t the lot lizards get toasted?

    • Hondo says:

      Agreed. Unfortunately, my source for that info appears to have used 65MPH – and their graphs for aero and rolling resistance stop at about 65MPH. I was reluctant to even attempt to guess the numbers for aero 70 or 75 MPH. The aero load is quite nonlinear (and thus very hard to guesstimate without more info). And while the rolling resistance appears to increase linearly, without the ability to project the much larger aero load estimating rolling resistance for 70 or 75 MPH IMO seemed kinda pointless.

  2. USAFRetired says:

    There is a reason why todays freight train locomotives are how they are. They use high torque electric motors to drive the wheels, powered by the onboard diesel generators.

    • 26Limabeans says:

      And those motors are series wound for high starting torque.
      Just like the subway trains which present a good example of
      how much power is needed to haul a train full of people with
      frequent starts and stops. Operating at 600 VDC you can see the
      overhead lights dim as the conductor moves the lever in steps.
      That third rail has to be a rail to handle the current.

      Diesel electric is the most efficient method of hauling frieght.
      And the most controlable with seperate motors on each wheel.

      Battery power is for flashlights and cell phones.

  3. 5th/77th FA says:

    DAAAAAAAAAYYUUUUUUUMM!!! I can’t believe I read and comprehended the whole thing. Don’t know who to kick harder, rgr769 for asking the question, or you for gloatingly high climbing/rising to the occasion to answer the question with all of the technical legalease. I followed the lesson plan, but..sumbitch, way yonder too early in the morning for that kind of cyphering, too many goezentas. And what about poor ol’ Pappy, The Stranger? As an engineer he has the background to grasp ALL of that but he was up most of the evening, sampling Yuenglings and smoking brisket with salmon.

    Reader’s Digest version answer…Tesla and Elon Musk is working on it! The bat-tree semi that is:

    https://en.wikipedia.org/wiki/Tesla_Semi

  4. Ex-PH2 says:

    – we’ve been powering trains with electric motors for literally decades. – Hondo

    This is correct, Hondo, but the fact is that passenger rail like commuter trains are powered directly, through the so-called 3rd rail. That is how Chicago runs the El trains and NYC does the same thing.

    Here’s a quote about New York’s rail system:
    In politics the third rail is an issue so powerful, politicians do their best to avoid it. In the subway the third rail is a line of track so powerful, patrons make sure they avoid it.

    And rightly so, since Metro’s trains run on 800 volts – enough to propel a packed rush-hour train at speeds of up to 70 mph through the Red Line tunnel between Hollywood/Highland and Universal City station.

    On subway trains, the third rail is the source of the electrical delivery system. The same power is delivered to light-rail lines such as the Blue, Gold, Green and Expo lines via an overhead catenary system. No petroleum gas for the trains. No CNG (compressed natural gas). Just good old-fashioned electricity.

    Where does the electricity come from? Like petroleum gasoline and compressed natural gas, Metro buys it. Electricity can be a product of nuclear, coal, gas, oil, water, wind or solar farm sources. In Metro’s case, the intermediary source is utility companies, including LADWP and Pasadena Water and Power — the same companies that supply power to many of our homes.
    Source: https://thesource.metro.net/2012/03/05/how-do-they-do-that-power-the-trains/

    For Chicago:

    Trains: Our fleet of about 1,500 rail cars carries about half of all our riders.

    Electric rail is a highly efficient motorized transport mode, operating on low-friction steel rails.
    CTA has begun putting a new family of ‘L’ cars into service, known as the 5000 Series. These railcars are equipped with an innovative braking system that can transfer electricity back to the third rail, supplementing power to nearby CTA trains.
    In April 2017, a report was produced following a study on how implementing a Wayside Energy Storage System (or WESS) would impact the CTA Red Line. Read the Red Line WESS report.

    Buses: We have a fleet of nearly 1,900 buses, which, thanks to new technology and recent replacement efforts, have been becoming more energy efficient and produce fewer emissions.
    We converted our entire bus fleet to ultra-low sulfur diesel in March 2003, well before the US Environmental Protection Agency mandated its use in October 2006. All buses delivered since 2007 have clean-diesel engines and particulate filters that meet EPA emissions standards.
    Emissions of key pollutants from our bus fleet decreased thanks to retrofitting and replacement work, including nitrogen oxides, hydrocarbons, carbon monoxide and particulate matter.
    We’ve employed technologies at garages for our hundreds of hybrid buses that allow buses to keep warm and minimize engine idling during cold winter months.
    Following a successful year-long operation of Chicago’s first two all-electric buses, we announced in 2016 plans for the nation’s second largest transit agency to purchase between 20-30 additional all-electric buses in the next few years,
    In 2011, we received federal Congestion Mitigation and Air Quality Improvement Program (CMAQ) grants for installing two bus fuel-efficiency technologies: $900,000 for Topodyne transmission software and $6.2 million for all-electric cooling fans.
    Our support vehicle fleet includes hybrid-electric SUVs, sedans and pickup trucks, vehicles that can run on 85% ethanol gasoline, and some vehicles that run on clean-burning compressed natural gas.
    Source: https://www.transitchicago.com/environment/

    In regard to suburban passenger transit, Metra is Chicago’s rail line, has been for decades, and has always been electrified.

    The Metra Electric District is an electrified commuter rail line owned and operated by Metra which connects Millennium Station (formerly Randolph Street Station), in downtown Chicago, with the city’s southern suburbs. As of 2018, it is the fifth busiest of Metra’s 11 lines, after the BNSF, UP-NW, UP-N, and UP-W with nearly 7.7 million annual riders.[2] While Metra does not explicitly refer to any of its lines by color, the timetable accents for the Metra Electric District are printed in bright “Panama orange” to reflect the line’s origins with the Illinois Central Railroad (IC) and its Panama Limited passenger train.[3] Apart from the spots where its tracks run parallel to other main lines, it is the only Metra line running entirely on dedicated passenger tracks, with no freight trains operating anywhere on the actual route itself (only exceptions perhaps being occasional work or repair trains). The line is the only one in the Metra system with more than one station in Downtown Chicago, and also has the highest number of stations (49) than any other Metra line.

    It is the only Metra line powered by overhead catenary, and the only one with three branches. Trains operate on 1500 volts direct current, and all stations have high-level platforms. Its main line north of Kensington is shared by NICTD’s South Shore Line, an electric interurban line through northern Indiana to South Bend. Per a longstanding non-compete agreement, South Shore trains stopping at stations shared with the Electric District only stop to pick up passengers eastbound and discharge them westbound.
    Source: https://en.wikipedia.org/wiki/Metra_Electric_District

    The loads these vehicles pull is possible because of the constant supply of voltage to the lines. That makes is practical and no one pays any attention to it.

    Electrification of city buses goes back a long way. When we used to visit my grandmother and her three sisters in Nebraska, downtown Lincoln had electrified buses with the overhead catenary attached to them. That was in the 1950s.

    These are practical applications of EV use that have been available for literally decades. Over the road stuff will only work for long distance hauling of heavy loads if there is a similar network available to power the vehicles.

    • Hondo says:

      Yes, electrified rail/tram/other systems work well – in large urban areas where they can service large populations on a limited number of routes of relatively short distance. But scalability (due to high capital costs required) leaves something to be desired. That’s the reason the vast majority of US trains used for long-distance freight and passenger service are diesel electric. Today, other than urban commuter systems the US appears to have somewhere around 1,000 miles of electrified railway systems.

      https://en.wikipedia.org/wiki/Railroad_electrification_in_the_United_States#Overview_of_electrification_in_the_U.S.

      The US Interstate Highway system has a bit under 47,000 total miles. Good luck with installing a 3-rail or other type of electrical power system on that – and with powering it if you do. And that doesn’t address Federal (non-Interstate) highways, state highways, county highways, and other roads over which freight is occasionally hauled.

  5. Ret_25X says:

    and once again we show that the problem for EV is not the electricity, but power storage and transmission.

    Some material breakthroughs are on the horizon for batteries which may resolve some of this side of the problem.

    The grid itself is the other problem. The American transmission grid is not designed or capable of carrying a 100–300% increase in total capacity without major upgrades.

    Where will the copper, steel, rubber, transformers, insulators, etc, etc, come from? They will all have to be mined, milled, manufactured, and installed.

    Too bad almost none of it is made in the USA anymore…

    If you don’t want to see us move to an electric based system you aren’t thinking ahead.

    If you want it done now, you aren’t thinking.

    • Hondo says:

      If you don’t want to see us move to an electric based system you aren’t thinking ahead.

      Possibly true, possibly not. Given enough cheap energy (high-temp or electricity), it’s possible to produce other fuels that will run in today’s ICEs with relatively minor modifications (they would be usable in fuel cells just as easily, hence the “possibly true” category).

      But I wouldn’t hold my breath waiting for batteries to “catch up” any time soon. Today we can recover the same amount of useful mechanical work from less than 350 lbs of diesel fuel that could be provided by a 10,600 lb advanced LiIon battery unit. To be weight-competitive with hydrocarbon fuels, you’re talking improving battery energy storage density (with respect to weight) by a factor of 30+.

      I’m not gonna hold my breath waiting for that degree of improvement. And as you pointed out, even that doesn’t solve the charging issue, either in terms of distribution or time required.

      If those other fuels I’m talking about were produced using, say, lawn or other agricultural waste as raw material – or from non-carbon-containing raw materials – there would also be little to no net additional carbon emissions generated (lawn and other agricultural waste decay, and decay is in general a merely a rather slow oxidation process). We know how to do both; access to the energy required to make the conversion and process efficiency are the roadblocks.

      We know today how to produce as much zero-carbon-emission energy (both electricity and high-temp) as we want today from reliable sources that can last for hundreds of years if used correctly. We also know how to deal with the miniscule amount of truly hazardous waste that would be produced. Thank Jimmy the Peanut and the anti-nuke movement of the 1970s for making that politically difficult if not impossible today.

      Developing the technology to make some of those other fuels from cellulose-containing wastes efficiently would require some effort (we can do it today, but the process is relatively inefficient). We know today how to make a different alternative, portable chemical fuel to replace petrochemical fuels containing zero carbon; unfortunately, it would require some materials development research to be long-term useful in today’s ICEs as well as huge quantities of electricity. (It would be immediately useful in fuel cells, however.)

      I’ll deal with this in the last article I plan to write on the subject of EVs. I plan at least 2 more articles.

  6. A Proud Infidel®™️ says:

    Electric trucks might do fine and dandy for local service or in flatlands, but I have doubts about what’s currently available for going say, Interstate 70 going West of Denver where it has to duel with Eisenhower an Vail Passes (Loveland Pass if hauling HAZMAT) and would said power storage be considered HAZMAT thus making them prohibited from going through Eisenhower Tunnel?

    • Hondo says:

      Not certain, API. Does the Eisenhower Tunnel ban EVs and hybrids today? Because each of those use LiIon batteries today – and in the case of an extended-range Tesla Model 3, you’re talking a LiIon battery pack weighing more than half a ton.

      • A Proud Infidel®™️ says:

        The amount means a lot as well because a lot of HAZMAT doesn’t require a placard unless there is 1000 pounds or more.

        • Hondo says:

          Thanks for the info; I didn’t know that.

          If LiIon batteries fall in that HAZMAT category then perhaps that could be a problem. Unless, of course, whatever agency governs HAZMAT rules for vehicles decides to give EVs an exemption for their on-board battery pack.

  7. Slow Joe says:

    Excellent research.

    I would say that a trans company using self driven trucks like the ones being tested in Arizona right now could get their money’s worth, but your are absolutely right that battery weight probably makes it ineffective economically.

    What about hybrid semis?
    Could a little gas engine recharge the batteries during operation?
    Would it be economically viable?

    The battery weight would still eat part of the available cargo weight…

  8. Green Thumb says:

    Batteries are heavy in a rucksack….

  9. Hack Stone says:

    Allow Hack to provide the inspiration for another chapter in the continuing saga of Unintended Consequences To Converting To All Electrical Vehicles. What happens to these vehicles when they reach end of life? Al Gore’s Amazing Internet has been inundated with tales of municipal governments and utility companies trying (unsuccessfully) to dispose of obsolete wind turbine blades and solar panels, so what you is the plan when these electric vehicles take their final journey? And that’s just what is anticipated. What happens when a major collision occurs in Mayberry involving multiple electrical vehicles? The HazMat response will wipe out Mayberry’s budget, not to mention all of those battery chemicals leaking into the local sewage system and dumping into the town water supply.

    • Hondo says:

      Probably not something I’ll tackle, Hack. I don’t really have the background in toxic materials and environmental engineering needed to do an analysis of how to handle the aftermath of an EV incident or how much of a toxic hazard that would pose. Sorry.

      From what little I do know about LiIon batteries, the environmental effect of such an incident might be less than you’d think. Most of the materials used in a LiIon battery seem to be fairly benign to only mildly toxic; the major hazard appears to be fire where the LiIon batteries’ electrolytes – which are typically organic compounds – catch fire and burn. (The batteries themselves also can generate oxygen, if I recall correctly.) Though they’d give off some degree of toxic smoke like any other fire, I’d guess that’s probably about the extent of the toxic aftermath.

      My guess is that a collision between two fuel tankers that didn’t burn but spilled over a large area and into a creek would be a far bigger HAZMAT and environmental problem. But I really don’t know, and I could easily be wrong.

  10. I wish I still had the video which I would have sent to Admin about a battery change on a tesla. Driver opens up a little door on the side of the car and like a trillion zillion AAA Batteries drop out onto the pavement. Very funny. And Hondo, I hope you listen to Give Me Forty Acres And I’ll Turn This Rig around while your gear jamming down the highway, and I bet you you can get the rpms up, and drop it into gear without using the clutch. Learned that on a !950’s Mack truck at Brink’s.

  11. Poetrooper says:

    The above explication represents why one should never ask Hondo what time it is unless one has the time to learn how Hondo’s watch was made and everything about the human concept of time itself…

    😜😜😜

    • David says:

      Thank God he isn’t a REAL engineer, he would start with space/time theory.

      • Hondo says:

        Nah. Unless they’re dealing with things very small (e.g., nanotechnology or cutting-edge chip design) or other cutting-edge research, engineers don’t usually worry about those kind of details. They’re usually more worried about practical stuff – like making things work in the everyday world. They mostly leave that kind of more esoteric stuff to the physicists. (smile)

        Besides, at the macro level we’re talking about here spacetime theory doesn’t come into play. It’s pretty much all classic thermo, efficiency, and simple AC electricity – along with doing unit conversions correctly and remembering to convert energy to power (and vice versa) properly.

  12. Poetrooper says:

    The above explication represents why one should never ask Hondo what time it is unless one has the time to learn how Hondo’s watch was made and everything about the human concept of time itself…

    😜😜😜

  13. Poetrooper says:

    Admin, why did my comment post twice? I clicked once.

  14. Stacy0311 says:

    And after we account for all the electricity needed for cars and long haul trucking, we’ll have to look at the energy needs for farm equipment, construction equipment. And then replacements for all of the other products made from fossil fuels.

    Research, sure.
    Replace everything NOW, not a chance.
    And the people (looking at you AOC) screaming about a Green Nude Eel, should not be allowed outside without adult supervision, a safety helmet and a mouth guard

  15. David says:

    Big trucks with easily interchangeable battery packs, driven only replacement hub to replacement hub. Truck rolls in, battery is offloaded along with load, new battery pack installed as new load is onloaded. Expended battery packs recharged for reuse. Local trucks deliver, round trip to hub for battery change. Each truck requires minimum 4 battery packs.
    That’s 20 tons of weight per truck and the aforementioned generation and distribution infrastructure. Offset that by how much we spend on refineries, pipelines, gas stations, etc. and maybe you can pay for what, 20% of it. Or just click your heels three times…

  16. rgr769 says:

    And I can confirm I was not in cahoots with Hondo on this question. I was merely speculating that I doubted that current battery technology being what is, it is unlikely EV semi-trucks doing long hauls was feasible. Thanks Hondo for doing the homework to answer my speculation. Once again you proved math is hard, but the numbers are immutable, not flexible like the Progs want us to believe. I guess the Green New Deal can only work if we can torture 2+2 to equal 5.

    • Hondo says:

      Did someone say “2+2=5”? Well, here ya go:

      (smile)

    • OWB says:

      Wouldn’t discount the possibility at all. Perhaps not in our lifetime, but maybe some of us will see it.

      Remember when computers took up multiple floors of large buildings? Now we have more computing capacity in a wrist watch than was available for the early space program. Sure, power sources are very different from computers but the analogy s not totally flawed either. Batteries in my telephones are much smaller, last much longer, and recharge more quickly than the one in my first few laptops, probably even this one.

      Sure, it could happen. Seems bizarre, sure, but it is also obvious from looking at a 747 that it won’t fly.

      • rgr769 says:

        How do you think we are going to generate all the electricity to charge these batteries that will run everything. The green new dealers don’t want any fossil fuels to power anything, period. Think they are going to increase the power of the sun and the wind? They certainly won’t ever approve another nuclear power plant. I don’t think there will be non-fossil fuel powered aircraft in the lifetimes of my grandchildren. Seen the plans for a battery powered 757 anywhere?

        • OWB says:

          I don’t know but have lived long enough to see that a whole lot of things I could not imagine are now commonly in use.

          For instance, the flex vehicles that basically charge themselves have become pretty darned efficient in the past 10 years or so. If that trend continues they just may soon need no fossil fuels at all beyond the original construction of the vehicle. And maybe some day not even that.

          No, I have no ability to devine the future with any specificity. But there are still dreamers around with enough skills to make the impossible into reality.

          And yes, it irritates me no end to see the publicly funded charging station outside my library that cost an incredible amount to install and in the 3 or 4 years it’s been there I have seen only one vehicle plugged into it. What a waste, just to feed the ego of some pompous snowflake who feels all superior to the rest of us, AND expects us to pay for his folly.

        • John Ryan says:

          It is estimated that at current efficiency levels it would take an area of about the size of the Mojave dessert
          A quick google search will show that both Airbus and Boeing are already working on large electric passenger planes
          An Israeli/Singapore company expects first flights this year of a 10 passenger 500 Mile range commuter regional plane

          • Hondo says:

            Regarding “an area the size of the Mojave”, I presume you’re talking using solar.

            Solar power produces close to rated output power levels for about 6 to 8 hrs daily. To replace our current electrical grid’s power with solar, that means you’d need to generate 3 to 4 times the typical US daily electricity during that 8 hrs – then store between 2/3 and 3/4 of the typical daily US demand somewhere until needed. Given high-demand days are a reality, I’d guess more like 3/4 would require storage.

            The largest operating electrical energy storage unit in the world is the Bath County Pumped Hydro storage facility in Virginia. It can store 24,000 MWh of electricity – or the daily output of a single 1,000 MWe generating plant.

            In 2018, per Wikipedia US annual electrical power consumption was 4,222.5 terawatt-hrs – or an average of 11.586+ terawatt-hrs per day. That in turn means we’d need to store at least 2/3 of that – or 7.712+ terawatt-hrs – in order to meet US electrical consumption requirements. More likely we’d need to store more to account for days with higher-than-normal demand.

            One terawatt-hr is one million MW-hrs, and pumped hydro is around 75% efficient. That means you’d need at least an additional 322 Bath County Pumped Hydro Storage stations to store the extra – and probably far more than that to give a reasonable safety factor for high-demand days. You’d also need at least another 2.6 terawatt-hours of additional generation daily just to do the pumping for that pumped storage (25% loss overall).

            “Good luck wit dat.”

  17. MI Ranger says:

    So what is Mr. Musk doing with his Huge electric truck he drove to the Press when he first unveiled he was making an electric Pick-up Truck?
    So Hondo, how does the Energy density of Hydrogen compare with this? I have been seeing a lot with GM and their Hydrogen Fuel cells, which are much more “eco friendly” than fossil fuels since their only bi-product is water. GM is pushing for a military vehicle with a hydrogen fuel cell. I have also seen a lot of UAVs with Hydrogen fuel cells. Their power to weight ratio is much better than electric UAVs. So is it as good with cars and trucks?

  18. John Ryan says:

    At the current rate of improvement in battery design what might be a reasonable estimate of when EV semis are BETTER than diesels ?
    Look at how far electric cars have gone in the last 20 years

    • Hondo says:

      As I noted in my comment above: don’t hold your breath.

      For EVs to be competitive, IMO their batteries’ energy density would need to approach 1/2 of that which can be recovered from hydrocarbon fuels as useful mechanical work. Right now hydrocarbon fuels have around a 31:1 advantage in terms of usable energy density. That means you’d have to improve battery energy density by a factor of 15 or so.

      We’ve had alkaline cells pretty much for the last 50 years, and nicads for about as long. The energy density of an alkaline C-cell is about 0.53 MJ/kg; a nicad is somewhat less (lower operating voltage). For comparison, the energy density of current LiIon batteries are at max around 1.06MJ/kg. That means we’ve improved the energy storage density of batteries by a factor of 2 in 50 years.

      If you want an estimate in years, assuming we can double that rate of progress re: battery energy density we would have a suitable battery after doubling battery energy density an additional 4 times (2^4 = 16). With each doubling assumed to take 25 years (twice the rate we’ve seen over the last 50 years), that means we’d have a suitable battery in around 100 years. I’ll be generous and say we do even better than that and have one in between 50 and 75 years – maybe.

      Even if we had the batteries today, we’d still have an monumental problem. As I noted above, the charging infrastructure doesn’t exist today and won’t any time soon. And as my previous article on EVs indicated, the current US electric grid couldn’t charge them all even if the distribution and charging infrastructure was in place today.

      Now, if you want to consider a vehicle powered by an electric motor that generates its electricity from an onboard fueled power source, that’s probably doable today. We’ve had fuel cells for decades, and engine-driven generators for far longer than that. The latter is mature technology and is used on trains today. The former could use either hydrogen or certain hydrocarbon fuels, and is substantially more efficient with respect to producing usable energy from fuel than is an ICE.

  19. 26Limabeans says:

    If the skin of vehicles were somehow made of solar cells the amount of
    power produced would maybe run the blower motor for the heater or
    air conditioner on a sunny day. At noon. On the equator.

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