Warning Tesla is a cult now, i never thought id find such a Gem.

[David Green]

If your objective is to expose your ignorance on the subject, then you've succeeded handily, "Mr. Clean Diesel". Heck, even my earlier generic "napkin math" analysis of a hypothetical BEV semi tractor estimated only 10.35 tons of batteries, and Tesla's battery pack turned out to be somewhat smaller than my estimate of 1800 kWh of capacity.

There are of course further weight savings from replacing the large, heavy diesel engine and transmission with a few electric motors and simple reduction gears, plus weight savings from not having to carry fuel, or an exhaust system, or various other ancillary devices a diesel truck needs but a BEV truck doesn't.

It looks like you're trying to do more Tesla bashing, dude. But you do it so very poorly!
-

There is no doubt the Semi can be done, but my point is that Tesla has not done a clear / verifiable demonstration of the capabilities. I will believe it when I see it is not Tesla bashing, but more using my own understanding of EV and battery tech and applying it to my trucks and the rigors they go through. Tesla has been caught with their semi being hauled around the country on the back of diesels in fans pictures that ended up on the internet. Even the latest picture is of the semi running bobtail with a diesel closely following it towing the trailer. I will admit to being slightly skeptical to Teslas claims, but Tesla has been sneaky before and not open and honest about their real world capabilities. On the semi, one thing that people who are not in the trucking industry do not understand, is going down the highway and over the mountains is where a diesel engine is the most efficient as the turbo charger stays wound up, and there is sufficient heat in the engine( this is the time when efficiency is the highest and emissions are the lowest), around town, and stop and go is where a diesel sucks. Thats why for example the BYD buses out of China are so great and make so much difference. The BYD buses operate in constant stop and go which is the place BEV's really excel. Tesla seems to be so caught up with acceleration, and I can tell you in a truck that is unnecessary, range is by far the most important element. Semi trucks do not go stoplight to stoplight having drag races.

 

[David Green]

I don't know if this is just more of your EV-hater trolling, Martin, or if you're just playing dumb again. If you really can't see that the chewing-the-furniture, foaming-at-the-mouth, fact-free rant that DonDeeHippy linked to is so over the top that it's literally laughable...

Well then, "Mr. Clean Diesel", the joke is on you!

I am certainly not an EV hater or troll, but I am quite skeptical when someone tells me something I feel is is a serious engineering challenge is going to be easy. Tesla fans are cheering and think they are changing the world. I say look at BYD if you want to see changing the world, they have put their busses into service in large quantity and responsible for more reductions in C02 then the entire Tesla fleet. Bloomberg just published an article last week talking about this and how it is noticeable in the global oil supply. Thats progress...

 

[Martin Williams]

I am as sceptical of Teslas claim of 500 miles as I am about all other motor manufacturer's claims about range and mileage, but even if he is right the electric Semi is able to achieve only half what a diesel one does. Add to that a long wait to pump another couple of MegaWatts into it and I would imagine no trucking operator in his right mind would touch one with a bargepole.

As David Green observes, semis are intended for long journeys where diesels excel in terms of mileage. They are probably the worst choice for buses and local delivery use where battery power has a clear advantage.

Horses for courses!

 

[Pushmi-Pullyu]

Now Musk claims 500 miles on a charge. If we assume his average demand is one quarter of this - 200 kW -

Why in the world would you start with the maximum power demand, and then merely take a wild guess at how much less than that the average power demand would be? I started with how much fuel an average modern semi truck uses when pulling a load at highway speed, and used that as the basis for the power needed. Tesla is claiming a lower power demand than I came up with, but that is something I fully expected and predicted in several posts on the subject. I predicted the Tesla Semi Truck's power demand would be something like 15% lower than my calculations, but in fact their claim is even lower than that. My estimate was 2.4 kWh/mile; Tesla is claiming less than 2 kWh per mile. As I recall they have not given the exact figure, so at the moment I'm guessing it's only very slightly less than 2 kWh per mile.

Perhaps you would like to exhibit the calculations on your napkin and we can compare the two.

I'll post it here for archival purposes only. I'll note that my calculations assumed a ~750 mile range, but Tesla is only claiming 500 miles, so my figures will be markedly off in that regard.

I also humbly note that in the last section of my analysis I made a big mistake in talking about how fast a battery pack would wear out, claiming that the pack would have to be replaced multiple times over the lifetime of a truck. I ignored the fact that larger battery packs get cycled less frequently than smaller ones. I also significantly overestimated the expected lifetime of a semi tractor used in a commercial fleet. Further napkin math on my part (not shown here) is that the pack should, on average, last the expected average lifetime of the truck.

[See analysis in next two posts]

 

[Pushmi-Pullyu]

FOR ARCHIVAL PURPOSES ONLY: PUSHMI-PULLYU'S BEV SEMI TRUCK NAPKIN MATH ANALYSIS (AKA "NAPKIN MATH 1.0")

Please note this is a generic analysis, and does not assume the truck is built by Tesla. Altho I did use figures for Tesla's battery pack for reference purposes, my figures did not assume the truck would have the superior streamlining we can expect from Tesla.

(revised May 30, 2017)

FACTS & FIGURES

A modern diesel semi pulling a load gets 6.5 MPG; therefore uses 0.1538 gallons of diesel per mile

1 gallon of diesel contains 40.7 kWh of energy

1 gallon of diesel varies in weight between 6.85lbs. and 7.5lbs per U.S. gallon, depending on temperature. (I'm going to use the figure of 7.1 lbs/gallon)

diesel semi typical engine weight 2880 lbs

Eaton Fuller 18-speed transmission weight 738 lbs

Tesla Roadster upgrade battery pack: 70 kWh in ~10 cubic feet

standard sized semi trailer dimensions: 110" high x 96" wide, or 9.167' x 8'

DOT weight limit for a six-axle semi tractor-trailer: 80,000 lbs

Typical price of a relatively high-end new semi tractor: $150,000

Typical trucker may drive as much as 600-700 miles in a day, and can legally drive up to 11 hours per day.

* * * * *

PREMISES & ASSUMPTIONS

What we need is a BEV battery pack for our semi tractor which will allow it to pull a load for ~750 miles. This should allow the trucker to complete a daily run on one charge. We assume at the end of the run either the battery pack is swapped out for one that's charged up, or the pack is charged during the hours the trucker is sleeping. Either way, we avoid the need for fast charging and very high current.

Our hypothetical BEV semi will have an energy efficiency 2.6 times that of a diesel semi. (An EV car is about 3.5 x as energy efficient as an average gasmobile, but diesel engines are about 30-35% more efficient than gas engines.)

Therefore, our BEV semi pulling a load needs (0.1538 x 40.7 / 2.6 =) 2.4 kWh of energy to run 1 mile.

Estimated weight of a 2016 Tesla battery pack using 18650 cells: 11.5 lbs / kWh

Estimated price for a Tesla battery pack (not just the cells): $180 / kWh

* * * * *

We need to look at three limiting factors for the BEV semi tractor's large battery pack: Space, weight, and cost.

SPACE ANALYSIS

The space behind a long-haul trucker's cab, the space now devoted to storage and sleeping space, is about 4.1 feet long, at least on the diagram I looked at; I'm assuming the height and width are the same as a typical semi trailer. (At least, the dimensions should be close enough for this ballpark estimate.)

Let's use that space for the battery pack. I don't see losing this space as a problem. Since we no longer need a long nose for the diesel engine, which isn't there, we can shove the cabin forward, and leave room for the battery pack behind. The tractor now looks more like a "cab-over" tractor with an extended space behind the cabin, rather than a long-nose tractor.

So I estimate that space at 4.145 x 9.167' x 8' = 303.977 cu.ft.

An upgraded Tesla Roadster's battery pack has 70 kWh and measures ~10 cubic feet.

Assuming a similar configuration, that gives us (303.977 / 10 * 70 =) 2127.8 kWh.

At 2.4 kWh per mile, that's 886.6 miles.

This is comfortably beyond our needs of ~750 miles.

Space isn't an issue.

* * * * *

[analysis too large to fit into one post; continued below]
-

 

[Pushmi-Pullyu]

FOR ARCHIVAL PURPOSES ONLY: PUSHMI-PULLYU'S BEV SEMI TRUCK NAPKIN MATH ANALYSIS (AKA "NAPKIN MATH 1.0")

[continued]

WEIGHT ANALYSIS

Weight *is* an issue, altho perhaps not as much as it appears.

At 2.4 kWh per mile, enabling a range of 750 miles requires our BEV semi tractor to carry a (750 x 2.4 =) 1800 kWh battery pack. At an estimated 11.5 pounds per kWh, that's 20,700 lbs. We save just a bit by losing the diesel drivetrain; maybe 3000 lbs or so. We also save half the weight of the fuel*, which for a trip of 750 miles (using ~115.35 gallons) would be approximately 409.5 lbs. (We could also subtract the weight of the transmission, but then the EV motor, inverter etc. do weigh something, so let's assume that cancels out the 738 lb transmission weight.) This brings us down to an estimated ~17,300 lbs. That's 21.6% of our maximum weight limit of 80,000 lbs. And note that various State laws may reduce the maximum weight even further, depending on what States our long-range truck travels through.

Now, that's not to say this makes the idea impractical. It may well be worth sacrificing some shipping capacity as a tradeoff for lower cost per mile of moving the freight. But it does limit the market for our BEV semi a bit, or perhaps more than a bit, depending on what the customer's needs are.

*We can only deduct half the weight of the diesel fuel, because that weight will disappear over the course of the day's trip. Now that's assuming the driver starts with as much fuel as he needs for the entire day's trip, which may or may not be correct. So far as I can find by Googling, there isn't any standard size for semi tractor fuel tanks; one source says they range from 100-400 gallon capacity, and I see a reference to 2 x 150 gallons as a typical size. So then, it appears reasonable to assume ~115 gallons is carried at the start, with no stops for refueling for the entire shift.

However, the importance of the weight limit has been called into question by Piper Jaffray analyst Alex Potter, who says "Most fleets run out of space in their trailers long before they approach the 80,000-pound threshold." We think he's right on this point. The weight limit will be an issue for some fleets, but not for others, and perhaps not for most. So the weight limit apparently would not limit Tesla's market much.

* * * * *

COST ANALYSIS

Cost for the battery pack is the real issue here. And that cost is almost certainly why, for example, UPS, FedEx, Wal*Mart, and other companies with large trucking fleets have not already started switching to heavy BEV trucks.

That 1800 kWh battery pack, at $180 / kWh at the pack level, will cost an estimated $324,000. And that's Tesla's estimated cost, not price, so you can likely add another 15-25% to that. Note a reasonably high-end diesel semi tractor costs $150,000, so adding that battery pack is more than tripling the cost. With a 20% markup, it's $388,000, which is 259% of the diesel semi tractor's $150,000 price. Sure, Tesla will save some money by using an EV powertrain instead of the much more complex, and more expensive, diesel powertrain. But as a percentage of the price of that battery pack, I doubt losing the diesel engine, exhaust, etc. etc. will make much of an impact on price.

There is also the matter of battery life. A Tesla battery pack may be expected to last the life of the car, but the typical car is only driven about 5-10% of the hours in a day. Contrariwise, a long range truck is expected to be on the road as much as possible. A truck just sitting around still has to be insured, and the owner still has to pay all those fees for a heavy commercial vehicle. A truck just sitting around is losing money for its owner.

So we need to ask: Just how many times will that very expensive battery pack have to be replaced, over the lifetime of the truck? A semi truck is expected to last an average of 20 years, significantly longer than the average life of a passenger car. Will the truck save enough on fuel costs to justify the amortized cost of buying replacement packs?

That's a subject beyond the scope of this analysis.

* * * * *

ADDENDUM: CUTTING THE PROBLEM IN HALF

Several people responding to this "napkin math" analysis have pointed out that if we assume the driver only drives for half a shift, then uses either battery swap or fast recharge while eating lunch, then this will allow us to use a battery only half the size, weight, and cost. This of course allows us rather more optimistic assumptions. We're not sure how realistic it is to think that a trucker would always stop to eat lunch at a battery swap station or a BEV truck stop, but let's do the math anyway.

First, we will assume a 60% battery pack size, not 50%, because there needs to be a least a bit of flexibility in what time the driver eats lunch and how far he drives before stopping in mid-shift.

60% battery pack size weighs 12,420 lbs. Losing the weight of the diesel engine and the diesel fuel saves approx. (3000 + 204.75) ≈ 3200 lbs, totaling 9220 lbs, which reduces the 80,000 lb. carrying capacity of our hypothetical BEV semi tractor-trailer rig by 11.53%, which makes this a much more optimistic scenario!
-

 

[Pushmi-Pullyu]

I am certainly not an EV hater or troll, but I am quite skeptical when someone tells me something I feel is is a serious engineering challenge is going to be easy.

I'm guessing you're referring to Elon Musk saying that designing and building the Tesla Semi Truck was... I can't remember his exact words, but something like it was simple and easy compared to designing and building the Model 3?

Yeah, I thought that was rather over-the-top, too!

I have taken Elon to task for his hype many, many times. Sometimes it's so eye-rolling that as a Tesla fans, I find it embarrassing. Fortunately, we Tesla fans -- excuse me, Tesla "cultists" -- have plenty of very real accomplishments by Tesla to point to, and plenty of glowing reviews of its cars, some of which read like love letters -- especially for the Model S, which multiple reviews actually called "The best car ever made"!
-

 

[Martin Williams]

Why in the world would you start with the maximum power demand?

In order to estimate the size of the motors of course. Which I note you have ignored. I assumed that Musk would want the best figures possible which means pushing the motors right to the max. spec.

It's worth noting in passing that these things might need to climb much steeper hills than 1 in 20, and as they are hauling 40 tons it may not be possible to do it with a fixed ratio. Motors have better speed/torque curves than ICEs, but there are limits nevertheless. You may need a 'low gear'. What you people call a 'transmission' I think. Four of them. As the motors may be working at max spec for possibly a mile or more at low speed, it is likely they will need liquid cooling too. Big motors have bigger problems dumping heat than the small ones that you have in cars. Has Musk considered this? Nobody knows.

Hoping that real-world loads will only be a fraction of the maximum load is not really very practical. Truckers in Europe contract to carry a container usually, and the people who want stuff moved will stuff it to the gills. Fine if happens to be sheets of polystyrene foam, but if its all steel spanners, they will load it to the legal maximum. Your semi has to be designed for the worst case.

Interesting that we came up with about the same figure for battery capacity. Have you considered the power levels required to charge these things? A 2MWh battery (your figure) can be fully charged in an hour at 2MW. However this involves perhaps 20,000 volts at 100 Amps, or 10,000 volts at 200 Amps and so on. In order to supply this you will need a high voltage grid connection and a substation to house the associated breakers and transformers. A lorry park designed to accommodate a number of these things will obviously need proportionately more infrastructure. It sounds like millions of dollars to me.

I stick with my estimate of about 15 tonnes leaving 25 tonnes for the payload. I don't think any trucker is likely to find this an attractive proposition, even if Musk could wave a magic wand and install country wide charging points overnight.

 

[bwilson4web]

My understanding is there are two models with different ranges:

• ~350 mi
• ~500 mi

Bob Wilson

 

[Pushmi-Pullyu]

In order to estimate the size of the motors of course. Which I note you have ignored.

That's right. I make no pretense of my analysis being an in-depth one. As I said: Napkin math.

It's worth noting in passing that these things might need to climb much steeper hills than 1 in 20, and as they are hauling 40 tons it may not be possible to do it with a fixed ratio. Motors have better speed/torque curves than ICEs, but there are limits nevertheless.

That's possible. There have been suggestions this truck won't do well climbing steep mountain roads, and if so the Rocky Mountain region would be off-limits.

At any rate, I think it's safe to assume the Tesla Semi Truck will not have a multi-gear transmission. Will that limit its maximum grade? Well yes, but then diesel semi trucks are also limited to a maximum grade, altho it may be a different figure.

Hoping that real-world loads will only be a fraction of the maximum load is not really very practical.

Entirely incorrect. About 90% of semi loads are less than maximum weight. Most loads, by far, have space/volume rather than weight as the limit. If Tesla's market is limited to that 90%, that's not much of a restriction! The restriction on range is a much bigger limit, but even there, the majority of freight hauling runs are less than 500 miles.

Let us please remember that the Tesla Semi Truck does not have to replace 100% of diesel semi trucks on Day 1 of sales. It will be quite enough if that truck can get a firm toe in the market, and prove that BEV semi trucks can compete successfully with diesel semi trucks for over-the-road freight hauling, even if it's only on certain routes and in certain regions. As BEV tech continues to improve, so will the ability of BEV semi trucks to compete.

Interesting that we came up with about the same figure for battery capacity. Have you considered the power levels required to charge these things? A 2MWh battery (your figure) can be fully charged in an hour at 2MW.

The figures for charging a 2 MWh battery (actually, my estimate was 1.8 MWh) are rather irrelevant to the Tesla Semi Truck, since Tesla is only claiming a 500 mile range for the long-range version, not the ~750 miles I assumed in my "Napkin Math 1.0" analysis.

However this involves perhaps 20,000 volts at 100 Amps, or 10,000 volts at 200 Amps and so on. In order to supply this you will need a high voltage grid connection and a substation to house the associated breakers and transformers. A lorry park designed to accommodate a number of these things will obviously need proportionately more infrastructure. It sounds like millions of dollars to me.

Tesla has cited a price of 7¢/kWh for electricity for charging its Semi Trucks, and it's probably no coincidence that this is very slightly more than the average industrial rate for electricity in the USA. I infer that Tesla will be restricting installation of its "Megachargers", as it calls them, to industrial areas where high-power hookups are already available.

This FUD that an electrical substation will need to be located right next to every Megacharger is pretty silly. Large skyscrapers can draw up to 10 MW, and a single electrical induction furnace can draw up to 42 MW! Estimates for the draw of a Megacharger range from about 1.2 MW to 1.4 MW. It has been speculated, based on the number of holes in the plug for the Tesla Semi Truck, that it will charge at 800 volts, so that will reduce the need for large cables as compared to the 125-145 volt charging of Tesla Superchargers.

I stick with my estimate of about 15 tonnes leaving 25 tonnes for the payload.

Well, we can just add that to the growing list of subjects where you deliberately choose to ignore facts. The real world doesn't care if you believe it exists or not.
-

 

[David Green]

Man, you guys are so deep into this analysis. Way higher then my pay grade... Lets just wait and see if Tesla does some demonstration of the Semi's capabilities. On the motors, it looks to me that they are using a standard axle, and replacing the 3rd member with their drive unit, this should be the most efficient way to do that. I do not think it will be a 2 speed setup since they will likely limit speed to 60MPH as most fleet trucks already do. The battery will be much heavier then the diesel engine, transmission, driveshaft, and fuel. some things you guys are missing, are the heating/cooling of the cab, battery, air compressor for the brakes, lights, comunications, all of which run off the battery, in addition to propelling the truck. Another thing to remember, with limited chargers, the truck will never reach its full range because of the charger locations. Now on I-90 here in WA state, there are way over 100 trucks per hour passing each way, lets assume 20% are EV at some point in the future, where do they all stop, and charge? Substation? They will need to stop at Grand Coulee Dam. Tesla has a great opportunity to prove their semi on the GF! to Fremont route, why are they not running them every day in test?

 

[Pushmi-Pullyu]

The battery will be much heavier then the diesel engine, transmission, driveshaft, and fuel.

Did you actually read, or even skim thru, my analysis? I go into a lot of detail on the weight question, altho my assumption was for a rather heavier battery pack than Tesla is using. You are correct, the Tesla Semi Truck will weigh more than its diesel equivalent, altho the shorter-range version shouldn't weigh that much more.

some things you guys are missing, are the heating/cooling of the cab, battery, air compressor for the brakes, lights, comunications, all of which run off the battery, in addition to propelling the truck.

The power drain for all that -- other than the HVAC system (heating/cooling the cabin) -- is rather negligible, unless the air compressor for the trailer air brakes requires a lot of power. On EV forums, there is a lot of talk about how much the HVAC system affects range, but nobody talks about power drain from the other auxiliary power needs, because they don't have a noticeable effect on a car's range. And given a ~1 MW battery pack, the drain from HVAC will likewise be negligible, or nearly so.

Another thing to remember, with limited chargers, the truck will never reach its full range because of the charger locations.

That's a rather strange concern to raise. You could just as well say "With limited numbers of truck stops, a diesel truck will never reach its full range because of the truck stop locations."

Common sense says that trucking companies which buy Tesla Semi Trucks will have Megachargers installed where they think it will best suit their needs. So if you're thinking that the trucks will have to drive far out of their way to recharge... then think again. These Megachargers are going to be installed either where the trucks spend their hours between shifts, probably at a truck depot somewhere, or along the routes where the trucks are going to be used, for en-route charging.

Don't make the mistake of thinking Tesla is going to try to install a nationwide network of Megachargers, in an attempt to cover the entire lower 48 States, as Tesla has with its Superchargers. Remember, Tesla's customers for its Semi Truck are all trucking fleet operators, not the general public.

Now on I-90 here in WA state, there are way over 100 trucks per hour passing each way, lets assume 20% are EV at some point in the future, where do they all stop, and charge? Substation?

In the future, when there is sufficient demand, we will see dedicated truck stops for heavy BEV trucks, just as we now see dedicated truck stops for heavy diesel trucks. We can expect to see high-tension power lines going directly into BEV truck stops.

Tesla has a great opportunity to prove their semi on the GF! to Fremont route, why are they not running them every day in test?

Because with only two prototypes built, they have to use those for everything, including demos for potential customers and for publicity events. Tesla isn't going to wear out those two prototypes by using them for endurance testing. We can expect Tesla to build a testing fleet at some point, which they can test to destruction.
-

 

[David Green]

Tesla has stated they plan to start production of the semi in 2019, there is just the 2 prototypes they better get moving, there is a huge test and validation program that needs to be done before they lock in the design and plan for production (also the problem of plant location, assembly line, and cash for production). Tesla has been burning lots of diesel to show off with these prototypes and none of it is impressive to me until they actually verify the capabilities and put these trucks in action so they can be seen daily between GF1 and Fremont, and not with a diesel helping it with the trailer.

HVAC and other loads are heavier then you are figuring, and for that matter battery, and drive unit cooling. Also Tesla's lose substantial range on hills, hot or cold weather, etc... Last weekend we took a Model 3 over the mountains to our vacation cabin. We used 205 miles of indicated range in 98 miles over I-90 Snoqualamie Pass at only 75MPH, no HVAC. We could not make it 200 miles total without stopping to charge

Why do you make so many excuses for Tesla... they need to act with accountability, just like any other company. When they show a verifiable demonstration of performance I will believe it.however when I see the semi bobtail, with the matching trailer being towed by a diesel right behind... Yes, I am skeptical... as any reasonable person would be.

 

[bwilson4web]

Why do you make so many excuses for Tesla... they need to act with accountability, just like any other company. When they show a verifiable demonstration of performance I will believe it.however when I see the semi bobtail, with the matching trailer being towed by a diesel right behind... Yes, I am skeptical... as any reasonable person would be.

A life-long engineer, there is a reason we have an engineering lab to test our designs. Those who don't suffer public humiliation. But Tesla's lab is 'the real world' in their hands.

Tesla skeptics are going to grasp at every fig leaf and try to make it stick. IMHO, it is misleading because I've dealt with many low-serial number products in the past. Integration and test never ends but it does taper down. So let's see test results for higher serial number cars and trucks. In the meanwhile, patience and take a 'grain of salt.'

Bob Wilson

 

[David Green]

A life-long engineer, there is a reason we have an engineering lab to test our designs. Those who don't suffer public humiliation. But Tesla's lab is 'the real world' in their hands.

Tesla skeptics are going to grasp at every fig leaf and try to make it stick. IMHO, it is misleading because I've dealt with many low-serial number products in the past. Integration and test never ends but it does taper down. So let's see test results for higher serial number cars and trucks. In the meanwhile, patience and take a 'grain of salt.'

Bob Wilson

I am not sure what you are talking about? This conversation is about the capabilities of the Semi...

BTW, I leased one of the first 2K Chev Volt made, and never had any quality problem with it, drove it 3 years and 28K miles and not one glitch. car was super solid. My friends with original Model S have drive units replaced (Not 1, multiple) and the door handles are unreliable. The also squeak and rattle like an old ford pickup after getting some miles on them. Consumer Reports had very much the same problems in their long term testing. Thats not a fig leaf... Thats chronic reliability problems. Model S is better now, but X and 3 are experiencing quite similar reliability issues.

 

[Martin Williams]

That's right. I make no pretense of my analysis being an in-depth one. As I said: Napkin math.



That's possible. There have been suggestions this truck won't do well climbing steep mountain roads, and if so the Rocky Mountain region would be off-limits.

At any rate, I think it's safe to assume the Tesla Semi Truck will not have a multi-gear transmission. Will that limit its maximum grade? Well yes, but then diesel semi trucks are also limited to a maximum grade, altho it may be a different figure.



Entirely incorrect. About 90% of semi loads are less than maximum weight. Most loads, by far, have space/volume rather than weight as the limit. If Tesla's market is limited to that 90%, that's not much of a restriction! The restriction on range is a much bigger limit, but even there, the majority of freight hauling runs are less than 500 miles.

Let us please remember that the Tesla Semi Truck does not have to replace 100% of diesel semi trucks on Day 1 of sales. It will be quite enough if that truck can get a firm toe in the market, and prove that BEV semi trucks can compete successfully with diesel semi trucks for over-the-road freight hauling, even if it's only on certain routes and in certain regions. As BEV tech continues to improve, so will the ability of BEV semi trucks to compete.



The figures for charging a 2 MWh battery (actually, my estimate was 1.8 MWh) are rather irrelevant to the Tesla Semi Truck, since Tesla is only claiming a 500 mile range for the long-range version, not the ~750 miles I assumed in my "Napkin Math 1.0" analysis.



Tesla has cited a price of 7¢/kWh for electricity for charging its Semi Trucks, and it's probably no coincidence that this is very slightly more than the average industrial rate for electricity in the USA. I infer that Tesla will be restricting installation of its "Megachargers", as it calls them, to industrial areas where high-power hookups are already available.

This FUD that an electrical substation will need to be located right next to every Megacharger is pretty silly. Large skyscrapers can draw up to 10 MW, and a single electrical induction furnace can draw up to 42 MW! Estimates for the draw of a Megacharger range from about 1.2 MW to 1.4 MW. It has been speculated, based on the number of holes in the plug for the Tesla Semi Truck, that it will charge at 800 volts, so that will reduce the need for large cables as compared to the 125-145 volt charging of Tesla Superchargers.



Well, we can just add that to the growing list of subjects where you deliberately choose to ignore facts. The real world doesn't care if you believe it exists or not.
-

Napkins are not an excuse to ignore simple calculations which might give embarrassing results.

As to the real world loads. Musk is seriously proposing to go to market with a truck that is INFERIOR to the competition! It has restricted range, there are no charging facilities for it, steep hills are out, and it won't carry a full load. Nobody wanting to shift loads is going to sit down and work out whether to ring an electric semi operator or a diesel one which will handle whatever they throw at it. As a business plan, it has catastrophe written all over it in six foot high neon illuminated letters!

Skyscrapers taking 10MW most certainly WILL have a substation. Probably hidden somewhere in the basement. So will induction furnaces. Both will probably receive a 33 kV connection. They will both need a massively expensive transformer at the very least, in the case of the skyscraper it will probably have one transformer to go from 33kV to 1100V and further smaller substations located on machinery floors to take the voltage down to 220V. When you are talking tens of MW, you can't get away from a high voltage connection. The alternative would be copper cables as thick as your head, and horrific losses from Joule heating. To get the voltage down to something a bit safer you need a rather large transformer. Heres a 5MW oil-filled 33kVA beauty to give you an idea of the sort of thing required.

To charge a 2MW battery at 800 volts would imply high currents, by the way. To do it over 8 hours would mean a current of 312 Amps. Over four hours it would mean a current of 625 Amps, 2 hours would require 1250, and 1 hour 2,500 Amps.

All this for a hugely expensive truck that can't handle hills and wont carry much or very far!

How can it possibly fail to sell?

 

[Martin Williams]

Did you actually read, or even skim thru, my analysis? I go into a lot of detail on the weight question,

No you don't. You have not even bothered to estimate the power of the motors or their weight! Or that of the gearing requited.

You need to abandon napkins and do the job properly or not at all!

 

[David Green]

Napkins are not an excuse to ignore simple calculations which might give embarrassing results.

As to the real world loads. Musk is seriously proposing to go to market with a truck that is INFERIOR to the competition! It has restricted range, there are no charging facilities for it, steep hills are out, and it won't carry a full load. Nobody wanting to shift loads is going to sit down and work out whether to ring an electric semi operator or a diesel one which will handle whatever they throw at it. As a business plan, it has catastrophe written all over it in six foot high neon illuminated letters!

Skyscrapers taking 10MW most certainly WILL have a substation. Probably hidden somewhere in the basement. So will induction furnaces. Both will probably receive a 33 kV connection. They will both need a massively expensive transformer at the very least, in the case of the skyscraper it will probably have one transformer to go from 33kV to 1100V and further smaller substations located on machinery floors to take the voltage down to 220V. When you are talking tens of MW, you can't get away from a high voltage connection. The alternative would be copper cables as thick as your head, and horrific losses from Joule heating. To get the voltage down to something a bit safer you need a rather large transformer. Heres a 5MW oil-filled 33kVA beauty to give you an idea of the sort of thing required.

To charge a 2MW battery at 800 volts would imply high currents, by the way. To do it over 8 hours would mean a current of 312 Amps. Over four hours it would mean a current of 625 Amps, 2 hours would require 1250, and 1 hour 2,500 Amps.

All this for a hugely expensive truck that can't handle hills and wont carry much or very far!

How can it possibly fail to sell?

But Elon said... Haha!

 

[DonDeeHippy]

I've thought that if the semi's replace grocery trucks going from the warehouse of a city, to the suburbs
in a few big countries, even that would be 100000's of vehicles and wouldn't need to carry huge weights and be relatively a small range.
The market is huge for full size semi's, even if u discount long range haulers.

 

[David Green]

I've thought that if the semi's replace grocery trucks going from the warehouse of a city, to the suburbs
in a few big countries, even that would be 100000's of vehicles and wouldn't need to carry huge weights and be relatively a small range.
The market is huge for full size semi's, even if u discount long range haulers.

That is exactly what I think the market is for those trucks, although I question the 100K... but 20 to 30K a year might be a reasonable number. Big fleets lease their trucks a certain number each year so they would slowly buy in. We will see over the next few years, as Tesla builds a few and puts them in their own fleet. I think Tesla needs 100 or so themselves to replace the diesels around their factories. How much power is it again to charge 100 of these each night?