Tesla is aiming to K.O. Freightliner

But even this has its limitations. Just because they are the same weight, it does not mean that can do the same job. Or just because both can go 400 miles with an empty load does not mean they both perform the same when fully loaded. EVs have regenerative braking, which will help make the battery pack a little smaller. Driving conditions including wind conditions will affect performance. Terrain will affect performance.

The most ideal test would be too have two identical trailers with the same payload, driven over the same distance, under the same conditions (essentially both are following the same route and starting from point A and reaching point B at the same time and carrying identical loads). Then you could calculate what would been the minimum battery weight and EV power-train that would have got you from point A to point B with zero charge left. Similarly you can get the data for the diesel truck.

Again, I am sure that there labs and companies that can simulate exactly what I have laid out without actually having to drive it. So the data the @R P wants is out there. It may not be publicly available. Unfortunately, I have not seen a simple formula that can be used to compare EV trucks against ICE trucks. There are just too many variables. None of the back of the napkin calculations show much.

 

You shouldn't be so presumptuous. You can blindly speculate all you want about Tesla and what they will do, but I am trying to get some solid data first that I can build on. Battery size to fuel weight ratio at least would give me a better idea of what size battery (minimum) would be required. I know what it is for my Kona compared to the gas equivalent, but not really sure about Tesla and if there is an industry accepted measure (weight to kV maybe?) and how it varies with size. In the case of Hyundai, it seems to get better with size, but not so with Tesla if the Model S results are any indication.

Size of battery will affect charging infrastructure (and cost) for semis.

 

For those who are interested (@bwilson4web you might be), here is a Govt developed simulator which provides the information and comparison, if you have the patience to fill in the information. There is pre-filled data for a variety of cars including ICEs, PHEVs and BEVs, so for those you can change parameters and run. They have data for Class 8 trucks but only for Diesel and Hydrogen Fuel Cells. They have no EV data for trucks. But if you can get some of the data, you can input it and create your vehicle. And if you want to compare the Huyndai EV against the Tesla, this tool will allow you to do it with prefilled data

One of these days I will get down to understanding it and playing around with it but not today.

https://www.nrel.gov/transportation/fastsim-download-confirmed.html

It is available in Python and Excell version. You can download it for free and run some simulations if you are so inclined. I know @R P is looking for something very simple, and this may not interest him. However, if someone is motivated enough, one might be able to find some of the answers @R P using this simulator.

 

Good point. But now we get into the realm where it's simply impossible to do a direct comparison between an ICEV and a BEV. BEVs need to be designed around the battery pack; a physically larger battery pack means the entire vehicle needs to be larger, which affects the basic shape, size, and cost of the vehicle. With a diesel semi tractor, if you need more range you can just add on some larger aftermarket fuel tanks, or an additional 3rd tank somewhere.

That's going to have very little impact on long-distance semi freight hauling. Most of the driving will be at a steady freeway speed, with little braking involved.

Indeed. There has been concern expressed about how the Tesla Semi Truck will do in going over the Colorado Rocky mountains, on a coast-to-coast run. This is one place where simulations aren't really adequate, and we would need actual testing under real-world use conditions.

I'm sure there are not. There are too many variables involved here. Computer simulations are good for certain things, but for something like this, they can only yield an approximation. George and Keith have their own computer models they use, but those can only yield estimates as good as their guesses.

As computer programmers say about what happens when you feed bad or questionable data into a computer program: "Garbage in, garbage out".

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If you're trying to remove yourself from any contribution to the discussion, that's certainly going a long way toward that goal. This isn't the first time you've chosen to make a personal attack on me or someone else in the midst of an otherwise interesting discussion, either.

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@Pushmi-Pullyu actually there are some very sophisticated simulators available as I just found it as I was curious. You can google it. There is so much work in simulating real life operating conditions for vehicles and a lot of AV driving is being simulated in addition to real life testing.

There are companies selling such software that can be used vehicle manufacturers Most of them are propriety. Again, if people are buying the products, it must have some use.

I just posted a simple simulator, where there is a tab for actual vs your simulation.

And having developed sophisticated simulations, no it it is not the final word, but it can provide very useful insights.

 

When I did my own "napkin math" estimate for a BEV semi truck (not necessarily a Tesla one) back in the day, I used the industry average for semi truck fuel use, about 6 MPG, and compared the energy contained in that to a Tesla battery pack. I came up with slightly more than 2 kWh per mile used; Tesla claims slightly less than 2 kWh per mile.

But trying to estimate the weight of the battery pack... that's pretty much a shot in the dark. We can figure the weight of a Model 3 battery pack per kWh, but the architecture for a much larger battery pack is going to be different.

Different people doing their own "napkin math" analyses have come up with different figures for how many kWh the Long Range Tesla Semi Truck needs, and thus different weights for the battery pack. R P, you're asking for an industry standard which simply doesn't exist.

I gave you links to the most comprehensive "napkin math" estimate I've seen on the subject, and in response you made a completely unprompted personal attack on me. I'll keep that in mind for future discussions. The phrase "Pearls before swine" comes to mind.

 

Yes that is one use case. If as you pointed out, you are going over mountain passes with steep curves (Like over the Rockies or the Sierra Nevada etc.), the use case is different. Not all driving is on freeways, some trucks have to spend time on surface streets. In real life you will have a combination of various scenarios (highway driving, street driving, narrow and winding roads etc) and good tests will add a combination of them. You cannot test every use case, but there are several use cases that favor EVs and regenerative braking.

 

I'm a computer programmer. I know exactly what "GIGO", or "Garbage In, Garbage Out" means. As I think I've already said, a computer simulation is only as good as the data fed into it. Nobody except Tesla knows exactly the kWh battery capacity of the Long Range Tesla Semi Truck, and nobody except perhaps a few trucking companies that Tesla has loaned their prototypes to has real-world data on how many kWh per mile the truck consumes when pulling a load in real-world conditions. Presumably they did that under NDA, so the data isn't being publicly disclosed.

Keith and George have created their own simulator for Tesla cars and trucks. I was startled to learn they use the same simulator for both cars and heavy trucks, and that's one reason why I consider their analyses to be rather speculative. But that's their choice.

If you don't like the "napkin math" estimates that others have done, then by all means do your own. Having done one myself back in the day, I feel no urge to repeat the effort. As I said, George and Keith's analysis a deeper dive than I did, despite all the hours of time I spent researching the subject and doing calculations. I think Electrek published a different "napkin math", and perhaps also Clean Technica? It's possible that one of those came closer to what the real-world figures will turn out to be, but there's no way of knowing until people actually start using Tesla's (or some other company's) BEV semi tractor for real-world hauling of tractor-trailer loads, and publicly reports those figures.

 

I have developed or lead development of complicated computer systems. So yes I know what GIGO is. You are right that many input variables are not going to be shared. Tesla is not give its information to anyone else or vice versa. So many companies often buy competitor vehicles to do testing and help develop comparative simulations.

I also agree that there is no substitute for real world testing. However, simulation is a tool to help improve and optimize quickly. A simulator combined with AI system keeps improving the model. Will it mimic a 100% real life? NO. Can it provide you insights that avoid may be 50% of the real life testing? Yes, I see many companies using simulation and AI to reduce testing. I have a friend who works on vehicle dynamics for FCA and he would come down to Arizona where they would do testing (on many testing ranges we have) every year. He has now reduced his frequency of visits as he told me that they are able to simulate a lot of the testing in the labs and yes, he still comes down but not often at all. And he told me that using the data, they keep improving their model.

It is not either or. Today it is both, simulation and real life testing.

Here is a link to article (written by the sales person for that company so it biased, where it talks about simulation of EVs)

https://www.todaysmotorvehicles.com/article/simulating-electric-vehicle-performance/

Some other articles
https://www.researchgate.net/publication/273341988_Comparing_a_driving_simulator_to_the_real_road_regarding_distracted_driving_speed

https://mashable.com/2017/07/14/autonomous-driving-real-cars-simulations/

http://www.rfpro.com/about/


And as you may have realized, in this discussion I have not go into napkin maths, as it is simply a guessing game.

 

Yes, but for long-distance trucking, the amount of stop-and-go driving and/or driving at less than freeway speed is going to be a very small percentage of the total miles. And for shorter routes, for local deliveries and for freight runs that are short enough that the truck will return to the fleet's storage lot at the end of the day, the Standard Range Tesla Semi Truck will be adequate, the battery pack will be smaller and lighter, which makes the use case so different that questions like kW per mile and the weight of the battery pack become largely irrelevant. With a smaller pack, the BEV semi truck should weigh less than some long-nose diesel semi trucks, so weight isn't really important.

For freight hauling runs of 250 miles or less, the amount of stop-and-go driving, or driving at less than freeway speeds, may well become a significant percentage of the trip. Thus, trying to estimate an average use case won't be very helpful. The fleet operator must use the right vehicle for the right route, and for shorter runs there may well be cases where it makes sense to use a BEV semi truck, and other cases where it doesn't.

Keep in mind that when it comes to choosing which trucks to buy and run, the fleet operator is mainly interested in the long-term per-mile cost of running a tractor-trailer rig. We couldn't answer that question even if we knew exactly what the specs of the Tesla Semi Truck are.

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Yes, absolutely computer simulations can be very helpful in narrowing down choices, eliminating the ones which obviously are not going to yield a desirable result. So yes, computer simulations can be quite useful. I understand they are helping a great deal in the fields of pharmaceuticals, material science and bio-engineering (where protein computer models are quite useful).

Perhaps I don't understand what your objective is here. I thought you were trying to get some figures for direct comparison between a diesel semi tractor and the Tesla Semi Truck, on the basis of weight, range, and energy use. Now it reads more like you're trying to develop some sort of spreadsheet or computer model which would estimate different use cases based on different driving conditions. The latter would be pretty ambitious.

If I've come across as a wet blanket on this subject, then I apologize. I certainly do encourage you to develop your own use case, and I'd be interested to see what you come up with when you're finished, if you're willing to share.

But demanding specific figures on this subject isn't going to get you anywhere, because the only people who have those figures are not going to publicly disclose them. The best we can do is estimates based on the scant publicly available data.

And realistically, I think we need to consider the very real possibility that the figures Tesla has given us so far are based on only their own internal estimates of how much battery tech is going to improve between now and whenever the Semi Truck goes into production. Hopefully Tesla will be giving us some info regarding that subject in the upcoming "Battery Tech and Powertrain Investor's Day" presentation, which I think is scheduled to happen sometime this quarter (1st quarter 2020).

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I have not demanded any specific figures. I have made no back of napkin calculations in this thread. I clearly have stated that I do not have any data that I can stand by. I have discussed hypothetical methods to do the comparison. I have provided some data and a simulator, but have left to anyone who wants to actually use the to make any calculations. I have personally not used the little data I have.

I repeat that I have not seen any real data and this real data may come out only after the product comes out. So I am not to going to guess.

 

There are many areas where the Interstates travel over undulating terrain, a series of small hills typically changing +/- 300 ft. Diesels struggle up the hill and typically use a 'Jake Brake' or coast down the hills. For example, I-65 between Birmingham AL and Nashville, TN. Traveling on cruise control, the Tesla or BMW smoothly transition between EV power and EV regeneration. But diesel trucks have no such advantage.

I often hear diesels using engine and smelling mechanical braking to modulate their speed going downhill. The potential energy gained climbing a hill is wasted as hot brakes and compression heat loss. This increases the wear on the diesel which needs more maintenance. In contrast, a BEV truck will reclaim a significant part of this energy. This has a practical effect on the Tesla BEV truck.

The higher power of the Tesla truck allows it to accelerate faster than traditional trucks. But the same power that moves the Tesla truck becomes the regenerative braking needed to descend a hill. In contrast, a diesel truck needs the minimum power to climb a hill, in the 'truck lane', and no more.

Bob Wilson