[brian_]

The weight comparisons between the Tesla Semi and diesel trucks in online discussions can be very frustrating. Almost no one makes a rational comparison, which means

1. accounting for all major components, meaning
   • battery, motors, gearboxes, and supporting equipment (charger, cooling, etc) for the EV
   • fuel, engine, transmission, driveline, and supporting equipment (exhaust, cooling, etc) for the diesel
2. comparing similar configurations, which means tandem-drive Class 8 day cabs
3. assuming comparable options (e.g. everyone uses aluminum wheels now; if one has wide-base single tires then other should, too)
4. using the same trailer, if considering trailer weight

For a very rough example:

• EV with 1 MWh battery: 5,000 kg (11,000 lb) battery + motors, gearboxes, and supporting equipment (charger, cooling, etc)
• Diesel: 2,000 kg engine + 300 kg fuel + transmission, driveline, and supporting equipment (exhaust, cooling, etc)

If the diesel's transmission weighs about the same as the EV's motors and gearing, and the diesel's exhaust system (with DPF and SCR) weighs about the same as the EV's charger, etc, and both have cooling systems, then the EV is 2,700 kg (a few tons) heavier; there is a huge uncertainty in that value.

Tesla likely compares their day cab to a typical diesel sleeper cab to conclude that the difference is only one ton of extra weight allowed by U.S. federal highway standards. It helps to get this deception accepted that the 500-mile (larger battery) version of the Semi has a cab extension that looks like (but is not) a sleeper.

The delivery video shows (at 16:47, if I recall correctly) a much-discussed example load behind a Tesla Semi, consisting of eleven roughly 10-foot concrete road dividers (called "jersey barriers"). A much-quoted estimate assumes 4,000 pounds per barrier (that's at the light end - many are substantially heavier) plus a 10,000 pound flat-deck trailer for a total of 54,000 pounds. Subtract that from the 81,000 pounds stated for a different Semi with a different trailer (!) and you get a 27,000 pound tare weight for the Semi tractor. There are so many rough estimates and questionable assumptions that this is very approximate, and more likely a high limit than an expected value (because of the light barriers and implausibly light trailer). That's higher than needed (based on component weights), but only about a ton heavier than the heavy end of sleeper-equipped diesel highway tractors.

 

[remy_martian]

This carries an extreme anti-Musk sentiment and is hypercynical, but has some interesting points of view, nonetheless:

For the unfamiliar, he's been calling out Musk for years on his channel.

edit: He does go through some of the weight analysis Brian posted while I was posting this one.

 

[Electric Land Cruiser]

The Tesla delivery event was certainly successful with the target audience, convincing those who were inclined to favourable opinions - and largely unfamiliar with heavy truck design and operation - that a miracle had indeed been delivered. Of course, it had not... but they did deliver a perfectly good battery-electric truck.

Is anyone here saying it's supposed to be anything more than a perfectly good battery electric truck? People are saying it's worse, definitely....

 

[electro wrks]

Here's my Semi weight analysis from 2017, when the Semi was first introduced:

"The Tesla Semi main designer, Jerome Guillen, said in a recent presentation in Europe that the Tesla truck weighs no more than a diesel truck. If you take a modern diesel semi (also designed by a team lead by Jerome Guillen when he worked for Daimler/ Freightliner) and pull the engine:DD16® | Freightliner Trucks ; transmission:https://freightliner.com/demand-detroit/detroit-dt12-transmission/ say ~1000# of tanks, radiators, non-fuel fluids, and other ICE related equipment; and 200gal(~1400#) of fuel. You save ~6000# (if I haven't left any thing out). So how much energy will ~6000#(~2700kg) of batteries give us? "

I wonder how close to the finished product I got.

 

[remy_martian]

I bet the electric air compressor for the brakes on an EV semi is pushing 200 pounds.

The entire engine bay of the eCascadia I saw about a month ago was completely filled with stuff, despite the humongous inverter boxes, motors, and batteries being mounted elsewhere.

Everything seemed to be mounted on heavy steel weldments. The truck builders understand longevity and everything was built like a brick poophouse on that truck - Tesla is using high-strung car motors, and I'm guessing with none of that margining. The cab is aluminum, so what else is for lightweighting? Aluminum cracks under fatigue...

I lost faith in Tesla's truck sensibilities after the Cybertruck abomination. How do you carry bales of hay with it or even load it from the side?

(my pic):

 

[brian_]

Is anyone here saying it's supposed to be anything more than a perfectly good battery electric truck? People are saying it's worse, definitely....

Here? No. But here the participants in the discussion are generally knowledgeable about the reality of battery-electric vehicles.
The Youtube and Facebook (and presumably Twitter, if that system is still operating ) comments have the usual Musk disciples spouting nonsense.

 

[brian_]

Here's my Semi weight analysis from 2017, when the Semi was first introduced:

"The Tesla Semi main designer, Jerome Guillen, said in a recent presentation in Europe that the Tesla truck weighs no more than a diesel truck. If you take a modern diesel semi (also designed by a team lead by Jerome Guillen when he worked for Daimler/ Freightliner) and pull the engine:DD16® | Freightliner Trucks ; transmission:https://freightliner.com/demand-detroit/detroit-dt12-transmission/ say ~1000# of tanks, radiators, non-fuel fluids, and other ICE related equipment; and 200gal(~1400#) of fuel. You save ~6000# (if I haven't left any thing out). So how much energy will ~6000#(~2700kg) of batteries give us? "

I wonder how close to the finished product I got.

With what is likely 11,000 pounds (5,000 kg) of battery, and the pesky little details of electric motors, reduction gearboxes, inverters, etc. the "500 mile" Tesla Semi will be substantially heavier than a truly comparable diesel truck, because that "~6000#(~2700kg) of batteries" isn't enough. But we are all still wondering, because Tesla won't say what the Semi weighs.

With only 60% of that amount of battery, the "300 mile" Tesla Semi would have about 6,600 pounds (3,000 kg) of battery, and come closer to the "same weight", but still needs the 2,000 pound exemption that U.S. federal rules allow.

The biggest available diesel engine may be a reasonable choice if the basis of comparison is power, but few if any buyers would spec that engine for an ordinary highway tractor at only 80,000 gross weight; this is minor factor, since the more appropriate DD13 is only 20% lighter. Also, there's no need to burden the diesel with 200 gallons of fuel when it only needs 75 gallons for 500 mile range.

 

[electro wrks]

With what is likely 11,000 pounds (5,000 kg) of battery, and the pesky little details of electric motors, reduction gearboxes, inverters, etc. the "500 mile" Tesla Semi will be substantially heavier than a truly comparable diesel truck, because that "~6000#(~2700kg) of batteries" isn't enough. But we are all still wondering, because Tesla won't say what the Semi weighs.

At the time of this analysis in 2017, some of us were thinking the battery energy density would have to improve by a factor of ~2X for the 500 mile range Semi to have the same weight as its diesel counterpart. It will be interesting to see what the actual weight is.

 

[brian_]

That first half of the "Thunderf00t" video was an enormous waste of time, raising nothing other than the obvious (the product is late, the truck's tare weight is not stated, and FSD is a farce), and the weight analysis is laughably wrong. He is correct that the trucking industry does not care about acceleration or grade-climbing speed the way Tesla seems to, and that autonomous operation is still not ready. At the end he returns to the obvious - that range is limited and charging takes time, and that while Tesla has stalled real truck manufacturers have put battery-electric trucks in production for appropriate applications. In my opinion, the nonsense drowns out the intelligence.

In the demonstration drive the Tesla Semi doesn't pass anything, simply because the driver is maintaining a relatively constant and moderate speed, as it must for sufficient range.

Check the comment by Doggfite on that YouTube video for an explanation of the multiple errors in Thunderf00t's weight nonsense. For a simpler check, note the barriers are most of the length of the vehicle passing the trucks - it's not a Smart ForTwo so those are not 2 metre (6 foot) barriers on the truck.

 

[cricketo]

Fun Tesla Semi video here :

Tesla on LinkedIn: Our engineers tested Semi in a variety of harsh conditions to maximize… | 345 comments

Our engineers tested Semi in a variety of harsh conditions to maximize reliability & durability. Join us on the Vehicle Test Team. https://lnkd.in/gu2NPePh | 345 comments on LinkedIn

www.linkedin.com

 

[electro wrks]

Here's one recent estimate of the weight and battery capacity of the Semi: https://www.teslarati.com/wp-conten...Shot-2022-12-29-at-9.01.43-AM-2048x1142-1.jpg
If correct, this is in line with what some of us figured in 2017, as outlined in posts 44 and 48. It's too bad that Tesla was not able to keep the tractor weight down(again, if this is correct) to that of its diesel powered counterparts, as claimed at the time of the Semi's introduction. The Semi still appears to be as good or better than its competitors. This weight factor will only improve over time, with better batteries. Overall, it remains to be seen how well this radical shift in technology will be accepted into the very competitive trucking industry.

 

[Electric Land Cruiser]

That is actually lighter than a lot of people predicted for the Tesla semi. A lot of people thought it would be 30k or more. Some diesel semi tractors are 20-25k lbs also.

Lastly the weight is less important I read a stat that based on data 90% of trucks on the roads in the USA are 73,000 or less. They are not always fully loaded which was my previous suspicion. Of course it won't replace every semi but definitely a good amount.

 

[remy_martian]

It's just a matter of time before Musk gets accused of unfair trade practices (battery dumping) by his competitors, if those price estimates are correct.

There's no magic in this stuff that cuts prices in half...

 

[brian_]

It's too bad that Tesla was not able to keep the tractor weight down(again, if this is correct) to that of its diesel powered counterparts, as claimed at the time of the Semi's introduction. The Semi still appears to be as good or better than its competitors.

I don't remember the details of the original fantasy, but Tesla has recently claimed that the Semi would be heavier than "a diesel truck" by only the extra 2,000 pounds allowed under U.S. federal rules for highway vehicles, giving them the same payload. Now, what is "a diesel truck" and what are "its competitors"?

Some diesel semi tractors are 20-25k lbs also.

Yes, but what tractors? Day cabs with only 80,000 pound gross weight ratings? Not likely. We probably have lots of highway tractors here at that tare (curb, empty) weight, but they have sleeper cabs and are equipped and used for Super B-Train or dual 53-foot trailer service, with 63,500 kg (140,000 lb) combination weight rating. Comparing the Tesla Semi day cab to a diesel tractor with a large sleeper, or to a tractor capable of hauling much higher loads, doesn't make sense.

Heavy truck manufacturers generally do not publish the weights of their products online, even in downloadable brochures and guides, presumably because the weight can vary so much with the many configuration options offered. Tesla doesn't share any real information at all. This makes objective comparison extremely difficult. It would be interesting if there were a real journalist anywhere in the automotive world who would assemble a Tesla Semi some truly comparable tractors, and run them all through scales to get real information. That's not going to happen any time soon, but we can hope that a Pepsi driver takes a Semi through a scale without a trailer and shares the weight.

 

[brian_]

Here's one recent estimate of the weight and battery capacity of the Semi: https://www.teslarati.com/wp-conten...Shot-2022-12-29-at-9.01.43-AM-2048x1142-1.jpg

That appears to be from the Teslarati "news" item Tesla Semi outperforms rivals in specification analysis, and repeats material published by NextBigFuture as Shopping Guide for Electric Semi Trucks [Prices, Weights and Payload].
That author provides no sources. We know that Tesla does not provide any weight data, so those values are guesses; I wonder if they're all guesses?

I note that there are two Freightliner eCascadia configurations listed with the same battery capacity, essentially the same range, the same price... and yet two significantly different weights (one 16% or 3050 pounds heavier). The heavier eCascadia has less power and lower GCWR, suggesting that it might be a straight truck rather than a tractor; if so, the comparison table is nearly useless. I applaud the effort, but there isn't enough information here to seriously compare anything.

I also note that the Tesla Semi 300 and the lighter variant of the Freightliner eCascadia are quite comparable in weight (the Tesla has 16% higher guessed battery capacity and 9% higher guessed weight). This isn't surprising; it also doesn't demonstrate any Tesla advantage. The claimed range of the Tesla is much higher in this pair, but all range values are of little value with no comparable basis for range determination.

 

[brian_]

If better, more up to date info becomes available, by all means people should post it.

I agree; I will certainly share anything that I find which I think is valuable.

For now, this is what is available. Should I take it down because it is not perfect?

That's not what I intended at all. I appreciate the link to the material which is available, although I wish the originator had provided sources or explanations of the numbers, which would have given them more value. I do think it is important to distinguish data from estimates.

 

[brian_]

Lastly the weight is less important I read a stat that based on data 90% of trucks on the roads in the USA are 73,000 or less. They are not always fully loaded which was my previous suspicion. Of course it won't replace every semi but definitely a good amount.

While mass is important to energy consumption, I agree that legal truck weight limits are not as major a limiting factor as many people think. Trucks are often limited by the bulk (volume) of the load rather than the weight (called a "cube-out" situation), or simply to the size of what needs to be moved as one shipment.

Suiting the truck to the application is important. While the Teslarati article ignores this (because their purpose is to rationalize a declaration of Tesla superiority), the NextBigFuture article which is the source of all of their information copies and links to a rational discussion from Freightliner: Moving the Electric Needle: Smart Ways to Use Electric Trucks

Most rational EV applications in trucking are in anything but long-haul, and most are for straight trucks rather than tractors pulling semi-trailers. Tesla has only addressed the tractor-trailer application, presumably either because they think that it is the most impressive to their fans, or because they don't want to deal with upfitters (the companies that add second-unit bodies and equipment to base trucks to make them useful).

 

[remy_martian]

Meanwhile, Ian Wright, one of Tesla's founders (pre-Musk), went the other way and founded a company that builds electric trucks (not semis) at Wrightspeed.

 

[electro wrks]

That author provides no sources. We know that Tesla does not provide any weight data, so those values are guesses; I wonder if they're all guesses?

Or, they might not be. Maybe the author called around to the electric truck manufacturers, with a reporter's verve, asking them to confirm or deny performance specs of their trucks. Or, maybe he told them he was going to publish some arbitrarily unflattering figures for the specs, forcing them to cough-up the actual specs.

 

[brian_]

Or, they might not be. Maybe the author called around to the electric truck manufacturers, with a reporter's verve, asking them to confirm or deny performance specs of their trucks. Or, maybe he told them he was going to publish some arbitrarily unflattering figures for the specs, forcing them to cough-up the actual specs.

So we agree - we have no idea where these numbers came from. It would be good to know.
I did not claim that I had better information; I only distinguished between these numbers and real data.