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Earlier promotional material showed two cab lengths, suggesting a shorter day cab and a longer sleeper cab. As the video shows, the long version is still only a day cab. The interior space ends at the back of the doors, which are well short of the back of the cab; that means that the extra length is a stack of battery above the frame... just like a BYD Class 8 day cab tractor, but with a nicer fairing over it.

Longer-range hydrogen-fueled fuel cell trucks have been shown with a similar behind-the-cab energy storage feature (tanks in that case).

Long haul without a sleeper? It can work (motels exist for a reason) but it's somewhat limiting.
 

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Discussion Starter · #22 ·
If the battery capacity is not sufficient for a full driving day (and 500 miles is not sufficient in long haul) then fast charging at short breaks (lunch?) is required. That is expensive infrastructure, and even if it is built out it is much more expensive to use than slower charging at corporate facilities.
Federal law requires minimum 30 min break for 8 hours of driving. On many routes 500mi in 8 hours won't be even possible due to truck speed limits, scales, and traffic when going through populated areas. I believe with sufficient infra 500mi range can be basically unlimited range if every quick food/bathroom stop results in 10-15 minute charge top off. But the cargo capacity is a better question, perhaps 300mi range + better charging would be a better option.
 

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Discussion Starter · #23 ·
No, you get the extra 200 miles, at 2 kWh/mile, with 400 kWh more battery. the Tesla Semi is very conventional: it has an normal heavy truck frame, axles, suspension, brakes, and general cab configuration (the goofy central-seat cab is an unimportant distinction). There's no evidence of "designing it as an EV from the start" about the fundamental design.


Good try, but way off. Musk has confirmed that the Semi's consumption when loaded to about 80,000 pounds is about 2 kWh/mile - that's six times Model X consumption, not three times. And there's nothing wrong with that, given the relative sizes of the vehicles and their shapes.


A realistic battery weight:
500 miles * 2 kWh/mile * 5 kg/kWh = 5,000 kg (5 tonnes)
You can't replace the engine and transmission with just motors - you need the reduction gearboxes for the electric motors as well. A better comparison is to assume that the electric drive units weigh about as much as the diesel truck's transmission, and that diesel-related accessories are comparable to EV-related accessories, so it's a matter of replacing two tonnes of engine and exhaust system with 5 tonnes of battery, for a net 3 tonne increase... plus or minus a substantial margin for error.

I agree that the weight penalty is manageable for many applications... but not all.
They have called out the exceptional aerodynamics, which is a component of that. Daimler has a conventionally shaped cab, and there is likely a penalty for that. In a diesel they could get away with that by making the fuel tank bigger, not so much in an EV.
 

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No...you are still dealing with the drag from the abrupt termination at the back of the trailer and its open wheels.

The Daimler trucks have fairings - they have been competing in fuel economy for decades. "Just burn more diesel" sends customers to the competition.

You must be peeing a lot with all that Musk-aide you've been guzzling 😂 Aero on the front of the truck is lipstick on a pig... that and the centered driver is more crap Musk has stolen from the covers of his 1950's Mechanix Illustrated collection.
 

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The only thing different is they have a master bullshitter at the helm, and, as CEO and major stockholder, he has the power to BS well beyond what any marketing exec would get approved to do.

Nothing they are doing is any different than anyone else, now.

The Maxwell dry cell tech in the 4680 was their trump card, and they can't seem to get the things to yield with all the cracking when they roll the cell. The "tabless design" was supposed to fix that (you also probably fell for the "superior cooling" sleight of hand Musk stated as to why they did tabless to detract from yield concerns, yet those "cooling" tabs sit on a chunk of ABS plastic in the Monro teardown).

Nothing is different. Both full self driving and the dry cells are still, eternally, two years away.
 

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It does 2kwh/mi and has 1000kwh. Not sure what the controversy is. They posted a video of the 500 mile drive on their youtube channel. It looks like it's limited to 55mph the whole way and sticks to the right lane so it's a realistic run.

They can sell them for $200k because they aren't just going to sell a truck. They are going to sell the whole charging infrastructure shebang with on-site storage and likely a decade or two contract with recurring costs and fees.

 

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The economics were predicated on the 4680 cell.

The Semi was delayed by the 4680 cell, as was Cybertruck.

The range was always cited as 300-500 miles. Nobody is disputing it went 500 miles at gross weight. What's in question is the PAYLOAD (the moneymaker).

Volvo, Daimler, and others were eating Tesla's lunch for the past couple of years with EV semi offerings. BYD now has one as well.

The Semi's battery was reworked to use the more expensive 2170 cells.

Tesla's in trouble if they don't get their act together on the 4680. All they have is a "me too" that's late to the party against companies with established service centers. There is no magic in any of this. Daimler has a wind tunnel here in Portland -- as if aero was some kind of innovation that gives Tesla a leg up? Puhleez.

The charger is nothing special - they are and have been available from others...in fact, it HAS to be standardized at loading docks, which is when regional trucks charge.

Tesla's only calling card is self-driving, which doesn't work yet and is no better than Daimler's.

They are severely late to the party. They are running on pricing (now forward pricing) based on 4680. Either they raise the price, or the 4680 goes in. Again, that special sauce ain't there, so this is just a "me too" product with a mouthpiece CEO who's been caught lying and stretching truth as a habit.
 

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They can sell them for $200k because they aren't just going to sell a truck. They are going to sell the whole charging infrastructure shebang with on-site storage and likely a decade or two contract with recurring costs and fees.
Perhaps. Of course, we have no idea what they are actually selling them for, since they only have one customer so far, with a negotiated price which is likely confidential.
 

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The most interesting bit of information that I have seen from this great unveiling and the associated demonstration trip appeared in an article from electrek:
Watch Tesla Semi do something Bill Gates said wasn’t possible
It presumably came from one of Tesla's videos, but I haven't bothered to watch all the way through them, and it shows the battery state of charge over the famous 500-mile drive:

The state of charge drops in a very nice straight line, at 0.186 %SoC per mile; the steep climbs cause dips below that line, but lower consumption and regeneration on the complementary descents bring it right back to that line. The conclusion is that - at least for this vehicle driven this way (relatively steady speed) - grades don't matter to energy consumption per distance travelled. Note that the trip starts and finishes at essentially sea level.

Google Map route
 

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There was a time on internet forums where if you participated in the discussion without having viewed the source material you would be chastised by others.

Now people freely proclaim their ignorance about not having viewed the source material and jumping in anyway.

Yes that graph was shown along with others. It's not surprising to anyone with EV experience; what goes up must come down. Hills along the way don't really hurt the overall range. The most important thing is the beginning elevation compared to ending elevation.
 

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There was a time when "source material" wasn't both infinite in volume and nearly devoid of value. There was a time when corporations released rational information, instead of videos of chatter, so that a graph didn't need to be extracted from a video. And I linked to the source of the graph on which I was commenting, which is a reputable publication; as usual, my contribution here is far more rigorously backed up and clearly presented than most of this forum's content, so I don't see the need for the shot.

I did later skim through the official Tesla video and confirmed that it is the source of the graph, as expected.

The "up-and-down equals level" effect is not so clearly true. Cycling energy through the powertrain and battery is far from perfectly efficient, so the net effect is not a wash - the result here is good, but that can't be assumed. The efficiency of any powertrain varies with load, so the average efficiency of high power on the climb and low power on the descent can't be assumed to be the same as constant power for the same time - in this case switching between three motors on the way up and one motor on the way down is probably very helpful.
 

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There was a time when "source material" wasn't both infinite in volume and nearly devoid of value. There was a time when corporations released rational information, instead of videos of chatter, so that a graph didn't need to be extracted from a video. And I linked to the source of the graph on which I was commenting, which is a reputable publication; as usual, my contribution here is far more rigorously backed up and clearly presented than most of this forum's content, so I don't see the need for the shot.

I did later skim through the official Tesla video and confirmed that it is the source of the graph, as expected.
Yes, devoid of value :geek: Luckily for you Tesla posted an edited down 35 minute version on their Youtube channel.

I don't really know anything about semis but here are a couple things that popped out to me from watching the Tesla event myself and then reading this thread:

-The Tesla semi uses a 1000+ volt architecture while the other EV semis use lower. Daimler comes close at "800-900." More voltage is an efficiency advantage, especially on a vehicle like this that will pull massive amps on a regular basis.

-Tesla designed a semi from the ground up whereas the legacy brands adapted their existing engineering that is really still 60s technology for the most part. They still have "fuel tanks" on the sides under the steel cab with fiberglass wind deflector for instance. There are benefits to doing it both ways. A cheap EV truck to move smaller trailers around a yard or make local deliveries might not need to be super advanced but obviously due to the technical challenges a long-haul EV semi does need to be super advanced.

-It's a 4WD truck standard with advanced traction control. Your comments about it being bad in winter conditions is pretty telling. In the event, they did spend some time talking about winter conditions and how the semi has advanced traction and stability control to prevent jackknifing and other things. They said "it drives like a Tesla" because Teslas are famed for their winter performance and traction control. The open differential matters less with traction control using the normal disc brakes and single motor modulating, the rear axle should be able to torque vector and use disc brakes, both axles can be driven independently. Also the boost motors are able to connect and start providing torque before the cruise motor reaches full power when the driver puts their foot down as stated in the event. The 4WD should be able to seamlessly activate whenever needed or the driver can just turn it on for snow. Now heater performance and range in winter, that's another thing entirely.

-The brakes barely ever get warm due to regen, as to be expected but that is a massive benefit to truckers not having to let their brakes cool or check them. They have to pull over and get out of the truck and inspect etc. I've seen semis with their brakes literally on fire coming down I-70. A few years ago a run away semi killed several people after he lost control coming down from 9000ft into rush hour traffic. Not having to shift through the gears and change axle ratios etc is a massive improvement for driver fatigue as well. Much less brake pad dust in the environment longer service intervals.

-Yes, any EV truck will suffer a max payload penalty. But most trucks are not running at their max capacity or anywhere close. I don't think you can fit enough potato chips in a semi to hit 80k. Maybe if it's full of Pepsi. The Semi has an estimated 11,000 lbs of battery which definitely takes a chunk out of payload but in a lot of cases that doesn't matter.

-Advances in technology like going to super single rear tires instead of dualies and aluminum trailers can tip the scale back towards an EV. For instance the Kenworth EV semi uses dualies and the Tesla semi uses big singles. The big single tires can save 1000 lbs by themselves. It's the sum of the parts coming together that make the end result significantly better than each small change can do on it's own.

-Average diesel semi engine/trans is 5000lbs

EV Semi +11,000lbs battery
-1000lbs aluminum wheels/tires
-2000 aluminum trailer
-1000lbs aluminum cab
= 7,000lbs net

EV truck 2,000lbs gross weight bonus = 5,000lbs net. Payload capacity unaffected. Obviously these are napkin level calculations for the purpose of discussion.

-Battery tech at launch is usually updated quickly by Tesla. I'm not a fanboy by any means but their track record shows. They upgrade batteries in first gen Model S and Roadsters for a really great price.

-In the delivery event livestream they showed their semi supercharger infrastructure. They spent several minutes showing acres of backup battery storage to deliver to Pepsi and Frito-Lay for their locations. It looked like Elon had batteries coming out of his ears he has so many.

-Elon said that Tesla will guarantee lifetime 7 cent/kwh Semi Supercharging and they will go 1,000,000 miles. The youtube channel below calculated that would be $180,000 for electricity vs. $700,000+ of diesel at current prices for 1,000,000 miles. It's unclear if the battery itself will go 1mn miles or just the chassis and drivetrain. I doubt the battery can come close but I bet it lasts about the same amount of time as an engine needs before it's time for an overhaul.


Like I said I'm no Tesla fanboy and do not like their marketing vaporware and anti-right to repair stuff like Rich Rebuilds is famous for but Tesla's track record is pretty good otherwise. I think EV makes more sense in a lot of cases for larger vehicles than small ones simply because a larger vehicle can carry more batteries. I also hate sitting behind two semis trying to pass eachother for 5 minutes on the interstate and I hate the smell of diesel.

The "up-and-down equals level" effect is not so clearly true. Cycling energy through the powertrain and battery is far from perfectly efficient, so the net effect is not a wash - the result here is good, but that can't be assumed. The efficiency of any powertrain varies with load, so the average efficiency of high power on the climb and low power on the descent can't be assumed to be the same as constant power for the same time - in this case switching between three motors on the way up and one motor on the way down is probably very helpful.
There are a couple of advantages because of air resistance on a large vehicle like a semi it's better to drive at a slower speed and regen more vs. on a smaller EV to allow the car to accelerate with gravity and regen less. If there was no aero drag or safety issue it would be most efficient to just let the vehicle coast all the way down hills as fast as possible and then slow as you go up the next hill or use the speed to carry you are far as possible til you need to add power. Speed limits, traffic, and aero drag tip the scales towards driving 55 and regening. The 1000 volts also likely helps a lot in the losses of cycling the battery. Either way I know from my time commuting in an EV that the hills and ups and downs didn't matter anywhere near as much as the starting and ending elevations.
 

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Let's review what you wrote, with my notes at ###

-The Tesla semi uses a 1000+ volt architecture while the other EV semis use lower. Daimler comes close at "800-900." More voltage is an efficiency advantage, especially on a vehicle like this that will pull massive amps on a regular basis.

### The motors used in the Semi are the exact same ones used in the Plaid. Not even half the voltage your "1000+ volt architecture" argument makes. So, all that efficiency argument you are making is BS. They are likely "doubling series, halving parallel" in a 900V charging configuration. Daimler, I believe, uses an actual 800V motor, so your argument of who has the more efficient driveline gets reversed.

-Tesla designed a semi from the ground up whereas the legacy brands adapted their existing engineering that is really still 60s technology for the most part. They still have "fuel tanks" on the sides under the steel cab with fiberglass wind deflector for instance. There are benefits to doing it both ways. A cheap EV truck to move smaller trailers around a yard or make local deliveries might not need to be super advanced but obviously due to the technical challenges a long-haul EV semi does need to be super advanced.

### Tesla designed nothing from the ground up anymore than anyone else did. Everyone uses a motorized axle. Everone uses a 'glass body on truck frame. Everyone uses underslung battery packs. Arguably, Tesla puts their batteries behind the cab to get that extra range...ever notice the armored rack behind a semi's cab? It's to keep a load shift from spearing the cab...genius place to put a battery that lights up when you puncture it. CG-wise, the tractor will also be more prone to flipping in curves.

-It's a 4WD truck standard with advanced traction control.

### this is called a "full tandem" configuration, which has been available in your great grandfather's day.

Your comments about it being bad in winter conditions is pretty telling. In the event, they did spend some time talking about winter conditions and how the semi has advanced traction and stability control to prevent jackknifing and other things.

### Which is pure Musk bullshit. A jackknife occurs when the trailer tries to pass the tractor. The only thing traction control will do it align the trajectory of the tractor with the trailer to force the tractor into a wall or over a cliff.

They said "it drives like a Tesla" because Teslas are famed for their winter performance and traction control. The open differential matters less with traction control using the normal disc brakes and single motor modulating, the rear axle should be able to torque vector and use disc brakes, both axles can be driven independently.

###more nonsense. If the goal was real traction control, they would not have cheaped out on deleting that second motor on the single motor axle. This is typical for Tesla - they cheap out in stupid areas, imo.

Also the boost motors are able to connect and start providing torque before the cruise motor reaches full power when the driver puts their foot down as stated in the event. The 4WD should be able to seamlessly activate whenever needed or the driver can just turn it on for snow. Now heater performance and range in winter, that's another thing entirely.

### there's no sleeper, so warming the cabin is a piece of cake compared to even a sedan with a lot of glass that includes its roof.

-The brakes barely ever get warm due to regen, as to be expected but that is a massive benefit to truckers not having to let their brakes cool or check them.

### you have ZERO regen for the top 100kWh of charge. Zero. The regen argument applies for Volvo, Daimler, BYD, and others' trucks as well. Meh.

They have to pull over and get out of the truck and inspect etc. I've seen semis with their brakes literally on fire coming down I-70. A few years ago a run away semi killed several people after he lost control coming down from 9000ft into rush hour traffic. Not having to shift through the gears and change axle ratios etc is a massive improvement for driver fatigue as well. Much less brake pad dust in the environment longer service intervals.

### there is no low gear at the top of SoC. There is no low gear. You HAVE to ride the brakes down the hill in that case. And stop to cool them down before they fade to zero.

-Yes, any EV truck will suffer a max payload penalty. But most trucks are not running at their max capacity or anywhere close. I don't think you can fit enough potato chips in a semi to hit 80k. Maybe if it's full of Pepsi. The Semi has an estimated 11,000 lbs of battery which definitely takes a chunk out of payload but in a lot of cases that doesn't matter.

### Tesla has carefully chosen its battle. You are absolutely correct about potato chips, styrofoam MacDonalds cups, etc as loads. Again, applies to all electric semis

-Advances in technology like going to super single rear tires instead of dualies and aluminum trailers can tip the scale back towards an EV.

### Tech that's been in use in Europe and ROW forever.

For instance the Kenworth EV semi uses dualies and the Tesla semi uses big singles. The big single tires can save 1000 lbs by themselves. It's the sum of the parts coming together that make the end result significantly better than each small change can do on it's own.

### Tires and wheels are build options for the other EV semis

-Average diesel semi engine/trans is 5000lbs

EV Semi +11,000lbs battery
-1000lbs aluminum wheels/tires
-2000 aluminum trailer
-1000lbs aluminum cab
= 7,000lbs net

### you don't get to pick the trailer, especially when much of the freight out there is modular and uses sea containers

EV truck 2,000lbs gross weight bonus = 5,000lbs net. Payload capacity unaffected. Obviously these are napkin level calculations for the purpose of discussion.

-Battery tech at launch is usually updated quickly by Tesla.

###battery tech was supposed to be the cheaper 4680. Look for a price increase or profuse bleeding of cash if they hold pricing.

I'm not a fanboy by any means but their track record shows. They upgrade batteries in first gen Model S and Roadsters for a really great price.

-In the delivery event livestream they showed their semi supercharger infrastructure. They spent several minutes showing acres of backup battery storage to deliver to Pepsi and Frito-Lay for their locations. It looked like Elon had batteries coming out of his ears he has so many.

### Batteries WAS a Tesla strength. This will change in 2-3 years. Tesla had NO batteries for the semi -- they had to redesign the pack to use more expensive Model 3 batteries. Chargers from BYD and Proterra have been out there for a while using reverse pantographs, which don't seem possible with Tesla's cab design.

-Elon said that Tesla will guarantee lifetime 7 cent/kwh Semi Supercharging and they will go 1,000,000 miles.

### Musk has made many promises on the cars he has taken back. He's a carny, a pitchman, a barker.

The youtube channel below calculated that would be $180,000 for electricity vs. $700,000+ of diesel at current prices for 1,000,000 miles. It's unclear if the battery itself will go 1mn miles or just the chassis and drivetrain. I doubt the battery can come close but I bet it lasts about the same amount of time as an engine needs before it's time for an overhaul.

###If the motors are geared down as I suspect, using the 20,000 RPM Plaid motor was a mistake for longevity, imo. Tesla was renowned for not getting more than 100k miles out of Model S drive units. Semis run long days, many miles, and a diesel is low RPM...which is why it lasts longer.

###So there you go - I've intentionally taken the counterpoint here to get the collective opinion to settle to reality, vs fanboy and shareholder hype. There are great attributes common to all EV semi trucks. There are also silly, car-guy, design choices that were made, much like was done with Cybertruck. Yes, Semi will haul bags of potato chips 500 miles...and getting speared in your truck cab by a Dorito is unlikely.

### I've been busy lately, but I think there's a Youtube video on this that's topical. I'll screen it first and if worthwhile, will reference it in this thread.
 

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... If there was no aero drag or safety issue it would be most efficient to just let the vehicle coast all the way down hills as fast as possible and then slow as you go up the next hill or use the speed to carry you are far as possible til you need to add power. Speed limits, traffic, and aero drag tip the scales towards driving 55 and regening.
I agree. Regen to control speed on descent is the practical approach; it incurs an efficiency loss, but still works out well.
 

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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.
 

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I found the three-motor powertrain choice interesting. Like Rivian (which has disconnects for the rear axle shafts of the R1T), Tesla found that running one highly loaded motor was adequate for highway cruise, and more efficient than running three or four similar motors, each lightly loaded. The efficiency difference with load isn't surprising (you can see it in the efficiency map of any motor), but I find it interesting that just one motor is enough, and that the efficiency difference is enough to justify the cost and complication of the disconnects. By the way, at least in smaller sizes, those disconnects are common off-the-shelf components.

The original (five years ago) publicly displayed prototype used dual motors on each axle, but the gear reduction ratio was different between the axles, so they had apparently intended even then to operate on the motors in only one axle under some conditions. I don't recall seeing any references to physical disconnects at that point, but they may have been included. The disconnects may also have been added after Rivian demonstrated their application.

The conventional equivalent is that trucks with tandem rear axles have been routinely available in three configurations:
  • 6X2: only one rear axle (generally the leading one) is driven; the other one is a "pusher" (ahead of driven axle) or "tag" behind driven axle) and may have single tires (or smaller super-singles if the drive axle has wide-base singles). Tag and pusher axles can have castering wheels (self-steering). A common intercity coach (bus) is a 6X2 with tag axle.
  • 6X2/4: only one rear axle (the leading one) is driven; the other one is engaged only when required for traction. Since the two axles will "fight" causing destructive and energy-consuming tire scrubbed the second axle is left disengaged as much as possible. This is functionally like a traditional part-time 4WD system, in which one axle (traditionally the front) is engaged only off-road. The Tesla Semi is essentially doing this, but due to the separate motors for each axle scrub is not an issue.
  • 6X4 with inter-axle differential: both axles are driven at all times, by the two outputs of an inter-axle differential which is mounted on the leading axle. The inter-axle differential may be lockable, just as the centre differential in a 4X4 may be lockable. An electric truck with motors on each axle is equivalent, but doesn't need a mechanical inter-axle differential or lock because the motors can run at different speeds and can be controlled to run at the same speed.
Some current heavy battery-electric trucks (such as those from Volvo/Mack) use a motor (or two on a shared transmission) mounted to the frame and conventional mechanically driven axles. Others (such as those from PACCAR) use axle-mounted motors like Tesla. I have not seen any indication of their motor management scheme, meaning how many motors they use under what conditions.
 
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