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

[Martin Williams]

The bigger the battery pack you have, the more cooling becomes important. (Small packs lose heat easily into the environment. Bigger ones need a lot more active cooling) I would expect the overall energy density of the pack to stay at about the same - around 150 Wh/kg.

 

[David Green]

David,
the axle is a 2 speed; it has different ratios for each motor (2 of them). I suspect each has a disconnect clutch so the truck can run on one or both depending on the driving demands of the moment. Its clever, and as efficient as you can imagine is possible.

The kwh energy use for a ICE semi is about 5 kwh for auxiliaries (air compressor, engine cooling fan, alternator, steering pump, HVAC; this number does not include the water or oil pump for the engine or gearbox) - see ICCT data on EU trucks - same engines and gearboxes on the majority of US trucks.

Mark my words, the 300 mile Tesla Semi will weigh about the same as a conventional truck. You have about 6k lbs of ICE components that go away, and what you replace it with weighs close to the same (mostly batteries; the motors/inverters and power electronics don't weigh much). Folks keep over-estimating the weight of the battery packs in the Semi because they are using 2012 Model S packs as a benchmark, and not accounting for improvements in energy density that are going to reduce the weight per battery pack.

OK, but since I own 3 Kenworth T-800 trucks you will have to trust me on some things. There are 2 kinds of trucks, mine use the heaviest steel frames, axles, drop axles and cary 80 gallons of fuel which is good for about 750 miles empty or 400 miles loaded to 105,500Lb GCVW At that weight 34.5 tons is payload riding on 8 axles. We use Cummins ISX engines at 565HP and around 2000 lb ft torque, and 18 speed fuller transmissions. This is a standard issue dump truck in our area. We take our trucks loaded to capacity off road, and around construction sites, they are tough workhorses. What Tesla is building is a light weight daycab. This is a totally different animal, a comparable fleet like walmart or pepsi, uses a very light weight aluminum frame, a 300 to 350Hp engine, 10 speed transmission, and the lightest axles. These trucks are intended for the highway only, and pulling a max 80K GCVW on 5 axles. Your weight estimation is about accurate for the drivetrain or our trucks, but you are not even close for the daycab fleet style. and you have completely discounted all of the additional weight of the drive units on the BEV truck for HVAC, Air Compressor, circulating cooling water etc. On our trucks all of those drive off 2 belts, of course there is 2 for redundancy. Tesla also showed their semi with super single tires, which save weight, but if you get a flat, you are stopped right there, no limping to an optimal place for a tire change. This is the reason most fleets do not use super singles.


I think BEV semi's will work, they must as BYD already sells short range versions that I have seen on some government sites, but we sometimes work up in the mountains, and when you pull Snoqualamie pass loaded you sit at 2000Lb ft of torque for 20 minutes+, how many Tesla's have you seen that can stay at max power for more then 10 seconds, let alone 20 minutes without generating too much heat? What about in heat over 100 degrees which is common in Eastern WA, Oregon, Idaho, Montana, Utah, Nevada, S E Cal, Arizona, Texas... ETC... So you show me the Tesla carry the payload, up hills in the heat or cold, and have durability? I think this is why the semi truck is on the back burner now, too many equations that need to be figured, out before it is going to be cost effective to have a BEV semi.

 

[Pushmi-Pullyu]

Folks keep over-estimating the weight of the battery packs in the Semi because they are using 2012 Model S packs as a benchmark, and not accounting for improvements in energy density that are going to reduce the weight per battery pack.

That's a fair cop. Unfortunately there does not seem to be any consensus on the energy density of battery packs using Panasonic's new 2170 cells. The arguments rage on the Tesla Motors forum, with one camp insisting there is no significant improvement over Panasonic's current 18650 cells (which, as you say, do represent some improvement over the 2012 version used when the Model S was new), and the other camp insisting there is something like a 35% improvement in energy density over current batteries. I'll wait to see some actual third-party tests of an actual Model 3 battery pack before I come to a conclusion on the subject.

Doodlebug, based on your deep-dive posts on this subject, I'd love to see your napkin math analysis! It looks to me like you're much better informed than I am. However, I personally would never base an analysis on something like the Navistar testing you cite. I used industry averages for a very good reason: Because those numbers represent what actual commercial fleets are getting, not some ideal test case which may not represent real-world driving by real trucks in commercial use.

​

 

[Pushmi-Pullyu]

Tesla also showed their semi with super single tires, which save weight, but if you get a flat, you are stopped right there, no limping to an optimal place for a tire change. This is the reason most fleets do not use super singles.

That's a criticism I've read elsewhere, too. Use of super single tires may be "a bridge too far" in Tesla attempting to maximize energy efficiency. I doubt trucking fleets are suddenly going to decide that super singles work better for them just because the truck is powered by electricity rather than diesel.

...how many Tesla's have you seen that can stay at max power for more then 10 seconds, let alone 20 minutes without generating too much heat?...

"10 seconds", really? I see you're back to your Tesla bashing. Too bad, because you had some useful comments in there before that.

The prototype 2020 Tesla Roadster shown at the Tesla Semi Truck reveal event was reported to have operated for some 45 minutes doing repeated acceleration demos, obviously without overheating or going into reduced-power mode. So Tesla has demonstrated that it can build a vehicle that has no problem with sustained rapid acceleration. Of course, that doesn't in any way prove that Tesla will make the cooling system in its Semi Truck as robust as the one in the 2020 Roadster; it merely proves that Tesla can do that for an expensive vehicle when it has a powerful incentive to do so. The economic case for building a Semi Truck is quite different than building a limited production expensive "supercar" like the 2020 Roadster.

Let us please remember that Tesla is aiming its Semi Truck at commercial trucking fleets which are going to give the trucks extensive testing before they commit to buying them in large numbers. What Tesla claims but isn't true isn't going to help them in any way in selling the Semi Truck; it's just going to give Tesla a black eye in the view of commercial trucking operators. And Tesla is fully aware of that fact. So if Tesla says that its truck, when loaded, can do a sustained climb up a 5% grade significantly faster than a loaded diesel semi truck, then the truck had darn well better be able to do that. If it can only do that for a few seconds or a few minutes, then that will become obvious as fleets test the truck.

There are many comments by industry watchers claiming that the Tesla Semi Truck won't perform well in mountainous regions, such as climbing over the Rockies on a coast-to-coast run. I don't know how they came to that conclusion; I'd like to learn more about that particular subject.

​

 

[Doodlebug]

OK, but since I own 3 Kenworth T-800 trucks you will have to trust me on some things. There are 2 kinds of trucks, mine use the heaviest steel frames, axles, drop axles and cary 80 gallons of fuel which is good for about 750 miles empty or 400 miles loaded to 105,500Lb GCVW At that weight 34.5 tons is payload riding on 8 axles. We use Cummins ISX engines at 565HP and around 2000 lb ft torque, and 18 speed fuller transmissions. This is a standard issue dump truck in our area. We take our trucks loaded to capacity off road, and around construction sites, they are tough workhorses. What Tesla is building is a light weight daycab. This is a totally different animal, a comparable fleet like walmart or pepsi, uses a very light weight aluminum frame, a 300 to 350Hp engine, 10 speed transmission, and the lightest axles. These trucks are intended for the highway only, and pulling a max 80K GCVW on 5 axles. Your weight estimation is about accurate for the drivetrain or our trucks, but you are not even close for the daycab fleet style. and you have completely discounted all of the additional weight of the drive units on the BEV truck for HVAC, Air Compressor, circulating cooling water etc. On our trucks all of those drive off 2 belts, of course there is 2 for redundancy. Tesla also showed their semi with super single tires, which save weight, but if you get a flat, you are stopped right there, no limping to an optimal place for a tire change. This is the reason most fleets do not use super singles.


I think BEV semi's will work, they must as BYD already sells short range versions that I have seen on some government sites, but we sometimes work up in the mountains, and when you pull Snoqualamie pass loaded you sit at 2000Lb ft of torque for 20 minutes+, how many Tesla's have you seen that can stay at max power for more then 10 seconds, let alone 20 minutes without generating too much heat? What about in heat over 100 degrees which is common in Eastern WA, Oregon, Idaho, Montana, Utah, Nevada, S E Cal, Arizona, Texas... ETC... So you show me the Tesla carry the payload, up hills in the heat or cold, and have durability? I think this is why the semi truck is on the back burner now, too many equations that need to be figured, out before it is going to be cost effective to have a BEV semi.

David,
wrt weight, simple: I am comparing apples-to-apples.
Most informed folks are very aware that trucks meet specialist requirements, so no-one is trying to compare a Semi against a truck of the spec that you are talking about. Tesla isn't building dump trucks. The Semi should be compared against other daycab semis.
The lightest comparable truck I've been able to find was a KW daycab that came in at 16,032 lbs (dealer advertised weight, spec'd for lightness). Fueled-up that's around 16,700 lbs. On average they are heavier, many significantly so.
Personally I did a bottom-up weight analysis based on public information I dug up all over the internet, including copies of KW dealer quotes to customers that detail the exact weight additions (or subtractions of various items). (Starting weight of a T880 is 15,236 lbs BTW BEFORE they start adding components - its in the quote). A Paccar MX13 is 2,600 lbs dry, for example (included in the quoted starting weight). An RT-18 is 716 lbs. KW AG400 weighs 820 lbs.
On a slightly different point, based on the 2016 NACFE report 44% of progressive fleets are already using super singles. Since those are the sort of on-highway fleets that might entertain an electric truck, I think that's a reasonable comparison point. For on-highway trucks, probably we'll see a lot more super singles in the future. In CA you see a lot of trailers with super singles also. But I understand why you don't run them.
In short, I'm not discounting anything. I'm not the discounting type.
For example, when I'm running a comparison I don't worry about HVAC and air compressors; both kind of trucks have them, so there's not a material difference in weight (unless you want to fuss over the extra weight of an electric motor to drive an 8 KW air compressor or 3 KW a/c unit, which isn't material on a 17,000 lb baseline; but you can look-up the WABCO spec sheet on e-compressors online; btw a Bosch EHPS weighs only 25 lbs).
Its a bit hard to guess the incremental weight of the electric axles: there's room to argue there. But the motors themselves don't weigh all that much.
However, all the uncertainty is in the weight of the battery packs - that's the big unknown.

Also, from your previous post, did you see that Volvo have launched 2 electric trucks in Europe? They both have 2 speed gearboxes. You can't say that Volvo don't know what they are up to (check out the FH750s running 175 tonnes in the Outback).
BTW, my first experience with Volvo was in 1980; in those days they were streets ahead of anyone else.

Respectfully
Doodlebug

 

[David Green]

David,
wrt weight, simple: I am comparing apples-to-apples.
Most informed folks are very aware that trucks meet specialist requirements, so no-one is trying to compare a Semi against a truck of the spec that you are talking about. Tesla isn't building dump trucks. The Semi should be compared against other daycab semis.
The lightest comparable truck I've been able to find was a KW daycab that came in at 16,032 lbs (dealer advertised weight, spec'd for lightness). Fueled-up that's around 16,700 lbs. On average they are heavier, many significantly so.
Personally I did a bottom-up weight analysis based on public information I dug up all over the internet, including copies of KW dealer quotes to customers that detail the exact weight additions (or subtractions of various items). (Starting weight of a T880 is 15,236 lbs BTW BEFORE they start adding components - its in the quote). A Paccar MX13 is 2,600 lbs dry, for example (included in the quoted starting weight). An RT-18 is 716 lbs. KW AG400 weighs 820 lbs.
On a slightly different point, based on the 2016 NACFE report 44% of progressive fleets are already using super singles. Since those are the sort of on-highway fleets that might entertain an electric truck, I think that's a reasonable comparison point. For on-highway trucks, probably we'll see a lot more super singles in the future. In CA you see a lot of trailers with super singles also. But I understand why you don't run them.
In short, I'm not discounting anything. I'm not the discounting type.
For example, when I'm running a comparison I don't worry about HVAC and air compressors; both kind of trucks have them, so there's not a material difference in weight (unless you want to fuss over the extra weight of an electric motor to drive an 8 KW air compressor or 3 KW a/c unit, which isn't material on a 17,000 lb baseline; but you can look-up the WABCO spec sheet on e-compressors online; btw a Bosch EHPS weighs only 25 lbs).
Its a bit hard to guess the incremental weight of the electric axles: there's room to argue there. But the motors themselves don't weigh all that much.
However, all the uncertainty is in the weight of the battery packs - that's the big unknown.

Also, from your previous post, did you see that Volvo have launched 2 electric trucks in Europe? They both have 2 speed gearboxes. You can't say that Volvo don't know what they are up to (check out the FH750s running 175 tonnes in the Outback).
BTW, my first experience with Volvo was in 1980; in those days they were streets ahead of anyone else.

Respectfully
Doodlebug

 

[Doodlebug]

That's a fair cop. Unfortunately there does not seem to be any consensus on the energy density of battery packs using Panasonic's new 2170 cells. The arguments rage on the Tesla Motors forum, with one camp insisting there is no significant improvement over Panasonic's current 18650 cells (which, as you say, do represent some improvement over the 2012 version used when the Model S was new), and the other camp insisting there is something like a 35% improvement in energy density over current batteries. I'll wait to see some actual third-party tests of an actual Model 3 battery pack before I come to a conclusion on the subject.

Doodlebug, based on your deep-dive posts on this subject, I'd love to see your napkin math analysis! It looks to me like you're much better informed than I am. However, I personally would never base an analysis on something like the Navistar testing you cite. I used industry averages for a very good reason: Because those numbers represent what actual commercial fleets are getting, not some ideal test case which may not represent real-world driving by real trucks in commercial use.

​

Pushmi,
just check out the Navistar test data for yourself before deciding - its a comparison test against FL, Volvo, KW rather than a solo test:
https://www.internationaltrucks.com...cks/spotlight/fuel-economy/lta26_wp-06-vf.pdf
Their data gels quite well with other test road data I've been seeing for 2018 trucks.

I think the key thing is that fuel economy of new trucks has improved quite a bit in the past few years. 2016 NACFE report states: "This research concludes that these fleets are operating their latest vehicles in a range of 7.8 to 9.0 miles per gallon."
Their baseline is 6.3 mpg for a BAU fleet, which is probably closer to the numbers you are thinking of. But that's not what the best fleets are getting. BTW the NACFE sample includes folks like UPS and Ryder, i.e. the sort of actual commercial fleets you are referring to. And also the sort of progressive fleets that in some cases have ordered the Semi already.

BTW, see my post for David Green for more data on weights, etc. I won't repeat it here.

Regarding battery pack weights, I agree that everyone will have to wait and see. However, if there's no progress on energy density since 2012 it would be a bit surprising since it would buck industry long term trends. Also, the weight of the pack itself is a factor. I'm betting that since there are 8 or 12 of them on the Semi, Tesla has recognized that minimizing pack weight is a good way of getting the weight of the truck lower, since weight is such an obvious issue.

w/regards...

 

[David Green]

David,
wrt weight, simple: I am comparing apples-to-apples.
Most informed folks are very aware that trucks meet specialist requirements, so no-one is trying to compare a Semi against a truck of the spec that you are talking about. Tesla isn't building dump trucks. The Semi should be compared against other daycab semis.
The lightest comparable truck I've been able to find was a KW daycab that came in at 16,032 lbs (dealer advertised weight, spec'd for lightness). Fueled-up that's around 16,700 lbs. On average they are heavier, many significantly so.
Personally I did a bottom-up weight analysis based on public information I dug up all over the internet, including copies of KW dealer quotes to customers that detail the exact weight additions (or subtractions of various items). (Starting weight of a T880 is 15,236 lbs BTW BEFORE they start adding components - its in the quote). A Paccar MX13 is 2,600 lbs dry, for example (included in the quoted starting weight). An RT-18 is 716 lbs. KW AG400 weighs 820 lbs.
On a slightly different point, based on the 2016 NACFE report 44% of progressive fleets are already using super singles. Since those are the sort of on-highway fleets that might entertain an electric truck, I think that's a reasonable comparison point. For on-highway trucks, probably we'll see a lot more super singles in the future. In CA you see a lot of trailers with super singles also. But I understand why you don't run them.
In short, I'm not discounting anything. I'm not the discounting type.
For example, when I'm running a comparison I don't worry about HVAC and air compressors; both kind of trucks have them, so there's not a material difference in weight (unless you want to fuss over the extra weight of an electric motor to drive an 8 KW air compressor or 3 KW a/c unit, which isn't material on a 17,000 lb baseline; but you can look-up the WABCO spec sheet on e-compressors online; btw a Bosch EHPS weighs only 25 lbs).
Its a bit hard to guess the incremental weight of the electric axles: there's room to argue there. But the motors themselves don't weigh all that much.
However, all the uncertainty is in the weight of the battery packs - that's the big unknown.

Also, from your previous post, did you see that Volvo have launched 2 electric trucks in Europe? They both have 2 speed gearboxes. You can't say that Volvo don't know what they are up to (check out the FH750s running 175 tonnes in the Outback).
BTW, my first experience with Volvo was in 1980; in those days they were streets ahead of anyone else.

Respectfully
Doodlebug

Haha! Yes I know what Tesla is going for. When you talk to lots of these folks here on the forum and they will tell you that the Tesla Semi is going to replace all the trucks, I have to try to explain to them that there are missions that BEV can do very well, and other missions BEV trucks are not well suited. For us, our mission creates a vehicle with high ground clearance no cladding on the lower parts of the truck (because it gets torn off the first time you go through some mud on a construction site) heavy loads on bumpy roads.

For a daycab, I think the Kenworth T680 (lighter then T-880, and more aerodynamic) is what most companies buy for the highway, and they usually use the MX11, Or ISX 13 engines (Fleet operators always go for lower power, better fuel economy, and less wear on parts), both are about 2k lbs. All up you can get a 680 with 5th wheel, mud flaps, and rear duals (no super singles, although that would save more weight 180Lbs) at 14950lbs, and that will run 80K GCVW for a million miles. When you compare the weight, the Cummins engine is 2050 lbs, and I think the driveshaft, and exhaust weight is about what the Tesla style drive units weight, looking at the Tesla Semi, they looked to have Navistar axle housings, with the motors installed into the 3rd members. This with all the controls will be much heavier that just a differential which looking at Tesla's design I assume the ring and pinion are still in there. Then you add the cooling for these drive units, inverters, and battery packs, and I think you are going to need pretty close to the conventional cooling system. Remember diesel waste heat goes 80% out the exhaust, and 20% to the radiator, which also is your winter heat source. Then add the weight of the inverters, and high voltage wiring, All the electric accessory drives, and I think you get to a point where you have 2000 to 2500 lbs removed before battery pack, and no redundancy on air compressor, power steering, interior heat pump, etc. I think you need at lease 600 KWH for 300 miles (which real world will be 200 miles) and industrial level cooling on the battery pack because of conditions we discussed in the previous post. My guess is that truck is 22k all up, so there went 7000 lbs of payload, times 2 trailers a day average. Then you figure the most expensive part of trucking... drivers, they are not going to want to make less per hour to drive a BEV semi, and they cost WAY more then the fuel. My drivers now make 75K a year and that is before OT and benefits.

I think there is a reason the Semi seems to be back burnered, and is not hauling between GF1 and Fremont every day.

 

[Martin Williams]

Regarding the energy density of 2170 and 18650 cells, you might be well advised to look at the energy density of the Model 3 battery pack. It is within spitting distance of 150Wh/kg. Any increase in the energy of the cells is due to their greater volume, not better performance from the technology. It's about the same.

And more than likely to remain there for the foreseeable future, despite many amazing 'breakthroughs' and 'advancements' which never seem to appear in the real world.

 

[Pushmi-Pullyu]

Pushmi,
just check out the Navistar test data for yourself before deciding - its a comparison test against FL, Volvo, KW rather than a solo test:
https://www.internationaltrucks.com...cks/spotlight/fuel-economy/lta26_wp-06-vf.pdf
Their data gels quite well with other test road data I've been seeing for 2018 trucks.

Well, clearly you are better informed about this subject than I am, so perhaps this is a case of me arguing with someone who knows considerably more than I do about a subject. That certainly annoys me greatly when it happens to me, and perhaps I'm guilty of the same thing here. If so, then mea culpa.

Anyway, I certainly am interested in learning more about this subject, so I am reading your posts with interest, even if I'm somewhat skeptical that any outsider can really figure out exactly how Tesla has designed and built its Semi Truck.

Regarding battery pack weights, I agree that everyone will have to wait and see. However, if there's no progress on energy density since 2012 it would be a bit surprising since it would buck industry long term trends. Also, the weight of the pack itself is a factor. I'm betting that since there are 8 or 12 of them on the Semi, Tesla has recognized that minimizing pack weight is a good way of getting the weight of the truck lower, since weight is such an obvious issue.

I hope nothing I said suggested that Tesla/Panasonic are using batteries that have no improvement in energy density since 2012! It's just that when I read people claiming that Tesla/Panasonic's new 2170 cells have "35% better energy density" or even "50% energy density", then I have to wonder what they're comparing them against. I can certainly believe 35% better energy density since 2012. That would be only very slightly better than the overall trend of approx. 5% improvement per year. A 50% improvement is harder to believe, especially with so many people on the Tesla Motors Club forum insisting there isn't any significant improvement in energy density as compared to the 18650 cells which Tesla is using in the Model S and Model X.

Furthermore, nothing that Elon Musk or J.B. Straubel have said recently -- within the past year or so -- would lead me to the conclusion that the 2170 cells represent a significant energy density improvement (and thus lower weight) over the 18650 cells. (A slight improvement, yes, due to improvements in the geometry; but I'm very skeptical there is a significant improvement in energy density.) There are some comments from both of them on a conference call from a couple of years ago indicating an improvement in battery chemistry, but I see no reason to conclude that this same improvement isn't now in the 18650 cells. Note the newer 100 kWh packs for the MS/MX represent a newer design than the older MS/MX packs. There was some talk of an improved cooling system, so I can easily believe whatever new chemistry Panasonic is using was incorporated into 18650 cells going into the new MS/MX packs at that time.

Now, at the pack level, it may indeed be possible to shave some weight for the Semi Truck. Especially in the pack casing, which for the Model S/X is part of the structural integrity, helping to stiffen the car. If multiple packs are stacked into the Semi Truck in order to reach the ~800-1000 kWh or so that it needs, then there's no reason to have such very strong cases for the batteries. It might even be possible to use lightweight plastic cases, altho that might represent a safety concern in case of accident. It might also be possible to shave some weight on the cooling system; for example, using one or two large pumps to circulate the coolant rather than separate pumps for each individual section of the battery pack.

​

 

[Pushmi-Pullyu]

And more than likely to remain there for the foreseeable future, despite many amazing 'breakthroughs' and 'advancements' which never seem to appear in the real world.

There isn't any rational reason to pay any attention at all to what you have to say on this subject, Martin. You are willfully ignorant on the subject. So far as I'm concerned, it's a settled point that li-ion battery cell chemistry continues to improve every year, a verified fact which you refuse to accept as reality, an "inconvenient fact" contrary to your anti-BEV agenda.

To quote the recent conference call with Tesla investors:

Rod Lache - Deutsche Bank Securities, Inc.

Okay. Thanks for that. And just secondly, your comments in your letter on the advances in batteries were interesting. Could you give us some insight into how we can translate that into cost per kilowatt hour? Or some metric in terms of the gains that you're making?

Deepak Ahuja - Tesla, Inc.

Every data point, Rod, that we look at internally suggests that we are best-in-class, but we don't prefer to...

Elon Reeve Musk - Tesla, Inc.

We're best, which is not a class.

Deepak Ahuja - Tesla, Inc.

Yes. We're the best. Sorry.

Elon Reeve Musk - Tesla, Inc.

The best-in-class of one.

Jeffrey B. Straubel - Tesla, Inc.

I think directionally, Rod, it's helpful to understand the different commodities and the trends that we're pursuing in the batteries. Being on a path to reduce cobalt usage, for instance, has been something we've been working on for literally several years now, and this has been extremely helpful in the overall cost per kilowatt hour, especially with recent commodity price movements. So, we can't really be quantitative, but that directionally is a pretty good trend.

Elon Reeve Musk - Tesla, Inc.

Yeah, we think we can get the cobalt to almost nothing.
​

Any rational informed person would accept that Elon Musk and JB Straubel know more about the subject than you, Martin. A lot more about it.

​

 

[Doodlebug]

Well, clearly you are better informed about this subject than I am, so perhaps this is a case of me arguing with someone who knows considerably more than I do about a subject. That certainly annoys me greatly when it happens to me, and perhaps I'm guilty of the same thing here. If so, then mea culpa.

Anyway, I certainly am interested in learning more about this subject, so I am reading your posts with interest, even if I'm somewhat skeptical that any outsider can really figure out exactly how Tesla has designed and built its Semi Truck.


PP,
I agree, no one on the outside can figure it out exactly, its all guesswork.
Furthermore, for all we know the specs may change a bit based on testing, so its possibly also a moving target.

For me, this is less a matter of what specs the Semi will have, but more about what is realistically possible for a battery electric truck. One of the valuable roles Tesla is playing is demonstrating what's doable - something the existing OEMs have little incentive to do. On my read, what's possible is what the skeptics (e.g. David Green) and the fans are essentially arguing about.

The reason I sent you the Navistar link is because the KWH per mile that the latest diesel trucks are achieving provides a baseline to quickly work out what KWH per mile is possible for an electric truck (and therefore the battery requirement, per your previous posts on this topic).

Also, I'm always looking for info on battery costs from various sources (triangulation). Did you see this Cairn ERA report from October? I thought you might be interested. See Slide 9.
https://www.ny-best.org/sites/defau...Energy Storage Market Forecast October 11.pdf

Regarding your post below, we are thinking the same things about how to get weight out of the packs, yes.



I hope nothing I said suggested that Tesla/Panasonic are using batteries that have no improvement in energy density since 2012! It's just that when I read people claiming that Tesla/Panasonic's new 2170 cells have "35% better energy density" or even "50% energy density", then I have to wonder what they're comparing them against. I can certainly believe 35% better energy density since 2012. That would be only very slightly better than the overall trend of approx. 5% improvement per year. A 50% improvement is harder to believe, especially with so many people on the Tesla Motors Club forum insisting there isn't any significant improvement in energy density as compared to the 18650 cells which Tesla is using in the Model S and Model X.

Furthermore, nothing that Elon Musk or J.B. Straubel have said recently -- within the past year or so -- would lead me to the conclusion that the 2170 cells represent a significant energy density improvement (and thus lower weight) over the 18650 cells. (A slight improvement, yes, due to improvements in the geometry; but I'm very skeptical there is a significant improvement in energy density.) There are some comments from both of them on a conference call from a couple of years ago indicating an improvement in battery chemistry, but I see no reason to conclude that this same improvement isn't now in the 18650 cells. Note the newer 100 kWh packs for the MS/MX represent a newer design than the older MS/MX packs. There was some talk of an improved cooling system, so I can easily believe whatever new chemistry Panasonic is using was incorporated into 18650 cells going into the new MS/MX packs at that time.

Now, at the pack level, it may indeed be possible to shave some weight for the Semi Truck. Especially in the pack casing, which for the Model S/X is part of the structural integrity, helping to stiffen the car. If multiple packs are stacked into the Semi Truck in order to reach the ~800-1000 kWh or so that it needs, then there's no reason to have such very strong cases for the batteries. It might even be possible to use lightweight plastic cases, altho that might represent a safety concern in case of accident. It might also be possible to shave some weight on the cooling system; for example, using one or two large pumps to circulate the coolant rather than separate pumps for each individual section of the battery pack.

​

 

[The Duke]

I am new here so correct me if these observations are incorrect.

Watching the first post's video I had to laugh. Tesla has been making good if not great cars for quite some time. Some buyers are cult members, some are not. Lumping all Tesla owners into one group is just ignorant and insulting, but I think that is the point. He wants to polarize people.

I see a lot of speculation on what will and will not work but we really don't know much besides the fact Tesla does have a working semi that they use almost daily to haul from Fremont to Reno and back. As a reminder how little we know, Toyota has a working fuel cell semi in Long Beach based on a Freightliner. Unless you have found specifics about that conversion then please post them for comparison. Tesla has paraded the semi to prospective customers and come away with $$$ meaning the customers are at least optimistic. They have more information than we have here. I will believe informed support over negative conjecture at this point. It could go the other way, but the smart money is going with BEV semis working and profitable in some capacity.

A 500 HP diesel truck needs to give 100% to get over a lot of passes. The diesel loses some efficiency due to altitude and therefore is not a direct comparison to a 1,000 HP electric semi working at 50%. But I do agree that the heat might be a problem. My Model S is only good for two laps (about 4 minutes) at Mazda Raceway before heat throttles output. I can stretch that to three laps by changing lines, but 10 laps is out of the question. Please consider that my S is an 8 year old design for the most part. Newer BEVs are not getting throttled at the track so the semi may not have a heat problem.

 

[David Green]

I am new here so correct me if these observations are incorrect.

Watching the first post's video I had to laugh. Tesla has been making good if not great cars for quite some time. Some buyers are cult members, some are not. Lumping all Tesla owners into one group is just ignorant and insulting, but I think that is the point. He wants to polarize people.

I see a lot of speculation on what will and will not work but we really don't know much besides the fact Tesla does have a working semi that they use almost daily to haul from Fremont to Reno and back. As a reminder how little we know, Toyota has a working fuel cell semi in Long Beach based on a Freightliner. Unless you have found specifics about that conversion then please post them for comparison. Tesla has paraded the semi to prospective customers and come away with $$$ meaning the customers are at least optimistic. They have more information than we have here. I will believe informed support over negative conjecture at this point. It could go the other way, but the smart money is going with BEV semis working and profitable in some capacity.

A 500 HP diesel truck needs to give 100% to get over a lot of passes. The diesel loses some efficiency due to altitude and therefore is not a direct comparison to a 1,000 HP electric semi working at 50%. But I do agree that the heat might be a problem. My Model S is only good for two laps (about 4 minutes) at Mazda Raceway before heat throttles output. I can stretch that to three laps by changing lines, but 10 laps is out of the question. Please consider that my S is an 8 year old design for the most part. Newer BEVs are not getting throttled at the track so the semi may not have a heat problem.

On the cult you are absolutely right, of my 10 or so friends that have Tesla vehicles none are cult members, they just like the EV, and want to do something to help the environment. People on this forum, and that do not have Tesla vehicles are far more passionate about Tesla in my experience...

The Tesla semi could be great for certain missions, having tested a BYD battery semi myself, its certainly a work in progress.

Yes, going over the pass in my diesel semi at 2000 lb ft of torque (flywheel power before the gear advantage) It can run all day at that power level, or until you run out of fuel. Because large trucks today are turbocharged there is not a fall-off in HP until you get to 6000 or so feet, then it is very noticeable. A modern large truck diesel engine runs its most efficient at wide open throttle and max load, the BSFC numbers get much better at the peak. They is why I say EV trucks will be great for light and flat, diesels will always win in heavy and hard... Its the same equation you have in heavy equipment and jets.

 

[Pushmi-Pullyu]

I am new here so correct me if these observations are incorrect.

For what it's worth, it looks to me like you have a pretty good understanding of the subjects under discussion in this thread. Certainly you know enough to talk about them intelligently.

Watching the first post's video I had to laugh. Tesla has been making good if not great cars for quite some time. Some buyers are cult members, some are not. Lumping all Tesla owners into one group is just ignorant and insulting, but I think that is the point. He wants to polarize people.

The first time I saw someone post about a Tesla "cult" in an InsideEVs comment, I laughed. Sure, there are some cult-like aspects of die-hard fans of any brand of automobile, not just Tesla. I think it's amusing to compare the dedication of a die-hard fan to a "cult", regardless of whether that's being an avid fan of an auto maker, a sports team, a band, or whatever. Unfortunately, some of the serial Tesla bashers immediately started using the "cult" label as a serious label, as an insult and a bludgeon. That's not at all funny. It's meant to be insulting... and it is.

Does being a rabid sports fan make you a "cult" member?

So I'm quite willing to go along with the joke, when it's a joke, by calling myself "Tesla Cult Member #245" (and extra points for Tesla fans who can identify the source of that number!). But when it's meant to be insulting... well then, I don't like being insulted any more than the next person does.

I do agree that the heat might be a problem. My Model S is only good for two laps (about 4 minutes) at Mazda Raceway before heat throttles output. I can stretch that to three laps by changing lines, but 10 laps is out of the question. Please consider that my S is an 8 year old design for the most part. Newer BEVs are not getting throttled at the track so the semi may not have a heat problem.

The Tesla Model S isn't designed to run at maximum speed for long. It's not intended to be a racetrack car, and it's not designed to run in the "unlimited" lane on the Autobahn. Designing it for the latter would be rather silly, because the battery pack can't hold that much energy (as compared to a tank of gasoline) and so it would run the battery flat in a fairly short time. In my opinion, designing and building the Model S to run at its maximum speed for a sustained period would merely have made the car more expensive -- and possibly heavier -- for no good reason.

Contrariwise, the Tesla Semi Truck had darn well better be designed to handle the heat output from the battery pack, in providing sustained power to pull the load at highway speed, even in hilly country. Designing for that isn't rocket science; it's merely a matter of putting in a heat exchange system that carries heat away from the battery pack fast enough to prevent it from overheating. Tesla may need to beef up the size of the tubes carrying coolant thru the pack, or increase the speed of coolant flow, or both. (Obviously the Semi Truck will need a significantly larger radiator than the Model S's, for the battery cooling system.) Neither one of those things should be a serious challenge to an engineer, altho it may mean that Tesla can't just shove multiple Tesla Model 3 battery packs into the Semi Truck until they add up to 1200 kWh, or whatever kWh capacity the Long Range Semi Truck needs. The battery packs for the Semi Truck probably will need to be designed specifically for the Semi Truck.

Or -- This is pure speculation on my part, altho I think it's an interesting speculation: Is it any coincidence that the new 2020 Roadster had its pre-production debut at the Tesla Semi Truck event? Like the Semi Truck, the 2020 Roadster will need to be able to handle continuous high power output, and therefore lots of heat transfer in the battery pack. Tesla demonstrated the 2020 Roadster's ability to perform repeated jackrabbit accelerations, one after another over a period of 45 minutes, at the Tesla Semi Reveal event, giving demo rides to the public. It seems quite clear that the 2020 Roadster can handle battery pack heat output much, much better than the current Model S.

So here's the speculation: Can it be that Tesla engineered the 2020 Roadster pack to handle high heat output, and Tesla is using that same pack (claimed to be 200 kWh!) in the Tesla Semi Truck? I wouldn't be surprised to find this is true!

As far as mountain climbing... well, some industry watchers are saying that the Tesla Semi Truck might not work well in mountainous areas, and that perhaps the truck won't be able to pull a full load in mountainous regions. Perhaps concerns over maximum heat exchange when mountain climbing is why they are speculating that? I haven't seen anyone say just why they think the Tesla Semi Truck won't do well in mountainous regions, so perhaps that's the reason. But so far as I know, it's pure speculation. Has any one of the few trucking companies which has had a chance to test a Tesla Semi Truck found it overheats in mountain-climbing at highway speed? If so, I haven't read of it. NDAs do apply here, so if something like that did leak out it would likely be only as a rumor.

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