Tesla Semi

[Doggydogworld]

I can see Tesla using LFP for somethings, in particular a budget priced compact car.

Econo-car doesn't need 5000 cycles (except Robotaxis, ha).

For the Semi IMO lowest weight possible for the truck is very important,

Cost and cycle life are much more important.

Chinese LFP bus packs are now 160 Wh/kg. That matches S/X and even exceeds Model 3. Hopes for a huge density jump with Roadrunner are misplaced, IMHO. Most Semis will be 300 milers. 600 kWh @ 160 Wh/kg is only 3750 kg. You save almost that much in engine, transmission and fuel. So there's no payload problem.

The 500 miler might fall a couple tonnes short in payload, but most trucks on the road are less than 75k lbs and fleets will still have plenty of diesel tractors for those. Semi has many other long haul issues, anyway.

Is Tesla using a 811 NMC?

I'm pretty sure MIC Model 3 does. I don't see how 622 could almost match range at the same weight.

The massive paralleling of cells should drop the I^R losses.

Not within the cells, where it matters most.

 

[Brando]

@MC3OZ

obviously Model 3 is different from number 3.
please keep Model 3
I may have been the only one who was confused. Model 3 pack

 

[MC3OZ]

@MC3OZ

obviously Model 3 is different from number 3.
please keep Model 3
I may have been the only one who was confused. Model 3 pack

Sorry that was merely an approximate indicator of the number of cells a Semi pack might have, it was just how I thought about it initially...

I hope that clears up the confusion...

 

[mongo]

Not within the cells, where it matters most.

Gah, can't believe I screwed that up, thanks!

 

[mongo]

Does this help?
Tesla Semi Prototype Spotted Hauling 75,000-Pound Load Through Northern California

Note: that headline is potentially misleading. The total gross weight was 75k pounds, not the payload.

 

[JRP3]

Yes, every semi is not loaded to the maximum weight, but a lot of them are because to not load them fully is missed income--and they typically charge by weight.

Average load is <40k pounds. https://www.fhwa.dot.gov/reports/tswstudy/Vol2-Chapter3.pdf

Discuss.

 

[jerry33]

Discuss.

When I was working with trucking companies, they were very concerned about getting the most payload (weight) in the truck. Every pound of vehicle weight lost them money. Now I'm not doubting the statistics, but there are a wide range of companies who use trucks. Some loads, like furniture max out by volume. It just depends on the type of freight a particular company hauls (most trucking firms have specialties). This is somewhat akin to the range issue where the average person drives four miles a day. The average is meaningless if you live in the suburbs where your commute is likely 25 miles one way (though some co-workers drove 90 miles one way), and it's too far for those who live in the inner city.

 

[mongo]

Discuss.

 

[JRP3]

there are a wide range of companies who use trucks

That's really my point. When people say the Tesla Semi can't be competitive because of weight there is still a huge market even if it is a few thousand pounds heavier.

 

[jerry33]

That's really my point. When people say the Tesla Semi can't be competitive because of weight there is still a huge market even if it is a few thousand pounds heavier.

And we don't actually know the final weight of the Semi. My original post on this was just speculating on whether the Semi batteries weighed more or less than the engine and transmission of current production trucks. I don't know the answer to this question.

 

[mongo]

And we don't actually know the final weight of the Semi. My original post on this was just speculating on whether the Semi batteries weighed more or less than the engine and transmission of current production trucks. I don't know the answer to this question.

Don't forget fuel.
Dual 125 gallon tanks are around 1,800 pounds full. Though to match 500 miles range, it's
more like 600 lbs.(national average of 6.4 MPG full loaded)

 

[jerry33]

Don't forget fuel.
Dual 125 gallon tanks are around 1,800 pounds full. Though to match 500 miles range, it's
more like 600 lbs.(national average of 6.4 MPG full loaded)

The original post in the Investor thread mentioned fuel.

 

[mongo]

The original post in the Investor thread mentioned fuel.

Roger that. The breakdown can get quite detailed (no differential, onboard charger, exhaust...), but I saw that as biggie for powertrain.

 

[Doggydogworld]

And we don't actually know the final weight of the Semi. My original post on this was just speculating on whether the Semi batteries weighed more or less than the engine and transmission of current production trucks. I don't know the answer to this question.

Batteries + motors weigh more than engine/transmission for the 500 miler. Carsonight claims they'll save a couple tons more in frame, suspension, cab, etc. but I am very doubtful. In the last call Elon said they had to use NMC instead of LFP for Semi due to weight considerations. This is a bit odd as some LFP buses in China actually have higher pack density than S/X/3. So it seems they are counting on a Semi pack density that is even better than the cars via more efficient structural packaging (i.e. taller) and cooling (unknown). I don't expect a big jump in cell density on Battery Day, but every little bit helps as long as it doesn't increase cost by even a penny.

300 miler weight shouldn't be much of an issue. That's really the sweet spot of the market, anyway. This Gov't site has some Class 8 tractor weight info.

 

[JRP3]

This is a bit odd as some LFP buses in China actually have higher pack density than S/X/3.

S/X/3 don't use NMC. A large vehicle using NMC could have higher pack energy density than S/X/3 NCA and LFP. Cell level NMC is higher than LFP, since it's more stable than NCA it should lose less density to pack safety.

 

[Doggydogworld]

S/X/3 don't use NMC. A large vehicle using NMC could have higher pack energy density than S/X/3 NCA and LFP. Cell level NMC is higher than LFP, since it's more stable than NCA it should lose less density to pack safety.

Yes, NMC might help in shedding some pack weight. But NMC532/622 are not competitive with NCA cell density and NMC811 is not exactly super-stable. Also note that MIC 3 uses NMC and seems to have slightly lower pack density than Fremont NCA 3s.

The densest LFP bus packs I've seen are 160 Wh/kg vs. 190 for NMC. I always figured Semi would be ~200. I don't think the LFP bus packs are liquid cooled, which may not work for Semi.

 

[dc_h]

Note: that headline is potentially misleading. The total gross weight was 75k pounds, not the payload.

I can't vouch for the math, but they specifically claim this is the approximate and estimated weight of the concrete based on the volume/size of the concrete blocks.

from the article:
Napkin math supports the driver's claim that the payload nears 75,000 pounds; each of the nine blocks appear to measure approximately three by three by six feet. As concrete has a density of around 150 pounds per cubic foot, and the trailer is seemingly toting close to 500 cubic feet, our calculations put the truck's payload at close to 73,000 pounds.

 

[mongo]

I can't vouch for the math, but they specifically claim this is the approximate and estimated weight of the concrete based on the volume/size of the concrete blocks.

from the article:
Napkin math supports the driver's claim that the payload nears 75,000 pounds; each of the nine blocks appear to measure approximately three by three by six feet. As concrete has a density of around 150 pounds per cubic foot, and the trailer is seemingly toting close to 500 cubic feet, our calculations put the truck's payload at close to 73,000 pounds.

Yeah, I gave them too much credit. The author doesn't understand the terms involved:
"Again, despite this heavy load, the driver claims that the truck's range remains better-than-expected, with "expected" initially meaning around 500 miles with a payload of 80,000 pounds according to Tesla CEO Elon Musk at the Semi's reveal."
80k is gross, not payload.

From the post the article is based on
"According to the driver the truck is operating at approximately 75,000 lbs and the truck is meeting or exceeding the range estimates."

I think this is a case of finding data to support a conclusion:
Non reinforced concrete has a density of 140 lb/cuft. CMACN - Heat Conduction
3x3x6 x 9 = 486 x 140 = 68k
Assuming the blocks are slightly smaller, 75k for the whole thing is not out of the question.

However, what would be out of the question is a 75k pound load + trailer + tractor making it through the weigh station. The limit is 80k...
Weight Limitation | Caltrans

 

[JRP3]

However, what would be out of the question is a 75k pound load + trailer + tractor making it through the weigh station. The limit is 80k...
Weight Limitation | Caltrans

I agree unless there are exceptions for testing or something.

 

[Doggydogworld]

They look like these, 4320 lbs each for just under 39k lbs total.