GRA
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Re: Tesla Semi Truck

Mon Mar 12, 2018 5:12 pm

Found some guesstimates of the Model S pack size. It's stated that the batteries are located inside the wheels (F to R), and as the wheelbase is 116.5" and the width 77.3", one size guesstimate I found was about 112" x 70" (9'4" x 5'10"). Height of the main part of the pack is only about 5" though. As these dimensions are too wide to put side by side or to be loaded crosswise, if Tesla wants to ship complete battery packs from the Gigafactory they'll definitely have to stack them to get anywhere close to gross weight, presumably using racks to avoid damage. The Model 3 pack is presumably a bit shorter but the wheelbase has only dropped to 113.2", so the likelihood that a complete Model 3 pack will fit crosswise in even a wide-body trailer (102" ext. width, but about 98" internal) seems minimal. I found weight and cube for the LR pack, 1,058 lb. and 14.13 ft.^3.

I think in order to maximize cube as well as gross, and also keep the C.G. down, it might be better to ship battery components rather than complete packs and do final assembly in Fremont, but I expect Tesla will look at costs both ways and decide which makes the most sense. Either way, even at only 1,000 Model 3s/week production and stacking packs 10 high (unlikely for C.G. reasons) so they could theoretically put up to 40 in a 40' container, that's 25 round trips/week.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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RegGuheert
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Re: Tesla Semi Truck

Mon Mar 12, 2018 5:42 pm

This excellent post at Tesla Motors Club makes a fairly careful estimate of the capacity of the Tesla Semi battery:
Kolodziejski at Tesla Motors Club wrote:I think this strongly suggests a usable of 800kWh, with a megawatt hour being impossible with the same chemistry as the Model 3.
But I will point out that if Tesla can manage to stabilize the NMC chemistry in the batteries used in the Model 3 for operation at higher voltages, 1 MWh should be quite achievable without adding any more cells.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
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TonyWilliams
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Re: Tesla Semi Truck

Tue Mar 13, 2018 3:53 am

lorenfb wrote:
RegGuheert wrote:That's a good question, but even fully unloaded, this trip likely required the consumption of at least 300 kWh and traveled over 250 miles.


Where are the data to conclude this, i.e. an energy consumption of at least 300 kWh (over 250 miles) - less than a mile/kWh?


Elon Musk has stated that the Semi would beat 2kWh per mile, and certainly 300kWh over 250 miles is that. I suspect is far closer to 500kWh for the trip.

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RegGuheert
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Re: Tesla Semi Truck

Tue Mar 13, 2018 8:12 am

FWIW, Nikola estimates efficiency to be 0.58 mi/kWh (1.72 kWh/mi) (at 22:45 in the video):



Other electric truck manufacturers come up with efficiencies between 1.4 kWh/mi and 2.0 kWh/mi based on unknown assumptions:
JKolodziejski at Tesla Motors Club wrote:Daimler E-FUSO Vision One (slightly streamlined, flat face, 11 tonne payload) => 300 kWh / 220 miles = 1.4 kWh/mile.

Daimler unveils heavy-duty all-electric truck concept with ‘up to 220 miles’ range

Cummins AEOS (34 tonnes overall, 75k lbs, Class 7 (drayage?) ) => 140 kWh / 100 miles = 1.4 kWh/ mile.

Besting Tesla's Reveal By Just Days, Cummins Unveils AEOS Electric Semi

BYD Class 8 (Cheap, Chinese-made conventional flat-face truck) => 188 kWh / 94 miles => 2.0 kWh / mile exact.

http://www.byd.com/usa/wp-content/uploa ... -final.pdf


Freightliner Supertruck (65k lbs, most similar use case and possibly similar all-length drag efficiency to the Tesla Semi.)

https://www.trucks.com/2015/06/25/freig ... efficient/

=> 48-52% thermal efficiency, 12.2 US-mpg, => 3.22 miles / L or per 10.8 kWh(th) @ 0.48 to 0.52 = > ~ 3.22 miles / 5.2-5.6 kWh mech.
=> (5.2 to 5.6) kWh / 3.22 miles = 1.61 to 1.73 kWh / mile after engine.

... and a 92% efficient battery power equivalent to "48-52% efficient 12.2 US-mpg Freightliner Supertruck" = 1.61 to 1.73 / 0.92 = 1.75 to 1.88 kWh / mile.


And this.

Tesla Semi is reasonable, part 1 | Selenian Boondocks

"<2 kWh" was stated for a reason.

1.5 to 1.7 kWh per mile at 56-65 mph is realistic.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

lorenfb
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Re: Tesla Semi Truck

Tue Mar 13, 2018 9:49 am

lorenfb wrote:1. What is the generally accepted typical energy usage per mile (miles/gal) for a diesel rig (tractor & typical fully loaded trailer)
traveling at 60mph on a level highway?
2. What is the assumed miles per kWh for the semi in #1, given these components;
a. Rolling Resistance Losses - RR = k * V
b. Drag Losses - DL = k * V^3
c. Energy Conversion Efficiency of the diesel ICE, - assumed to be a little better than a gasoline ICEV (@ about 60%), assume 75% for diesel?
3. What is the assumed miles per kWh for an EV semi assuming RR & DL are the same for a diesel ICE semi traveling under the same
conditions and assuming about +95% energy conversion efficiency for the EV semi?

A simple solution to #3;
1. Assume 38 kWh per gallon of diesel fuel.
2. Assume RR + DL = energy output of diesel = .75 of diesel fuel energy input
3. Then miles/kWh for the EV semi = miles/gal (diesel mileage) X (EV conversion efficiency) / (kWh/gal X diesel conversion efficiency),
or simply MPG (#1) X .95 / (38 X .75)
4. Assuming a diesel ICE under conditions of #1 with an MPG = 5 miles/gal (bad assumption?) then;
EV semi miles/kWh = .167 miles/kWh
5. If one assumes that the diesel is only 50% efficient versus 75%, then the EV semi miles/kWh becomes .5 miles/kWh


Using an EV efficiency of 98% and a nominal 7 miles/gal for the diesel, the result becomes; .72 miles/kWh (1.38 kWh/mile)

Theory makes for a great starting point, but it's time for Tesla to do actual long term field testing:

lorenfb wrote:If Tesla is really serious about producing a EV semi in the near term, they should build two test tractors capable
of pulling a vehicle transporter loaded with seven Tesla vehicles being transferred from Fremont to the L.A. area,
by mid 2018. From what I've seen over the last 2-3 years, Tesla makes at least two deliveries per week to the L.A. area.
Initially from a battery energy perspective, a range of only about 150 miles would be necessary traveling the 101 Hwy,
thus avoiding the GrapeVine and Hwy 152 via Hwy 5. Besides, the availability of SCs is greater along the 101 Hwy,
resulting in an initial smaller battery. The data gathered would not only further corroborate the design concept and
technology, but additionally it would greatly enhance Tesla's PR with regard a EV semi.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Tue Mar 13, 2018 10:19 am

lorenfb wrote:Theory makes for a great starting point, but it's time for Tesla to do actual long term field testing:
Tesla and the other companies have actually measured the energy use of their trucks. You are the one who is stuck on theory and the odd man out with 2.5 kWh/mi.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

lorenfb
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Re: Tesla Semi Truck

Tue Mar 13, 2018 3:08 pm

RegGuheert wrote:
lorenfb wrote:Theory makes for a great starting point, but it's time for Tesla to do actual long term field testing:
Tesla and the other companies have actually measured the energy use of their trucks. You are the one who is stuck on theory and the odd man out with 2.5 kWh/mi.


No, not really! What was presented was a first order approximation, i.e. based on simple H.S. physics, which was lacking in the thread.
Each is free to use different assumptions. Surprised that you didn't present some simple analysis other than what usually gets presented,
i.e. a copy & paste. The approximation obviously didn't include mods to the losses, i.e. rolling resistance and Elon's "tweaking" of the drag
coefficient. Again, without any rigorous worst case field testing, i.e. thousands of miles over various terrains, the Tesla EV semi
projections are marginal at best and this thread "goes nowhere fast".
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Tue Mar 13, 2018 6:44 pm

lorenfb wrote:No, not really! What was presented was a first order approximation, i.e. based on simple H.S. physics, which was lacking in the thread.
And your H.S. physics causes you to come up with this:
lorenfb wrote:Did you overlook this:
Using an EV efficiency of 98% and a nominal 7 miles/gal for the diesel, the result becomes; .72 miles/kWh (1.38 kWh/mile)
Let's correct your math to eliminate the confusion you are trying to spread:

7 mi/gal * 2 gal(in)/gal(out) * 1/38 gal/kWh = 0.37 mi/kWh = 2.7 kWh/mi

This result seems pretty clear: After throwing away 50% of the energy content of the diesel in the tank, these trucks achieve low efficiency due to their inability to recover some of the potential energy gained in climbing hills. They are also losing some of their energy to poor aerodynamics.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

lorenfb
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Re: Tesla Semi Truck

Tue Mar 13, 2018 9:02 pm

RegGuheert wrote:
lorenfb wrote:No, not really! What was presented was a first order approximation, i.e. based on simple H.S. physics, which was lacking in the thread.
And your H.S. physics causes you to come up with this:
lorenfb wrote:Did you overlook this:
Using an EV efficiency of 98% and a nominal 7 miles/gal for the diesel, the result becomes; .72 miles/kWh (1.38 kWh/mile)
Let's correct your math to eliminate the confusion you are trying to spread:

7 mi/gal * 2 gal(in)/gal(out) * 1/38 gal/kWh = 0.37 mi/kWh = 2.7 kWh/mi.


Yes, a simple math error, but the original relationship was correct. To help you with the units in your expression, my initial expression;

3. Then miles/kWh for the EV semi = miles/gal (diesel mileage) X (EV conversion efficiency) / (kWh/gal X diesel conversion efficiency),


Have you forgotten Tesla's estimate per your quote;
Tesla Semi webpage wrote: <2 kWh/mi


Then my assumptions weren't that far off when the math error was corrected (2.7 kWh/mi), right? As I said previously:

Each is free to use different assumptions. The approximation obviously didn't include mods to the losses, i.e. rolling resistance
and Elon's "tweaking" of the drag coefficient.


RegGuheert wrote:This result seems pretty clear: After throwing away 50% of the energy content of the diesel in the tank, these trucks achieve low efficiency due to their inability to recover some of the potential energy gained in climbing hills. They are also losing some of their energy to poor aerodynamics.


So you just realized that? And it took a simple H.S. physics equation to get you thinking in those terms after all those posts in this thread?
I'm really disappointed!
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Wed Mar 14, 2018 3:41 am

You really are here just to pollute the thread...
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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