bambam4171
Member
Elon said that the range is a highway speeds which is kind of a worst case number if I recall correctly. No one ever talked about any other factors like uphill, cold climate, endless recharges or anything else I believe.
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Lets work out the Tesla Semi-Truck Technical Specs
- Thread starter lnpurnell
- Start date
Elon said that the range is a highway speeds which is kind of a worst case number if I recall correctly. No one ever talked about any other factors like uphill, cold climate, endless recharges or anything else I believe.
Flat highway at 55mph. Any degree up and it will drop massively.
Cabin heat - absolute minority.
Pack temperature - can be controlled before departure
What Elon didn't definitely thought about is range in wet-snow conditions.
Going heavy uphill range will be around 50 miles with cargo.
Diesel truck consumption will spike from 30l/100km to 300l/100km going uphill.
What goes up must come down. And trucks are not going to downhill very fast, so get a lot of regen.
Going slower and being so heavy, relative losses going over a hill should be significantly lower than with a personal vehicle going over the same hill at the same let alone traveling at higher speeds coming down. Important though is that the motors and battery have capacity to do something with the immense regen power available, and not having to resort to engage friction brakes.
If a fleet manager has the opportunity to keep the wheels rolling for all but megcharging, mileage is going to add up quickly and a million miles will be done and over with in not so many years. Then still, batteries will only get cheaper, the pack will have earned itself back by then, and with Tesla's recycling operation well up to speed by then, you can get a new pack at a lower price than when all matterials were newly mined. If today tesla is playing with $100/kWh at the cell level for new cells, imagine what it may be in 8 years from now, with scaled recycling and true giga production? 1MWh is not going to break the bank quite so much in 2026.
Going slower and being so heavy, relative losses going over a hill should be significantly lower than with a personal vehicle going over the same hill at the same let alone traveling at higher speeds coming down. Important though is that the motors and battery have capacity to do something with the immense regen power available, and not having to resort to engage friction brakes.
If a fleet manager has the opportunity to keep the wheels rolling for all but megcharging, mileage is going to add up quickly and a million miles will be done and over with in not so many years. Then still, batteries will only get cheaper, the pack will have earned itself back by then, and with Tesla's recycling operation well up to speed by then, you can get a new pack at a lower price than when all matterials were newly mined. If today tesla is playing with $100/kWh at the cell level for new cells, imagine what it may be in 8 years from now, with scaled recycling and true giga production? 1MWh is not going to break the bank quite so much in 2026.
If destination is higher, then vehicle doesn't come down. I know, hard to imagine a problematic mountain from Netherlands. Same here where I live
But a friend of mine told me about some semi trips he took in Norway. Going uphill... for an hour.
Regen loses a third. So going uphill might cost 300kWh, and downhill recovers 200kWh.
But a friend of mine told me about some semi trips he took in Norway. Going uphill... for an hour.
Regen loses a third. So going uphill might cost 300kWh, and downhill recovers 200kWh.
No, it will always come down... What you are trying to say is that it may go up fully loaded, and go down empty...
... and living where I do I have no problem to imagine some problematic mountains
And that is why I'm looking forward to some sort of "charge while your drive" system. Not on every road everywhere for everyone, but especially on step uphills for heavy transporters. It may be inductive in the road or by a pantograph on the roof.
But a friend of mine told me about some semi trips he took in Norway. Going uphill... for an hour.
Even an hour is only a little over a tenth of Semi's flat-land range.
From physics, it takes a little over 100 kWh for a fully loaded Semi to climb 1 kilometer of altitude. Semi has potentially as much as 1 MWh of batteries. A mountain is not stopping it.
As for how much range you lose: it depends entirely on how much you regen vs. coast on the downslope. Regen efficiency should be quite high on Semi, with the combination of a large li-ion pack and PM motors rather than induction. Maybe you get 75-80% of the range back if it's all regen. On the other hand, if it's coasting down then there's little if any loss. You have to drive the motors in a higher power band and run more current from the batteries during the climb, which may equate to lower efficiency during it. But then again, you're probably driving slower, too, and lower density air equals lower wind resistance.
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You must accept heartbreaking fact, that even 3 meters of that cable between semi and megacharger costs A LOT.
Making it 3000 meters will cost much more than 1000 times more
It's cheaper to have a megacharger halfway. Or even a mega-discharger, in case of downhill
Reciprocity
Active Member
If destination is higher, then vehicle doesn't come down. I know, hard to imagine a problematic mountain from Netherlands. Same here where I live
Trucks tend to drive routes that have then back where they started so as long as this how is not an 11 hour drive they more then likely would net out in terms of elevation change. I am sure there are exceptions, there always are. This will not be the semi for every need, just most of them. It's a great start and drivers and companies will adapt to take advantage.
Reciprocity
Active Member
It actually costs more to deliver the electricity then to buy it. Tesla won't sell excess back, they will store it. When you sell yours back to pge, it doesn't actually go back to pge, it goes to your neighbor who is paying .15c because the bill isn't broken down by provider, it's flat rates for supply and delivery. If you supply it, the delivery is basically free.
You not the nail on the head though. Tesla will supply and store their own energy at rates higher then wholesale but will have 0 delivery cost aside from the two way trip into and out of the battery. This 7c will actually be a profit center. Also Tesla is going to partner with customers to add solar, battery and megachargers to their facilities. This will be a huge profit center for Tesla and a huge savings for the customer because the production side will save them money on their entire facilities, not just semi charging.
ccutrer
Active Member
If you’re driving 60mph uphill, and have a constant source of power, why does that power need to be supplied at a rate of 800mph of rated range? Heck, 30mph would be plenty, just so long as it’s enough to offset inordinately high consumption from bad weather and elevation gain.You must accept heartbreaking fact, that even 3 meters of that cable between semi and megacharger costs A LOT.
Making it 3000 meters will cost much more than 1000 times more
It's cheaper to have a megacharger halfway. Or even a mega-discharger, in case of downhill
What's the point of the system when it becomes a bottleneck? There will be cars behind truck... stuck.
Truck will discharge at... roughtly.. 500mph rated-range going uphill at 50mph. So 500mph rated-range charge rate is a minimum to even consider.
This uphill overhead wire should support at least 5 trucks. Making it 2500mph rated-range charging system.
This system must be up to 800V DC (truck can't accept higher voltage). DC voltage is a bad choice, especially at 800V.
I find no economical ways to fulfill that dream with current knowledge known to mankind.
400-500kW onboard AC-DC converter. That is not economical. Nor lightweight. For the vehicle side. This solves overhead wire-pair price though.
I may have mathed wrong, but not accounting for wind/tire/etc resistance, just fighting gravity, and assuming 80,000lb (36,000kg) at 60 mph (26.8m/s) at 7% grade (from a brief google, seems to be steepest grade of any significant length as far as interstates go), I came up with ~1160 kW needed to maintain speed.
So yes, if it has only 800 kWh, it will be depleted in around 40 minutes (again not accounting for wind/tire/etc). For comparison, I did the same calculation with a 1% grade and the result was ~165 kW.
I doubt there's any 7% grade highway sections for more than a few miles at a time though - surely 30-40 mile long sections are uncommon (on account of the resulting altitude being higher than commercial aircraft can fly)? If we naively assume a single stretch going from sea level to 10,000 ft, at 7%, it would be (again, if I didn't math wrong) less than 3 miles long, which means the worst case loss in addition to level power needs (i.e., wind/tire/etc) would be less than 58kWh additional power needs over that stretch, or a loss of less than 8% range assuming 800kWh pack.
Put this together with an assumed worst case range of 500 miles on level road (I think that is a pessimistic interpretation for level road, but we'll make this worst case), and assume only 800kWh battery - every time you drive to up a 7% grade at 60mph to 10,000 feet you lose an extra 40 miles of range (i.e., you traveled 3 miles but used 43 miles of range). This sounds bad, but you'll get some of that back on the way down the other side, and there's not going to be many stretches with more than a handful of such climbs. So if you go back down and take a hopefully pessimistic 50% regen, that means for every 6 miles (3 up, 3 down) you'll use less than 25 miles of range.
TL;DR: The concern about range on hills is probably overblown, even if the greater power needs are true - the power need is for such a short period of distance that it shouldn't impact range significantly unless it occurs at the end of an already borderline trip.
So yes, if it has only 800 kWh, it will be depleted in around 40 minutes (again not accounting for wind/tire/etc). For comparison, I did the same calculation with a 1% grade and the result was ~165 kW.
I doubt there's any 7% grade highway sections for more than a few miles at a time though - surely 30-40 mile long sections are uncommon (on account of the resulting altitude being higher than commercial aircraft can fly)? If we naively assume a single stretch going from sea level to 10,000 ft, at 7%, it would be (again, if I didn't math wrong) less than 3 miles long, which means the worst case loss in addition to level power needs (i.e., wind/tire/etc) would be less than 58kWh additional power needs over that stretch, or a loss of less than 8% range assuming 800kWh pack.
Put this together with an assumed worst case range of 500 miles on level road (I think that is a pessimistic interpretation for level road, but we'll make this worst case), and assume only 800kWh battery - every time you drive to up a 7% grade at 60mph to 10,000 feet you lose an extra 40 miles of range (i.e., you traveled 3 miles but used 43 miles of range). This sounds bad, but you'll get some of that back on the way down the other side, and there's not going to be many stretches with more than a handful of such climbs. So if you go back down and take a hopefully pessimistic 50% regen, that means for every 6 miles (3 up, 3 down) you'll use less than 25 miles of range.
TL;DR: The concern about range on hills is probably overblown, even if the greater power needs are true - the power need is for such a short period of distance that it shouldn't impact range significantly unless it occurs at the end of an already borderline trip.
I'm getting about half your number with 36,364 kg, rising at 1.88 m/s, 0.186 kWh/s.
Worst case numbers from my spreadsheet: 725kW rate for 7% grade @ 65 MPH. 10,000 ft (sea level to highest city in US) at 7% would be 27 miles. Call it 30 minutes/ miles. With 80k lbs, good tires and aero loading, that is 30*1.6 = 48 kWh + 725kW×.5hr =362.5kWh, or 410kWh, about half the pack size.
jackbowers
Jack Bowers
The combined weight of my Model X plus Bowlus trailer is about 8,000 lb. Coming out of Stovepipe Wells in Death Valley on the way to the Lone Pine Supercharger there is a 5,000 ft climb over 13 miles, roughly a 7% grade. I drove it at speeds ranging 40-50 mph, trying to keep the power draw just below 100kW to keep I^2*R losses from getting out of hand. The energy used was roughly 2 kWh per mile. For the Semi, we can probably figure that better batteries, better inverters, and permanent magnet motors might improve efficiency by 20%. But doing that climb at 65 mph with 80,000 lb would still require draws in excess of 1150kW and consume over 200kWh.
Incorrect calculations. 4 motors will not give that much and also there is not enough cooling capacity. But we know the vehicle can do it.
Just take basic calculations. 36 metric tons going up at the rate previously mentioned. Add 10% losses. Add distance travelled as well.
Reciprocity
Active Member
There is to much focus on 7% grades. Elon stated 65 for a 5% grade. This could very well mean that a 7% would be slower. Also, the Tesla semi will not be for every route. There will still be routes that are better for Diesel until the energy densities improve a bit more to allow for more capacity, better cooling and higher regen. Going down hill, you are going to have to regen as the truck would get going way to fast if you just coasted. TACC should be smart enough to coast when it makes sense and regen when it makes sense. Regen will be limited based on heat as well, which others have noted. If you heat up the whole system going up, you will lose some regen going down unless the entire system is large enough and with good enough cooling to take full advantage of the regen.
In general, those steeper grades are rare because they are deadly. Going down those grades you see those sand outlets for run away trucks to merge of the freeway and be stopped by the sand.
In general, those steeper grades are rare because they are deadly. Going down those grades you see those sand outlets for run away trucks to merge of the freeway and be stopped by the sand.
Well, I probably mathed wrong. Especially if I'm off by a factor of 10 for the distance traveled to raise 10,000 ft at 7% grade ...
I think that Roadster 2020 has 200kwh 2170 battery pack. It's one 200kwh pack or two 100kwh, but my bet is on one 200kwh. The same packs are used in semi 4 of them so 800kwh of batteries. Making semi efficiency 1.6kwh per mile. No breakthrough, no solid state batteries... Just simple model 3 batteries.
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