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Tesla Semi’s EPA range rating will simply never exist…Here’s why

I wish that the graphic of the Semi trip from SF to SD showed the topography in something other that dark grey (!), but it is quite remarkable that the grapevine climb and descent, and well as the other ups and downs along the route, had very little effect on overall Wh/mile compared to flat terrain driving. Regen shines here.

I set the slope of the added line to match the the interval between ~ miles 200 -- 250 of the trip where the terrain is flat.
This map has some % grades on it in the lower right.
See it here: Elevation from Fremont (California) to San Diego via Grapevine
t8y1HBg.jpg


Google map with waypoints:
 
I wish that the graphic of the Semi trip from SF to SD showed the topography in something other that dark grey (!), but it is quite remarkable that the grapevine climb and descent, and well as the other ups and downs along the route, had very little effect on overall Wh/mile compared to flat terrain driving. Regen shines here.

I set the slope of the added line to match the the interval between ~ miles 200 -- 250 of the trip where the terrain is flat.
View attachment 880919
It's not all Regen, at least not battery Regen per se ... going up the hill a lot of it is Kinetic Energy converted to Potential Energy "stored" in the mass of the entire vehicle, batteries included, and even some in the human occupant . Then the PE is converted to KE coming back down the hill. I daresay it's 100% efficient roundtrip from KE to PE to KE. All vehicles have it, not just EV's, even people have it.

But I think the driver skill is in fact to keep that PE conversion as efficient as possible, you want to minimize inefficient energy transfer elsewhere. If the driver applies acceleration to maintain constant speed going up hill, then you're converting battery energy, and then invoking battery Regen going down, losing some energy to roundtrip Regen inefficiency (or otherwise you' may lose it to increased air drag from faster speeds). So on smaller rolling hills, it's more efficient to actually minimize Regen by letting the vehicle slow down and speed up through KE-PE-KE conversion, though too fast you increase air drag. But on the big climbs like the Grapevine, you have no choice but to invoke some Regen to not go too fast, but it's only like 4% of the battery coming down the other side (all the lost energy was steady road and air drag losses that are the same whether on the flats or the hills).

So I marvel more at nature's battery (Potential Energy), 2nd the likely skill of the driver probably trained to make the most use of Regen, PE, and speed to maximize hypermiling, and distant 3rd the Regen.
 

aerodyne

MS LR = Last Car?
Nov 19, 2018
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It's not all Regen, at least not battery Regen per se ... going up the hill a lot of it is Kinetic Energy converted to Potential Energy "stored" in the mass of the entire vehicle, batteries included, and even some in the human occupant . Then the PE is converted to KE coming back down the hill. I daresay it's 100% efficient roundtrip from KE to PE to KE. All vehicles have it, not just EV's, even people have it.

But I think the driver skill is in fact to keep that PE conversion as efficient as possible, you want to minimize inefficient energy transfer elsewhere. If the driver applies acceleration to maintain constant speed going up hill, then you're converting battery energy, and then invoking battery Regen going down, losing some energy to roundtrip Regen inefficiency (or otherwise you' may lose it to increased air drag from faster speeds). So on smaller rolling hills, it's more efficient to actually minimize Regen by letting the vehicle slow down and speed up through KE-PE-KE conversion, though too fast you increase air drag. But on the big climbs like the Grapevine, you have no choice but to invoke some Regen to not go too fast, but it's only like 4% of the battery coming down the other side (all the lost energy was steady road and air drag losses that are the same whether on the flats or the hills).

So I marvel more at nature's battery (Potential Energy), 2nd the likely skill of the driver probably trained to make the most use of Regen, PE, and speed to maximize hypermiling, and distant 3rd the Regen.

Regen is only 85% efficient. I agree with the rest, If you can coast more, with reduced Regen, you will gain efficiency.

That said, Semi coasting 5 northbound past Tejon pass is not something I'd like too see up close!
 
Back on topic. Do diesel trucks get EPA few efficiency ratings?

Perhaps the thinking is that these are full grown adults who are making business decisions and can figure things out on their own. They don't need a nanny state government to help them make their decisions. (Sorry, rant over.)
EPA fuel economy ratings are only given for cars and light trucks.

The fleets that buy bigger trucks do care a lot about economy, but before buying a hundred trucks, they can buy one of each possible choice to test economy themselves. Individuals buying one car or light truck for themselves are less able to do this, so there is more value in a standardized economy rating for cars and light trucks.
 
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SageBrush

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going up the hill a lot of it is Kinetic Energy converted to Potential Energy

No ...
Speed is conserved for the most part, or all if it is Tesla Semi

I used to play the game you talk about in the mountains of Colorado in a Prius. Not possible with a 4,000 foot drop and in an 82k pound vehicle.
 
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The fleets that buy bigger trucks do care a lot about economy, but before buying a hundred trucks, they can buy one of each possible choice to test economy themselves. Individuals buying one car or light truck for themselves are less able to do this, so there is more value in a standardized economy rating for cars and light trucks.
Precisely. And you can be certain that companies like Pepsi are having mileage assurances from Tesla written into the contract. This is a new technology and they’re not going to just blindly trust the word of any CEO.
 
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aerodyne

MS LR = Last Car?
Nov 19, 2018
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50¢ a kWh ?
I bet that is a corner case. In general I expect these companies to charge at night, using commercial tariffs.
Since L4 does not exist yet in any quantity, current Tesla L3 rate at $0.48/KwH is a likely number.

Even TOU rates are high in CA, I pay $0.21 off peak. Commercial numbers not published that I can see, but my guess is average will be north of $0.24/KwH
 
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Dave EV

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I used to play the game you talk about in the mountains of Colorado in a Prius. Not possible with a 4,000 foot drop and in an 82k pound vehicle.
Even in a Prius, or other passenger automobile, there's so many variables it's not always straight forward to calculate - length of descent, weight of vehicle, aero-drag of vehicle, etc, all add up. Are you going for maximum efficiency? What's the minimum average speed you're willing to drop down to?

But no matter what, you can assume that any energy lost to wind resistance is energy thrown away. If you're coasting at terminal velocity, you're throwing all aero-drag energy away.

In a gas car with no battery to store braking energy, it doesn't matter - coast as much as possible and aim for the highest speed at the bottom of the hill.

With a hybrid or EV, the calculations get more complicated - but no matter what, you will be more efficient if you regen at lower speed until the point at which you can coast and still reach terminal velocity at the bottom of the hill.

It would be interesting to calculate all the variables to determine the exact speeds one should drive for maximum efficiency - I imagine that Tesla has all the data needed to do this. I would love to see a feature like this added to TACC. Not holding my breath, though - TACC can't even slow down or come to a stop or accelerate in an efficient manner.
 

SageBrush

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Commercial numbers not published that I can see

LADWP commercial rate, 4.8kV service
Look at the A2 schedule
Keep in mind that a Tesla Semi is probably going to leave Los Angeles, so this is only one data point.
My eyeball estimate is about 12¢ a kWh + $10/kW demand charges. Demand charges are tricky for obvious reasons. If the demand is constant and used for 6 hours a day, it adds about 5.5¢ a kWh. 12 hours usage a day would reduce demand charges to about 2.75¢ a kWh.

Screen Shot 2022-12-04 at 4.46.32 AM.png Screen Shot 2022-12-04 at 4.56.16 AM.png
 
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SageBrush

REJECT Fascism
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the calculations get more complicated

They are simple for the Tesla Semi. The vehicle mostly drives at the speed limit. Excess potential energy from long descents are pushed into the pack at around 70% efficiency. The hypermiling tricks you are somewhat describing are not in play for a couple of reasons, chief among them that 2, they are not necessary; and 1, playing with high speeds in an 82k pound truck is a very bad idea.
 
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aerodyne

MS LR = Last Car?
Nov 19, 2018
5,246
8,423
Los Angeles
LADWP commercial rate, 4.8kV service
Look at the A2 schedule
Keep in mind that a Tesla Semi is probably going to leave Los Angeles, so this is only one data point.
My eyeball estimate is about 12¢ a kWh + $10/kW demand charges. Demand charges are tricky for obvious reasons. If the demand is constant and used for 6 hours a day, it adds about 5.5¢ a kWh. 12 hours usage a day would reduce demand charges to about 2.75¢ a kWh.

View attachment 881310 View attachment 881311
Good catch, I am not serviced by LADWP, so I did not check there.
 
There's no way they averaged 66 mph. Just watch the video, very little time is spent above 60 mph, most of the time is spent from 50-55 mph.

This is actually my biggest beef with the run, it's fairly obvious that they were hypermiling it, most trucks run ~60 mph on I5 when they were doing 50-55 even when the road was wide open in front of them.
I can't see how we should expect any manufacturer to report or demonstrate economy results at illegal speeds. And I wouldn't call 55 in a 55 "hypermiling" in any sense.
 
Quick reality check here...only valid for California.


Assumptions:. 1.7 KwH and 5.5 mpg for Tesla Semi and Diesel class 8 truck

I'm getting a cost of $0.82/mile for the Semi, vs $1.09/mile for a diesel class 8.

That's only a 25% reduction. Not that much.

Assuming your numbers and calculations are correct, a 25% reduction in fuel/energy costs seems enormous to me. What kind of reduction would it take to impress you?
 

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