Tesla Semi Finally Revealed

[freebeard]

Originally Posted by redpoint5

Of course there are more promising technologies we should be exploring, but when have the masses been good at employing "common" sense or reason?

There was that stretch from rockabilly music to the hippys. I claimed at the time that they were the real conservatives. Then the Yippies came along and steered everything to the left. Post-Millennials seem to be recoiling from the Millennial commies. Since it's not The Lounge, I'll just say go to Youtube and look for Lucy Gowen covering Beatles songs.

Seriously, the hippys were right. There is an exhaustive search for energy density. Joseph Goodenough and others.

pcmag.com:Fisker Battery Promises 500 Mile EV Range, 1-Minute Charging

Fisker just filed a patent claim. How long to bring it to market?

[RedDevil]

Originally Posted by Hersbird

But the battery is really has a poor amount of energy storage compared to the weight. A Tesla battery weighs what, 1200 pounds? That's 150 gallons of gas or on the other side a Tesla's 300 mile range would only require 8 gallons of gas or 65 pounds of fuel in a under 30 pound container, under 100 pounds total. That's what makes a great mobile source of energy, lots of energy in a light weight.

True, but the upside is that the combined weight of motor, wires and control electronics is way less than the engine, radiators, exhaust, gearbox etc. that a conventional truck needs. The heavy battery outweighs that advantage, but it does make a dent in it.

Come improvements in battery chemistry and cost like the solid state batteries that Toyota and Panasonic expect to start shipping around 2020, the balance will shift more and more in favor of electric cars.

[NeilBlanchard]

Originally Posted by Hersbird

But the battery is really has a poor amount of energy storage compared to the weight. A Tesla battery weighs what, 1200 pounds? That's 150 gallons of gas or on the other side a Tesla's 300 mile range would only require 8 gallons of gas or 65 pounds of fuel in a under 30 pound container, under 100 pounds total. That's what makes a great mobile source of energy, lots of energy in a light weight.

It seems that Tesla has new, much more powerful batteries; both from the Roadster 2 (with 2X the battery capacity of their current batteries) and the Semi, with its reported 1MwH battery in a $180,000 vehicle.

Electricity is about 90% efficient, and it doesn't need to be transformed from liquid to heat to mechanical. And mechanically, an electric motor is nearly perfect, while a reciprocating piston engine is poor. Imagine driving a semi - with no shifting!

[sendler]

The cell chemistry is not that much better than before. There are just that many more of them.

[redpoint5]

Originally Posted by Hersbird

But the battery is really has a poor amount of energy storage compared to the weight. A Tesla battery weighs what, 1200 pounds? That's 150 gallons of gas or on the other side a Tesla's 300 mile range would only require 8 gallons of gas or 65 pounds of fuel in a under 30 pound container, under 100 pounds total. That's what makes a great mobile source of energy, lots of energy in a light weight.

Sure, for many use cases, fossil fuels make more sense. I wouldn't go on a road trip in an EV.

For other uses, such as in town transportation, an EV can have a lower total cost of ownership, less maintenance, and no time spent at the pump. It's way easier to plug in a car at home than to periodically visit a petrol station.

To say that either battery electric or petrol is superior in all use cases would be incorrect. It would probably also be incorrect to say that fossil fuels will be the dominant energy storage medium in the somewhat near future (my lifetime).

EV will be a great technology for things like delivery trucks since they make frequent stops, sit in traffic, and are constantly changing speeds.

[Hersbird]

Right they may be better for other reasons but I was just pointing out that a battery is a poor energy storage device in comparison to what is basically a natural product. That is amazing when you think about it. Our best design doesn't even reach 10% of nature's design, diesel.

[Fingie]

this is kinda wild.

i predicted electric powertrains would come in the future, yes, but in form of a undersized truck engine, coupled to a battery and electric motors would drive it.


in tesla semis,
regen braking would give quite well energy, if even the trailer had electric motors
hey, why don't have a smaller "power pack" in some trailers for extended trips? maybe even a cyclically-ran gas turbine for REALLY long trips?

[roflwaffle]

Originally Posted by Hersbird

But the battery is really has a poor amount of energy storage compared to the weight. A Tesla battery weighs what, 1200 pounds? That's 150 gallons of gas or on the other side a Tesla's 300 mile range would only require 8 gallons of gas or 65 pounds of fuel in a under 30 pound container, under 100 pounds total. That's what makes a great mobile source of energy, lots of energy in a light weight.

That sounds right. I think the Model 3 Long Range battery pack weighs a little under 1000lbs for about 65-70kWh of energy that can be put to the pavement, so the energy to weight ratio isn't great compared to gasoline/diesel, which only needs ~85lbs to deliver the same 65-70kWh (lower weight, but also lower efficiency).

At the same time, the power to weight ratio of an electric motor/diff is far higher than an ICE. The Model S drive unit is I think 300+lbs, and I imagine the Model 3 drive unit is around 250+lbs. A RWD ICE with similar power output/tractability is I think around 900lbs.

While the EV drive unit + battery is still a few hundred pounds heavier, some of that can be offset by needing less in the body for rigidity, and the end result is that the curb weight/performance/range of an EV can be pretty close to that of an ICE for higher power cars, eg a Model 3 compared to a BMW 3 series. That gap is much larger with small displacement cars because the engine/trans can weight half as much and they get better mileage, so the range on something like a Leaf is much lower than a Versa or similar.

[freebeard]

Electric battery packs exhaust their embodied energy without materially affecting their weight. They should be compared to 1/2 tank of fuel, which both Ford and Diesel felt should be sourced from hemp seed.

[Hersbird]

I was looking at a common 4 door a Honda accord and it's 4 cylinder Vtec and transmission weight being 405 pounds. Add another 100 pounds in cooling, fluids, exhaust. Then the 100 pounds of fuel and it's container. 600 pounds. How does that compare to the Tesla S battery, chargers, inverters, motor, etc? Seems the battery alone weighs more. I know to add a 16 kw·hr battery, controls, and motor to a Pacifica minivan with otherwise the same powertrain it's 600 pounds more. The battery is 368 pounds in that case and one of the best in specific energy at 100 W·h/kg for the total pack.

On the Tesla semi scale, a modern Cummins L8 weighs 1850 wet and accessorized, A class 8 transmission about 1000 pounds, and another 500 in cooling and exhaust or 3350 pounds. Even older semi motors, transmissions, accessories, only pushed maybe 4200 pounds tops.

From any of the estimates I see the Tesla semi will need at least 10 1200 pound packs meaning the batteries alone weigh 4 times the entire conventional semi drivetrain. That also means 8000-10000 pounds less cargo ability as many are pushed right up to the max allowed on the road, hence the need for so many weight stations out there.