Engineering Explained:Why Tesla's Are Bad at Towing

[teoman]

Theoretically all batteries with the same Chemistry andC rating change at the same time (if you are capable of supplying the amps. From drone batteries to car batteries.

If expense and weight was not an obstacle, then having a massive battery would be a solution to the charge time problem. You have to stop ever so often, and when you do, you could dump enough kwh to drive several hours as fast as pumping gasoline.

[redpoint5]

In my Prius, I can add about 500 miles of range in 1 minute.

To do that with electricity would be roughly 7,500,000 watts. That's 7.5 megawatts of power to put 500 miles of range into a battery in 1 minute. It would be like 6250 homes appearing on the grid out of nowhere all of a sudden.

The batteries are a major limiting factor, but the chargers themselves are another limiting factor.

[Bajascoob]

A Tesla you can start to “fill” walk away, take a pee, grab a drink maybe a snack, jump back in and leave...you don’t have to stand there, park, take a pee...etc. most people don’t have a 400mile bladder.

[slowmover]

“Steady state” is all to the good in figuring HP draw. The problem is
maximizing steady state.

1). Few are the trips when towing where accel/decel events aren’t the definitory problem.

2). Whether traffic congestion or terrain, the amount of time spent opened-throttle is where the fuel reserves disappear. The only time weight matters. But IT MATTERS A GREAT DEAL,
(why empty car stunt driving has nothing to do with fuel economy despite general belief).

How to get the load to speed

How to maintain steady-state

How to minimize braking

And to do it all in a way which MAXIMIZES safety (never otherwise), will be the big difference between otherwise comparable rigs.

In commercial work, where the ONLY difference is the driver, it’s as much as a One-Third penalty between best & worst drivers. Completely about accel/decel.

The amount of time spent steady-state (engine Hours) is surprisingly lower than expected no matter the day’s total miles.

(Whine) “It’s too much work”.

“I be gettin’ runned over!!”

Etc

Half the trip — even Interstate — can be other than steady state (cruise control as definition).

Where aero REALLY matters is in handling crosswinds. These are natural AND man-made. They can be constant. Which means yet more juice to maintain headway.

But, who is the operator? Is he towing something to make his living? That’s both incentive and disincentive to maximize aero qualities. They aren’t “qualities” for a contractor covering a large metro area if “aero” reduces on-site efficiency.

As I’ve posted before — and will continue — an empty vehicle MPG is just noise. Tells us nothing worth knowing. Until proficiency in moving a FULLY loaded vehicle comprises a high proportion of annual miles, HOW to estimate, calculate towing fuel use is in the dark.

1970 or 2020 the baseline starting point for travel trailer towing is a 40% penalty. This is constant. No matter how “good” one is with the tow vehicle loaded 80%+, 40% is a fair minimum.

It’s a good deal higher (increases rapidly) with road problems of climate, terrain and congestion.

Be clear about use.

Tractor-trailers APPEAR to be a model. But how many of you expect that electric vehicle towing will be from one large metro to another, nation-wide.

Optimized conditions with experienced, motivated operator doesn’t come about motoring to & from a single metro region. One must be a minimum of 75-miles from city center before traffic spaces out.

How many miles will you cover past that point, or returning is where aero FINALLY reaches potential. And that’s assuming no adverse weather.

I see that the argument there’s no difference in power-plants. I’d recommend you read those who are towing with Tesla sedans. Electric can get penalized by virtue of what it is. Where comparative power draw is simply higher. Demand creates resistance.

The theoretical load isn’t higher, so that’s the point here. Better more carefully check the hypothetical underpinnings. Assumptions.

With diesel versus gasoline, towing MPG comes down to cylinder pressure. Highest = Winner. Every time. As it’s those transitions (degree & duration) that tell the black box story.

In ancient days — besides adding tachometer, vacuum gauge & fuel flow meter — the savvy added an airspeed indicator to modify throttle inputs versus travel set speed.

Towing an aero-inefficient load, weight & winds both matter. A CAT Scale ticket, and knowing prevailing winds foot-by-foot are the only way past NOT having a turbocharged diesel.

The only RELEVANT practice while solo is with a load factor of 85%. Aero matters little without the trailer. It’s fixed. Knowing how to maintain the glide, is the thing, and can’t be done empty.

.

.

[MeteorGray]

Originally Posted by Bajascoob

A Tesla you can start to “fill” walk away, take a pee, grab a drink maybe a snack, jump back in and leave...you don’t have to stand there, park, take a pee...etc. most people don’t have a 400mile bladder.

A Tesla will yield 400 miles on a 15 minute charge?

[freebeard]

Originally Posted by slowmover

Electric can get penalized by virtue of what it is. Where comparative power draw is simply higher. Demand creates resistance.

If we're talking about P=I/E keep in mind that it's polyphase DC, so resistance becomes reluctance.

What is Magnetic Reluctance - definition - Circuit Globe
[Search domain circuitglobe.com/what-is-magnetic-reluctance.html]
Definition: The obstruction offered by a magnetic circuit to the magnetic flux is known as reluctance. As in electric circuit, there is resistance similarly in the magnetic circuit, there is a reluctance, but resistance in an electrical circuit dissipates the electric energy and the reluctance in magnetic circuit stores the magnetic energy.

[ldjessee00]

I think that the Tesla Semi will have informed Tesla and its engineers a lot about towing and how to handle many of these issues, just like building and getting data back from the Model S and X informed them how to build the Model 3, which then was rolled back into (or will be) the Model S and X (the Model 3 reluctance motor).

As they learn more from the practicals of running a semi from San Francisco to Nevada and back, I am sure they learned exactly what it will take to run an electric Semi from one city to the next... my question is why? Trains do heavy, long haul cargo better than trucks. They have smoother roads, usually the terrain (grades, curves, tunnels, etc) has been setup to be less dramatic than highways.

Anyway, if you want to haul something with an EV, there will be solutions. Look back to when automobiles first came out. If you wanted to get a load over a mountain, in bad weather, you did not use an auto, you used horses, mules, and/or donkeys. Most cars got stuck and when they did, it was one of these animals that pulled them out.

Now we are transitioning from fuel burning in ICE to batteries and electric motors. There will be segments that will say EVs will never compete with ICE... until that is not true any more. Will that be in 5 years or 10 years? Depends on the battery tech that Tesla has been paying lots of researchers to work on the last few years... and other people trying to find new battery tech to compete with Tesla. As more and more money gets poured in to this research, the more niches EVs can fill, until it is just impractical for most people to even own an ICE.

Just as some people still ride horses, some people will still operate ICE vehicles. People still read papers and listen to radio... older technologies don't just go away, sometimes they find a new niche or become hobbies.

I agree it could be so much better and every time I see the flat backend of a semi trailer, it just makes me cringe. Some of the aero forms and flaps that are added to the back help some, but I think the industry will need to adopt a standard form that is more compatible with an aerodynamic shape. Even if it is for diesel or hydrogen semis, they will need the increase in efficiency... or someone will realize that trains are just so much cheaper and money will go into developing trains (adopting some of the tech from Europe and Asia, since they have continued to invest in trains)...

[redpoint5]

Originally Posted by ldjessee00

Now we are transitioning from fuel burning in ICE to batteries and electric motors. There will be segments that will say EVs will never compete with ICE... until that is not true any more. Will that be in 5 years or 10 years? Depends on the battery tech that Tesla has been paying lots of researchers to work on the last few years... and other people trying to find new battery tech to compete with Tesla. As more and more money gets poured in to this research, the more niches EVs can fill, until it is just impractical for most people to even own an ICE.

Are we transitioning? I think it will happen, but 1% of vehicle sales is hardly a transition.

It's a myth to think that money spent = results. The fact that money is invested to improve technology is no guarantee that it will pay off. Look at US healthcare vs dollars spent. Look at US education vs dollars spent. Look at cancer research for "the cure". The universe has placed limitations on us, and you can't buy your way out of that.

I agree it could be so much better and every time I see the flat backend of a semi trailer, it just makes me cringe. Some of the aero forms and flaps that are added to the back help some, but I think the industry will need to adopt a standard form that is more compatible with an aerodynamic shape. Even if it is for diesel or hydrogen semis, they will need the increase in efficiency... or someone will realize that trains are just so much cheaper and money will go into developing trains (adopting some of the tech from Europe and Asia, since they have continued to invest in trains)...

Tractor/trailers aren't made to slip through the air; they are made to move cargo. That cargo comes on pallets. Pallets are square. The trailer has to interface with a loading dock... all this to say there is room for improvement, but solutions have to keep in mind the purpose in the first place, which is to move stuff.

Trains in the US might be fine for certain routes, but you always have to have trucks to move stuff to warehouses, and then from warehouses to stores. Ever look at train ticket prices to travel? They are comparable in price to airline travel yet much slower... and that's the subsidized price. If air travel is better, why would moving cargo via train be any better?

[freebeard]

The trailer has to interface with a loading dock... all this to say there is room for improvement, but solutions have to keep in mind the purpose in the first place, which is to move stuff.

Plasma actuators.

[ldjessee00]

[

Originally Posted by redpoint5

Are we transitioning? I think it will happen, but 1% of vehicle sales is hardly a transition.

It's a myth to think that money spent = results. The fact that money is invested to improve technology is no guarantee that it will pay off. Look at US healthcare vs dollars spent. Look at US education vs dollars spent. Look at cancer research for "the cure". The universe has placed limitations on us, and you can't buy your way out of that.



Tractor/trailers aren't made to slip through the air; they are made to move cargo. That cargo comes on pallets. Pallets are square. The trailer has to interface with a loading dock... all this to say there is room for improvement, but solutions have to keep in mind the purpose in the first place, which is to move stuff.

Trains in the US might be fine for certain routes, but you always have to have trucks to move stuff to warehouses, and then from warehouses to stores. Ever look at train ticket prices to travel? They are comparable in price to airline travel yet much slower... and that's the subsidized price. If air travel is better, why would moving cargo via train be any better?

1% of US Sales, world wide sales, or something else? Not sure what your 1% number is referring to. I know in some countries, it is now over 50% of sales. (Norway)

How do you think a transition from ICE to BEV will look like? That during a transition, it would not start at a low percentage and build? And that some where during that transition it will have still less sales, but more and more manufacturers make more models available in some electrified format?

Sure the Jeep Wrangler plugin hybrid is pretty weak, but still they are making it, something some people thought would never happen...

Money spent with no guidance, limits, goals, or guiding force will result in nothing but spent money. But as companies invest in battery technology because batteries are driving so many consumer electronics right now, any advancement would be a huge payday. So, this keeps companies investing, but it has to show promise, improvements, and technology does advance. If you had not noticed, the pace of change has picked up lately.

If you want to talk about what is wrong with the US Healthcare and cancer research, I have some ideas, but that is not relevant to EVs.

Cargo goes on planes as well, and there the cargo is not always on palettes, sometimes it is in funky shaped boxes to match the curvature of the plane.

Semis have to move cargo cost effectively, which will mean competing with other forms of transport.

RE: Docks
Are you trying to be funny? I mean, the trucks will have to be used on roads as well... is that a reason it cannot be aerodynamic? Also true with docks.

There are planes that have flip-up noses, swing up or to the side tails, and there are trains that load from the side very quickly... It is kind of shocking when you look into it, you can find all kinds of examples of how to move cargo into and out of a vehicle that is aerodynamic. And some of them could even be adapted to tractor-trailers.

All warehouses used to all be on train spikes and trucks were only for local distribution...but that is not true anymore here in the US, but world wide... well, some countries kept up on keeping train technology up to date, so train is faster, cheaper, and a better way to travel in many countries.

Passenger train travel in the US is not even comparable to how competitive cargo rail. Here is a report on Train cost for cargo.

Air travel is only better for some because of the speed. If I wanted to ship iron ore or coal, by air hardly makes any sense.

Weight, density, and priority are all factors now.