Engineering Explained: F-150 better than Cybertruck for towing duty (over distance)

[ajdelange]

I said that any range estimates I would give would be exceeding crude and I'll continue to hide behind that statement. If we assume that rolling resistance is 20% of consumption (as I did before) and that the CT's consumption un burdened is 485 that implies drag consumption of the CT is 388 Wh/mi. Putting the trailer's drag at 5 times that gives it consumption of 1940 for drag. Our assumption assigned 97 Wh/mi to rolling resistance and we might assume the trailer's rolling resistance consumes twice that as it weighs twice as much (we're still talking the huge 5th wheel rig here) or about 200 Wh/mi. That gives 1940 + 200 = 2140 for the trailer to which must be added the 485 for the CT itself meaning a total consumption o f 2625 Wh/mi. This is 5.4 times the demand for the truck alone and range will thus be less that 1/5th (18.5%) of the CT by itself. For the 500 mi rang model that's 92 miles. But this is also a very crude estimate. Someone who has one of these and want's to get an idea should go out and measure the increase in fuel consumption per mile with his current ICE truck. The measurement won't exactly match what's going to happen with the CT but factors of 5 would certainly be detected.

Note that there are "aerodynamic" trailers made such as the one that I mentioned in #12.

Also note that the towing vehicle shields the trailer to some extent.

Do keep in mind that there are other consumers of energy (transmission loss, bearing loss, slip loss) so that wh/mi vs speed does not go as the square of speed as these other forces tend to swamp drag.

Sponsored

 

[ajdelange]

The more fuel you burn (ie towing and/or if you drive a lot) .. the more money you save using an EV. Simple.

Not if you are recharging at EA stations.

 

[Rancherort]

The biggest issue I see is Tesla constantly avoiding the subject. The model x with even a moderate load drops to 40% of its range. Unless the CT has some crazy new motor or battery design I don't see any advantage or efficiency increase while it's towing. I expect it to lose electrons like crazy when a trailer gets hooked to it. Of course Tesla isn't or wont release that info.

 

[ajdelange]

The biggest issue I see is Tesla constantly avoiding the subject. The model x with even a moderate load drops to 40% of its range.

The Model X which requires about 300 Wh/mi has its range reduced to 40% of its nominal range when the trailer load is 0.6*300/.4 = 485 Wh/mi i.e about 1.62% times as much as the X. Is that a moderate load? Consider towing another x. We know that that takes about 300 wH/mi more and that the range would, therefore, be about half. That's a 5500 pound load. Is that moderate? Yes, compared to a 14,000 lb 5th wheel trailer but there are pretty nice camping trailers which weigh less than half of 5500 lbs. I think we can presume that they would not reduce range to less than 50%.

I have a moderate sized trailer (big enough to haul furniture from Virginia to Quebec. Changes in gas mileage with my Lexus suggests that it takes about 80 Wh/mi to pull this thing. Call it 100 Wh/mi. It would reduce the range of the X to 300/(300 + 100) = 75%. To find out I would have to actually pull it behind the X. I would expect to find consumption up to 400 Wh/mi but I wouldn't expect it to be much different than that.

Unless the CT has some crazy new motor or battery design I don't see any advantage or efficiency increase while it's towing.

No because as I keep trying to make clear the only thing with a major effect on towing range is the power required to move the load relative to the size of the ""gas tank" on the truck. Improving the efficiency of the CT to 95% from the X's 90% isn't going to make an appreciable difference. Going from a 100 kWh battery to a 225 kWh battery is.

I expect it to lose electrons like crazy when a trailer gets hooked to it. Of course Tesla isn't or wont release that info.

You may not understand the physics but Tesla does. They can tell you what the towing range reduction will be if you tell them what the trailer's weight and consumption are. Until they know that they cannot do the calculations and would be fools to throw out numbers based on the simplistic assumptions one is forced to make without that data.

 

[Garden_Aum]

The biggest issue I see is Tesla constantly avoiding the subject. The model x with even a moderate load drops to 40% of its range. Unless the CT has some crazy new motor or battery design I don't see any advantage or efficiency increase while it's towing. I expect it to lose electrons like crazy when a trailer gets hooked to it. Of course Tesla isn't or wont release that info.

I do not know if it is a "isn't or won't" situation with the towing range. I doubt they have the real world data at this time. I hope as they prepare for a final production design they test the CT in a range of conditions and then release the data. They should also test ICE counterparts so that there is something to compare the numbers of the CT to.

 

[Rancherort]

My experience with my own trucks is around 45% loss or so towing a 5000lb car and hauler combo. It really depends on terrain. Tesla had little to say for inquiries into the model x's towing range. The problem i see is that an extended range battery is a must on the dual motor CT.

 

[ajdelange]

My experience with my own trucks is around 45% loss or so towing a 5000lb car and hauler combo.

Seems reasonable. The range will be reduced to r = 1/(1 + T/W) where T is the energy required to tow whatever it is that is being towed some distance (1 mile) and W is the energy required to move the vehicle alone that same distance. If you tow an X behind an X T = W and the towing reduction factor is 0.5.

It really depends on terrain.

Yes it really does. I just found out from another thread that 85% of the people here do not have BEVs. BEV operators are very conscious of the effects of terrain and weather on W and range, Range, R, is R = Usable_battery/ W. For the X, as an example, the battery size is about 100 kWh and W about 0.33 kWh/mi for R = 300 miles. If it rains, and not even very hard, W can shoot up to over 400 and range goes down to around 220 miles. That's without the trailer. Range reduction with rain is caused by the extra energy required of the tyres to push water out of the way and water is actually pretty thick stuff. The trailer has tyres too and so both T and W will go up - approximately to the same extent so that T/W is about the same as is r. But now r is applied to the 220 miles reduced range, not the nominal 300 mile EPA range for an X (pre Raven) and you have probable range of 110 miles towing another X in the rain as compared to 150 miles towing it dry. Cold weather, headwinds, rough road surface, loose gravel, and especially grade have an effect. Then recognize that we are usually comfortable using only 80% of the battery's available capacity (we don't charge from 0 to 100%) thus practical range to tow an X with an X might be 120 miles in dry weather on flat terrain but only perhaps 88 miles if it is raining. Going up hill really eats your lunch.

Tesla had little to say for inquiries into the model x's towing range.

What would you expect them to say? What you experience depends on the trailer (T), the oonditions under which you drive it and your driving habits. All Tesla knows is W and the battery size.

You can, of course, get a rough idea as to what T might be by noting the reduction in range experienced in towing a trailer of interest behind a vehicle for which you know W. It is too bad the guys that made the videos linked in this thread didn't understand this. They made no effort to measure W which they could have done very simply. I found out in the course of investigating this this that truck manufacturers are not required to publish mpg numbers so I couldn't even WAG W values!

The problem i see is that an extended range battery is a must on the dual motor CT.

A load equal to the car's load (T = W) reduces range to 50%. With a nominal range of 500 mi and a practical range of 80% of this we have a potential ability to tow 200 miles under good circumstances recognizing that this might go down to 150 or even less under unfavorable ones and this might be acceptable. And we might suppose that trailers weighing less that the truck itself might require T < W and might be suitable for towing. The decision rests with the buyer.

OTOH if the nominal range is of the vehicle is 300 miles the picture isn't so rosy. Nor is it so rosy for trailers that weigh more than the truck (T > W).
So yes, a small battery in the CT implying a small nominal range (relative to 500 miles) is a problem which could ostensibly be solved by installing a bigger one. But there is more to it than that. The third motor in the 500 mile CT means more available power to accelerate and decellerate the larger total loads associated with towing.

The real problem is that people are relying for guidance on this on folks like the two guys in the videos who clearly don't understand the physics very well. And I guess we might say that the problem is that the problem is complicated enough that some technical background is necessary to understand it. And even those who do can't really make solid predictions because sufficient data is unavailable. The only way I can tell you with any certainty what will happen if you pull a 14,000 lb 5th wheel behind a CT is to get one of each, install the hardware in the bed of the truck and start taking measurements. I''m not likely to do that as common sense and some crude engineering estimates don't suggest that success is likely. But someone will probably eventually do it and then we'll know.

 

[CarsBarsMars]

Skip to the end to avoid two paragraphs of exposition on why I have my opinon......lol.

IMHO as a guy who tows several different trailers weekly, and who usually has a utility trailer behind me about half the work day, you should not buy the CT if your life is trailer heavy unless Tesla makes a trailer with an onboard battery pack. I am not making an anti-EV statement here, just a practical observation that trailering for most people is a very very part time gig and if they are really worried about their ability to tow a 10,000 pound trailer from a hitch receiver for an annual vacation to Florida they should look into renting a truck for the trip. I used to be the guy with the full size v-8 family hauler and the 28 foot trailer full of camping crap out on the expressway living the american dream. That was 2000 out of 18000 miles I drove every year and the rest of the time I was hauling around a ton of extra vehicle that served absolutely no purpose except to keep my mpg around 9 in the kind of city driving I do. I currently drive a mid-size Lexus that I use to tow trailers when I need truck like capacity for work, and it's a much better solution than a full size pickup.

However the CT is just too much the car I have always wanted (since Jeep decided a Gladiator should cost $50,000 wtf) so I am telling myself that increased efficiency justifys the extra 4000 pounds of vehicle. Also, I plan to keep the lexus since I've painted all my trailers to match it and it's honestly the best truck I've ever owned. I'll use the CT for everything else.

So in my opinion, based on lots of real world trailering, is that you do not want an electric vehicle as a frequent trailer tractor. You will never get anything like consistent power use or predictable power use with a trailer attached unless you're on the expressway in a flat part of the country. I would not be frightened about hitching up a cargo trailer to run to the lumber yard or to pick up cabinets. However I would not buy a CT thinking it's going to be my new lifestyle vehicle where i hook up my 9000 pound (dont actually have one) boat and run to the lake every weekend. I am not sure I'd back a CT down a boat launch in any condition....lol. If you start adding up the load, trailer, people, camping gear, AC, iPads, frequent exit and entry ramps for rest stops, wind conditions, traffic, you might find that in a real world long range trailering situation you'll get 25% of the potential max unloaded range. Just my opinion.

 

[ajdelange]

So in my opinion, based on lots of real world trailering, is that you do not want an electric vehicle as a frequent trailer tractor. You will never get anything like consistent power use or predictable power use with a trailer attached unless you're on the expressway in a flat part of the country.

In what way does the fact that the vehicle is electric make things any different from what they would be with an ICE vehicle?

 

[ajdelange]

I haven't run out of coulombs yet but I have run out of gas. Thus I dismiss range anxiety.

The answer I was looking for is in the last paragraph: you can get a bigger gas tank on an ICE vehicle.

Thus the person considering towing with a BEV needs to do the same thinking as a guy contemplating towing with an ICE truck.

Keep in mind Rivian's patent for the electric jerry can.

Sponsored