Range reduction when towing.

[TyPope]

People say the sail sides will interfere, but I don't know if they thought of using CT lowered with a higher 5th wheel.
What is your clearance on the goose neck?
The bed can support/ haul 3500lbs. Why wouldn't it be strong enough to handle a 5th wheel?

It's high enough to get my head between the trailer and truck but not comfortably... Maybe 10-12". The 5th wheel hitch can be extended to fit a truck lower than mine while maintaining level. Actually, knowing the bed height of the CT would go a long way to knowing if I could use it. If it's lower than my F350, then I could see it being usable though it is a moot point if I can't get a hitch that uses the T-rail system to lock it in.

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[ajdelange]

Hey guys, have you heard anything about whether or not I'd be able to tow a 5th wheel trailer with the Cybertruck? ... 3rd party solution.

I think the answer turns on the 3rd party solution of which several have been discussed here. The only question in my mind is as to whether Tesla will approve attachment of these third party solutions to their vehicle and I think the answer is either that they will offer something themselves or work something out with the other guys, If you look into the CT TrMotor specs it is pretty clear that its principal design requirement was that it be able to tow a large trailer. 14,000 pounds is, IMO, a big trailer. Given that it seems certain that they will provide a means for hooking it up.

As to range: you are already aware that it's going to go down dramatically, perhaps as low as 100 miles in bad weather and with a positive grade. Your MPGe loss should be about the same with the CT as with the ICE truck so if you know what that is you'll have a rough idea of what to expect.

 

[TyPope]

I think the answer turns on the 3rd party solution of which several have been discussed here. The only question in my mind is as to whether Tesla will approve attachment of these third party solutions to their vehicle and I think the answer is either that they will offer something themselves or work something out with the other guys, If you look into the CT TrMotor specs it is pretty clear that its principal design requirement was that it be able to tow a large trailer. 14,000 pounds is, IMO, a big trailer. Given that it seems certain that they will provide a means for hooking it up.

As to range: you are already aware that it's going to go down dramatically, perhaps as low as 100 miles in bad weather and with a positive grade. Your MPGe loss should be about the same with the CT as with the ICE truck so if you know what that is you'll have a rough idea of what to expect.

I'm not so sure the loss will be as slight as it is when I tow with my diesel pick up. I go from 512 mile range to 416 miles of range. The CT is going to drop way more than the 18% that my diesel will. There was a video explaining why but I can neither access video from work (next week, I'm back at home) nor can I remember but the guy does a great job explaining everything from the amount of energy in a gallon of fuel, the losses from inefficiency there, and the corresponding energy in the expected battery. It was good an nerdy and I don't remember it.

 

[ajdelange]

The reasons are those I have been discussing here. If it takes Td Wh/mi to move the trailer against drag and its mass related loads total Tm and it takes Cd Wh/mi to move the CT against it's drag and Cm for its inertial load and Dd for the diesel's drag and Dm for its mass related loads the range reduction for the CT will be

(Cm+ Cd)/(Cm + Cd + Tm + Td) = 1/(1 + (Tm + Td)/(Cm + Cd) )

and for the diesel

(Dm + Dd)/ (Dm + Dd + Tm + Td) = 1 /(1 + (Tm + Td)/(Dm + Dd) )

The diesel is (1) more massive than the CT and (2) Cm is much reduced by regen so Dm is quite a bit bigger than Cm and lots of effort has gone into reducing Cd so (Dm + Dd) is going to be appreciably greater than (Cm + Cd), lets say three times (Tm + Td) whereas (Cm + Cd) might be twice (Tm + Td). Thus the diesel's range reduction will be reduced to

1/(1 + 2) = 1/3

whereas the CT's range reduction will be to

1/(1 + 3) = 1/4

of it's no trailer range. Thus it is apparent that you will see more of a fractional range reduction with the CT than with the diesel and the biggest factor will be the reduction of Cm. But before you concluding that the answer is to turn off regen keep in mind that this will result in a larger fraction of unloaded range being retained but that the unloaded range will be smaller and thus range achieved smaller than with regen on. I'd better stop here.

 

[SSonnentag]

Figure 60% range reduction, 200 miles vs 500 for the tri-motor, or 100 miles vs 250 for the single motor. EVs seem to take a much larger range hit than ICE when towing. I'm not sure why, but every instance I've seen and experienced shows this to be true.

 

[ajdelange]

The reason is given in the post just preceding yours (# 19).

 

[SSonnentag]

The reason is given in the post just preceding yours (# 19).

I read it, but I'm not sure I followed the formulas. In any case, my 1-ton Diesel dually would drop from 17 mpg to 12 mpg when towing a small, light, but very boxy enclosed trailer. Our Tesla Model X Wh/mile increased from 345 Wh/mi to around 700 Wh/mi pulling the same trailer.

Diesel shows a 30% drop in range while the X shows a 51% drop in range.

The front profiles and drag coefficients on these two vehicles are apple to oranges, so I'm not sure how much value there is in my comparison, but it's all the data I have to work with.

 

[ajdelange]

I keep forgetting that people in this country just hate math. So let's see if we can get at it without formulas. Let's suppose your diesel requires 600 Wh/mi to travel and the trailer requires 300. If you tow the trailer your total requirement is 600 + 300 = 900. For a given size of fuel tank it will take 900/600 times as much "gas" to get you however far you are going so your range, for whatever size fuel tank, will be 600/900 = 2/3 what it was.

Now suppose your BEV requires 300 Wh/mi. With the trailer your total requirement is now 300 + 300 = 600 and the rig with trailer thus requires 600/300 = 2 times the amount of "gas". For a given battery size your range will thus be 300/600 = 0.5 times what it was without the trailer.

With the diesel the tractors energy demand is large and the trailer thus represents a small percentage increase of the total. Range reduction isn't that great. With the BEV the tractor energy requirement is smaller and the trailer energy requirement thus larger relative to it. The reduction in range is thus greater when the trailer is added.

Your observations are interesting and useful.

 

[TyPope]

I keep forgetting that people in this country just hate math. So let's see if we can get at it without formulas. Let's suppose your diesel requires 600 Wh/mi to travel and the trailer requires 300. If you tow the trailer your total requirement is 600 + 300 = 900. For a given size of fuel tank it will take 900/600 times as much "gas" to get you however far you are going so your range, for whatever size fuel tank, will be 600/900 = 2/3 what it was.

Now suppose your BEV requires 300 Wh/mi. With the trailer your total requirement is now 300 + 300 = 600 and the rig with trailer thus requires 600/300 = 2 times the amount of "gas". For a given battery size your range will thus be 300/600 = 0.5 times what it was without the trailer.

With the diesel the tractors energy demand is large and the trailer thus represents a small percentage increase of the total. Range reduction isn't that great. With the BEV the tractor energy requirement is smaller and the trailer energy requirement thus larger relative to it. The reduction in range is thus greater when the trailer is added.

Your observations are interesting and useful.

I think that's the thing that people don't realize. The trailer has the same penalty regardless of what is pulling it. The Cybertruck has FAR less energy in its tank than an F-150 has in its tank. That is why towing with the Cybertruck will never be something as effortless as towing with a diesel. I'll look up the difference in energy "storage" that the Cybertruck should have as well as the F150 and post that in a second in an easy to see format.

Or, I'll do it right here.

The CT, with a 200KWH battery has, well, 200KWH of energy stored.
The F150 with a 32 gallon tank has 1200 Kwh of energy "stored". With 6 times the energy (but less efficient at using that energy), the F-150 will probably tow circles around the CT.

 

[ajdelange]

To put it more in the way I tried to in #23:
A)The diesel has a relatively huge tank - one big enough to grant it range of 600 or 700 miles compared to the CT's 500
B)As discussed in #23 less of the no trailering range,, on a fractional bases, will be lost to the diesel than to the CT because the diesel uses more energy per mile without a trailer than the CT.

Thus there are two effects at work.

 

[Dids]

I think that's the thing that people don't realize. The trailer has the same penalty regardless of what is pulling it. The Cybertruck has FAR less energy in its tank than an F-150 has in its tank. That is why towing with the Cybertruck will never be something as effortless as towing with a diesel. I'll look up the difference in energy "storage" that the Cybertruck should have as well as the F150 and post that in a second in an easy to see format.

Or, I'll do it right here.

The CT, with a 200KWH battery has, well, 200KWH of energy stored.
The F150 with a 32 gallon tank has 1200 Kwh of energy "stored". With 6 times the energy (but less efficient at using that energy), the F-150 will probably tow circles around the CT.

So the energy density of gasoline and diesel are nearly identical... And yet a diesel will tow the pants off a gasoline ICE. Energy doesn't move the load. Power does that and how the energy is turned into power is more important than efficiency.
Gasoline engines peak at 35% efficiency.
Diesels peak at about 40% efficiency.
So it's really only 5 % peak efficiency difference between the 2 fuel engines types.
But take a high efficiency gas motor and double the load and you will quickly discover that it is no longer efficient with greater than 50% loss on the efficiency. Double the load on the diesel and it's efficiency does not drop to 1/2.
If what aj says were true this shouldn't happen. The energy density of the fuels didn't change. It should take twice as much energy to move twice as much load.

There are 2 components of power ( the thing that actually moves the load). Energy is used to create the power. Power is rpm x force.
In a gas engine energy is turned into rpm with less force. It can go fast.
Here are 2 hypothetical gasoline engines, they are equally efficient and the energy density of the fuel is identical.
100hp = 2700rpm x 200 ft lbs torque
100hp= 1350rpm x 400 ft lbs torque
The first engine can move 200 lbs quickly. The second can move 400lbs more slowly.
Let's add 200 lbs load.
For the first the load has doubled. 100% increase.
For the second the load is 50% increase.
Do you really believe that the energy required for both these engines remains the same?

 

[TyPope]

So the energy density of gasoline and diesel are nearly identical... And yet a diesel will tow the pants off a gasoline ICE. Energy doesn't move the load. Power does that and how the energy is turned into power is more important than efficiency.
Gasoline engines peak at 35% efficiency.
Diesels peak at about 40% efficiency.
So it's really only 5 % peak efficiency difference between the 2 fuel engines types.
But take a high efficiency gas motor and double the load and you will quickly discover that it is no longer efficient with greater than 50% loss on the efficiency. Double the load on the diesel and it's efficiency does not drop to 1/2.
If what aj says were true this shouldn't happen. The energy density of the fuels didn't change. It should take twice as much energy to move twice as much load.

There are 2 components of power ( the thing that actually moves the load). Energy is used to create the power. Power is rpm x force.
In a gas engine energy is turned into rpm with less force. It can go fast.
Here are 2 hypothetical gasoline engines, they are equally efficient and the energy density of the fuel is identical.
100hp = 2700rpm x 200 ft lbs torque
100hp= 1350rpm x 400 ft lbs torque
The first engine can move 200 lbs quickly. The second can move 400lbs more slowly.
Let's add 200 lbs load.
For the first the load has doubled. 100% increase.
For the second the load is 50% increase.
Do you really believe that the energy required for both these engines remains the same?

Yes

 

[ajdelange]

Ohmygosh NO! To start with it is energy that moves the vehicle. To accelerate it from 0 to velocity v requires that m*v*v/2 units of energy be transferred to it. To move it up hill a distance h requires that m*g*h units of energy be transferred to it. To move it distance d against drag force F requires that d*F units of energy be transferred to it. When you go to buy a BEV you will be shown a Monroney sticker that tells you the average amount of energy required to drive a mile and as you are driving you will be presented with continuous updates on the energy used as the drive progresses. The units of energy we use are Watt hours per mile (Wh/mi) and are around 300 Wh/mi for the current Tesla vehicles and expected to be 400 - 450 for the CT. Thus if you drive 100 miles in a CT you will use 40000 to 45000 Watt hours written as 40.0 to 45 kWh (killowatt hour) of energy. Power is simply the rate at which energy is consumed, generated, transformed transferred etc. Thus if one drives 100 miles in 1 hour using 40 kWh of electricity the average rate of consumption which is the average power would be 40/1 = 40 kW. The unit of power that we use is the watt or killowatt.

There is no point in going over the other errors in the post you are agreeing with because they really don't relate to the reason that one sees a larger percentage decrease in towing range with a BEV relative to what he sees with a gasoline or diesel. That is completely explained in terms of the relative amounts of energy required to move trailer and tractor the required distance. If most of the fuel (energy) used while towing goes to move the tractor it should be clear that taking the trailer on and off won't have much of an effect on the range. Conversely if most of the fuel (energy) used in towing goes to move the trailer it should be clear that taking the trailer on and off would have a profound effect on range.

 

[TyPope]

Ohmygosh NO! To start with it is energy that moves the vehicle. To accelerate it from 0 to velocity v requires that m*v*v/2 units of energy be transferred to it. To move it up hill a distance h requires that m*g*h units of energy be transferred to it. To move it distance d against drag force F requires that d*F units of energy be transferred to it. When you go to buy a BEV you will be shown a Monroney sticker that tells you the average amount of energy required to drive a mile and as you are driving you will be presented with continuous updates on the energy used as the drive progresses. The units of energy we use are Watt hours per mile (Wh/mi) and are around 300 Wh/mi for the current Tesla vehicles and expected to be 400 - 450 for the CT. Thus if you drive 100 miles in a CT you will use 40000 to 45000 Watt hours written as 40.0 to 45 kWh (killowatt hour) of energy. Power is simply the rate at which energy is consumed, generated, transformed transferred etc. Thus if one drives 100 miles in 1 hour using 40 kWh of electricity the average rate of consumption which is the average power would be 40/1 = 40 kW. The unit of power that we use is the watt or killowatt.

There is no point in going over the other errors in the post you are agreeing with because they really don't relate to the reason that one sees a larger percentage decrease in towing range with a BEV relative to what he sees with a gasoline or diesel. That is completely explained in terms of the relative amounts of energy required to move trailer and tractor the required distance. If most of the fuel (energy) used while towing goes to move the tractor it should be clear that taking the trailer on and off won't have much of an effect on the range. Conversely if most of the fuel (energy) used in towing goes to move the trailer it should be clear that taking the trailer on and off would have a profound effect on range.

It'll take the same amount of energy to move the trailer whether BEV or ICE if I understand correctly. The CT will likely have a 200 kWh battery. The F-150 with a 32 gallon tank (33.7 KwH per gallon) will have about 1200 kWh of energy stored in the gas. The ICE isn't as efficient as the CT which is why the range is so close... 500 miles for the CT, 620ish for the F150. It's when you tow that the ICE catches up. At least that's what the guy explaining it in the video said: Can it tow?

It made sense watching it but if you are saying he's wrong, how so? I don't understand...

 

[ajdelange]

Let's say it takes 400 Wh/mi to move the CT and 600 Wh/mi to move the trailer. Let's suppose the CT to be 95% efficient. The energy from the battery required to go a mile is then 400/.95 = 421 Wh/mi and for the trailer is 600/0.95 = 632 Wh/mi. Whatever the size of the battery is I can go
(421 + 632)/421 times farther without the trailer than I can with. Divide numerator and denominator by 421 and that ratio becomes (1 + 632/421). Note that is numerically equal to (1 + (600/.95)/(400/.95) ) = (1 + 600/400) because the efficiencies cancel out. Thus if it takes 400 Wh/mi to move the CT and 600 to move the trailer you can go 1 + 6/4 = 10/4 farther without the trailer than you can with and conversely adding the trailer will reduce the vehicle's range to 4/10 of what it is when not towing irrespective of what the battery size is or how efficiently the CT converts its fuel to energy delivered to the vehicle.

Now doing exactly the same for an ICE vehicle we get the same result which again does not depend on the efficiency of the engine nor on the size of the gas tank. We may suppose that a big diesel weighs more than the CT and that less attention is paid to drag reduction so that the Wh/mi are somewhat higher than for the CT. Lets say its consumption is 500 Wh/mi as opposed to the CT. Then the factor becomes 1 + 500/600 = 1 + 5/6 and the reduction in range is by the reciprocal of that to 6/11 = 0.54 which is a larger fraction. Than 0.4. The other aspect of this is that the ICE vehicle has more fuel on board up to 800 miles worth in some cases. 0.54*800 = 432 is a bigger number than 0.4*500 = 200 thus the ICE vehicle is "better" for towing if your criterion of goodness is range between fueling stops. If, OTOH, it is emissions reduction and energy efficiency the BEV is much better.

In No. 28 I responded to your "Yes' in No. 27 which came right after No. 26 leading me to believe that you were agreeing with that post. I didn't realize that you were referring to the video in No. 14. There is nothing wrong with what he says in the video. The guy is an engineer and he clearly understands the physics. The only problem I find with the video is that he goes all around cock robin's barn calculating energies to come to the same conclusion which the much simpler analysis set out here takes us to more quickley.