Cybertruck Towing Range

[eaglefire]

What are your thoughts on the estimated range while towing with the Cybertruck?> I pre-ordered the 3 motor AWD and am hoping to use it to tow a 10,000 lbs travel trailer. I'm hoping to get 200 miles range while towing, Just hope this isn't too optimistic for an EV.

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[ajdelange]

This is a popular question at the moment and is addressed in at least a couple of threads. What happens to the towing range depends on the trailer - not the truck (for the most part). Thus we cannot answer the question other than to say that for a trimotor CT to be able to tow a trailer 200 miles the trailer must require 0.6*485/.4 = 727.5 Wh/mi or less to move on level ground. Does your 10,000 lb trailer require less than that?

 

[eaglefire]

This is a popular question at the moment and is addressed in at least a couple of threads. What happens to the towing range depends on the trailer - not the truck (for the most part). Thus we cannot answer the question other than to say that for a trimotor CT to be able to tow a trailer 200 miles the trailer must require 0.6*485/.4 = 727.5 Wh/mi or less to move on level ground. Does your 10,000 lb trailer require less than that?

Thank you for the insight. I'm not sure how to determine Wh/mi requirement but absolutely appreciate you sharing your expertise. I'm looking to tow a 30 foot Airstream travel trailer with a weight of 10,000 pounds. Any extra guidance you can share would be much appreciated. Thanks

 

[ajdelange]

The basic math is that the nominal range of a vehicle is the size of the "gas" tank divided by the amount of "gas" used to go 1 mile;

Rn = S/W

For the 3 motor CT W is estimated at .485 kWh/mi and, if that's correct, the size of the battery required for 500 mi nominal range is 242.5 kWh. If an extra load, such as a trailer, is involved, range is reduced to

R = S/(W + T)

where T is the energy required to pull the extra load 1 mile. Dividing numerator and denominator by W, the power required by the truck, we get

R = (S/W)/(1 + T/W) = Rn/( 1 + T/W)

Thus range is reduced by the factor (1 + T/W). W is easily obtained. It is the EPA rated energy consumption. If we also know T then it's easy to estimate the range. But we don't and the only recourse we have is to guess what T might be. In the case of a 10,000 pound trailer we observe that it certainly weighs more than the truck which we estimate will weigh between 6,000 and 7,000 pounds. From this it is certain that T > W, perhaps appreciably so. But let's start by assuming that T = W. For that most optimistic case we find R = Rn/2. The range is cut in half. If T is 10% greater than W then R = 48% of Rn and if T is 1.5*W then the range is only 40% of the range of the vehicle alone. Beyond this we can use more sophisticated techniques to try to estimate T such as by guessing at drag and rolling resistance for the trailer based on its dimensions and weight but one is really going out on a limb doing this.

Note that the formulas given above are independent to the type of vehicle and "gas". Thus you can expect that the range reduction you will see in your CT when towing the trailer will be, as a fraction, about the same as you observe through your gas mileage with the ICE truck you currently pull it with. IOW if your unburdened gas mileage is 15 mpg but drops to 7.5 mpg with the trailer you should expect to see about a 50% decrease in range with the CT too.

Ten thousand pounds is a big trailer for sure but you might get 200 mi from the trimotor CT when towing it under ideal conditions. If you are new to EVs you many not be aware of the sensitivity of Rn to things like grade, rain, snow, cold weather and winds. Thus 500 mi EPA rated range could turn into under 400 from nothing more than a rain shower or driving into a stiff breeze. Also keep in mind that we typically operate our BEVs between say 10% and 90% SoC such that the nominal practical range of the 500 mile CT would be 400 mi.

 

[eaglefire]

Great information. Thank you so much!

 

[Etchhead]

Very educational! I towed a lot with my F350 and 8k trailer and can vouch for the >50% range hit. Now Tesla needs to figure out a few options for charging a CT with Trailer attached OR have a lot nearby to unhook.

 

[ajdelange]

They know perfectly well how to do it. They just don't build many stalls that allow it.

 

[Garden_Aum]

I have been thinking a lot about road trips in the CT. My wife and I have been using different EV trip planning websites and have discovered that some of the more remote locations we would like to visit (i.e. Newfoundland) pose a serious challenge when traveling there using an EV. So, I decided to change my CT order from a dual motor to tri-motor. The benefit of having an additional 200 miles of range makes us both more comfortable especially when we will be pulling a trailer.

 

[eaglefire]

I have been thinking a lot about road trips in the CT. My wife and I have been using different EV trip planning websites and have discovered that some of the more remote locations we would like to visit (i.e. Newfoundland) pose a serious challenge when traveling there using an EV. So, I decided to change my CT order from a dual motor to tri-motor. The benefit of having an additional 200 miles of range makes us both more comfortable especially when we will be pulling a trailer.

Good insight. I'm glad I went with the tri-motor too for similar reasons. I'm really hoping to get a good 200 mile range while towing a 10,000 lb Airsteam with the tri-motor. The CT may not be practical if it can't tow a travel trailer at least 200 miles between charges.

 

[HiTeKReDNeK]

I have seen lots of commentary on this. The one thing I have not seen considered in the calculations is the amount of Range recovered with regenerative braking. Particularly when you are going downhill with the trailer.

Even the YouTube group TFLT knuckleheads noted a tremendous amount of regeneration when going downhill with trailer.

I think that we have to wait until we see the specs and, more importantly, the advancements they have made which will hopefully be revealed on battery/powertrain investors day in early 2020 from Tesla.

 

[Garden_Aum]

I have seen lots of commentary on this. The one thing I have not seen considered in the calculations is the amount of Range recovered with regenerative braking. Particularly when you are going downhill with the trailer.

Even the YouTube group TFLT knuckleheads noted a tremendous amount of regeneration when going downhill with trailer.

I think that we have to wait until we see the specs and, more importantly, the advancements they have made which will hopefully be revealed on battery/powertrain investors day in early 2020 from Tesla.

I have experienced regeneration with my current car; it does add a surprising amount of power back into a battery. The concern I have is with aerodynamic drag while driving in relatively flat areas. One of my life goals is to drive coast to coast in Canada. I plan on executing this trip soon after getting the CT. It is going to be done in stages. The first stage is the eastern most portion of the country where there is not a lot of charging infrastructure at this time. The second stage would be from Ontario to Alberta. When I was playing with route planning software, it had sections that would require speed reductions to make to the next charging location. It was at that time that I came to the conclusion that there would be no way to make the trip in the dual motor CT while pulling a small trailer so, I changed my order to the tri-motor. I am glad that I had the option to make the change while maintaining my order number. I am also grateful that we have a good community of contributors on this forum. The discussions and questions have been very helpful.

 

[CyberDoc]

Battery pack in Tesla trailer would enable full range while towing

 

[eaglefire]

Battery pack in Tesla trailer would enable full range while towing

I plan to tow an Airstream Travel Trailer that weights 10,000 lbs. A special Tesla cargo trailer has no function for my needs. I'm hoping to learn towing range for RV use.

 

[CyberDoc]

I plan to tow an Airstream Travel Trailer that weights 10,000 lbs. A special Tesla cargo trailer has no function for my needs. I'm hoping to learn towing range for RV use.

Fair enough but I wish Tesla would create their own travel trailers complete with their own 1 or 2 hundred KWh battery packs.

I can understand about using what you already have, though.

 

[ajdelange]

I have seen lots of commentary on this. The one thing I have not seen considered in the calculations is the amount of Range recovered with regenerative braking.

The formula given in #4:

R = Rn/( 1 + T/W)

includes the effects of regeneration as long as T and W are consumptions determined when regeneration is taking place. So, for example, if W is the consumption the odometer gave for the summer months it includes the effects of the regeneration you harvested during the summer months.

Kinnetic Energy: When a vehicle of mass m is accelerated from velocity v to v + ∆V its kinetic energy increases by (1/2)*m*(2*v*∆v + ∆v*∆v). When is is slowed back to v it loses an equal amount of energy. The energy required from the battery is larger than this because the PWM and motor are not 100% efficient. Lets say 1.1*(1/2)*m*(2*v*∆v + ∆v*∆v). When the car slows the motors act as generators, also less than 100% efficient, and so the energy returned to the battery is, say, 0.9*(1/2)*m*(2*v*∆v + ∆v*∆v). Thus there is an energy loss, for the assumed motor and generator efficiencies, of 0.2*(1/2)*m*(2*v*∆v + ∆v*∆v) for each acceleration of ∆v from velocity v. What this means is that if you drive 10 miles and traffic requires you to accelerate and decellerate 10 times you will lose twice as much energy to regeneration inefficiency as if you only have to speed up and slow down 5 times.

Potential Energy: When a vehicle of mass m is raised from an elevation of h to h + ∆h its potential energy is increased by m*g*∆h were g is the gravitational constant. If the vehicle rolls the same distance down hill its potential energy is decreased by that amount, As with kinetic energy it takes more battery energy to raise it. Assuming the same factor we require 1.1*m*g*∆h to go ∆h uphill. Rolling back down only 90% of that gets returned to the battery so we have a potential energy regeneration loss of 0.2*g*∆h for going up and down a hill ∆h high. As is the case with kinetic energy, the amount of loss for going up and down hill depends on the number of times you must do it in the distance driven. There is major difference with potential energy, though.

Let us rewrite W as W = Wd + Wk + Wp + Wh i.e. as the sum of Wd, watt hours per mile not associated with vehicle energy such as for drag, Wk, those required for kinetic energy regeneration loss and Wp, those required for potential energy regeneration loss. We require a fourth term because unlike with kinetic energy where we always start a trip at the same velocity, v = 0, we may start and end trips at different elevations. Wh is the watt hours per mile required to raise or lower the vehicle between those elevations. Wh = k*m*g*(h2-h1)/d where d is the distance driven. h2 - h1 is the difference in alitude and must be in miles, as must d, if we want Wh/m. That's easily obtained by dividing (h2 - h1) in feet by 5280. k = 0.9 if h2 < h1 and 1.1 if h2 > h1. If the mass is in pounds convert it to kg by dividing by 2.2. We can define G = (h2 - h1) /d as the grade (slope) as a fraction and g = 9.8 m/sec^2. Thus Wh = k*m*9.8*G.

Now we let W = Wd + Wk + Wp where W has its meaning as in the earlier post, that is the watt hours per mile for the towing vehicle including the effects of regeneration in normal driving qs determined by you from OD readings, but modify the simpler formula to

R = Rn/(1 + (To + 9.8*k*mT*G)/(Wo + 9.8*k*mW*G) )

in which mT and mW represent, respectively, the masses of the trailer and truck so that we can include the effects of grade.

1//(1 + (To + 9.8*k*mT*G)/(Wo + 9.8*k*mW*G) ) represents the reduction in range on a grade relative to what the range is without the trailer (Rn). This is Rn = S/(Wo + 9.8*k*mW*G) in which S is the battery capacity. Thus there are two range reduction factors at play

1) Wo/(Wo + 9.8*k*mW*G) representing the reduction in range caused by the grade for the truck alone
2) 1//(1 + (To + 9.8*k*mT*G)/(Wo + 9.8*k*mW*G) ) a further reduction caused by the trailer.

Note that these can be increases in range if G < 0 (downhill grade - don't forget to change k to - 0.9 in that case.


Now all this is obviously a lot to digest so I hope it will be useful. If we plug in numbers for a 2500 kg X and look at at 1% grade we find Wh = 269 which is close to Wo = 300 Wh/mi. In the previous post we looked at trailing another X such that To = Xo and mT = mW in which case the first factor (X alone) represents a reduction to 300/(300 + 269) = 0.527 of 0 grade range. The second factor represents reduction to 0.5 of the no trailer range. The combination thus estimates range on a 1 % grade as about 26% of an X's nominal range.