Towing with an electric vehicle

[BigDan]

Originally Posted by Raspy

I don't know what the efficiency of the electric vehicle is, but it must be far higher considering there is far less waste heat.

Compared to road and aero losses the power conversion loss is essentially nil. ICE vehicles are heat engines, which take energy (fuel) and convert it to work (turning wheels). EV’s already contain a storage of work - a battery, so there’s zero conversion losses, and no loss through gearing (EV’s have typically a single fixed gear). The only loss is a little bit of heating up the motor - to 120 deg F or so, but most EV’s save that heat and reuse it for the cabin, the battery conditioning, etc. The other things is EV’s are highly aerodynamic, not having a big front grill and otherwise being designed for it (flat under carriage, etc).

Stopping every 150 miles or so does not seem like a deal breaker to me. Being on vacation, instead of being late to work, makes those stops a good chance to stretch and feel great at the destination. I don't think the average length of the stops was mentioned, but with the fast charging systems now, it seems one can add about 200 miles of range in under 20 minutes. Of course towing range would be less than that. Thoughts?

I’ve done careful analysis of the Silverado EV with 400 mi range/212 kWh battery, where it appears you can stay within the 20%-80% Goldilocks zone of the SOC and have a full days driving of 300-400 miles/sub 5 hours, with a single under one hour charge at noontime on a 350kW charger commonly available. This includes losses of a towable, but does assume you keep it under 60, aero is going to destroy you no matter what vehicle you drive faster than that.

To do these calculations you want to ideally use the range 20%-80% else otherwise you’re putting wear on the battery and wasting your time for incremental charging. Losses are assumed at 30%ish with a reasonably aero trailer and the 60 mph maximum. At lower speeds EV’s will go forever.

[Travellers]

Originally Posted by BigDan

Compared to road and aero losses the power conversion loss is essentially nil. ICE vehicles are heat engines, which take energy (fuel) and convert it to work (turning wheels). EV’s already contain a storage of work - a battery, so there’s zero conversion losses, and no loss through gearing (EV’s have typically a single fixed gear). The only loss is a little bit of heating up the motor - to 120 deg F or so, but most EV’s save that heat and reuse it for the cabin, the battery conditioning, etc. The other things is EV’s are highly aerodynamic, not having a big front grill and otherwise being designed for it (flat under carriage, etc).



I’ve done careful analysis of the Silverado EV with 400 mi range/212 kWh battery, where it appears you can stay within the 20%-80% Goldilocks zone of the SOC and have a full days driving of 300-400 miles/sub 5 hours, with a single under one hour charge at noontime on a 350kW charger commonly available. This includes losses of a towable, but does assume you keep it under 60, aero is going to destroy you no matter what vehicle you drive faster than that.

To do these calculations you want to ideally use the range 20%-80% else otherwise you’re putting wear on the battery and wasting your time for incremental charging. Losses are assumed at 30%ish with a reasonably aero trailer and the 60 mph maximum. At lower speeds EV’s will go forever.

Yah. Speed is a huge factor. We tow at max 90 kph but reality is for us the speed limit is seldom over that where we travel in BC. But it’s interesting to watch consumption climb at higher speeds.

[Raspy]

Originally Posted by Travellers

Yah. Speed is a huge factor. We tow at max 90 kph but reality is for us the speed limit is seldom over that where we travel in BC. But it’s interesting to watch consumption climb at higher speeds.

It's easy to overlook the problem of wind resistance. But wind resistance increases by the square of the speed. So, the difference between 50 and 70 MPH is only 20 MPH, about 29% faster, but at 70 the wind resistance is about twice that of 50 MPH.

If someone wants more efficiency, or better mileage, drive slower. Wind resistance is the one efficiency factor we have the most control over when driving longer distances. Each of us has to decide how much more we are willing to spend to get there a little faster. Or how many more fuel stops we are willing to make to get there a little faster. How much is speed worth?

[justa25thTA]

Originally Posted by Travellers

I’m not good with numbers but we generally stop to charge every couple hours and a typical charge stop for us when towing is closer to 30 minutes as opposed to 20 minutes when not towing, and they’d because we suck the battery down further and charge it higher than when not towing.



That’s our experience. We towed over 15200 kilometres last year.

You have to leave your camper sitting in the way of traffic while charging?

[Travellers]

Originally Posted by justa25thTA

You have to leave your camper sitting in the way of traffic while charging?

No. The picture doesn’t show well. It’s not in traffic. It’s a big wide lot. The traffic is further back. This trailer stall is typical of some tesla drive in back out trailer stalls but it is meant for short trailers only.

This is also a trailer stall but it is a parallel affair. One can back straight or swing wife and parallel park. It is separated from the other stalls by about 10 metres to accommodate this.



There’s always a way. We practice max courtesy and make sure we don’t inconvenience other drivers. Here’s a few more charge pics.

This one is in southern BC...somewhere.... Maybe Castelgar. This is a FLO station. Kinda slow at 50 KW but actually a slow charger is kinda handy at lunch as you don't have to scarf down your meal to beat the charge complete text.



This one is Drummondville Quebec. We used it twice, once on the way in and once on the way back. Worked out good but this was actually a fairly busy little supercharger. Thought for sure I was going to have to move at one point.



This one is Coburg Ontario...I think... Less chance of a problem when they are this size...as long as its not a long weekend.



The trend is towards more trailer accessible stalls as more and more of us are towing little trailers. It all takes time.

[justa25thTA]

Originally Posted by Travellers

No. The picture doesn’t show well. It’s not in traffic. It’s a big wide lot. The traffic is further back. This trailer stall is typical of some tesla drive in back out trailer stalls but it is meant for short trailers only.

This is also a trailer stall but it is a parallel affair. One can back straight or swing wife and parallel park. It is separated from the other stalls by about 10 metres to accommodate this.



There’s always a way. We practice max courtesy and make sure we don’t inconvenience other drivers. Here’s a few more charge pics.

This one is in southern BC...somewhere.... Maybe Castelgar. This is a FLO station. Kinda slow at 50 KW but actually a slow charger is kinda handy at lunch as you don't have to scarf down your meal to beat the charge complete text.



This one is Drummondville Quebec. We used it twice, once on the way in and once on the way back. Worked out good but this was actually a fairly busy little supercharger. Thought for sure I was going to have to move at one point.



This one is Coburg Ontario...I think... Less chance of a problem when they are this size...as long as its not a long weekend.



The trend is towards more trailer accessible stalls as more and more of us are towing little trailers. It all takes time.

Perhaps the pictures don't tell the story, but in picture 1 it looks like you are across at least 3 parking spots. Picture 3 looks like the front end of your vehicle is sticking out into traffic. Picture 4 looks like you are sitting across 4, maybe 5 parking spots.


As much grief as some EV drivers get, that LOOKS like you are asking for trouble. Glad to be wrong though.

[Travellers]

Originally Posted by justa25thTA

Perhaps the pictures don't tell the story, but in picture 1 it looks like you are across at least 3 parking spots. Picture 3 looks like the front end of your vehicle is sticking out into traffic. Picture 4 looks like you are sitting across 4, maybe 5 parking spots.


As much grief as some EV drivers get, that LOOKS like you are asking for trouble. Glad to be wrong though.

No. Picture one is one charge stall. It’s separated from the rest by about 10 metres. It was designed that way for trailers.

Definitely not blocking traffic in 3.

Picture 4 I’m taking up 3 stalls but it’s a quiet time at the charger location so not a big deal.
We use to block multiple pumps with our truck fifth wheel combo. It happens. We try to be courteous and if it looks like we are going to inconvenience someone we move or disconnect. It’s not a big deal.

Cheers.

[Steve Hague]

Originally Posted by Raspy

Jon,

While the energy content of gasoline is about 33.42 KWH/US gallon, gasoline engines are only about 35% efficient (fuel consumed vs power produced at the crankshaft). Maybe less while working hard. And the drivetrain causes more losses through friction. So for an equivalent amount of work done, towing a trailer for that distance in those conditions, by a gas driven vehicle, it would take about three times the 22 gallon figure. Or approximately 66 gallons of gas depending on several factors. I don't know what the efficiency of the electric vehicle is, but it must be far higher considering there is far less waste heat.

Stopping every 150 miles or so does not seem like a deal breaker to me. Being on vacation, instead of being late to work, makes those stops a good chance to stretch and feel great at the destination. I don't think the average length of the stops was mentioned, but with the fast charging systems now, it seems one can add about 200 miles of range in under 20 minutes. Of course towing range would be less than that. Thoughts?

Good question about the charging time.
On the way to Gunter Hill our average charging time was 28 minutes. Two of those five required unhitching which added about 5 minutes to each beyond the charging time.
On the way back home our average charging time was 46 minutes, with three of the six stops requiring unhitching.
On the way down we probably averaged 62 MPH. On the way home it was quite a bit faster (70+), as I was tempted to go faster by the Tesla navigation showing that we would arrive at the next planned charging stop with plenty of margin. I ended up staying with the flow of traffic, which increased our consumption and therefore our charging time. Live and learn.

[Travellers]

Originally Posted by Steve Hague

Good question about the charging time.
On the way to Gunter Hill our average charging time was 28 minutes. Two of those five required unhitching which added about 5 minutes to each beyond the charging time.
On the way back home our average charging time was 46 minutes, with three of the six stops requiring unhitching.
On the way down we probably averaged 62 MPH. On the way home it was quite a bit faster (70+), as I was tempted to go faster by the Tesla navigation showing that we would arrive at the next planned charging stop with plenty of margin. I ended up staying with the flow of traffic, which increased our consumption and therefore our charging time. Live and learn.

Heh heh. I hear ya Steve. The age old question. Go faster and use more fuel or slow down and use less. We mostly hang out in the right lane at 90 kmh but depending on the circumstances will press a bit. Generally speaking with a short wheel base combo we are more in our comfort zone at lower speeds.

We have been pretty fortunate and seldom have to unhook to charge, but if there is a chance of inconveniencing some one we unhook.

Glad you had a good trip. Have a great camping summer. Ours starts in 5 weeks in Bear creek provincial park. But we have lots of scheduled miles in front of us this year., mostly on north Vancouver island and northern routes in BC. (Highway 16 from prince Rupert to Jasper Alberta. Should be fun.

Cheers.

[Jon MB]

Originally Posted by BigDan

EV’s already contain a storage of work - a battery, so there’s zero conversion losses, and no loss through gearing (EV’s have typically a single fixed gear). The only loss is a little bit of heating up the motor - to 120 deg F or so, but most EV’s save that heat and reuse it for the cabin, the battery conditioning, etc. The other things is EV’s are highly aerodynamic, not having a big front grill and otherwise being designed for it (flat under carriage, etc).

To do these calculations you want to ideally use the range 20%-80% else otherwise you’re putting wear on the battery and wasting your time for incremental charging. Losses are assumed at 30%ish with a reasonably aero trailer and the 60 mph maximum. At lower speeds EV’s will go forever.

The losses of converting the DC battery power into the three phase AC that the drive motor(s) use is a loss. The heat produced by battery discharge, by DC to AC conversion, motor windings, planetary gear sets, and such does add up. Less of a percentage of loss from DC energy to miles traveled than the 60 to 75% lost in converting liquid combustible fuel heat energy to miles, but still a loss that isn't "zero". That waste heat, though far less than with a combustion process, has to be dissipated and can't be used for adding distance.

GM, in their wisdom, put limits on my Volt's battery usage that prevent me from deviating from the 80-20 guide, or rather the 85-25. I get annoyed that I can only use the middle 10 kWh of the car's 16 kWh battery. The on-board generator starts up at about 25% SOC to prevent dropping below that, and plug-in grid charge ends at about 85%, but I do expect a greater number of years before battery deterioration becomes an issue, and have avoided the battery fire recalls prompted by makers pushing the upper charge limit in an effort to gain range for advertising reasons.

The 30% range loss is on par with my experiences of towing assorted trailers with appropriate tow vehicles. The Audi gets 27 mpg average on weekly use, just under 18 when towing the Casi. My Saab gets 35-ish, and 25 when I took the Coleman Colorado to Sturgis last fall. The Volt with the Colorado has a comparable mi/kWh and mpg drop.

[Raspy]

Originally Posted by BigDan

EV’s already contain a storage of work - a battery, so there’s zero conversion losses, and no loss through gearing (EV’s have typically a single fixed gear). The only loss is a little bit of heating up the motor - to 120 deg F or so, but most EV’s save that heat and reuse it for the cabin, the battery conditioning, etc. The other things is EV’s are highly aerodynamic, not having a big front grill and otherwise being designed for it (flat under carriage, etc).

Zero conversion losses is not correct. Changing from dc to ac is not perfectly efficient and gears do consume energy as they transfer power.
Gears in oil have pumping losses as they shear the oil, different gear styles and sizes make more or less heat than others during the process, bearings shear oil and have pumping losses, etc. As an engineering rule of thumb, one might attribute a 5-8% loss per gear set of the remaining power. A one speed box is still a gearbox. The system is designed to match the motor to the required wheel speed, while being large enough to handle the torque, do its job quietly (helical gears) and provide a differential system to allow the wheels to turn at different speeds while delivering equal torque to the ground. Oil is constantly being circulated by the movement of the gears and is constantly being sheared between the gear teeth. Lost power is being converted to heat. You mentioned that heat was saved and used for heating the cabin. How is this done? What is the reservoir? Not on hot days. Excess heat is wasted energy. No gearbox is 100% efficient.

[Radar1]

Originally Posted by Steve Hague

Our first outing of 2023 was to Gunter Hill COE..

Glad we got to see and talk to you at Gunter Hill. It was a bit on the chilly side this year, was wondering about your trip home.
Dave and Marilyn

[thrifty bill]

Originally Posted by Raspy

Jon,

While the energy content of gasoline is about 33.42 KWH/US gallon, gasoline engines are only about 35% efficient (fuel consumed vs power produced at the crankshaft).

It's the energy used to create the electricity that makes the difference.

If the source of the electricity is natural gas turbine, turbines are about 44% efficient in converting the energy in natural gas to electricity. Coal is much worse at slightly over 30%.

Meanwhile, a natural gas furnace can be 95% efficient.

[Jon MB]

The "well-to-wheels" energy return on investment (EROI) is about equal for all fossil sourced energy, about 15%. About "100 gallons of energy" are used to get "115 gallons" to the end user
The home heat from burning methane (lets call "natural" gas what it is) may be 95% efficient at producing heat, but the majority of that heat goes up the flue. The heat applied to the space intended to be heated is a fraction of that total heat.
An internal combustion powered vehicle is close to that heat energy efficiency as well: Almost all the heat energy in the fuel is converted to heat, but only a small fraction (25 to 35%) is delivered for the intended purpose of moving a person or goods.
The heat loss of electric cars is much less, a greater percent of the energy (around 85% of that in the battery) is used for movement.
50% of 15% for methane
30% of 15% for gasoline or diesel
85% of 15% for electricity

[thrifty bill]

Originally Posted by Jon MB

The home heat from burning methane (lets call "natural" gas what it is) may be 95% efficient at producing heat, but the majority of that heat goes up the flue. The heat applied to the space intended to be heated is a fraction of that total heat.

Fraction? Majority of the heat goes up the flue?

Not the case with natural gas furnaces. Many have very little heat going up the flue, in fact you will find plastic vent piping used on high efficiency units. It's 97% because 97% of the heat from burning the natural gas goes into your home, and only 3% goes out the flue.

Even new standard gas furnaces are 80% efficient: 80% goes to heating your home, 20% goes out the flue. So none of them have the majority of the heat going up the flue.

We have a 97% efficient unit ourselves. YMMV. And cities that use natural gas to produce electricity (44%, 56% goes out the stack), then deliver that electricity to your home or vehicle are very energy inefficient.

I put a natural gas hot water boiler (for hot water heat) in a home back in 1983. Even then, the unit was 95% efficient, so it's not just a recent improvement. Basically, the high efficiency units use secondary heat exchangers to capture the heat in the exhaust.

[Raspy]

Originally Posted by thrifty bill

Fraction? Majority of the heat goes up the flue?

Not the case with natural gas furnaces. Many have very little heat going up the flue, in fact you will find plastic vent piping used on high efficiency units. It's 97% because 97% of the heat from burning the natural gas goes into your home, and only 3% goes out the flue.

Even new standard gas furnaces are 80% efficient: 80% goes to heating your home, 20% goes out the flue. So none of them have the majority of the heat going up the flue.

We have a 97% efficient unit ourselves. YMMV. And cities that use natural gas to produce electricity (44%, 56% goes out the stack), then deliver that electricity to your home or vehicle are very energy inefficient.

I put a natural gas hot water boiler (for hot water heat) in a home back in 1983. Even then, the unit was 95% efficient, so it's not just a recent improvement. Basically, the high efficiency units use secondary heat exchangers to capture the heat in the exhaust.

Earlier hydronic boilers that ran at approximately 70-80% efficient were designed to never condense water out of the flue gasses. That condensation was acidic and had liquid water. It would destroy boiler heat exchangers. When modern high efficiency boilers were developed, they were designed to condense the flue gasses by essentially being oversized to the point they pulled enough energy out of the exhaust that the exhaust condensed. They take the latent heat of vaporization and send it to the house, instead of out the stack. They are designed from high grade stainless steel that is not affected by the acidic liquid. They also have a way to manage the condensation, by dripping it out of the boiler. And they have a computer controlled combustion system that is not reliant on the old fashioned natural draft that was induced by a large flame. Instead, they have a blower and gas valve system that feeds the boiler a prescribed amount of properly mixed fuel and air mixture. The flame size can vary and only a controlled amount of air can pass through the combustion chamber. Compare this to an old fashioned home fireplace, where a large flame drives the flue gasses and a large percentage of the flame's energy is consumed to drive the system. With the modern high efficiency system, the fan powers the flue draft. By combining a carefully balanced combustion system, a fan to drive the flue gasses, and an oversized heat exchanger, it is easy to improve boiler efficiency to about 95%. By efficiency, I mean the amount of energy that gets delivered to the house, from the amount of overall energy fed into the boiler. Or, about 95%. About 5% goes out the stack as warm humid air through PVC piping. Before condensing boilers were adopted across the industry, boilers were being improved from the earlier 70-80% range, to 82-85%. These are just refined natural draft boilers that are good, but an interim step. The extra 10%, to 95% efficiency makes the boiler much more complicated, but by capturing the latent heat by condensing the flue gasses, an extra 10% can be captured over the earlier "high efficiency" of the 1980s. On my standard efficiency oil boiler at home (85%) I have fine tuned it to run as cool as possible without condensing and I started out with a larger boiler that I detuned to more effectively cool the exhaust. It also has a very large delivery system (radiant floor) that only needs about 80 degrees delivered water temp to heat the house. To make the overall system even better, I installed a thermal solar system that does all of the heating and hot water for about 8-9 months of the year, then uses oil to make up the difference in the cold overcast periods. I chose not to go with the most up to date high efficiency boiler because of the significant increase in complexity and possible reduced reliability.

[Steve Hague]

Originally Posted by Radar1

Glad we got to see and talk to you at Gunter Hill. It was a bit on the chilly side this year, was wondering about your trip home.
Dave and Marilyn

Even though it was mostly chilly at Gunter Hill, it was still nice to get a preview of the spring flowers. Here at home a week later, and we still only have a few crocuses and daffodils in bloom.
Our trip home was uneventful and fairly relaxing, but the next day I regretted driving straight through. I think that it would be better to keep the day's mileage under 500.
It was great to see you and Marilyn and looking forward attending more rallies with you in the coming months.
Steve and Beth

[BigDan]

Originally Posted by Jon MB

The losses of converting the DC battery power into the three phase AC that the drive motor(s) use is a loss.

Originally Posted by Raspy

Zero conversion losses is not correct.

Zero conversion to create a unit of work is what I was talking about. To take energy (petrol) and convert to work (explosion in a piston) loses most of the energy in the process (waste heat that must be dumped overboard via a prone to breakdown system) whereas the battery already stores work.

The drive chain after that - DC to AC conversion plus 1 speed gearbox, vs ICE piston/drive shaft/transmission/generator/etc is a different system that of course incurs losses. But since you mention it, the losses of the EV drive chain are effectively negligible, since the tiny losses (compared to ICE especially) are usually scavenged for battery and cabin climate control - depending on ambient conditions.

We can get pedantic here but engineering wise the efficiency of ICE vs EV is orders of magnitude different any way you cut it - and we’re not even including losses inherent in the fuel vs electricity chain before it got to your vehicle.

[geneR]

My fist post on this site. I am Gene from southern California.


I am glad to see great results for you folks with your EV towing here. I bought my first Tesla back in 2012. I have not bought a single gallon of gas since. I added 11 Kw of solar to my home, added 2 Powerwalls and converted all of my home to be all electric. All my transport and home life literally is free, powered by the sun.


I used to be a professional mechanic working on gas and diesel. I was an engine rebuild specialist. At this point when a friend brings by a failing gas cancermobile, looking under the hood is laughable to me. What a quagmire of poisonous idiocy. Thankfully, I rarely fix friend's cars anymore, most all of my friends and family are now driving EV'S, mostly Tesla.



These days I drive a Tesla Model Y. I had a TAB320 for awhile. Towing it was a breeze with the Model Y. Only downside was 500 watt/mile consumption at fwy speeds. I had a Rivian on order but have cancelled it as I have learned that the Rivian consumes more energy even empty, just driving around town, than my Model Y does towing a TAB!!



I learned a lot about trailer aerodynamics since then. These teardrops are really being towed backwards. That slope in the rear creates a vacuum. The curve in the front does little to help. The biggest killer is the sharp edge where the front and the flat sides meet, such as on my TAB. And so, I have a Scamp 13 foot on order, no bath, dinette version so I can leave the bed set up. Like an Airstream, the Scamp edges are all curved. This should have decent results for aerodynamics.


In my case, I have ordered my SCAMP deleting all gas appliances. My wonderfully pollution free home air quality I plan to carry on to my SCAMP. I was interested to hear from the Scamp salesman that I am not alone and they are actually looking into making an all electric version option as they get many requests. (Just look up gas stove health hazards for a frightening awakening). I have already been tent camping successfully with an Ecoflow Delta2 battery, 12v fridge and single burner induction stove. It works out superbly. I'll just work all this gear into the Scamp after I receive the new trailer.


Anyway, nice to see you all here!

[Travellers]

Welcome to the group. Thanks for sharing your experiences.