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Discussion Starter · #1 ·
Many will laugh this off, but, I'm beginning to think it may be a valid question....

Now that we have pickups coming to market that are capable of towing, got me thinking, could you just take two Rivian's, tow one to charge it with regenerative braking and switch back and forth?

I've had EV's for 9+ years. Always noticed how much range I got back on a long steep downward sloping hillside from regenerative braking. While I don't have scientific stats, the range gained over a 4 mile down hill run was significant. Certainly more than the 4 miles travelled.

Tried searching the internet and found where someone towed a Model 3 around a 1.4 mile track and gained more than 1.4 miles in range. Was closer to 3.5 miles gained. Hence, regenerative braking seems to charge much faster than the distance travelled.

The question would be, how much range loss would you experience from towing? If you can gain 3.5 miles in range by towing over a 1.4 mile distance, or more simply put, gain 2.5 miles by towing 1 mile, so long as your range doesn't decline by that much from towing, seems like you could just switch off and never have to charge?

Rivian has 314 miles in range. Towing we know drastically lowers that range.
Based on the Tesla towing test, Towing 100 miles would theoretically add 250 miles in range to the other Rivian. Could be more or less depending on the actual regenerative power, which in my test drive of the Rivian felt stronger than a Tesla. But, it was only a 1 mile drive, so no clue how much actual range I was gaining. But theoretically, If I can gain 250 miles of range in 100 miles, that means that, you'd only have to accomplish a range of 100 miles from the 300 mile range battery to be net zero. Seems possible, no??

Get a tow-bar to attach the two vehicles together. Would have to have a driver in each vehicle with both vehicles on and shifted in to "Drive". If the Rivian's regen is equal to the Tesla and really will add 2.5 miles in range for every 1 mile driven, then simply towing a second Rivian would theoretically give you endless range? Assuming you can get 100 miles in range out of the battery while towing the other Rivian.

May not be the greatest on the motors and charging system, but the question being, "could it be done?". Not "should" it be done. In a pinch, could be useful. Keep the speeds reasonable. The Tesla test was at about 30 miles per hour, so not that fast.

Anyway, just a thought for fun, but that thought , when thinking further, seems like it could actually be a reality. Until now, there were no EV's practically capable of towing. Now, with the Ford, Hummer & Rivian, there is. Will be interesting to see if someone tests this out. Seems like it could work. Your batteries and drivetrain may not last as long as a result, but that's not the point to the question. If you ended up in the middle of a desert somewhere, 1,000 miles from the nearest charger, and had one charged up Rivian and one on empty, could you get to the that charger 1,000 miles away by connecting the two vehicles together?

I do see that Ford filed a patent for recharging by towing. So, clearly they've thought of it. The only question is, how far could you tow versus how much range is gained on the second vehicle from the regenerative power? Seems like 100 miles is certainly possible, especially at just 30 MPH. In this scenario, with a solid enough tow bar, rather than switching back and forth, the Rivian behind could just push the Rivian in front once it runs out, which would be the same as towing and recharge the front Rivian while it's being pushed, instead of towed. I remember, even in my Chevy Volt years ago, coasting down the grapevine gave me several miles of range back, far more in that short distance than I ever got from plugging in the car over the same amount of time.

I don't know. Thinking it might be possible. Maybe not practical, but certainly possible?
 

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Discussion Starter · #6 ·
Why not just put a 30kw generator in the bed and use it as a REx..... get a couple of 6gal marine gas tanks and you're all set o_O
Considering charge rates at 16 miles per hour, couldn't charge fast enough. And that's if you can get 240 from a generator. Otherwise, you'd only be adding 3-4 miles per hour of range. Not a bad idea for a destination option if there are no chargers. Regen charges pretty darn quick. Obviously, we don't have many mountains long enough to charge an entire battery. But, pulling it, would effectively be like going down a 100 mile long mountain. Regen, at least on other EV's charges pretty quickly, relative to miles gained per hour.

What you postulate is not possible. You will expend more energy than you regen.
Is there data that supports that the regen in place on EV's will not regenerate enough power? I tried to find some results on this. Other than the test I found where they towed a Tesla. That's the key question. Based on the Tesla test results, gaining 2.5 miles of charge (actually happened) after just 1 mile of driving (being towed), the only question is then, could you tow at 30 miles per hour using less than 1 kwh/per mile? EPA estimates reflect that at 314 miles, you can get 2.3 miles per Kwh used. Maybe 2.5 depending on how much of the 135kwh battery is available for use. If the Rivian regens at the same rate as the Tesla proved to do in the test, seems completely possible that the Rivian, even towing, could get 1 mile per 1 kwh used, thus easily get 100 miles out of a 135 kwh battery.
 

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Is there data that supports that the regen in place on EV's will not regenerate enough power?
you can tow-charge an EV and build range in the towed vehicle via regen, but the amount of energy you recover will be less than the energy consumed by the towing vehicle. Your original premise that two vehicles could tow each other and “leapfrog” for unlimited range simply violates the laws of physics as we currently understand them. What this boils down to is “perpetual motion” and many have tried and none have succeeded.

I tried to find some results on this. Other than the test I found where they towed a Tesla. That's the key question. Based on the Tesla test results, gaining 2.5 miles of charge (actually happened) after just 1 mile of driving (being towed), the only question is then, could you tow at 30 miles per hour using less than 1 kwh/per mile? EPA estimates reflect that at 314 miles, you can get 2.3 miles per Kwh used. Maybe 2.5 depending on how much of the 135kwh battery is available for use. If the Rivian regens at the same rate as the Tesla proved to do in the test, seems completely possible that the Rivian, even towing, could get 1 mile per 1 kwh used, thus easily get 100 miles out of a 135 kwh battery.
Are you asking about a theoretical “real world” application? If so, you’d need to support gains at a net-zero elevation gain (either flat road or if there is a decline at some point there would need to be an incline at another to compensate — such as a return journey). Under this scenario, you’ll expend more energy towing the vehicle than you’d gain back through regen.

if you’re asking about a contrived scenario such as only going down a steep mountain, then I suppose you could regen more than the energy expended towing — since gravity is doing the heavy lifting…. But that isn’t practical and wouldn’t be actual efficiency gains. It’s no different than a 15mpg truck can technically show 99mpg when coasting down a mountain.
 

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Discussion Starter · #9 ·
you can tow-charge an EV and build range in the towed vehicle via regen, but the amount of energy you recover will be less than the energy consumed by the towing vehicle. Your original premise that two vehicles could tow each other and “leapfrog” for unlimited range simply violates the laws of physics as we currently understand them. What this boils down to is “perpetual motion” and many have tried and none have succeeded.


Are you asking about a theoretical “real world” application? If so, you’d need to support gains at a net-zero elevation gain (either flat road or if there is a decline at some point there would need to be an incline at another to compensate — such as a return journey). Under this scenario, you’ll expend more energy towing the vehicle than you’d gain back through regen.

if you’re asking about a contrived scenario such as only going down a steep mountain, then I suppose you could regen more than the energy expended towing — since gravity is doing the heavy lifting…. But that isn’t practical and wouldn’t be actual efficiency gains. It’s no different than a 15mpg truck can technically show 99mpg when coasting down a mountain.
As I noted, just going based on the numbers from tests that ARE available. Not just assuming because it's never been done before. The test of the Tesla proves what's possible in that scenario. The only question is, how much range will the Rivian lose by actually towing another one. Until we know that, neither one of us has any factual information to say it is possible or not possible. I'm certain someone will try it at some point. Again, just based on what is out there, it's not as impossible as the thought of it would initially seem. People will say no, can't be done, just because it hasn't been done or doesn't make sense. But, if the Rivian can get 100 miles in range while towing another Rivian, then, it's certainly possible that it at least comes close to be possible. Time will tell.
 

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As I noted, just going based on the numbers from tests that ARE available. Not just assuming because it's never been done before. The test of the Tesla proves what's possible in that scenario. The only question is, how much range will the Rivian lose by actually towing another one. Until we know that, neither one of us has any factual information to say it is possible or not possible. I'm certain someone will try it at some point. Again, just based on what is out there, it's not as impossible as the thought of it would initially seem. People will say no, can't be done, just because it hasn't been done or doesn't make sense. But, if the Rivian can get 100 miles in range while towing another Rivian, then, it's certainly possible that it at least comes close to be possible. Time will tell.
Science does not agree with you. Science backs me up. I can't tell you specifically how bad the energy consumption is, but I can say with 100% certainty that you cannot add more energy than what you consume, if you're on a flat road, or include a "return" journey on any route that involves a decrease in elevation.
 

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Discussion Starter · #11 ·
Unfortunately, neither of us knows for sure. I will point out, at one point, nobody thought it would be possible to generate power just from the sun. Then came solar.

Another example that could be relevant....If you're a NASCAR fan, think back about 8 or 10 years ago when they were doing tandem racing at Daytona & Talladega. One car by itself was only capable of a speed of up to 200 or so MPH. However, when two cars became attached, not only did they go much faster together, they also consumed notably less fuel between them. The car behind could stay attached to the car in front with just the throttle pressed only halfway down. The math isn't linear. Two together are capable of more than the results of each individually, then added together.

It's only not possible until someone does it.

If I had my truck, I'd try it. Unfortunately, I won't be able to do so for at least 7 months.

If it's not possible, I wonder why Ford decided to patent it?
 

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Unfortunately, neither of us knows for sure. I will point out, at one point, nobody thought it would be possible to generate power just from the sun. Then came solar.
Mankind has known solar power was possible for a looooong time. It may not have had a practical implementation until relatively recently -- but it was known to be theoretically possible.

Nuclear fusion is another example of something we know is theoretically possible (it happens on the sun, for example) but we have not found a way to safely harness it in a cost-effective manner.

These are NOT the same thing as perpetual motion. It isn't simply a matter of "we haven't figured out how to do it well/cheaply yet" but rather that it would violate the laws of physics.

Another example that could be relevant....If you're a NASCAR fan, think back about 8 or 10 years ago when they were doing tandem racing at Daytona & Talladega. One car by itself was only capable of a speed of up to 200 or so MPH. However, when two cars became attached, not only did they go much faster together, they also consumed notably less fuel between them. The car behind could stay attached to the car in front with just the throttle pressed only halfway down. The math isn't linear. Two together are capable of more than the results of each individually, then added together.
That can all be explained with fluid dynamics. The theory was well known. Practical, demonstrable applications may be discovered for theoretical concepts -- but the theories evolve, first. You're really trying to reach and use false analogies that simply do not apply in this situation. Perpetual motion isn't even theoretically possible. It's impossible.

If it's not possible, I wonder why Ford decided to patent it?
Oh, please show us this magical patent on perpetual motion! I can't wait to read it ROFLMFAO.
 

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Unfortunately, neither of us knows for sure.
Yes, we do know, 100% for sure - your scheme will not work. This is not subject to change, and is not subject to new knowledge or new theories coming along. Conservation of energy is continually being tested to great precision and continually found to be true to more decimal places than you have fingers. I'm not going to even try to convince you further, because there are quite literally hundreds of years of science testing this and confirming it - at this point it's simple high school physics. If you want to understand why this is true, then there are libraries full of materials you can read to educate yourself. But if your mind is closed there's nothing I can say that will matter to you.

If you accept this as a fact, you will quickly see the major weakness in your original argument. It is the same reason why putting a wind turbine on an electric airplane won't give us unlimited range for free.
 

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Don't forget, Toyota already has self-charging vehicles! (I didn't watch the last LeMans race but I am assuming they never stopped for gas.)
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Discussion Starter · #15 ·
Yes, we do know, 100% for sure - your scheme will not work. This is not subject to change, and is not subject to new knowledge or new theories coming along. Conservation of energy is continually being tested to great precision and continually found to be true to more decimal places than you have fingers. I'm not going to even try to convince you further, because there are quite literally hundreds of years of science testing this and confirming it - at this point it's simple high school physics. If you want to understand why this is true, then there are libraries full of materials you can read to educate yourself. But if your mind is closed there's nothing I can say that will matter to you.

If you accept this as a fact, you will quickly see the major weakness in your original argument. It is the same reason why putting a wind turbine on an electric airplane won't give us unlimited range for free.
No need to get snooty. My "argument"?. More like "question". Again, simply based on the results of a factual test where a Tesla generated enough power by being towed, that, "IF" the Rivian could tow another Rivian for 100 miles on a single charge, might make it possible. Regardless of what science might say. My question again, has it been tried? I sounds as though there's at least one closed-minded person in this discussion and it's not me. Regardless of what science may or may not say, real world results are all that matters. I guess the same could be tested with a Tesla towing a Tesla, but, clearly not that easy to hook up two Tesla's as it would be two Rivian's or Ford Lightning's. Not an argument, just a question of if it may work in the real world. The test of the Tesla appears to indicate it's possible. Again "possible", not definite. But, I am open-minded to the numbers from the Tesla test that suggest, IF the Rivian can do 100 miles and produces a similar level of regen that a Tesla does, then no matter what science says, the Rivian being towed will have generated more miles in range added that the Rivian that towed it lost. Possibly, the drag from towing a Rivian will be too great to allow the towing Rivian to go 100 miles on a full charge? (actually would need to be 125 based on simple math). But, if a Rivian can tow 9,000 lbs and only lose half its range, then, maybe it can tow a 7,000 lb Rivian, effectively with brakes partially applied and not lose more than 2/3rds of its range. Maybe it can't. Until it's attempted in the real world, not in science, at least based on what real world knowledge exists regarding the range of a Rivian Towing and the real world knowledge of how much power can be recuperated from towing an EV, it doesn't seem as impossible as the science would suggest.

Keeping an open mind. And, the wind turbine example is more relevant to a comparison with Solar power. Both generate power to slowly to offset. A Tesla being towed, generates 2 1/2 miles of range added after just one mile. Which is far faster than that most charging systems, other than Tesla Supercharging or DC fast charging. Assuming the Rivian to be as good as the Tesla (if not better since it has four separate motors versus Tesla only having two to regenerate power), then after 100 miles, if it stays linear, should have 250 miles in range after 100 miles of being towed. Possibly, more realistic to only do 50 mile stretches or just 25 mile stretches to not overtax the battery. Would just mean switching between vehicles more often rather than attempting to do it all in one stretch based on full battery capacity. And technically, you could generate enough power with solar to never have to charge if you had the surface area available to absorb enough energy during the day. Not practical, but certainly possible. I don't know enough about wind turbines, but assuming the same would be true, if you had space for enough turbines, then it could be possible. Again, not practical.

Anyway, sorry to have offended any of the scientists out there with the question. Only asked based on the "real world" test results of towing a Tesla and simple elementary school math adds up, IF the Rivian can tow and go 125 miles or so doing so on a single charge. That remains the primary question that needs an answer. The only answers provided so far, are "because science says it can't be done". As with everything, science changes with more research and advancement. Remember when rockets weren't reusable? Until we can get two Rivian's together to actually try it, the question remains unanswered as it hasn't been tried yet, that we're aware of. Ford's patent suggests, they apparently have and found enough reason to patent it. If the Rivian can only two another Rivian for 50 miles before running out of range, then you will have be proven correct. If it can tow 125 miles on a charge, then there's chance the answer to my question will be "Yes".
 

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Discussion Starter · #16 ·
And even if it's not 100% net zero, certainly, any added range to the second Rivian would be free power to that particular Vehicle. That's based on technology that exists today. Can Tesla, Rivian, Ford, GM or anyone improve on that technology? Pretty likely they can and will. So, even if they can't go forever.....yet, they certainly can go further together than they can individually. (sounds like a marriage! LOL). Depending on how close a real world test indicates it is, then the possibility may not be that far off with improvement to the tech that exists today. It's been over 10 years since I had my Volt and tech then was enough to regen more energy than miles travelled. Assuming it can only get better. If it could work, then I guess you could theoretically add another battery, four more motors and four more tires to spin the motors, without the rest of the car/truck, to the same vehicle. Not necessarily practical or appealing. But, saving the weight of having a whole other truck to tow around yet achieve the same regenerative results by adding a few thousand pounds to one vehicle, rather than towing a full 7,000 lb vehicle, would be even more efficient. I think "technically", even if it's not possible by towing a full Rivian Truck, could still certainly be possible be doubling the batteries, motors and wheels to a single vehicle. That however, is a test that's highly unlikely to happen. But, towing a Rivian to see how close it gets, is certainly doable now, or as soon as two Rivian owners are willing to attempt it? Wouldn't need to go 300 miles to find out. Just a few miles would provide the results necessary to determine if it could be done, or if its even close.

Taking it further, the Rivian as a Truck is certainly not the most efficient EV in the world. If you you had someone crazy enough to put the money in to adding another battery, 4 motors and wheels, then could do it in a much more efficient vehicle. We lose what, 15% just by putting All Terrain Tires on it. So, what if you put small wheels and tires on it? Would likely be more efficient than what the EPA currently says it is. At 30 MPH, aero wouldn't be all that critical. I don't know, but, with several more "if's" added in, I think it could technically be possible with today's tech, in the right package, if it's not possible simply by having a Rivian tow another Rivian. In the right package, I'd venture to say it's far more probable than just possible, which would debunk the "science" aspect that it can't be done. Again, not practical in any other scenario than simply towing another vehicle, which already isn't very practical, but the arguments above have been that it's scientifically not possible. That, I "believe", simply from common sense, based on what factual data does exist to the common man, is incorrect. I guess the Tesla Roadster would be a step in that direction. It will already have double the battery in a light package. So, just add 4 more motors and tires under it and divide the battery to be two separate 100 kwh batteries instead of one single 200 kwh battery. Elon's claiming it will do 600 miles and 1.9 0-60. Who would have ever that that alone could be possible? All theoretical, but I think certainly probable, technically. Just towing a Rivian to accomplish the same, maybe just possible.

So, since we're on science, how do you feel about alien life in the universe? Possible, probable?, Impossible? LOL....Yeah ok, another discussion for another day! LOL

And just to be clear, simply having fun with this thread in friendly debate on possibilities and improbabilities. I personally enjoy such debates! So, all in good fun!
 

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And even if it's not 100% net zero, certainly, any added range to the second Rivian would be free power to that particular Vehicle. That's based on technology that exists today.
By your "logic" you could create a loop between a lamp and a solar panel and the light would run forever.

That is an experiment you can setup yourself, if you are so inclined. Hint: it does not work.

May as well just hire a flat bed tow truck, put your vehicle on the back of it, and have the tow driver chauffeur you everywhere. They'd spend a lot on fuel but I guess you'd feel comfortable saying that you get infinite MPG?
 

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The “example” of a Tesla gaining more miles than being towed is irrelevant. The towing vehicle exerted MUCH more energy than the towed Tesla gained. Through gearing you could design a vehicle to generate charge enough to go 10 miles after being towed just 100 feet. But the energy used to tow the Tesla would still be much more than you ever got back.

For those that think they can invent perpetual motion machines, entropy sucks.
 

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So, since we're on science, how do you feel about alien life in the universe? Possible, probable?, Impossible? LOL....Yeah ok, another discussion for another day! LOL
You probably should have posted that vs. the original topic because your original "question" has been answered by a couple of hundred years of proven math and physics. Perpetual motion in lossy systems is not possible as you are constantly losing energy due to mechanical friction and built in inefficiencies involving converting one form of energy to another and back again.

Think of pouring water out of a cup, into another cup.. then pour that water into another new cup (not the original cup) then pour that into another new cup... do that 10,000 times and you will have no water left to pour. Losses due to less than 100% efficiency transferring water from one cup to the next.

Alien life? You need to prove to me why someone would think life in the universe only exists on Earth. It would be impossible to have a sterile universe sans one planet.
 

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Wow this place got freaking weird.

So there's an argument being made to run the batteries of not 1, but 2 Rivians down to zero?
The simple logic of dragging another Rivian with Regen (let alone trying "push" one with Regen) just means you will now have TWO dead Rivians.
So you got about 50% further than you would have with just one Rivian?
Good luck with that.
Now you can have TWO times the fun re-charging BOTH vehicles fully.
Sheeeeeesh.
 
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