Tow to charge?

[jjerabek]

Is there a reason you’d hesitate to use a 10,000W generator and a 40A mobile cord to keep the truck charged as needed? Direct electrical generation is most likely to be a more efficient method.

You are right. The only reason is that for my application/business case, I will need 2 trucks anyway, in a remote place where having a 100kw battery with Pro Power on board is a boon, but no chargers.

While you are correct in terms of losses through powertrain, IF (big IF) I can pull the Lightning for 100km and recharge 40-50kW and have a 10l extra fuel consumption, I am looking at a $20 fuel surcharge. 40kw at a supercharger can be anywhere from $20-25 so really not that huge, plus you save 1 hour of fiddling around chargers if you can even get one in remote locations.

Excellent points. I am tempted to rent an HD truck to try.

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[RickLightning]

Rivian did it to get through parts when they did their americas trip.

It's 100% doable but it would be tricky and possibly illegal.

Possibly? Having someone in the towed vehicle is clearly illegal.

 

[jjerabek]

Possibly? Having someone in the towed vehicle is clearly illegal.

I guess I did not take into consideration local law. I am in BC Canada, just trying to fish out whether it is illegal.

 

[Yellow Buddy]

Hey everyone!

I am planning a business that may require me to have 2 vehicles and one of them will be my 23 SR XLT. It will likely be remote places, so I wonder:

Has anyone tried to tow your Lightning to charge it?

I saw some videos and thought: if I have a HD diesel truck, it may even be cheaper and quicker to tow charge the Lightning for parts of the journey. Thoughts? Experiences?

Edit:

Turns out that some places, including BC Canada, it is illegal to tow a vehicle that has persons inside. However, if a friend of a friend ever decides to go ahead with this heinous crime in some remote places, I'll ask them for the numbers and experience, for science.

I have done it, but with the Lightning as a tow vehicle and in an emergency situation (broken charge controller, car would not take a charge from AC nor DC but was able to use the motors to regen)

A couple of things to note, this is NOT for the faint of heart.

There is usually a distance limit to the tow strap (rather use tow bars) otherwise cars can cut in between. This puts the other driver on edge as reaction time is limited. That said, the regen is significantly faster than anticipated, just a couple of miles gets a decent amount of range back.

In an emergency situation, doable. I would not do it long distances.

 

[TaxmanHog]

 

[invertedspear]

Possibly? Having someone in the towed vehicle is clearly illegal.

That must be very location dependent. I see people around here do so all the time, often in front of cops. It's the only safe way when using a strap, rope, or chain. I've even seem them tow with a rope on the freeway, which is nuts to me. The only time I've ever used a tow chain I wanted to go as slow as possible, but that's because the in-tow vehicle had no engine, so no power steering or brakes.

 

[jjerabek]

I have done it, but with the Lightning as a tow vehicle and in an emergency situation (broken charge controller, car would not take a charge from AC nor DC but was able to use the motors to regen)

A couple of things to note, this is NOT for the faint of heart.

There is usually a distance limit to the tow strap (rather use tow bars) otherwise cars can cut in between. This puts the other driver on edge as reaction time is limited. That said, the regen is significantly faster than anticipated, just a couple of miles gets a decent amount of range back.

In an emergency situation, doable. I would not do it long distances.

Thanks for sharing! Yes, the idea would likely be a tow bar, also very likely in remote/out of town situations and as little as possible. But the idea of not being reliant on charging infrastructure and that you could drive your Lightning for 700km by towing it for 100 is enticing.

 

[tls]

Rivian did it to get through parts when they did their americas trip.

It's 100% doable but it would be tricky and possibly illegal.

Sure, with a factory engineering team available, I bet it's a thing the could be done.

It would be crazy to get near this otherwise. Think of all the ways you could destroy two $80,000+ trucks, and potentially hurt others around you on the road. A few examples:

• How are you going to tow? With all 4 wheels on the ground? What will you connect to at the front of the truck that is strong enough to tow against the resistance of the motors?
• If your answer to the above is "in reverse" consider that the truck has a maximum speed in reverse and that you have literally no idea what its motor control firmware will do if you forcibly exceed it.
• If your answer to the above is "with only two wheels on the ground", remember that you are in the realm of undefined/unknown behavior for both the motor control firmware and the traction control system. Even more can go wrong.
• If anything you do causes the towed vehicle to suddenly apply brakes or otherwise dramatically increase resistance while travelling at high speed, there is probably nothing on either end of the truck you can connect to that is strong enough to prevent a sudden, catastrophic loss of the tow connection. This is not a theoretical problem, it actually happens on railroad locomotives when their multiple-unit control systems go haywire - they can break couplers or even permanent drawbars. On a road, you don't have railroad tracks to constrain the dynamics of what can happen next.

With an engineer with full system documentation, access to all the module settings and source code, and time to prepare a list of what would need adjustment to make charging by towing possible - OK, sure, I buy that it could be done safely. Without extensive factory support? No way. The worst thing that could happen is that you could think you have it working, get up to speed, and then... Just please don't try.

 

[Yellow Buddy]

Thanks for sharing! Yes, the idea would likely be a tow bar, also very likely in remote/out of town situations and as little as possible. But the idea of not being reliant on charging infrastructure and that you could drive your Lightning for 700km by towing it for 100 is enticing.

The biggest thing is when would you know when it’s full. Without a load it regens pretty quickly.

I don’t recall the Lightnings regen rate, but Hyundais and Kia’s for example are capable of 80kW regen. We’re talking DCFC charging speeds. It would be a pain to have to stop every 30min to unhook and rehook the truck…

I’d much rather just stop at an EA and pay the $30

 

[jjerabek]

Sure, with a factory engineering team available, I bet it's a thing the could be done.

It would be crazy to get near this otherwise. Think of all the ways you could destroy two $80,000+ trucks, and potentially hurt others around you on the road. A few examples:

• How are you going to tow? With all 4 wheels on the ground? What will you connect to at the front of the truck that is strong enough to tow against the resistance of the motors?
• If your answer to the above is "in reverse" consider that the truck has a maximum speed in reverse and that you have literally no idea what its motor control firmware will do if you forcibly exceed it.
• If your answer to the above is "with only two wheels on the ground", remember that you are in the realm of undefined/unknown behavior for both the motor control firmware and the traction control system. Even more can go wrong.

Just to re-iterate, my initial use case was tow bar, driver inside the towed lightning, in remote locations without charging infrastructure.

The safety concerns you brought up IF this was attempted without a driver are very valid. I also edited the initial thread to include the fact that to tow a vehicle with someone inside is illegal in many places in North America. And that if a friend of a friend ever tries it in the future for science purposes, the results may be shared.

 

[Yellow Buddy]

Just to re-iterate, my initial use case was tow bar, driver inside the towed lightning, in remote locations without charging infrastructure.

The safety concerns you brought up IF this was attempted without a driver are very valid. I also edited the initial thread to include the fact that to tow a vehicle with someone inside is illegal in many places in North America. And that if a friend of a friend ever tries it in the future for science purposes, the results may be shared.

Would your 2nd truck be along for the journey already? Or would you tow it?

If it’s along for the journey already - it’s possible. Not recommended, but possible.

If you’re going to tow the diesel truck until you need it, it’ll make matters worse. You’ll cut your range in half just to execute a maneuver that’s not recommended.

Otherwise, I am confirming for you, what you are asking is 100% possible. It will work. The truck will regen and do so quickly. It is simple, you make sure you start towing before the truck is dead. You throw a driver in the second truck so it doesn’t throw itself in park, you put it in drive, you engage throttle to get it off of hold and you just drag it and regen. The spotter then radios you to say when you’re going too fast - too much/max regen - and when the truck is nearing 80% charge. All possible…but I would recommend leaving the Lightning home and taking the diesel for the trip instead.

 

[Jseis]

From personal experience: My ‘62 bug had dead battery. My father looks at it, then me, and says “Generator huh?” “So we tow it enough to get that battery to light up that coil”. Took a mile.

 

[marc_hanna]

So, if you drive 100km @ 100km/h you would likely use 30kWh of energy. Theoretically, towing would require 30kWh extra energy to tow the lightning 100km @ 100km/h.
A litre of diesel has 10kWh of stored energy and at 30% thermal efficiency leaves you with 3kWh of kinetic energy.
That puts you at 10 litres of diesel to theoretically charge by towing. Factor in 10% losses and you’re still only at 11 litres.
Where additional loss would occur is real-time power output and torque with the tow vehicle. If it takes 150hp to accelerate the lightning up to 100km/hr, that power would also be added onto the tow vehicle thereby running out each gear longer and to a higher rpm. So, i would estimate about triple the fuel consumption during conservative acceleration. While cruising, you will have a constant added drag of about 30kW, which is about 40hp. It doesn’t seem like a lot, but it might be enough to kick the tranny out of the overdrive gears. So, no longer running at optimal rpm for fuel economy.

So my guess is:
11 litres base load
3 litre acceleration penalty
2 litre non-optimal rpm penalty
=16 litres/100km increase in fuel consumption

Let us know your actual numbers when you give it a try.

 

[rockhead]

So, you're saying it IS DOABLE?

As long as you remember to put up a wind turbine in the Lightning to ensure over unity energy production

 

[Hank42]

From personal experience: My ‘62 bug had dead battery. My father looks at it, then me, and says “Generator huh?” “So we tow it enough to get that battery to light up that coil”. Took a mile.

A mile huh? Laggards! I used to push start my dead VW all the time - put it in neutral, give it a good running start (slight downhill never hurt ) jump in the moving car and pop the clutch with the ignition on! Would start right up every time - except that one time when the alternator was shot

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