Towing and Solar System Charging

[joelmcewen777]

Hello gang,
I am new here and bear with me if this has already been answered, though I couldn’t find an exact answer in prior posts. I am considering buying a T1 to tow a 9000 pound trailer. I understand that the specs say I can tow 11,000 but I’m trying to find real world numbers on this and how it affects range. I saw one video where they were towing around 7000 or so and it seems that you lose about 2/3 of your range if anyone has an experience towing these heavier loads like around 9000 or 10,000 short distances please let me know the range you’ve experienced. On this trailer, what I’m hoping to do is to put a 3-4kw solar system on top of the trailer, ideally giving me a little power for the trailer and also extra power to slowly charge the truck. I want to take the trailer in truck in the summer up to the California mountains and park it for one to two weeks at a time, I figured I would be able to get around 12 to 16 miles of charge per day with this smaller system and I wouldn’t only be driving the truck once or twice a week very short distances while we’re camping. Again. I am not going to be charging this a lot each day. It would be very small amounts which should be fine for the small range I need to go to the store and things like that.
Info on either of the above is much appreciated and thank you for starting this forum!

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[CharonPDX]

The same as gasoline or diesel - on flat ground, aerodynamics is the biggest detriment to efficiency. On my old diesel pickup, I lost about half my MPG when towing my large not-very-aerodynamic 8000 lb trailer at 55-60 MPH. When towing with my R1T at the same speed, I lose about half my range.

When towing at 45 MPH? I only lose about 1/3.

When towing my teardrop, ~4000 lb trailer, at 45 MPH, I barely lose any range. At 70 MPH, I lose slightly more than half. (I shudder to think how much I would have lost with the big less aerodynamic trailer.)

Oh hills, weight matters more. A 9000 lb trailer (which basically by definition would be unaerodynamic) doing 75 up the Rockies? You'll be lucky to get 70 miles out of the Dual Max. (TFL Truck got 70 miles in 80% of Gen 1 Quad Large going 60 MPH towing a mid-aerodynamic 8000 lb trailer in their "Ike Gauntlet" towing test.)

As for solar panels? Good luck fitting 3-4kW on a trailer. I guess if it's a 9000 lb trailer, it would be big enough to hold that many (8 feet by 20 feet of solar panels is 3kW at current standard solar panel efficiency.) But unless you're parking in full sun, with panels angled upward toward the sun (not flat on the roof†,) you're not going to get 3-4kW all day. You'd be *VERY* lucky to get even 15kWh in a day. And of course, your solar panels aren't going to directly feed the truck. You'd need to have an intermediate battery (EcoFlow, Bluetti, Jackery style) to collect with, then use its inverter to run an AC charge cord to the truck, introducing even more losses. If your goal is simply "cover during-the-week short drives" it might be fine.

† - My teardrop trailer has three "100W' solar panels. On its rear angled panel, so it's similar "angled upward" to house rooftop solar. Parking in full sun with the rear of my trailer pointed due south, the best instant production I've ever seen is just under 200W. Figure if it's on the flat roof of a big trailer, "4 kW" of solar panels will top out at only 2-2.5 kW peak. Yeah, you'll do decent at noon, but far worse on the edges of daylight.

 

[Electrified Outdoors]

The R1 carries the equivalent energy of about 4 and a half gallons of gas. I have documented my towing experiences and have found that weight matter a lot less than aero.

Travel trailers...especially boxy ones with a lot of ground clearance are the worst. The weight will only come into play when you have a significant net change in elevation or if you have a lot of up and down mountains. Even if no net change going up and down mountains still makes it worse with more weight because you can't recover 100% with regen when you come back down.

If you plan to tow long distances an EV may not be a good choice currently. It will be more expensive to public charge it than a comparable gas/diesel truck on long towing trips. If your like me and only tow a dozen times a year or so then it works. I figure its a little inconvenience on the road trips but I save money and time all the rest of the time.

I average between 1 and 1.2 mi per kwh with our 5,500 lb box on wheels Apex 245BHS...an airstream would probably do better. Also remember the 70% rule as that will be your practical range between charging stops. If you get max pack you have 142 kWh usable multiplied by .7 = 99.4 kWh. So likely range between charging stops on a long trip would be between 100 and 120 miles. If you run it from 100% all the way to zero (definitely not recommended!) you would get between 140 and 170 miles range.

I have seen as much as 1.6 mi per kWh with flat trailers. Everything I have towed is tandem axle. You can do better with single axle (less rolling resistance) but then one flat can turn into a whole lot of trouble.

I have some videos on my YT showing my experiences. Main reason I got my Silverado EV is to have that extra range when I need it. If I had to tow long distance very frequently I would probably get a small displacement diesel and run biodiesel blend.

 

[Fraslin]

I average between 1 and 1.2 mi per kwh with our 5,500 lb box on wheels Apex 245BHS...an airstream would probably do better

Just to jump in on this which is exactly right. We have an R1S and tow a 7,000 lb airstream and get about 1.3 kwh. That is about 180 miles of range which means we have to charge every 2.5 hours or so when towing. We live in SoCal so it is fine as we can get most places we will go for long weekends without charging or with one charge. We have taken some longer trips and it can make for some long days when you are still working and have limited vacation days. It is not too bad if you can relax and go slow (if you are retired or have flexibility)

I like the ideas on the solar for the Rivian but don't think that is practical right now. Especially as you will also need Solar for the trailer too.

 

[defcon888]

The R1 carries the equivalent energy of about 4 and a half gallons of gas.

Where is the gas tank door located?.......LOLOLOL


I'll show myself out!

 

[HyperionMark]

Sounds like the OP understands the limitations of the solar and is just using it for a few miles here and there. As someone that trickle charges his Rivian off of a tiny bit of solar (partially from RV connected to an EcoFlow), I know firsthand that you can get a little usable range from solar.

OP, sounds like an amazing trip. A 3-4kw system will be plenty for your needs as long as you keep backup options in mind. Enjoy!

 

[babock]

To get 3 to 4Kw on a trailer, your trailer would have to be a LOT bigger than anything you would want to tow.

I have 800W on a 25' trailer that I tow with an ICE truck and not much I could do to get more solar on it.

 

[HyperionMark]

To get 3 to 4Kw on a trailer, your trailer would have to be a LOT bigger than anything you would want to tow.

I have 800W on a 25' trailer that I tow with an ICE truck and not much I could do to get more solar on it.

I assume he means he would be setting up more at camp.

As far as your trailer...are they older panels? I feel like I've heard way more on smaller. Heck, I have 620W on my little Tab400.

 

[babock]

As far as your trailer...are they older panels? I feel like I've heard way more on smaller. Heck, I have 620W on my little Tab400.

2 years old. I could probably put some 250W panels in place of my 200W panels to get me 1000W. I could also fit one where my TV antenna is. Between that and my 560AH of battery, I am fine with what I have.

Looks like you have flex panels on your trailer. How long have you had them? In my experience, they only last a couple years and only ever recommend them to people that have a curved roof like yours. What's the max output you have seen for your 620W?

 

[LivingInKaos]

Ideally, you'll want to use a hybrid system. Use the 3-4kw of panels with a hybrid inverter and a battery bank. You can set up the inverter to utilize solar first if you want to avoid some efficiency losses, but then your solar production will be at levels low enough that the j1772 charging won't engage (1.3-1.4kw minimum) - so you'll want it to be charging the batteries when at the lower output.

I live off-grid myself. I have appx 8kw of panels and 32kwh of battery. I don't generate enough to charge at home as well as live. In the summer, when AC is not needed, I could potentially get a few kwh in. It just isn't worth the expense to me to go further since I charge at work at no cost to me.

 

[CharonPDX]

I assume he means he would be setting up more at camp.

As far as your trailer...are they older panels? I feel like I've heard way more on smaller. Heck, I have 620W on my little Tab400.

I see yours wrap all the way to the front - mine (also Tab 400) are only on the back half. What peak production do you see? (I'm guessing if you park "back end South" the front one doesn't do as well as the rear.) - I'm assuming it's 620W "theoretical peak", so curious if you get 300, 400, 500. Or is it 620W in reality, and it's actually "1000W peak" or something? (I'm thinking about adding more to mine, and replacing my lead-acid with a Li-Ion.)

 

[HyperionMark]

I see yours wrap all the way to the front - mine (also Tab 400) are only on the back half. What peak production do you see? (I'm guessing if you park "back end South" the front one doesn't do as well as the rear.) - I'm assuming it's 620W "theoretical peak", so curious if you get 300, 400, 500. Or is it 620W in reality, and it's actually "1000W peak" or something? (I'm thinking about adding more to mine, and replacing my lead-acid with a Li-Ion.)

I think like 350-400W would be peak since they wrap a bit like you said. But that design also allows for a good 100+W during most daylight hours. Also has a spot to add more via a SAE connection on the side.

 

[CharonPDX]

I think like 350-400W would be peak since they wrap a bit like you said. But that design also allows for a good 100+W during most daylight hours. Also has a spot to add more via a SAE connection on the side.

That's the one annoying thing about my setup - mine was shipped without solar, it was added aftermarket by a previous owner. They did an excellent job, but there's nowhere to connect extra panels. (Unless I feel like running bare wires into the screw terminal block on the solar controller in the closet.)

 

[MarcyB]

We have 1500W of solar on our travel trailer roof, and we use the excess to level 1 charge our Rivian. In a good month (not too hot or cold, plenty of sunshine, time to manage the charging) we can send 30-60 kWh to the truck. It's not much but it's something.
https://allelectricproject.com/

I think the main thing I see is that there are a lot of electronic pieces between the panels and the truck battery, all of them take energy, and the truck itself is quite inefficient at bringing in level 1 power. We used to have a Chevy Bolt, and charging from the solar panels made a real difference in adding miles. Not so much with the Rivian (and I don't think it's only the difference in driving efficiency). Again, better than nothing.

Also a good backup (backup, backup) plan if we ever get too low on truck battery level while towing - we could always sit somewhere for days to add enough juice to limp to a charging station Hopefully we never have to test this in real life!

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