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We Need Trailer & Camper Manufacturers To Publish Data On EV Range Impacts

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In the next few months, I’m planning on buying a camper. Unlike most Americans, I’m not looking for the triple-axle fifth wheel with three king beds, two living rooms, and a better kitchen than my home (plus a garage for UTVs). I’m looking for something I can tow behind my Bolt EUV (which I call my Bolt EAV). Not only is it cheaper to drive an EV on trips, but EVs have big batteries that can be used to power campsites!

But, there’s one big downside to towing with an EV: range loss. When you’re already driving a vehicle that doesn’t have the best range, having your range cut in half (or worse) can really put a damper on trips. Sure, it’s no big deal towing on gas, because there are gas stations everywhere and you can even take a jerry or two along for extra range out in the backcountry. But, when charging stations generally only exist along the interstates, and some places out in the woods don’t have electricity at all, that hit to range is a much bigger problem.

But, there’s no easy way to really predict the range hit a trailer will have on your EV.

If you’re really lucky, someone else already has your same vehicle and has towed the same trailer you want to buy. When that happens, you can know pretty much what to expect and maybe even put the numbers into something like A Better Routeplanner to plan your trips. But, if you want to tow something that nobody has shared the data on, it’s anybody’s guess how much range you’ll lose.

What makes this problem even more complicated is that efficient camper designs can be deceptive. Some designs that you’d think would give you great efficiency don’t really pan out. For example, there are many “teardrop” designs that start with good science, but don’t quite get the proportions right, resulting in a design that doesn’t preserve range like it should. Plus, many other factors, like axle bearings, tires, wheels, and the shape of the tow vehicle factor in and can give unexpected results even with sound designs.

So, if you’re shopping for a cargo trailer, a camper, or any other towable vehicle, you’re playing an iffy game. If you’re lucky, the trailer does better than expected, and you can go more places than you anticipated. If your luck isn’t great or you fall for junk science in marketing, you could suffer a much greater range loss than you’d hoped for, and not be able to get to the campsites or business destinations you’d planned on.

The Ideal Way To Know For Sure

Want to get rid of the uncertainty? There’s a great way to do that with any EV.

Start out by getting the premium version of A Better Routeplanner and buying an OBD-II Bluetooth dongle to connect your smartphone to the car (some vehicles can do this without the Bluetooth dongle). Create a custom version of your vehicle in the app, making note that it’s the one towing the specific trailer.

Then, take the trailer on some test runs, preferably with a variety of speeds along the route. Do a mix of city, urban highway, and rural highway driving between DC fast charging stations 50 miles apart so you won’t risk running out of range. Then, check and see what the reference range figure is inside the app.

You can compare that reference figure to your car’s normal reference figure to determine the approximate percentage of range lost towing that specific trailer, and use that same reference figure to plan towing trips ahead of time.

Trailer Manufacturers Will Need To Start Doing This, Though

While the above method would work great, there are some significant problems with it when you’re shopping for trailers.

The biggest problem is that almost nobody’s going to let you test tow a trailer. RV dealers, cargo trailer builders, and boat shops aren’t going to let you go drive 50-100 miles with their vehicle to get that precious data. If you wreck it before buying it, they don’t know that your insurance will cover it, and they don’t want to deal with the hassle even if they could be sure. They’re certainly not going to pay for the insurance that it would take to cover customer test tows.

Eventually, trailer and RV businesses are probably going to need to start doing test tows, but when they’ve got ICE-driving customers coming in every day, it makes little sense to go out of their way to accommodate the odd EV driver.

You might be able to work around this by renting a trailer, but it needs to be a trailer that’s basically identical to the one you’re considering buying for the test data to be useful at all. Other variables like tires, aerodynamics, whether the bearings were maintained properly, and many other things can shift the results.

So, if you’re shopping trailers, you’re probably not going to be able to test it yourself. But, as more and more drivers have EVs, manufacturers are going to need to consider collecting some data themselves to give to prospective buyers.

Generalizing Test Results For All EVs

The problem with the above testing method is that it’s not all that useful for vehicles other than those identical to your own, or to those used in a specific test.

If I tow a specific trailer with my Bolt EAV and you tow it with a Tesla, we could get very different range losses. The back of the Bolt’s hatch is a lot taller, and Tesla’s vehicles tend to have a lower deck, making for better aerodynamic efficiency for the Tesla. But, when that more sloped back end releases the air and sends it flying back to the trailer, the air that the trailer is riding through is now completely different. In some cases, the Bolt will be a better match for the trailer because the trailer rides in the slipstream more. But, there’s no guarantee.

So, trailer manufacturers need to think about how they’re going to collect and share towing range test data so that it will be useful for more drivers.

The best way to do this would be to test with common and popular EVs. There’s no way to cover every EV someone might tow the trailer with, but testing with a variety of EV shapes (car, hatchback, SUV, truck) and publishing results with each vehicle can at least help prospective trailer buyers get in the ballpark before buying.

Instead of publishing the overall range loss (ex. “This car only goes 105 miles towing”), it’s probably a good idea to publish the extra watt-hours per mile and/or reduced miles/kWh that happens when towing vs driving the same course unloaded. In other words, it’s good to publish the percentage of extra energy needed and not the overall range reduction on a given vehicle. This would make it possible for people to extrapolate the range loss to EVs with different battery pack sizes.

Finally, it’s probably good to come up with a good average after testing several different types of electric vehicles. The average won’t be useful for EV buyers directly, but having overall averages for different trailers can give customers an idea of what trailers are better for EV towing.

How This Helps Move The Industry Forward

Perhaps most importantly, encouraging EV range testing would be great for the future development of EV-friendly trailers. When there’s a basis to compare towing energy efficiency, manufacturers will feel more motivation to create better trailers. As the EV transition goes forward, this will be an important part of the towing and RV industries, so it makes sense for manufacturers to start laying the groundwork now rather than later.

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Written By

Jennifer Sensiba is a long time efficient vehicle enthusiast, writer, and photographer. She grew up around a transmission shop, and has been experimenting with vehicle efficiency since she was 16 and drove a Pontiac Fiero. She likes to get off the beaten path in her "Bolt EAV" and any other EVs she can get behind the wheel or handlebars of with her wife and kids. You can find her on Twitter here, Facebook here, and YouTube here.


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