Towing efficiency increase if I don't plug in harness?

[shamoo]

This weekend I was towing a ~450 lb trailer with a ~310 lb dual-sport motorcycle. The Rivian estimated the trailer weight at about 500 lbs.

The trip was ~85 miles each way. Under normal circumstances, I can make that round trip without charging and still have plenty of range remaining. As soon as I connected the trailer wiring, before the weight even registered, the efficiency estimate dropped significantly (which I suppose is expected).

What surprised me is that this isn't a heavy or large setup. The trailer is relatively low profile and the total weight isn't substantial. Am I crazy for thinking Rivian is building a large buffer into its towing efficiency calculations, and that the projected range loss may be more pessimistic than reality? In my head, I wouldn't expect a setup like this to have such a significant impact on range, yet I ended up needing to charge twice.

I'm also curious, if I had towed the exact same setup without plugging in the trailer wiring (obviously not something I'd actually do since I'd lose brake lights and turn signals), would the truck still have experienced the same range loss? In other words, is the reduced estimate simply because the vehicle knows a trailer is attached, or is it accurately reflecting true efficiency hit?

I'm well aware towing with an EV results in poor efficiency, but this was surprising to me.

Note, I've towed heavier loads before and I've gotten similar efficiency results, but this was not expected.

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[LivingInKaos]

Keep in mind, the vehicle has absolutely no way of knowing what the trailer dynamics are (aerodynamics, wheel drag, etc), only calculated weight. So when you start, it has some default efficiency it works with for the weight calc. If you set up a specific trailer profile for that trailer only, it will adjust the more you apply to that profile based on history.

 

[Dark-Fx]

Projected range loss is exceptionally optimistic for anything I have towed. Only way I could see an actual increase here is if you're a dual motor vehicle or using conserve mode, since towing forces AWD

 

[VSG]

Projected range loss is exceptionally optimistic for anything I have towed. Only way I could see an actual increase here is

Initial projection has always been exceptionally pessimistic for me. I've only towed maybe 4 different times, and I believe it always used to start at guessing range would be cut in half, but as it learned it always went up for me. Towing a sedan on a flatbed trailer, total weight 6000 lbs, for example, it eventually leveled off at 75% of the EPA range. So the initial estimate was low, as it should be.

 

[VSG]

I'm also curious, if I had towed the exact same setup without plugging in the trailer wiring (obviously not something I'd actually do since I'd lose brake lights and turn signals), would the truck still have experienced the same range loss?

Yes.

 

[antimatter]

When I'm towing my InTech Sol Dusk (with a much higher profile than your cargo trailer), I actually get a slightly more optimistic range estimate that what I actually get. My R1T will estimate 1.1-1.2 miles per kWh, but I'm usually closer to 1.0 when all things are said and done.

 

[CharonPDX]

... before the weight even registered...

That answers it right there. The Rivian had no way of knowing what trailer you plugged in, what efficiency it would have, etc. It just knows "a trailer has been plugged in, so I'm going to do my normal "cut range in half" estimation until I know the trailer better."

It's not that your actual efficiency will increase if you tow when unplugged, it's just that the vehicle won't know that you're towing, and won't adjust its estimates.

 

[HaveBlue]

The weight matters less than the wind resistance/drag. How far you'll go also depends on your battery size and how fast you drive. With those factors in mind, ymmv.

 

[CommittotheIndian]

Aerodynamics of the trailer makes the difference in towing. Weight plays very little on effieceny.

 

[shamoo]

Good info, thanks everyone.

I drove 7 miles back to my friend's house to return the trailer and I did NOT plug in the harness.

Anecdotal data for sure:
- Efficiency was over 2 mi/kwh, but over a shorter distance, not on a freeway, bike not in trailer.
- Previously it was 1.5 or lower, over a longer distance, bike in trailer.

Interesting for sure. Aero definitely at play, but my thinking was the bike is so small (it is a small dual sport and narrow).

You guys are right, but the whole thing is contrary to what I thought it would be. I wasn't towing a giant 12' high RV or a 10K load.

 

[SwampNut]

I've towed several motorcycles for many hundreds of miles, as well as carrying them in the bed. Aero is the problem of course. My dual sport is ultra light, and has a massive effect in the bed, because it's also ultra tall (XR650R). There's no trailer to plug in but the Rivian eventually calculates the new range.

The street bikes with a trailer also have a major effect, or even just the trailer.

Funny story, I took the empty trailer with the Tesla to San Diego to pick up the electric bike shown here. On the uphill side of the 5k foot pass, it showed range as <40, and the next charger was 72 miles away. On the down side, it showed 999 miles of range. I skipped two chargers and was still fine. You may be having range anxiety as you see the numbers change. They will vary more than without the load.

Oh, and that food wrap...saved a LOT of energy! I took it off nearing home, and ate another 5% or maybe up to 9% more energy.

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