Is this efficiency drop normal?? (First road trip)

[NC-Rivian]

Welcome to EV driving! Book numbers are only theoretical which are intruded upon by real world conditions. Owning both a Tesla Y and an R1T I can tell you that at least the Rivian guess-o-meter is pretty close … the Tesla‘s isn’t close to being realistic.

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[Bearmountain]

I usually prefer to hover between 10 and 15 above the speed limit, but when I saw how fast we were burning through the battery I backed off to 70 max and tried to draft.

80mph takes almost twice as much energy as 60mph wind resistance is a function of the square of the speed. And head wind makes it that much worse. What's your hurry.

 

[Ladiver]

Nobody else has mentioned it, but RAIN! I have had a noticeable decrease in wet weather. Add to that high speed and headwind and I think you did quite well.

 

[LL75]

we did quite a few of Dallas to Norman these past summer. Here is our last trip. All of these are conserve with 21" without aerocover. . Yesterday was the first day weather got around 40 degree so it definitely be the factor for you. The top picture is Norman to Dallas. (no traffic). Bottom is Dallas to Norman.

 

[R1Thor]

Not sure if you drive with any (exterior) accessories, but pulling them off helps too.

It goes without saying for most, but if you hadn't considered it, remove any cross-bars/roof-luggage racks, etc.

It's been getting colder up here in the northeast and I was doing gravy all summer doing 80-85 to/from work with mudflaps and Rivian cargo crossbars. Took them both off to get back to summer efficiency numbers with the colder temperatures.

YMMV

 

[Zoidz]

80mph takes almost twice as much energy as 60mph wind resistance is a function of the square of the speed. And head wind makes it that much worse. What's your hurry.

When I see posts about "poor EV efficiency" and they post that they were driving 75 - 80 mph, I'm always a bit surprised that people never noticed/understood the same 60 vs 80 impact with their ICE vehicles. It seems to be a surprise with an EV. Don't people notice they have to fill up with dinosaur fluid more frequently at higher speeds?

 

[Whataboykie!]

I have the perfect solution for you. Move to Florida! Mostly flat and never cold.

 

[Doctorjorts]

Thank you all for the replies - I was mostly surprised at how big a difference their was from the same speed, where the only changes between the two legs of the journey was a) headwind and b) temperature drop to 45-50degF. 1.8mi/kwh was definitely the higher end. Most of the trip was less than 1.5mi/kwh. I had no outboard luggage or racks to affect wind resistance, for reference.

Thank you to the reply that referenced the temperature graphs. I assumed/hoped that the temperature effects would be less pronounced above freezing temps, but even going from 80degF to 60degF there was some real range loss. It was surprising to this neophyte, anyway.

I’m planning to drive around town (mostly highway, mostly in traffic fwiw) the next few days while it’s still cold, without making any changes (leave the tires at 40psi, aero covers on) to see if the headwind was the biggest factor, or cold.

 

[Marchin_MTB]

When I see posts about "poor EV efficiency" and they post that they were driving 75 - 80 mph, I'm always a bit surprised that people never noticed/understood the same 60 vs 80 impact with their ICE vehicles. It seems to be a surprise with an EV. Don't people notice they have to fill up with dinosaur fluid more frequently at higher speeds?

I think it’s because ICE becomes more efficient at higher RPMS so, unlike an EV, there is an optimal speed for efficiency resulting from the increading engine efficiency balanced by increased drag. It’s also related to the fact that drivetrain inefficiencies in an ICE usually swamp other factors. But yes, you should still notice 70 vs 90 mph differences no matter what your driving.

 

[strykerwsu]

We did our first road trip this weekend with the R1S. (First BEV road trip of any kind!) Drove from Oklahoma City to Fort Worth on Friday night, and back this evening. That’s a 200mi trek which is 3hrs straight through, or 3.5-4 if you have young kids like us. The trip is almost completely level, according to my buddy with a tesla.

On 21s with the aero covers in conserve mode, I was disappointed in our range. On the way there it wasn’t terrible. I did about 2.2mi/kwh and the trip took us 70% of our large pack battery SOC. So on the way back we left with 90% SOC, and we had a direct headwind the whole time, and added 44kwh at a dcfc halfway because we weren’t going to make it home. According to weather.com the wind was 15mph, but at the charge-up the rain was coming down sideways and I bet it was closer to 25. Struggled to get more than 1.8mi/kWh and usually lower than 1.5 unless I was drafting behind a semi. It was a little chilly but never less than 40degF even towards the end tonight, and my tires were a little lower than the recommended 48 because of the cold, but still over 42psi.

So is this huge drop in range expected from a headwind alone?

Also, in the gauge view I could see the front motors nearing overheating in conserve mode, such that the bar turned orange and the diagram of the vehicle turned orange near the front motors, too. Is that expected as well? I never got any warnings on the dash but when we knew we had no range worries I switched over to all-purpose mode.

Yes, with all factors noted, 80mph, under 50 degrees, headwind, and under inflated tires sounds about right. Your ICE vehicle is very similar in loss but we don't notice as have so many Refuel options and quicker to fuel.

I did a trip earlier from Wichita to Springfield with my RTT setup and 21s. Low winds and 75 degrees way out. Got 2.2 and was really happy with numbers with RTT impact expected. Way back headwind, 30 degrees and was under 1.5. Plugshare saved me as small-town had a 50 kwh charger.

 

[Stumpjumper]

Rivian actually has a great Coefficiant of Drag for a truck, 0.3 or just above: https://insideevs.com/news/611642/rivian-r1t-aerodynamics-drag-coefficient-simulatiion/
Also, when looking at efficiency it is better to work in Kwh/Mile. I assume Rivian shows Mi/KwH because people have grown accustomed to MPG, but it has a non-intuitive impact on your understanding of efficiency.

 

[YellowR1T]

I’ve recently been getting crappier efficiency. I’ve started to wonder if they changed the meters. It’s not that cold.

My Last 300 miles are at 1.75. My lifetime is 2.11.

How do you find the lifetime efficiency number?

 

[sub]

Thank you all for the replies - I was mostly surprised at how big a difference their was from the same speed, where the only changes between the two legs of the journey was a) headwind and b) temperature drop to 45-50degF. 1.8mi/kwh was definitely the higher end. Most of the trip was less than 1.5mi/kwh. I had no outboard luggage or racks to affect wind resistance, for reference.

Thank you to the reply that referenced the temperature graphs. I assumed/hoped that the temperature effects would be less pronounced above freezing temps, but even going from 80degF to 60degF there was some real range loss. It was surprising to this neophyte, anyway.

I’m planning to drive around town (mostly highway, mostly in traffic fwiw) the next few days while it’s still cold, without making any changes (leave the tires at 40psi, aero covers on) to see if the headwind was the biggest factor, or cold.

Speed / wind has a much, much bigger impact than temperature.

The impact that a headwind has is very easy to calculate. As others have noted air resistance is proportional to the square of the speed. ( 70MPH + 15MPH headwind) ^2 / ( 70MPH - 15MPH tailwind) ^2 / = 2.3

Switching from having a 15mph tailwind to a 15mph headwind will more than double the air resistance. Air resistance the biggest consumer of energy, so yes wind can have a huge impact on your range. This isn't an EV thing. A gas car would also burn 2x as much fuel when dealing with a headwind vs a tailwind.



Based on the data from my Tesla, temperature's impact is much smaller. It does add up, but to double consumption like switching from a 15MPH tailwind to 15MPH headwind can do you are looking at seriously cold temperatures.

 

[elektrode]

How do you find the lifetime deficiency number?

Sorry, that’s misleading of me. Basically you have to dedicate Trip B as your “lifetime” and never reset it.

 

[Blackrock2014]

I only have my R1T on order, but I have been driving Tesla's for many years. Headwind + high speed + raining sideways + cold = very poor efficiency. I am actually quite impressed with the numbers you got. In my experience, nothing zaps more battery then cold. Next worst is speed.

The good news is that in cold and rain we should all drive slower. Too many lives at stake and vehicles (especially Rivian's weight) are like dangerous weapons so to speak. Leave a couple minutes earlier and get there a couple minutes later, and we all save lives.

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