Misguided article by Outside Magazine

[SeaGeo]

I have a question about battery efficiency. I currently get about 300watts/mile on a 7 year old 70d with 70k miles on it. I realize that the Rivian is inferior aerodynamically and has more weight but I would think that after 7 years of work on battery technology they would have been able to compensate for the above and match that 300 w/mi . Any thoughts on this?

Yes, that's unrealistic. Generally speaking EVs are quite *efficient*. For example, most EV motors are apparently around 90%+ energy efficient. Going from 90% to 95% doesn't leave a ton of room to increase efficiency. Increasing the voltage can help by reducing weight and heat loss (part of the reason Lucid went that way). Cutting weight helps in stop/go and slope speed. Hence the Lightning consumes less energy in the city rating than the Rivian, but consumes more in the highway rating than the Rivian.

I'm being a bit pedantic here, but I think it's somewhat important to note that consumption (300 wh/mi) isn't really efficiency. Two cars could have totally different energy efficiencies (say 80% vs 95%) while both consuming 300 wh/mi.

That being said, to answer your question more directly, look at the efficiency of a modern model S. Going from a 2017 S to a 2022 S you're reducing consumption fro 333 wh/mi to 285. The S is about 2,000 lbs lighter than a Lightning, has a significantly smaller cross sectional area and more aerodynamic shape, and is going to have lower rolling resistance tires given the different use cases between a car and truck.

Let's do a simple comparison. The S has a drag coefficient of about 0.21. Let's assume a highly aero truck with a bed would have a cd of about 0.3. Let's also assume that the truck has the same cross sectional area as the model S (which it obviously doesn't). At highway speed the vast majority of energy goes to pushing air out of the way. So let's figure out how efficient a current model S drive train would have to be to have the fictional truck version of the S achieve 333 wh/mi.

X wh/mi *0.3/0.21 = 333 wh/mi (target). Do some arithmetic and that lands at 212 wh/mi, which is much less than 285 wh/mi. That doesn't account for the added size, weight, or rolling resistance associated with a truck.

Now, let's take the current S efficiency and try to scale it for size and drag.I'll use the gross area of the R1T and S for simplicity in estimating the areas.

285 wh/mi *0.3/0.21 * 3.3m^2/2.6m^2 = 516 wh/mi. So right around 1.9 to 2 mi/kwh. The R1T is rated at about 480 wh/mi. So that gives about a 7% error on the estimate, well within the uncertainty the actual cross section area dimensions of each and the drag coefficient. But, it suggests that the R1T has an efficiency that's very similar to the current gen model S. And maybe a bit better.

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[RoadRunner]

I read the article shortly after it was published, and had many of the thoughts posted above. The author does seem to have some credibility with ICE off-roaders/overlanding etc but is kind of a fringe case due to his location and lifestyle, and his opinions reflect that.

He's right that current EV trucks are not ready for his fairly extreme overlanding use-case, but his critics are also right that it's unreasonable to expect that the first generation EV trucks would be. They'll get there eventually, likely sooner than he thinks. Battery tech should evolve pretty rapidly to increase range and decrease charging time. And hopefully decrease weight as well.

I'm not sure how decreasing their speed limit would change much though...how fast they are seems more an inherent advantage of electric motors with little downside if used judiciously. I'm not sure going down to 1 motor with a bunch of extra parts (differentials, etc) would be an improvement. Seems like software could fix the off-road traction issues he talks about, with a lot less added weight/complexity.

And smaller, lighter off-road EV's should be coming s00n, from Ford, Jeep, and Rivian among others. Hopefully with 400-500+ miles of range. Things are changing rapidly. I really wanted the R1S with max pack and would be happy with 2 motors but will end up with the large pack and 4 motors since that's what's available in the near term. I'd be happy with a smaller version too with better efficiency (I don't need 3 rows of seats) but that's not available either...

 

[Fred6v]

Better battery tech is on the way. Check the electric viking on YouTube and his many articles abt BYD's blade battery tech which is not only lighter and energy dense but is also LiPho4 which has 2-3x the charge life than the NCD cells used in the R1T. Waiting for my max pack in 2H '23.

 

[dfx]

Yes, that's unrealistic. Generally speaking EVs are quite *efficient*. For example, most EV motors are apparently around 90%+ energy efficient. Going from 90% to 95% doesn't leave a ton of room to increase efficiency. Increasing the voltage can help by reducing weight and heat loss (part of the reason Lucid went that way). Cutting weight helps in stop/go and slope speed. Hence the Lightning consumes less energy in the city rating than the Rivian, but consumes more in the highway rating than the Rivian.

I'm being a bit pedantic here, but I think it's somewhat important to note that consumption (300 wh/mi) isn't really efficiency. Two cars could have totally different energy efficiencies (say 80% vs 95%) while both consuming 300 wh/mi.

That being said, to answer your question more directly, look at the efficiency of a modern model S. Going from a 2017 S to a 2022 S you're reducing consumption fro 333 wh/mi to 285. The S is about 2,000 lbs lighter than a Lightning, has a significantly smaller cross sectional area and more aerodynamic shape, and is going to have lower rolling resistance tires given the different use cases between a car and truck.

Let's do a simple comparison. The S has a drag coefficient of about 0.21. Let's assume a highly aero truck with a bed would have a cd of about 0.3. Let's also assume that the truck has the same cross sectional area as the model S (which it obviously doesn't). At highway speed the vast majority of energy goes to pushing air out of the way. So let's figure out how efficient a current model S drive train would have to be to have the fictional truck version of the S achieve 333 wh/mi.

X wh/mi *0.3/0.21 = 333 wh/mi (target). Do some arithmetic and that lands at 212 wh/mi, which is much less than 285 wh/mi. That doesn't account for the added size, weight, or rolling resistance associated with a truck.

Now, let's take the current S efficiency and try to scale it for size and drag.I'll use the gross area of the R1T and S for simplicity in estimating the areas.

285 wh/mi *0.3/0.21 * 3.3m^2/2.6m^2 = 516 wh/mi. So right around 1.9 to 2 mi/kwh. The R1T is rated at about 480 wh/mi. So that gives about a 7% error on the estimate, well within the uncertainty the actual cross section area dimensions of each and the drag coefficient. But, it suggests that the R1T has an efficiency that's very similar to the current gen model S. And maybe a bit better.

Thanks. That was a very detailed response/answer that pencils

 

[R1Simon]

Wes wrote a BS article about Rivian being vaporware after the initial reveal. Here’s a brief snippet: “Bollinger appears to be in a very similar position to Rivian. The big difference between all of the above and the R1T appears to be Rihanna.” That article was just as painful to read as his most recent - riddled with false assumptions and disingenuous attacks.

 

[RoadRunner]

The dude is seriously conflicted, and his articles reflect that as well. He likes the idea of the perfect EV overlanding truck but isn't ready to give up the ICE trucks he's familiar with until the EV one outperforms the ICE truck in every possible way. He's also really skeptical of startups and their marketing (appropriately so, in many cases). But that older article from 2018 hasn't aged all that well. Here's how he ended it:

"It looks like Rivian has the pieces in place to find success in that environment. It’s just not clear if that success will actually involve putting the R1T or R1S you see here in your driveway."

 

[Monkey]

They kind of lost me with their first bullet point:
The Problems with EV Trucks

• Extreme complication equals a nearly endless list of potential failure points. And anything that can break will break off-road.

Written by someone who has no clue how EVs work and has probably never turned a wrench on an ICE vehicle in their life, especially on anything "off-road".

 

[Bobthebuilder352]

A valid concern against EV’s is lack of user serviceability. I’ve got an old 21” gas lawnmower that I can fix every inch of when something breaks. The electric one I’ve got, I’ll probably end up throwing it away whenever that breaks. That said, all cars are more and more less user serviceable these days but I’m not *scared* of the moving parts in my wife’s Acura like I will be of just about all of the non-moving parts in the Rivian when I get it and the fact of it not moving doesn’t mean it’s more reliable.

 

[ajdelange]

the fact of it not moving doesn’t mean it’s more reliable.

Yes, in general, it does.

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