Why it's time to get over your EV range anxiety [Arstechnica]

[Tommm]

..For people (like me) who rarely go on road trips above 250km, a city car is all you need and is far better than carrying around batteries that are never needed. ...

I too don't want to drag around unnecessary weight. That is why I tossed the cigarette lighter years ago. And of course I don't keep the owner's manual in the car. Just dead weight that has no use to the 99.44% of the population that doesn't bother to open it because they know everything. Rear floor mats are another thing. I'm glad BMW stopped supplying them. Nobody sits in the back anyway. Just dead weight.

"When I drive my EV to work, it's uphill both ways in the snow!"

With bare feet or in this case bald tires, and no heat (a la Beetle).

 

[Puppethead]

Lucid air: 4,630 lb (and 3.9mi/kWh)

Wait what, the much-vaunted Lucid Air is no more efficient than the much-derided SE (personally I get over 5 mi/kWh in the summer)? That's interesting. Not knocking the Air, but maybe MINI should be talking up the engineering of the SE more.

It sure would be nice if there was some comparison of all EV models by efficiency instead of just range.

 

[Carsten Haase]

Wait what, the much-vaunted Lucid Air is no more efficient than the much-derided SE (personally I get over 5 mi/kWh in the summer)? That's interesting. Not knocking the Air, but maybe MINI should be talking up the engineering of the SE more.

I'm sure you'd be getting much better than the rated efficiency in the lucid but definitely pretty crazy that the MINI is 0.02mi/kWh (rated) better than the lucid even with it's rather poor ~0.3 drag coefficient! Just goes to show a major advantage of small cars, the area part of the drag equation is just as important as the drag coefficient.

It sure would be nice if there was some comparison of all EV models by efficiency instead of just range.

Thanks to @fishbert for the site, you can sort by efficiency here:

EV database

 

[Brawndo]

It's almost like they should make more than one car since people have different use cases, budgets, priorities, and desires or something.

 

[yoomini]

8 months of ownership with the SE and have come to the realization that an SUV is completely unnecessary for my family (me, wife, toddler, and our little chihuahua). Feel good not having to lug around extra battery for no reason.

 

[fishbert]

Battery size and weight have a small effect on efficiency

O, RLY?

Weiss, M.; Cloos, C.K.; Helmers, E. Energy efficiency trade-offs in small to large electric vehicles. Environ. Sci. Eur. 2020, 32, 46

Results
Certified and real-world energy consumption of electric vehicles increase by 60% and 40%, respectively, with each doubling of vehicle mass, but only by 5% with each doubling of rated motor power. These findings hold roughly also for passenger cars whose energy consumption tends to increase 0.6 ± 0.1 kWh/100 km with each 100 kg of vehicle mass. Battery capacity and vehicle mass are closely related. A 10 kWh increase in battery capacity increases the mass of electric cars by 15 kg, their drive range by 40–50 km, and their energy consumption by 0.7–1.0 kWh/100 km.

Conclusion
Mass-related efficiency trade-offs in electric vehicles are large...
​

Berjoza, D.; Jurgena, I. Influence of batteries weight on electric automobile performance. Eng. Rural Dev. 2017, 16, 1388–1394

Conclusions
5. Luxury class electric automobiles with a high basic weight, e.g., Tesla Model S (85), demonstrated the highest energy consumption per km travelled – 200 Wh·km-1. This parameter was, on average, two times higher than that for the compact class electric automobiles Renault Zoe and BMW I3.

6. The experiment on an electric automobile, imitating an increase in its weight by 270 kg that corresponds to the average weight of a 22 kWh battery pack, showed that the period of acceleration to 90 kmh-1 and 50 kmh-1 increased by, one average, 29.8 %. The automobile’s acceleration to 90 kmh-1 with an extra load on an experimental road section required a 28 % longer distance.

9. In the experiment, the electric automobile’s range per charge in the urban driving regime in Jelgava decreased by 8.2 %. [with 270 kg increase in weight]​

Mruzek, M.; Gajdáˇc, I.; Kuˇcera, L.; Barta, D. Analysis of Parameters Influencing Electric Vehicle Range. Procedia Eng. 2016, 134, 165–174

Conclusions
From the simulations results that the vehicle weight and size of the battery pack have the main impact on the range. Vehicle weight increases directly with battery capacity. In the case that the electric vehicle has high capacity battery pack and is used for short distances for example EV with 24 kWh battery pack for 70 km range the vehicle is less efficient than the same vehicle with 8 kWh battery pack. In this case the EV with smaller battery pack is more efficient because of 1.17 km higher range achieved from 1 kW of energy. ... The result from the comparison of vehicles operating in urban traffic where the speed rarely exceeds 50 km/h is that the aerodynamic drag coefficient has not a major impact to the range.​

 

[teslarati97]

So what we all learned is if you want to get maximum efficiency on the highway, you should be setting the cruise control to 31MPH (50km/h). Now you can make the one-way 150 mile MINI SE trip in 4.8 hours WITHOUT charging!! #highwayhypermiling

 

[fishbert]

So what we all learned is if you want to get maximum efficiency on the highway, you should be setting the cruise control to 31MPH (50km/h). Now you can make the one-way 150 mile MINI SE trip in 4.8 hours WITHOUT charging!! #highwayhypermiling

I know, it's a funny joke ... but go take a look at what your trip computer says your average speed has been. ¯\_(ツ)_/¯

 

[Carsten Haase]

Pretty simple, correlation does not mean causation.

Weiss, M.; Cloos, C.K.; Helmers, E. Energy efficiency trade-offs in small to large electric vehicles. Environ. Sci. Eur. 2020, 32, 46

Results
Certified and real-world energy consumption of electric vehicles increase by 60% and 40%, respectively.​

This study is comparing mass to energy usage. It demonstrates a correlation, not a causation. Energy use does absolutely increase with mass but it's not because of mass. Bigger things are heavier. Bigger things have more aerodynamic drag. Of course a 15mph electric kick scooter uses less energy than a car on the highway.

Berjoza, D.; Jurgena, I. Influence of batteries weight on electric automobile performance. Eng. Rural Dev. 2017, 16, 1388–1394

They added some weight to a car and found an 8% reduction in range. Adding a significant amount of weight to a chassis (and tire) not adequately designed for it could definitely increase rolling resistance. Did they even adjust the tire pressure?
Besides, their own chart shows no correlation between vehicle weight and efficiency:

Mruzek, M.; Gajdáˇc, I.; Kuˇcera, L.; Barta, D. Analysis of Parameters Influencing Electric Vehicle Range. Procedia Eng. 2016, 134, 165–174

Conclusions
From the simulations​

This is a paper discussing a simulation published in a non-peer reviewed journal intended to be used for conferences. Not exactly credible.

"Procedia Engineering is an e-only product focusing entirely on publishing high quality conference proceedings."

"Organizers are being credited on the actual issue and are fully responsible for quality control, the review process and the content of individual conference papers."

 

[fishbert]

This study is comparing mass to energy usage. It demonstrates a correlation, not a causation. Energy use does absolutely increase with mass but it's not because of mass.
...
They added some weight to a car and found an 8% reduction in range. Adding a significant amount of weight to a chassis (and tire) not adequately designed for it could definitely increase rolling resistance. Did they even adjust the tire pressure?
Besides, their own chart shows no correlation between vehicle weight and efficiency:
[chart]

You can't criticize one study, saying it shows correlation but not causation... then turn around and criticize another, saying it shows causation but not correlation. That's just taking potshots.

And btw, rolling resistance is not just a function of mass (Frr = coefficient * normal force; normal force = m * g on level ground), it's the precise mechanism for how mass affects the energy requirements of rolling bodies. So, of course adding mass could increase rolling resistance; that's what it do (as the kids say). "Did they even adjust the tire pressure?" Please.

Listen, you made a wild claim that flies in the face of basic physics: that mass does not have a significant effect on efficiency. I presented multiple studies concluding the exact opposite (though it's so fundamental a concept I shouldn't have to). Are you going to present any actual evidence in support of your claim, or will you just continue to Statler & Waldorf your way through this? I'm not particularly interested in the latter.

 

[polyphonic]

Lucid air: 4,630 lb (and 3.9mi/kWh)
EV6: 4,431 lb (and 3.9 mi/kWh)
Model S: 4,784 lb (and 3.7 mi/kWh)

Is that the EPA highway MPGe or the combined?

 

[Carsten Haase]

Is that the EPA highway MPGe or the combined?

Just the rated range divided by usable battery capacity to avoid any differences in accounting for charging losses (data from here: EV Database)

 

[Carsten Haase]

You can't criticize one study, saying it shows correlation but not causation... then turn around and criticize another, saying it shows causation but not correlation. That's just taking potshots.

I didn't say any of your studies showed causation, my entire point was that none of them showed causation. I said one of them just showed correlation and the other showed no correlation, with their own chart disagreeing with their conclusion. As said above by someone else, just because a study is published doesn't mean it's correct, especially when it's not peer reviewed like the 3rd one.

And btw, rolling resistance is not just a function of mass (Frr = coefficient * normal force; normal force = m * g on level ground), it's the precise mechanism for how mass affects the energy requirements of rolling bodies. So, of course adding mass could increase rolling resistance; that's what it do (as the kids say). "Did they even adjust the tire pressure?" Please.

I completely agree that adding weight to a specific car with no other changes will increase rolling resistance but that little coefficient you just glossed over is hiding a ton of other detail and is no where near constant. Just ask all of the forum members who have changed to high performance tires and lost 15-20% of their range (quite a bit more than the 8% lost by adding 600lbs in study 2).

Listen, you made a wild claim that flies in the face of basic physics: that mass does not have a significant effect on efficiency. I presented multiple studies concluding the exact opposite (though it's so fundamental a concept I shouldn't have to). Are you going to present any actual evidence in support of your claim, or will you just continue to Statler & Waldorf your way through this? I'm not particularly interested in the latter.

Please explain to me with this basic physics how multiple vehicles weighting 1000+ pounds more than the MINI can be just as efficient if weight causes such a significant increase in energy usage. Maybe you disagree but I consider real world efficiency of numerous heavy and light vehicles to be "actual evidence".

I have looked for a decent study but it seems neither of us can find one, at least one that's free. I have provided data but you seem to ignore those parts of my posts.

Lets review:

They took a sample from a metropolitan area (shorter trips), used an assumed 3.6mi/kWh (too high for most crossovers), didn't include weather/temperature effects, and ONLY 37.9% of drivers would have been able to make all of their trips with a 140mi range EV.

Including charging would definitely make that go up but that seems very low for pretty much an ideal case for a short range EV.

They also didn't look at other external factors that effect range:
Strap a bike, kayak, ski box, or other thing to your roof? Knock 20-50% off your range.
Unexpected headwind on the highway? -20%
Need to tow something? -50%

This was an observation about the original article, my source is the paper you posted. I did say 3.6 was high for a crossover/SUV and provided examples including my own data log showing just how much efficiency can vary from the on-paper rating. My original point was that the original paper overlooked many real world variables that would significantly alter their conclusion.

Lucid air: 4,630 lb (and 3.9mi/kWh)
EV6: 4,431 lb (and 3.9 mi/kWh)
Model S: 4,784 lb (and 3.7 mi/kWh)

All just as heavy as your list but as efficient as the MINI?

There is in fact another explanation to your thesis: aerodynamics. Many heavy vehicles happen to also be larger meaning more frontal area and more drag. They're also frequently styled like a brick making their drag even worse.

You pointed out that my example vehicles were heavy and assumed that's why they were inefficient so I provided data to the contrary with heavy but efficient vehicles. Providing data that conflicts with a thesis is usually how they are disproven.

I pointed out that there were some issues with the papers you were trying to use to prove your point, including the 2nd one showing a graph with no correlation between battery weight and efficiency and not even attempting to explain why. I'm sorry you took this legitimate criticism as heckling.

 

[fishbert]

I didn't say any of your studies showed causation...

But you did... right here:

"They added some weight to a car and found an 8% reduction in range."​

And then just now you admit:

"I completely agree that adding weight to a specific car with no other changes will increase rolling resistance..."​

I completely agree that adding weight to a specific car with no other changes will increase rolling resistance but that little coefficient you just glossed over is hiding a ton of other detail and is no where near constant. Just ask all of the forum members who have changed to high performance tires and lost 15-20% of their range (quite a bit more than the 8% lost by adding 600lbs in study 2).

Are you familiar with the concept of controlling variables? If you can lower the coefficient of rolling resistance on a large-battery EV, but haven't done the same on the small-battery EV, that's no longer a comparison of the effect of additional mass on efficiency; you've introduced a confounding variable. That's like comparing lap times between a base Cooper and a JCW, but the Cooper has racing slicks and the JCW is on donut spares.

Please explain to me with this basic physics how multiple vehicles weighting 1000+ pounds more than the MINI can be just as efficient if weight causes such a significant increase in energy usage.

Again, controlling variables. You like to point to aerodynamic drag... and yes, like mass, that also has a significant effect on efficiency (especially as speed increases). The MINI is shaped like a brick, with a 0.3 coefficient of drag; Lucid Air and Tesla Model S are both a comparatively slippery 0.2 ... and yet, no, they are not "just as efficient" as the Cooper SE.

I don't know where your numbers came from, but per ev-database.org the most efficient trim of each model is:
Kia EV6 SR: 1,875 kg (177 Wh/km) ... 4,134 lbs (3.51 mi/kWh)
Lucid Air GT: 2,360 kg (168 Wh/km) ... 5,203 lbs (3.70 mi/kWh)
Tesla Model S DM: 2,170 kg (167 Wh/km) ... 4,784 lbs (3.72 mi/kWh)
MINI Cooper SE: 1,440 kg (161 Wh/km) ... 3,175 lbs (3.86 mi/kWh)

It's worth noting that the EV6 has aerodynamics similar to the Cooper SE (controlling variables), and look how much worse the efficiency is. Ignoring differences in drivetrain losses and the like, you can see how the improved aerodynamics of the Lucid and Tesla help their efficiency relative to the Kia, but the still lower mass of the MINI keeps it in the lead.

Maybe this will be difficult to follow, and I don't know how strictly "valid" it is, but let's see how delta-mass x delta-drag tracks with delta-efficiency.
[CdA = drag coefficient x cross-sectional frontal area; cross-sectional area here is a pretty rough estimate using height x width]

EV6... 1.30 x Cooper SE mass ... ~1.10 x Cooper SE CdA ... 1.30 x 1.10 = 1.43 (43% higher mass ratio x drag ratio)
Lucid... 1.64 x Cooper SE mass ... ~0.74 x Cooper SE CdA ... 1.64 x 0.74 = 1.20 (20% higher mass ratio x drag ratio)
Model S... 1.51 x Cooper SE mass ... ~0.76 x Cooper SE CdA ... 1.51 x 0.76 = 1.15 (15% higher mass ratio x drag ratio)

EV6... 1.099 x Cooper SE Wh/km (9.9% higher energy consumption)
Lucid... 1.043 x Cooper SE Wh/km (4.3% higher energy consumption)
Model S... 1.037 x Cooper SE Wh/km (3.7% higher energy consumption)

EV6 / Model S... 43% / 15% = 2.9 ... 9.9% / 3.7% = 2.7 <-- pretty close
Lucid / Model S... 20% / 15% = 1.38 ... 4.3% / 3.7% = 1.17 <-- fuzzier with less separation, but also pretty close

In plain english:
Relative to the Cooper SE, the EV6 is 2.9 times worse than the Model S in mass x drag... and 2.7 times worse in efficiency.
Relative to the Cooper SE, the Lucid is 1.38 times worse than the Model S in mass x drag... and 1.17 times worse in efficiency.
This suggests the difference in relative mass x relative drag is proportional to the difference in relative efficiency. Pretty cool!​

I have looked for a decent study but it seems neither of us can find one...

Not that supports your claim, no.

I’m sure you’ll disagree, but I feel I’ve proven my point a couple times over by now. It’s basic physics; I’m not going to waste any more of my time on this.

 

[Puppethead]

I find it amusing that there are a lot of articles gushing about the Kia EV6 GT being so fun to drive because it has a smaller battery pack. Maybe the irrational "more range is needed" mentality is waning. We SE owners already know the value of a lighter EV.

 

[CuriousGeorge]

I find it amusing that there are a lot of articles gushing about the Kia EV6 GT being so fun to drive because it has a smaller battery pack.

77.4 kWh is "smaller"?

 

[Puppethead]

77.4 kWh is "smaller"?

Oh looks like I misread. The shorter range is due to the "more powerful" motors, not smaller battery pack. Well never mind then. It's just the opposite, the GT seems to be wasting battery to get performance instead of being lighter and more efficient like the SE.

 

[teslarati97]

Oh looks like I misread. The shorter range is due to the "more powerful" motors, not smaller battery pack. Well never mind then. It's just the opposite, the GT seems to be wasting battery to get performance instead of being lighter and more efficient like the SE.

Yes but the dual motors is integral to the 697V architecture as the rear motor acts as the 105kW brake regen during DCFC.

 

[AndysComputer]

It’s worth noting at if you genuinely used 80% of the EPA range of the asE in a daily basis that amounts to over 32,000 miles per year. Hardly anyone in the US does that kind of mileage.
If you change it to just commuting 5 days a week at 90 miles round trip that’s over 23,000 miles per year just for commuting which again, hardly any American does.
If you halve the commute to 45 miles round trip we’re at under 12,000 miles per year for commuting use which seems more in line with a large chunk of the population given the mileage they actually put on their vehicles.
That just leaves the weekend use which yes, may require a single charge while away from home to get back on such a day trip. That seems doable if we’re sticking to metropolitan areas, not so much if you travel into the middle of nowhere today.
As for towing, not many people do, even the majority of pickup truck drivers never tow, never mind frequently.
How often are people driving long distances with kayaks (or whatever) on the roof? Given how I frequently I see such a sight on the highway away from civilization I’m going to suggest not very. Edge case.
And very long multi day road trips are incredibly rare as few people can afford the time, the reality is most fly. And if you do drive but only do it once per year get used to the idea of renting a car for that trip instead of paying for a battery (or gas) the whole year when you don’t need to.
People (myself included) make very bad emotional decisions when buying cars, fueled by dreams of lifestyles we don’t actually have which is why so many families end up with SUVs when a minivan is a much better choice. But image matters more than money…
I daily charge our Long Range Tesla to just 60% and get back home on 50%. The range just isn’t needed except for once every 3-4 weeks when I travel across the state and have to charge to get back home. I could do it in the mini but I’d have to also charge once in the way there and once in the at back. Not ideal but do-able. And beyond that I only really make use of the cars capability once or twice per year when I do a multi state road trip just because I like to do such road trips (it would make more sense to fly) but I suspect I am atypical, and with the currently available range, Tesla charging infra and speed, a 9.5hr gas trip has become 10hours. Big deal. If the trip was not practical I’d fly and still have an EV like the mini for day to day use anyway.

 

[chrunck]

How often are people driving long distances with kayaks (or whatever) on the roof? Given how I frequently I see such a sight on the highway away from civilization I’m going to suggest not very. Edge case.

I drive with skis on the roof nearly every weekend in the winter, but I don't know how much that affects range. The place we go most often is about 160 miles, mainly back roads.

I told my FIL when he was building a giant garage last year to build in a 220v plug for EVs, but I'm not sure whether he did. If so, we could in theory drive up in something with 200 miles of range, charge while we're there, then drive back. But in reality we'll just take our gas car because it's less of a headache.