Study: EV Range Drops by 25% Due to “Psychological Safety Buffer”


EV Range Graphic

EV Range Graphic

A doctoral candidate at Technische Universität Chemnitz in Germany concludes that 20% to 25% of the range of an electric vehicle is actually lost in the real world due to what he calls a psychological safety buffer.

BMW i3 Range Sign - It's No Longer Expected That the i3 Will Deliver Even Close to 100 Miles Per Charge in EPA Tests

BMW i3 Range Sign – It’s No Longer Expected That the i3 Will Deliver Even Close to 100 Miles Per Charge in EPA Tests

Of course, this isn’t always true, as there are countless EV drivers who routinely run their rides down to less than 5% charge or even lower, but the general finding is that most driver’s aren’t willing to push an EV to near its range limit.

A study was conducted around 79 Mini E drivers who logged more than 249,000 miles over the course of 6 months.

Thomas Franke, the man who put forth the “psychological safety buffer” conclusion writes:

“In sum, the suboptimal range utilization found in previous studies is explained by the proposition that there are three psychological range levels besides the technical range that characterize the transition from the objective physical to the subjective psychological range situation: (1) The competent (i.e., maximum achievable for the user), (2) the performant (i.e., available on an everyday basis) and (3) the comfortable (i.e., actual usable) range. It shows that 20-25% of the range resources that are available on an everyday basis are lost as a psychological safety buffer.”

Mini E - A Pure Electric Relic of the Past

Mini E – A Pure Electric Relic of the Past

“[The results imply] that the primary objective of vehicle development should not be to increase battery capacity but to increase the comfortable usable range for the driver. If you consider how much increasing the technical range of electric vehicles by 20 percent costs today, it is very promising if one could achieve such an increase potentially also through optimized information and assistant systems.”

Like by including an accurate state of charge meter, perhaps?

For a more detailed analysis of the study, follow the source link below.

Source: Green Car Congress

Categories: General

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38 Comments on "Study: EV Range Drops by 25% Due to “Psychological Safety Buffer”"

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This is interesting but we are all familiar with the same effect in ICEs. Very few people drive to where the gas gauge reads E. No one wants to be stranded so we all maintain a buffer. With spotty availability of EVSEs, EV owners are right to be a bit more conservative than their ICE brethren.

Personally, I get very nervous when my remaining range is below around 20%. A road closure or small emergency could become a huge problem.

Finally, to say that we can get more range by driving it to zero is kind of ridiculous. Running out of charge means a tow/flatbed. Running out of gas means you go get a gas can. Very different time and costs associated with each.

> Running out of charge means a tow/flatbed.

Only if you’re silly enough to keep driving, continuously ignoring all the urgent chiming and dashboard warning messages.

The EV equivalent to a gas can is pulling into a commercial or residential driveway, pulling out your 120v charge cord, and humbly asking your neighbor for 25 cents worth of electricity, which you’ll gladly pay $1, or $5 or whatever for.

If you’re a little more savvy, you’ve got PlugShare loaded in your smart phone and you go to someone’s house or business who not only gives you the charge, at 240v for free, but offers you a cup of tea, a crumpet, and a sympathetic ear. May or may not be your new BFF, but hey, people have gotten married beginning with less formal introductions.

There’s also AAA, who has a new sunshine yellow Level 2 and CHAdeMO rescue truck patrolling the freeways of the SF Bay area. (more to follow, not doubt, they are big into batteries these days)

If you really have to call a flat bed, you are paying the stupidity tax.

At least Nissan is offering free towing AFAIK. It’s not the $$ cost but the inconvenience and time lost.

The way to avoid the “stupidity tax” is precisely what the study finds: keep a buffer unless you *know* you are, e.g., heading back into the stable with just enough range.

That doesn’t change what goes through people’s minds when they get low. The psychological effect is real. And plug share is fine but there are lots of charging deserts in the US.

The correct answer is to build cars with more range. I would never own a BEV that has less than 200 miles of range.

It boils down to knowing the car a little. You don’t just “run out of charge”, like by accident. With just a little bit of experience, range, and especially how, it can stretch dramatically with less aggressive driving (unlike an ICE), are very predictable.

My two rules of thumb with the Leaf:

* If I think I’m not going to make it, e.g. the Guess-O-Meter indicates less miles left than the remaining distance I’ve to cover — don’t worry one bit and keep going.

* If I know FOR SURE I’m not going to make it, e.g. the guess-o-meter indicates 4 miles left and I’ve another 12 to go — just slow down.

Of course, I understand that this would be a little unsettling to newbies — it’s not something that I’d have done during my first week with an EV either. But I now know this works beautifully.

With experience comes confidence, and with it serenity.

I know of people who drive their gas guzzler exclusively on empty often with the light on and refuse to put in more than $5 of gas. Completely irrationally those same people are too anxious to get an EV.

Maybe they would be more comfortable with an EV, since it would alway report less than 75 miles left of range. It’s all about staying in your comfort zone…

“running out of gas means a gas can”

No, it means you compare apples and apples and oranges and oranges. In an EV world, the tow truck can charge you, and in 5 minutes give you enough charge to get to a station. This is as good or better than the AAA driver with a can of gas.

Manufacturers don’t help by underestimating range when SOC% is low.

For example,in a LEAF having two remaining charge bars out of 12 makes most people think they’re at 1/6 capacity or less, when they typically have 20-30%SOC left.

Umm.. welcome to 1996. It’s called range anxiety.

Also, using a percentage like 25% isn’t a good idea since some BEVs have 50 mile ranges while others have 300 mile ranges. It would have been better to say that they don’t allow their range to go below X miles.

I questioned that too, but then I realize that many Model S owners start getting nervous below 60 miles remaining.

I laugh because I start out each day with only about 60 miles range remaining in the LEAF! (80% charge, down almost 20% capacity from new).

I think a lot of the anxiety around EV range is tied to the detail provided about range.

Unlike ICE vehicles where most just have a gauge where at 1/4 or 1/8 full most have no clue how many miles they have left, but just know they need to get gas. But with an EV, you know it’s 23 miles for example.

Where no matter if you drive and EV or ICE vehicle, at 1/2 full most will ‘plan’ to find a plug or gas station and fill up.

Which is why it makes sense to only lease/buy an EV with twice your daily commute range at minimum.

I have taken my i-MiEV to one bar remaining (out of 16) only twice. Once on an emergency trip that was just outside the range of the car (had to charge a bit at midpoint) and once when I was recalibrating the guess-o-meter.

Otherwise, I rarely if ever hit 2 bars. Usually it’s in the spring/fall when I don’t have to use any heater or A/C and I’ll go 3 or even 4 days without charging, just because I can. 🙂

LOL scion iq is lame

It took a doctoral candidate to come up with this information? I said the same thing a year or two ago, explaining why Volt drivers get more EV range in practice than Leaf drivers, despite the smaller battery pack.

And you’d be completely and utterly wrong.

The Leaf has over twice the electric range than the Volt, so for your assumption to be true, people would have to stop driving their EV when the battery reaches 50% SoC.

Not very plausible is it?

The reason why PHVs drivers travel a lot of miles on electricity is simply because they drive more.
It’s a kind of preselection bias: people who drive a lot will naturally tend to prefer hybrids (plug-in or not) over EVs.

Different needs, different vehicles. How hard is this to grasp?

Being able to “drive more” also means more opportunity charging and thus more EV miles.

If PHEV’s do allow you to “drive more” then that is an advantage over lower-range BEVs. A less compromised vehicle.

I keep wondering why many Volt owners (unlike other hybrids, amazingly) feel the urge to diss disparaging remarks at EVs whenever they get the chance. Sorry guys but it makes no sense IMHO.

Anyway, you surely bought yours knowing full well about its seating and cargo capacity, and those have probably never been an issue: the car does all you wanted and more, and you’re totally happy with it.
Would you now say your vehicle is “compromised” because you can’t move e.g. a piano with it?

Unless you needed to transport large objects on a regular basis, that artificial requirement would be completely pointless in your situation, wouldn’t it?

If you ever had to move big things, you’d just borrow or rent a truck, or even have someone else take care of it (trivial expense compared to the gas you already saved I’m sure). Not drive some much-larger-than-necessary vehicle every day, “just in case”… right?

It’s compromised regarding the topic at hand. You’re the one who said it, not me.

If we were talking about hauling pianos, I’d say most/all compacts & subcompacts are compromised.

The biggest difference in comparing to an ICE car is the frequency of the anxiety and effort to resolve it. If someone (foolishly IMO) buy an EV with a daily driving pattern right on the edge of their range, well, RA will be their best friend and they experience it EVERY day. With an ICE car, that doesn’t roll around nearly as often (OK, OK, as a teenager I was routinely driving around on “E” – LOL) and if it does, you are often a few blocks from a “full tank”. It all boild down to how big your buffer is for YOUR driving pattern (and a big *ss battery – a la Tesla – goes a long way toward addressing that).

This study has been reported multiple times on other sites. The most logical comment I’ve seen is that the buffer is not a percentage of total range, but rather a fixed distance cushion. I’ve seen people state 10-20 miles is their routine cushion. I concur, but it always depends on where you’re driving and how many public charging stations are around near the end of the trip. If there are public stations available in the last 10-20 miles of the trip, I just don’t worry about it.

This is why we need EVs with a 125 mile range. 100 miles covers most people’s needs and the extra 25 gives people that buffer range for security.

Personally I need 200 min, but i’d prefer 265, or whatever I’d get in a Model S w/my driving style/destinations.

Who made that graphic at the top of the story? That’s not even the right RAV4 body for the EV. It’s the body of the 2013 & 2014 ICE RAV4.

It’s just a mindset. I drive regularly to Orange County and back to San Diego. I’ve gotten 0 bars plenty of times and have yet to run out. It is just based on experience and driving technique when you know you need the range. I’m also the type of person to not fill up the gas tank until it lights up on E.

Want to drastically increase EV range on the freeway? Follow a semi-truck. I followed a semi from a comfortable distance travelling 62 mph in my Prius the other day along a long straight and level stretch of I-5. The Prius reported ~45 MPG when not behind the truck then shot up to ~75 when behind it. You can really feel the difference if you put your hand out the window. I told my wife if she’s ever concerned about reaching a destination in her LEAF, pull in behind a semi.

Haha… I do this too. It works! Thanks, semi, for pushing the air out of my way! Honk honk!

Gosh, that number is so right. Same feeling here.

But for me it’s not just the fear of being stranded, I also don’t want to cycle my battery to deep, because discharge close to 0% on regular bases will speed up degradation even more than filling to 100%.

So there realy is a benefit in not/seldom using the last quarter. Not much need for improved “use advisor tec” imho.

I think they need to build in reserve in their calculators for this 25%.
In my gas car, I know when the light comes on, I have at least 50km left.
If I have that same kind of buffer in an ev, its not as big a deal.
I.e. when it hits ‘0’, I really have 10k to get to the nearest charger.

Better yet, this is all computer driven – let us pick the ‘E’ threshold. Those who like to play it safe, larger buffer. Those who want a little risk, zero buffer.

With all the whiz-bang moving maps and navigation software available today, which will tell you to within a tenth of a mile how far your next trip leg is, it’s pretty silly to truly run out of range enroute. Start each day with a full charge and you’ll very rarely be anywhere close to empty.

For those rare days where you really are running all over town, there’s a simple solution: charge early and charge often. How many times do you really drive all over the place and not stop for 30 mins to an hour?

Be vocal with the places you do business with that one of your selection criterion is whether they support clean air, etc. by providing charging infrastructure. Most businesses, if they hear that a few times, will start thinking about how to serve you and keep your business. If its a small shopowner in a strip mall, they’ll start talking to the property manager.

It won’t happen overnight, but if every shopkeeper starts hearing they should have at least an outlet avail in the parking lot, range anxiety will be something we tell out grand kids about to make them giggle.

Hmm… I guess “range anxiety” is alive and well…

In the minds of people not actually driving EVs, yes, sadly that myth continues unabated.

In the first sentence quoted from the article linked above (which you didn’t bother to read before jumping to conclusions):
“users with practical electric vehicle experience rarely experience situations in which range anxiety occurs”

Another study in the US came to the same conclusion:
“[EV drivers] indicate that any possible “range anxiety” they experienced before buying one has been eliminated over time”

( page 4)

Well, most LEAF owners already did a “range anxiety” removal by removing the need of their “daily driving range” like you said.

That is why “average LEAF owners” average less EV miles than Volt owners.

But the fact is that until we have enough range AND charging network available, the range anxiety is there, especially during winter.

You are right, the self selection bias is there. That is why my coworkers with 80 miles commute isn’t buying the LEAF. But those people with long range commute are the BIGGEST benefactor if they convert to the plugin cars.

A LEAF going 30 miles per day is only 10K miles per year to about 7,800 miles for commuting. In that sense, it is below the typical 12K miles for most car leases…

Here is the info from you study:

An SCE study of 92 Nissan LEAF owners shows:
• Average daily miles driven: 35.
• Driven more during the weekdays.
• On average charged only once a day, at home and overnight.
• The type of trips taken in the LEAF weekly did not differ from those taken in other household vehicles (except long road trips).

Nuff said there….

Also, your link was on “early adopter” as stated in: “Initial Findings Show Early Adopters of BEV Technology Demonstrate Consistent and Predictable Behavior”

As a group, the early adopter are generally different from mass market.

Folks with this ‘buffer’ issue should drive hybrids or bring a shrink along with them!

Well, send me the shrink please! I have been driving my Leaf for 7 months / 7500 miles now in Minnesota, not too many L2 public chargers here yet.

I get uncomfortable when I drop below 20% charge and am more than 10 miles from home still. I did a road trip in my Leaf last weekend a total of 176 miles in 1 day on nothing but L2 chargers (we don’t have a single Chademo charger in Minnesota yet). On the final stretch coming home I pulled into the garage with 7% charge remaining – the lowest I have ever taken it. If I had 5 more miles to drive, I would have honestly been searching for the nearest 110 outlet. Beyond Minneapolis and Saint Paul, L2 chargers are a very rare find here, and I have more often than not received push back when contacting stores/employers about installing charging stations. 🙁

Lol,’I can’t send you a shrink Tim, but I can send you some copies of Electric Car Insider magazine, which you can give to those employers and shop keepers when you suggest that they consider installing charge stations.

Our upcoming issue makes a pretty good business case for installing workplace and retail EVSE.

Just send me an email, my contact info is on the web site.