Battery-Electric Fast-Charging Versus Time Explained

FEB 7 2019 BY DAVID ROPER 66

If BEV charging really an issue?

One often reads statements by ICE drivers that they will not buy a BEV until it can be charged as fast as ICE cars can be filled with gasoline; they often state a 5-minutes target fill time. I do not recall ever spending only 5 minutes at a gasoline station. I estimate 15 minutes as the minimum time I used to be at a gasoline station, and it was usually longer. I stop my Tesla Model 3 Long Range on long trips for personal reasons more often than needed to charge car. Tesla navigation on the screen tells me how long to charge at each Supercharger to minimize travel time; I often charge longer than that for personal reasons.

It is a fact that fast-charging (kW) a BEV battery is not at a constant speed as is the case for filling an ICE gasoline tank. In this document I examine the filling rate for fast charging of a BEV.

Consider three BEVS with maximum charge rate of 120 kW, 250 kW and 350 kW with batteries of the same battery chemistry and, therefore the same shape of the charging-power curve. If the 120-kW BEV is the Tesla Model 3 Long Range BEV (TM3LR) with about 75-kWh usable battery capacity, the power-proportional usable battery capacities for the other two cars would be about 155 kWh and 220 kWh. (I use 250 kW power because Tesla has indicated that will be the maximum power for near-future Superchargers. I use 350 kW because Electrify America is starting to install some stations with that maximum power.)

Using the mathematical formula for charging power in my previous study for charging the TM3LR using a Tesla Supercharger and TM3LR charging-power data I get the following approximate charging curves for the three BEVs:

The two higher kWh BEVs probably would not have as high efficiency as the 75-kWh BEV. The batteries would weigh more and the cars would be larger.Assume the following realistic efficiencies:

  • BEV kWh 75 155 220
  • Miles/kWh 4 3 2.5

The corresponding three curves for miles gained versus charging time using a Supercharger are:

The vertical line is about the half-way the time to full.

Note that a 75-kWh BEV with 4 miles/kWh efficiency would get about 150 miles added in twenty minutes. As the three curves show, when driving a BEV on a long trip it is not wise to fill the battery to near full; that should be done overnight at home or a hotel. Of course, the level-2 charging stations power at those locations will range from 6 kW to 19 kW, which have much longer level power curves, but the curves do tail off before reaching full. A constant 10 kW would take about 7.5 hours to fill the 75-kWh battery from empty to full, about 15.5 hours to fill the 155-kWh battery from empty to full and about 22 hours to fill the 220-kwh battery from empty to full.

It is not wise to charge from a high state of charge (SOC) to near full on a long trip because the average charging power is much lower than when starting at a low SOC. Here is such a Supercharging curve for the TM3LR starting charging at 68% SOC:

In the future, there may be new battery chemistry that possibly include super-capacitors for BEVs that charge much faster or without tailing off as quickly as shown below:

Categories: Battery Tech, Charging, EV Education

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66 Comments on "Battery-Electric Fast-Charging Versus Time Explained"

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Thank you for this article. I sure wish the industry would standardize and rate DCQC charging times more realistically, for example, from, say, 20% to 80%. On a long BEV trip, one would rarely want to dip below about 15% and certainly would rarely want to hang around above about 75% unless really needed to reach the next charging station. In my case with a Tesla S85 used only for long trips, after three years I have yet to fully charge it and the only time I even approach 85% during a trip is when we’ve stopped for lunch.

“…they often state a 5-minutes target fill time”

1. It generally takes less than 5 minutes given the trend to have small fuel tanks in ICE vehicle these days (in the US). My Honda HRV’s tank is 13+ gallons, down from 18+ gallons in my previous Camry. As MPG has gone up, I do see why ICE manufacturers started using smaller fuel tanks.

2. I fuel up when the station is not busy so I do plan when to fuel up. That 5-minute timeframe is both fair and accurate in my case.

I was looking to buy the Subaru Hatchback when the new model came out and it had 13.2 gallons for the fuel tank, which was down from 14.5 gallons in the previous model. A reduction of 1.3 gallons may not be much, but it reduces fueling times.

As gas engines get more fuel efficient, I expect to see even smaller fuel tanks as the standard.

Lastly, I was looking at the Toyota RAV4 (and Hybrid), and it only has a 14.5 gallon fuel tank, down from 15.9 gallons, respectively.

I agree that 5 minutes is plenty doable in a car. When I’m on my bike I don’t even get off, just get close enough to grab the nozzle and reach the credit card slot; 2 minutes max.

You’re missing the point. While it’s possible to refuel a small car in 5 minutes, longer times are more common. This is especially true for motorists looking for cheaper gas. There are always long waits at Costco gas (often 30 minutes) to save a few % off the station down the block. Besides, most of my charging takes 5 seconds to plug in, and costs a tiny fraction of gas.

The real point is that filling up is much easier and faster than charging an EV. So the whole argument of gas stations needs to be dropped because it is not possible to take EV advocates seriously when they bring up something that is so obviously wrong.

I’ve spent more time looking for a single charging station that I’ve done filling up a years worth of fuel. Even charging at home is a lot more work and takes more time than filling up a gas car.

There are hundreds of reason why an EV is better, but time and effort of charging vs. filling up is definitely not one of them.

“Even charging at home is a lot more work and takes more time than filling up a gas car.”

You lost me on that one. I plug my Model 3 in maybe twice a week at most. It takes 10 seconds from stepping out of the car until it’s plugged in and I’m walking inside. So 20 seconds a week to stay charged up in my garage.

exactly – wtf –

“Even charging at home is a lot more work and takes more time than filling up a gas car.”

Either you don’t actually own an EV or you have some type of Rube Goldberg arrangement to charge your car at home. How else can you possibly compare the time it takes to pull your cable off the charger and plug it into your EV to filling up at a gas station? It takes 15 seconds to plug in MY car (30 if my daughter hung up the cord). It takes you at least a minute just to drive into the gas station, let alone put the filler into your tank and pay three times as much with your charge card, unless you pay in cash and then it’s an even more ridiculous comparison.

Oh, and instead of “looking for a charging station,” try using PlugShare and get the directions.

You offer an absurd statement comparing a gas station to home charging. Take that seriously.

I think charging at home it’s much more convenient than fueling a car.
Having said that, where I live there are plenty of stations where someone do all the work.

What a load of rubbish! It takes 5 seconds to plug in at home. 95% of the time for 95% of people that will be enough. So most people will save a lot of time overall not driving an ice car. Only if you go on frequent long drives will charging bite into your time, in that case maybe electric is not the right choice.
But for by far the majority of people, with EV’s that can charge at home or at work, will save a lot of time and hassle at stinky fuel stations.

That really depends. I come home, plug I the car in a few seconds. And even that is something I do not do every day because on a normal day I maybe use 20% of the charge. So I can do a few days without charging. My Ford Focus diesel, costs me around 7 minutes to fuel up. Parking, getting out, paying etc.

There are plenty of chargers already, but most of the time they are “invisible”. That’s why Fastned in Europe uses bright yellow colours and almost landmark kind of visible things. Because you see them from afar on the highway stations. They are installing 175kWh chargers right now and that is a huge difference in charging speed when cars are going to use that.
So yes a car takes longer to charge but you can charge almost everywhere nowadays. And you can’t fill up a ICE car at home. We can’t install a charger but I bought a cable long enough for outside so even when it’s raining I can charge our little Zoe.

Now we know, that you do not charge at home, otherwise your opinion about home charging could not be further from the truth. Or you simply don’t understand the difference, which is puzzling, indeed.

“You’re missing the point…” I studied production management during my MBA studies and the author of this article is confusing fueling times with set-up time with other issues. That is no different than set-up time, wait-time, etc, for an EV. You need to make an apples to apples comparison and the author failed miserably at that. The difference between us is I caught the author’s mistake and you did not. Btw, I buy my gas at Costco and I don’t but gas when the lines are crazy. Believe it or not, people plan to when to buy gas (at off peak hours) which is no different than an EV owner who has to plan when to charge up. Again, you need to make an apples to apples comparison. One more thing, I live near Davis, CA that offers free EV charging (at a 4-hr limit) in public places and these chargers are almost always being used. Good luck finding a free charger for your EV during peak hours. The point is: IT DOES NOT MATTER if you own an ICE or EV when the respective fueling station is busy — refueling times are going to be long!!

The main reason for smaller fuel tanks is packaging.

A fuel tank can’t be put anywhere, since it needs extras crash protection. So every liter saved gives more flexibility to the engineers. That leads to a bigger trunk, interior volume, or weight savings due to less strengthening because of larger crumple zones.

The reason why they aren’t super small, is that people expect a certain driving range from their car. But if the car gets more efficient, a smaller tank gives the same range.

My last ICE was a diesel with a massive fuel tank. It took long to fill up, but it could also easily go over 500 miles in any circumstance. I personally liked that, because it meant less visits to the gas station.

The article is interesting, but I can refuel a car in less than 5 minutes if there’s no waiting line, if I use automatic payment less than that.
I was accused of spreading FUD about EVs (people with a high level of ignorance) but hiding the problems of EVs makes no sense – no EVs don’t charge as close as fast as ICE cars. In 5 minutes an ICE car is good for more 500 miles a Diesel car 800 miles.
Obviously many recharge EVs at home and time waiting for charging the car is irrelevant.

“Obviously many recharge EVs at home…”
Duh!
The 5 minutes you spend at the gas station (if you are super fast) are 5 minutes more than what i spend at the gas station.

Exactly and at as much as 1/10th the cost per mile compared to fossil fuels and infinitely more sustainable. In my case I charge off of my roof panels in my garage. So I run the car with sunlight ….Our power company in the Pacific NW is mostly renewable energy and even if your region used coal to generate electricity, there are economies of scale. Trolls like Alex never acknowledge that fossil fuels are the primary cause of climate change and apparently don’t give a crap to save a few minutes at the pump. I haven’t fueled at a pump for years. When I travel I use a supercharger for free and grab a snack and then go on my way.

Do you want to explain your math for 1/10 of the cost? (I’m from Europe where gas is very expensive, so use European gas prices at will).
I’m asking this sincerely, I’m curious.

So in many regions in the NW US, electricity is about 14 cents a KW. https://www.electricchoice.com/electricity-prices-by-state/ Gas in many areas averages 3.00 per gallon: https://gasprices.aaa.com/state-gas-price-averages/ Most EVs average about 300 watts to travel 1 mile. Lets use 21 MPG as a base. At 3.00 per gallon that is approximately .14 cents per mile (300/21) In terms of watts @ 14 cents per KW is .00014 cents per watt x 300 watts per mile (the number of watts it takes to travel one mile in an EV) = .042 cents per mile So in our region the cost per mile comparison is .042/.140 = .3 times or a little less than one third the cost of propelling a vehicle with electricity vs gasoline at current prices. Gas prices are artificially low right now. These ratios will change depending on the cost of electricity and gas. I have solar power on my roof so it is a much lower cost for electricity and most people here drive large SUVs which get even lower mileage so it gets closer to that 1/10th the cost of fuel. On the average I would say it is 1/3 to 1/4 the cost of fuel to drive… Read more »
Why not use average electricity prices, or even better weight EVs sales to get that average price, per example California where there are more EVs would get more weight. So the original 1/10 was reduced to less than half, maybe 1/3 – let’s talk about trolls that spread FUD. Are you trying to compare a big truck with a different size EV? Let me help you, use a semi truck full loaded, it will help your cause. Are you sure the average fuel price is that, I counted 3 states with fuel price above $2.5/gallon (fast look at AAA site). 21 MPG seems a reasonable value, but there are cars (probably more models than all the EVs) that do at least twice as better. Now in those few occasions where super chargers are used, charging becomes a lot more expensive. In the cold consumption grow a lot more with EVs. Also a model 3 just parked uses $5/month (if it’s not too cold) – it’s in another recent article here. But I don’t doubt fueling/charging is cheaper for EVs. But now let’s account for acquisition costs and interests (most people borrow money to get a car). A leaf (a very… Read more »

21MPG?!? I have never owned a car that got anywhere near that low. You have to go to a fairly large SUV to get that, and now you are no longer comparing apples to apples. A comparable car to a Leaf should get at least 30-35MPG.

Agreed – I was pointing out the numbers using those for SUVs and trucks which are the best selling and most fuel intensive vehicles in the US. I agree I mis-stated that electric propulsion was one 10th of ICE – I apologize –
However, I don’t think anyone can dispute with some rough calculations with equivalent vehicles that running cars will electricity is at least half of the cost of ICE. Most Evs get around 120 MPGE – not many cars get 60MPG or close to that unless they are plug in hybrids do you think?

I can go 1000km a day without stopping in a place I don’t want.
For small to medium trips if one has easy access to a charger, EVs are indeed more convenient.
In Europe about 60% of the people live in non detached houses and most of them park on the street.

so how often do you travel 1000 km a day? If that is your routine, yeah it won’t work for you very well. If you care about your carbon footprint maybe you should get a job that doesn’t require you to drive over 1000 km a day. You are selfish and irresponsible if that is your transportation pattern. I can’t say I personally know anyone that travels that much regularly – its not much of a life. You are correct in that adaptation of EVs from people that park on the street is a major obstacle. In our region however there are thousands of chargers in the metro area so it isn’t a problem. I say if you have to park on the street, the odds are that you have access to public transit and shouldn’t be driving a car anyway.

Yes I drive 1000km a day. Do you want to tell me how I should live my life?
😉

So the ones parking on the street shouldn’t have the right to own a car?!
Do you realize how insane and offensive for millions of people is what you say?!

I don’t believe that you drive 1000 km or 621 miles a day unless you are a long haul trucker. Parking is clogging up our cities. Areas of density favor public transportation – look at Paris, New York, London, San Francisco. – people who have to park on the street in dense public cities should consider other options it would be insane not to.

Why don’t you believe? Do you know me?

@SansIce It’s a bit arrogant of you to pontificate that people who live in densely populated areas with access to public transit “shouldn’t be driving a car anyways.” Did you ever try doing a Costco or supermarket run using public transit? How are going to bring all the stuff you bought on to public transit? Did you have an infinite amount of time each day to for the extra time to get to various destinations? It could take hours longer to run errands using public transit, as opposed to driving. Getting between two points like the gym and the dry cleaners via public transit could take you on a roundabout route that might require transfers/changing-lines, making the trip very time consuming as opposed to driving straight there. Then there is the cost of public transit. On the weekend, if I want to take my family of four to the ocean beach in the suburbs or shopping to the upscale Mall in the suburbs (both about 25 miles away) I’d have to take commuter rail and then a bus. That would cost me about $100 each way, not to mention extrateavel time. Instead of paying $200 for a round trip on… Read more »

Public transit in Seattle is cheap.plentiful and safe. How do you fit your large family and all of your Costco purchases in an Apartment? I believe you live in a house and that you could charge in your garage if you wanted to. Why are you anti EV guys trolling this discussion group?

70 Percent of the population in the us lives in houses – 88 percent own cars- so the number in dispute is the 18 percent of the people that own cars and live in apartments? If we could get the 70 percent of people that own cars to drive electric- that would be the goal.
https://www.builderonline.com/money/economics/80-percent-of-americans-prefer-single-family-homeownership_o

So the World that matters is the US… only the ones that live in detached houses!

If any of us is anti-EVs, that I’m not, you seem to be anti 6.5 billion people — conservative!
Wow!

Really you are not helping yourself in this discussion.
I’m always happy to have a discussion using elevated arguments and I’m good at it, so if you really want to do this in a polite and educated manner without silly accusations you better be prepared or you’ll make it silly for your cause.

EVs are so much better in so many aspects, and you decided to chose all the wrong ones!

This is primarily a US page although it is great to hear from people from other countries. So the crux of your is that the adaptation of EVs is difficult because not everyone lives in detached houses and can charge at home. Fine, we are all in agreement with that point. I say that in areas where there is sufficient density maybe we should look at limiting cars altogether- I didn’t invent this idea and it is being implemented. The discussion thread is about charging times and availability. In the US most people live in houses and can charge at home- that is a fact. Electricity is cheaper than gas to run vehicles in all countries-fact. More telling is how you let it slip that you are anti- EV and trolling our page- please leave us alone or st least stop saying “silly” so much – lol.

It doesn’t matter how hard people try to have a coherent honest discussion with you, you always turn it into ax grinding you so desperately need every day, I guess.

Go enjoy 1000km drive days you drive often with zero break, I am sure. Just buy TDI since you live in Europe without access to a plug at home. Obviously, EV is not for you. Why to waste time posting here and looking silly several times a day. Life is short …

Are you still talking about EVs?
It wasn’t me starting with 1/10th and ended up with 1/3rd a few posts later – is that coherent to you?

Come on, you just don’t have arguments for me, because I’m right. Simply as that.

That is why I am highly suspicious of Alex; the syntax, the relentless bashing and trolling. Alex could be getting paid by the post. It wouldn’t be the first time a discussion group has been hacked and trolled by someone with opposing interests. There are a lot of people that have a lot to lose financially with the green and EV revolution including the Russians and our President. I wouldn’t be surprised if Alex is part of that resistance movement and is getting paid to disrupt our site – Alex doth protesteth too much!

WTF! Are you saying that all pilots must give up their jobs because their work requires them to dump tonnes of carbon into the atmosphere. It’s no wonder the greenies are fighting an uphill battle when they are represented with the likes like this.

I am saying that if you truly believe that our individual behavior is affecting the health of the planet adversely, then one needs to look at ones life holistically and make changes for the betterment of society as a whole. Personally, I drive 2 EVs powered by panels on my roof and have changed my job to work locally after travelling over 75,000 miles a year by plane. Those are the changes I have consciously made to reduce my carbon footprint.If you don’t think your behavior is important to move towards a more sustainable green society then so be it. A lot of us are walking the talk with our actions. Change is not easy but necessary. What are the decisions you have made to make a difference for the better or do you not give a crap?

And the trolling continues…..

Let’s try to stop it right here.
What’s your position on charging vs fueling cars?
😉

Simple -charging is easy and fast enough, fueling cars with gasoline causes cancer, kills the planet, is expensive, dirty and unsustainable.

end should say “and faster but not worth the speed gained.”

Just depends on travel habits. Gas car or EV I’m forced to stop every 2 1/2-3 hours anyway because somebody has to go to the bathroom. So in our Model 3 we just stop at a Supercharger rather than a gas station and charge for 20 minutes. I’ve found that if plugging in at a fairly low state of charge in 20-25 minutes you have enough to go another 2-2 1/2 hours.

So it’s a little slower than gas but unless you are attempting a NASCAR pitstop, yelling at your family to hurry up it’s going to take 10-15 minutes anyway. So at worst you are maybe losing 10 minutes per stop. 3 stops on a 500 mile 6 1/2 hour trip means a 7 hour trip instead. Not a big deal.

Then the rest of the year charging at home is much faster than filling up.

It’s not a little slower.
The guy from YouTube channel “e for electric” owned a model S, and he used to rent an ice car every time he needed to do a longer commute – just because it was simply more convenient.
This was an EV fan owning one of the most expensive and biggest range EVs.

If all people start to suffer from cognitive dissonance believing that charging speed and range is not an issue we better stop improving batteries.

How can someone spend 15 minutes at a gas station? You drive in, swipe your card, fill it up in 3 minutes and go. 5 minutes maximum….

who cares – that isn’t the reason most of us drive EVs. The earth is dying because of you – wake up.

I spend maybe 20 seconds a week “filling up” in my garage.

EVs are a perfect fit for about 5 to 10% of persons – so you belong there, perfectly fine thanks for sharing your personal case.

Nice try Alexandra the Russian troll. Your numbers are way off. Most people travel less than 100 miles to work – most modern EVs easily have that range.

https://www.washingtonpost.com/news/wonk/wp/2016/02/25/how-much-of-your-life-youre-wasting-on-your-commute/?noredirect=on&utm_term=.9bcbf60e3acb

There you are, you lost arguments make silly accusations based on ignorance.
But let me ask you, what’s the share of sales of EVs worldwide?

Increasing by great numbers every year dispute your wishes. For instance the Model 3 being the top selling luxury sedan in the us regardless of its electric drive train- that must make you angry.

I said “are a perfect fit” I didn’t wrote “will be a perfect fit in 10 years”.
I’m not angry, I play with EVs even before Tesla was a dream, I converted a motorcycle when I as 16.
Electric vehicles are better in every way except battery energy density and cost of it.

Model 3 is not the top selling luxury car, it’s not even a luxury car, only the price is luxury because batteries cost a lot of money…. yet. You seem to forget easily you are not alone in this World.

Stop killing the Earth dude…

You think it is funny – most of us here don’t – you are killing the planet – lady – wake the f up. Internal combustion engines are the main cause of global warming:

https://education.seattlepi.com/release-car-exhaust-fumes-cause-global-warming-3682.html

I don’t think it’s funny. It wasn’t me that voted for Trump, he’s the one that likes to make jokes about climate changes.

Maybe not but your Russian friends swung our election in his favor

I have nothing against the Russians, do you?
Do you think we should judge people based on nationality?

The Russians tried ( perhaps successfully) to affect our democratic process for the financial gain of their oligarchs and our corrupt President – is that something the people in the US should be happy about?

I don’t know. Every time I go to Costco I chuckle at the line of lemmings waiting 15 to 20 minutes to save a $1.

How does this work? Are people buying some sort of liquid fuel at these places?

There is a cancer warning on the posts so I avoid them and charge at home.

Why didn’t you do a comparison of the model3 v the Etron or, something useful like that?
The Etron can charge faster at kwh per hour but, it doesn’t charge faster in terms of range per hour because it is so inefficient.

What would be useful is a charging range per hour graph of all the competing models. Atm the moment, companies like VW can hide behind a nominally higher charging rate when in fact it is slower on what matters – range/min. I acknowledge that VW duping the public is par for the course.

15min at a gas station? Maybe in the States but here in the third world I fill 80litres diesel in about 5-7 minutes in and out. If the petrol attendants are busy with lots of cars it may get to 10 and 15 on a extremely bad day. Yes, we use petrol attendants for employment creation – not allowed to fill own car here. The haters have a great point and until we stop burying our heads in the sand with inapropriate arguments like: -more than 15minute gas fills (try half that) -in cold weather gas cars also suffer from range loss too (agreed, but not 30% and refils take 5 minutes, and your base range is 600-800km at least) -you need to stop more often than your car (agreed, unless you driver swap while refueling, or your destination has not electricity, or there are no chargers on your route, or there is no electricity on your route!, or what if you are towing a trailer/caravan etc) -cheaper long term cost of ownership (few people think long term with car costs. Upfront is what is in their minds – live in the now mentality and they only keep cars for… Read more »

I want to ask people, you say it takes 5 min to fill up your car? Do you have a gas station at home? or do you have to drive to one first?
Once you realize you need gas, you first have to find a gas station, that will take more than 5 min with fueling.
Is it not worth your while to charge a car at home, then when doing a long trip wait for it to charge? How much time and money have you saved by not going to a gas station during the year?
Statistics show that on average Americans drive 29 Miles a day.

+1

I absolutely hate when I need to put gas in my Volt! Do estimate electric is 3 to 4 times cheaper than gas for me, but even if reversed I would pay the higher price to drive electric – assuming I can afford. It is a choice, and if money allows I will clearly make my next car a BEV, end of lease or sooner, don’t care about little inconveniences. Will make it work.

That is what I came to above – it seems like driving electric averages 1/3 to 1/4 the cost of ICE on average . That doesn’t include oil and brakes though which drives the cost of driving EVs even lower.