Op-Ed: Musing “3rd” Generation EVs And Range

APR 11 2014 BY SCOTT FRANCO 88

Tesla Has Promised A $35,000 (ish), 200 Mile EV In 2017

Tesla Has Promised A $35,000 (ish), 200 Mile EV In 2017

The current situation

If you believe the press, by 2015 to 2017 we will see 150-200 mile range cars in the $25,000 to $35,000 price bracket. What would it mean to have cars with that range? The Tesla series cars are certainly a preview of it. A Tesla S model (85 kWh version) at 300 miles range (according to Tesla motors). This is similar to the average range of a gasoline car. I’m sure that it was not an accident that Tesla picked this range. Aside from the pesky charging issue, this makes the Model S a reasonable competitor for gas driven cars.

A 48 kWh "Mobile Test Lab" Nissan LEAF Ran This Year At ECOseries

A 48 kWh “Mobile Test Lab” Nissan LEAF Ran This Year At ECOseries

The Tesla model S is not immune from range issues. My co-workers (read: managers) with Teslas usually have to put up with a level 2 charger at work. That means about 20 miles per hour of charge, or 12 hours to reach a 80% charge. At 120 kW (the Tesla maximum supercharger rate), and 396 W per mile, that means 42 minutes to reach an 80% charge at the highest available Tesla supercharger.

The reason I mention this is because, with the expected 150 mile range Leaf and the 200 mile range Tesla model E, the charge times of the next generation leaf go up, and the charge times of the Tesla go down, both relative to the current generation cars. That is, if the same chargers are used. This is why you have to consider both the car and what is charging it.

Let’s start with an across the board way to measure charging, and the resultant mileage from the car. As often stated, charge times are linear up to 80%, then curve up after that. For example,  it takes more time after 80% to get the same amount of mileage. So I will use “watt/hours per mile (KWH/mile). This is not the same thing as the power efficiency, or how many watt/hours the car expends to push itself one mile. Instead, it is the total cost, in watts, to push the car a mile, after the charging efficiency, the drive efficiency, everything, is considered.

So here are a few WPMs for the two cars studied here:

musings1(Note you can find miles per kWh by 1000/WPM)

What’s notable here is how similar the WPM is across the two cars, even with very different chargers. It’s also a good number because it gives you a relative amount of power per mile you can understand. Run that 350 Watt halogen light for an hour, and that’s the power you would need to move a car one mile.

Of course, the number of miles you get from a given number of watts varies with driving conditions, the driver, and the car. Fortunately we don’t have to consider that. The Environmental Protection Agency calculates that for us. And all we do is use the measure for comparison. That is, whether the EPA mileage is a good estimate or a bad one, we assume it is equally good or equally bad for both types of cars, because the EPA is assumed to be an impartial judge.

Tesla Model S Can Charge

Tesla Model S Can Charge At 396 WPM

For a long distance traveler, two figures on the car’s range are important. The 100% charge and the 80% charge range. The first because it defines the first leg of the journey. The second because all subsequent charges and legs are going to use the 80% figure. Otherwise, you would waste charging time and power trying to push the battery charge in its last, non-linear phase.

Now before we leave the realm of current cars, what does it mean that the charge time of the next generation, higher range leafs go up, but the next Tesla, the model E goes down in charge time? It’s a factor of the charger and the kWh capacity of the car. If Leafs get more capacity but use the same charger, their charge time doubles. If Teslas go down in capacity, but use the same charger, they actually get faster to charge.

The lesson of this is that it is not enough to increase the range of a car; you have to increase the charging infrastructure to match. Since Nissan will probably not want to have to explain why the new Leaf takes twice as long to charge, it’s a good bet that they will try to roll out a new charger with the new Leaf, most likely double the current Chademo 44 kW capacity. Whether this is an enhanced Chademo, or a completely new standard, is an open question.

For Tesla, there is no charger question at all. The model E will put no strain on their supercharger network. It will be a shorter range car, but it will make up for some of that by charging faster, on a percentage of total charge basis.

Calculating a long distance trip

So how do you characterize a long distance trip in an EV? If you do it “linearly”, by taking the 80% charge against the time to drive, you get:
musings3

Editor’s  note: duty cycle should read 82% for the Tesla, and 65% for the Nissan in above chart

Note that the “duty cycle” is the percentage of time the car actually spends driving.

This is the worst case picture of how an EV drives, and does not reflect real driving. For common long distance trips, the rule is going to be “100/80…”, meaning that the first drive of the trip is going to be at 100% charge, then the second at 80% charge, and all subsequent charges are going to be at 80%. The reason is simple. Long distance trips are going to start after a 100%, all night charge.

Using 100/80 calculations, short trips are going to look better. Longer trips are going to increasingly flatten out to approach the 80% charge duty cycle of the car. Since that is true, let’s use a “standard trip” for comparison. I’ll use a 500 mile trip at 65 miles per hour. That’s 7 hours 41 minutes of driving, which I think we can all agree would require a break or two even without the need to charge. It’s also a full day of driving without going into heroics like 12 hour driving with short stops, typical of college kids trying to make it to spring break in Florida.

I have calculated the times using the 100/80 rule, and even accounted for a driver to only charges the amount needed to complete the last leg of the trip:
muisings4And of course you noticed that I have stuck a new competitor in the mix, a generic gasoline drive car with 300 miles range. Now we have a new subject, “what is a refill break for a gasoline car”? Let’s define it.
musings5The “SBF”, of course, stands for “Spring Break Florida”, or the time it takes to refill for a college kid hyped up on caffeine, who starts the pump, enters the store on the run for more coffee, completes the fill, pays and bolts.

A "RLB" Is Probably More Like An Hour

A “RL” Break Is Probably More Like An Hour

I think it’s safe to say that 15 minutes is more the average on-the-go break. Its time enough to get coffee, a doughnut, wander a few minutes to see what mix tapes the station has, and pay and leave.

A food break is McDonald’s, eaten in the store.

Finally, a dinner break is a sit down meal with service.

So getting back to our 500 mile standard trip, the Tesla driver has waited 32 minutes longer than the gas car driver (its 42 minutes for a 80% charge). The leaf driver has waited 3 hours and 17 minutes longer than the gas car driver.

The Leaf numbers aren’t great, as you would expect. They are reasonable for a ferry, instead of a trip. That is, they are reasonable if your goal is to move the car to a new place, instead of just have it move you. The alternative is a car dolly pulled by a gasoline car.

The 3rd generation (of EVs)

Now of course I will take it in the shorts for declaring the next generation to be the 3rd. I hope you will forgive me for a purely relative comparison. In this article, the 1st generation was the GM EV1, the second the current crop of (mostly) lithium based cars, and the 3rd is the coming generation of longer range/cheaper cars.

The contenders are (cobbled from a list of announcements, test cars, and blind speculation):
musings6For the Telsa case, there just happens to be a car already in existence with the approximate specifications, the model S 60 kWh battery version.  Thus, I have used the figures from the 60 kWh version of the model S for this future car.

For the Nissan Leaf NT, the test car Nissan fielded has 48 kWh. We assume here, perhaps wrongly, that the new doubled battery capacity vehicle has similar characteristics as the old one, and that the range is in fact doubled.

Here’s the new charge and duty cycle calculations:
musings7

Note on above chart: duty cycle should read 82% for the Tesla, and 65% for the Nissan

The time to charge the Leaf to 80% has doubled. This is reasonable, since the charger power hasn’t changed, but the battery being charged has doubled. The resulting duty cycle is the same.

Here are the 500 mile trip specifications:
musings8Here the Tesla driver has waited 44 minutes longer than the gas car driver (its 32 minutes for an 80% charge). The leaf driver has waited 2 hours and 40 minutes longer than the gas car driver. The Tesla model E driver waited an extra 12 minutes than the model S driver. The Leaf NT driver waited 37 less minutes than the Leaf 2013 model.

What about the charger?

So the Leaf NT numbers are better, but not great. That still does not mean that a real 150 mile range is not useful. It means a long distance commute is far more feasible, and that weekend wine country trips are going to be easier.

However, the numbers strongly imply that Nissan would need to come out with a faster charger to match the longer range Leaf. So now lets speculate what would happen with Nissan came out with a “double strength” charger of 88 kW, versus the existing Chademo charger at 44 kW:

musings13Alright, now we are down to 1 hour and 13 minutes more than a gasoline powered car. The Tesla Model E and the Leaf NT would start to approach each other in performance. This makes perfect sense, because the basic specifications are converging.

In short, I suspect the numbers from a Leaf that is simply doubled in range, without an improvement in charger infrastructure, are poor enough that Nissan would be forced to go towards a higher power charger. If you believe the Chademo organization web site, they are against it. However, Nissan makes their own chargers, and could very well roll a double strength charger to their dealer organization.

This would not solve the problem overnight. It would still take a lot of time for the double strength chargers to become common. This is perhaps Tesla’s stronger hand. Their charger infrastructure is already north of 100 kW, and the new Model E would actually make less demands on it than the 85 kW model S.

The 4th generation (of EVs)

Let’s end this article with a twist on the usual “future projections”, of what the next, or the next after the next, EV might look like. Unfortunately (to my mind), the answer a lot of folks give is that the future EV should have similar performance figures to a gasoline powered car. This is unfortunate because in any competition between electric and gas powered cars, the gas powered car is going to win using the goals designed for gas cars. If you come out with a 500 mile range electric car, they will come out with a 1000 mile range gas car. Some gasoline cars are exceeding 400 miles of range simply because the fuel economy of the car was dramatically improved and the gas tank capacity has stayed the same. EVs need to compete on being different, not the same. Examples include: ability to charge at home, %100 clean, lower maintenance costs, etc.

Instead, let’s imagine that you are going to a rare (I suspect very, very rare), joint appearance of Carlos Ghosn and Elon Musk at the same EV press conference as part of a panel. You are in line to ask questions. You want to advocate for them to push for either higher KW chargers or longer range cars, but you don’t want to and don’t have the time to advocate for both.

So let’s imagine two future cars, one with 400 miles of range and a 100 kW charger, and one with 200 miles of range and a 200 kW charger. We’ll call them the Leafesla and the Tesleaf:

musings12

The 400 mile range, 100 kW charger Leafesla is the winner, but note that the time difference is down to the 13 minutes, about the time it would take to charge the car at 200 kW.

Note also that the 400 mile range car nearly converges in time with the gasoline car. This seems impossible with a 30 minutes charge time. However, it works because it is possible to short charge the car to reach the destination. Thus, only an 18 minute charge sufficies.

Conclusions

Telsa and Nissan appear to be headed for the same market, a $35k car around 200 miles range. This is a normal result of an open competition market, you go where the money is. In this contest, Tesla would seem to have the advantage because, although each maker built out a charger infrastructure to match their cars, Telsa starts at a high charger level and would be going downward, where the opposite is true of Nissan. Of course Nissan could aggressively roll out new chargers and even things up.

The calculations

To write this article, I relied on constructing a BASS or “Big As you like it Spread Sheet”, of which you can have your own personal copy here. I’ll look forward to folks finding my errors on the sheet.

Notes

The Tesla numbers don’t strictly add up. The issue is that Tesla states 30 minutes on Supercharger to reach 170 miles of range, but gives us a time of “as little as 20 minutes”  to reach half range. We use EPA figures for reasons discussed above. What we care about is the 80% range, since that is the linear section of the charge curve. With the Leaf, the maker specifies 30 minutes to 80% charge, meaning we have a fixed method to calculate. With Tesla, we can use either the 30 minute/170 mile figure or the 20 minute/133 mile range (half the EPA mileage). Naturally they don’t match. The 170 mile calculation is based on Tesla’s own 300 mile range. The way I “solved” this was to find for the 80% range given the 170 miles in 30 minutes figure by using the %80 range of their 300 mile figure as 240*30/170 or 42 minutes to reach 80% charge. Its reasonable because the charge times are stated to be linear until the 80% charge time is reached, and can thus be solved by a ratio. Thus, using the EPA figures together with the 80% charge time we calculate the rest, and these equations are applied the same way across both Leaf and Tesla.

You’ll also note that the EPA figures calculated against the WPM or Watts Per Mile didn’t quite match. That is, the Tesla Model S 60 kWh and 85 kWh did not quite match at the EPA stated ranges of 208 and 265 miles, respectively. I “solved” this by downgrading the range of our “model E” by subtracting 6 miles from the range. To me this made sense, because the two cars, running on the same charger, should have identical WPM figures in the linear range.

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88 Comments on "Op-Ed: Musing “3rd” Generation EVs And Range"

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I am excited to see the new cars!

I think the only #’s that really matter regarding charging is miles/hour.

I don’t care if the charger is rated a 100kW or my battery size is rated at 60kWh or what the % of charge is.

What I want to know is, how long it will take me to get 100 miles of range (or whatever).

This would be nice to have a in graph form so times for all distances can be looked at.

I have been saying for a while that the existing 40-50 kW CHAdeMO installations are all a waste of money. The installation costs are 10x that of 80A J1772 which provides 20 kW. In an EV future, we need many charging slots, not just one here and there. With the huge installation costs for CHAdeMO 50 kW and the fact that it still isn’t fast enough to support reasonable long distance travel, this is all a waste of money. It would serve us much better to put in a lot of 80A J1772’s which charge at 20 kW and let Nissan spend the money instead on upgrading each Leaf to 20 kW AC charging. At 20 kW, it is far cheaper to set up many EVSE’s and the standard is supported by everyone. 20 kW is more than enough for charging at work or charging at home, even with 85 kWh battery packs. With 48+kWh battery packs which will become the norm in a few years, who is going to bother charging for 30 min at Walgreens at 6 kW? Nissan can come back with CHAdeMO or CCS when they have a car than can handle 100 kW charging, either… Read more »

240V doesn’t support the charge speed 480V does, for a given amperage. That’s part of the reason 40kw L3s are more than “twice as fast” as 20kw L2s. DC has a lot to do with it.

And there is no real limit. 480v (typically three phase) is an industrial standard. The standard neighborhood transport voltage is in the KV range (1kv and up). If you are an industrial customer with big power needs, they run you a KV line and you provide your own transformer. The power company could give you enough power to turn your car to ash if they wished.

Total capacity is another issue, which is why some have complained that the system would colapse if EVs really took off. However, assuming that the total fleet size stays the same, the charge time is immaterial over the average. That is, a car that uses a KV to charge in 15 minutes is not going to use more total power than a 480v charge in 30 minutes.

Sorry but I don’t at all agree. Putting in 20KW EVSEs rather than 50KW EVSEs is a lose for long distance travel. When we get to 150+ mile EVs, the vast majority of owners will use home charging – other local charging options aren’t needed. And 20KW still takes a while to charge.

A well thought out 50KW network will be very useful. The problem with the current chademo network is that it was put in with no thought to actual utilization. If you took all those chargers and placed them in the same manner that Tesla did, you could drive a Leaf coast to coast in a reasonable amount of time (not that I’d want to but it would be possible). Also, you don’t need that many to form a credible network. Tesla is looking at about 200 SCs for the national network. I’d guess chademo would need to be in the 400-500 range.

I’m happy with my Volt’s 10 miles per hour charge rate….

That’s because on the road, you bring your own 80+ MPH charger. AND it can be used while driving.

While I applaud you for driving a Volt, some of us look forward to going “all in” on electric cars.

Don’t ride that bus then Brian

I’m not quite sure what you’re saying here.

My point is that MrEnergyCzar seems to be blowing off this entire article, saying simply that the Volt solves everything. He misses the point completely when he points out that his Volt works great with only 10MPH charging. The point is that it has on-board 80+MPH charging, and that it “charges” while you’re driving. Thus you don’t need to wait around.

The Volt is a wonderful solution for today’s needs (of most drivers), using today’s technology. This article focuses on tomorrow’s technology, and his comment does nothing but seemingly poo-poo those of us for whom the end-goal is a fully-electric car.

I answered in more detail below. I think he is pointing out that there is another valid solution to the well laid out argument. EREV drivers want an all electric highway too.

The point that I take from the article is a very pragmatic approach to match every aspect of the ICE experience (currently) and where the future takes us. If the article fails at anything is highlighting the current superior aspects of the EV experience and leaving out the EREV option which is what I took MrEergyCzar to mean.

EREV drivers do not have the perfect solution for sure for there is still an ICE in there, but they have a solution all the same. EREVs want an all electric highway, they are dealing with the current technology at hand, which I think it is very important for newcomers to know that there are some really valid solutions like the LEAF and Volt out there now. I don’t like when it is implied that “these EVs are a good idea but not quite ready”.
We are on the same page Brian.

Thanks for the clarification, Mark. I know most EREV drivers have the same long-term goals as BEV/Hybrid “families” like mine. Heck, we both accomplish the same thing today – local electric driving, efficient ICE for long-range.

I do get frustrated when Volt drivers start complaining when any particular article doesn’t mention their solution of choice. We always come back to the same discussion, and it makes it hard to talk about something different like this article tries to.

It is similar to the recent PV + 2 EV story here. Some of the commenter lamented that the author didn’t mention global warming specifically when discussing these technologies. IMO, not every discussion on EVs and Solar needs to talk about global warming. Just like not every story about long-distance electric travel needs to talk about EREVs/PHEVs.

As a Volt owner, I wish i had 7-10kW charging. The Model E (or anyone else with a 200 mile $40k BEV) is on my buying horizon in 2017/18.

I also would appreciate faster charging for my Volt. At least 30 A for 20 mph charging

GSP

MEC, I understand your point regarding 10 miles per hour of charging working for some people, but I disagree that GM should be satisfied with such a slow recharge rate. I spent 4 months with no home outlet to charge my Volt and charged it exclusively at area public chargers. It was fairly tough finding time to spend 2-3 hours per day to get the power needed to keep my Volt going primarily on electricity. 10 kW charge rates would mean that a long lunch break would be enough to keep the Volt charged.
More importantly with an EREV, it would mean that a lunch break would be enough to keep the genset off on days where the Volt owner is going to be driving more than 40 miles. Plus, upgrading from 3.3 to 6.6 wouldn’t cost much at all. And 10.0 like the RAV4 EV wouldn’t cost that much more than 6.6.
Is it necessary for an EREV to charge faster than 3.3? No. But it is a very, very nice option to have. Not as important as more rear seat legroom, but close.

I agree completely. Except that faster charging would be much better than more rear seat legroom (I sit in front).

GSP

I charge the Tesla at 4 mof range per hour and the Imiev at about 3. We drive the 2 vehicles 1750 miles per month. Never charge anywhere but home.

The article clearly targeted longer road trips but I hate the fact that the author mentioned his “co-workers” having to charge at work… this just perpetuates the myth that you have to be able to charge everywhere you go… I am quite sure those Model S owners got to work with 200 or more miles left on their battery to get home since you start off every morning with a full charge courtesy of your garage… workplace charging is for Leafs, not Teslas

Assuming you’re not one of those 41% of the population that does not have a garage or permanent parking spot. Workplace charging fills a vital role for the tenants amongst us.

…or that you live here in Texas. The building management here won’t install chargers (or even 120V outlets) because “God created Earth with enough gas and oil until the rapture”.

Seriously. 🙁

Electric-Car-Insider.com

Oh my … sincere condolences

No really said that . . . did they?

I agree. The tesla rate is so slow (as a %) that I don’t see how it makes sense to charge the Tesla at our work. I still see them plugged in, though.

Having a Model S, I can vouch for that. I almost never charge anywhere but home. Never locally. On a couple of 100 mile day trips I have but even that wasn’t really necessary.

On the issue of apartment dwellers without charging spaces, they simply aren’t candidates for EVs. Over time, this will change as EV charging becomes a selling point for apartment buildings. Trying to replicate the gasoline filling station model is a huge mistake. I can’t imagine sitting around for even 30 minutes to charge up.

The only time I can accept sitting around for 30 minutes to charge is on l-o-n-g trips. For those, I want to stretch my legs, pee, find some candy and sodas, look through the trinkets, then get back on the road.

I see the problem with tenants but that is something that will change with greater adoption of the technology. As a renter myself, in Ohio, I was able to receive a property modification approval to install an EV charging station (I opted for 50amp, 14/50 outlet) in my garage with the condition that I pay for it myself and leave it behind when I move. I am in the process of relocating now to Minnesota and have had four different apartment complexes agree to accomodate a similar request. It will get better!

Electric-Car-Insider.com

Ouch, I would hate to leave behind a $500-$750 charge station. Simply install an outlet instead and when it’s time to go, unplug and go.

Is your washer and dryer, or refrigerator, or large microwave hard wired?

Nissan wouldn’t have to aggressively role out new chargers if they licenced the right to use supercharger technology.

Is Tesla even entertaining offers for licensing? Might not be an option for Nissan (or BMW, or GM, etc.), if Tesla isn’t open to negotiating.

The CHAdeMO standard was penned with the ability to charge up to 100kW. What happened? The fastest CHAdeMO charger I’ve heard of is 62.5kW. Have they given up on increasing the capacity?

Tesla has publicly invited other BEV makers to use their proprietary fast chargers, since day one. But there are many reasons why established automakers won’t play ball with the new kid on the block– even if it hampers their own plans for grabbing marketshare.

Very nice report. Well done Scott. You have done an excellent job of explaining the issue.

I think the new LEAF range will make a huge difference and expand driving capabilities. People still need to make the long trips at times and they at least need to know what to expect.

In fairness to helping people understand the electric drive experience, it would be nice to at least make the EREV comparison since the ICE comparison is there and mention the primary existing Chevy Volt and the new BMW i3 Rex as to how they address this issue.

By the 4th generation, it may no longer be required, but for today it is a very valid solution. Currently Volt drivers are driving 60%+ on electricity with a 38 mile AER. It will be very interesting to see what the BMW i3 Rex numbers work out to be. If I were to guess, I would say still 20%. A trip to the beach, mountains etc. eats up more of the driving experience that one might think. Still, it is a solution unless the purest think the bus, lawn mower, plane, etc. miles don’t count on the path to a fossil free solution.

Calculations for Model E should include a 20 percent weight reduction, since Mr. Musk has been adamant that is the target size / weight difference from the current Model S. Less weight, more range, less batteries, even faster recharge than your assumed 60 kWH version?

You’re making me hot…..

Active cooling might fix that… 😉

You lost me with that complicated stuff…

Here is a practical view:
San Jose to San Diego about 9 hrs and uses 150 kWh. Lets compare a 85 kWh and a future 125 kWh
Model S. I leave 15 kWh as reserve so I can use
70 kWh in the S85 and 110 kWh in the S125.
S85 – 150-70 = 80 kWh charge on the road
S125 – 150-110 = 40 kWh

So I have cut the amount of energy needed to charge on the road by two and the time even more. S85 = 2 stops, S125 = 1 stop.

Future is 350 EPA battery plus fast charging at many locations.

Not clear from the article what the exact charge were assumed in the Level 2. Seems like 16Amp in most cases. L2 can provide up to 70A (18KW) per the J1772 spec.

This analysis lends power to the argument that the L2 AC charging rates in vehicles should be increased as there is a gain in BOTH Range and Access to the current infrastructure while keeping or decreasing the charge times required.

Building out more L2 high current (70A) infrastructure would serve 100% of the currently shipping vehicles without necessitating multiple charger formats and higher infrastructure costs.

The article is heavily biased towards L3 chargers, if that was your point.

My L2 at home is 30 AMP (leaf), with 40 AMP wiring (still have no idea why). I did the install myself. I could have just as easily gone to 100 AMP charging. There is lots of room left in L2/home chargers.

The limitation is the on-board charger on your vehicle. The EVSE is an intelligent power source — nothing else. The rectification of power occurs in your car, not on the EVSE. Having a 100A EVSE will not make your LEAF charge any faster.

By the way, if your EVSE pulls 30A, you are safe using a 40A circuit. According to all state’s electrical codes, you need to have some “breathing room”.

I figured that the 40amp thing was headroom. I came to the conclusion that they weren’t really using the 40amps because the wire size within the charger itself was 30amp rated. However, the code allows you to use smaller gauge wire, its a function of the length of wire vs. the amps it carries.

How did you come to the conclusion that the onboard charger is permanently limited to 30 amps? What is the reason later cars cannot introduce a 100 amp (or about) AC charger? The wire size of the 25′ cable?

The duty cycles in the article are wrong. It should read:

Tesla (both Model S and Model E): %82
Nissan Leaf (both 2013 and NT): %65

Apologies.

Scott

Good read, but I think “BEV and L3” were enough the focus that, as an infrastructure commentary it fell short of painting what will happen with L2.

Longer charge times at charger stops aren’t really the problem with L2. For the workplace, the inability of many venders to sell kwh, by law, or their choice not to go with hourly fees, leads to squating and an insufficient number of chargers. With the new PHEV’s, the ratio of ‘time at charger not charging’, to ‘time at charger while charging’, is going to go through the roof.

Decent article, but you got really slopping with confusing watt-hours and watts.

***mod edit*** fixed up those couple of snafus, thanks ***mod edit**

I guess 120KW and 44KW would be more accurate. Not sure what the issue is with watts (as in watt/hours) per mile?

watt is a unit of power, i.e. how fast the energy flows.

watthour is a unit of energy, which you should be looking at when stating energy consumption.

watt/hour is watts per hour and almost never relevant in the context of EV’s.

Thanks for changing the charger capacity ratings from energy to power. The problem with “watts-per-mile” is that it should be “watt-hours-per-mile”. A watt is a unit of power, an instantaneous measurement of the rate of energy with respect to time. It takes a certain number of watts to maintain a given speed under a given set of conditions. A watt-hour takes this rate of energy per time and multiplies it by time again to get you back to just energy. It’s a little silly, but it’s the common language. You measure a vehicle’s efficiency by describing how much energy it takes to go a certain distance.

Do not use watt-hours and watts interchangeably. I hear it happen all the time in conversation, that’s one thing, but don’t put it down on paper, or worse, on the internet! The general public will never wrap their heads around these concepts if the supposed experts can’t get it right.

+1

You explained it so much better than me!

+1

Phrases like “the total cost, in watts, to push the car a mile” indicate the author’s lack of a basic understanding about that which is opining.

Did you want to explain exactly how I got that wrong, or were you just intending to insult me?

Note, by the way, that I have the guts to use my real name.

As has been explained very eloquently by mustang_sallad, watt is a unit of power (=how fast the energy flows), not a unit of energy.

What you will see on your electric bill is that you pay your energy per kWh. The Model S uses 0.396 kWh to cover 1 mile. 0.396 kWh = 396 Wh.

“At 120 kWh (the Tesla maximum supercharger rate), and 396 kWh per mile,”

“So I will use “watts per mile” (kWh/mile).”

Please, correct the units. It should be a 120 kW rate, not kWh. And luckily the Tesla doesn’t use 386 kWh per mile, but only 386 Wh per mile. And it is not watts per mile, but watthour per mile.

How would a petrolhead feel if a car site stated that “the newest Lamborghini sports a V12 with maximum torque of 790 hp?

I come to an EV site to read from EV specialists. EV specialists know electrical units. Period.

Good catch, it should read “At 120 kW (the Tesla maximum supercharger rate), and 396 W per mile”.

it should read “At 120 kW (the Tesla maximum supercharger rate), and 396 Wh per mile”.

Addition: ‘Wh per mile’ is exactly what the Model S displays on the dash.

Energy per mile, so Wh per mile is the only thing that can be correct.

(Watt per mile often used spoken language to save a syllable)

Saying “watts per mile” is just wrong. It makes no sense.

As you point out, the dash says Wh per mile. Wh stands for watt-hours.

Oh geez, no!!

Your sentence should read “At 120 kW and 396 W·HOUR per mile”…
Or better IMHO: “At 120 kW and 886 J/m”, in joules per meter.

Joule/meter conveniently is also kJ/km (go do that with yards and miles…), and makes the inevitable eventual comparisons with other fuels easy. I don’t ever want to later hear of hydrogen cars’ efficiency expressed in “kW·h per mile equivalent” or other such non-sense, for example.

The watt is a unit of POWER, or rate of transfer of energy.

The joule and watt·hour are amounts of ENERGY — it’s what you’d get transferring 1 watt for one or 3600 seconds, respectively. 1 watt·second = 1 joule.

Rate vs quantity. Like speed vs distance. Not at all the same things.

[sigh] Americans with units…

+1 on all accounts. Would be just one more great opportunity to make the unit conversion.

“My car gets 40 rods to the hogs head, and that’s the way I likes it!” – Grandpa Simpson

ROFL. Thanks for the link.

You might want to consider these numbers instead: Tesla E at 48 kWh and New LEAF at 36 kWh. Then also consider that the New LEAF might be available more than TWO years before the Tesla E. By the time the Tesla E hits consumer garages, Nissan should already have a larger car also with 48 kWh battery. I think the more interesting question is when Nissan will offer the CCS charging interface.

Plus, by the time the Model E comes out the Leaf will be much cheaper. I suspect at least a $10k gap between vehicles – probably much more with a fully loaded Model E.

For long trips, I think we need:
1) >200 miles range EVs with fast-charging batteries
2) really fast fast-chargers (200-500 kW) everywhere (especially along highways,…)

And for those who cannot charge at home:
3) fast-chargers in the cities, towns and villages
(yes, same as gas stations, more or less…)

Add Starbucks at each coffee shop, where people wait in line anyway, and you’ve got yourself a viable business opportunity.

s/coffee shop/gas station/

Wireless charging at all drive-through restaurants. While you’re waiting for your latte, you get some electrons and don’t even have to get out of the car (because we are all that lazy).

If you look at US driving trip statistics, it will probably never make sense for most people to own an EV with a 200-300 mile range, as that range will be used so seldom.

The most plausible efficient use of battery-based EV’s for most users will be to own one with a 40 kWh battery and 100-150 mile range tops, with a 50 kW FCDC charge rate to cover that occasional 200 mile trip. For that occasional 500+ mile trip, go to Enterprise Rent-an-EV and rent a 100 kWh Tesla or equal with 150 kW FCDC charge rate.

A lot of people kind of do that now – have a cheap paid-for car for daily local travel and rent a nicer, more comfortable car for that long annual trip.

+1 and would add that those affording one car may be the up and comers, who will have a different perception of time at a charger, and be willing to sit for 30-60 minutes on those dozen, or so, days they go long.

The 120-150 mile range could soon be the coastal solution, as we close not that many more L3 gaps.

I dunno, it’s not always about “making sense”. We have gas cars with 700 mile ranges. Does this make sense?

I would like to have 200 miles+ at my fingertips whenever I want it. I don’t want to have to rent a car.

I have a lot of sympathy for the argument that it is unnecessary to roll 300 mile range cars for everyone. I commute 60 miles round trip by car through heavy traffic, and although that is close to the total range of the Leaf at 75 miles, realistically I could go much farther. The difference is that I have access to excellent workplace charging facilities.

However, for the future, I don’t think it makes sense to just say that we can rent a car for the weekend. The reason is simple. The long term goal of the EV revolution is to get RID of gasoline cars. Clearly that is going to mean having cars with broader range than is required on a day to day basis.

I do think that (around) 200 miles fills the requirement, as indeed is the basic point of the article. The key to this is charging resources. The good thing is that we are not even near any sort of real charging limitations. ie., charging times are one thing that can be improved on EVs without invoking rocket science chemistry.

O.K. Interesting article. But what all this discussion points up to me is that (assuming we get improved and upsized batteries) the true Achilles heel of EVs is probably not range. It is charging time on longer road trips, and the infrastructure to support fast charging. In the grand scheme of things it’s a reasonable goal for the ultimate EV to be rechargeable on the road with about the same “time penalty” as an ICE car. However today, my trusty 9 y/o Prius (soon to be replaced by a Leaf) can go 500 miles on a 7 minute fill-up when driving I-5 between CA and OR. An EV at 3mi/kWh would need 167 kWh of “fuel” in 7 minutes to match that – a charging rate of 1.4 Megawatts. That’s huge! In any real world we will never get there. The excess battery/charger heat load needing to be blown away, at say 95% charge efficiency, would be ~70kW. That’s enough to heat a decent size commercial building in an Alaskan winter – maybe. So it would require a monstrous thermal handling system on-board or off-board the vehicle. Even an 85kWh Tesla on a 135kW Supercharger falls far short of this… Read more »

Heading for a 15 minute charging target is reasonable, especially with a 200 mile range car. Why would we need to go below that? Because some kids can fuel and bolt in 5 minutes?

Lets go back and look at the spreadsheet results for a 200 mile range car with 200KW charger:
distance to go Leg Distance of Leg Charge time Drive time Total Time (m) Time h Time m
500 leg 1 200 0 185 185 3 5
300 leg 2 160 16 148 164 2 44
140 leg 3 140 14 129 144 2 24
0 leg 4 0 0 0 0 0 0
0 leg 5 0 0 0 0 0 0
0 leg 6 0 0 0 0 0 0
0 leg 7 0 0 0 0 0 0
0 leg 8 0 0 0 0 0 0
0 leg 9 0 0 0 0 0 0
0 leg 10 0 0 0 0 0 0

Totals
500 31 462 492 8 12

So here you are getting 15 minute charge times (on average), and the total trip time is only 16 more minutes, mostly due to the limited range.

I would argue that you are better off picking a real limit for miles range and charging, then work on the price of the car.

I don’t think that is a reasonable expectation. First of all, to make a valid comparison, consider the time needed to fuel that Prius before one leaves for the trip. This has to be added to account for the fact that the EV was fueled while the driver slept.

We also have certain expectations for fueling our cars based on our experiences with gasoline. If I took a 300 mile trip about once per month (in fact, I typically do), I would gladly pay the extra 30 minute penalty that today’s Tesla Model S 85 would incur because I would NEVER have to stop for fuel on any other trip. So compare 30 minutes at a supercharger per month to how many minutes at a gas station per month? About the same, maybe even more when you consider the time to go out of your way to get to the gas station.

When I have to buy gas for the hybrid, it adds about 15 minutes to my commute. Yes, I have timed it.

+1

Meeting or exceeding ICE capabilities is the right target, when practical. As MikeM points out, this is not practical for recharge times.

This will not be a problem for EV adoption however. Two stops of one half hour each for a full 600 mile day driving is all that is required today for a Tesla Model S. There is no need to make the stops only 5 minutes. That isn’t even enough time to clean the windows.

When not on long trips, you never take time to fill up, since the battery is full every morning. That is much faster and better than a gas car.

GSP

The debate about 3rd or 4th generation EV’s is useless unless we also debate about the world that 3rd and 4th generation EV’s would be designed to inhabit. One thing we frequently get too hung-up on at these forums is projecting current driving practices on a future world that has either voluntarily or been forced to make the transition to an electric-based travel infrastructure. It is very likely a lot of things will have changed. Rail will be much more dominant. The suburbs may have taken an hit and commuting may be less prevalent. The totally-fossil-fuel-dependent airline industry will probably be history. Our whole attitude about “I can go anywhere, any time, inexpensively and quickly” will have probably changed.

Or alternately, EVs, autonomous driving and increased renewables in the electric supply chain will have made commuting more acceptable, and thus even more prevalent than today.

Thus leading to more sprawl and the accelerated destruction of what little open space we have left. I hope that doesn’t happen. With any luck, road traffic will keep that in check…

Some people make a big deal about the gas mileage of the Volt under CS mode. To a very small group of Volt drivers this is meaningful but to the rest it is a bunch of hot air. Once BEV’s have a >150mile real world every day range, the on-the-road fast charge times fall into the same category as CS mileage for the Volt. It will only matter to a very small percentage of actual EV owners. To the media and other small thinkers it will probably remain a big deal until EV’s are seen as commonplace.

Of course if the car has less than 200 miles of full charge range it won’t be seen as a practical road trip car regardless.

Good analogy. Very insightful.

GSP

Except for rural America who needs an EV too.

Though a L3 charger in the end is more practical than a gas station, your need for a fueling station (of any kind of fuel) is totally different using an extender.

Can’t limit the thought process to fossil fuel for that one is on the way out. I am not so sure that even Musk is not considering an air battery as a secondary chemistry. He said only batteries but he didn’t say what kind.

I am 100% in agreement with the author on the deductive process for chargers, IMO, there is just another piece to the puzzle.

Doesn’t it bother anyone that the table with 88 kw charging is exactly the same as the table with 44 kw charging for the Nissan Leaf NT? Am I the only one who actually read the article?

Sorry John, that was a editorial mix-up with the uploading of the tables. Fixed now.

After reading all this, I still think that for long range EV driving, the only #’s that really matter are how often & how long you have to stop to recharge.

After reading through most of the foregoing, I see no mention of the battery chemistry currently in development which could potentially be a game changer. IBM is supposedly working on battery systems that will yield 1000 miles. They are not alone in this battery technology race. Li ion batteries may become antiquated while still in the cradle.

Pretty cool article and fun to ponder the possibilities, and the comments are pretty good too (nobody is fighting, for the most part 😉 ).

I learned a very interesting selling point by reading Brian’s comment about considering the full fueling time for a vehicle on all trips. If 90% of our miles are local trips fueling at home and 10% “road trips”, in comparison to a gasoline car that ALWAYS requires a longer non-home refuel time (to get to and to complete), then spending 10-15 more minutes per stop in an EV on our much less frequent road trips could actually be a smaller investment in total fueling time for most people.

I made a 300 mile trip this past week … I rode the train and it was way faster, more productive, and relaxing than any car :).

The article is interesting but indeed it should take into account the EVER solution like the Volt and the BMW i3. The 100% EV purity goal may seem to be loadable but it actually is counterproductive in helping the EV cause. Much of the reason why the EV market share is still bellow the one percent mark is exactly due to that integrist approach of the 100 % electric. If one consider the facts in a pragmatic way long range has only 2 solutions. One you make a big battery of 120 KWh that allow a range of 400 miles and you combine it with hypercharge at 1 MW, or two you use a decent battery of 60 KWh and combine it with a Rex and 100 KW superchargers. At present the first solution still being off limit, the second solution appears more at hand and certainly available for direct globalization against the still ruling standard gasoline cars.