There’s Really No Consensus Designing Electric Vehicles

Electric Vehicles

DEC 14 2017 BY EVANNEX 47

Tesla

A fleet of electric vehicles from Tesla (Instagram: everything.tesla)

HOW SHOULD AUTOMAKERS DESIGN THEIR ELECTRIC VEHICLES? THERE’S NO CONSENSUS.

Most consumer products tend to become more uniform as their market matures. You’d be hard-pressed to find much practical difference among appliances, computers, or even smartphones, from different brands. That’s because, over the years, companies learn what features are important to consumers, and they figure out the cheapest and most efficient ways to build their products.

When it comes to cars, the surface differences can be striking – a Mustang looks very different from a Corvette – but under the hood, they all require the same components: engine, transmission, etc. Over the course of more than a century, automakers have gotten extremely good at building these things, and there really isn’t any secret sauce or better mousetrap. Many of them order from the same suppliers, so some components are not only similar across different brands, but identical. Of course, automakers are continually making improvements, but at this stage, the basic design of a gas-powered car isn’t likely to change much.

Enter electric vehicles. This is a new breed of automobile, and automakers are still experimenting with different motors, different battery chemistries, and even such basic concepts as where the battery should be located. The various EV-makers have vastly different ways of doing things.

*This article comes to us courtesy of EVANNEX (which also makes aftermarket Tesla accessories). Authored by Matt Pressman.

To investigate the technical differences among different EVs, the management consulting firm McKinsey & Company had a team of engineers physically disassemble 10 electric models, including a Tesla Model S, a BMW i3, a VW e-Golf, a BYD e6, a Chevy Bolt and two model years of the Nissan LEAF (2011 and 2017). The results reveal huge differences in the powertrain components that make these cars go.

Of all the technologies that go into an EV, batteries are arguably the least mature, with the most room for improvement, so it’s not surprising that different automakers still have very different ideas about the best kind to use. McKinsey’s engineers found an array of battery cell designs with three different geometries (cylindrical, prismatic, and pouch), and multiple chemistries. Each design has its pros and cons, and McKinsey didn’t identify any clear winner when it comes to overall performance. It found that automakers have achieved similar energy density increases, regardless of what battery design they use – over 30 percent from 2011 to 2018.

When it comes to thermal management, there’s a wide range of powertrain cooling and heating solutions in use. The Nissan LEAF and VW e-Golf get by with passive (air) cooling for their battery packs, but use liquid cooling for their motors and other powertrain components. Tesla’s vehicles use an interconnected liquid cooling and heating system for the entire powertrain. Other EVs use various different combinations of cooling and heating methods.

Electric Vehicles

Above: Differences in powertrain and thermal management design among electric vehicles (Source: McKinsey & Company)

As Tesla has often reminded us, its cylindrical battery cells have by far the highest energy density of any design currently available – approximately 245 watt-hours per kilogram, compared to 195 Wh/kg for pouch cells and 160 Wh/kg for prismatic cells. However, at the pack level, taking the required housing and thermal management into account, the score is more even: 132 Wh/kg for cylindrical cells versus 138 Wh/kg for pouch and 104 Wh/kg for prismatic.

Unsurprisingly, McKinsey’s teardown vindicates another of Tesla’s design innovations: native EVs (those designed as EVs, as opposed to those adapted from an existing gas-burning vehicle) have big advantages in both driving range and interior space. “Native EVs optimize battery packaging; non-native EVs force the battery into the awkward footprint of the ICE platform,” says McKinsey. A purpose-built EV’s battery pack can be designed as a simple rectangle, so the natives can offer up to twice the range without forcing up the price. The native EV’s pack can be placed at the bottom of the vehicle (a “skateboard” design, as Model S designer Franz von Holzhausen called it), giving it up to 10 percent more interior space, compared not only to non-native EVs but also to legacy ICE vehicles in the same segment.

These days, automakers devote much effort to reducing the weight of their vehicles (so much so that the industry has decided that “lightweight” is now a verb). Surprisingly, however, McKinsey finds that lightweighting is of secondary importance for EVs. Whereas some older EVs rely on aluminum (Model S) and carbon fiber (the BMW i3), for some of the newer mass-market EVs, aluminum amounts to only 5 to 10 percent of total vehicle weight – close to the 5 percent used in an average ICE vehicle.

Tesla made extensive use of aluminum in Model S, but for the lower-priced Model 3, it went back to using mostly steel. Another case in point: the Nissan LEAF uses a combination of steel and aluminum body panels, and the upcoming next-generation vehicle will use about the same proportion of the two metals.

Why the waning interest in aluminum? Because it turns out there are more cost-effective ways to improve range. According to McKinsey, “Generational leaps in powertrain technology yield significant weight reductions, which are then directly reinvested into lower-cost structural materials. At today’s manufacturing cost, batteries, not lightweight materials, are the key to longer ranges.” Aluminum body panels are also more expensive to repair – several Tesla owners have reported being presented with shockingly high repair bills after collisions.

Electric Vehicles

The degree to which manufacturers of electric vehicles have supply chain vertical integration (Source: McKinsey & Company)

McKinsey’s report found big differences not only in the kinds of components used but in the way those components are developed and manufactured. Using the supplier logos on the various components, combined with publicly available information, the engineers were able to piece together a picture of the different EV-makers’ powertrain supply chains. These range from almost total vertical integration to nearly full outsourcing. The most vertically integrated of the automakers studied is BYD, which makes all the major powertrain components for its e6 in-house. In second place is Tesla, which sources battery cells from Panasonic and transmission components from BorgWarner, but makes its own battery packs, motors and power electronics. At the other end of the spectrum is the Chevy Bolt – not only the powertrain but much of the user interface comes from Korean supplier LG.

It’s plain that automakers are still learning how best to design electric vehicles. There’s even more uncertainty concerning the question of how they will make money from them. “Automotive OEMs will have to reconceive their business model to create new income and profit streams for EVs,” the McKinsey report found. “Today, they rely heavily on customers upgrading the base vehicle with additional engine, transmission, comfort, and safety features, as well as on aftermarket parts and services to boost profitability.”

Even Tesla indulges in the practice of pushing high-margin options – it has announced that Model 3s ordered with options will be delivered first, while budget buyers who ordered strippies will go to the back of the queue. According to McKinsey however, there are two reasons why this may not be a viable strategy for EVs.

First, there is little room to differentiate model variants by performance. Current EVs already offer plenty of acceleration for most drivers, and the new generation (Model 3 and the Bolt) offers adequate range. McKinsey notes that the EVs it surveyed offer no more than four combinations of engine and transmission types, compared with the 10 to 20 possibilities available for a typical ICE model.

Second, base EV configurations already contain many features previously thought of as options. All electric vehicles have a high base price, thanks to the cost of the batteries, so OEMs have felt compelled to entice buyers by offering more features in the base configuration of an EV than in a comparable legacy vehicle, thus sacrificing what was once a high-margin income stream.

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Written by: Charles Morris; Source: McKinsey & Company

*Editor’s Note: EVANNEX, which also sells aftermarket gear for Teslas, has kindly allowed us to share some of its content with our readers. Our thanks go out to EVANNEX, Check out the site here.

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47 Comments on "There’s Really No Consensus Designing Electric Vehicles"

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SJC
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SJC

We standardized on 12 VDC lead acid batteries, but there are dozens of sizes and shapes.

mx
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mx

That’s the problem with standards.
This standard should have died with a modern update 15 years ago.

SJC
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SJC

It is an example of a partial standard yet lots of sizes and shapes. Makers to not want to be commodities, so they are different.

ModernMarvelFan
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ModernMarvelFan

I thought eGolf has a cooling fan blowing across the battery pack. That would be “active cooling”, just not liquid cooling.

Passive cooling is what Nissan does which doesn’t even have a fan blowing across it.

gary
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gary

No cooling fan on the e-Golf. It is indeed passive.

Mike I.
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Mike I.

The Kia Soul EV has a fan like you’re describing. Not the e-Golf.

jim stack
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jim stack

Our SOUL EV used active air cooling fan and it’s not enough for the Phoenix area or the Southern USA. 10 of my friends and I have had the battery fail within our 3 year lease.
QUOTE=gary
December 14, 2017 at 2:26 pm
No cooling fan on the e-Golf. It is indeed passive.

Mike I.
December 14, 2017 at 3:35 pm
The Kia Soul EV has a fan like you’re describing. Not the e-Golf.

cr08
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cr08

As a Ford C-Max owner with ‘active’ fan only cooling, it may as well be considered passive. Fellow C-Max owners have a lot of reports of significantly reduced battery capacity due to high HVB temps.

ModernMarvelFan
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ModernMarvelFan

Thanks for the correction!

Well, I guess eGolf is another LEASE ONLY BEV then.

SparkEV
Guest

Passive cooling implies there are structures built into the system to allow cooling, like cooling fins on air cooled engines. Leaf battery is just a box. Calling it “passive cooling” is not correct. More accurate term is no cooling.

Pushmi-Pullyu
Guest
Pushmi-Pullyu

In the technical/scientific sense, “passive cooling” is the correct for the Leaf’s battery pack, altho as noted above, not for the Kia Soul EV. Even in the Leaf, there is some conduction of heat away from the batteries thru the metal box around the pack. It’s not like the batteries are thermally isolated from any heat sink.

Cooling fins, or a lack thereof, may indicate faster or slower passive cooling, but either way the cooling is passive rather than active.

SparkEV
Guest

If “passive cooling” means anything that tend to increase entropy of the universe, yes, Leaf is passive cooled. Following that logic, anything and everything in the universe is “passive cooled”.

Magnus H
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Magnus H

Nissan e-nv200 have active cooling of the battery.

HVACman
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HVACman

Thermal management notes:

Note that Tesla S battery can only be heated when the vehicle is moving, scavenging heat from the motor and power electronics.

They creatively added stationary battery resistive heating to the Model 3 by using the same overall TMS concept as the Model S, but also adding the ability to run DC current through the Model 3 motor windings while the vehicle is parked to make some resistive heat without creating any torque. I don’t recall if it can do this any time or only when plugged-in.

Note the Bolt’s battery heater only runs when plugged-in. Bro recently reported his Bolt had a slow DCFC charging issue after sitting unplugged for a couple of hours in the cold while on a family trip.
Apparently, though driving 60 miles after the soak before attempting to recharge the charge, the Bolt’s battery never warmed up enough to accept a high-kW fast charge, so it took a lot longer to get the kWh to get home.

Though the article didn’t discuss it, EV cabin heating techniques are also all over the map – everyone does it a little different.

EV thermal management is still a work-in-progress.

georgeS
Guest
georgeS

@HVACman
Hi Keith,
u said

“Note that Tesla S battery can only be heated when the vehicle is moving, scavenging heat from the motor and power electronics. ”

I believe it has an electric heater to heat the battery glycol loop also. We wrote the article.

https://insideevs.com/tesla-model-s-recycles-waste-heat-to-warm-the-battery-bower/

Does Borg Warner really make the Model S gearbox???

I thought they got dropped when Tesla gave up on the 2 speed gear box.

Also what is interesting is the battery energy densities. Cylindrical win at cell level but at pack level there is no difference. Kind of points to less efficient packing efficiencey for the cylindrical cells which we have always suspected. Not to mention worse heat transfer.

HVACman
Guest
HVACman

Oh, man, you’re right about the Model S heater. Howe could I forget? Terminal cluelessness sneaking in, I guess:)

Regarding cylindrical/pouch cell efficiencies at cell and pack levels – I wonder if they were comparing the current-generation Bolt with the previous-generation Tesla pack and cells. The Model 3 pack with the 2170 cells may be a little more efficient. But also may be a lot harder to build on an automated assembly line.

SparkEV
Guest

“We” wrote the article? You related to George Bower?

Pushmi-Pullyu
Guest
Pushmi-Pullyu

Yeah, that caught my eye too. Is that the editorial “we”, meaning just you, GeorgeS? Or is “George Bower” a pseudonym for a collaboration of two or more writers?

GeorgeS
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GeorgeS

@ PMPU & spark
My name is george s bower

Ambulator
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Ambulator

My initial assumption was that HVACman must have helped write it. It now appears that it was just a slip of the pen.

Devroot
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Devroot

The Bolt will run the battery thermal management system while unplugged as long as the SOC is above 30%. This is for both heating or cooling the pack, depending upon conditions.

pjwood1
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pjwood1

“McKinsey finds that lightweighting is of secondary importance for EVs.”

I didn’t realize the steel Model 3 just happened to be ~3,600 pounds. What manufacturers, and the steel industry, quickly got good at doing was optimizing the use of steel in a way that would add the least weight.

Perhaps McKinsey sees greater compliance with CAFE coming through drive-train (EV), rather than weight reduction. That may say a lot about their thinking about EV penetration, if I’m not reading into things too much.

God/Bacardi
Guest
God/Bacardi

In racing you’d be amazed how much of a difference unsprung weight makes…Strong and affordable 9.9lb, 15×7 racing rims have been around for over a decade (K1s) and even 17s that are under 15lbs…Also things like aluminum hat two piece rotors all could make a significant difference…Next is the hub assemblies…Lastly, the tires also make a difference in terms of LRR but automakers have limited input on the tire tech…

Pushmi-Pullyu
Guest
Pushmi-Pullyu
pjwood1 said: “I didn’t realize the steel Model 3 just happened to be ~3,600 pounds. What manufacturers, and the steel industry, quickly got good at doing was optimizing the use of steel in a way that would add the least weight.” Thank you! The article is really misleading when it says: “Tesla made extensive use of aluminum in Model S, but for the lower-priced Model 3, it went back to using mostly steel.” It’s not that EV makers no longer try to reduce the weight of car bodies using aluminum or CFRP (Carbon Fiber Reinforced Polymer); it’s that they have figured out how to save weight while still using steel, which is cheaper (altho it’s possible CFRP might someday be cheaper than steel, with economy of scale). The Model 3 car body is made of three types of steel: ordinary mild steel, high-strength steel, and ultra-high-strength steel (and some aluminum here and there, too). Auto makers have figured out how to shape and fold thinner steel to give it more strength, reducing manufacturing costs over use of aluminum while still providing similar weight savings. Unfortunately, the cost for repair of ultra-high-strength steel is, like aluminum body sections, also rather higher… Read more »
mx
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mx

You should add suspensions.
It’s time to BAN Torsion beam suspensions.

theflew
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theflew

Given all the people that have test drove a Bolt or own one don’t mention the suspension as a weakest it must mean that it sounds worse on paper than it does in reality.

mx
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mx

I think this is more to due to reviewers wanting to review the next year’s Bolt, and not be dropped.

georgeS
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georgeS

good article EVannex!

Lou Grinzo
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Lou Grinzo

A lot of us, including the plug-heads on this site and many within the car makers, are still coming to grips with what a transition to electrified vehicles will really mean. I’m always yammering on here about the market psychology aspects of the transition, and that’s certainly part of the big picture, in addition to things like building out more public charging infrastructure, figuring out better ways to accommodate at-home charging for people who live in apartments and other garage-free homes, etc.

And then there are the knock-on effects, such as a reduced business for some suppliers — anyone here bought a catalytic converter or muffler or EGR valve or… for their BEV lately? The auto parts stores scattered all over the place will face a grim future once EVs steal enough market share to reduce the demand for almost everything those stores sell beyond tires and pine tree air fresheners.

God/Bacardi
Guest
God/Bacardi

Theory is Amazon and places like Walmart who will ship routine maintenance parts are slowly killing them anyways, expect lots of mergers…

Still lots of amenity parts/sensors that can break, wiper blades, battery coolant, windshield wiper, cabin filters, bearings, etc…

Only things I’ve heard for the USis that for 2040, California would LIKE to ban new ICE sales…There will be a lot of people who buy ICEs up to the last minute and still others willing cross state lines…

Devroot
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Devroot

Bolt automagically runs the the battery thermal management system while unplugged as long as SOC is above 30%. This is both for cooling and heating the battery.

John Doe
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John Doe

I think EVs are just as uniform as ICE cars..

There are front, mid and (used to be) rear placed engines.
There are gasoline, diesel, wankel and LNG engines.
There are manual, automatic and semi automatic (robotised) gearboxes.
There are front wheel driver, rear wheel drive, all wheel drive.
There are various suspension types, like air, coil, leafsprings, torsion springs and so on..
Batteries are placed under drivers seat, in the trunk, under the hood..

So.. an ICE car normally have 4 wheels, an engine that burns some kind of fuel, has a steering wheel and some seats..
An EV have 4 wheels, an electric motor, a lithium battery placed low, a steering wheel and some seats..

Pushmi-Pullyu
Guest
Pushmi-Pullyu

“There are manual, automatic and semi automatic (robotised) gearboxes.”

You left out CVT transmissions.

But you’re emphasizing the differences. Wankel engines are not different than gasoline or diesel engines; they’re just gasoline or diesel engines with a different piston design. They are also a design which has been tried and failed, just like many variations over the years. I think I read about some new PHEV design using a Wankel engine for the range extender, but in general I think it’s safe to say the Wankel is obsolete. Other than the change from carburetors to fuel injection, a change enabled by advances in electronics, gasmobile engines have remained essentially unchanged for a century or more.

And engine-in-the-front is the standard for modern automobiles. Correct me if I’m wrong, but mid-engines are a niche application found only in some sports cars.

John Doe
Guest
John Doe
Yeah, I agree on everything you said. Just added the wankel engine, as it is a total redesign of a gasoline engine. Just like there are variations on how an electric engine can be made. The wankel engine is super simple, few parts, light weight, high power to weight ratio with an amazing RPM.. but it is thirsty, and they have never manages to make the seals work for a long time – like a round piston ring does. Even though Mazda has done a lot to make them better. We had about the engineering behind car engines at the university, and a modern engine is complex. They were probably at the peak of quality a few years back. Everything they have done since then has to do with emission control, which results in engines lasting a shorter time. In Europe people remember for example diesel engines from Mercedes, that lastet “forever”. They had maybe a 3 liter engine, and had less then 100hp, now a 1 liter engine has probably 120hp. The same goes with old Volvo gas engines, that lasted for ever. Dual mass flywheels, insted of just a solid piece of machined steel. Differens sensors, EGR valves,… Read more »
Another Euro point of view
Guest
Another Euro point of view

Thanks for the article, very informative.

georgeS
Guest
georgeS

Looks like the Model S 85 kwh pack is more like 156 kwh/kg versus 132 as stated in the article for the MS60 pack. The P100 pack would be better. S0 it’s not a tie on wh/kg at the pack level cylindrical vs pouch. Cylindricals win……………except I’d like the BoltEV’s pack energy density to compare as well it should be better than 132.

Bill Howland
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Bill Howland

I don’t get why the article says the battery is heating on a BOLT ev ‘only when plugged in’. On the 4 GM cars I own or have owned (volts, bolt, and elr) the battery will use its own storage to heat itself if it is too cold while driving.

Seeing as the cars have always worked that way I’m surprised they’d get that wrong.

(The roadster would only self-heat if it was VERY cold outside – the design engineers deeming that the battery can DISCHARGE while it is quite cold, but wouldn’t let it charge at all if it was under 35 deg F).

orinoco
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orinoco

With ICE cars you can save a lot more energy using lightweight materials because the ICE is so extremely inefficient that saving weight means saving much more fuel than electric power in BEVs. VW did this with the 3L-Lupo, an extreme lightweight, spartan car which consumes less than 3 liters Diesel/100km, equivalent to about 30 kWh/100km.
A VW e-Golf weights about twice the 3L-Lupo and consumes only half of it, because the electric engine is so much more efficient.

Bojan
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Bojan

To me it seems like the main difference is not overall efficiency as such, but specifically regenerative braking.

Weight mainly affects the amount of energy used for acceleration (and subsequently lost while braking) while having little effect on the amount of energy used for driving at a sustained speed, which is mainly governed by aerodynamics. Regenerative braking reduces the braking energy losses by a significant percentage, which greatly reduces the impact that weight has on the overall efficiency of the vehicle, while aerodynamics become much more important as a result.

jim stack
Guest
jim stack

I like to see the screen data available on all electrics. Here are some I’d want the same on all electric vehicles.

1-Show the volts, amps and Power when charging. Only Tesla seems to do this.

2- Display the driving efficiency in miles per kWh. Some show wH/mi Watt Hour.

3-Show the battery temperature. This can affect the life of the pack.

4- Show the battery capacity % and in kWh. Then you can tell if your battery has degraded.

Bill Howland
Guest
Bill Howland
Jim Stack: Agreed. With both the BOLT ev, and VOLTS, from the beginning (late 2010), the cars never tell you what they’re doing until they think something is broken – so in that sense its a modern Idiot light. Even worse because a Check Engine on the VOlt must be further diagnosed to see what the problem is…. The other thing is that if the 12 volt battery is disconnected for service, it will take quite a while before the dashboard regains all its sanity. In my ELR for instance, you lose Tire Pressure Monitoring for quite a while until the computers feel like displaying it again. With the BOLT ev they’ve gotten worse. Not only do you lose the ‘b’ trip odometer that you get with the VOLT, it also won’t tell you expected charge times at anything but the fastest level. If you plug into 110, and let it charge for a while, then if it feels like it the system will tell you what day and time the car will complete charging. And of course, GM thinks with ALL its cars that the customer is too stupid to make his own decisions. I have to drive around… Read more »
SparkEV
Guest

SparkEV is optimal. Electronics (DCDC, etc) are happy in one temperature zone, Motor/gear in different one, battery in yet different zone. It also makes it easy to run one of them harder to see what may work best; makes for best test platform.

Pushmi-Pullyu
Guest
Pushmi-Pullyu
Good article, altho it does gloss over some details (such as the difference between ordinary mild steel and high-strength steel used in car bodies). Compare to the early days of the motorcar revolution, when early auto makers tried out very different layouts and controls. The very earliest cars had the motor mounted behind, perhaps attached to the rear axle. There were wooden wheels, tillers instead of steering wheels, and open cockpit cars which had a hand-operated brake lever mounted on the outside of the car! In the Model T, you have to manually control the spark advance or retard (to accelerate or slow down) with a hand-operated lever mounted on the steering column. I was reminded on just how early it is in the EV revolution just the other day, when reading a review of the Honda Clarity PHEV. The the way the controls interface with the driver, controlling whether the car is in EV mode or gasmobile mode, are very different than they are in the Chevy Volt. Definitely some experimentation going on there, with different auto makers trying different things. It’s going to take some years, probably decades, for the market to sort out what works the best… Read more »
theflew
Guest
theflew

The model 3 moved everything to the touch screen to save cost, not increase usability – that’s the problem.

Smartphones have been out well over a decade and still have physical volume controls – why? Because it’s more convenient when you need to adjust without looking at the screen.

Why Not?
Guest
Why Not?

I read an interesting article on a German website the other day. They drove a BMW I3 & Tesla Model S 100 Km (62 miles) under nearly identical conditions and added 100, 200, and 300 kg (220, 440, & 660 lbs) in extra weight. They found that the energy usage was only minimally affected, .1 KWh higher for the Tesla and .57 kWh for the I3. They attributed that to the energy regained through recuperation, which goes up with vehicle weight. Their conclusion was that lightweighting is not as crucial in EVs as was originally thought.

Here is a link to the article if you would like to practice your German.

https://www.elektroauto-news.net/2017/gewicht-keine-entscheidende-rolle-reichweite

Mr. M
Guest
Mr. M

For ICE the weight formula is like 0,1l (=1kWh) more per 100kg increased weight. Assuming BEV efficiency =100% and ICE efficiency = 33% the added consumption for BEV would be 0,3kWh/100kg.

Mr. M
Guest
Mr. M

Most consumer products tend to become more uniform as their market matures….. The EV market is not matured. Wie just recently saw the Start of the second Generation of BEV. Most habe still first gen for sale.

A mature product nicht need 3-6 cycles.