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BMW Outlines LifeDrive Architecture for Upcoming Megacity Vehicle; A Focus on CFRP-Enabled Lightweight Design and Safety

Mcv
BMW Group Megacity Vehicle Design Sketch. Click to enlarge.

At BMW Group’s Innovation Days: Mobility of the Future briefing in Munich, the company outlined its plans for the upcoming electric Megacity Vehicle (MCV), due onto the market in 2013 (earlier post), as well as the new LifeDrive architecture upon which the MCV is based.

The LifeDrive concept consists of two horizontally separated, independent modules. The Drive module—the aluminum chassis—integrates the battery, drive system and structural and crash functions into a single construction. Its partner, the Life module, consists primarily of a high-strength and extremely lightweight passenger cell made from carbon fiber reinforced plastic (CFRP). The new vehicle architecture enables new production processes which are both simpler and more flexible, and use less energy, BMW said.

The Megacity Vehicle is a revolutionary automobile. It will be the world’s first volume-produced vehicle with a passenger cell made from carbon. Our LifeDrive architecture is helping us to open a new chapter in automotive lightweight design. Indeed, this concept allows us to practically offset the extra 250 to 350 kilograms of weight typically found in electrically powered vehicles.

The drive system remains the heartbeat of a car, and that also applies to electric vehicles. Powertrains also remain a core area of expertise of Bayerische Motoren Werke. Electromobility and the hallmark BMW driving pleasure make an excellent match, if you go about things the right way. For this reason we are developing the powertrain for the Megacity Vehicle in-house—that includes the electric motor, the power electronics and the battery system.

—Klaus Draeger, Member of the Board of Management for Development

The importance of weight. Powering a vehicle electrically means more than just replacing the combustion engine with an electric drive system, BMW said. The electrification of a vehicle involves extensive revisions to the entire body, as the electric drive system components place very different demands on the packaging space in a vehicle. Based on its development work on the MINI E and BMW ActiveE concept projects, BMW concluded that “conversion cars”—i.e., vehicles designed to be powered by combustion engines and subsequently converted to run on electric power—do not represent an optimum long-term solution when it comes to meeting the demands of e-mobility.

As important as these vehicles have been in amassing knowledge on the usage and operation of EVs, the company said, the integration of an electric drive system into a foreign vehicle environment is not the best way of exploiting the potential of e-mobility. Conversion cars are comparatively heavy. In addition, accommodating the big and heavy battery modules and special drive electronics is a complex job, as the structural underpinnings of the vehicles are based on a very different set of requirements.

BMW therefore set out to develop a new body concept which carefully addressed the full gamut of technical peculiarities of an electric drive system. Lightweight design is particularly important for electric vehicles because, alongside battery capacity, weight is the key limiting factor when it comes to the vehicle’s range. Under acceleration, in particular, every kilogram of extra weight makes itself clearly felt in the form of reduced range. And in the city—the main area for an electric vehicle—the driver has to accelerate frequently due to the volume of traffic.

However, the drivetrain of an EV is far heavier than that of a vehicle with a combustion engine, full tank of fuel included; an electric drive system (including battery) weighs around 100 kg more. The battery is the chief culprit here. To cancel out the extra weight it brings to the vehicle, the BMW Group is working on the application of lightweight design principles and the use of innovative materials.

Drive Module. The Drive module brings together several functions within a lightweight and high-strength aluminium structure. This is the basic body, complete with the suspension, crash element, energy storage device and drive unit. Weighing around 250 kg and with dimensions similar to those of a child’s mattress, the energy storage system is the driving element of the integrative and functional design of the Drive module.

The initial priority in the conception of the Drive module was therefore to integrate the battery—the largest and heaviest factor in the electric vehicle in terms of construction—into the vehicle structure so that it would be operationally reliable and safe in a crash.

The Drive module is divided into three areas. The central section houses the battery and surrounds it with aluminium profiles. The two crash-active structures in the front and rear end provide the necessary crumple zone in the event of a front or rear-end impact. The Drive module also houses the components of the electric drive unit and numerous suspension components. The electric drive system is, as a whole, much more compact than a comparable combustion engine, cleverly accommodating the electric motor, gear assembly, power electronics and axles within a small space.

Life module. The Life module is a passenger cell mounted on the load-bearing structure of the Drive module. The primary characteristic of the Life module is its construction mainly out of carbon fiber-reinforced plastic (CFRP). The selection of this high-tech material—on this scale—for a volume-produced vehicle is unprecedented, as the extensive use of CFRP has previously been thought of as too expensive and still not sufficiently flexible to work with and produce.

CFRP offers many advantages over steel; while it is at least as strong as steel, it is also around 50% lighter. Aluminium, by contrast, would save 30% in weight terms over steel. This makes CFRP the lightest material that can be used in body construction without compromising safety.

BMW believes that, with more than ten years of intensive research work and experience with a program of process optimization, it is currently the only carmaker with the manufacturing experience necessary to use CFRP in volume production.

The extensive use of this high-tech material makes the Life module extremely light and gives the car both a longer range and improved performance. It also delivers handling benefits—the stiffness of the material makes the driving experience more direct. At the same time, CFRP enables a higher level of ride comfort, as the stiff body dampens energy inputs extremely effectively. As a result, unwanted vibrations on the move are eliminated: there are no rattles or shakes.

The integration of all the drive components into the Drive module allows the removal of the transmission tunnel through which the engine’s power was previously channelled to the rear wheels but which took up a lot of room in the interior. The Megacity Vehicle (MCV) therefore offers more room for its occupants within the same wheelbase. This new structure also enables the integration of new functionalities, allowing a new degree of freedom in the design of the vehicle architecture.

CFRP in body construction. CFRP offers a number of benefits as a material for a vehicle body. It is extremely corrosion-resistant and does not rust, giving it a far longer lifespan than metal. Complex corrosion protection measures are unnecessary and CFRP retains its integrity under all climatic conditions.

Carbon fibers are exceptionally tear-resistant longitudinally. The fibers are woven into lattice structures and embedded in a plastic matrix to create the carbon fiber/plastic composite material CFRP. In its dry, resin-free state CFRP can be worked almost like a textile, and as such allows a high degree of flexibility in how it is shaped. The composite only gains its rigid, final form after the resin injected into the lattice has hardened. This makes it at least as durable as steel, but it is much more lightweight.

The high tear resistance along the length of the fibers also allows CFRP components to be given a high-strength design by following their direction of loading. To this end, the fibers are arranged within the component according to their load characteristics. By overlaying the fiber alignment, components can also be strengthened against load in several different directions. In this way, the components can be given a significantly more efficient and effective design than is possible with any other material that is equally durable in all directions—such as metal.

This, in turn, allows further reductions in terms of both material use and weight, leading to another new wave of savings potential. The lower accelerated mass in the event of a crash means that energy-absorbing structures can be scaled back, cutting the weight of the vehicle.

In addition to lightweight design, passenger safety also played a major role in the development of the LifeDrive concept. The current impact stipulations for a vehicle body are extremely stringent and a wide range of different crash scenarios have to be taken into account. Generally speaking, this presents development engineers with serious challenges, especially as far as the use of new materials is concerned. However, the combination of aluminium in the Drive module and the CFRP passenger cell in the Life module exceeded all expectations—even in the initial testing phase.

Its rigidity, combined with its ability to absorb an enormous amount of energy, makes CFRP extremely damage-tolerant. Even at high impact speeds it displays barely any deformation. As in a Formula One cockpit, this exceptionally stiff material provides an extremely strong survival space. Furthermore, the body remains intact in a front or rear-on impact, and the doors still open without a problem after a crash.

The ability of CFRP to absorb energy is truly extraordinary, BMW said. Pole impacts and side-on collisions highlight the safety-enhancing properties of CFRP. Despite the heavy, and in some cases, concentrated forces, the material barely sustains a dent. This makes CFRP perfectly suited for use in a vehicle's flanks.

There are limits to what CFRP can endure, BMW noted. If the forces applied go beyond the limits of the material’s strength, the composite of fibers breaks up into its individual components in a controlled process.

In April, SGL Automotive Carbon Fibers LLC, the joint venture between SGL Group and BMW Group announced that it will build a carbon fiber manufacturing plant in Moses Lake, WA. The fibers manufactured at Moses Lake will be used exclusively for the MCV. (Earlier post.)

Comments

shopa

Do I dare to disagree with the engineers at BMW? I do.

About carbon fiber: "Its rigidity, ... ability to absorb enormous energy." "High speed impacts..barely any deformation."

Crumple zones are supposed to crumple.
They are not supposed to be rigid.
Rigid delivers killer g forces on body.

Their Drive Module Crumple Zone protects in front or rear end impact. My invention protects sides, as well as front and rear.

My invention can use cheap, rigid polyurethane foam.

www.safersmallcars.com

Please help me get some support to develop my invention which has a US Patent.


Davemart

Somehow I imagine that BMW engineers are up to speed on crumple zones and have built them in where needed.
Some parts need structural rigidity, some parts to crumple.

HarveyD

Forward looking vehicle design and materials. By the time it hits the roads (2020?), batteries are going to be up to 3x lighter, so their weight is going to be more than 100% offset.

shopa

To Davemart:

When a car crashes into your door, you need more than an airbag. Look at the video on my website to see an expensive vehicle hitting a pole sideways at 20 mph. Not pretty. Only 20 mph.

www.safersmallcars.com or YouTube at

http://www.youtube.com/watch?v=o5sLfULSADQ&feature=youtube_gdata

ToppaTom

IF it reduces cost it will be used.

IF.

I dare say if I want economy of ownership, BMW is way down on my list.

Original cost - Yikes
MPG - Yikes
Maint/Repair costs - Yikes (just paid $80 for a 2003 540i 4.4L PCV, (yes a PCV) plus installation - Yikes.
Reliability - Yikes (R&Rd the plastic water pump also - hoses were $60 ea)

But there is another list -
Conspicuous Consumption it's called -
BMW is near the top.

Davemart

Harvey D:
I didn't quite know where you got your information from, but it appears the answer is clear and simple. You invent it!:-0
For those of us who prefer to go on actual information available, the Magacity is due in 2013, not 2020.

Shopa,
I agree car safety could be improved. The use of carbon plastic will help us get towards this goal
Check out the crash performance of racing cars.

HarveyD

Dave:

This one is strictly a design and PR effort. The carbon fiber plants are not designed or built yet. This forward looking light weight e-car may not hit the road before 5 to 8+ years if it ever does it that format. By that time, lithium batteries will have much better energy density, longevity, quicker charge/discharge capabilities etc; over 100 different makes of first and second generation EVs will be on the roads from 4 continents and 20+ countries. That's normal progression in a competitive world.

Interesting decade.

In the last 6 years (2004-2010), digital camera batteries went from $59.95 to $5.95 while their size was reduced by almost 50% and energy storage was increased by almost 2x. Simultaneously, recent Digicams consume 30% to 60% less energy per photo with 3x the number of pixels. In other words, my new 2010 camera does about 4 to 6 times the work with a battery costing 1/10 the price. Those are facts and past history now. Will we see the same changes in the next 6 years (2011-2117)? Maybe, but probably not to the same extend. We will see...

drivin98

Harvey,

BMW is currently building a plant in Moses Lake whose entire carbon fiber output will go into the MegaCity vehicles which are due to arrive in 2013.
http://green.autoblog.com/2010/04/07/bmw-megacity-ev-makes-carbon-fiber-jobs-in-america/

It's not a PR effort.

Peter_XX

To shopa: Have you tried to sell your idea to Dinky Toys?

Safety with CFRP? I just recently saw Mark Webber crash his Formula 1 car at ~300 km/h. He stepped out from his car without any injury. Not too bad for a CFRP car chassi... Of course, we cannot compare directly with passenger cars but I would not be afraid of driving this BMW.

To Harvey: We will for sure use more lithium batteries in the future. Thus, the price for batteries might increase again in a not too distant future. There is not enough lithium on the planet. So, pure electric cars will be too expensive... forever. We just have to be careful with the resources and go for hybrids instead to minimize the use of rare elements. It seems difficult enough to make those cars affordable.

Davemart

Peter xx
You have been reading Tahil, who also has a theory that the World Trade Center was destroyed by the CIA with mines, or some such!
Lithium is actually a very common element.
It is used as lithium carbonate, which contains around 18% lithium by weight.
Chemetall gives world reserves at around 150 million tons of lithium carbonate, at 1kg/kwh enough for several billion EV's.
In Clay Valley in Nevada the US may have enough lithium to power all the US vehicle fleet.

The cost of battery grade lithium carbonate is around $50/kg, so the cost in the Leaf is about $1200.
The raw material before processing is around $8/kg

Lithium is not rare, and is not the major cost in battery cars.

Mannstein

Harvey:

The present digital cameras use less energy per picture than older versions. That has nothing to do with batteries and everything to do with new generation ICs and image sensors.

We will not see a similar reduction in electric cars since the present motor technology is about as good as it's going to get from an efficiency stand point. Reducing vehicle weight which BMW is proposing is one obvious way to reduce power consumption. It's the low hanging fruit they plan to harvest.

Mannstein

@ Davemart

"You have been reading Tahil, who also has a theory that the World Trade Center was destroyed by the CIA with mines, or some such!"

I haven't gotten to the CIA yet, since I'm still wondering about the 5 Israelis dancing the Hora on a roof top in New Jersey as they were filming the event. They were picked up by the FBI which shortly released them. Last these clowns were seen on Israeli TV boasting that they were there to film the event. In other words they admitted to have had prior knowledge of what would go down. No pun intended.

We subsequently went to war with Iraq which had nothing to do with 9/11 and wasted treasure and innocent lives.

Patriotic Americans ought be asking themselves who was in the know and for whom was this war fought.

HarveyD

Mannstein:

I'm also using the new lower cost/improved capacity batteries in my old camera with surprising results, ie. twice the number of photos per charge at 1/10 the price of 6 years ago = 1/20 the energy cost per photo. If you could improve your 2004 EV in the same magnitude or your 2010 EV 6 years down the road (in 2016) you may not need another ICE vehicle.

MG

@ Davemart, Mannstein:

There is a good engineering site about 9/11, with expert opinions:
http://www.ae911truth.org

HarveyD

I fully agree with Davemart that lithium is not a rare element. The planet has more than enough lithium for 10+B EVs. Secondly, lithium batteries can be recycled to recover most of the lithium used. Thirdly, future batteries could use a lot less lithium per Kwh and/or per EV.

The same goes for future clean e-energy production. Nuke + Solar + Wind + Hydro + Geothermal could produce more then the energy required for 10+ B EVs. No great challenge there.

Peter_XX

Lithium:
With the same arguments about abundancy you could claim that there is enough gold in the sea for everyone. However, that doese not make us all rich. The trouble with most of the lithium resources is that the concentrations are far too low. Basically all the (economically) recoverable lithium is found in a couple of salt lakes in South America. You should read the report: "The Trouble with Lithium 2" (see link below). This clearly explains the problem. Besides lithium, you can find a number of rare earth metals and other rare elements used in EVs and HEVs. For example, we have seen escalating prices of Neodymium during the last year. This is at a stage when we have just started to introduce EVs and HEVs on the market. Why should the cost go down in the future?

I would like to buy a drilling machine from Bosch with lihium batteries but I find it far too expensive compared to one with NiMh batteries. Thus, I have hesitated for a very long time. The same story as with electric cars: I cannot afford the Tesla...

http://www.meridian-int-res.com/Projects/EVRsrch.htm

HarveyD

Quebec Hydro R & D Lab has produced a lithium EV battery that can withstand 30,000 cycles. It is to be mass produced in Taiwan soon. That should be enough for 100 years for the average EV owner and would effectively reduce the lithium required to 1/10. (ie 100 years instead of 10 years)

Davemart

Peter XX
You really should look at some proper sources instead of making unsubstantiated claims.
Right here on this forum they were looking a resource that they aim to process 16,000 tons of lithium carbonate a year, or enough for many hundreds of thousands of EVs a year, far more than the currently planned Nissan US production.
In Hope Valley there may be enough lithium to move the entire US car fleet to lithium.
China not only has it's own supplies, but is negotiating with Burma a deal for access to reserves there.
To date no-one much has looked for lithium, as current supplies far exceed needs, and no shortage is predicted by Mineral journals etc.

I fail to understand what you imagine the current price of lithium batteries for power tools has to do with fundamental shortages of the material, which costs a fraction of the total cost.
NiMH is a more mature technology, so they have been able to reduce production costs more.
Lithium technologies are catching up fast.

Peter_XX

Davemart
You should read the source I gave you. It is definitely not unsubstantiated! You can find refrerences to this study everywhere. Surprisingly, nobody has found any real flaw in the study. If you start to look at the topic you will also find that many other share this concern.

Another issue is that lithium is not the only rare element used in these batteries. We could have some hope for finding replacements for those elements. This is probably where the best prospect is for cost reductions.

HarveyD made a reference to other consumer electronics, so I wanted to remind him about a real case. I could also mention that a (non-OEM) battery to my mobile phone or my digital camera cost 30€. These batteries are already in mass production and there has been absolutely no price cut in the last 3 years. Do I have to remind about the Tesla again, which use consumer-type batteries... When the cost for those batteries start to come down, I could perhaps believe that there is some prospect for EVs. It must be apparent to anyone that this will not happen in the near future. With no cost reduction, we will see EVs only in niche applications. HEVs has a much bigger potential, although PHEVS will, to some extent, be plagued by the same problem.

Davemart

Peter XX
I've read it. The main rebuttals were led by Evans:
http://www.lithiumalliance.org/about-lithium/lithium-sources/56-an-abundance-of-lithium

In the trade journals of the minerals industry the problem that is discussed is always of oversupply of lithium for many years - Tahil etc are so far out of touch with realities that he is little discussed.

Here is someone in the minerals field who is in general gloomy about resource prospects - but not for lithium:
'There is no present demand for lithium not met by present supply and then some, and no foreseeable demand that cannot be met by increasing the production of lithium from existing, already capitalized, sources such as those in Chile, the U.S.A., China, and Argentina. Such increases would be the most economical way to deploy capital. That is how the free market will do it.'

http://seekingalpha.com/article/210067-afghan-lithium-and-other-mineral-nonsense

Peter_XX

Davemart
Yes, I expected that you would bring up Evans... He is linked to the lithium industry so he is definietely biased. I have also looked at his arguments against the Meridian report. Basically, he could not find anything wrong, which is remarkable. So my conclusion is clear: we will not have enough lithium at a reasonable cost to power all vehicles. That is, unless anything radical will happen and I have not seen that yet... I would better buy the Bosch drilling-machine with lithium batteries I have been longing for well before the price increases.

Calvin Brock

Ron Gremban invented a very simple way to add batteries to a Prius and eventually tested it. ENGINER made their lithium ion version. best rated mattresses

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