What If An Electric Car Could Use Its Body As A Structural Battery?

NOV 17 2018 BY EVANNEX 33

COULD AN ELECTRIC VEHICLE’S BODY ALSO BE ITS BATTERY?

The question of where to put the heavy, bulky battery is central to electric vehicle design. Tesla pioneered the “skateboard” approach – mounting the battery at the bottom – and other EV-makers including BMW and Audi have followed the trend.

*This article comes to us courtesy of EVANNEX (which also makes aftermarket Tesla accessories). Authored by Charles Morris. The opinions expressed in these articles are not necessarily our own at InsideEVs.

Above: A different outlook for implementation of an electric vehicle battery (Image: Charged via Chalmers University of Technology)

But what if the body panels of a vehicle could form part of its battery? Researchers at Sweden’s Chalmers University of Technology have been exploring the possibility of using carbon fiber as a structural battery. The team has studied the relationship between carbon fiber’s microstructure and electrochemical capacity, and is working to develop a combination that is both mechanically sound and energy-dense.

Above: Carbon Fiber (Image: Interesting Engineering via Texdata.com/Wikimedia Commons)

The team has discovered that carbon fiber’s electrical and mechanical properties can be controlled by carefully rearranging its graphitic order and crystallite sites. Fibers with small, disorganized crystals have better electrical characteristics, and are slightly stiffer than steel. Large, highly-oriented crystals provide even better stiffness (over twice that of steel), but the electrochemical properties are not adequate for practical use as a battery. The team is now experimenting with ways to increase the composite thickness in order to overcome the mechanical challenges while boosting total energy storage capacity.

Above: Chalmers Professor Leif Asp describes his research findings (Youtube: Auto & Moto via Chalmers University of Technology)

“The key is to optimize vehicles at system level – based on the weight, strength, stiffness and electrochemical properties,” says Chalmers Professor Leif Asp. “That is something of a new way of thinking for the automotive sector, which is more used to optimizing individual components. Structural batteries may perhaps not become as efficient as traditional batteries, but since they have a structural load-bearing capability, very large gains can be made at system level. In addition, the lower energy density of structural batteries would make them safer than standard batteries, especially as they would also not contain any volatile substances.”

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Written by: Charles Morris; Sources: Chalmers University of Technology via ChargedGreen Car Congress

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

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33 Comments on "What If An Electric Car Could Use Its Body As A Structural Battery?"

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Does not work if battery needs liquid cooling.
When Solid State Battery is a commercial thing maybe this will too.

It’s a solid state battery. Did you read the last sentence? No volatile substance = solid state by design.

This has been proposed before, although I don’t recall using this particular method. Main concerns are safety, is it more prone to catch fire in an accident? Will it provide desirable crumple zone effect? And will small dent accidents be very expensive to fix? Cheaper to build? And finally, this better be a very long lived battery, because you are certainly not going to swap it out.

Intriguing idea, but I very much doubt it will be practical.

Not only that, but what happens if you lean on the car? What about when it rains or snows? Shorts and shocks seem more likely with this kind of idea as well

Every battery requires some sort of casing or coating that is non-conductive, to prevent unintended loss of stored energy from contact by a conductive surface. Obviously a battery that’s part of an automobile’s structure would be protected with a layer or coating of non-conductive material, probably plastic.

This isn’t a concern worthy of discussion.

I really enjoy the low center of gravity in my Tesla(s) due to having the battery at the lowest possible height. I do not favor adding any batteries above the wheels because of how that placement would impact handling and stability.

All BEV’s that use the skateboard design for battery placement enjoy the low CofG. It might be possible to put some battery in other places and not unduly affect the handling AND enable a higher battery capacity to be used than the chassis might otherwise allow.
I don’t think it is a yes or no situation.

It would not affect it at all. It’s about replacing parts with equal parts that also works as batteries. The weight distribution will be the same.

The whole idea is that it’s structural parts that will not only be structural but have another use. It would actually improve handling since you could shave off some weight.

If you get batteries in all panels instead of only in the floor, that definitely changes the centre of gravity.

“The weight distribution will be the same.”

What? It couldn’t possibly be the same.

Distributing the weight of the battery throughout the body of the car, instead of having it all at the bottom, will inevitably raise the center of gravity.

Engineers would also have to be careful to balance weight between front and back, if designing a car this way.

If they are essentially carbon figure, I doubt you have to the same concerns with center of gravity.

The BMW carbon fiber chassis can be lifted by two people. Carbon fiber based cars will inherently be lighter than your Tesla.

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There is no reason why TESLA would not be Carbon fiber based car as well. It just mass production + cost issue now (For everyone not just Tesla)

Right, this is why BMW is dropping its use of carbon fiber structure in its EVs post the i3 and i8; COST is CRITICAL.

He is talking about centre of gravity, not weight.

Also, the article clearly states that the carbon fibre doubling as battery is not as stiff as ordinary carbon fibre, i.e. it would have to be thicker. In fact it would have to be *much* thicker in order to provide meaningful capacity…

That is just the “life module”, i.e. the body in a body-on-frame design, and does not include a bunch of things that are part of a unibody, like the frame, outer panels, b-pillars, suspension mounting points/reinforcements, etc. Not fair to compare this to a unibody. When you tot up all of the other parts that would be part of a unibody and normalize for the size of the car, the i3 is not all that light.

I really don’t think this is necessary in cars. In about 10 years, we are going to see vast improvements in power density and price and trying to squeeze power into body panels will not be cost effective. However, for maybe electric airplanes, this might be a pretty good idea. A wing and fuselage have a lot of surface area and you need as much power density as possible in airplanes.

Yeah, for planes, buildings, and boats this might make sense. For cars it’s just a ridiculous idea due to safety and damage-avoidance concerns. And cost – that wee little obstacle.

Why buildings? Seems about the worst possible application…

I don’t know about buildings but you can put a few layers of anode/cathode this under a solar panel and have a solar panel that will output power 24×7 or on demand.

I thought about this at one point; but concluded that the complexity of manufacturing this, and the extra electronics needed in every panel, would make this much more expensive than just adding dedicated battery packs to the installation…

Electronics is cheap! and if a company can build batteries and solar panels, electronics is nothing. I have a 50w panel hooked up to a sealed lead acid battery that runs 24×7 to power my home security system. 50w panel was about $100, battery about $50 and charge controller $20 for my alarm system… works great. The problem will still be the cost of the battery. I don’t think this will be feasable till there is a good solid state, thermally stable lithium battery.

The point is that having the electronics and batteries in every single panel is more expensive than having them in a central place.

(Also, it’s not generally true that “electronics is cheap”. It depends a lot on the specific parts. Some electronics are very expensive.)

I think it is worth exploring alternatives to what is perceived as a status quo/industry norm.
As you say, it might have uses in Aviation.

This would be great, and if they can also be 3D printed?……..

I have an alternate headline to suggest, “What If Pigs Could Fly?”

This concept certainly looks like something worthy of experimentation, but I have my doubts that we will ever see it in a mass produced car. BMW apparently didn’t find its attempt to use a carbon fiber body in the i3 to be a success, since they are not expanding that to other models.

A lack of cooling system will only work if the batteries have an extremely low resistance, so don’t generate significant amounts of heat when charged rapidly.

* * * * *

@Giles:

Solid-state batteries, at least in their first generation, are not going to be a cure-all for all the limitations of EV batteries. Switching from liquid or semi-liquid electrolyte to a solid electrolyte isn’t going to drop the internal resistance to zero. That would require superconductors.

This is such stupid idea that it shouldn’t be put anywhere online, certainly not at serious EV news site.

More to the point would be solar panels built and shaped into the body work as new flexible materials come on the market, but it’s a neat idea with new materials coming along you never know what’s around the corner.

Regarding this phrase in the article, “Tesla pioneered the “skateboard” approach”.

Wrong!

From first link below — “Unveiled at the 2002 Detroit auto show, it was supposed to be GM’s radical vision for a truly futuristic car. Freed from the tyranny of the internal combustion engine, GM was going to revamp the entire automotive paradigm with this, it’s most audacious concept car ever. Behold, the billion-dollar Skateboard!”

From second link below — “I regularly run into Borroni-Bird at conferences on connected and autonomous vehicles including a recent event I attended in Silicon Valley and a few days later I sat down with him over a cup of coffee to discuss the birth of the skateboard chassis of which he and his team at GM R&D can reasonably be called the creators.”

http://www.autoblog.com/2010/09/24/forgotten-concept-2002-gm-autonomy/

http://www.forbes.com/sites/samabuelsamid/2016/05/23/the-father-of-the-skateboard-chassis-dr-chris-borroni-bird/#43706c67b301

Well Tesla certainly pioneered USING a skateboard chassis in a production car(s).

And of course many other improvements like OTA software updates for a car.

Thank You for the links. I remember reading about that GM Skateboard when i used to subscribe to a few car magazines before internet. I thought this or maybe another article was back in mid to late 1990’s. First time I saw the Tesla Model S platform I immediately thought of the GM Skateboard. Anyways, this was GM at it’s best… No more.

Yes!!!!
Let’s put battery that can ccatastrophically fail all around passengers. Less cook them evenly. Why would we be satisfied with letting them walk away from a crash /s

Idiots who thought it must be PR masterminds if they secured funding fit this criminally incompetent idea.