Not only does their weight soak up power that would otherwise be used to move the car around, but their physical size often necessitates a dramatic reduction in boot capacity or compromised interior packaging.
Just look at the Holden Volt, for example. The large centre tunnel needed to accommodate its T-shaped battery pack means it's strictly a four-seater, despite having an interior large enough for five.
But Swedish automaker Volvo reckons it's got a solution. The company's research and development boffins have teamed up with the Imperial College London to sandwich energy storage materials into the very body panels that make up a car's external skin.
By sandwiching supercapacitive material between carbon fibre sheets, the research team effectively created a relatively thin body panel that also doubles as an energy storage device - simultaneously saving weight and freeing up room inside the car.
The weight savings are substantial too.
By replacing the standard steel bootlid of an S80 with the prototype carbon fibre battery body panel, Volvo was able to create a part that was not only capable of storing power from a regenerative braking system or mains oultet, but one that was also lighter than the part it replaced.
Overall, Volvo reckons that a vehicle's weight could be reduced by upwards of 15 percent by employing this technology.
It's ideally suited to large, broad pieces of bodywork like the roof, doors, bootlid and bonnet, however the technology is still strictly in a prototype stage. Don't expect a production debut any time soon.
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