At first, electric vehicles were no more than conventional vehicles with the conventional powertrain replaced by an electric one, but this isn’t a very efficient way of doing things.
In fact, the electric vehicle is evolving quite like the conventional vehicle has evolved over the last hundred years. For example, conventional vehicles were built with a passenger cabin mounted to a frame, to which everything else was attached. Engineers eventually started using the passenger cabin itself as a structural component which, among other things, enabled vehicles to become lighter and more fuel efficient.
As I mentioned, the first electric vehicles essentially added electric powertrain components, such as battery packs and electric motors, to a conventional body, but what if we applied the same evolutionary steps to electric vehicles that conventional vehicles went through? Tesla Motors’ first attempt at an electric vehicle could be analogous to the cabin-on-frame model, replacing the Lotus Elise conventional powertrain with a Tesla Motors electric powertrain. The Tesla Model S could be analogous to the switch to unibody construction, using the large lithium-ion battery pack as the underbody of the vehicle.
Eliminating frame parts and using a structural battery enabled Tesla Motors to reduce overall weight and increase rigidity, as well as improve vehicle dynamics by keeping the center of gravity near the ground. The Tesla Model S is also the class-leader in available range, up to 300mi in the 85kWh Performance version. Tesla Motors isn’t the only one investigating structural electric vehicle batteries. We covered Volvo Car Group in their research and development of supercapacitor-embedded body panels, which saves weight by eliminating heavy sealed lead-acid batteries, improving fuel efficiency.
As battery technology advances and lightweight materials are utilized more, it won’t be long before we see more structural-battery designs in hybrid and electric vehicles. As Volvo put it, reducing weight starts a spiral of increasing fuel economy. Lighter weight requires less suspension weight and less motor to haul that weight, resulting in climbing fuel economy.