In what may revolutionize the way electric vehicles (EVs) are made, Tesla CEO Elon Musk announced yesterday a “profound” change to the design of their battery packs and how they integrate with the car.
During his presentation at Battery Day, Musk compared the change to how airplanes used to carry the fuel tanks as cargo. As technology progressed, fuel tanks were then made into a wing shape, and bolted to the structure of the wing. Eventually a more efficient method was realized by turning the wings themselves into the fuel tanks.
Tesla is now taking the same principle and turning the battery pack into a structural element of the car, giving it a use as more than just a fuel source.
“All modern airplanes, the fuel tank, your wing is just a fuel tank and wing shaped. This is absolutely the way to do it. And then the fuel tank serves as dual structure, and it’s no longer cargo. It’s fundamental to the structure of the aircraft. This was a major breakthrough. We’re doing the same for cars.”
By creating a battery pack that becomes part of the car’s structure, a number of benefits will be realized. One of these is reduced weight. This is achieved by removing intermediate structures that are no longer needed like supports and stabilizers within the battery pack (the red parts in the image below). Less weight then equals more range.
This change also makes the car much safer. By integrating the battery pack, the structure of the vehicle becomes much stiffer. Musk pointed out that even a convertible car with this design would be stiffer than a regular car.
Another advantage of a structural battery pack is that the individual cells are brought closer to the center of the vehicle. This reduces the probability of a side impact impacting the cells, making it a safer design overall. Not only does it make it safer, but it also improves the handling of the car by reducing the “polar moment of inertia”.
The analogy Musk gave to understand this change is how ice skaters keep their arms close to their body to increase the speed of their rotation. With cells closer to the center, the car will handle and manoeuvre better.
A big change that will allow them to do this is making the manufacturing of the vehicle much easier. You have probably heard of the new Giga Press machines being installed at the Fremont factory and Giga Shanghai which will create single piece castings for the rear of the Model Y. This process requires 79 fewer parts per car to manufacture.