The Heart of the Car
A battery box is an enclosed assembly in a solar car that houses the car’s batteries and other battery adjacent components. This includes not only the main battery packs themselves, but also battery controllers, fuses, cooling systems, auxiliary batteries, and more. As it is the source of the car’s energy, a well engineered battery box is integral to a successful solar car.
Battery boxes are heavily regulated in the American Solar Challenge, and for good reason. With cars like ours having around 400 individual battery cells, there is a lot of potential for disaster if proper precautions aren’t taken. This makes the battery box an interesting engineering problem to solve with numerous overlapping systems, rules, and constraints to take into account.
Our current battery box design looks fairly simple but is the result of many rounds of iterations and restructures. Our main struggles in the design process so far have been in securement, both of the internal components to the box and of the box to the chassis. Due to the American Solar Challenge’s impounding regulations, the battery box has to be routinely removable which means that the battery box cannot be permanently secured to the chassis. Our solution to this issue has been to utilize a plywood board as our base that extends beyond the dimensions of the box with holes for bolts to secure the box to eight L-brackets welded onto the chassis. These L-brackets will also have nuts welded onto their underside to make the cumbersome removal process a little easier. Our internal components have also been an issue as most do not have built in attachment points. This has required us to create housings for each component so that they are secured in all directions. We have solved this issue by designing thin strips of sheet metal that can be bent to the shape of each component and bolted into the box’s base. This provides a simple and easily fabricatable solution that is also strong enough to withstand any potential forces in the event of a collision.
Current electrical challenges include the layout of the batteries within the box that provided optimal cooling and space efficiency. Our current idea is to use 4x4 battery packs with 18650 Lithium-Ion batteries, with each pack having space to bolt the pack to the battery box. This allows for space efficiency, batteries secured from the turbulence of the car, and enough space between packs to allow for efficient cooling with a forced convection cooling system.
With the design phase of our battery box mostly complete, we are planning to begin fabrication starting in the fall quarter. We anticipate that the design of this phase will be complete by the end of the quarter and the system will be tested with the full battery setup by the end of winter quarter. This will be a collaboration between the mechanical team working on the design and the electrical team providing the specifications, with the time limiting factor being the time it takes for the parts to arrive, especially for electrical components.
