Over the past few weeks, the electrical team has been working towards completing the solar car’s battery cell array. With the lithium-ion batteries arriving, it has been time to design the battery holders. As opposed to last year, this year’s battery holders have been integrated with polycarbonate in one unit. Due to extensive iterations and changes to the holder’s dimensions, the new battery holder’s design has been an extended process.
When initially designing the lithium-ion battery holders, the diameters of the batteries’ surfaces were heavily considered. After cutting a prototype of possible hole diameters for the batteries, we determined that the best fit for the surfaces and ends of the batteries was 18.4 millimeters. Knowing this and the needed distance between each battery, we were able to design a sample holder with the new dimensions.
Once the sample was designed, we found that the batteries fit snugly in place. Building on this, e created a set of new holes in the design between each battery cell hole. Room was also made for fiberglass supports to potentially be placed through the two layers of the battery holder. This would allow for extra support between the battery cells. Similar to before, we tested multiple hole sizes for the supports, finding that a diameter of 3 millimeters kept the supports firmly in place.
With the dimensions of both the space between battery cells and the diameters of the holes to be cut, we began to focus on the sides of each battery holder layer. The battery holder was designed with two layers. Both would have short flaps on each side of the battery cell array. These flaps would fold downwards. Once each end of the battery holder was placed together, the flaps of each would overlap and form an open-ended box.
While this design offered additional support to the battery cells, the flaps would prevent necessary access to the cells from the side. Because of this, we decided to use two layers of the battery holder without the flaps to fold down.
As soon as all of the dimensions of the battery cell holders were tested and decided upon, we cut the final battery cell array using the arrangement previously chosen (15 battery cells in parallel and 30 cells in series). With the battery cell holders cut, the team can continue to work towards completing the battery.