Effect of Busbar Design on the Thermal Performance of Battery Packs

Li-ion batteries face challenges that are not usually present with other chemistries is cell balancing. If a high imbalance occurs within a parallel circuit, possibly because of poor cell - grading or due to temperature localization, the adjacent cells will charge the unbalanced cell and it may be possible that the imbalance never completely fades away and the other cells also end up unbalanced. One of the key solutions to maintaining cell balance is to ensure that all cells within a battery pack are kept at a uniform temperature. This requires careful thermal management, which can be achieved through a combination of conduction and convection circuits. In this paper, a 1D-3D simulation study has been performed on a 12V 4s-4p pack by varying the thickness of HV busbars and temperature localization effects and temperature uniformity has been observed. The holder has 16 cells with a 4×4 grid pattern, each cell has a diameter of 18 mm and a length of 65 mm. The cells are connected in series using nickel busbars using a thickness of 0.25 mm and width of 28 mm which runs along the top and bottom of the cells. Cells are connected to HV busbars at the ends of cell grids. The HV busbars are 0.25 mm in thickness and 180 mm in length under natural convection environment and for variations. A pure copper strip has been used at different locations in other variations on nickel busbars to observe the effect of temperature localization. The output temperature contours under various loadings have been studied and the temperature of each cell in the matrix has been plotted to observe the variation and non-uniformity of temperature among cells for different busbar thicknesses.