Compared to copper busbars aluminium offers a weight and cost save, but requires an increase in cross-sectional area of ~62%. Hence aluminium busbars need more volume for packaging. The highest conductivity is achieved by high purity aluminium (purity of 99.9 wt% Al and higher) in soft temper.
The current is an estimated continuous rating and plotted versus the cross-sectional area in mm 2. The gradient of the “straight line fit” shows that 5.9A/mm 2 is a rough estimate for copper busbar size. However, to be on the safe side of this I would initially size at 5A/mm 2 before doing the detailed electrothermal analysis.
Busbars are the main electrical connections between cells, modules and connect all of the HV system to the outlet connector. Normally made from copper or aluminium. Careful consideration needs to be taken: Electrical grade aluminum busbar material also known as ec grade aluminum busbar.
The maximum temperature obtained from the 2.5 mm Al busbar joint (i.e., 59.97 °C) is higher than the measured temperature from any of the Cu busbar joints. Therefore, the performance of copper busbar was better when Al was used as tabs. The performance of 0.3mm Cu [Ni] tab to Al and Cu busbar joints are plotted in Figure 6 c,d, respectively.
In this study, 0.3 mm Cu [Ni] and Al tabs were welded to 1.0 mm Cu and Al busbars, respectively, to identify satisfactory process parameters by varying welding pressure, welding time and amplitude of ultrasonic vibration. The process parameters and corresponding levels are given in Table 3.
For example, maximum temperatures obtained for the 0.3 mm Al tab to 1.5, 2.0 and 2.5 mm Al busbar joints were 80.27, 67.83 and 59.97 °C, respectively. In general, copper busbar-based joints were not heated as much as Al busbar-based joints due to higher thermal conductivity and lower resistance change.