## 5 Results and Discussion
### Sensitivity Analysis with Coolant Flow Rate and Ambient Temperature  
Extending from the base case, where the coolant flow rate is 10 L/min and the ambient temperature is 35 \({}^{\circ}\)C, two sets of sensitivity analyses are further conducted. In the first set, the ambient temperature is kept constant at 35 \({}^{\circ}\)C, while the coolant flow rate is increased from 10 L/min to 20 L/min and 30 L/min, respectively, and the results are shown in Figure 13. In the second set, the coolant flow rate is maintained at 10 L/min, while the  
Figure 12: Cell-level thermal performances of the serial and parallel module designs. **(a)** Temperature at middle of riding, **(b)** SOC at middle of riding, **(c)** OCV at middle of riding, **(d)** SOP at middle of riding, **(e)** temperature at end of riding, **(f)** SOC at end of riding, **(g)** OCV at end of riding, and **(h)** SOP at end of riding. ambient temperature is decreased from 35 \({}^{\circ}\)C to 20 \({}^{\circ}\)C and 5 \({}^{\circ}\)C, respectively, and these results at the end of riding are displayed in Figure 14.  
Figure 13a-c show the variation in component temperatures as the flow rate increases. It can be observed that a higher flow rate leads to lower temperatures for the battery, inverter, and motor, but for either the serial or the parallel design, the extent of temperature reduction lessens with increasing flow rate. Another phenomenon is that, with the increase in coolant flow rate, the gap between the serial and parallel designs expands. Comparing the serial and parallel designs, the serial design results in lower battery temperatures but higher temperatures for the inverter and motor, which is consistent with the findings in the base case. Figure 13d illustrates that a higher flow rate leads to higher overall cooling system efficiency, but as the flow rate increases, the rate of efficiency improvement slows down. Additionally, the serial design exhibits higher efficiency compared to the parallel design. Figure 13e-h show the variations in temperature, SOC, OCV, and SOP among cells with respect to the coolant flow rate. It can be observed that an increase in flow rate reduces the performance variations among cells, and this holds true for both the serial and parallel designs. Compared to the serial design, the parallel design can lead to smaller cell-to-cell variations, but as the flow rate increases, the gap between the two designs becomes significantly smaller. With increased coolant flow rates, the serial design emerges as the superior choice for battery thermal management. It not only maintains a lower average temperature but also narrows the temperature differential between cells to approximately  
Figure 13: Performances of the serial and parallel module designs with coolant flow rate. (**a**) Battery maximum temperature, (**b**) Inverter maximum temperature, (**c**) Motor maximum temperature, (**d**) Cooling system efficiency, (**e**) Maximum temperature difference between cells, (**f**) Maximum SOC difference between cells, (**g**) Maximum OCV difference between cells, and (**h**) Maximum SOP difference between cells. 2 \({}^{\circ}\)C from a previous 4.5 \({}^{\circ}\)C. This improvement underscores the serial design's efficacy in scenarios where overall cooling is imperative, such as in high ambient temperature conditions. Figure 14a-d illustrate the variations in battery temperature, inverter temperature, motor temperature, and cooling system efficiency with changes in ambient temperature. As expected, the temperatures of these components and the cooling system efficiency increase with the rise in ambient temperature, showing an approximately linear relationship. Similar to the observations in Figure 13, the serial design results in lower battery temperatures at the expense of higher inverter and motor temperatures. Figure 14e-h show the trends of cell-to-cell variations with changes in ambient temperature.