## 3 Results and Discussion  
The variation of voltage during discharge rates of 1C-4C is represented in Figure 3. It should be noted that all discharge rates end at the cut-off voltage corresponding to 2 V. Figure 3 depicts that both the nominal voltage and discharge time values diminish with increasing discharge rate. It can be understood from the figure that the operation voltage has a sharp decrease with the increment of current. Battery discharge durations are recorded as 3550, 1750, 1140 and 840 s for 1C, 2C, 3C and 4C, respectively. \begin{table}
\begin{tabular}{c c} \hline \hline
**Measured Parameter** & **Uncertainty** \\ \hline Ptloo & \(\pm\)0.1 \({}^{\circ}\)C \\ \hline Thermocouple & \(\pm\)1.0 \({}^{\circ}\)C \\ \hline Data acquisition system & \(\pm\)0.6 \({}^{\circ}\)C \\ \hline Flow meter & \(\pm\)1\% \\ \hline Power supply & \(\pm\)0.1\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Uncertainties for measured parameters. Figure 2: The schematic representation (**a**) and photo (**b**) of the established experimental setup. Figure 4 shows the effect of fluid type and immersion ratio on average battery surface temperature for various discharge rates, the cooling water temperature of 25 \({}^{\circ}\)C and flow rate of 1 L/min. The average battery surface temperature is determined by the estimation of the arithmetic mean of the ten temperatures. The results revealed that the average battery temperature rises during discharge, and this situation can be explained by an exothermic chemical reaction. The results showed that the average battery surface temperature could be kept in the desired temperature range (between 20 \({}^{\circ}\)C and 40 \({}^{\circ}\)C) with the use of distilled water for both 50% and 100% immersion. The air cooling is not sufficient, especially for 4C discharge rate. The highest average battery surface temperatures are 32 \({}^{\circ}\)C, 35.94 \({}^{\circ}\)C and 42.91 \({}^{\circ}\)C for 100% water immersion, 50% water immersion and air at the end of 4C discharge rate, respectively. The lowest average battery temperature result was obtained with the application of 100% water immersion because of the higher heat transfer performance of distilled water compared to air. The average battery surface temperature reduces by 13%, 19%, 28% and 25% with the applications of 100% water immersion compared to air for 1C, 2C, 3C and 4C, respectively. In addition, it can be seen that there is a sharp increase in average battery temperatures with higher discharge rates. Figure 5 demonstrates the variation of maximum battery surface temperatures with the depth of discharge for different fluid types, immersion ratios and various discharge rates, respectively. It can be revealed that there is nonhomogeneous temperature distribution on the battery surface during discharge, and it rises with an increment of discharge rate. According to Figure 5, the maximum battery surface temperatures are 33.32 \({}^{\circ}\)C, 42.28 \({}^{\circ}\)C and 45.61 \({}^{\circ}\)C for 100% water immersion, 50% water immersion and air at the end of 4C discharge rate, respectively. The maximum battery surface temperatures are observed for the positions of T\({}_{1}\), T\({}_{2}\) and T\({}_{1}\) for 100% water immersion, 50% water immersion and air at the end of discharge. It should be noted that the maximum temperatures are observed in the location near the tabs. It can be concluded that the 100% immersion technique can keep battery temperature in the desired range for all considered discharge rates, whereas the other techniques are only appropriate for lower discharge rates (1-2C). Temperature curves depict that the maximum temperature of the battery is significantly affected by immersion since half of the test section is filled with distilled water. Moreover, this situation can also be observed at the minimum temperatures, and the results are given in Table 3.  
Figure 3: The variation of voltage with time for different discharge rates. Figure 4: _Cont_.