## 5 Experiment
### Experiment on a Vehicle  
The previous simulation and bench tests were performed for the quantitative analysis at a constant heating power and a stable coolant temperature and cooling flow. In order to observe the battery pack temperature trends when these boundary conditions change dynamically, the battery pack was tested on a hybrid SUV. This experiment was carried out by driving 30 km (about 1.2 h in the summer) when the ambient temperature was 33 \({}^{\circ}\)C\(\sim\)39 \({}^{\circ}\)C. The vehicle speed and battery current curve are shown in Figure 16a. The maximum charging current was about 79.6 A, while the maximum discharging current was about \(-\)127.8 A. The root mean square current, including charging and discharging, was 26.5 A during the whole testing process. The cooling flow varied between 5 and 10 L/min, and the inlet temperature was dynamically adjusted between 25 and \(-\)30\({}^{\circ}\)C.  
The temperature test positions in the battery pack were determined according to the results of the bench test, covering the highest and lowest temperature points. The temperature and temperature difference curves are shown in Figure 16b. At the beginning of the test, the maximum temperature of the battery pack was 41.3 \({}^{\circ}\)C. After the cooling system was turned on, the battery temperature dropped rapidly and eventually stabilized at around 39.3 \({}^{\circ}\)C. During the test, the temperature difference of the battery pack was 2.87 \({}^{\circ}\)C at first; then, the temperature difference gradually became larger,  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Test**} & \multicolumn{3}{c}{**Boundary Conditions**} & \multicolumn{3}{c}{**Simulation**} & \multirow{2}{*}{**Experiment**} \\ \cline{2-2} \cline{6-7}  & **I\({}_{\text{rms}}\)** & & & **T\({}_{\text{inlet}}\)** & & **Q** & **T\({}_{\text{max}}\)** & **T\({}_{\text{diff}}\)** & **T\({}_{\text{max}}\)** \\  & **(A)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **T\({}_{\text{diff}}\)** **(\({}^{\circ}\)C)** & \\ \hline \(1\)\({}^{1}\) & & 25 & 5 & 37.6 & 3.0 & 38.7 & 3.0 & Pass \\ \(2\) & 25 & 25 & 10 & 36.8 & 2.8 & 38.3 & 2.9 & Pass \\ \(3\) & & 30 & 5 & 41.1 & 2.7 & 42.3 & 2.6 & Pass \\ \(4\) & & 30 & 10 & 40.2 & 2.1 & 41.3 & 2.4 & Pass \\ \hline \(5\) & & 25 & 5 & 40.4 & 3.5 & 41.3 & 3.2 & Pass \\ \(6\) & & 25 & 10 & 40.2 & 2.9 & 41.1 & 2.8 & Pass \\ \(7\) & & 30 & 5 & 43.9 & 3.1 & 45.1 & 2.9 & Pass \\ \(8\) & & 30 & 10 & 43.2 & 2.5 & 44.8 & 2.7 & Pass \\ \hline \(9\) & 35 & 25 & 10 & 45.3 & 3.9 & 46.3 & 4.1 & Fail \\ \(10\) & & 30 & 10 & 48.6 & 4.0 & 49.7 & 3.8 & Fail \\ \hline \hline \end{tabular}  
* The process and results of the NO.1 experiments are described in detail as examples.  
\end{table}
Table 6: Comparison of the experimental results and numerical results.  
Figure 16: Test conditions and test results of the temperature on vehicles: (**a**) road spectrum, transient current spectrum, and RMS current over ten minutes; (**b**) ambient temperature inside the battery pack temperature trends from six sensors, and temperature difference curves.  
but eventually stabilized at 4 \({}^{\circ}\)C. This result shows that the maximum temperature and temperature difference of the whole battery pack were effectively controlled.