**5. Experimental Validation**

As we know from the previous section, the optimal arrangemen<sup>t</sup> of the inlet and outlet in the one-in-one-out model is scheme 13, and the optimal arrangemen<sup>t</sup> of the inlet and outlet in the one-in-two-out mode is scheme 24. This is because, under these two configurations, the fluid flow state in the battery pack is most suitable for dissipating the heat in the battery pack, which can result in good heat dissipation of the battery system when working. However, the simulation results need to be verified by experiments. Therefore, discharge tests were conducted on scheme 13 and scheme 24. The 20 batteries are arranged in a 4 × 5 arrangemen<sup>t</sup> and connected in a series of four and a parallel of five. To ensure a constant discharge current of 2 A, the discharge current of 8 A was set to constantly discharge for 15 min. In the experiment, the temperature of 20 batteries was collected in real-time, and a temperature sensor was installed on the side of each battery. The experimental set up is shown in Figure 3.

The temperature data of two battery packs were collected in the experiment. The temperature at the end of discharge (i.e., the MaxT of the battery) was marked on the single battery according to the battery layout in the experiment. The results are shown in Figures 22 and 23, respectively. Under the premise of good enough performance of the BTMS, lower cost should also be a focus. The transient change process in the temperature cloud map is shown in Figures 24 and 25.

**Figure 22.** Comparison between the simulation and experimental results for scheme 13 (simulation on the left and experiment on the right).

**Figure 23.** Comparison between the simulation and experimental results for scheme 24 (simulation on the left and experiment on the right).

Figures 22 and 23 show the comparison of the battery temperature during the simulation and the experiment. In Figure 22, the error in MaxT between the simulation and experiment is 0.017% and in Figure 23, the error in MaxT between the simulation and experiment is 0.049%. The experimental results are close to the simulation temperature. Battery temperature is generally lower near the inlet, and the temperature starts to rise as the distance from the inlet increases. High-temperatures appear near the outlet, and the closer they are to the outlet, the higher the temperature. These phenomena are consistent with the basic predictions of heat transfer. However, the experimental results are still inconsistent with the simulation results. At the end of discharge, the battery temperature is still slightly lower than the simulation results. In addition, the influence of pressure on the temperature field was not considered in this study, which is a possible cause of temperature error. Table 2 shows a comparison of the air speed in the simulation and the experiment. Limited by the difficulty of adjustment and measurement accuracy, the forced air speed at the inlet can only be adjusted close to 1 m/s. The error in the simulation and experiment stabilized at less than 15.38%.

**Figure 24.** A temperature field change in scheme 13 in the dying minutes.

**Figure 25.** A temperature field change in scheme 24 in the dying minutes.

**Table 2.** Comparison of the air speed at the inlet and outlet in the simulation and the experiment.

