## 3 Experimental Results
### Effect of Vibration on DC Resistance  
The DC resistance distribution before and after the vibration test are presented in Tables 2 and 3, respectively. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Test Condition** & \multicolumn{6}{c}{**DC Internal Resistance**} \\ \hline  & 38.03 & 39.47 & 39.07 & 39.67 & 37.40 & 38.47 & 38.00 \\  & 36.80 & 36.60 & 36.37 & 38.23 & 37.40 & 37.83 & 36.80 \\ Pre-Test & 37.40 & 37.12 & 36.73 & 36.92 & 36.16 & 36.64 & 36.79 \\  & 36.23 & 34.93 & 37.56 & 37.27 & 36.66 & 36.67 & 37.61 \\  & 36.10 & 36.52 & 35.69 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: DC resistance distribution before vibration test (m\(\Omega\)). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Test Condition** & \multicolumn{6}{c}{**DC Internal Resistance**} \\ \hline  & 37.63 & 38.87 & 38.67 & 38.63 & 37.40 & 38.43 & 38.03 \\  & 35.57 & 37.83 & 37.20 & 38.43 & 37.83 & 38.87 & 37.20 \\ Post-Test & 38.03 & 38.23 & 37.60 & 38.83 & 36.60 & 37.43 & 37.63 \\  & 36.57 & 36.17 & 39.20 & 42.44 & 38.72 & 38.52 & 40.09 \\  & 38.43 & 38.50 & 37.13 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: DC resistance distribution after vibration test (m\(\Omega\)). Figure 9: The distribution function and theoretical normal distribution function of the capacity samples after vibration. According to existing studies, the effect of vibration on the electrical performance of the battery is weak. Therefore, the conclusion that vibration has no effect on the electrical properties cannot be made, even if the electric performance does not change significantly before and after vibration. The statistical knowledge must be used to study how the electrical properties change. As can be seen from Tables 2 and 3 and Figure 10, some cells exhibit an increase in internal resistance while others exhibit a decrease after the vibration test simply on the perspective of the single cell; therefore, there are no consistent conclusions to be reached on this problem as to whether the vibration and the mechanical loading lead to an increase or a decrease in the internal resistance. However, from another point of view, it also can be seen that, on the whole, there is an increasing trend in internal resistance, where 26 out of 32 cells which exhibit an increase in the internal resistance occupy most of the sample, while just 6 out of 32 cells exhibit a slight decrease. Therefore, in order to eliminate the influence of the measurement uncertainty and other accidental factors which may lead to an illusion of a decreasing trend, the mathematical statistical analysis is adopted to excavate a more reasonable conclusion. In order to identify whether there is an increasing trend that relates to the impact of vibration on the cell resistance, this paper adopts the method of hypothesis testing to give reasonable assumptions. Based on the sample distribution of the internal resistance before and after the vibration test, a decision regarding the acceptance or rejection of the null hypothesis is made under a certain significant level \(\alpha\). In general, the null hypothesis is the hypothesis that the researcher wants to collect the evidence to object to, which is expressed usually as \(H_{0}\). The alternative hypothesis is the hypothesis that the researcher wants to collect evidence to support this, which is expressed as \(H_{1}\). Therefore, in this paper, the null hypothesis is \(\mu\leq\mu_{0}\) where \(\mu\) represents the internal resistance mean of samples before vibration testing and \(\mu_{0}\) represents the internal resistance mean of samples after vibration testing. Consequently, the alternative hypothesis is \(\mu>\mu_{0}\). If a decision to reject the null hypothesis is made under a certain significant level \(\alpha=0.05\), it would show that there is a probability of 95% that the sample mean after the vibration test is greater than the sample mean before the vibration test. In other words, there are good reasons to believe it is vibration which leads to an increase in the internal resistance.