# Application of Infrared Thermography in E-Bike Battery Pack Detail Analysis--Case Study
## 3 Analysis and Diagnostics of the Battery Pack
### Battery Cells Electric Parameters and Functional Analysis
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Cell No.**} & **Resistance** & **Capacity** & **Group** & **Remaining** & **Cell** & **Charge** \\  & **R (m/l)** & **C (mAh)** & **Capacity** & **Capacity** & **Voltage** & **Time** \\  & & & **(mAh)** & **(mAh)** & **(mAh)** & **_U (V)_ & **(min)** \\ \hline
1 & 113 & 115 & 937 & 5.11 & 4.140 & 16 \\
2 & 101 & 340 & & 15.11 & 4.120 & 34 \\
3 & 109 & 277 & & 12.31 & 4.120 & 26 \\
4 & 101 & 205 & & 9.11 & 4.100 & 23 \\ \hline
5 & 101 & 174 & 737 & 7.73 & 4.090 & 20 \\
6 & 101 & 189 & & 8.40 & 4.120 & 23 \\
7 & 103 & 156 & & 6.93 & 4.100 & 18 \\
8 & 106 & 218 & & 9.69 & 4.130 & 27 \\ \hline
9 & 101 & 207 & 668 & 9.20 & 4.190 & 23 \\
10 & 98 & 226 & & 10.04 & 4.140 & 25 \\
11 & 117 & 68 & & 3.02 & 4.140 & 9 \\
12 & 111 & 167 & & 7.42 & 4.120 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Battery pack cells parameter values during 1 A charge. Figure 18: Spatial distribution of TOP/upper- (**a**) and BOT/lower-layer (**b**) pack cells capacities. Figure 17: Comparison of discharge (**a**) and charge (**b**) current–voltage (C-V) characteristics of best performing cell, cell No. 21. The results in Table 3, a charge-based capacity assessment approach, validate and confirm the results of the cell capacity determination method that utilized the _discharging_ approach. Finally, a charge-based approach yielded similar visually representative cell spatial mapping for both pack assembly layers (TOP and BOT), as shown in Figure 19.  
The results support the confirmation of the poor pack assembly state and cells degradation determined by the discharging method. The comparison of cells capacities, determined with the charging and discharging method, shows a capacity deviation in accordance with the expectation [41; 44], as presented in Figure 20. A cell parameters degradation was expected [45; 46], but in the case of the analyzed battery pack, it occurred rather quickly. Figure 19: TOP/Upper- (**a**) and BOT/lower-layer (**b**) cell capacities determined with 1 A cells charging method. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Cell No.** & \begin{tabular}{c} **Resistance** \\ \(R\) **(mT)** \\ \end{tabular} & \begin{tabular}{c} **Capacity** \\ \(C\) **(mAh)** \\ \end{tabular} & \begin{tabular}{c} **Group** \\ **Capacity** \\ **(mAh)** \\ \end{tabular} & \begin{tabular}{c} **Remaining** \\ **Capacity** \\ **(mAh)** \\ \end{tabular} & \
\begin{tabular}{c} **Cell** \\ **Voltage** \\ **(mAh)** \\ \end{tabular} &
\begin{tabular}{c} **Charge** \\ **Voltage** \\ **(mAh)** \\ \end{tabular} \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._The visualization of the spatial capacity distribution within the battery pack as well as the corresponding temperature distribution are shown in Figures 21 and 22. Unlike the previously presented thermograms, we decided to export the radiometric data to a more readable and convenient form for a further analysis--a CSV file--and to display it in a different form by processing in a basic spreadsheet tool. Figures 21 and 22 clearly depict that the thermal distribution pattern and cell state of capacity cannot be correlated. The reason is in the inertia of the thermal process [47] and in the balancing dynamics shown in Figure 12. Among all the cells in the analyzed battery pack, only two can be used to make a new package--cells 14 and 21. Attempting to assemble a battery from these cells would be pointless, as none of the parallel cells would be able to match the capacity of a healthy cell, Table 4.  
Figure 21: Comparison of (**a**) TOP layer capacity distribution in (mAh) and (**b**) measured temperature values in (°C). Figure 20: Comparison of cells capacities determined with the charging and discharging method.