# Application of Infrared Thermography in E-Bike Battery Pack Detail Analysis--Case Study
## 4 Battery Pack Revitalization, Results, and Discussion  
### Revival and Optimization of Battery Assembly  
In order to preserve the e-bike function by revitalizing its battery pack, we decided to use the batteries from Figure 16c (used laptop battery cells) to assemble the new functional pack. The availability of such cells is a rather limiting factor for making a proper selection, and in case of a larger quantity, it is necessary to check all the cells and choose the best performing [48]. Due to the different cells, which are not designed for the currents expected from e-bike batteries, it was decided to lower the discharge current by 20% to obtain more accurate capacity values. Table 5 shows cells' charge states and cells' capacities after discharging all cells with current of 1.8 A. The higher cell resistance values are the result of oxidation of the contacts [42]. The reused cells 21 and 14 show a higher capacity due to the lower discharge current and the slight overcharge, which can be seen from the voltage value before the discharge begins. The overcharge is the result of using a simple charger to shorten the charging time.  
After an optimal structure of the 2p10s pack was determined, the new pack parameter assessment was conducted, Table 6. As is shown in Figure 23, a repaired battery pack now  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & & & \multicolumn{3}{c}{**10s**} & & \\ \hline  & 1049 & 831 & 520 & 262 & 565 & 271 & 414 & 277 & 310 & 340 \\  & 68 & 92 & 146 & 226 & 115 & 211 & 162 & 205 & 189 & 167 \\  & 74 & 94 & 156 & 230 & 121 & 218 & 163 & 207 & 193 & 174 \\  & 84 & 105 & 160 & 246 & 141 & 221 & 165 & 207 & 203 & 187 \\ \hline
**sum** (mAh) & **1275** & **1122** & **982** & **964** & **942** & **921** & **904** & **896** & **895** & **868** \\ \hline \(\Delta\) to avg.(mAh) & 298 & 145 & 5 & \(-13\) & \(-35\) & \(-56\) & \(-73\) & \(-81\) & \(-82\) & \(-109\) \\ \% & 30.51 & 14.85 & 0.52 & \(-1.32\) & \(-3.57\) & \(-5.72\) & \(-7.46\) & \(-8.28\) & \(-8.38\) & \(-11.15\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Optimal layout of pack compound in 4p10s configuration arranged from the existing cells regarding cell capacities (mAh).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Cell No.**} & **Start** & **Cell** & **Cell** & **Discharge** & **End** & **Charge** \\  & **Voltage** & **Resistance** & **Capacity** & **Time** & **Voltage** & **Time** \\  & **\(\mathbf{U_{s}}\) (V)** & **\(\mathbf{R}\) (m/\(\mathbf{\Omega}\))** & **(mAh)** & **\(\mathbf{t_{d}}\)** & **\(\mathbf{U_{e}}\) (V)** & **\(\mathbf{t_{c}}\) (min)** \\ \hline
41 & 4.22 & 189 & 2283 & 1 h 15 m & 3.60 & 16 \\
42 & 4  
has 35% of the capacity of a new one. However, it still has three times the capacity of a pack that has reached its end of service, when it has only 11% of the initial capacity and two defective cells in a pack assembly. In addition to Figure 23, there is a thermogram that monitors the equilibrium of the items during the initial fill that shows a fairly uniform thermal load on all cells. Such uniform distribution of the thermal load across the cells in the pack is a strong indicator that the battery pack is now recovered to some degree, as determined by the characteristics of the cells used.