## 4 Selected Measurement Test Results  
Two specimen number 1 and number 2 were tested, according to the method described above, in two measurement series at an ambient temperature of 25 \({}^{\circ}\)C \(\pm\) 5 \({}^{\circ}\)C. Initial measurements were taken at rated supply voltages and up to nominal charging/discharging currents. In the second stage, measurements with voltages and currents that were exceeding the predicted values were made to accelerate the occurrence of aging phenomena. The acceleration was applied due to the time consuming method of constant current charging/discharging at nominal parameters of supercapacitor (declared lifetime of more than 500,000 cycles at nominal values at 25 \({}^{\circ}\)C).  
For instance, Figure 8 illustrates the graph of maximum temperature increments (\(\Delta T_{Max}\)) on the observed surface of supercapacitor at rated capacitor values of \(U=2.7\) V, \(I=1400\) mA for which no changes in capacitor parameters were noted and the maximum test temperature was approximately \(\Delta T_{Max}=5\)\({}^{\circ}\)C.  
Second stage tests with overruns of nominal values have been presented in Figure 9 a thermogram for tests with voltage \(U=3.3\) V and current \(I=2800\) mA.  
Figure 8: Maximum temperature increments \(\Delta T_{Max}\) of supercapacitors at voltage \(U=2.7\) V and current \(I=1400\) mA (nominal conditions).  
Figure 9: Chart of maximum temperature increments \(\Delta T_{Max}\) change during test \(U=3.3\) V, \(I=2800\) mA.  
Simultaneously taken measurements of the characteristic parameters (C) and \(ESR\) shown in Figure 10 displayed no changes (Figure 10 for \(\sim\)450 cycles).  
Variations in characteristic values of tested supercapacitors were observed after around 700 cycles with the test parameters: \(U=3.6\) V, \(I=3200\) mA, as illustrated in Figure 11.  
Observed variations in capacity (C) and \(ESR\) were accompanied by an increase in maximum temperature increments (\(\Delta T_{Max}\)) which were increasing along with \(ESR\) increment, as shown in Figure 12.  
Figure 11: Chart presenting variation of capacity (C) and \(ESR\) during test \(U=3.6\) V, \(I=3200\) mA.  
Figure 10: Charts illustrating variation in capacity (C) and equivalent series resistance (\(ESR\)) values during test \(U=3.3\) V, \(I=2800\) mA.  
Figure 13 presents the temperature field distribution for the picture taken in 101 h of the test for the test at voltage \(U=3.6\) V and current \(I=3200\) mA.  
Figure 14 illustrates the results of the average temperature increments (\(\Delta T_{Ax}\)) of all the observed samples as a function of current, for which no changes in the capacities (C) and \(ESR\) occurred during the test. Changes in the values of maximum temperature increments (\(\Delta T_{Max}\)), as a function of currents, are demonstrated in Figure 15.  
Figure 14: Average surface temperature increments (\(\Delta T_{Ax}\)) of tested supercapacitors as a function of current.  
Figure 15: Maximum surface temperature increment (\(\Delta T_{Max}\)) of tested supercapacitor as a function of current.  
Figure 16 shows a graphical representation of the standard deviation \(\sigma\) obtained during the test of samples at the test values \(U=2.7\) V, \(I=500\) mA, and at the test values \(U=2.7\) V, \(I=1400\) mA.  
In addition, Figure 17 depicts the instantaneous values obtained for ancillary parameters (sum of temperatures \(\Sigma T\) and coefficient of variation \(CV\)) to illustrate the condition of the sample for the test value \(U=3.6\) V, \(I=3200\) mA, for which occurred changes in the determined parameters.