A method to quickly obtain the capacity of all single cells in the battery pack
A technology for single cells and battery packs, which can be used in measuring electrical variables, measuring electricity, measuring devices, etc., and can solve problems such as difficulty in application
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example 1
[0044] The target lithium-ion battery is CATL's lithium iron phosphate battery, with a nominal capacity of Cap initial =180Ah, the battery reference curve data uses the SOC-OCV relationship curve data, and the data interval is ΔSOC=2%. The capacity value corresponding to each OCV point is calculated by the formula: Q=SOC*180;
[0045] Use the five-point cubic smoothing filter method (by selecting 2 data before and after the position to be smoothed, a total of 5 data, using a third-order polynomial for fitting, and calculating the value after smoothing) to obtain the SOC-OCV relationship data The capacity increment curve of the obtained capacity increment curve is as follows figure 2 As shown by the dotted line in dQ / dV, figure 2 Take SOC as the abscissa, the left ordinate is the open circuit voltage OCV of the battery, the right ordinate is dQ / dV, and the position of the first eigenvalue is figure 2 In the position of point A, the corresponding SOC is 55.6%, and the capa...
example 2
[0055] The target lithium-ion battery is Lishen 21700 ternary battery with a nominal capacity of Cap initial =4.5Ah, the battery reference curve data uses the SOC-OCV relationship curve data, and the data interval is ΔSOC=3%. The capacity value corresponding to each OCV point is calculated by the formula: Q=SOC*4.5;
[0056] The capacity increment curve and d 2 Q / dV 2 curve, the obtained capacity increment curve is as follows Figure 4 dQ / dV dotted line in dQ / dV, d 2 Q / dV 2 curve like Figure 4 As shown by the dotted line, Figure 4 The abscissa is the open circuit voltage OCV, the left ordinate is the battery SOC, the first right ordinate is dQ / dV, and the second right ordinate is d 2 Q / dV 2 , the position of the first eigenvalue in the figure is Figure 4 The position of point E in the corresponding SOC value is 39.8%, and the capacity Q 1 =1.791Ah, the position of the second eigenvalue in the figure is Figure 4 Point F in the position, the corresponding SOC valu...
example 3
[0065] The target lithium-ion battery is Guoxuan Hi-Tech's soft-pack ternary battery, 15Ah in parallel and then connected in series, with a nominal capacity of Cap initial =30Ah, the battery reference curve data uses historical curve data, the charging current is 6A, and the data extraction condition is ΔV≥5mV;
[0066] The capacity incremental curve and d 2 Q / dV 2 The curve, with the charging voltage as the abscissa, the left ordinate is the battery SOC, the first right ordinate is dQ / dV, and the second right ordinate is d 2 Q / dV 2 , get the charging capacity Q' corresponding to the first eigenvalue position 1 =16.53Ah, the charging capacity Q' corresponding to the second eigenvalue position 2 =26.13Ah;
[0067] Calculate the relationship coefficient between the capacity and the total capacity of the battery characteristic values:
[0068] g=ΔQ / Cap initial =|Q' 2 -Q' 1 | / Cap initial =(26.13-16.53) / 30=0.32
[0069] The battery pack assembled by the target lithium-io...
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