A method to quickly obtain the resistance values of all single cells in a battery pack
A technology for single cells and battery packs, applied in the measurement of resistance/reactance/impedance, measurement of electricity, measurement of electric variables, etc., can solve problems such as poor practicability, inability to obtain the internal resistance of single cells, battery damage, etc., and achieve small errors. Effect
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example 1
[0040] The target lithium-ion battery is CATL lithium iron phosphate battery, and the battery reference curve data uses the SOC-OCV relationship curve data, and the data interval is ΔSOC=0.1%. The capacity value corresponding to each OCV point is calculated by the formula: Q=SOC*180.
[0041] 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. like 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 Point A in the position, the corresponding voltage V 1 =3.202V, current I 1 =0, the position of the second eigenvalue of ...
example 2
[0048] The target lithium-ion battery is Lishen 21700 ternary battery, and 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*4.5.
[0049] 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 point E in the position, the corresponding voltage V 1 =3.661V, current I 1 = 0, the position of the second eigenvalue in the figure is Figure 4 The point F in the position, the corresponding voltage V 2 =3.887V, current I 2 =0.
[0050] The targ...
example 3
[0056] The target lithium-ion battery is Guoxuan Hi-Tech's soft-pack ternary battery, with a nominal capacity of Cap initial =15Ah, the battery pack is composed of 32 batteries through 2 parallel 16 strings, the battery reference curve data uses the SOC-OCV curve data calibrated by itself, and the data interval is ΔSOC=3%. Q=SOC*30Ah is calculated.
[0057] The capacity increment curve and d 2 Q / dV 2 curve, the voltage V corresponding to the first eigenvalue position 1 = 3.54V, current I 1 =0, the voltage V corresponding to the second eigenvalue position 2 =3.723V, current I 2 =0.
[0058] For the battery pack assembled by the target lithium-ion battery, the target lithium-ion battery is charged at a constant current of 15A until the voltage of any single battery reaches 4.2V, that is, the charging is stopped. The SOC of the battery pack in the early stage of charging is 13%.
[0059] After charging is complete. Extract the data of ΔV ≥ 2mV in the charging data, the da...
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