CN114247663A - Method for sorting single batteries for producing lithium ion battery pack - Google Patents
Method for sorting single batteries for producing lithium ion battery pack Download PDFInfo
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Abstract
The invention discloses a method for sorting single batteries for producing a lithium ion battery pack, which comprises the following steps: measuring constant-current charging static voltage V of battery to be sorted2(ii) a Measuring the discharge capacity C of the battery at a certain discharge current2(ii) a Measuring the voltage of the battery after laying aside to obtain the discharge termination rebound voltage V4(ii) a After charging the battery by a certain mechanism, standing for 2-28 days at a certain temperature T; measuring the voltage V of the battery after placement5And an internal resistance R; according to battery discharge capacity C2Constant current charging static voltage V2Voltage V for stopping discharge4After-rest voltage V5And sorting the batteries to be sorted by the internal resistance R. The method considers the actual charging and discharging working condition of the battery pack, performs charging and discharging tests on the battery by using the actual working current to obtain the battery capacity under the actual working condition, reflects the dynamic characteristic of the battery by using the polarization voltage of the battery under the actual working condition, and has high sorting precision and good effect.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a single battery sorting method for producing a lithium ion battery pack.
Background
The lithium ion battery has the advantages of high specific energy, long cycle life, safety, environmental protection and the like, and is widely applied to the fields of electric automobiles, electric tools, energy storage systems and the like. However, the voltage of the lithium ion single battery is only about 3.2-3.7V, and the single capacity is also limited, so that the single battery cannot meet the requirements of electric loads on the energy and power of the battery. In order to improve the voltage and capacity of the battery, the single batteries are combined into a battery pack in a parallel connection and series connection mode so as to meet the requirements of electric loads on the energy and power of the battery. The lithium ion battery pack is formed by combining a large number of single batteries in a series-parallel connection mode, which means that the performance of the battery pack is influenced by a barrel effect, namely the performance of the battery pack is determined by the single battery with the worst quality in the battery pack. Due to the fact that batch inconsistency of raw materials, fluctuation of production process and environmental factors and the like exist in the actual production process, parameters such as capacity and internal resistance of single batteries of the same type produced in the same batch are different, namely the inconsistency. If the difference exceeds a certain interval range, the performance of the whole battery pack is obviously influenced. Therefore, before the batteries are combined, the single batteries are sorted and matched, the batteries with the difference of parameters such as discharge capacity, internal resistance, voltage, self-discharge rate and the like within a certain range are sorted, and are combined in series and parallel after being matched.
At present, lithium ion battery pack production is mainly based on the static characteristic parameters of single batteries for sorting and matching, generally, the capacity of the single batteries is divided to obtain the discharge capacity of the batteries under a certain charge-discharge mechanism, then the internal resistance and voltage of the batteries are measured after the batteries are placed for a certain time, and then the sorting of the batteries is completed according to the capacity, internal resistance and voltage data of the batteries. The method has short screening time and high efficiency, but can only ensure the consistency of the static characteristic parameters of the screened single batteries, but cannot reflect the dynamic characteristics of the batteries in the working process. On the other hand, the battery capacity data according to the existing sorting process is often obtained under specific charging and discharging conditions, the actual charging and discharging current magnitude and the actual working voltage interval of the battery pack are not considered, and new inconsistency is probably shown under the actual working condition after the single battery packs obtained by sorting and grouping are combined into the battery pack. Therefore, it is necessary to develop a battery sorting method that reflects the dynamic operating characteristics and static parameters of the battery while considering the actual operating conditions of the battery pack.
The dynamic operating characteristics of the battery are closely related to the polarization of the battery. The polarization of the battery exists, so that the charge and discharge potential of the battery is deviated from the balance potential in the working process, and the larger the polarization is, the larger the deviation degree is. Therefore, the polarization voltage of the battery under a certain working current can be used for representing the dynamic characteristics of the battery during operation. During battery sorting, static characteristic parameters such as capacity, internal resistance and self-discharge rate of the battery under actual working conditions and polarization voltage can be integrated for sorting, and consistency of static characteristics and dynamic characteristics of the sorted battery is guaranteed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the single battery sorting method for producing the lithium ion battery pack, and the method can be used for sorting according to the static characteristic parameters and the dynamic characteristic parameters of the battery at the same time, so that the sorting efficiency is high, and the consistency is good.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for sorting single batteries for producing lithium ion battery packs comprises determining charging current I of the method for sorting single batteries according to the nominal parameters of the lithium ion battery packs produced1Charging cut-off voltage V1Discharge current I2And discharge cut-off voltage V3Charging current I1Charging current I for battery packC1/n, n is the number of parallel battery unit cells of the battery pack, and the charging cut-off voltage V11/m of the cut-off voltage for charging the battery pack, wherein m is the serial number of the single batteries of the battery pack and the discharge current I21/n of rated discharge current of the battery pack, n is the parallel number of the single batteries of the battery pack, and the discharge cut-off voltage V3The method is 1/m of the lowest discharge voltage of the battery pack, m is the serial number of single batteries of the battery pack, and the single battery sorting method comprises the following steps:
step 1: with a charging current I1Constant current charging is carried out on the single batteries to be sorted to the charging cut-off voltage V1；
Step (ii) of2: the voltage of the battery is measured after being laid aside for 30 to 120 minutes to obtain the constant current charging static voltage V of the battery2；
And step 3: continue with I1Constant current and constant voltage charging of the battery to V by current1Charging cutoff current I0；
And 4, step 4: with a discharge current I2Constant current discharging the fully charged battery to the discharge cut-off voltage V3Obtaining the discharge capacity C of the battery2；
And 5: the voltage of the battery is measured after 3 to 120 minutes of laying aside to obtain the discharging termination rebound voltage V4，
Step 6: with a charging current I3Charging the discharged battery for t minutes at constant current;
and 7: the battery is kept for 2 to 28 days under the condition of a certain temperature T;
and 8: measuring the voltage V of the battery after placement5And an internal resistance R;
and step 9: according to battery discharge capacity C2Constant current charging static voltage V2Voltage V for stopping discharge4After-rest voltage V5And sorting the batteries to be sorted by the internal resistance R.
In the step 7, the certain temperature T is from normal temperature to 60 ℃.
In the step 9, the individual batteries to be sorted are sorted by a clustering method based on the variation coefficient and the relative deviation, and the method specifically includes:
1) calculating the discharge capacity C of the single battery to be sorted2Average value of C2aSum mean square error C2sIf the coefficient of variation C2s/C2aGreater than a first predetermined threshold value epsilon1Then screen out | C2-C2aThe battery with the maximum | value recalculates the residual battery C2Average value of C2a /Sum mean square error C2s /Up to C2s //C2a /Is less than or equal to a first preset threshold value epsilon1Entering step 2);
2) if the relative deviation | C of the battery discharge capacity enters this step2-C2a /|/C2a /Greater than a second predetermined threshold value epsilon2If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 3) for the rest batteries;
3) calculating the constant-current charging static voltage V of the battery entering the step2Average value of (V)2aSum mean square error V2sIf the coefficient of variation V2s/V2aGreater than a third predetermined threshold epsilon3Then screen out | V2-V2aThe battery with the maximum | value recalculates the residual battery V2Average value of (V)2a /Sum mean square error V2s /Up to V2s //V2a /Is less than or equal to a third preset threshold value epsilon3Entering step 4);
4) if entering the battery V of this step2Relative deviation | V of2-V2a /|/V2a /Greater than a fourth predetermined threshold epsilon4If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 5) for the rest batteries;
5) calculating the discharging termination rebound voltage V of the battery entering the step4Average value of (V)4aSum mean square error V4sIf the coefficient of variation V4s/V4aGreater than a fifth predetermined threshold epsilon5Then screen out | V4-V4aThe battery with the maximum | value recalculates the residual battery V4Average value of (V)4a /Sum mean square error V4s /Up to V4s //V4a /Is less than or equal to a fifth preset threshold value epsilon5Entering step 6);
6) if go to battery | V of this step4-V4a /|/V4a /Greater than a sixth predetermined threshold epsilon6If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 7) for the rest batteries;
7) calculating the voltage V of the battery entering the step5Average value of (V)5aSum mean square error V5sIf the coefficient of variation V5s/V5aGreater than a seventh preset threshold epsilon7Then screen out | V5-V5aThe battery with the maximum | value recalculates the residual battery V5Average value of (V)5a /Sum mean square error V5s /Up to V5s //V5a /Less than or equal to a seventh preset threshold epsilon7Entering step 8);
8) if go to battery | V of this step5-V5a /|/V5a /Greater than an eighth preset threshold epsilon8If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 9) for the rest batteries;
9) calculating the average value R of the internal resistance R of the battery entering the stepaSum mean square error RsIf the coefficient of variation R iss/RaGreater than a ninth preset threshold epsilon9Then screen out | R-RaThe battery with the maximum | value recalculates the average value R of the remaining batteries Ra /Sum mean square error Rs /Up to Rs //Ra /Is less than or equal to a ninth preset threshold epsilon9Entering step 10);
10) if entering the battery of this step | R-Ra /|/Ra /Greater than a tenth predetermined threshold epsilon10And if so, judging that the batteries are unqualified in group matching, screening the batteries, and finishing the sorting and group matching of the batteries.
In the step 9, a K-means clustering method, a mean shift clustering method or a DBSCAN clustering method is adopted to sort the single batteries to be sorted.
The invention has the beneficial effects that:
1. the invention considers the actual charging and discharging working condition of the battery pack, performs charging and discharging tests on the battery by using the actual working current to obtain the battery capacity under the actual working condition, reflects the dynamic characteristic of the battery by using the polarization voltage of the battery under the actual working condition, has high sorting precision, and has the performance of the grouped battery obviously superior to that of the battery pack obtained by static sorting.
2. The invention selects the constant-current charging static voltage V2As a parameter reflecting the charging polarization, it is ensured that the unit cell is one at the charging end of the battery packAnd the overcharge of the single battery is effectively prevented, and the cycle performance and the safety of the battery pack are improved.
3. Compared with the traditional battery sorting, the invention only adds the constant-current charging static voltage V at the battery capacity testing stage2And a discharge termination rebound voltage V4The method has simple steps and high separation efficiency.
Drawings
Fig. 1 is a schematic diagram of a method for sorting unit cells for producing a lithium ion battery pack according to the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention.
As shown in figure 1, the single battery sorting method for producing the lithium ion battery pack determines the charging current I of the single battery sorting method according to the nominal parameters of the produced lithium ion battery pack1Charging cut-off voltage V1Discharge current I2And discharge cut-off voltage V3Charging current I1Charging current I for battery packC1/n, n is the number of parallel battery unit cells of the battery pack, and the charging cut-off voltage V11/m of the cut-off voltage for charging the battery pack, wherein m is the serial number of the single batteries of the battery pack and the discharge current I21/n of rated discharge current of the battery pack, n is the parallel number of the single batteries of the battery pack, and the discharge cut-off voltage V3The method is 1/m of the lowest discharge voltage of the battery pack, m is the serial number of single batteries of the battery pack, and the single battery sorting method comprises the following steps:
step 1: with a charging current I1Constant current charging is carried out on the single batteries to be sorted to the charging cut-off voltage V1；
Step 2: the voltage of the battery is measured after the battery is placed for 30 to 120 minutes to obtain the constant current charging stillness of the batteryVoltage V2；
And step 3: continue with I1Constant current and constant voltage charging of the battery to V by current1Charging cutoff current I0；
And 4, step 4: with a discharge current I2Constant current discharging the fully charged battery to the discharge cut-off voltage V3Obtaining the discharge capacity C of the battery2；
And 5: the voltage of the battery is measured after 3 to 120 minutes of laying aside to obtain the discharging termination rebound voltage V4，
Step 6: with a charging current I3Charging the discharged battery for t minutes at constant current;
and 7: the battery is kept for 2 to 28 days under the condition of a certain temperature T;
and 8: measuring the voltage V of the battery after placement5And an internal resistance R;
and step 9: according to battery discharge capacity C2Constant current charging static voltage V2Voltage V for stopping discharge4After-rest voltage V5And sorting the batteries to be sorted by the internal resistance R.
In the step 7, the certain temperature T is from normal temperature to 60 ℃.
In the step 9, the individual batteries to be sorted are sorted by a clustering method based on the variation coefficient and the relative deviation, and the method specifically includes:
1) calculating the discharge capacity C of the single battery to be sorted2Average value of C2aSum mean square error C2sIf the coefficient of variation C2s/C2aGreater than a first predetermined threshold value epsilon1Then screen out | C2-C2aThe battery with the maximum | value recalculates the residual battery C2Average value of C2a /Sum mean square error C2s /Up to C2s //C2a /Is less than or equal to a first preset threshold value epsilon1Entering step 2);
2) if the relative deviation | C of the battery discharge capacity enters this step2-C2a /|/C2a /Greater than a second predetermined threshold value epsilon2If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 3) for the rest batteries;
3) calculating the constant-current charging static voltage V of the battery entering the step2Average value of (V)2aSum mean square error V2sIf the coefficient of variation V2s/V2aGreater than a third predetermined threshold epsilon3Then screen out | V2-V2aThe battery with the maximum | value recalculates the residual battery V2Average value of (V)2a /Sum mean square error V2s /Up to V2s //V2a /Is less than or equal to a third preset threshold value epsilon3Entering step 4);
4) if entering the battery V of this step2Relative deviation | V of2-V2a /|/V2a /Greater than a fourth predetermined threshold epsilon4If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 5) for the rest batteries;
5) calculating the discharging termination rebound voltage V of the battery entering the step4Average value of (V)4aSum mean square error V4sIf the coefficient of variation V4s/V4aGreater than a fifth predetermined threshold epsilon5Then screen out | V4-V4aThe battery with the maximum | value recalculates the residual battery V4Average value of (V)4a /Sum mean square error V4s /Up to V4s //V4a /Is less than or equal to a fifth preset threshold value epsilon5Entering step 6);
6) if go to battery | V of this step4-V4a /|/V4a /Greater than a sixth predetermined threshold epsilon6If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 7) for the rest batteries;
7) calculating the voltage V of the battery entering the step5Average value of (V)5aSum mean square error V5sIf the coefficient of variation V5s/V5aGreater than a seventh preset threshold epsilon7Then screen out | V5-V5aThe battery with the largest | value is recalculatedResidual battery V5Average value of (V)5a /Sum mean square error V5s /Up to V5s //V5a /Less than or equal to a seventh preset threshold epsilon7Entering step 8);
8) if go to battery | V of this step5-V5a /|/V5a /Greater than an eighth preset threshold epsilon8If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 9) for the rest batteries;
9) calculating the average value R of the internal resistance R of the battery entering the stepaSum mean square error RsIf the coefficient of variation R iss/RaGreater than a ninth preset threshold epsilon9Then screen out | R-RaThe battery with the maximum | value recalculates the average value R of the remaining batteries Ra /Sum mean square error Rs /Up to Rs //Ra /Is less than or equal to a ninth preset threshold epsilon9Entering step 10);
10) if entering the battery of this step | R-Ra /|/Ra /Greater than a tenth predetermined threshold epsilon10And if so, judging that the batteries are unqualified in group matching, screening the batteries, and finishing the sorting and group matching of the batteries.
In the step 9, a K-means clustering method, a mean shift clustering method or a DBSCAN clustering method is adopted to sort the single batteries to be sorted.
Examples
The purpose of this example is to sort and group 12 18650 model 2.6Ah ternary lithium ion batteries by the method of the present invention, and the obtained group battery is used to produce a 3S2P lithium ion battery pack with a combined structure. The nominal voltage of the lithium ion battery pack is 10.8V, the nominal capacity is 5.2Ah, the charging current is 2A, the working discharging current is 3A, and the working voltage range is 9V-12.6V. According to the actual working parameters of the battery pack, the charging current I when the capacity of the battery to be sorted is tested by using the method can be calculated1Is 2A/2 ═ 1A, I2Discharge current 3A/2 ═ 1.5A, discharge cut-off voltage V39V/3-3V.
The sorting steps are as follows:
step 1: carrying out constant current charging on the single batteries to be sorted by using the voltage 1A until the charging cut-off voltage is 4.2V;
step 2: the voltage of the battery is measured after the battery is placed for 60 minutes to obtain the constant current charging static voltage V of the battery2The data are shown in Table 1;
and step 3: continuously carrying out constant-current constant-voltage charging on the battery to 4.2V by using the current of 1A, and stopping the charging at the current of 52 mA;
and 4, step 4: discharging the fully charged battery at constant current of 1.5A until the discharge cut-off voltage reaches 3V to obtain the discharge capacity C of the battery2The data are shown in Table 1;
and 5: the voltage of the battery is measured after the battery is placed for 60 minutes to obtain the discharge termination rebound voltage V4The data are shown in Table 1,
step 6: charging the discharged battery for 60 minutes at a constant current of 1.3A;
and 7: the battery is kept for 3 days at the temperature of 45 ℃;
and 8: measuring the voltage V of the battery after placement5And internal resistance R1The data are shown in Table 1;
TABLE 1 batteries to be tested C2、V2、V4、V5And R1Measured value of
| Number of battery | C2(mAh) | V2(V) | V4(V) | V5(V) | R1(mΩ) |
| 1 | 2580 | 4.057 | 3.179 | 3.697 | 21.3 |
| 2 | 2590 | 4.083 | 3.142 | 3.685 | 20 |
| 3 | 2592 | 4.085 | 3.145 | 3.683 | 20.2 |
| 4 | 2594 | 4.085 | 3.142 | 3.682 | 20.3 |
| 5 | 2597 | 4.085 | 3.145 | 3.682 | 19.4 |
| 6 | 2589 | 4.08 | 3.139 | 3.684 | 19.7 |
| 7 | 2591 | 4.075 | 3.146 | 3.674 | 19.4 |
| 8 | 2592 | 4.081 | 3.141 | 3.682 | 19.2 |
| 9 | 2595 | 4.078 | 3.138 | 3.672 | 19.3 |
| 10 | 2590 | 4.077 | 3.146 | 3.652 | 20.4 |
| 11 | 2592 | 4.079 | 3.143 | 3.683 | 20.1 |
| 12 | 2595 | 4.082 | 3.14 | 3.682 | 19.8 |
And step 9: according to battery discharge capacity C2Constant current charging static voltage V2Voltage V for stopping discharge4After-rest voltage V5And internal resistance R1And sorting the batteries to be sorted. The method comprises the following specific steps:
1) calculating the discharge capacity C of the single battery to be sorted2Average value of C2a2591.4 and mean square error C2s4.1324, take the first preset threshold epsilon1When the ratio is 0.001, then C2s/C2a＝0.0016>ε1. Screening out | C2-C2aThe first battery with the maximum | value recalculates the residual battery C2Average value of C2a /2592.5 and mean square error C2s /2.3884, then C2s //C2a /＝0.0009<ε1Entering step 2);
TABLE 2| C2-C2aI calculation table
2) Taking a second preset threshold valueε2When the value is 0.002, | C is calculated2-C2a /|/C2a /The values are shown in Table 2. As can be seen from Table 2, all cells | C2-C2a /|/C2a /Are all less than epsilon2All the batteries enter the step 3);
TABLE 3| C2-C2a /|/C2a /Calculation table
| Number of battery | C2(mAh) | |C2-C2a /|/C2a / |
| 2 | 2590 | 0.00096 |
| 3 | 2592 | 0.00019 |
| 4 | 2594 | 0.000579 |
| 5 | 2597 | 0.001736 |
| 6 | 2589 | 0.00135 |
| 7 | 2591 | 0.00058 |
| 8 | 2592 | 0.00019 |
| 9 | 2595 | 0.000964 |
| 10 | 2590 | 0.00096 |
| 11 | 2592 | 0.00019 |
| 12 | 2595 | 0.000964 |
| C2a / | 2592.5 |
3) Calculating to obtain the constant-current charging static voltage V of the battery entering the step 112Average value of (V)2a4.081 and mean square error V2s0.00329, take the third preset threshold epsilon3When the value is 0.001, then V2s/V2a＝0.00097<ε3All the batteries enter step 4);
4) calculate | V of 11 batteries entering this step2-V2a|/V2aThe value and the result are shown in Table 4, and a fourth preset threshold value epsilon is taken4When the battery voltage is 0.001, the 7 th battery | V is shown in table 42-V2a|/V2a＝0.00147>ε4Judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 5) for the rest batteries;
TABLE 4| V2-V2a|/V2aCalculation table
| Number of battery | V2(V) | |V2-V2a| | |V2-V2a|/V2a |
| 2 | 4.083 | 0.002 | 0.00049 |
| 3 | 4.085 | 0.004 | 0.00098 |
| 4 | 4.085 | 0.004 | 0.00098 |
| 5 | 4.085 | 0.004 | 0.00098 |
| 6 | 4.08 | 0.001 | 0.00025 |
| 7 | 4.075 | 0.006 | 0.00147 |
| 8 | 4.081 | 0 | 0 |
| 9 | 4.078 | 0.003 | 0.00074 |
| 10 | 4.077 | 0.004 | 0.00098 |
| 11 | 4.079 | 0.002 | 0.00049 |
| 12 | 4.082 | 0.001 | 0.000245 |
| V2a | 4.081 |
5) Calculating to obtain the discharging termination rebound voltage V of 10 batteries entering the step4Average value of (V)4a3.142 and mean square error V4s0.00255, take the fifth preset threshold ε5When the value is 0.001, then V4s/V4a＝0.00081<ε5All 10 batteries go to step 6);
6) calculate | V of 10 batteries entering this step4-V4a|/V4aThe values and results are shown in Table 5, and a sixth preset threshold value epsilon is taken6As can be seen from table 5, all cells | V ═ 0.0024-V4a|/V4a<ε6All 10 batteries go to step 7);
TABLE 5| V4-V4a|/V4aCalculation table
| Number of battery | V4(V) | |V4-V4a| | |V4-V4a|/V4a |
| 2 | 3.142 | 0 | 0 |
| 3 | 3.145 | 0.003 | 0.000955 |
| 4 | 3.142 | 0 | 0 |
| 5 | 3.145 | 0.003 | 0.000955 |
| 6 | 3.139 | 0.003 | 0.00095 |
| 8 | 3.141 | 0.001 | 0.00032 |
| 9 | 3.138 | 0.004 | 0.00127 |
| 10 | 3.146 | 0.004 | 0.00127 |
| 11 | 3.143 | 0.001 | 0.000318 |
| 12 | 3.14 | 0.002 | 0.00064 |
| V4a| | 3.1421 |
7) Calculating to obtain the battery voltage V of 10 batteries in the step5Average value of (V)5a3.679 and mean square error V5sTaking the seventh preset threshold value epsilon as 0.009527When the value is 0.001, then V5s/V5a＝0.00259>ε7Then calculate | V5-V5aThe value of | V is screened out5-V5aThe 10 th battery with the maximum | value recalculates the residual battery V5Average value of (V)5a /3.6817 and mean square error V5s /0.00358, then V5s //V5a /＝0.00097<ε7,The rest 9 batteries enter the step 8);
TABLE 6| V5-V5aI value calculation table
8) 9 batteries | V are calculated and entered into the step5-V5a /|/V5a /The values and results are shown in Table 7, and the eighth preset threshold value ε is taken8When the total weight is 0.001, the 9 th battery | V is shown in table 75-V5a /|/V5a /＝0.00272>ε8If so, screening out the batteries which are not qualified in matching, and entering the step 9) by using the remaining 8 batteries;
TABLE 7| V5-V5a /|/V5a /Value calculation table
| Number of battery | V5(V) | |V5-V5a /|/V5a / |
| 2 | 3.685 | 0.000815 |
| 3 | 3.683 | 0.000272 |
| 4 | 3.682 | 0 |
| 5 | 3.682 | 0 |
| 6 | 3.684 | 0.000543 |
| 8 | 3.682 | 0 |
| 9 | 3.672 | 0.00272 |
| 11 | 3.683 | 0.000272 |
| 12 | 3.682 | 0 |
| V5a / | 3.6817 |
9) Calculating to obtain the internal resistance R of the battery in the step 81Average value R of1a19.84 and mean square error R1s0.38419, take the ninth preset threshold ε9When R is 0.02, then R1s/R1a＝0.01937<ε9Then 8 batteries enter step 10);
10) the calculation is carried out to 8 batteries | R-R in the stepa|/R5aThe values and results are shown in Table 8, and the tenth predetermined threshold ε is taken10As can be seen from table 8, all 8 batteries | R-R ═ 0.03a|/Ra<ε10And judging that the remaining 8 battery cores all meet the sorting and grouping requirement, and finishing the sorting and grouping of the batteries. 6 cells from the 8 cells can be selected for producing the 3S2P lithium ion battery pack.
TABLE 8R-Ra|/R1aValue meterCalculating table
| Number of battery | R(mΩ) | |R-Ra|/Ra |
| 2 | 20 | 0.0081 |
| 3 | 20.2 | 0.0181 |
| 4 | 20.3 | 0.0232 |
| 5 | 19.4 | 0.0222 |
| 6 | 19.7 | 0.0071 |
| 8 | 19.2 | 0.0323 |
| 11 | 20.1 | 0.0131 |
| 12 | 19.8 | 0.0020 |
| Ra | 19.84 |
The above-mentioned embodiments are only for illustrating the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and to carry out the same, and the present invention shall not be limited to the embodiments, i.e. the equivalent changes or modifications made within the spirit of the present invention shall fall within the scope of the present invention.
Claims (4)
1. A method for sorting single batteries for producing lithium ion battery packs is characterized in that the charging current I of the method for sorting single batteries is determined according to the nominal parameters of the produced lithium ion battery packs1Charging cut-off voltage V1Discharge current I2And discharge cut-off voltage V3Charging current I1Charging current I for battery packC1/n, n is the number of parallel battery unit cells of the battery pack, and the charging cut-off voltage V11/m of the cut-off voltage for charging the battery pack, wherein m is the serial number of the single batteries of the battery pack and the discharge current I21/n of rated discharge current of the battery pack, n is the parallel number of the single batteries of the battery pack, and the discharge cut-off voltage V3The method is 1/m of the lowest discharge voltage of the battery pack, m is the serial number of single batteries of the battery pack, and the single battery sorting method comprises the following steps:
step 1: with a charging current I1Constant current charging is carried out on the single batteries to be sorted to the charging cut-off voltage V1；
Step 2: the voltage of the battery is measured after being laid aside for 30 to 120 minutes to obtain the constant current charging static voltage V of the battery2；
And step 3: continue with I1Constant current and constant voltage charging of the battery to V by current1Charging cutoff current I0；
And 4, step 4: with a discharge current I2Constant current discharging the fully charged battery to the discharge cut-off voltage V3Obtaining the discharge capacity C of the battery2；
And 5: the voltage of the battery is measured after 3 to 120 minutes of laying aside to obtain the discharging termination rebound voltage V4，
Step 6: with a charging current I3Charging the discharged battery for t minutes at constant current;
and 7: the battery is kept for 2 to 28 days under the condition of a certain temperature T;
and 8: measuring the voltage V of the battery after placement5And an internal resistance R;
and step 9: according to battery discharge capacity C2Constant current charging static voltage V2Voltage V for stopping discharge4After-rest voltage V5And sorting the batteries to be sorted by the internal resistance R.
2. The method for sorting unit cells for manufacturing a lithium ion battery pack according to claim 1, wherein the certain temperature T in the step 7 is from room temperature to 60 ℃.
3. The method for sorting the single batteries for producing the lithium ion battery pack according to claim 1, wherein in the step 9, the single batteries to be sorted are sorted by a clustering method based on the coefficient of variation and the relative deviation, and the method specifically comprises the following steps:
1) calculating the discharge capacity C of the single battery to be sorted2Average value of C2aSum mean square error C2sIf the coefficient of variation C2s/C2aGreater than a first predetermined threshold value epsilon1Then screen out | C2-C2aThe battery with the maximum | value recalculates the residual battery C2Average value of C2a /Sum mean square error C2s /Up to C2s //C2a /Is less than or equal to a first preset threshold value epsilon1Entering step 2);
2) if the relative deviation | C of the battery discharge capacity enters this step2-C2a /|/C2a /Greater than a second predetermined threshold value epsilon2If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 3) for the rest batteries;
3) calculating the constant-current charging static voltage V of the battery entering the step2Average value of (V)2aSum mean square error V2sIf the coefficient of variation V2s/V2aGreater than a third predetermined threshold epsilon3Then screen out | V2-V2aThe battery with the maximum | value recalculates the residual battery V2Average value of (V)2a /Sum mean square error V2s /Up to V2s //V2a /Is less than or equal to a third preset threshold value epsilon3Entering step 4);
4) if entering the battery V of this step2Relative deviation | V of2-V2a /|/V2a /Greater than a fourth predetermined threshold epsilon4If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 5) for the rest batteries;
5) calculating the discharging termination rebound voltage V of the battery entering the step4Average value of (V)4aSum mean square error V4sIf the coefficient of variation V4s/V4aGreater than a fifth predetermined threshold epsilon5Then screen out | V4-V4aThe battery with the maximum | value recalculates the residual battery V4Average value of (V)4a /Sum mean square error V4s /Up to V4s //V4a /Is less than or equal to a fifth preset threshold value epsilon5Entering step 6);
6) if go to battery | V of this step4-V4a /|/V4a /Greater than a sixth predetermined threshold epsilon6If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 7) for the rest batteries;
7) calculate the access bookStep battery voltage V5Average value of (V)5aSum mean square error V5sIf the coefficient of variation V5s/V5aGreater than a seventh preset threshold epsilon7Then screen out | V5-V5aThe battery with the maximum | value recalculates the residual battery V5Average value of (V)5a /Sum mean square error V5s /Up to V5s //V5a /Less than or equal to a seventh preset threshold epsilon7Entering step 8);
8) if go to battery | V of this step5-V5a /|/V5a /Greater than an eighth preset threshold epsilon8If so, judging that the batteries are unqualified in group matching, screening out the batteries, and entering the step 9) for the rest batteries;
9) calculating the average value R of the internal resistance R of the battery entering the stepaSum mean square error RsIf the coefficient of variation R iss/RaGreater than a ninth preset threshold epsilon9Then screen out | R-RaThe battery with the maximum | value recalculates the average value R of the remaining batteries Ra /Sum mean square error Rs /Up to Rs //Ra /Is less than or equal to a ninth preset threshold epsilon9Entering step 10);
10) if entering the battery of this step | R-Ra /|/Ra /Greater than a tenth predetermined threshold epsilon10And if so, judging that the batteries are unqualified in group matching, screening the batteries, and finishing the sorting and group matching of the batteries.
4. The method for sorting the single batteries for producing the lithium ion battery pack according to claim 1, wherein in the step 9, the single batteries to be sorted are sorted by adopting a K-means clustering method, a mean shift clustering method or a DBSCAN clustering method.
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