CN107132481B - Method and system for identifying monomer consistency in battery pack - Google Patents
Method and system for identifying monomer consistency in battery pack Download PDFInfo
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- CN107132481B CN107132481B CN201710261042.4A CN201710261042A CN107132481B CN 107132481 B CN107132481 B CN 107132481B CN 201710261042 A CN201710261042 A CN 201710261042A CN 107132481 B CN107132481 B CN 107132481B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/3644—Constructional arrangements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
Abstract
The invention relates to a method and a system for identifying the consistency of single batteries in a battery pack, wherein the method comprises the following steps of S1, measuring the capacity of each single battery in the battery pack to obtain the single batteries with consistent capacity; s2, measuring the internal resistance of each single battery with the consistent capacity to obtain the single batteries with the consistent internal resistance; and S3, carrying out polarization test on each single battery with consistent internal resistance to obtain the single batteries with consistent polarization, wherein the single batteries with consistent polarization are the identification results of the single batteries in the battery pack. The invention has the beneficial effects that: the method for identifying the consistency of the single batteries in the battery pack divides the consistency of the battery pack into capacity consistency, internal resistance consistency and polarization consistency, and the single batteries are qualified in consistency only when the three consistency needs to be met simultaneously, so that the consistency of the single batteries in the battery pack can be identified in a high-precision and quantitative manner.
Description
Technical Field
The invention relates to the field of battery testing, in particular to a method and a system for identifying monomer consistency in a battery pack.
Background
Storage batteries are widely used in various fields as energy storage and conversion devices. In some fields such as electric vehicles, energy storage, electric tools and consumer electronics, batteries are often required to be connected in series or in parallel to form a battery pack in order to increase the available energy and increase the output power. Initial performance inconsistencies between individual cells in a battery pack, as well as differences between individual cells that result from successive charge and discharge cycles, will accelerate the decay of the capacity of certain individual cells, thereby causing premature failure of the battery pack. Therefore, the combined application of the battery not only requires that the performance index of the single battery reaches the specified requirement, but also has strict requirements on the matching of the performance of the single batteries participating in the matching. The difference of the single batteries mainly consists of the following aspects: difference of initial performance of single batteries before combined packaging; amplification of performance differences resulting from inconsistencies in performance variations in cyclic storage.
In the use of the battery pack, any battery quality failure affects the overall performance, causing the entire battery pack to fail. Therefore, the batteries must be sorted during the combination process, so that the batteries are consistent as much as possible in the aspects of capacity, internal resistance, charging voltage platform, temperature rise during charging and discharging, self-discharging rate, service life and the like. Common battery classification methods are: volumetric method, internal resistance method, characteristic curve method. The so-called characteristic curve method is to compare the actual charging or discharging curves of the single batteries, however, it is difficult to find a quantitative evaluation index. Although the capacity method and the internal resistance method can be compared quantitatively, then even if the battery is judged to have the same capacity and internal resistance, inconsistency occurs in actual use, that is, the capacity and the internal resistance cannot be simply used as indexes for evaluating the consistency of the battery pack.
Disclosure of Invention
The invention aims to provide a method and a system for identifying the consistency of single batteries in a battery pack, which can identify the consistency of the single batteries in the battery pack in a high-precision and quantitative manner.
The technical scheme for solving the technical problems is as follows: a method of identifying a correspondence of cells in a battery pack, comprising the steps of,
s1, measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
s2, measuring the internal resistance of each single battery with the consistent capacity to obtain the single batteries with the consistent internal resistance;
and S3, carrying out polarization test on each single battery with consistent internal resistance to obtain the single batteries with consistent polarization, wherein the single batteries with consistent polarization are the identification results of the single batteries in the battery pack.
The invention has the beneficial effects that: the method for identifying the consistency of the single batteries in the battery pack divides the consistency of the battery pack into capacity consistency, internal resistance consistency and polarization consistency, and the single batteries are qualified in consistency only when the three consistency needs to be met simultaneously, so that the consistency of the single batteries in the battery pack can be identified in a high-precision and quantitative manner.
On the basis of the technical scheme, the invention can be further improved as follows.
Furthermore, the number N of the single batteries in the battery pack is more than or equal to 40, and the type, the specification and the appearance of each single battery in the battery pack are consistent.
The beneficial effect of adopting the further scheme is that: when the number N of the measured single batteries is more than or equal to 40, the statistical calculation can be effectively carried out.
Further, in S1, specifically,
s11, respectively measuring the standard capacity of each single battery in the battery pack, and calculating the standard capacity relative error of each single battery;
s12, setting a first threshold value for the relative error of the standard capacity, judging whether the standard capacity error of each single battery in the battery pack is within the first threshold value, reserving the single batteries with the standard capacity errors within the first threshold value, and simultaneously rejecting the single batteries with the standard capacity errors not within the first threshold value;
s13, setting the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value to be in accordance with a first normal distribution, and setting a first confidence coefficient for the first normal distribution;
s14, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value is within the first confidence coefficient, if so, determining the single battery to be the single battery with consistent capacity and reserving the single battery, otherwise, executing S15 to continue judging;
and S15, setting a second threshold value for the standard capacity relative error, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value and outside the first confidence degree is within the second threshold value, if so, determining the single battery to be the single battery with consistent capacity, reserving the single battery, otherwise, determining the single battery to be the single battery with inconsistent capacity, and rejecting the single battery.
The beneficial effect of adopting the further scheme is that: by setting the standard capacity relative error first threshold, the first confidence coefficient and the first threshold, the single batteries with consistent capacity can be accurately identified.
Further, in S2, specifically,
s21, adjusting the charge state of the single batteries with the consistent capacity to be SOC (state of charge) 50%, respectively measuring the alternating current internal resistance of each single battery with the consistent capacity, and calculating the relative error of the alternating current internal resistance of each single battery with the consistent capacity;
s22, setting a third threshold value for the relative error of the alternating current internal resistance, judging whether the alternating current internal resistance error of each single battery with the consistent capacity is within the third threshold value, reserving the single batteries with the alternating current internal resistance error within the third threshold value, and simultaneously rejecting the single batteries with the alternating current internal resistance error not within the third threshold value;
s23, setting the alternating current internal resistance relative error of the single battery with the alternating current internal resistance relative error within the third threshold value to obey a second normal distribution, and setting a second confidence coefficient for the second normal distribution;
s24, judging whether the relative error of the alternating current internal resistance of the single battery with the relative error of the alternating current internal resistance within the third threshold value is within the second confidence coefficient, if so, determining the single battery to be the single battery with consistent internal resistance, and reserving the single battery, otherwise, executing S25 to continuously judge;
s25, setting a fourth threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of the single battery within the third threshold value and outside the second confidence level is within the fourth threshold value, if so, determining the single battery to be the single battery with consistent internal resistance, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent internal resistance, and rejecting the single battery.
The beneficial effect of adopting the further scheme is that: through setting the third threshold, the second confidence and the fourth threshold of the relative error of the alternating current internal resistance, the single batteries with consistent internal resistance can be accurately identified.
Further, in S21, the state of charge of the cells having the same capacity is adjusted to have an SOC of 50%, and the cells having the same capacity are discharged, charged to an amount of electricity equal to half the standard capacity, and left to stand for 2 hours.
The beneficial effect of adopting the further scheme is that: the stability of the single battery is guaranteed, and the measuring precision is improved.
Further, the alternating-current internal resistance is an internal ohmic resistance obtained by measuring the current and the voltage drop of the single batteries with consistent capacity by adopting alternating current with the frequency greater than 1000 hertz.
The beneficial effect of adopting the further scheme is that: the internal resistance measured by the high-frequency alternating current is the internal ohmic resistance of the single battery, and the internal resistance does not comprise the polarization resistance and the diffusion resistance of electrochemical reaction, so that conditions can be provided for accurately measuring the alternating current internal resistance of the single battery.
Further, in S3, specifically,
s31, adjusting the charge state of the single batteries with the consistent internal resistance to SOC (state of charge) of 50%, respectively calculating the polarization voltage of each single battery with the consistent internal resistance through polarization test, and calculating the relative error of the polarization voltage of each single battery with the consistent internal resistance;
s32, setting a fifth threshold value for the relative error of the polarization voltage, judging whether the polarization voltage error of each single battery with consistent internal resistance is within the fifth threshold value, reserving the single battery with the polarization voltage error within the fifth threshold value, and rejecting the single battery with the polarization voltage error not within the fifth threshold value;
s33, setting the polarization voltage relative error of the single battery with the polarization voltage relative error within the fifth threshold value to obey a third normal distribution, and setting a third confidence coefficient for the third normal distribution;
s34, judging whether the relative error of the polarization voltage of the single battery with the relative error of the polarization voltage within the fifth threshold value is within the third confidence coefficient, if so, determining the single battery to be the single battery with consistent polarization, and reserving the single battery, otherwise, executing S35 to continue judging;
and S35, setting a sixth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of the single battery within the fifth threshold value and outside the third confidence level is within the sixth threshold value, if so, determining the single battery to be the single battery with consistent polarization, reserving the single battery, otherwise, determining the single battery to be the single battery with inconsistent polarization, and rejecting the single battery.
The beneficial effect of adopting the further scheme is that: by setting the fifth threshold, the third confidence and the sixth threshold of the polarization voltage relative error, the single batteries with consistent polarization can be accurately identified.
Further, in S31, the step of calculating the polarization voltage of each unit cell having the same internal resistance through the polarization test includes the steps of,
s311, measuring the open-circuit voltage U of each single battery with consistent internal resistanceOCV；
S312, recording the 10 th second instantaneous voltage U after the discharge of each single battery 3C with consistent internal resistanceTThen, the polarization voltage U of each single battery with the same internal resistancep＝UOCV-UT。
Further, in S31, the charge state of the unit cells having the same internal resistance is adjusted to have an SOC of 50%, and the unit cells having the same internal resistance are discharged, charged to an amount of electricity of half the standard capacity, and left to stand for 2 hours.
The beneficial effect of adopting the further scheme is that: the stability of the single battery is guaranteed, and the measuring precision is improved.
Based on the method for identifying the consistency of the monomers in the battery pack, the invention also provides a system for identifying the consistency of the monomers in the battery pack.
A system for identifying the consistency of monomers in a battery pack comprises a capacity measuring module, an internal resistance measuring module and a polarization testing module,
the capacity measurement module is used for measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
the internal resistance measuring module is used for measuring alternating current internal resistance of each single battery with consistent capacity to obtain the single batteries with consistent alternating current internal resistance;
the polarization testing module is used for carrying out polarization testing on each single battery with consistent alternating current internal resistance to obtain the single batteries with consistent polarization, wherein the single batteries with consistent polarization are recognition results of single batteries in the battery pack.
The invention has the beneficial effects that: the system for identifying the consistency of the single batteries in the battery pack divides the consistency of the battery pack into capacity consistency, internal resistance consistency and polarization consistency, and the single batteries are qualified in consistency only when the three consistency needs to be met simultaneously, so that the consistency of the single batteries in the battery pack can be identified in a high-precision and quantitative manner.
Drawings
FIG. 1 is an overall flow chart of a method of identifying cell identity in a battery pack in accordance with the present invention;
fig. 2 is a flowchart of determining capacity consistency in a method of identifying cell consistency in a battery pack according to the present invention;
fig. 3 is a flowchart of determining internal resistance consistency in a method of identifying cell consistency in a battery pack according to the present invention;
FIG. 4 is a flowchart illustrating the determination of polarization consistency in a method for identifying cell consistency in a battery pack according to the present invention;
FIG. 5 is a graph illustrating the relationship between normal distribution curves and confidence levels in a method for identifying cell identity in a battery pack according to the present invention;
fig. 6 is a block diagram of the mechanism of a system for identifying the identity of cells in a battery pack according to the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, a method of identifying a correspondence of cells in a battery pack includes the steps of,
s1, measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
s2, measuring the internal resistance of each single battery with the consistent capacity to obtain the single batteries with the consistent internal resistance;
and S3, carrying out polarization test on each single battery with consistent internal resistance to obtain the single batteries with consistent polarization, wherein the single batteries with consistent polarization are the identification results of the single batteries in the battery pack.
In this embodiment, the present invention is mainly applicable to lithium ion batteries, and may also be used to detect other batteries. The batteries used for detection are the same type of batteries, namely, the battery has the same material composition, and the specification and the appearance of the batteries are the same, preferably the batteries produced in the same batch; and meanwhile, the number N of the single batteries in the battery pack is more than or equal to 40, otherwise, effective statistical calculation cannot be carried out.
As shown in fig. 2, the S1 specifically includes:
s11, respectively measuring the standard capacity of each single battery in the battery pack, and calculating the standard capacity relative error of each single battery; the method for measuring the standard capacity (or called rated capacity) of the battery needs to be based on the method formulated by national standard or battery generation enterprises, and the calculation formula of the standard capacity relative error is as follows:
s12, setting a first threshold value for the relative error of the standard capacity, judging whether the standard capacity error of each single battery in the battery pack is within the first threshold value, reserving the single batteries with the standard capacity errors within the first threshold value, and simultaneously rejecting the single batteries with the standard capacity errors not within the first threshold value; in this particular embodiment, the first threshold is set to 5%.
S13, setting the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value to be in accordance with a first normal distribution, and setting a first confidence coefficient for the first normal distribution; a normal distribution (Normaldistribution), also known as a "normal distribution", also known as a Gaussian distribution (Gaussian distribution). If the random variable X obeys a probability distribution with a position parameter of mu and a scale parameter of sigma and its probability density function is
This random variable is called a normal random variable, and the distribution to which the normal random variable is subjected is called a normal distribution. Where x is the standard capacity relative error, the positional parameter is μ, and σ is the standard deviation, and the calculation is made according to the following formula
Confidence, or confidence interval, refers to the distance or length of the region where the overall parameter is located at a certain confidence. The confidence level is also called significance level, meaning stage, confidence coefficient and the like, and refers to the probability that an error may be made when the estimated overall parameter falls in a certain interval. For example, a 95% confidence level means that the overall parameter falls within the interval, with an estimated probability of 95% for correctness and 5% for errors. If there is a mean of 68.26% of all means that falls between one standard error above and below μ, then it can be inferred that: the interval between 68.26% of all means plus one or minus one standard error will contain the overall parameter μ, i.e., 68.26% of the chance is contained between any one mean ± 1 standard error, or 68.26% of the probability that μ is estimated to be correct between the means ± 1 standard error. For the same reason, it can be said that: the probability of μ being correct between the mean ± 1.96 standard errors is 95%, the probability of μ being correct between the mean ± 2.58 standard errors is 99%, and any other possible probability. The relationship between the normal distribution curve and the confidence level is shown in FIG. 5.
S14, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value is within the first confidence coefficient, if so, determining the single battery to be the single battery with consistent capacity and reserving the single battery, otherwise, executing S15 to continue judging; in this particular embodiment, the first confidence level is set to 95%.
S15, setting a second threshold value for the standard capacity relative error, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value and outside the first confidence degree is within the second threshold value, if so, determining the single battery to be the single battery with consistent capacity, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent capacity, and rejecting the single battery; in this embodiment, the second threshold is set to 2%, because according to the statistical rule, as long as the number of the single batteries is large enough, the standard capacity of each single battery is always out of the confidence level, but this does not mean that the single batteries out of the confidence level are inconsistent in capacity, further judgment needs to be performed through the second threshold.
As shown in fig. 3, the S2 specifically includes:
s21, adjusting the charge state of the single batteries with the consistent capacity to be SOC (state of charge) 50%, respectively measuring the alternating current internal resistance of each single battery with the consistent capacity, and calculating the relative error of the alternating current internal resistance of each single battery with the consistent capacity; the calculation principle of the relative error of the alternating current internal resistance is the same as the calculation principle of the relative error of the standard capacity, and only the object is changed into the alternating current internal resistance.
S22, setting a third threshold value for the relative error of the alternating current internal resistance, judging whether the alternating current internal resistance error of each single battery with the consistent capacity is within the third threshold value, reserving the single batteries with the alternating current internal resistance error within the third threshold value, and simultaneously rejecting the single batteries with the alternating current internal resistance error not within the third threshold value; in this particular embodiment, the third threshold is set to 5%.
S23, setting the alternating current internal resistance relative error of the single battery with the alternating current internal resistance relative error within the third threshold value to obey a second normal distribution, and setting a second confidence coefficient for the second normal distribution; in this particular embodiment, the second confidence level is set to 95%; the second normal distribution and the second confidence coefficient are the same as the first normal distribution and the first confidence coefficient of the standard capacity relative error, and only the statistical object is changed into the alternating current internal resistance relative error.
S24, judging whether the relative error of the alternating current internal resistance of the single battery with the relative error of the alternating current internal resistance within the third threshold value is within the second confidence coefficient, if so, determining the single battery to be the single battery with consistent internal resistance, and reserving the single battery, otherwise, executing S25 to continuously judge;
s25, setting a fourth threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of the single battery within the third threshold value and outside the second confidence level is within the fourth threshold value, if so, determining the single battery to be the single battery with consistent internal resistance, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent internal resistance, and rejecting the single battery; in the present embodiment, the fourth threshold is set to 2%.
In S21, the state of charge of the cells having the same capacity is adjusted to have an SOC of 50%, and the cells having the same capacity are discharged, charged to an amount of half the standard capacity, and left to stand for 2 hours.
The alternating current internal resistance is an internal ohmic resistance obtained by measuring the current and the voltage drop of the single batteries with consistent capacity by adopting alternating current with the frequency of more than 1000 Hz; by ac internal resistance is meant that the current through the battery and the voltage drop are measured with ac power, the resistance is equal to the voltage drop divided by the current, and the frequency of the ac power is greater than 1000 hz. The internal resistance measured by high-frequency alternating current is the ohmic resistance in the cell, which does not include the polarization resistance and diffusion resistance of electrochemical reaction.
As shown in fig. 4, the S3 specifically includes:
s31, adjusting the charge state of the single batteries with the consistent internal resistance to SOC (state of charge) of 50%, respectively calculating the polarization voltage of each single battery with the consistent internal resistance through polarization test, and calculating the relative error of the polarization voltage of each single battery with the consistent internal resistance; the calculation principle of the relative error of the polarization voltage is the same as that of the standard capacity relative error, and only the object is changed into the polarization voltage.
S32, setting a fifth threshold value for the relative error of the polarization voltage, judging whether the polarization voltage error of each single battery with consistent internal resistance is within the fifth threshold value, reserving the single battery with the polarization voltage error within the fifth threshold value, and rejecting the single battery with the polarization voltage error not within the fifth threshold value; in this embodiment, the fifth threshold is set to 10%, and since the relative error or standard deviation of the polarization voltage is usually several times larger than the standard capacity and the ac internal resistance, that is, the polarization consistency is a more severe standard, and directly reflects whether the microscopic property difference related to the dynamics in the battery is within a certain range, 10% is selected as the fifth threshold (the fifth threshold is larger than the first and third thresholds).
S33, setting the polarization voltage relative error of the single battery with the polarization voltage relative error within the fifth threshold value to obey a third normal distribution, and setting a third confidence coefficient for the third normal distribution; in this particular embodiment, the third confidence level is set to 95%; the third normal distribution and the third confidence coefficient are the same as the first normal distribution and the first confidence coefficient of the standard capacity relative error, and only the statistical object is changed into the polarization voltage relative error.
S34, judging whether the relative error of the polarization voltage of the single battery with the relative error of the polarization voltage within the fifth threshold value is within the third confidence coefficient, if so, determining the single battery to be the single battery with consistent polarization, and reserving the single battery, otherwise, executing S35 to continue judging;
s35, setting a sixth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of the single battery within the fifth threshold value and outside the third confidence level is within the sixth threshold value, if so, determining the single battery to be a single battery with consistent polarization, reserving the single battery, otherwise, determining the single battery to be a single battery with inconsistent polarization, and rejecting the single battery; in the present embodiment, the sixth threshold is set to 5%.
In S31, the step of calculating the polarization voltage of each unit cell with the consistent internal resistance through the polarization test comprises the following steps,
s311, measuring the open-circuit voltage U of each single battery with consistent internal resistanceOCV；
S312, recording the 10 th second instantaneous voltage U after the discharge of each single battery 3C with consistent internal resistanceTThen, the polarization voltage U of each single battery with the same internal resistancep＝UOCV-UT。
In S31, the charge state of the battery cells having the same internal resistance is adjusted to have an SOC of 50%, and the battery cells having the same internal resistance are charged with half the standard capacity after the charge is discharged, and left to stand for 2 hours.
The method of the invention divides the consistency of the single batteries into capacity consistency, internal resistance consistency and polarization consistency, and the single batteries are qualified batteries with consistency which must meet the three consistency at the same time. During detection, the measurement is carried out in sequence according to the consistency of capacity, the consistency of alternating current internal resistance and the consistency of polarization, and the sequence cannot be reversed. Therefore, the consistency of the single batteries in the battery pack can be identified with high precision and quantification.
Based on the method for identifying the consistency of the monomers in the battery pack, the invention also provides a system for identifying the consistency of the monomers in the battery pack.
As shown in fig. 6, a system for identifying the uniformity of cells in a battery pack includes a capacity measuring module, an internal resistance measuring module and a polarization testing module,
the capacity measurement module is used for measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
the internal resistance measuring module is used for measuring alternating current internal resistance of each single battery with consistent capacity to obtain the single batteries with consistent alternating current internal resistance;
the polarization testing module is used for carrying out polarization testing on each single battery with consistent alternating current internal resistance to obtain the single batteries with consistent polarization, wherein the single batteries with consistent polarization are recognition results of single batteries in the battery pack.
The system for identifying the consistency of the single batteries in the battery pack divides the consistency of the battery pack into capacity consistency, internal resistance consistency and polarization consistency, and the single batteries are qualified in consistency only when the three consistency needs to be met simultaneously, so that the consistency of the single batteries in the battery pack can be identified in a high-precision and quantitative manner.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A method of identifying a uniformity of cells in a battery pack, comprising: comprises the following steps of (a) carrying out,
s1, measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
s2, measuring the internal resistance of each single battery with the consistent capacity to obtain the single batteries with the consistent internal resistance;
s3, carrying out polarization test on each single battery with consistent internal resistance to obtain single batteries with consistent polarization, wherein the single batteries with consistent polarization are recognition results of single batteries in the battery pack;
specifically, the step S1 is,
s11, respectively measuring the standard capacity of each single battery in the battery pack, and calculating the standard capacity relative error of each single battery;
s12, setting a first threshold value for the relative error of the standard capacity, judging whether the relative error of the standard capacity of each single battery in the battery pack is within the first threshold value, reserving the single batteries with the relative errors of the standard capacity within the first threshold value, and rejecting the single batteries with the relative errors of the standard capacity not within the first threshold value;
s13, setting the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value to be in accordance with a first normal distribution, and setting a first confidence coefficient for the first normal distribution;
s14, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value is within the first confidence coefficient, if so, determining the single battery to be the single battery with consistent capacity and reserving the single battery, otherwise, executing S15 to continue judging;
s15, setting a second threshold value for the standard capacity relative error, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value and outside the first confidence degree is within the second threshold value, if so, determining the single battery to be the single battery with consistent capacity, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent capacity, and rejecting the single battery;
specifically, the step S2 is,
s21, adjusting the charge state of the single batteries with the consistent capacity to be SOC (state of charge) 50%, respectively measuring the alternating current internal resistance of each single battery with the consistent capacity, and calculating the relative error of the alternating current internal resistance of each single battery with the consistent capacity;
s22, setting a third threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of each single battery with the consistent capacity is within the third threshold value, reserving the single batteries with the relative error of the alternating current internal resistance within the third threshold value, and simultaneously rejecting the single batteries with the relative error of the alternating current internal resistance not within the third threshold value;
s23, setting the alternating current internal resistance relative error of the single battery with the alternating current internal resistance relative error within the third threshold value to obey a second normal distribution, and setting a second confidence coefficient for the second normal distribution;
s24, judging whether the relative error of the alternating current internal resistance of the single battery with the relative error of the alternating current internal resistance within the third threshold value is within the second confidence coefficient, if so, determining the single battery to be the single battery with consistent internal resistance, and reserving the single battery, otherwise, executing S25 to continuously judge;
s25, setting a fourth threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of the single battery within the third threshold value and outside the second confidence level is within the fourth threshold value, if so, determining the single battery to be the single battery with consistent internal resistance, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent internal resistance, and rejecting the single battery;
specifically, the step S3 is,
s31, adjusting the charge state of the single batteries with the consistent internal resistance to SOC (state of charge) of 50%, respectively calculating the polarization voltage of each single battery with the consistent internal resistance through polarization test, and calculating the relative error of the polarization voltage of each single battery with the consistent internal resistance;
s32, setting a fifth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of each single battery with consistent internal resistance is within the fifth threshold value, reserving the single batteries with the relative error of the polarization voltage within the fifth threshold value, and rejecting the single batteries with the relative error of the polarization voltage not within the fifth threshold value;
s33, setting the polarization voltage relative error of the single battery with the polarization voltage relative error within the fifth threshold value to obey a third normal distribution, and setting a third confidence coefficient for the third normal distribution;
s34, judging whether the relative error of the polarization voltage of the single battery with the relative error of the polarization voltage within the fifth threshold value is within the third confidence coefficient, if so, determining the single battery to be the single battery with consistent polarization, and reserving the single battery, otherwise, executing S35 to continue judging;
s35, setting a sixth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of the single battery within the fifth threshold value and outside the third confidence level is within the sixth threshold value, if so, determining the single battery to be a single battery with consistent polarization, reserving the single battery, otherwise, determining the single battery to be a single battery with inconsistent polarization, and rejecting the single battery;
in S31, the step of calculating the polarization voltage of each unit cell with the consistent internal resistance through the polarization test comprises the following steps,
s311, measuring the open-circuit voltage U of each single battery with consistent internal resistanceOCV；
S312, recording the 10 th second instantaneous voltage U after the discharge of each single battery 3C with consistent internal resistanceTThen, the polarization voltage U of each single battery with the same internal resistancep＝UOCV-UT。
2. The method of claim 1, wherein the method further comprises the steps of: the number N of the single batteries in the battery pack is more than or equal to 40, and the type, specification and appearance of each single battery in the battery pack are consistent.
3. The method of claim 1, wherein the method further comprises the steps of: in S21, the state of charge of the cells having the same capacity is adjusted to have an SOC of 50%, and the cells having the same capacity are discharged, charged to an amount of half the standard capacity, and left to stand for 2 hours.
4. A method of identifying a correspondence of cells in a battery pack according to claim 3, wherein: the alternating current internal resistance is an internal ohmic resistance obtained by measuring the current and the voltage drop of the single batteries with consistent capacity by adopting alternating current with the frequency of more than 1000 Hz.
5. The method of any one of claims 1 to 4, wherein the method comprises the steps of: in S31, the charge state of the battery cells having the same internal resistance is adjusted to have an SOC of 50%, and the battery cells having the same internal resistance are charged with half the standard capacity after the charge is discharged, and left to stand for 2 hours.
6. A system for identifying a uniformity of cells in a battery pack, comprising: comprises a capacity measuring module, an internal resistance measuring module and a polarization testing module,
the capacity measurement module is used for measuring the capacity of each single battery in the battery pack to obtain single batteries with consistent capacity;
the internal resistance measuring module is used for measuring alternating current internal resistance of each single battery with consistent capacity to obtain the single batteries with consistent alternating current internal resistance;
the polarization testing module is used for carrying out polarization testing on each single battery with consistent alternating current internal resistance to obtain single batteries with consistent polarization, wherein the single batteries with consistent polarization are recognition results of single batteries in the battery pack;
the capacity measurement module is particularly adapted to,
respectively measuring the standard capacity of each single battery in the battery pack, and calculating the standard capacity relative error of each single battery;
setting a first threshold value for the relative error of the standard capacity, judging whether the relative error of the standard capacity of each single battery in the battery pack is within the first threshold value, reserving the single batteries with the relative error of the standard capacity within the first threshold value, and simultaneously rejecting the single batteries with the relative error of the standard capacity not within the first threshold value;
setting the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value to be in accordance with a first normal distribution, and setting a first confidence coefficient for the first normal distribution;
judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value is within the first confidence coefficient, if so, determining the single battery to be the single battery with consistent capacity, reserving the single battery, and if not, continuing to judge;
setting a second threshold value for the standard capacity relative error, judging whether the standard capacity relative error of the single battery with the standard capacity relative error within the first threshold value and outside the first confidence degree is within the second threshold value, if so, determining the single battery to be the single battery with consistent capacity, reserving the single battery, otherwise, determining the single battery to be the single battery with inconsistent capacity, and rejecting the single battery;
the internal resistance measuring module is specifically used for,
adjusting the charge state of the single batteries with the consistent capacity to be SOC (state of charge) 50%, respectively measuring the alternating current internal resistance of each single battery with the consistent capacity, and calculating the relative error of the alternating current internal resistance of each single battery with the consistent capacity;
setting a third threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of each single battery with the consistent capacity is within the third threshold value, reserving the single batteries with the relative error of the alternating current internal resistance within the third threshold value, and simultaneously rejecting the single batteries with the relative error of the alternating current internal resistance not within the third threshold value;
setting the alternating current internal resistance relative error of the single battery with the alternating current internal resistance relative error within the third threshold value to obey a second normal distribution, and setting a second confidence coefficient for the second normal distribution;
judging whether the alternating current internal resistance relative error of the single battery with the alternating current internal resistance relative error within the third threshold value is within the second confidence coefficient, if so, determining the single battery to be the single battery with consistent internal resistance, reserving the single battery, and if not, continuously judging;
setting a fourth threshold value for the relative error of the alternating current internal resistance, judging whether the relative error of the alternating current internal resistance of the single battery within the third threshold value and outside the second confidence level is within the fourth threshold value, if so, determining the single battery to be the single battery with consistent internal resistance, reserving the single battery, and if not, determining the single battery to be the single battery with inconsistent internal resistance, and rejecting the single battery;
the polarization testing module is particularly useful for,
adjusting the charge state of the single batteries with the consistent internal resistance to be SOC (state of charge) 50%, respectively calculating the polarization voltage of each single battery with the consistent internal resistance through polarization testing, and calculating the polarization voltage relative error of each single battery with the consistent internal resistance;
setting a fifth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of each single battery with consistent internal resistance is within the fifth threshold value, reserving the single batteries with the relative error of the polarization voltage within the fifth threshold value, and simultaneously rejecting the single batteries with the relative error of the polarization voltage not within the fifth threshold value;
setting the relative error of the polarization voltage of the single battery with the relative error of the polarization voltage within the fifth threshold value to obey a third normal distribution, and setting a third confidence coefficient for the third normal distribution;
judging whether the relative error of the polarization voltage of the single battery with the relative error of the polarization voltage within the fifth threshold value is within the third confidence coefficient, if so, determining the single battery to be the single battery with consistent polarization, and reserving the single battery, otherwise, continuing to judge;
setting a sixth threshold value for the relative error of the polarization voltage, judging whether the relative error of the polarization voltage of the single battery within the fifth threshold value and outside the third confidence level is within the sixth threshold value, if so, determining the single battery to be the single battery with consistent polarization, reserving the single battery, otherwise, determining the single battery to be the single battery with inconsistent polarization, and rejecting the single battery;
the method for respectively calculating the polarization voltage of each single battery with consistent internal resistance through polarization test comprises the following steps of measuring the open-circuit voltage U of each single battery with consistent internal resistanceOCV(ii) a Recording the 10 th second instantaneous voltage U after the discharge of each single battery 3C with the same internal resistanceTThen, the polarization voltage U of each single battery with the same internal resistancep＝UOCV-UT。
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