CN110031770B - Method for rapidly obtaining capacity of all single batteries in battery pack - Google Patents

Method for rapidly obtaining capacity of all single batteries in battery pack Download PDF

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CN110031770B
CN110031770B CN201910353661.5A CN201910353661A CN110031770B CN 110031770 B CN110031770 B CN 110031770B CN 201910353661 A CN201910353661 A CN 201910353661A CN 110031770 B CN110031770 B CN 110031770B
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battery
charging
curve
characteristic value
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CN110031770A (en
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刘中财
王东征
严晓
黄碧雄
马非凡
丁家宝
郭海龙
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Shanghai MS Energy Storage Technology Co Ltd
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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]
    • G01R31/385—Arrangements for measuring battery or accumulator variables
    • G01R31/387—Determining ampere-hour charge capacity or SoC
    • G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
    • 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]
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Abstract

The invention relates to a method for rapidly obtaining the capacity of all single batteries in a battery pack, which comprises the following steps: s1, obtainingTarget battery reference curve data and battery nominal capacity Capinitial(ii) a S2, processing the battery reference curve data, and recording the capacity or charging capacity of the battery at the characteristic value position; s3, calculating a relation coefficient between the capacity and the total capacity among the characteristic values of the batteries; s4, processing the battery pack charging curve, and recording the charging capacity of the battery at the characteristic value position; and S5, calculating the capacities among the battery characteristic values obtained in the step S4, and calculating the capacities of all the single batteries in the battery pack one by one according to the relation coefficient in the step S3. The method is applicable to the normal charging process of the battery pack, does not influence the work input and output of the battery, only needs to acquire the SOC-OCV curve data of the battery or a historical charging curve and the nominal capacity of the battery in advance, does not need to additionally test battery parameters, and can obtain the total capacity of all single batteries in the battery pack in real time.

Description

Method for rapidly obtaining capacity of all single batteries in battery pack
Technical Field
The invention relates to a method for quickly obtaining the capacity of all single batteries in a battery pack.
Background
The invention relates to the capacity of all single batteries in a battery pack, in particular to the capacity of all single batteries in a battery pack formed by connecting a plurality of single batteries in series. Lithium ion batteries have been widely used in the fields of electric vehicles, electrochemical energy storage, 3C electronic products, and the like, because of their advantages of high energy, high battery voltage, wide operating temperature range, long storage life, and the like. The effective capacity of the battery is related to the continuous working time of the battery, the resistance value of the battery is closely related to the instant charging and discharging capacity of the battery, and in addition, in the battery packs which are connected in series into a group, the capacity distribution of the single batteries is closely related to the consistency of the battery packs.
The capacity of a lithium ion battery is one of important performance indexes for measuring the performance of the battery, and it represents the amount of electricity discharged by the battery (JS-150D can be used for discharge test) under certain conditions (discharge rate, temperature, end voltage, etc.), that is, the capacity of the battery is usually expressed in ampere-hour units (abbreviated as a · H, 1A · H is 3600C). In the lithium ion battery in the actual use process, the situation that the battery is fully charged and discharged basically does not exist, and the total capacity of the battery is difficult to know, so that the estimation of the battery and the nuclear power State (SOC) is influenced, the accurate real-time calculation of the capacity of the battery is realized, and the lithium ion battery has important significance for the safety management of the battery.
The invention discloses a Chinese patent (patent number: CN109342955A, patent name: a method and a system for calculating the capacity of a lithium ion battery). according to the method, the discharge capacity of the lithium ion battery at the experimental temperature is obtained by performing discharge tests on the lithium ion battery at n experimental temperatures, a model is established by combining an Arrhenius formula, and the battery capacity value at any temperature point is calculated. The method needs n discharge tests in advance, is complex to operate, can only calculate the capacity value of the battery at different temperatures, cannot accurately calculate the capacity value of the battery after aging, and is poor in practicability.
The invention discloses a Chinese patent (patent number: CN 108152747A, patent name: detection method and device of storage battery capacity), which is characterized in that the method comprises the steps of obtaining a measured value of a storage battery discharge parameter of a wind generating set in the process of supplying power and changing the pitch by using the storage battery; and detecting the current capacity of the storage battery according to the measured value and a functional relation constructed by the storage battery test by utilizing the discharge parameters. The method needs to carry out a large number of storage battery tests before use to construct a relational database of measured values and battery capacity, calculates the required measured values by capturing appropriate discharge parameters in the actual use process, and evaluates the current capacity of the storage battery by searching the corresponding capacity in the database prepared in advance. The method needs to establish a relational database in advance, and has troublesome actual application and high cost; and due to the nonlinear characteristic of the battery, in the implementation process, whether the corresponding relation between the capacity of the storage battery and the corresponding measured value is established or not is judged, and the accuracy of the result is lack of data support.
The invention patent of China (patent number: CN108732508, patent name: a real-time estimation method of lithium ion battery capacity) obtains a charging data-real-time capacity VS voltage curve in a standard capacity test through a battery durability test, and then performs data fitting on the curve for difference. The peak position and the size in the difference result curve have correlation with the residual capacity of the battery, and the battery capacity can be estimated by comparing the difference curve in the initial condition and the certain time condition. The method requires a durability test for the battery, and the method has poor practical operability; the peak value of the difference result curve is related to a data screening processing method, and the error is large.
Chinese patent (patent No. CN109031153, patent name: a method for estimating the state of health of lithium ion battery online), this method passes the test of short-term cycle life, as the initial parameter of model training, utilize the capacity increment analysis method, extract a plurality of characteristic parameters from the curve of capacity increment, form the characteristic parameter set, carve the state of health of the battery, and regard the value of the characteristic parameter as the model output of the regression model method of the multiple output Gaussian process, finish the online assessment to the capacity of the battery. The method needs to carry out cycle life test, and practical application has difficulty.
Disclosure of Invention
The invention aims to provide a method for calculating the capacity value of all single batteries in a battery pack in real time by extracting characteristic value parameters after processing based on a charging curve in the normal work of the batteries and substituting the characteristic value parameters into a model for calculation.
The purpose of the invention can be realized by the following technical scheme:
a method for rapidly obtaining the capacity of all single batteries in a battery pack comprises the following steps:
s1, aiming at the target lithium ion battery, acquiring battery reference curve data and battery nominal capacity Capinitial；
S2, processing the lithium ion battery reference curve data, and recording the capacity or charging capacity of the battery at the characteristic value position;
s3, calculating a relation coefficient between the capacity and the total capacity among the characteristic values of the batteries;
s4, processing the battery pack charging curve, and recording the charging capacity of the battery at the characteristic value position;
and S5, calculating the capacities among the battery characteristic values obtained in the step S4, and calculating the capacities of all the single batteries in the battery pack one by one according to the relation coefficient in the step S3.
The battery reference curve data in step S1 may be battery SOC-OCV curve data obtained from a manufacturer, or may be historical charging curve data.
In step S2, the processing is performed on the lithium ion battery reference curve data, and the capacity or the charging capacity of the battery at the characteristic value position is recorded: according to the type of the battery material, data with SOC greater than 20% are obtained for the lithium iron phosphate battery, a capacity increment curve is obtained, and the calculation formula is
Figure BDA0002044723140000031
Extracting a characteristic value, wherein the position of the characteristic value is the maximum position in the capacity increment curve, and recording the capacity Q or the charging capacity Q' corresponding to the position of the characteristic value; for ternary material battery, data with SOC greater than 20% is taken to obtain d2Q/dV2Curve, the calculation formula is
Figure BDA0002044723140000032
Extracting the feature value, the position of the feature value is
Figure BDA0002044723140000033
And recording the capacity Q or the charging capacity Q' corresponding to the characteristic value position; q ═ SOC Capinitial；
Wherein: q is the battery capacity, Q' is the charge capacity, dQ is the differential of the capacity, d2Q is the second differential of the capacity, Δ QkIs the difference in capacity between adjacent samples, V is the voltage of the cell, dV is the differential of the voltage, dV2Is the second order differential of the voltage, Δ VkIs adjacent toDifference in voltage between sampling points, Δ Q, for each sampling point kk＝Qk-Qk-1，ΔVk＝Vk-Vk-1，ΔQk-1＝Qk-1-Qk-2，ΔVk-1＝Vk-1-Vk-2。
Wherein, the characteristic value of the battery reference curve has 2, namely a first characteristic value and a second characteristic value, and the capacity Q of the 1 st characteristic value position is recorded1Or charging capacity Q'1Capacity Q of the 2 nd eigenvalue position2Or charging capacity Q'2。
In step S3, a coefficient g of the relationship between the capacity and the total capacity between the battery characteristic values is calculated as Δ Q/Capinitial(ii) a Where Δ Q is the capacity difference between the 1 st characteristic value and the 2 nd characteristic value, Δ Q ═ Q2-Q1L, |; if historical charging curve data is employed, then Δ Q ═ Q'2-Q‘1|。
Wherein, the step S4 is to process the battery pack charging curve, and the recording of the battery charging capacity at the characteristic value position specifically includes: and extracting data meeting the condition that delta V is larger than or equal to X in the charging process of the battery pack. According to the type of a battery material, data with SOC greater than 20% are taken for the lithium iron phosphate battery, a capacity increment analysis method is utilized, a characteristic value is extracted from a capacity increment curve, and the charging capacity corresponding to the position of the characteristic value is recorded; for ternary material battery, data with SOC greater than 20% is taken to obtain d2Q/dV2A curve, extracting a characteristic value and recording the charging capacity corresponding to the position of the characteristic value; the charging capacity corresponding to the characteristic value comprises a charging capacity Q 'of the 1 st characteristic value position'1jAnd a charging capacity Q 'of the 2 nd characteristic value position'2jWherein: q1jThe j number of the single battery capacity, Q, of the 1 st characteristic value position2jIs the No. 2 characteristic value position j single battery capacity, Q'1jIs the charging capacity of the monomer of No. j of the 1 st characteristic value position, Q'2jThe charge capacity of the No. j cell at the No. 2 characteristic value position.
Wherein the step of S5 calculates the capacity between the characteristic values of the batteries obtained in the step of S4, and performs the calculation according to the characteristic values of the batteries obtained in the step of S3The specific calculation of the capacities of all the single batteries in the battery pack is as follows: calculating the capacity difference between the 1 st characteristic value and the 2 nd characteristic value of the j single battery, namely delta Qj＝|Q2j-Q1j|＝|Q‘2j-Q‘1jAccording to the formula Capj＝ΔQjThe capacity of the j single battery is obtained, and then the capacities of other single batteries in the battery pack are calculated one by one; wherein, CapjThe j-th unit cell capacity g is a coefficient of the relationship between the capacity and the total capacity between the characteristic values of the battery obtained in claim 5.
Wherein the value range of X is more than or equal to 1mV and less than or equal to 10 mV.
The charging curve of the battery pack may be the last charging curve, or may be a last charging curve extracted from the last 10 charging curves and combined with the last charging curve, so that a curve including 2 characteristic value points is formed.
The method comprises the following steps of extracting a charging curve from the charging curve of the last 10 times and combining the charging curve with the last time, firstly selecting a curve which has the same charging current as the charging current of the curve of the last time and has an environmental temperature difference smaller than 5 degrees from the charging curve of the last 10 times, then selecting a curve which can be combined with the curve of the last time to form a curve comprising two characteristic value position curves from the rest curves, and if a plurality of curves meet requirements, preferentially selecting the curve with the closest environmental temperature; if the ambient temperature is the same, the most recent charging profile, i.e. the profile closest in time to the last charging, is preferably selected.
The invention has the beneficial effects that: 1. the method is applicable to the normal charging process of the battery pack, and does not influence the working input and output of the battery; 2. the method only needs to acquire the SOC-OCV curve data of the battery or a historical charging curve and the nominal capacity of the battery in advance, and does not need to additionally test battery parameters; 3. the total capacity of all the single batteries in the battery pack can be obtained in real time; 4. the total capacity of all the single batteries can be obtained without fully charging the batteries.
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FIG. 1 is a flow chart of the present invention;
FIG. 2 is a capacity increment curve for a lithium iron phosphate lithium ion battery reference curve;
FIG. 3 is a graph of capacity increase for lithium iron phosphate lithium ion battery charging data;
FIG. 4 is a capacity increment curve and d for a ternary lithium ion battery reference curve2Q/dV2A curve;
FIG. 5 is a capacity increment curve for ternary lithium ion battery charging data and d2Q/dV2A curve;
FIG. 6 is a histogram of the capacities of all the cells in the battery pack;
FIG. 7 is a graph of the error of the calculated capacity versus the true capacity of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
As shown in fig. 1, a method for rapidly obtaining the capacity of all the single batteries in a battery pack, the middle battery of the battery pack may be a lithium iron phosphate battery or a ternary material battery; the battery pack can be a battery pack system formed by connecting a plurality of battery cells in parallel and then in series. Acquiring battery reference curve data and battery nominal capacity Cap aiming at a target lithium ion batteryinitial. The lithium ion battery reference curve data can be battery SOC-OCV curve data obtained from a manufacturer, and can also be historical charging curve data. The SOC-OCV curve data of the battery is obtained from a manufacturer, and the SOC value density is between 0.1% and 5%, including 0.1% and 5%. Processing curve data, extracting a characteristic value from a capacity increment curve by using a capacity increment analysis method according to the type of a battery material and taking data with SOC (State of Charge) more than 20% of the lithium iron phosphate battery, and recording a capacity Q or a charging capacity Q' corresponding to the position of the characteristic value; for ternary material battery, data with SOC greater than 20% is taken to obtain d2Q/dV2And (5) extracting a characteristic value and recording the capacity Q or the charging capacity Q' corresponding to the position of the characteristic value by a curve. Q ═ SOC Capinitial。
Processing the data of a reference curve of the lithium iron phosphate battery, and obtaining a capacity increment curve with SOC as an abscissa, wherein the calculation formula is
Figure BDA0002044723140000051
Extracting a characteristic value, wherein the position of the characteristic value is the position of the maximum value in the capacity increment curve; processing the data of the reference curve of the ternary battery to obtain d with the voltage as the abscissa2Q/dV2Curve, the calculation formula is
Figure BDA0002044723140000052
Extracting the feature value, the position of the feature value is
Figure BDA0002044723140000053
Figure BDA0002044723140000054
The position of (a). For lithium iron phosphate or ternary batteries, in the interval of which the SOC is more than 20% and less than 100%, the characteristic values of the curves are all 2. Capacity Q for recording the 1 st eigenvalue position1Or charging capacity Q'1Capacity Q of the 2 nd eigenvalue position2Or charging capacity Q'2. Wherein: q is the battery capacity, Q' is the charge capacity, dQ is the differential of the capacity, d2Q is the second differential of the capacity, Δ QkIs the difference in capacity between adjacent samples, V is the voltage of the cell, dV is the differential of the voltage, dV2Is the second order differential of the voltage, Δ VkFor the difference in voltage between adjacent samples, Δ Q for each sample point kk＝Qk-Qk-1，ΔVk＝Vk-Vk-1，ΔQk-1＝Qk-1-Qk-2，ΔVk-1＝Vk-1-Vk-2；
Calculating the relation coefficient of the capacity and the total capacity between the characteristic values of the battery, wherein g is delta Q/Capinitial(ii) a Where Δ Q is the capacity difference between the 1 st characteristic value and the 2 nd characteristic value, Δ Q ═ Q2-Q1L, |; if historical charging curve data is employed, then Δ Q ═ Q'2-Q‘1|。
And extracting data meeting the condition that delta V is larger than or equal to X in the charging process of the battery pack. The data includes voltage values of all single batteries, and the batteriesThe charge time of the pack and the charge capacity value of the battery pack, etc. The value range of X is more than or equal to 1mV and less than or equal to 10 mV. According to the type of a battery material, data with SOC greater than 20% are taken for the lithium iron phosphate battery, a capacity increment analysis method is utilized, a characteristic value is extracted from a capacity increment curve, and the charging capacity corresponding to the position of the characteristic value is recorded; for ternary material battery, data with SOC greater than 20% is taken to obtain d2Q/dV2And (5) a curve, extracting the characteristic value and recording the charging capacity corresponding to the position of the characteristic value. Recording charging capacity Q 'of 1 st characteristic value position of all battery curves'1jRecording the charging capacity Q 'of the 2 nd characteristic value position of all the cell curves'2jWherein: q1jThe j number of the single battery capacity, Q, of the 1 st characteristic value position2jIs the No. 2 characteristic value position j single battery capacity, Q'1jIs the charging capacity of the monomer of No. j of the 1 st characteristic value position, Q'2jThe charge capacity of the No. j cell at the No. 2 characteristic value position.
Calculating the capacity difference between the 1 st characteristic value and the 2 nd characteristic value of the j single battery, namely delta Qj＝|Q2j-Q1j|；ΔQjAlso equal to the 1 st to 2 nd eigenvalue charge capacity. If a charging curve contains both the 1 st and 2 nd characteristic values, Δ Qj＝|Q‘2j-Q‘1jL. If the single charging curve does not contain two characteristic value positions, the charging curve can be extracted from the charging curve of the last 10 times and combined with the last time to form a curve containing 2 characteristic value points. The two combined curves should meet the requirement that the charging current is the same and the temperature difference of the charging environment is less than 5 degrees, otherwise, the two curves are not combined.
And (3) calculating the total capacity corresponding to the j-th single battery, wherein the calculation formula is as follows:
Capj＝ΔQj/g；
and calculating the capacity of each single battery in the battery pack one by one.
Example 1:
the target lithium ion battery is a CATL lithium iron phosphate battery with a nominal capacity of CapinitialThe battery reference curve data is SOC-OCV relationship curve data at 180Ah, and the data interval is Δ SOC of 2%. The capacity value corresponding to each OCV point is represented by the formula: q ═ SOC 180 is calculated;
obtaining a capacity increment curve of SOC-OCV relation data by adopting a five-point cubic smoothing filtering method (2 data before and after the position to be subjected to smoothing filtering are selected, the total number of the data is 5, a 3-order polynomial is adopted for fitting, and the numerical value after smoothing filtering is obtained), wherein the obtained capacity increment curve is shown as a dQ/dV point drawing line in figure 2, the figure 2 takes SOC as an abscissa, the left ordinate is battery open-circuit voltage OCV, the right ordinate is dQ/dV, the 1 st characteristic value position is an A point position in figure 2, the corresponding SOC is 55.6 percent, and the capacity Q is Q1The 2 nd eigenvalue position in the graph is the B point position in fig. 2, corresponding to an SOC of 84.9%, at 100.08Ah, and the capacity Q2＝152.82Ah；
Calculating a relation coefficient of capacity and total capacity between the characteristic values of the batteries:
g＝ΔQ/Capinitial＝|Q2-Q1|/Capinitial＝(152.82-100.08)/180＝0.293
the charging data condition of fig. 3 is that the battery pack performs constant current charging with a current of 0.35C, 63A until the voltage of any single battery reaches 3.6V, i.e. stops charging, and the SOC of the battery pack in the early stage of charging is 20%.
The charging data is extracted under the condition that the delta V is more than or equal to 2mV, and the voltage value and the charging electric quantity value of each single battery are extracted. Obtaining a capacity increment curve by adopting a five-point triple smoothing filter method for the voltage value and the charging electric quantity value of the battery, wherein the capacity increment curve of the No. 1 single battery in the battery pack is shown in fig. 3, the SOC is taken as an abscissa in fig. 3, the left ordinate is the battery voltage, the right ordinate is dQ/dV, the 1 st characteristic value position in the diagram is the C point position in fig. 3, and the corresponding charging capacity value is Q'1167.66Ah, the 2 nd eigenvalue position in the figure is the D point position in figure 3, and the corresponding charge capacity value is Q'21＝119.2Ah；
And (3) calculating the total capacity of the No. 1 single battery of the battery pack:
Cap1＝ΔQ1/g＝|Q‘21-Q‘11|/g＝(119.2-67.06)/0.293＝177.9Ah
the same calculation method calculates the total capacity of the number 2 single battery in the battery pack to the total capacity of the number 240 single battery, and draws the total capacity of all the single batteries into a histogram, and fig. 6 is a histogram of the capacity of all the single batteries in the battery pack.
And comparing the capacity value calculated by the method of the present invention with the real capacity value of the battery, the capacity error rate is shown in fig. 7, which shows that the maximum capacity error is 3.86%.
Example 2:
the target lithium ion battery is a 21700 ternary battery with nominal capacity of CapinitialThe battery reference curve data used was SOC-OCV curve data at 4.5Ah, and the data interval was Δ SOC of 3%. The capacity value corresponding to each OCV point is represented by the formula: q ═ SOC 4.5 was calculated;
solving a capacity increment curve and d of SOC-OCV relation data by adopting a five-point three-time smoothing filtering method2Q/dV2The resulting capacity increase curve is shown in dotted dQ/dV in FIG. 4, d2Q/dV2The curve is shown by the dotted line in FIG. 4, where FIG. 4 is the open circuit voltage OCV on the abscissa, the left ordinate is the battery SOC, the right 1 st ordinate is dQ/dV, and the right 2 nd ordinate is d2Q/dV2In the figure, the 1 st eigenvalue position is the E point position in figure 4, corresponding to the SOC value of 39.8%, the capacity Q1When the value is 1.791Ah, the 2 nd eigenvalue position in the graph is the F point position in fig. 4, corresponding to the SOC value of 76.4%, and the capacity Q2＝3.438Ah；
Calculating a relation coefficient of capacity and total capacity between the characteristic values of the batteries:
g＝ΔQ/Capinitial＝|Q2-Q1|/Capinitial＝(3.438-1.791)/4.5＝0.336
the target lithium ion battery is charged with a constant current of 1C and 4.5A until the voltage reaches 4.2V, and the charging is stopped, wherein the SOC of the battery pack in the early stage of charging is 15%.
The charging data is extracted under the condition that the delta V is more than or equal to 3mV, and the voltage value and the charging electric quantity value of the battery are extracted. The capacity increment curve and d are obtained by adopting a five-point triple smoothing filtering method for the voltage value and the charging electric quantity value2Q/dV2Curve, capacity increment curve of charge data of the battery and d2Q/dV2The graph is shown in FIG. 5, where FIG. 5 is the voltage on the abscissa, the left ordinate is the battery SOC, the right 1 st ordinate is dQ/dV, and the right 2 nd ordinate is d2Q/dV2Where the 1 st eigenvalue position in the figure is the H point position in figure 5, and the corresponding charge capacity value is Q'110.945Ah, the 2 nd eigenvalue position in the figure is the M point position in figure 5, and the corresponding charge capacity value is Q'21＝2.601Ah；
And (3) calculating the total capacity of the No. 1 single battery of the battery pack:
Cap1＝ΔQ1/g＝|Q‘21-Q‘11|/g＝(2.443-0.945)/0.336＝4.46Ah
the total capacity of other single batteries in the battery pack is calculated by the same calculation method.
Example 3:
the target lithium ion battery is a soft package ternary battery of the high department of the Xuan, 15Ah is connected in series after being connected in parallel, and the nominal capacity is CapinitialThe battery reference curve data is historical curve data, the charging current is 6A, and the data extraction condition is that delta V is more than or equal to 5 mV;
obtaining a capacity increment curve and d of historical charging curve data by adopting a five-point three-time smoothing filtering method2Q/dV2Curve, and with charging voltage as abscissa, left ordinate is battery SOC, right 1 st ordinate is dQ/dV, right 2 nd ordinate is d2Q/dV2Calculating the charging capacity Q 'corresponding to the 1 st characteristic value position'116.53Ah, and a charging capacity Q 'corresponding to the 2 nd characteristic value position'2＝26.13Ah；
Calculating a relation coefficient of capacity and total capacity between the characteristic values of the batteries:
g＝ΔQ/Capinitial＝|Q‘2-Q‘1|/Capinitial＝(26.13-16.53)/30＝0.32
the battery pack assembled by the target lithium ion battery is formed by connecting 2 batteries and 16 batteries in series, the target lithium ion battery is charged at constant current of 0.5C and 15A until the voltage of any single battery reaches 4.2V, the charging is stopped, and the SOC of the battery pack in the early stage of charging is 13%.
The charging data is extracted under the condition that the delta V is more than or equal to 1mV, the voltage value and the charging electric quantity value of each single battery are extracted, and after the charging is finished, the data with the SOC less than 15 percent are removed. Obtaining a capacity increment curve and d by adopting a five-point triple smoothing filtering method for the voltage value and the charging electric quantity value of each single battery2Q/dV2Recording the charging capacity value of the 1 st characteristic value position and the charging capacity value of the 2 nd characteristic value position of each single battery, wherein the 1 st characteristic value position of the No. 1 single battery corresponds to the charging capacity value of Q'110.945Ah, and the charge capacity value corresponding to the 2 nd unique value position is Q'21＝2.601Ah；
And (3) calculating the total capacity of the No. 1 single battery in the battery pack:
Cap1＝ΔQ1/g＝|Q‘21-Q‘11|/g＝(21.56-11.576)/0.32＝31.2Ah
the total capacity from the No. 2 single battery to the No. 16 single battery in the battery pack is calculated by the same calculation method.
Example 4:
embodiment 4 is similar to embodiment 3, except that, when processing the charging curve, the single charging curve does not include two characteristic value positions, so the charging curve is extracted from the charging curve of the last 10 times and combined with the last time to form a curve including 2 characteristic value points. Firstly, selecting a curve which is the same as the charging current of the last curve in the last 10 charging curves and has the difference of the environmental temperature less than 5 degrees, selecting a curve which can be combined into a curve containing two characteristic value position curves from the last curve, and preferentially selecting the curve with the closest environmental temperature if a plurality of curves meet the requirement; if the ambient temperature is the same, the most recent charging profile (i.e., the profile closest in time to the last charge) is preferably selected. The data extraction conditions may be data for conditions where Δ V is greater than or equal to 10 mV. And calculating the capacity of the single batteries in the battery pack one by using the formula.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (7)

1. A method for rapidly obtaining the capacity of all single batteries in a battery pack is characterized in that: comprises the following steps:
s1, aiming at the target lithium ion battery, acquiring battery reference curve data and battery nominal capacity Capinitial；
S2, processing the lithium ion battery reference curve data, and recording the capacity or charging capacity of the battery at the characteristic value position;
s3, calculating a relation coefficient between the capacity and the total capacity among the characteristic values of the batteries;
s4, processing the battery pack charging curve, and recording the charging capacity of the battery at the characteristic value position;
s5, calculating the capacities among the characteristic values of the batteries obtained in the step S4, calculating the capacities of all the single batteries in the battery pack one by one according to the relation coefficient in the step S3,
in step S2, the lithium ion battery reference curve data is processed, and the capacity or charging capacity of the battery at the characteristic value position is recorded: according to the type of the battery material, data with SOC greater than 20% are obtained for the lithium iron phosphate battery, a capacity increment curve with SOC as a horizontal coordinate is obtained, and a calculation formula is
Figure FDA0003136451280000011
Extracting a characteristic value, wherein the position of the characteristic value is the maximum position in the capacity increment curve, and recording the capacity Q or the charging capacity Q' corresponding to the position of the characteristic value; for the ternary material battery, the data with SOC greater than 20% is taken to obtain d with voltage as abscissa2Q/dV2Curve, the calculation formula is
Figure FDA0003136451280000012
Extracting the feature value, the position of the feature value is
Figure FDA0003136451280000013
And recording the capacity Q or the charging capacity Q' corresponding to the characteristic value position; q ═ SOC Capinitial；
Wherein: q is the battery capacity, Q' is the charge capacity, dQ is the differential of the capacity, d2Q is the second differential of the capacity, Δ QkIs the difference in capacity between adjacent samples, V is the voltage of the cell, dV is the differential of the voltage, dV2Is the second order differential of the voltage, Δ VkFor the difference in voltage between adjacent samples, Δ Q for each sample point kk＝Qk-Qk-1，ΔVk＝Vk-Vk-1，ΔQk-1＝Qk-1-Qk-2，ΔVk-1＝Vk-1-Vk-2，
The characteristic values of the battery reference curve are 2, namely a first characteristic value and a second characteristic value, and the capacity Q of the 1 st characteristic value position is recorded1Or charging capacity Q'1Capacity Q of the 2 nd eigenvalue position2Or charging capacity Q'2，
In step S3, a coefficient of relationship g ═ Δ Q/Cap between the capacity and the total capacity between the battery characteristic values is calculatedinitial(ii) a Where Δ Q is the capacity difference between the 1 st characteristic value and the 2 nd characteristic value, Δ Q ═ Q2-Q1L, |; if historical charging curve data is employed, then Δ Q ═ Q'2-Q‘1|。
2. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 1, wherein: the battery reference curve data in step S1 is battery SOC-OCV curve data obtained from a manufacturer, or historical charging curve data.
3. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 1, wherein: step S4 is to process the battery pack charging curve, and recording the battery charging capacity at the characteristic value position specifically includes: extracting data meeting the condition that delta V is larger than or equal to X in the charging process of a battery pack, taking data with SOC larger than 20% for a lithium iron phosphate battery according to the type of a battery material, extracting a characteristic value through a capacity increment curve taking SOC as an abscissa, and recording the charging capacity corresponding to the position of the characteristic value; for the ternary material battery, the data with SOC greater than 20% is taken to obtain d with voltage as abscissa2Q/dV2A curve, extracting a characteristic value and recording the charging capacity corresponding to the position of the characteristic value; the charging capacity corresponding to the characteristic value comprises a charging capacity Q 'of the 1 st characteristic value position'1jAnd a charging capacity Q 'of the 2 nd characteristic value position'2jWherein: q1jThe j number of the single battery capacity, Q, of the 1 st characteristic value position2jIs the No. 2 characteristic value position j single battery capacity, Q'1jIs the charging capacity of the monomer of No. j of the 1 st characteristic value position, Q'2jThe charge capacity of the No. j cell at the No. 2 characteristic value position.
4. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 3, wherein: the step S5 is to calculate the capacities among the battery characteristic values obtained in the step S4, and calculate the capacities of all the single batteries in the battery pack one by one according to the relationship coefficient in the step S3, specifically: calculating the capacity difference between the 1 st characteristic value and the 2 nd characteristic value of the j single battery, namely delta Qj＝|Q2j-Q1j|＝|Q‘2j-Q‘1jAccording to the formula Capj＝ΔQjThe capacity of the No. j single battery is obtained by/g and then is counted one by oneCalculating the capacities of other single batteries in the battery pack; wherein, CapjThe j-th unit battery capacity g is a coefficient of the relationship between the capacity and the total capacity between the characteristic values of the battery obtained in claim 1.
5. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 3, wherein: the value range of X is more than or equal to 1mV and less than or equal to 10 mV.
6. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 3, wherein: the charging curve of the battery pack is the charging curve of the latest time, or the charging curve is extracted from the charging curves of the latest 10 times and combined with the latest time, so that the charging curve becomes a curve containing 2 characteristic value points.
7. The method for rapidly obtaining the capacity of all the single batteries in the battery pack according to claim 6, wherein: extracting a charging curve from the charging curves of the last 10 times and combining the charging curve with the last time, firstly selecting a curve which has the same charging current as the charging curve of the last 10 times and has an environmental temperature difference smaller than 5 degrees from the charging curve of the last 10 times, selecting a curve which is combined with the curve of the last time into a curve containing two characteristic value position curves from the rest curves, and selecting the curve with the closest environmental temperature if a plurality of curves meet the requirement; if the ambient temperature is the same, the most recent charging profile, i.e., the profile closest in time to the last charge, is selected.
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