Method for detecting battery system health during dc charging of a complete vehicle

Abstract

The present application relates to a kind of whole vehicle direct current charging process detection battery system health degree method, comprising the following steps: obtaining the maximum charging current data of battery when SOC=0%;In the artificial preset SOC interval, according to the charging capacity, point operation is carried out, and a plurality of different fitting points are obtained;Obtain the highest battery charge and the lowest battery charge;Polarization voltage is calculated;Unpolarized voltage is calculated;Find the current battery charge in the artificial preset battery SOC-OCV curve;Find the real SOC value;Battery system health degree is calculated.The present application can have abundant data resources and can be widely used in application process, and further has good data extraction convenience;The stability of calculation formula is simple, and the health degree of the technical calculation of the present application is more accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of commercial vehicle battery application, in particular to a method for detecting battery system health degree in a whole vehicle direct current charging process. BACKGROUND

[0002] At present, the number of electric vehicles is increasing year by year, and the market occasionally has problems of batch replacement due to battery health degree not meeting the standard within the warranty period. Vehicle enterprises generally use the method of calculating discharge capacity for statistics, but due to the large difference in discharge working conditions, the results of calculation are quite different. It is urgent to use the battery charge and discharge data under the steady state working condition to analyze the battery health degree.

[0003] A typical prior art is Chinese patent with application number 200710064294.4 and name "Estimation method of state of charge of nickel-hydrogen power battery based on standard battery model"; it discloses the following technical solution:

[0004] (1) Obtain multiple external characteristic quantities of the internal resistance, capacity and discharge curve of the battery respectively, and jointly judge the current health state of the battery by fusing the above-mentioned characteristic quantities.

[0005] (2) Including the following steps: charge the lithium ion battery to the upper limit cut-off voltage and keep constant voltage charging, so that the battery reaches 100% SOC; after the battery voltage is stable, the ohmic resistance Rohm is measured by using the step method or impedance spectrum method, and the internal resistance SOHR of SOH is calculated; discharge the battery to the lower limit cut-off voltage to shorten the discharge stage in the capacity method, and after standing, the discharge curve of the battery from 100% to 0% SOC is obtained, so that the discharged capacity and the discharge curve are obtained, and the capacity SOHQ of SOH is calculated, the correlation of the two discharge curves is calculated by comparing the discharge curve with the initial or standard discharge curve, and the discharge SOHC of SOH is obtained; the ohmic resistance Rohm1 is measured by using the step method or impedance spectrum method, and the initial or standard ohmic resistance SOH of the internal resistance SOHR1 at SOC of 0% is calculated; the fusion estimation of the four characteristic quantities SOHR, SOHQ, SOHC and SOHR1 of battery SOH is realized by using the weighting method or the like.

[0006] (3) Charge 1C to the upper limit cut-off voltage, and keep constant voltage charging until the current is less than 0.02C or the time exceeds the set time, so that the battery reaches 100% SOC.

[0007] (4) After the battery voltage is stable, the ohmic resistance Rohm is measured by using the step method or impedance spectrum method, and is calculated according to the formula.

[0008] (5) Discharge the battery at 2C or more to the lower limit cut-off voltage.

[0009] (6) using step method or impedance spectrum method to measure ohmic resistance Rohm1.

[0010] (7) wherein R' ohm represents the initial or standard ohmic resistance of the type of battery when the SOC is 100%; Q' represents the initial or standard capacity of the type of battery, Q represents the capacity of the battery discharged at 2C rate to the cut-off voltage; R' ohm1 represents the initial or standard ohmic resistance of the type of battery when the SOC is 0%.

[0011] (8) using standard deviation calculation method to calculate the correlation of the discharge curve and the initial or standard discharge curve.

[0012] (9) using weighted method to calculate the battery SOH: SOH = ∑a*SOH R +b*SOH Q +c*SOH C +d*SOH R1 ; wherein a, b, c, d are weighting coefficients, and finally the battery SOH estimation value is obtained.

[0013] Summarizing the technical scheme of 200710064294.4, it can be concluded that the existing technology focuses on a whole SOH estimation scheme, which decomposes SOH into SOHQ and SOHR two categories of calculation.

[0014] 200710064294.4 considers comprehensively, but the test process is complicated and the workload is large, and a simple method for evaluating the battery health is urgently needed.

[0015] In view of the problem that the current battery life calculation method is complicated and has low accuracy, a method with simple algorithm and strong practicability is needed to enable vehicle enterprises to respond to health degradation problems in a timely manner; SOHQ is mainly obtained by small current charge and discharge test, and SOH R is often obtained by Thevenin model simulation, which requires testing a large amount of data, and the result is obtained by matlab simulation. SUMMARY

[0016] The present application provides a method for detecting the health of a battery system during the direct current charging process of a whole vehicle, aiming at the above problems, which has the advantages of rich data resources and wide application, and further has good data extraction convenience; the calculation formula is stable and simple, and the health calculated by the present application has higher accuracy; two functions can be realized for a specific battery pack: real-time measurement of the direct current resistance in the whole life cycle, and real-time calculation of the battery system health SOHR.

[0017] To solve the above problems, the technical scheme provided by the present application is:

[0018] A method for detecting battery system health degree in a whole vehicle direct current charging process, comprising the following steps:

[0019] S100. Calculating theoretical battery maximum charging current;

[0020] S200. Calculating battery system health degree; the battery system health degree is the final result of the method.

[0021] Preferably, S100 specifically comprises the following steps:

[0022] S110. Obtaining maximum charging current data of the battery at SOC=0%; the SOC is used to represent the current charge of the battery;

[0023] S120. In the artificially preset SOC interval, according to the charging capacity, a point selection operation is performed to obtain a plurality of different fitting points; each fitting point comprises a value of the charging capacity and a value of the optimal charging current corresponding to the value of the charging capacity;

[0024] S130. Formulating a step charging map.

[0025] Preferably, S110 specifically comprises the following steps:

[0026] S111. At SOC=0%, the maximum charging current data of the battery is measured by using a three-electrode charging method; the three-electrode charging method comprises three electrodes, namely a positive electrode, a negative electrode and a reference electrode; during the charging stage of the measurement process, the potential of the negative electrode is maintained at not less than 0V;

[0027] S112. After the measurement process of S111 is completed, the battery cell is disassembled; then, according to the disassembly result, the following operations are performed:

[0028] If lithium precipitation occurs on the surface of the disassembled battery cell, the test result of S111 is discarded; then, the battery used in S111 is discarded and a new battery of the same type is obtained; then, S111 is returned and executed again;

[0029] If lithium precipitation does not occur on the surface of the disassembled battery cell, the maximum charging current data of the battery measured in S111 is retained.

[0030] Preferably, S120 specifically comprises the following steps:

[0031] S121. In the SOC interval, a plurality of charging capacities are selected at uniform intervals; the SOC interval is a closed interval composed of different SOC values on a number axis;

[0032] S122. Obtain the value of the corresponding optimal charging current based on the value of each of the charging caps;

[0033] S123. Pack the value of the charging capacity with the value of the optimal charging current corresponding to the value of the charging capacity to obtain the fitting point corresponding to the value of the charging capacity.

[0034] Preferably, S130 specifically includes the following steps:

[0035] S131. In the last segment of the charging current ladder of the two SOC intervals SOC∈[0%,10%] and SOC∈[90%,100%], the SOC is maintained at 5% to 10%;

[0036] S132. In the SOC range of [10%, 90%], set 5 or 6 charging current steps, and the span of each charging current step shall not exceed 20% of SOC;

[0037] S133. Adopt a constant voltage charging strategy when approaching 100% SOC;

[0038] S134. Based on the steps completed in S131 to S134, specify a charging map diagram for the stepped charging map; then, create a SOC-I diagram based on the charging map diagram; the SOC-I diagram is a stepped curve diagram; the step transition points of the curves in the SOC-I diagram are the switching moments of the charging current.

[0039] Preferably, S200 specifically includes the following steps:

[0040] S210. Obtain the maximum battery charge and the minimum battery charge; both the maximum battery charge and the minimum battery charge are preset by the manufacturer;

[0041] S220. The polarization voltage is calculated.

[0042] S230. Calculate the unpolarized voltage based on the polarization voltage;

[0043] S240. Based on the unpolarized voltage, find the current charge of the battery corresponding to the unpolarized voltage in the artificially preset battery SOC-OCV curve;

[0044] S250. Set the current battery charge obtained in S240 to the true SOC value obtained from the battery SOC-OCV curve;

[0045] S260. The battery system health is calculated by finding the true SOC value based on the battery SOC-OCV curve obtained in S250.

[0046] Preferably, the optimal charging current is expressed as follows:

[0047] I c = I0- β * SOC

[0048] wherein: I c is the optimal charging current; β is the maximum charging current reduction coefficient; SOC is the current charge amount of the battery; I0is the initial charging current;

[0049] The maximum charging current reduction coefficient is expressed as follows:

[0050] β = α * Q

[0051] wherein: α is the charging acceptance rate; Q is the charging capacity;

[0052] The initial charging current is expressed as follows:

[0053]

[0054] wherein: I0is the initial charging current; e is the natural logarithm; t is the charging duration.

[0055] Preferably, the polarization voltage is expressed as follows:

[0056] U 极化 = I * R

[0057] wherein: U 极化 is the polarization voltage; I is the last segment charging current; R is the charging DC internal resistance;

[0058] The last segment charging current is the last segment constant current charging current of the step charging map;

[0059] The charging DC internal resistance is expressed as follows:

[0060] R = ΔU / ΔI

[0061] wherein: ΔU is the charging voltage variation, obtained by real-time acquisition of the charging voltage during charging; ΔI is the charging current variation, obtained by real-time acquisition of the charging current during charging; the charging voltage variation and the charging current variation are synchronously acquired over the charging duration, and the charging voltage variation changes with the charging current variation.

[0062] Preferably, the un-polarization voltage is expressed as follows:

[0063] U 未极化 = U 满充 - U 极化 = U 满充 - I * R

[0064] wherein: U 未极化 is the un-polarized voltage; U 满充 is the full charge voltage, obtained by measuring the battery in full charge state.

[0065] Preferably, the battery system health degree is expressed as follows:

[0066] SOH R = (SOC 真实 -SOC min ) / (SOC max -SOC min )

[0067] wherein: SOH R is the battery system health degree; SOC 真实 is the real SOC value obtained according to the battery SOC-OCV curve; SOC min is the minimum battery charge amount; SOC max is the maximum battery charge amount.

[0068] Compared with the prior art, the present application has the following advantages:

[0069] 1. Since the present application extracts charging data with fixed working conditions, the present application can have abundant data resources and can be widely used in the application process, and further has good data extraction convenience.

[0070] 2. Since the present application uses the charging process current step conversion point, the calculation formula is stable and simple, and the health degree calculated by the present application has higher accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 is a pulse test voltage-current change curve diagram of a specific embodiment of the present application;

[0072] Figure 2 is a battery charging capacity curve diagram according to the third law of mass fitting of a specific embodiment of the present application;

[0073] Figure 3 is a battery OCV curve of a specific embodiment of the present application. DETAILED DESCRIPTION

[0074] The present application will be further illustrated below in conjunction with specific embodiments, and it should be understood that these embodiments are only used to illustrate the present application and not used to limit the scope of the present application, and after reading the present application, various equivalent modifications of the present application by those skilled in the art all fall within the scope defined by the claims attached hereto.

[0075] A method for detecting battery system health during a whole vehicle direct current charging process, comprising the following steps:

[0076] S100. Calculate a theoretical maximum battery charging current.

[0077] In this embodiment, S100 specifically comprises the following steps:

[0078] S110. Obtain maximum battery charging current data at SOC=0%; SOC is used to represent the current charge of the battery.

[0079] In this embodiment, S110 specifically comprises the following steps:

[0080] S111. At SOC=0%, use a three-electrode charging method to measure and obtain the maximum battery charging current data; in the three-electrode charging method, there are three electrodes, namely the positive electrode, the negative electrode, and the reference electrode; during the charging phase of the measurement process, the negative electrode potential is maintained at no less than 0V.

[0081] S112. After the measurement process of S111 ends, disassemble the battery cell; then, according to the disassembly result, perform the following operations:

[0082] If lithium precipitation occurs on the surface of the disassembled battery cell, discard the test result of this S111; then, discard the battery used in this S111 and replace it with a new battery of the same model; then, return to and perform S111 again.

[0083] If lithium precipitation does not occur on the surface of the disassembled battery cell, retain the maximum battery charging current data measured in this S111.

[0084] It should be emphasized that during the charging phase of the measurement process, the negative electrode potential must be maintained at no less than 0V, otherwise lithium precipitation may occur; and lithium precipitation may likely lead to safety risks.

[0085] S120. Within a manually preset SOC interval, perform a point selection operation according to the charging capacity to obtain multiple different fitting points; each fitting point comprises a charging capacity value and a best charging current value corresponding to the charging capacity value.

[0086] In this embodiment, S120 specifically comprises the following steps:

[0087] S121. Within the SOC interval, select multiple charging capacity values at uniform intervals; the SOC interval is a closed interval composed of different SOC values on the number axis.

[0088] S122. Obtain the corresponding best charging current value according to each charging capacity value.

[0089] S123. Pack the value of the charging capacity with the value of the optimal charging current corresponding to the value of the charging capacity to obtain a fitting point corresponding to the value of the charging capacity.

[0090] It should be noted that the process of obtaining the fitting point by uniformly selecting points in the SOC interval preset by the artificial according to Q is consistent with the measurement method and matters needing attention of the maximum charging current data of the battery in S110 at SOC=0%, using three-electrode charging method, and it is again emphasized to prevent the generation of lithium precipitation phenomenon.

[0091] In the embodiment, the fitting point is expressed in the form of (Q, I c ).

[0092] In the embodiment, the optimal charging current is expressed by formula (1):

[0093] I c =I0-β*SOC (1)

[0094] Wherein: I c is the optimal charging current; β is the maximum charging current reduction coefficient; SOC is the current charge of the battery; I0 is the initial charging current.

[0095] The maximum charging current reduction coefficient is expressed by formula (2):

[0096] β=α*Q (2)

[0097] Wherein: α is the charging acceptance rate; Q is the charging capacity.

[0098] The initial charging current is expressed by formula (3) as follows:

[0099]

[0100] Wherein: I0 is the initial charging current; e is the natural logarithm; t is the charging duration.

[0101] In the embodiment, the charging duration is not less than 1 min.

[0102] It should be noted that first, the relationship between the initial charging current and the optimal charging current is determined, that is, expressed by the first part in formula (3) to obtain formula (4):

[0103] I c =I0*e -αt (4)

[0104] Then integrate the second part in formula (3) to obtain formula (5):

[0105] e αt =1-αt / I0 (5)

[0106] By combining the above formula (4) and formula (5), a fitting expression, i.e. formula (1), can be obtained.

[0107] It should be further explained that the physical basis of the derivation process in S120 is that the maximum charging current of the battery at different SOC must comply with the third law of mass, thereby obtaining

[0108] As shown in FIG. 1, it is a schematic diagram of fitting the charging capacity curve of the battery cell according to the third law of mass. Figure 2

[0109] S130. Formulate a step charging map based on the relationship between the maximum charging current and the SOC.

[0110] In the embodiment, S130 specifically comprises the following steps:

[0111] S131. In the last segment of the charging current step in the SOC interval of SOC∈[0%, 10%] and SOC∈[90%, 100%], the SOC is continuously 5% to 10%.

[0112] It should be noted that the theoretical basis of S131 is that the internal resistance changes greatly at both ends of the entire SOC, and therefore the above numerical range is the preferred numerical range for achieving the technical purpose of the present application through the long-term experimental verification of the applicant. The embodiment is implemented according to the above numerical range, thereby ensuring the accuracy of the calculation.

[0113] S132. In the SOC interval of SOC∈[10%, 90%], 5 or 6 charging current steps are set, and the span of each charging current step does not exceed 20% SOC.

[0114] It should be noted that the purpose of setting the number and span of the charging current steps in S133 is to make the charging rate change frequently.

[0115] S133. A constant voltage charging strategy is adopted when approaching 100% SOC.

[0116] S134. On the basis of the completion of S131-S134, a charging map graph about the step charging map is specified; then an SOC-I graph is made according to the charging map graph; the SOC-I graph is a step curve graph; the step conversion of the curve in the SOC-I graph is the switching time of the charging current; the change of the charging current corresponds to the change of the voltage as shown in FIG. 2. Figure 1

[0117] S200. Calculate the health degree of the battery system; the health degree of the battery system is the final result of the method.

[0118] ​​In the embodiment, S200 specifically comprises the following steps:

[0119] S210. Obtain the maximum battery charge amount and the minimum battery charge amount; both of which are pre-set by the manufacturer.

[0120] It should be noted that the vehicle manufacturer will limit the SOC usage range when the battery is actually used. In order to facilitate subsequent understanding, in the embodiment, the SOC min represents the minimum battery charge amount, and the SOC max represents the maximum battery charge amount. Therefore, the battery SOC usage range is the interval [SOC min , SOC max ].

[0121] S220. Calculate the polarization voltage.

[0122] In the embodiment, the polarization voltage is expressed by formula (6):

[0123] U 极化 = I * R (6)

[0124] Where: U 极化 is the polarization voltage; I is the last charging current; and R is the charging DC internal resistance.

[0125] The last charging current is the last constant current charging current of the step charging map.

[0126] It should be noted that in the technical field, the charging internal resistance is approximately considered to be consistent with the charging internal resistance. Therefore, the way in which the high SOC internal resistance affects the health degree is mainly reflected in the last constant current charging current. Therefore, the last charging current in the step charging map is I, and the polarization voltage is U 极化 = I * R.

[0127] The charging DC internal resistance is expressed by formula (7):

[0128] R = ΔU / ΔI (7)

[0129] Where: ΔU is the charging voltage change amount, which is obtained by real-time acquisition of the charging voltage during charging; and ΔI is the charging current change amount, which is obtained by real-time acquisition of the charging current during charging. The charging voltage change amount and the charging current change amount are synchronously collected in the charging duration, and the charging voltage change amount changes with the charging current change amount.

[0130] S230. Calculate the unpolarized voltage according to the polarization voltage.

[0131] In the embodiment, the unpolarized voltage is expressed by formula (8):

[0132] U未极化 = U 满充 - U 极化 = U 满充 - I * R (8)

[0133] wherein: U 未极化 is the un-polarized voltage; U 满充 is the full charge voltage, which is obtained by measuring the battery in full charge state.

[0134] It is to be noted that when the full charge voltage has been measured, the battery at this time does not consider the polarization voltage; thus, formula (8) is obtained.

[0135] S240. According to the un-polarized voltage, the current charge amount of the battery corresponding to the un-polarized voltage is obtained in the artificially preset battery SOC-OCV curve.

[0136] S250. The current charge amount of the battery obtained in S240 is set as the real SOC value obtained according to the battery SOC-OCV curve.

[0137] S260. According to the real SOC value obtained according to the battery SOC-OCV curve in S250, the battery system health degree is calculated.

[0138] In the embodiment, the battery system health degree is expressed by formula (9):

[0139] SOH R = (SOC 真实 - SOC min ) / (SOC max - SOC min ) (9)

[0140] wherein: SOH R is the battery system health degree; SOC 真实 is the real SOC value obtained according to the battery SOC-OCV curve; SOC min is the lowest battery charge amount; and SOC max is the highest battery charge amount.

[0141] In order to further demonstrate the technical effect of the present application, the embodiment herein gives an experimental process containing specific numerical values, and the same numerical values are brought into the prior art to make a simulation, so as to compare and show the significant progress of the present application relative to the prior art.

[0142] As Figure 1The pulse current test data of the battery SOC in this experiment is shown, wherein the U1-U5 stage is the pulse discharge test data, and the U5-U9 stage is the pulse charge test data; during the end of charging, the battery voltage reaches the charging cutoff voltage due to the ohmic internal resistance polarization effect under a certain current, and the charging is stopped, and the corresponding process is U5-U6.

[0143] First, as shown in Figure 3 , the battery SOC-OCV curve is artificially preset, and is a known condition.

[0144] Secondly, the initial parameters of this experiment are as follows:

[0145] The nominal capacity of the battery is 20 Ah, and the measured charging capacity is Q = 20.3 Ah.

[0146] The minimum battery charge is SOC min = 3%.

[0147] The maximum battery charge is SOC max = 98%.

[0148] Therefore, in this embodiment, the use range of the battery is [3%, 98%].

[0149] Therefore, in this embodiment, the voltage at SOC = 98% is taken as the full charge voltage U 满充 ; it is measured that the full charge voltage corresponding to SOC = 98% is U 满充 = 4.16 V.

[0150] Then, it is measured that the initial charging current is I0 = 50 A.

[0151] Then, in the use range of the battery as the SOC interval [3%, 98%], the corresponding maximum charging current is tested every 10% SOC.

[0152] Then, the relationship between SOC and the corresponding maximum charging current is shown in Table 1:

[0153] Table 1. Relationship table between SOC and the corresponding maximum charging current

[0154] SOC (%) 0 10 20 30 40 50 60 70 80 90 100 I (A) 50 43.9 38.1 33 27.9 23 18.6 14 8.2 3.4 0

[0155] On the basis of Table 1 and the above initial parameters, the fitting points in Table 1 are fitted according to formula (1), and the last charging current is obtained as follows:

[0156] I = 48.42-0.49*SOC

[0157] Therefore, in the embodiment, two stages are defined according to the fitted battery charging and discharging capacity curve: the charging current is 8 A when SOC is in [80%, 90%], and the charging current is 3 A when SOC is in [90%, 98%].

[0158] Charging at 90% SOC is equivalent to HPPC test on the battery, and the result is Figure 1 U1-U3 data; wherein:

[0159] U1=4.15 V, U2=3.95 V, so the charging DC internal resistance is

[0160] R=(U1-U2) / ΔI=0.2 V / 5 A=40 mΩ

[0161] Next, when charging at the end, the charging current is 3 A; therefore, the corresponding polarization voltage is:

[0162] U 极化 =I*R=3 A*40 mΩ=0.12 V

[0163] Then, the un-polarized voltage is calculated according to the polarization voltage as:

[0164] U 未极化 =U 满充 -U 极化 =U 满充 -I*R=4.16 V-0.12 V=4.04 V

[0165] Then, the real SOC value obtained according to the battery SOC-OCV curve is SOC 真实1 =96%.

[0166] Finally, the above data is substituted into formula (9) to obtain:

[0167] SOH R =(SOC 真实1 -SOC min ) / (SOC max -SOC min )=(96%-3%) / (98%-3%)=97.9%

[0168] The above is the calculation, and next, in order to verify the technical effect of the application, the battery is actually charged at 0.1C to obtain the charging capacity:

[0169] SOH 真实2 =charging capacity / initial charging capacity=95%

[0170] Therefore, the real SOC value measured and the real SOC value calculated can be compared to obtain a deviation value:

[0171] Bias = |SOH 真实1 -SOH 计算2 | / SOH 真实2 = 1.3%

[0172] Correspondingly, the prior art technical solutions are Chinese patents with application number 200710064294.4 and name "Nickel-hydrogen power battery state of charge estimation method based on standard battery model", and 201680030378.3 and name "Method and device for determining health and state of charge of lithium-sulfur battery pack", which also disclose the calculation method of SOH; in order to show the significant technical progress of the present application relative to the prior art, the same battery and parameters are also experimented according to the above two prior arts respectively in this embodiment, and the comparison of the results obtained by the present application is shown in Table 2:

[0173] Table 2. Comparison table of technical effects

[0174] Technical Solution CN201680030378.3 CN200710064294.4 The Invention SOH 90.8％ 92％ 93.8％ Calculation Deviation % 4.4％ 3.1％ 1.3％

[0175] It is obvious that the bias of the present application relative to 201680030378.3 is reduced by 4.4%-1.3%=3.1%, that is, the accuracy is improved by 3.1% / 4.4%=70.4%, and the effect is very obvious.

[0176] The bias of the present application relative to 200710064294.4 is reduced by 3.1%-1.3%=1.8%, that is, the accuracy is improved by 1.8% / 3.1%=58.1%, and the effect is also very obvious.

[0177] It can be seen that the accuracy of the present application is improved by at least nearly 60% compared with the prior art, and more than 70%, which is a significant technical progress.

[0178] In the above detailed description, various features are combined together in a single embodiment to simplify the disclosure. This disclosure method should not be interpreted as reflecting the intention that the embodiments of the claimed subject matter require more features than those clearly stated in each claim. On the contrary, as reflected in the appended claims, the present application is in a state of less than all the features of the disclosed single embodiment. Therefore, the appended claims are hereby incorporated into the detailed description, where each claim is separately as a separate preferred embodiment of the present application.

[0179] The foregoing description of the exemplary embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

[0180] The above description includes one or more examples of the embodiments. Of course, not all possible combinations of components or methods described above will be described, but one of ordinary skill in the art will recognize that further combinations and permutations of the embodiments described herein are possible. Accordingly, the disclosure is intended to embrace all such alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be interpreted as "including but not limited to" rather than "consisting only of." Also, where the term "or" is used in either the detailed description or the claims, such term is intended to be interpreted as "exclusive or" rather than "inclusive or." That is, "A employs B or C" means "A employs B; or A employs C."

[0181] The above detailed description has shown, described, and pointed out the aspects of the application in connection with the illustrative embodiments. However, it will be understood that various modifications and variations can be made to the disclosed embodiments without departing from the spirit or scope of the application. Accordingly, the application is intended to embrace all such alterations, modifications, and variations as fall within the scope of the appended claims.

Claims

1. A method for detecting the health of a battery system during DC charging of a vehicle, characterized in that: Includes the following steps: S100. Calculate the theoretical maximum charging current of the battery; S200. Calculate the battery system health status; the battery system health status is the final result of this method; S100 specifically includes the following steps: S110. Obtain the maximum charging current data of the battery when SOC=0%; the SOC is used to characterize the current charge of the battery; S120. Within a pre-defined SOC range, a point-taking operation is performed based on the charging capacity to obtain multiple different fitting points; each fitting point contains a value of the charging capacity and the value of the optimal charging current corresponding to the value of the charging capacity; S130. Develop a tiered charging map; S200 specifically includes the following steps: S210. Obtain the maximum battery charge and the minimum battery charge; both the maximum battery charge and the minimum battery charge are preset by the manufacturer; S220. The polarization voltage is calculated; S230. Calculate the unpolarized voltage based on the polarization voltage; S240. Based on the unpolarized voltage, find the current charge of the battery corresponding to the unpolarized voltage in the artificially preset battery SOC-OCV curve; S250. Set the current charge of the battery obtained in S240 to the true SOC value obtained from the battery SOC-OCV curve; S260. Calculate the health of the battery system by finding the true SOC value based on the battery SOC-OCV curve obtained in S250. The polarization voltage is expressed by the following formula: in: The polarization voltage; This is the final charging current. The DC internal resistance during charging; The last segment of charging current is the last segment of constant current charging current in the stepped charging map. The charging DC internal resistance is expressed by the following formula: in: The change in charging voltage is obtained by real-time acquisition of the charging voltage during charging. The charging current change is obtained by real-time acquisition of the charging current during charging; the charging voltage change is acquired synchronously with the charging current change over the charging duration, and the charging voltage change changes with the charging current change.

2. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 1, characterized in that: S110 specifically includes the following steps: S111. When SOC=0%, the maximum charging current data of the battery is measured using a three-electrode charging method; the three-electrode charging method includes three electrodes, namely a positive electrode, a negative electrode, and a reference electrode; during the charging phase of the measurement process, the potential of the negative electrode is maintained at no less than 0V; S112. After the measurement process in S111 is completed, disassemble the battery cell; then, based on the disassembly results, perform the following operations: If lithium plating appears on the surface of the disassembled battery cell, the test results of this S111 are discarded; then the battery used in this S111 is discarded and replaced with a new battery of the same model. Then return to and execute S111 again; If no lithium plating appears on the surface of the disassembled battery cell, the maximum charging current data of the battery obtained by S111 is retained.

3. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 2, characterized in that: S120 specifically includes the following steps: S121. Within the SOC range, select multiple charging capacities at uniform intervals; the SOC range is a closed interval formed by different SOC values ​​on a number axis; S122. Obtain the corresponding value of the optimal charging current based on the value of each of the charging caps; S123. Pack the value of the charging capacity with the value of the optimal charging current corresponding to the value of the charging capacity to obtain the fitting point corresponding to the value of the charging capacity.

4. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 3, characterized in that: S130 specifically includes the following steps: S131. In and In the last segment of the charging current ladder of these two SOC intervals, the SOC remains between 5% and 10%. S132. In Within this SOC range, five or six charging current steps are set, and the span of each charging current step does not exceed 20% of SOC. S133. Adopt a constant voltage charging strategy when approaching 100% SOC; S134. Based on the steps completed in S131 to S133, specify a charging map diagram for the stepped charging map; then, create a SOC-I diagram based on the charging map diagram; the SOC-I diagram is a stepped curve diagram; the step transition points of the curves in the SOC-I diagram are the switching moments of the charging current.

5. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 4, characterized in that: The optimal charging current is expressed by the following formula: in: The optimal charging current is specified. This is the reduction factor for the maximum charging current; The current charge of the battery; This is the initial charging current; The maximum charging current reduction factor is expressed by the following formula: in: For charging acceptance rate; The charging capacity; The initial charging current is expressed by the following formula: in: The initial charging current; It is the natural logarithm; The charging duration.

6. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 5, characterized in that: The unpolarized voltage is expressed by the following formula: in: The unpolarized voltage; The full charge voltage is obtained by measuring a fully charged battery.

7. The method for detecting the health of a battery system during DC charging of a vehicle according to claim 6, characterized in that: The health status of the battery system is expressed by the following formula: in: The health status of the battery system; The value referred to here is the actual SOC value obtained by searching based on the battery SOC-OCV curve. This refers to the minimum battery charge. This represents the highest battery charge.

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