A method for estimating the state of health of a power battery

Abstract

The application discloses a SOH estimation method of a power battery, which is applied to each battery in a battery system and comprises the following steps: step S1, obtaining a charging OCV table; step S2, obtaining a discharging OCV table; step S3, obtaining a charging SOH of the battery; step S4, obtaining a discharging SOH of the battery; and step S5, obtaining a final SOH of the battery according to the charging SOH of the battery obtained in step S3, the discharging SOH of the battery obtained in step S4 and a preset calculation formula. The SOH estimation method of the power battery is scientific in design, can reliably estimate and obtain the SOH of the battery system according to the change relation between the electric quantity and the SOC in the charging and discharging processes, is small in calculation amount, fast and efficient, can save a large amount of time and has great practical significance.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management, and in particular to a method for estimating the SOH of a power battery. Background Art

[0002] Power batteries are important components of new energy vehicles. During the use of power batteries, the battery management system can ensure the safety of power batteries and provide useful battery-related information to the entire vehicle. Among them, the battery's SOC (state of charge, also called remaining power) and SOH (battery capacity, health, and performance status, which is the ratio of performance parameters to nominal parameters after a period of battery use) are important information that directly affects the driving experience of new energy vehicles.

[0003] Therefore, whether the two battery parameters, SOC and SOH, can be accurately estimated has become an important criterion for measuring whether a battery management system is qualified.

[0004] SOC estimation can guarantee a certain degree of accuracy in new battery systems. However, when the battery system has been used for a period of time and has decayed, the accuracy of battery SOC estimation will be greatly reduced.

[0005] To ensure accurate SOC estimation throughout the lifecycle of a power battery, it's necessary to factor in the SOC estimation process. However, existing SOH estimation techniques typically rely on building models based on extensive calendar life test data. This is not only costly, but also computationally intensive and time-consuming. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for estimating the SOH of a power battery in view of the technical defects in the prior art.

[0007] To this end, the present invention provides a method for estimating the SOH of a power battery, which is applied to each battery in a battery system, comprising the following steps:

[0008] Step S1, obtaining a charging OCV table;

[0009] Step S2, obtaining a discharge OCV table;

[0010] Step S3, obtaining the battery charging SOH:

[0011] Step S4, obtaining the battery discharge SOH:

[0012] Step S5: Obtain the final SOH of the battery according to the charging SOH of the battery obtained in step S3 and the discharging SOH of the battery obtained in step S4, as well as a preset calculation formula.

[0013] Preferably, the step S1 specifically comprises the following steps:

[0014] In a plurality of preset constant-temperature environments with different charging temperatures, the battery is subjected to a plurality of preset constant-current charging operations, and the voltage value and the SOC value of the battery in the charging process are collected in real time to obtain a set of charging dynamic OCV tables under different charging temperatures and different charging rates;

[0015] The charging dynamic OCV table records the correspondence between the charging temperature, the charging rate, the charging duration, the voltage value in the charging process and the SOC in the charging process of the battery;

[0016] The preset constant-current charging operation specifically includes the following steps: first, emptying the battery, then charging the battery at a preset first charging rate to a preset charging voltage threshold, and then charging the battery at a preset second charging rate to the self-charging cutoff voltage of the battery, i.e., full charge;

[0017] The preset first charging rate is greater than the preset second charging rate.

[0018] Preferably, in the step S1, the battery is emptied, specifically, the voltage of the battery is discharged to the discharge cutoff voltage of the battery.

[0019] In the step S1, the preset constant-current charging operation specifically includes the following steps: first, emptying the battery, then charging the battery at a 1C charging rate to a preset discharge voltage threshold, and then charging the battery at a 0.1C, 0.2, 0.3 or 0.5C charging rate to the self-charging cutoff voltage of the battery, i.e., full charge.

[0020] In the step S1, the plurality of preset constant-temperature environments with different charging temperatures specifically includes a plurality of preset constant-temperature environments with different charging temperatures, the temperature values of which gradually increase.

[0021] Preferably, the step S2 comprises the following steps:

[0022] In a plurality of preset constant-temperature environments with different discharging temperatures, the battery is subjected to a plurality of preset constant-current discharging operations, and the voltage value and the SOC value of the battery in the discharging process are collected in real time to obtain a set of discharging dynamic OCV tables under different discharging temperatures and different discharging rates;

[0023] The discharging dynamic OCV table records the correspondence between the discharging temperature, the discharging rate, the discharging duration, the voltage value in the discharging process and the SOC in the discharging process of the battery;

[0024] The preset constant-current discharge operation specifically includes: first, performing a constant-current discharge operation on the battery at a preset first discharge rate to discharge the battery to a preset discharge voltage threshold; and then, performing a constant-current discharge operation on the battery at a preset second discharge rate to discharge the battery to a discharge cut-off voltage of the battery itself, i.e., to empty.

[0025] The preset first discharge rate is greater than the preset second discharge rate.

[0026] Preferably, in step S2, the preset constant-current discharge operation specifically includes: first, performing a constant-current discharge operation on the battery at a 1C charging rate to discharge the battery to a preset discharge voltage threshold; and then, performing a constant-current discharge operation on the battery at a 0.3C, 0.5C or 0.8C discharge rate to discharge the battery to a discharge cut-off voltage of the battery itself, i.e., to empty.

[0027] In step S2, the plurality of preset constant-temperature environments of different discharge temperatures specifically include a plurality of preset constant-temperature environments of different discharge temperatures with gradually increasing temperature values.

[0028] Preferably, the step S3 includes the following steps:

[0029] Step S31, during the direct-current charging of the battery system, for any one battery in the battery system, whenever the battery management system BMS detects that the battery satisfies a preset charging condition, a preset battery charging capacity acquisition operation is performed once to obtain a charging capacity C 充电 of the battery.

[0030] The preset charging condition specifically includes that a real-time charging voltage of the battery is greater than or equal to a preset charging voltage threshold recorded in a charging dynamic OCV table, and a real-time charging current is less than a preset charging current threshold recorded in the charging dynamic OCV table, and a battery temperature is within a preset charging temperature value range.

[0031] The preset charging current threshold recorded in the charging dynamic OCV table is a preset first discharge rate.

[0032] A maximum value of the preset charging temperature value range is a maximum value of the plurality of charging temperatures in step S1, and a minimum value of the preset charging temperature value range is a minimum value of the plurality of charging temperatures in step S1.

[0033] Step S32, when the charging capacities C 充电 of the plurality of batteries are collected, the charging capacities C 充电 of the plurality of batteries are averaged to obtain C 充电平均 .

[0034] Step S33, the charging SOH of the battery is calculated according to a preset charging SOH calculation formula.

[0035] Preferably, in step S31, the operation of obtaining the battery charging capacity is preset, specifically including the following steps:

[0036] Step S311: Record the real-time charging voltage of the battery as the battery starting point voltage V1 充电 , and calculate the amount of electricity charged into the battery at this time, and record it as the battery starting point electricity Q1 充电 ;

[0037] Step S312: As the DC charging process continues, when the battery no longer meets the preset charging conditions, the real-time charging voltage of the battery is recorded as the battery end point voltage V2. 充电 , and calculate the amount of electricity charged into the battery at this time, and record it as the battery end point electricity Q2 充电 ;

[0038] Step S313: The battery starting point power Q1 充电 And the battery end point charge Q2 充电 Calculate the difference to obtain the amount of charge ΔQ between the starting point and the end point 充电 , and according to the battery starting point voltage V1 充电 and battery end point voltage V2 充电 , query the charging dynamic OCV table obtained in step S1 to obtain the battery starting point voltage V1 充电 Corresponding battery starting point SOC 充电 And the battery end point voltage V2 充电 Corresponding battery end point SOC 充电 , calculate the battery starting point SOC of the battery during the charging process 充电 and battery end point SOC 充电 The difference ΔSOC 充电 ;

[0039] Step S314: Obtain the battery charging capacity C according to the preset first calculation formula. 充电 ;

[0040] The preset first calculation formula is as follows:

[0041]

[0042] In step S33, the preset charging SOH calculation formula is as follows:

[0043] Battery charge SOH = C 充电平均 / C 标称 *100%;

[0044] Among them, C 标称 is the nominal capacity of the battery.

[0045] Preferably, the step S4 specifically includes the following steps:

[0046] Step S41: During the DC discharge process of the battery system, for any battery in the battery system, whenever the battery management system BMS detects that the battery meets the preset discharge condition, it executes a preset battery discharge capacity acquisition operation to obtain a discharge capacity C of the battery. 放电 ;

[0047] The preset discharge conditions are: the real-time SOC of the battery is less than the preset SOC threshold, the real-time discharge voltage is less than the preset discharge voltage threshold recorded in the discharge dynamic OCV table, the real-time charging current is less than the preset current discharge threshold recorded in the discharge dynamic OCV table, and the battery temperature is within the preset discharge temperature value range;

[0048] In step S41, the preset current discharge threshold recorded in the discharge dynamic OCV table is the preset first discharge rate;

[0049] In step S41, the maximum value of the preset discharge temperature value range is the maximum value of the multiple charging temperatures in step S2, and the minimum value of the preset discharge temperature value range is the minimum value of the multiple charging temperatures in step S2;

[0050] Step S42: When the discharge capacity C of multiple batteries is collected 放电 When the discharge capacity of multiple batteries C 放电 Find the average value and get C 放电平均 ;

[0051] Step S43 , calculating the discharge SOH of the battery according to a preset discharge SOH calculation formula.

[0052] Preferably, in step S41, the operation of obtaining the discharge capacity of the preset battery specifically includes the following steps:

[0053] Step S411: Record the real-time discharge voltage of the battery as the battery starting point voltage V1 放电 , and calculate the amount of electricity released by the battery at this time, and record it as the battery starting point electricity Q1 放电 ;

[0054] Step S412: As the DC discharge process continues, when the battery no longer meets the preset discharge conditions, the real-time discharge voltage of the battery is recorded as the battery end point voltage V2. 放电 , and calculate the amount of electricity released by the battery at this time, and record it as the battery end point electricity Q2 放电 ;

[0055] Step S413: The battery starting point power Q1 放电And the battery end point charge Q2 放电 Calculate the difference to obtain the amount of electricity released between the starting point and the end point ΔQ 放电 , and according to the battery starting point voltage V1 放电 and battery end point voltage V2 放电 , query the discharge dynamic OCV table obtained in step S2 to obtain the battery starting point voltage V1 放电 Corresponding battery starting point SOC 放电 And the battery end point voltage V2 放电 Corresponding battery end point SOC 放电 , calculate the battery's starting point SOC during discharge 放电 and battery end point SOC 放电 The difference ΔSOC 放电 ;

[0056] Step S414: Obtain the discharge capacity C of the battery according to the preset second calculation formula. 放电 ;

[0057] The preset second calculation formula is as follows:

[0058]

[0059] In step S43, the preset discharge SOH calculation formula is as follows:

[0060] Battery discharge SOH = C 放电平均 / C 标称 *100%;

[0061] Among them, C 标称 is the nominal capacity of the battery.

[0062] Preferably, in step S5, the preset calculation formula is as follows:

[0063] The final SOH of the battery = charging SOH*x + discharging SOH*(1-x), formula (7);

[0064] In formula (7), x represents the weight factor, and the value range of x is 0 to 1.

[0065] It can be seen from the technical solution provided by the present invention above that, compared with the prior art, the present invention provides a method for estimating the SOH of a power battery. The method is scientifically designed and can reliably estimate the SOH of the battery system through the relationship between the change in charge and the change in SOC during charging and discharging. The method has not only a small amount of calculation but also is fast and efficient, which can save a lot of time and has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1A basic flow chart of a method for estimating the SOH of a power battery provided by the present invention;

[0067] Figure 2 A method for estimating the SOH of a power battery provided by the present invention, and a flow chart for estimating the charging SOH;

[0068] Figure 3 The present invention provides a method for estimating the SOH of a power battery, and a flow chart for performing discharge SOH estimation. DETAILED DESCRIPTION

[0069] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and implementation methods.

[0070] See also Figures 1 to 3 The present invention provides a method for estimating the SOH of a power battery, which is applied to each battery in a battery system and specifically includes the following steps:

[0071] Step S1, obtaining a charging OCV (open circuit voltage) table: performing multiple preset constant current charging operations on the battery in multiple constant temperature environments with different preset charging temperatures (i.e., performing multiple preset constant current charging operations in each constant temperature environment), and collecting the battery voltage and SOC value in real time during the charging process to obtain a set of charging dynamic OCV tables at different charging temperatures and different charging rates;

[0072] The charging dynamic OCV table records the corresponding relationship between the battery's charging temperature, charging rate, charging time, voltage value during the charging process, and SOC during the charging process;

[0073] The preset constant current charging operation is as follows: first, the battery is discharged, then the battery is charged with a constant current at a preset first charging rate until the battery reaches a preset charging voltage threshold, and then the battery is charged with a constant current at a preset second charging rate until the battery reaches its own charging cut-off voltage, i.e., fully charged.

[0074] The preset first charging rate is greater than the preset second charging rate.

[0075] It should be noted that the preset charging voltage threshold is lower than the charging cut-off voltage of the battery itself.

[0076] In the present invention, in step S1, the preset charging voltage threshold is a voltage value close to full charge. For iron-lithium batteries, it is necessary to select a point outside the voltage plateau and at which the current has begun to decrease based on the battery's charging power map. For ternary batteries, the voltage turning point when the charging current changes from 1C to a smaller rate is selected based on the battery's charging power map. In the present invention, in step S1, the preset charging voltage threshold is less than the battery's own charging cut-off voltage. The preset charging voltage threshold is the voltage value at which the battery is about to be fully charged. Near this voltage value, the charging current in the power battery's charging power map will significantly decrease (for example, the current drop per second reaches a preset value).

[0077] In the present invention, in step S1, a first charging rate is preset, preferably 1C.

[0078] In the present invention, in step S1, the preset second charging rate is set according to the charging power map of the power battery, which is generally less than 1C, that is, the current at which the battery is almost fully charged and enters the current reduction stage.

[0079] In step S1, in a specific implementation, the battery is discharged, specifically: the battery voltage is discharged to the battery discharge cut-off voltage.

[0080] In step S1, in a specific implementation, the preset constant current charging operation is preferably: first, the battery is discharged, and then the battery is constant-current charged to a preset discharge voltage threshold at a 1C charging rate (i.e., as a preset first charging rate), and then, the battery is constant-current charged to the battery's own charging cut-off voltage, i.e., fully charged, at a 0.1C, 0.2, 0.3 or 0.5C charging rate (i.e., as a preset second charging rate).

[0081] In step S1, the multiple constant temperature environments with different preset charging temperatures are specifically: multiple constant temperature environments with different preset charging temperatures with gradually increasing temperature values. For example, the multiple constant temperature environments with different preset charging temperatures include four constant temperature environments with different charging temperatures: 25°C, 30°C, 35°C, and 40°C.

[0082] Step S2, obtaining a discharge OCV (open circuit voltage) table: performing multiple preset constant current discharge operations on the battery in multiple constant temperature environments with different preset discharge temperatures (i.e., performing multiple preset constant current discharge operations in each constant temperature environment), and collecting the battery voltage and SOC value in real time during the discharge process to obtain a set of discharge dynamic OCV tables at different discharge temperatures and different discharge rates;

[0083] The discharge dynamic OCV table records the corresponding relationship between the battery's discharge temperature, discharge rate, discharge time, voltage value during the discharge process, and SOC during the discharge process;

[0084] The preset constant current discharge operation is specifically as follows: first, the battery is subjected to a constant current discharge operation at a preset first discharge rate to discharge the battery to a preset discharge voltage threshold; then, the battery is subjected to a constant current discharge operation at a preset second discharge rate to discharge the battery to its own discharge cut-off voltage, i.e., emptying the battery;

[0085] The preset first discharge rate is greater than the preset second discharge rate.

[0086] In step S2, regarding the preset discharge voltage threshold, for the iron-lithium battery, the point of leaving the voltage plateau period is selected, and for the ternary battery, the voltage of the turning point before the battery is about to be discharged and the discharge current is reduced is selected according to the discharge power map.

[0087] In step S2, the preset discharge voltage threshold is greater than the discharge cut-off voltage of the battery itself. The preset discharge voltage threshold is the voltage at which the battery starts to reduce current before being discharged.

[0088] In step S2, the first discharge rate is generally preset to 1C.

[0089] In the present invention, in step S2, the preset second discharge rate is set according to the discharge power map of the power battery, wherein the iron-lithium battery generally selects the current value corresponding to the SOC leaving the voltage plateau period according to the discharge power map, and the ternary battery generally selects the current value for discharging to the low SOC range and starting to reduce the current according to the discharge power map.

[0090] In step S2, the preset constant current discharge operation is specifically implemented as follows: first, a constant current discharge operation is performed on the battery at a 1C charge rate (i.e., as a preset first discharge rate) to discharge the battery to a preset discharge voltage threshold; then, a constant current discharge operation is performed on the battery at a 0.3C, 0.5C, or 0.8C discharge rate (i.e., a preset second discharge rate) to charge the battery to its own discharge cut-off voltage, i.e., to discharge the battery;

[0091] In step S2, the multiple constant temperature environments with different discharge temperatures are specifically preset, and specifically, multiple constant temperature environments with different discharge temperatures with gradually increasing temperature values. For example, the multiple constant temperature environments with different discharge temperatures include four constant temperature environments with different discharge temperatures: 25°C, 30°C, 35°C, and 40°C.

[0092] Step S3, obtaining the battery charging SOH, specifically includes the following steps:

[0093] Step S31: During the DC charging process of the battery system, for any battery in the battery system, whenever the battery management system BMS detects that the battery meets the preset charging conditions, it executes a preset battery charging capacity acquisition operation to obtain a charging capacity C of the battery.充电 (i.e. the capacity charging result of the battery);

[0094] The preset charging conditions are specifically: the real-time charging voltage of the battery is greater than or equal to the preset charging voltage threshold recorded in the charging dynamic OCV table, the real-time charging current is less than the preset charging current threshold recorded in the charging dynamic OCV table (the preset charging current threshold corresponding to the preset charging voltage threshold, that is, the preset first discharge rate), and the battery temperature is within the preset charging temperature value range;

[0095] It should be noted that in step S31 , the preset charging voltage threshold here is consistent with the preset charging voltage threshold in the process of preparing the charging dynamic OCV table, that is, the preset charging voltage threshold recorded in the charging dynamic OCV table.

[0096] In step S31, the preset charging current threshold here is consistent with the preset charging current threshold in the process of making the charging dynamic OCV table, that is, the preset charging current threshold recorded in the charging dynamic OCV table, which is the preset charging current threshold corresponding to the preset charging voltage threshold, that is, the preset first charging rate.

[0097] In step S31, the preset charging temperature value range is the temperature range distributed in the process of making the charging dynamic OCV table, that is, the maximum value of the preset charging temperature value range is the maximum value of the multiple charging temperatures in step S1, and the minimum value of the preset charging temperature value range is the minimum value of the multiple charging temperatures in step S1.

[0098] In step S31 , the temperature of the battery can be obtained through a temperature sensor installed on the surface of the battery.

[0099] Step S32: When the charge capacity C of multiple (for example, three) batteries is collected, 充电 When the charging capacity of multiple batteries is C 充电 Find the average value and get C 充电平均 ;

[0100] Step S33: Calculate the charging SOH of the battery according to a preset charging SOH calculation formula.

[0101] In the present invention, in a specific implementation, in step S31, the operation of obtaining the battery charging capacity is preset, and specifically includes the following steps:

[0102] Step S311: Record the real-time charging voltage of the battery as the battery starting point voltage V1 充电 , and calculate the amount of electricity charged into the battery at this time (specifically equal to the product of charging time and charging current), and record it as the battery starting point electricity Q1 充电 ;

[0103] Step S312: As the DC charging process continues, when the battery no longer meets the preset charging conditions, the real-time charging voltage of the battery is recorded as the battery end point voltage V2. 充电 , and calculate the amount of electricity charged into the battery at this time (specifically equal to the product of charging time and charging current), and record it as the battery end point electricity Q2 充电 ;

[0104] Step S313: The battery starting point power Q1 充电 And the battery end point charge Q2 充电 Calculate the difference to obtain the amount of charge ΔQ between the starting point and the end point 充电 , and according to the battery starting point voltage V1 充电 and battery end point voltage V2 充电 , query the charging dynamic OCV table obtained in step S1 to obtain the battery starting point voltage V1 充电 Corresponding battery starting point SOC 充电 And the battery end point voltage V2 充电 Corresponding battery end point SOC 充电 , calculate the battery starting point SOC of the battery during the charging process 充电 and battery end point SOC 充电 The difference ΔSOC 充电 ;

[0105] Step S314: Obtain the battery charging capacity C according to the preset first calculation formula. 充电 .

[0106] In the present invention, it should be noted that according to the existing SOC calculation formula, that is, the following formula (1)

[0107]

[0108] In formula (1), Cα,β is the battery capacity calculated for this charge or discharge, Icell is the battery charge or discharge current, SOC(OCV(tα)) is the SOC value obtained by looking up the battery voltage at point tα using an OCV table, and SOC(OCV(tβ)) is the SOC value obtained by looking up the battery voltage at point tβ using an OCV table. tα and tβ are two time points during charge or discharge.

[0109] According to formula (1), the following formula (2) can be derived:

[0110]

[0111] Therefore, for the battery charging process, the following formula (3) can be obtained:

[0112]

[0113] Further, the following formula (4), i.e., the preset first calculation formula, can be obtained:

[0114]

[0115] According to the formula (4), the capacity of a battery can be calculated through the change of the electric quantity and the change of the SOC during the charging process, which is named as C 充电 .

[0116] In the specific implementation, in the step S33, the preset charging SOH calculation formula is as follows:

[0117] The charging SOH of the battery = C 充电平均 / C 标称 * 100%.

[0118] Wherein, C 标称 is the nominal electric quantity value of the battery.

[0119] In the step S33, in the specific implementation, the results of three C 充电 are recorded, and then the average value is obtained to obtain C 充电平均 . Then, the charging SOH of the battery is calculated.

[0120] In the step S4, the discharging SOH of the battery is obtained, including the following steps:

[0121] In the step S41, during the direct current discharging process of the battery system, for any one battery in the battery system, each time the battery management system BMS detects that the battery meets the preset discharging condition, the preset battery discharging capacity acquisition operation is performed once to obtain a discharging capacity C 放电 of the battery (i.e., the capacity discharging result of the battery);

[0122] The preset discharging condition is specifically that the real-time SOC of the battery is less than a preset SOC threshold, the real-time discharging voltage is less than a preset discharging voltage threshold recorded in the discharging dynamic OCV table, the real-time charging current is less than a preset current discharging threshold recorded in the discharging dynamic OCV table, and the battery temperature is within a preset discharging temperature value range.

[0123] In the step S41, the temperature of the battery can be obtained through the temperature sensor installed on the surface of the battery.

[0124] In the step S41, the preset SOC threshold needs to consider the OCV curve characteristics of the battery. The iron lithium battery must be separated from the voltage platform period of the battery, and the SOC point with smaller discharging current can be selected according to the discharging power map of the ternary battery.

[0125] It should be noted that in step S41 , the preset discharge voltage threshold here is consistent with the preset discharge voltage threshold in the process of preparing the discharge dynamic OCV table, that is, the preset discharge voltage threshold recorded in the discharge dynamic OCV table.

[0126] In step S41 , in a specific implementation, the preset SOC threshold may be the SOC corresponding to the preset discharge voltage threshold recorded in the discharge dynamic OCV table.

[0127] In step S41, the preset discharge current threshold here is consistent with the preset discharge current threshold in the process of preparing the discharge dynamic OCV table, that is, the preset discharge current threshold recorded in the discharge dynamic OCV table, which is the preset discharge current threshold corresponding to the preset discharge voltage threshold, that is, the preset first discharge rate.

[0128] In step S41, the preset discharge temperature value range is the temperature range distributed in the process of preparing the discharge dynamic OCV table, that is, the maximum value of the preset discharge temperature value range is the maximum value of the multiple charging temperatures in step S2, and the minimum value of the preset discharge temperature value range is the minimum value of the multiple charging temperatures in step S2.

[0129] Step S42: When the discharge capacities C of multiple (for example, three) batteries are collected, 放电 When the discharge capacity of multiple batteries C 放电 Find the average value and get C 放电平均 ;

[0130] Step S43 , calculating the discharge SOH of the battery according to a preset discharge SOH calculation formula.

[0131] In the present invention, in a specific implementation, in step S41, the operation of obtaining the discharge capacity of the preset battery specifically includes the following steps:

[0132] Step S411: Record the real-time discharge voltage of the battery as the battery starting point voltage V1 放电 , and calculate the amount of electricity released by the battery at this time (specifically equal to the product of discharge time and discharge current), and record it as the battery starting point electricity Q1 放电 ;

[0133] Step S412: As the DC discharge process continues, when the battery no longer meets the preset discharge conditions, the real-time discharge voltage of the battery is recorded as the battery end point voltage V2. 放电 , and calculate the amount of electricity released by the battery at this time (specifically equal to the product of discharge time and discharge current), and record it as the battery end point electricity Q2 放电 ;

[0134] Step S413: The battery starting point power Q1放电 And the battery end point charge Q2 放电 Calculate the difference to obtain the amount of electricity released between the starting point and the end point ΔQ 放电 , and according to the battery starting point voltage V1 放电 and battery end point voltage V2 放电 , query the discharge dynamic OCV table obtained in step S2 to obtain the battery starting point voltage V1 放电 Corresponding battery starting point SOC 放电 And the battery end point voltage V2 放电 Corresponding battery end point SOC 放电 , calculate the battery's starting point SOC during discharge 放电 and battery end point SOC 放电 The difference ΔSOC 放电 ;

[0135] Step S414: Obtain the discharge capacity C of the battery according to the preset second calculation formula. 放电 .

[0136] In the present invention, according to the following formula (2):

[0137]

[0138] Therefore, for the battery discharge process, the following formula (5) can be obtained:

[0139]

[0140] Then the following formula (6) can be obtained, which is the preset second calculation formula:

[0141]

[0142] From this formula (6), the capacity of a battery can be calculated by the change in charge and SOC during the discharge process, which is named C 放电 .

[0143] In specific implementation, in step S43, the preset discharge SOH calculation formula is as follows:

[0144] Battery discharge SOH = C 放电平均 / C 标称 *100%;

[0145] Among them, C 标称 is the nominal capacity of the battery.

[0146] In step S43, in specific implementation, record C three times 放电 The results are then averaged to get C 放电平均Then the discharge SOH of the battery is calculated.

[0147] In step S5, according to the charge SOH of the battery obtained in step S3 and the discharge SOH of the battery obtained in step S4, and a preset calculation formula, the final SOH of the battery is obtained.

[0148] In step S5, specifically, the final SOH of the battery can be calculated from the charge SOH of the battery and the discharge SOH of the battery;

[0149] In step S5, the preset calculation formula is as follows:

[0150] The final SOH of the battery = charge SOH * x + discharge SOH * (1-x), formula (7);

[0151] In formula (7), x represents a weight factor, and the value range of x is 0-1.

[0152] In addition, in order to obtain the SOH of the entire power battery system, the application further includes step S6:

[0153] In step S6, for a power battery system, the final SOHs of a plurality of batteries in the power battery system are averaged, and the final SOH of the battery system is obtained.

[0154] Based on the above technical solution, for the SOH estimation method of the power battery provided by the application, the charge OCV and discharge OCV table are made, the charge process SOH is estimated, the discharge process SOH is estimated, and the estimation results of the two are fused together through a weight factor to obtain the final battery SOH and the power battery system SOH estimation result.

[0155] In summary, compared with the prior art, the SOH estimation method of the power battery provided by the application has the advantages of scientific design, reliable estimation of the battery system SOH through the relationship between the change of the electric quantity and the change of the SOC in the charging and discharging processes, small calculation amount, high efficiency, saving of a large amount of time, and great practical significance.

[0156] The above description is only the preferred embodiments of the application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the application.

Claims

1. A method for estimating the SOH of a power battery, applied to each battery in a battery system, characterized in that: The following steps are involved: Step S1, obtaining a charging OCV table; Step S2, obtaining a discharge OCV table; Step S3, obtaining the battery charging SOH: Step S4, obtaining the battery discharge SOH: Step S5, obtaining the final SOH of the battery based on the charging SOH of the battery obtained in step S3 and the discharging SOH of the battery obtained in step S4, as well as a preset calculation formula; The step S3 comprises the following steps: Step S31: During the DC charging process of the battery system, for any battery in the battery system, whenever the battery management system BMS detects that the battery meets the preset charging conditions, it executes a preset battery charging capacity acquisition operation to obtain a charging capacity C of the battery. 充电 ; Step S32: When the charging capacity C of multiple batteries is collected 充电 When the charging capacity of multiple batteries is C 充电 Find the average value and get C 充电平均 ; Step S33, calculating the charging SOH of the battery according to a preset charging SOH calculation formula; In step S31, the operation of obtaining the battery charging capacity is preset, including: Step S311: Record the real-time charging voltage of the battery as the battery starting point voltage V1 充电 , and calculate the amount of electricity charged into the battery at this time, and record it as the battery starting point electricity Q1 充电 ; Step S312: As the DC charging process continues, when the battery no longer meets the preset charging conditions, the real-time charging voltage of the battery is recorded as the battery end point voltage V2. 充电 , and calculate the amount of electricity charged into the battery at this time, and record it as the battery end point electricity Q2 充电 ; Step S313: The battery starting point power Q1 充电 And the battery end point charge Q2 充电 Calculate the difference to obtain the amount of charge ΔQ between the starting point and the end point 充电 , and according to the battery starting point voltage V1 充电 and battery end point voltage V2 充电 , query the charging dynamic OCV table obtained in step S1 to obtain the battery starting point voltage V1 充电 Corresponding battery starting point SOC 充电 And the battery end point voltage V2 充电 Corresponding battery end point SOC 充电 , calculate the battery starting point SOC of the battery during the charging process 充电 and battery end point SOC 充电 The difference ΔSOC 充电 ; Step S314: Obtain the battery charging capacity C according to the preset first calculation formula. 充电 ; The preset first calculation formula is as follows: ； In step S33, the preset charging SOH calculation formula is as follows: Battery charge SOH = C 充电平均 / C 标称 *100%; Among them, C 标称 is the nominal capacity of the battery; C 充电平均 For multiple C 充电 The average value of In step S31, the preset charging conditions are: the real-time charging voltage of the battery is greater than or equal to the preset charging voltage threshold recorded in the charging dynamic OCV table, the real-time charging current is less than the preset charging current threshold recorded in the charging dynamic OCV table, and the battery temperature is within the preset charging temperature value range; The preset charging current threshold recorded in the charging dynamic OCV table is the preset first discharge rate; The maximum value of the preset charging temperature value range is the maximum value among the multiple charging temperatures in step S1, and the minimum value of the preset charging temperature value range is the minimum value among the multiple charging temperatures in step S1; The step S1 comprises the following steps: In a constant temperature environment with multiple preset charging temperatures, the battery is subjected to multiple preset constant current charging operations, and the voltage value and SOC value of the battery during the charging process are collected in real time to obtain a set of charging dynamic OCV tables at different charging temperatures and different charging rates; the charging dynamic OCV table records the corresponding relationship between the battery's charging temperature, charging rate, charging time, voltage value during the charging process, and SOC during the charging process.

2. The method for estimating the SOH of a power battery according to claim 1, wherein: In step S1, the preset constant current charging operation is specifically as follows: First, the battery is discharged, and then the battery is charged with a constant current at a preset first charging rate to a preset charging voltage threshold. Then, the battery is charged with a constant current at a preset second charging rate to the battery's own charging cut-off voltage, i.e., fully charged. The preset first charging rate is greater than the preset second charging rate; Among them, discharging the battery is specifically: discharging the battery voltage to the discharge cut-off voltage of the battery; in step S1, the preset constant current charging operation is specifically: first, discharging the battery, and then charging the battery with a constant current at a 1C charging rate to a preset discharge voltage threshold, and then, charging the battery with a constant current at a 0.1C, 0.2, 0.3 or 0.5C charging rate to the battery's own charging cut-off voltage, that is, fully charged; in step S1, multiple constant temperature environments with different preset charging temperatures are specifically: multiple constant temperature environments with different preset charging temperatures with gradually increasing temperature values.

3. The method for estimating the SOH of a power battery according to claim 1, wherein: The step S2 comprises the following steps: Under multiple constant temperature environments with different preset discharge temperatures, the battery is subjected to multiple preset constant current discharge operations, and the battery voltage and SOC values ​​during the discharge process are collected in real time to obtain a set of discharge dynamic OCV tables at different discharge temperatures and different discharge rates; The discharge dynamic OCV table records the corresponding relationship between the battery's discharge temperature, discharge rate, discharge time, voltage value during the discharge process, and SOC during the discharge process; The preset constant current discharge operation is specifically as follows: first, the battery is subjected to a constant current discharge operation at a preset first discharge rate to discharge the battery to a preset discharge voltage threshold; then, the battery is subjected to a constant current discharge operation at a preset second discharge rate to discharge the battery to its own discharge cut-off voltage, i.e., emptying the battery; The preset first discharge rate is greater than the preset second discharge rate.

4. The method for estimating the SOH of a power battery according to claim 3, wherein: In step S2, the preset constant current discharge operation is specifically as follows: first, the battery is subjected to a constant current discharge operation at a 1C charge rate to discharge the battery to a preset discharge voltage threshold; then, the battery is subjected to a constant current discharge operation at a 0.3C, 0.5C or 0.8C discharge rate to discharge the battery to its own discharge cut-off voltage, i.e., emptying the battery; in step S2, multiple constant temperature environments with different preset discharge temperatures are specifically: multiple constant temperature environments with different preset discharge temperatures with gradually increasing temperature values.

5. The method for estimating the SOH of a power battery according to claim 1, wherein: The step S4 specifically includes the following steps: Step S41: During the DC discharge process of the battery system, for any battery in the battery system, whenever the battery management system BMS detects that the battery meets the preset discharge condition, it executes a preset battery discharge capacity acquisition operation to obtain a discharge capacity C of the battery. 放电 ; The preset discharge conditions are: the real-time SOC of the battery is less than the preset SOC threshold, the real-time discharge voltage is less than the preset discharge voltage threshold recorded in the discharge dynamic OCV table, the real-time charging current is less than the preset current discharge threshold recorded in the discharge dynamic OCV table, and the battery temperature is within the preset discharge temperature value range; In step S41, the preset current discharge threshold recorded in the discharge dynamic OCV table is the preset first discharge rate; In step S41, the maximum value of the preset discharge temperature value range is the maximum value of the multiple charging temperatures in step S2, and the minimum value of the preset discharge temperature value range is the minimum value of the multiple charging temperatures in step S2; Step S42: When the discharge capacity C of multiple batteries is collected 放电 When the discharge capacity of multiple batteries C 放电 Find the average value and get C 放电平均 ; Step S43 , calculating the discharge SOH of the battery according to a preset discharge SOH calculation formula.

6. The method for estimating the SOH of a power battery according to claim 5, wherein: In step S41, the operation of obtaining the discharge capacity of the battery is preset, specifically including the following steps: Step S411: Record the real-time discharge voltage of the battery as the battery starting point voltage V1 放电 , and calculate the amount of electricity released by the battery at this time, and record it as the battery starting point electricity Q1 放电 ; Step S412: As the DC discharge process continues, when the battery no longer meets the preset discharge conditions, the real-time discharge voltage of the battery is recorded as the battery end point voltage V2. 放电 , and calculate the amount of electricity released by the battery at this time, and record it as the battery end point electricity Q2 放电 ; Step S413: The battery starting point power Q1 放电 And the battery end point charge Q2 放电 Calculate the difference to obtain the amount of electricity released between the starting point and the end point ΔQ 放电 , and according to the battery starting point voltage V1 放电 and battery end point voltage V2 放电 , query the discharge dynamic OCV table obtained in step S2 to obtain the battery starting point voltage V1 放电 Corresponding battery starting point SOC 放电 And the battery end point voltage V2 放电 Corresponding battery end point SOC 放电 , calculate the battery's starting point SOC during discharge 放电 and battery end point SOC 放电 The difference ΔSOC 放电 ; Step S414: Obtain the discharge capacity C of the battery according to the preset second calculation formula. 放电 ; The preset second calculation formula is as follows: ； In step S43, the preset discharge SOH calculation formula is as follows: Battery discharge SOH = C 放电平均 / C 标称 *100%; Among them, C 标称 is the nominal capacity of the battery.

7. The method for estimating the SOH of a power battery according to any one of claims 1 to 5, characterized in that: In step S5, the preset calculation formula is as follows: The final SOH of the battery = charging SOH*x+discharging SOH*(1-x); In the formula, x represents the weight factor, and the value range of x is 0~1.

Images