Method and device for measuring state of charge of battery and vehicle

Abstract

The invention provides a method and device for measuring the state of charge of a battery and a vehicle, and the method comprises the steps: obtaining a first curve of the state of charge and the open-circuit voltage of the battery in a charging process, and obtaining a second curve of the state of charge and the open-circuit voltage of the battery in a discharging process; obtaining a third curve of the state of charge and the open-circuit voltage of the battery according to the average value of the first curve and the second curve; obtaining an actual measurement value of the open-circuit voltage of the battery; obtaining a hysteresis correction value of the open-circuit voltage of the battery; obtaining a true value of the open-circuit voltage of the battery according to the actual measurement value of the open-circuit voltage and the hysteresis correction value of the open-circuit voltage; and substituting the true value of the open-circuit voltage into the third curve to obtain a charge state correction value of the battery. According to the scheme, the actual measurement value of the open-circuit voltage of the battery is subjected to hysteresis state correction, so that the finally obtained charge state correction value is closer to a real value.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy sodium batteries, and in particular to a method for measuring the state of charge of a battery, a measuring device and a vehicle. Background Art

[0002] As a core component of electric vehicles, one of the main functions of the battery management system (BMS) is to accurately estimate the battery's state of charge (SOC) so that passengers can accurately grasp the remaining battery power and plan driving routes and charging plans reasonably. Among them, the open circuit voltage (OCV) method is a commonly used state of charge estimation method. Its basic principle is to estimate the current state of charge based on the open circuit voltage measurement value of the battery by looking up the table, and display the remaining power on the dashboard. However, during the charging and discharging tests, the open circuit voltage of the battery at the same state of charge will be inconsistent ( Figure 1 The figure shows that the SOC-OCV curves of the battery for charge and discharge are not the same, and the two form a hysteresis interval. This leads to hysteresis in the open circuit voltage of the battery. Hysteresis refers to the fact that during the charge and discharge process of the battery, the actual open circuit voltage value may be different from the measured voltage value, that is, the actual open circuit voltage may be in a state of Figure 1 Any point within the hysteresis interval shown results in a large difference between the estimated value and the actual value of the state of charge, which is not conducive to the occupants to plan the driving route reasonably.

[0003] In the prior art, there are usually two ways to estimate the state of charge of a battery. One is to select a fixed SOC-OCV curve. For example, when the current operating condition is discharge, the discharge SOC-OCV curve is selected, and when the current operating condition is charging, the charging SOC-OCV curve is selected. Although this method is simple and easy to implement, it ignores the hysteresis phenomenon of the open circuit voltage during the above-mentioned charging and discharging process, which may cause a large estimation error in the state of charge. The other is to add a correction value threshold judgment on the basis of the correction of the open circuit voltage. If the correction value is within a certain threshold range, the current battery's open circuit voltage correction value is used as the current battery's open circuit voltage value. This method of open circuit only filters a part of the possible abnormal corrections by the size of the correction amplitude, but it cannot reduce the error of the correction of the open circuit voltage. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of large error in the estimation of the state of charge of the battery in the prior art due to the hysteresis phenomenon of the open circuit voltage, thereby providing a method, a measuring device and a vehicle for measuring the state of charge of a battery.

[0005] In order to solve the above problems, the present invention provides a method for measuring the state of charge of a battery, comprising: obtaining a first curve of the state of charge and the open circuit voltage of the battery during a charging process, and obtaining a second curve of the state of charge and the open circuit voltage of the battery during a discharging process; obtaining a third curve of the state of charge and the open circuit voltage of the battery according to the average value of the first curve and the second curve; obtaining an actual measured value of the open circuit voltage of the battery; obtaining a hysteresis correction value of the open circuit voltage of the battery; obtaining a true value of the open circuit voltage of the battery according to the actual measured value of the open circuit voltage and the hysteresis correction value of the open circuit voltage; substituting the true value of the open circuit voltage into the third curve to obtain a corrected value of the state of charge of the battery.

[0006] Optionally, obtaining a first curve of the state of charge and open circuit voltage of the battery during the charging process includes: charging the battery to a preset capacity; measuring the open circuit voltage after the battery is left to stand, and obtaining a corresponding relationship between the state of charge of the battery and the open circuit voltage; repeatedly charging the battery and measuring the open circuit voltage to obtain the first curve.

[0007] Optionally, obtaining a second curve of the state of charge and open circuit voltage of the battery during the discharge process includes: discharging the battery to a preset capacity; measuring the open circuit voltage after the battery is left to stand, and obtaining a corresponding relationship between the state of charge of the battery and the open circuit voltage; repeatedly discharging the battery and measuring the open circuit voltage to obtain the second curve.

[0008] Optionally, obtaining a third curve of the battery's state of charge and open circuit voltage based on the average value of the first curve and the second curve includes: obtaining a first open circuit voltage value on the first curve at a certain state of charge, and a second open circuit voltage value on the second curve; obtaining the average value of the first open circuit voltage value and the second open circuit voltage value to obtain a third open circuit voltage value; obtaining the third curve based on the correspondence between multiple groups of charge states and the third open circuit voltage values.

[0009] Optionally, obtaining the true value of the open circuit voltage of the battery according to the actual measured value of the open circuit voltage and the hysteresis correction value of the open circuit voltage includes: OCV_est=OCV_meas+OCV_hust; wherein OCV_est is the true value of the open circuit voltage, OCV_meas is the actual measured value of the open circuit voltage, and OCV_hyst is the hysteresis correction value of the open circuit voltage.

[0010] Optionally, the hysteresis correction value is obtained by the following formula: OCV hyst =M0*s+M*h; where OCV hyst is the hysteresis correction value, M0 is the instantaneous hysteresis value of the open circuit voltage, s is the direction of change of the instantaneous hysteresis with the current direction, which takes a value of 1 or -1, M is the maximum hysteresis offset of the open circuit voltage, and h is the offset coefficient, which takes a value in the range of -1 to 1.

[0011] Optionally, the instantaneous hysteresis value M0 of the open circuit voltage is obtained in the following manner: under a certain state of charge, measuring a fourth open circuit voltage value of the battery; charging or discharging the battery for a preset time; after the battery is left to stand, measuring a fifth open circuit voltage value of the battery; and obtaining the instantaneous hysteresis value of the open circuit voltage based on the difference between the fourth open circuit voltage value and the fifth open circuit voltage value.

[0012] Optionally, the instantaneous hysteresis with the change direction of the current direction s is obtained by the following formula: Among them, k is the time and i is the current.

[0013] Optionally, the hysteresis offset maximum value M of the open circuit voltage is obtained by the following formula: Wherein, OCV_charge is the maximum hysteresis offset of the open circuit voltage on the first curve, and OCV_discharge is the maximum hysteresis offset of the open circuit voltage on the second curve.

[0014] Optionally, the offset coefficient h is obtained by the following formula: h[k]=e -|γ·ΔSOC| h[k-1]-(1-e -|γ·ΔSOC| )sgn(i); Among them, k is the time, i is the current, and Q is the battery capacity.

[0015] Optionally, the hysteresis correction value and the true value of the open circuit voltage of the battery are obtained by the following formula: ΔOCV_hyst=K*ΔSOC; OCV_est=OCV_meas+∑ΔOCV_hyst; wherein, OCV_est is the true value of the open circuit voltage, OCV_meas is the actual measured value of the open circuit voltage, OCV_hyst is the hysteresis correction value of the open circuit voltage, K is the coefficient, i is the current, and Q is the battery capacity.

[0016] The present invention also provides a device for measuring the state of charge of a battery, comprising: a measuring module, suitable for obtaining the actual measured value of the open circuit voltage of the battery; a control module, communicatively connected to the measuring module, and the control module is used to execute the above-mentioned method for measuring the state of charge of the battery.

[0017] The present invention also provides a vehicle, comprising the battery state of charge measuring device as described above.

[0018] The present invention has the following advantages:

[0019] By using the technical solution of the present invention, the third curve is obtained by taking the average of the first curve and the second curve, and the third curve represents the initial state of the open circuit voltage without hysteresis offset. Then the actual measured value and hysteresis correction value of the open circuit voltage of the battery are obtained, and the true value of the open circuit voltage is obtained. The true value of the open circuit voltage is substituted into the third curve, and finally the state of charge correction value of the battery is obtained. In the above scheme, by performing hysteresis state correction on the actual measured value of the open circuit voltage of the battery, the state of charge correction value finally obtained is closer to the true value, so the battery power evaluation is more accurate, which is conducive to the occupants to accurately plan the driving strategy. Therefore, the technical solution of the present invention solves the defect that the battery in the prior art has a large error in estimating the state of charge due to the hysteresis phenomenon of the open circuit voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram showing a SOC-OCV curve of a battery in the prior art after charging and discharging;

[0022] Figure 2 A schematic diagram showing a first curve, a second curve and a third curve in the measurement method of the present invention is shown;

[0023] Figure 3 A schematic diagram showing how to obtain the true value of the open circuit voltage through the measured value of the open circuit voltage and the hysteresis correction value in the present invention;

[0024] Figure 4 A schematic flow chart showing a method for measuring the state of charge of a battery according to the present invention is shown;

[0025] Figure 5 Shows Figure 4 A further schematic diagram of a process for obtaining a first curve in the test method;

[0026] Figure 6 Shows Figure 4 A further schematic diagram of the process of obtaining the second curve by the test method;

[0027] Figure 7 Shows Figure 4 A further schematic diagram of the process of obtaining the third curve in the test method.

[0028] Description of reference numerals:

[0029] 10, first curve; 20, second curve; 30, third curve DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Embodiment 1:

[0035] like Figures 2 to 4 As shown, according to the first embodiment of the method for measuring the state of charge of a battery of the present application, the method includes:

[0036] S10: obtaining a first curve 10 of the state of charge and the open circuit voltage of the battery during the charging process, and obtaining a second curve 20 of the state of charge and the open circuit voltage of the battery during the discharging process;

[0037] S20: Obtaining a third curve 30 of the state of charge and the open circuit voltage of the battery according to the average value of the first curve 10 and the second curve 20;

[0038] S30: Obtaining an actual measured value of the open circuit voltage of the battery;

[0039] S40: Obtaining a hysteresis correction value of an open circuit voltage of the battery;

[0040] S50: Obtaining a true value of the open circuit voltage of the battery according to the actual measured value of the open circuit voltage and the hysteresis correction value of the open circuit voltage;

[0041] S60: Substitute the actual value of the open circuit voltage into the third curve 30 to obtain a corrected value of the state of charge of the battery.

[0042] Using the technical solution of this embodiment, by taking the average of the first curve 10 and the second curve 20, a third curve 30 is obtained, and the third curve 30 represents the initial state of the open circuit voltage without hysteresis offset. Then the actual measured value and hysteresis correction value of the open circuit voltage of the battery are obtained, and the true value of the open circuit voltage is obtained. The true value of the open circuit voltage is substituted into the third curve 30, and finally the state of charge correction value of the battery is obtained. In the above scheme, by correcting the hysteresis state of the actual measured value of the open circuit voltage of the battery, the state of charge correction value finally obtained is closer to the true value, so the battery power evaluation is more accurate, which is conducive to the occupants to accurately plan the driving strategy. Therefore, the technical solution of this embodiment solves the defect that the battery in the prior art has a large error in estimating the state of charge due to the hysteresis phenomenon of the open circuit voltage.

[0043] First of all, it should be noted that the battery's state of charge (SOC) refers to the ratio of the remaining capacity of a battery after it has been used for a period of time or has been left unused for a long time to its capacity in a fully charged state, usually expressed as a percentage. The value range is 0 to 1. When SOC is 0, it means that the battery is fully discharged, and when SOC is 1, it means that the battery is fully charged.

[0044] Furthermore, the open circuit voltage (OCV) of a battery is the difference between the electrode potential of the positive electrode and the electrode potential of the negative electrode of the battery when the battery is disconnected (ie, when no current passes through the two electrodes).

[0045] Therefore, the relationship curve between the battery's state of charge and open circuit voltage is also called the SOC-OCV curve.

[0046] In the above step S10, it is necessary to obtain a first curve 10 of the state of charge and the open circuit voltage of the battery during the charging process, and to obtain a second curve 20 of the state of charge and the open circuit voltage of the battery during the discharging process.

[0047] Furthermore, the first curve 10 is also the SOC-OCV curve of the battery during the charging process, and the second curve 20 is also the SOC-OCV curve of the battery during the discharging process. Figure 2It can be seen that the first curve 10 and the second curve 20 do not overlap, so a hysteresis interval is enclosed between the first curve 10 and the second curve 20 .

[0048] Further, since the first curve 10 and the second curve 20 are both obtained from the measured values ​​when the open circuit voltage of the battery has a hysteresis offset, in step S20, the first curve 10 and the second curve 20 are averaged to form the third curve 30. By averaging the first curve 10 and the second curve 20, the hysteresis offset of the open circuit voltage can be reduced as much as possible, so the third curve 30 represents the initial state of the open circuit voltage of the battery without a hysteresis offset, that is, the third curve 30 is the initial SOC-OCV curve of the open circuit voltage of the battery.

[0049] Further, in step S30, after the battery is sufficiently left to rest, the open circuit voltage of the battery is measured and used as the actual measured value of the open circuit voltage.

[0050] Further, in step S40, it is necessary to obtain a hysteresis correction value of the open circuit voltage to correct the actual measured value of the open circuit voltage. In the first embodiment, the hysteresis correction value needs to take into account the instantaneous change and long-term hysteresis of the open circuit voltage of the battery, which will be described in detail below. In step S50, the actual measured value of the open circuit voltage is corrected by the hysteresis correction value, and the true value of the open circuit voltage is obtained.

[0051] Finally, in step S60, the actual value of the open circuit voltage is substituted into the third curve 30, and the final state of charge correction value is obtained by looking up the table. Since the open circuit voltage of the battery has been corrected, the corrected state of charge value obtained is closer to the actual state of the battery capacity, and can provide more accurate battery information to the occupants.

[0052] like Figure 5 As shown, in the technical solution of this embodiment, obtaining a first curve 10 of the state of charge and the open circuit voltage of the battery during the charging process, that is, the above-mentioned step S10 includes:

[0053] S11: charging the battery to a preset capacity;

[0054] S12: measuring the open circuit voltage of the battery after it is at rest, and obtaining a corresponding relationship between the battery state of charge and the open circuit voltage;

[0055] S13: Repeat charging the battery and measuring the open circuit voltage to obtain a first curve 10.

[0056] Specifically, the first curve 10 is obtained by performing a charging experiment on a battery.

[0057] In step S11 , the battery is charged to a preset capacity so that the state of charge of the battery changes.

[0058] For example, a battery may be charged to 5 percent of capacity, which increases the battery's state of charge by 0.05.

[0059] Of course, those skilled in the art can determine the specific capacity of the battery to be charged after executing step S11 once according to actual needs. For example, the battery can be charged to 1%, 10%, etc. Those skilled in the art can understand that the smaller the preset capacity of the battery to be charged, the more accurate the first curve 10 finally obtained after fitting.

[0060] In step S12, after the battery is charged to a preset capacity, the battery needs to be allowed to stand for a long time, and then the open circuit voltage of the battery is measured to obtain the relationship between the battery's current state of charge and the corresponding open circuit voltage.

[0061] Furthermore, after the battery is charged to a preset capacity, the specific length of time for which the battery needs to be left to rest sufficiently can be determined by those skilled in the art based on the specific model of the battery and actual needs.

[0062] In step S13 , the battery needs to be charged and measured multiple times, so as to obtain multiple sets of relationships between the state of charge and the open circuit voltage, and finally fit the first curve 10 .

[0063] For example, the battery can be fully discharged first, that is, the state of charge is reduced to 0. Then the battery is charged to 5% of its capacity, that is, the state of charge is increased to 0.05, and after the battery is fully rested, the corresponding open circuit voltage value is measured.

[0064] The battery is charged 20 times (each time the battery is charged to 5% of its capacity), that is, the battery is fully charged, and the state of charge is raised to 1. 20 sets of corresponding relationships between the state of charge and the open circuit voltage are obtained, and these corresponding relationships are represented as points in the coordinate system, and a first curve 10 is obtained by fitting multiple points.

[0065] like Figure 6 As shown, in the technical solution of this embodiment, a second curve 20 of the state of charge and the open circuit voltage of the battery during the discharge process is obtained, that is, the above-mentioned step S10 also includes:

[0066] S14: Discharge the battery to a preset capacity;

[0067] S15: measuring the open circuit voltage of the battery after it is at rest, and obtaining a corresponding relationship between the battery state of charge and the open circuit voltage;

[0068] S16: Repeat discharging the battery and measuring the open circuit voltage to obtain a second curve 20.

[0069] Specifically, the second curve 20 is obtained by performing a discharge experiment on the battery.

[0070] In step S14, the battery is discharged by a preset capacity so that the state of charge of the battery changes.

[0071] For example, a battery may be discharged by 5 percent of its capacity, which reduces the battery's state of charge by 0.05.

[0072] Of course, those skilled in the art can determine the specific capacity of the battery to be discharged after executing step S14 once according to actual needs. For example, the battery can be discharged by 1%, 10%, etc. Those skilled in the art can understand that the smaller the preset capacity of the battery discharge, the more accurate the second curve 20 finally obtained after fitting.

[0073] In step S15, after the battery is discharged to a preset capacity, the battery needs to be allowed to stand for a long time, and then the open circuit voltage of the battery is measured to obtain the relationship between the corresponding open circuit voltage of the battery under the current state of charge.

[0074] Furthermore, after the battery is discharged to a preset capacity, the specific length of time for which the battery needs to be left to rest sufficiently can be determined by those skilled in the art based on the specific model of the battery and actual needs.

[0075] In step S16 , the battery needs to be discharged and measured multiple times, so as to obtain multiple sets of relationships between the state of charge and the open circuit voltage, and finally fit the second curve 20 .

[0076] For example, the battery can be fully charged first, that is, the initial value of the state of charge is reduced to 100. Then the battery is discharged by 5% of its capacity, that is, the state of charge is reduced to 99.5, and after the battery is fully rested, the corresponding open circuit voltage value is measured.

[0077] The battery is discharged 20 times (5% of the battery capacity is discharged each time), that is, the battery is emptied and the state of charge is reduced to 0. 20 sets of corresponding relationships between the state of charge and the open circuit voltage are obtained, and these corresponding relationships are represented as points in the coordinate system, and a second curve 20 is obtained by fitting multiple points.

[0078] like Figure 7 As shown, in the technical solution of this embodiment, according to the average value of the first curve 10 and the second curve 20, obtaining the third curve 30 of the state of charge and the open circuit voltage of the battery includes:

[0079] S21: obtaining a first open circuit voltage value 10 on the first curve and a second open circuit voltage value 20 on the second curve at a certain state of charge;

[0080] S22: Obtain an average value of the first open circuit voltage value and the second open circuit voltage value to obtain a third open circuit voltage value;

[0081] S23: obtaining a third curve 30 according to the correspondence between the plurality of groups of charge states and the third open circuit voltage value;

[0082] Specifically, since the open circuit voltage of the battery has hysteresis in both the charging and discharging tests of the battery, the first curve 10 and the second curve 20 cannot represent the initial state in which the open circuit voltage has no hysteresis offset. In this embodiment, the average value of each point on the first curve 10 and the second curve 20 is taken to obtain the third curve 30, which is used to represent the initial state in which the open circuit voltage has no offset.

[0083] In step S21 , a specific state of charge value is first selected, and two open circuit voltage values ​​are obtained on the first curve 10 and the second curve 20 .

[0084] For example, when the state of charge is 0.05, a first open circuit voltage value and a second open circuit voltage value can be obtained on the first curve 10 , respectively.

[0085] In step S22, the first open circuit voltage value and the second open circuit voltage value are summed and divided by 2 to obtain a third open circuit voltage value. The third open circuit voltage value is a value corresponding to the state of charge of 0.05.

[0086] In step S23 , multiple points are selected in the state of charge range from 0 to 1, and multiple sets of corresponding relationships between the state of charge and the third open circuit voltage value are obtained. These corresponding relationships are represented by points in the coordinate system, and multiple points are fitted to form a third curve 30 .

[0087] For example, 20 state of charge points may be uniformly selected at intervals of 0.05 within the range of the state of charge from 0 to 1.

[0088] like Figure 3 As shown, in the technical solution of this embodiment, obtaining the true value of the open circuit voltage of the battery according to the actual measured value of the open circuit voltage and the hysteresis correction value of the open circuit voltage includes:

[0089] OCV_est=OCV_meas+OCV_hyst;

[0090] Among them, OCV_est is the true value of the open circuit voltage, OCV_meas is the actual measured value of the open circuit voltage, and OCV_hyst is the hysteresis correction value of the open circuit voltage.

[0091] Specifically, OCV_meas is the open circuit voltage value measured after the battery is fully rested after charging or discharging. OCV_hyst needs to take into account the instantaneous hysteresis change and long-term hysteresis of the battery. After OCV_meas and OCV_hyst are added, OCV_est is obtained, which is the true value of the open circuit voltage.

[0092] Furthermore, in the technical solution of this embodiment, the hysteresis correction value OCV_hyst of the open circuit voltage is obtained by the following formula:

[0093] OCV hyst =M0*s+M*h;

[0094] Among them, OCV hyst is the hysteresis correction value, M0 is the instantaneous hysteresis value of the open circuit voltage, s is the direction of change of the instantaneous hysteresis with the current direction, which takes a value of 1 or -1, M is the maximum hysteresis offset of the open circuit voltage, and h is the offset coefficient, which takes a value in the range of -1 to 1.

[0095] Specifically, M0*s is used to describe the instantaneous hysteresis of the battery as the current changes and the direction of the instantaneous change. Among them, M0 is measured by experiment, s is calculated by formula, and its value is -1 or 1, representing the direction. M*h is used to describe the long-term hysteresis of the open circuit voltage. Among them, M is calculated by formula, and M represents the maximum offset that the hysteresis offset of the open circuit voltage can reach. h is obtained by calculation, and h is a function related to the SOC change at the previous moment and the current moment, and the value of h is in the range of -1 to 1 (including -1 and 1).

[0096] The following is a detailed introduction.

[0097] In the hysteresis correction value of the open circuit voltage, the instantaneous hysteresis value M0 of the open circuit voltage is obtained by:

[0098] Under a certain state of charge, measuring a fourth open circuit voltage value of the battery; charging or discharging the battery for a preset time;

[0099] After the battery is left to rest, the fifth open circuit voltage value of the battery is measured;

[0100] An instantaneous hysteresis value of the open circuit voltage is obtained according to a difference between the fourth open circuit voltage value and the fifth open circuit voltage value.

[0101] Specifically, the preset value duration is a short time, for example, the preset duration is 0.1 second, 0.5 second or one second.

[0102] The battery needs to be tested for instantaneous charging and instantaneous discharging at a certain state of charge. The following examples illustrate:

[0103] When the state of charge of the battery is 0.5, the fourth open circuit voltage value of the battery is first measured after it has been fully rested. Then the battery is charged for 0.5 seconds, and after charging, the battery is fully rested, and the fifth open circuit voltage value of the battery is measured. The instantaneous hysteresis value of the open circuit voltage is obtained by taking the difference between the fourth open circuit voltage value and the fifth open circuit voltage value.

[0104] When the state of charge of the battery is 0.5, the fourth open circuit voltage value of the battery is first measured after it has been fully rested. Then the battery is discharged for 0.5 seconds, and after discharge, the battery is fully rested, and the fifth open circuit voltage value of the battery is measured. The discharge instantaneous hysteresis value of the open circuit voltage is obtained by taking the difference between the fourth open circuit voltage value and the fifth open circuit voltage value.

[0105] Furthermore, when the state of charge is in the range of 0 to 1, multiple points may be uniformly selected to perform the above-mentioned battery instantaneous charge and discharge experiment. For example, 20 points may be uniformly selected at intervals of 0.05, and the battery instantaneous charge experiment and instantaneous discharge experiment may be performed at these 20 points.

[0106] When the battery's pre-operating condition is charging, M0 selects the value of the instantaneous charging experiment. When the battery's pre-operating condition is discharging, M0 selects the value of the instantaneous discharging experiment.

[0107] Further, in the technical solution of this embodiment, the direction s of the change of the instantaneous hysteresis with the current direction is obtained by the following formula:

[0108] Among them, k is the time and i is the current.

[0109] Specifically, sgn is a sign function. When the current is positive, s outputs 1, and when the current is negative, s outputs -1. And the current cannot be 0. When the current is 0, the value of s is the output value of the previous moment (when the current is not 0).

[0110] Those skilled in the art can understand that when s is 1, the battery is instantaneously charged, and when s is -1, the battery is instantaneously discharged.

[0111] Furthermore, in the technical solution of this embodiment, the maximum value M of the hysteresis offset of the open circuit voltage is obtained by the following formula:

[0112]

[0113] OCV_charge is the maximum hysteresis offset of the open circuit voltage on the first curve 10 , and OCV_discharge is the maximum hysteresis offset of the open circuit voltage on the second curve 20 .

[0114] Specifically, Figure 2The range enclosed by the first curve 10 and the second curve 20 is the maximum range of the hysteresis offset of the open circuit voltage. Therefore, the open circuit voltage has a maximum charge offset OCV_charge on the first curve 10 , and has a maximum discharge offset OCV_discharge on the second curve 20 .

[0115] Therefore, in this embodiment, the maximum hysteresis offset value M of the road voltage is taken as the average value of the maximum charge offset OCV_charge and the maximum discharge offset OCV_discharge.

[0116] Furthermore, in the technical solution of this embodiment, the offset coefficient h is obtained by the following formula:

[0117] h[k]=e -|γ·ΔSOC| h[k-1]-(1-e -|γ·ΔSOC| )sgn(i);

[0118]

[0119] Among them, k is the time, i is the current, and Q is the battery capacity.

[0120] The applicant found through experimental data that the hysteresis offset shape of the open circuit voltage in the coordinate system is similar to an exponential function, so the above function h[k] is obtained by fitting. The value of h[k] is related to the change in the state of charge, that is, the input includes ΔSOC. ΔSOC represents the change in the state of charge per unit time.

[0121] As mentioned above, sgn is a sign function.

[0122] Furthermore, the value of h is in the range of -1 to 1. That is, the long-term hysteresis of the open circuit voltage includes: the open circuit voltage has no hysteresis offset (h has a value of 0), the open circuit voltage has a maximum charging hysteresis offset (h has a value of 1), the open circuit voltage has an offset less than the maximum charging hysteresis (h has a value between 0 and 1), the open circuit voltage has a maximum discharge hysteresis offset (h has a value of -1), and the open circuit voltage has an offset less than the maximum discharge hysteresis (h has a value between -1 and.).

[0123] Embodiment 2:

[0124] The difference between the second embodiment of the method for measuring the nuclear power state of a battery according to the present application and the above-mentioned first embodiment is that the calculation of the hysteresis correction value of the open circuit voltage and the true value of the open circuit voltage is different.

[0125] Specifically, in the second embodiment, the hysteresis correction value and the true value of the open circuit voltage of the battery are obtained by the following formula:

[0126] ΔOCV_hyst=K*ΔSOC;

[0127]

[0128] OCV_est=OCV_meas+∑ΔOCV_hyst;

[0129] Among them, OCV_est is the true value of the open circuit voltage, OCV_meas is the actual measured value of the open circuit voltage, OCV_hyst is the hysteresis correction value of the open circuit voltage, K is the coefficient, i is the current, and Q is the battery capacity.

[0130] From the above formula, it can be seen that in the second embodiment, the hysteresis offset of the open circuit voltage is simplified into a linear system, and the maximum value of the unit offset is defined, that is, the above coefficient K. When the state of charge changes by one unit, the open circuit voltage shifts by one unit in a certain direction.

[0131] Furthermore, in the second embodiment, the shift direction of the open circuit voltage is consistent with the change direction of the state of charge, that is, when the state of charge increases, the shift direction of the open circuit voltage is positive, and when the state of charge decreases, the shift direction of the open circuit voltage is negative.

[0132] In the second embodiment, the hysteresis offset of the open circuit voltage is simplified into a linear system, which is more convenient for calculation. However, the second embodiment does not consider the instantaneous hysteresis and long-term hysteresis of the open circuit voltage, and does not consider the change law of the long-term hysteresis of the open circuit voltage that is approximately an exponential function. Therefore, the correction accuracy of the state of charge will be lower than the technical solution of the first embodiment.

[0133] The present application also provides a device for measuring the state of charge of a battery, and an embodiment of the device includes a measuring module and a control module. The measuring module is suitable for obtaining an actual measurement value of the open circuit voltage of the battery. The control module is communicatively connected to the measuring module, and the control module is used to execute the above-mentioned method for measuring the state of charge of the battery.

[0134] The present application also provides a vehicle, and an embodiment of the vehicle includes the above-mentioned charge state measurement device.

[0135] Optionally, the vehicle is a new energy electric vehicle.

[0136] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for measuring the state of charge of a battery, characterized in that: include: Obtaining a first curve (10) of the state of charge and the open circuit voltage of the battery during the charging process, and obtaining a second curve (20) of the state of charge and the open circuit voltage of the battery during the discharging process; Obtaining a third curve (30) of the state of charge and open circuit voltage of the battery according to an average value of the first curve (10) and the second curve (20); Obtaining an actual measured value of an open circuit voltage of the battery; Obtaining a hysteresis correction value of an open circuit voltage of the battery; Obtaining a true value of the open circuit voltage of the battery according to an actual measured value of the open circuit voltage and a hysteresis correction value of the open circuit voltage; The actual value of the open circuit voltage is substituted into the third curve (30) to obtain a corrected value of the state of charge of the battery.

2. The measuring method according to claim 1, characterized in that: Obtaining a first curve (10) of the state of charge and the open circuit voltage of the battery during the charging process includes: Charging the battery to a preset capacity; After the battery is at rest, the open circuit voltage is measured to obtain a corresponding relationship between the battery state of charge and the open circuit voltage; The battery is charged and the open circuit voltage is measured repeatedly to obtain the first curve (10).

3. The measuring method according to claim 1, characterized in that: Obtaining a second curve (20) of the state of charge and the open circuit voltage of the battery during the discharge process includes: Discharging the battery to a preset capacity; After the battery is at rest, the open circuit voltage is measured to obtain a corresponding relationship between the battery state of charge and the open circuit voltage; The battery is discharged and the open circuit voltage is measured repeatedly to obtain the second curve (20).

4. The measuring method according to any one of claims 1 to 3, characterized in that: Obtaining a third curve (30) of the state of charge and the open circuit voltage of the battery according to the average value of the first curve (10) and the second curve (20) comprises: Obtaining a first open circuit voltage value on the first curve (10) at a certain state of charge, and a second open circuit voltage value on the second curve (20); Obtain an average of the first open circuit voltage value and the second open circuit voltage value to obtain a third open circuit voltage value; The third curve (30) is obtained according to the correspondence between the multiple groups of charge states and the third open circuit voltage value.

5. The measuring method according to any one of claims 1 to 3, characterized in that: Obtaining the true value of the open circuit voltage of the battery according to the actual measured value of the open circuit voltage and the hysteresis correction value of the open circuit voltage includes: OCV_est=OCV_meas+OCV_hyst; Wherein, the OCV_est is the true value of the open circuit voltage, the OCV_meas is the actual measured value of the open circuit voltage, and the OCV_hyst is the hysteresis correction value of the open circuit voltage.

6. The measuring method according to claim 5, characterized in that: The hysteresis correction value is obtained by the following formula: CVC hyst =M0*s+M*h; Wherein, the OCV hyst is the hysteresis correction value, M0 is the instantaneous hysteresis value of the open circuit voltage, s is the direction of change of the instantaneous hysteresis with the current direction, and takes a value of 1 or -1, M is the maximum hysteresis offset of the open circuit voltage, and h is the offset coefficient, and takes a value in the range of -1 to 1.

7. The measuring method according to claim 6, characterized in that: The instantaneous hysteresis value M0 of the open circuit voltage is obtained by: Under a certain state of charge, measuring a fourth open circuit voltage value of the battery; Charge or discharge the battery for a preset time; After the battery is left to rest, the fifth open circuit voltage value of the battery is measured; The instantaneous hysteresis value of the open circuit voltage is obtained according to the difference between the fourth open circuit voltage value and the fifth open circuit voltage value.

8. The measuring method according to claim 6, characterized in that: The instantaneous hysteresis changes with the direction of the current by the following formula: Wherein, k is the time, and i is the current.

9. The measuring method according to claim 6, characterized in that: The maximum value M of the hysteresis offset of the open circuit voltage is obtained by the following formula: The OCV_charge is the maximum hysteresis offset of the open circuit voltage on the first curve (10), and the OCV_discharge is the maximum hysteresis offset of the open circuit voltage on the second curve (20).

10. The measuring method according to claim 6, characterized in that: The offset coefficient h is obtained by the following formula: h[k]=e -|γ·ΔSOC| h[k-1]-(1-e -|γ·ΔSOC| )sgn(i); Wherein, k is the time, i is the current, and Q is the battery capacity.

11. The measuring method according to claim 5, characterized in that: The hysteresis correction value and the true value of the open circuit voltage of the battery are obtained by the following formula: ΔOCV_hust=K*ΔSOC; OCV_est=OCV_meas+∑ΔOCV_hyst; Among them, the OCV_est is the true value of the open circuit voltage, the OCV_meas is the actual measured value of the open circuit voltage, the OCV_hyst is the hysteresis correction value of the open circuit voltage, the K is a coefficient, the i is the current, and the Q is the battery capacity.

12. A device for measuring the state of charge of a battery, characterized in that: include: A measuring module, adapted to obtain an actual measured value of an open circuit voltage of a battery; A control module is communicatively connected to the measurement module, and the control module is used to execute the method for measuring the state of charge of the battery as claimed in any one of claims 1 to 11.

13. A vehicle, characterized in that: A device for measuring the state of charge of a battery comprising the device as claimed in claim 12.

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