A method and device for predicting battery open circuit voltage and a battery pack

Abstract

The present invention discloses a prediction method, prediction device and battery pack for the open circuit voltage of a battery. The open circuit voltage of the battery is predicted when the absolute value of the current of the battery in the battery pack is not greater than the threshold current, that is, the open circuit voltage is predicted when the current of the battery is small, which can help improve the accuracy of the predicted open circuit voltage. In addition, the voltage of the battery is collected according to a preset collection period, the first difference between any two adjacent voltages is calculated, and the prediction coefficient is determined according to each first difference. Then, the open circuit voltage of the battery is predicted according to the prediction coefficient and the prediction formula, so that the open circuit voltage of the battery at any time in the future can be predicted, and the battery can be prevented from being stationary for a long time when predicting the open circuit voltage, and the open circuit voltage can be obtained in a shorter time.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and device for predicting a battery open circuit voltage, and a battery pack. Background Art

[0002] OCV (Open Circuit Voltage) refers to the potential difference between the positive and negative electrodes when the battery is open and not discharging. In a battery pack, the prediction of the battery's OCV helps to identify the battery's internal state and detect the battery's performance parameters, thereby better maintaining the battery. In addition, the prediction of the battery's OCV can also help users check the charging state, capacity, and aging of lithium batteries, thereby ensuring the best performance of lithium batteries. Therefore, how to predict the open circuit voltage of a battery has become an urgent problem to be solved. Summary of the invention

[0003] The embodiments of the present invention provide a method, a device and a battery pack for predicting the open circuit voltage of a battery, which are used to predict the open circuit voltage of a battery.

[0004] In a first aspect, an embodiment of the present invention provides a method for predicting an open circuit voltage of a battery, comprising:

[0005] When the absolute value of the current of the battery in the battery pack is not greater than the threshold current, the following process is performed:

[0006] Collecting the voltage of the battery according to a preset collection period, sorting the collected voltages according to the order of collection time, and calculating a first difference between any two adjacent voltages;

[0007] determining a prediction coefficient according to each of the first differences;

[0008] According to the prediction coefficient and the prediction formula, the open circuit voltage of the battery at a first moment in the future is predicted; wherein the prediction formula is used to describe the relationship between the first moment, the prediction coefficient, the preset acquisition cycle, the voltage collected in the last preset acquisition cycle, and the moment of the last preset acquisition cycle.

[0009] In a second aspect, an embodiment of the present invention provides a device for predicting an open circuit voltage of a battery, comprising:

[0010] A memory for storing program instructions;

[0011] The processor is used to call the program instructions stored in the memory and execute the prediction method introduced in the first aspect according to the obtained program.

[0012] In a third aspect, an embodiment of the present invention provides a battery pack, comprising: a battery and a prediction device as described in the second aspect above, wherein the prediction device is used to predict the open circuit voltage of the battery.

[0013] The beneficial effects of the present invention are as follows:

[0014] The embodiment of the present invention provides a method, device and battery pack for predicting the open circuit voltage of a battery. The open circuit voltage of the battery is predicted when the absolute value of the current of the battery in the battery pack is not greater than the threshold current, that is, the open circuit voltage is predicted when the current of the battery is small, which can help improve the accuracy of the predicted open circuit voltage. In addition, the voltage of the battery is collected according to a preset collection period, the first difference between any two adjacent voltages is calculated, and the prediction coefficient is determined according to each first difference. Then, the open circuit voltage of the battery is predicted according to the prediction coefficient and the prediction formula. In this way, the open circuit voltage of the battery at any time in the future can be predicted, and the battery can be prevented from being stationary for a long time when predicting the open circuit voltage, so that the open circuit voltage can be obtained in a shorter time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart of a method for predicting an open circuit voltage of a battery provided in an embodiment of the present invention;

[0016] Figure 2 A comparison diagram of an actually measured open circuit voltage and a predicted open circuit voltage provided in an embodiment of the present invention;

[0017] Figure 3 A flowchart of Example 1 provided in an embodiment of the present invention;

[0018] Figure 4 A schematic diagram of the structure of a device for predicting the open circuit voltage of a battery provided in an embodiment of the present invention;

[0019] Figure 5 A schematic diagram of the structure of a battery pack provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the accompanying drawings to describe in detail a specific implementation of a method for predicting the open circuit voltage of a battery, a prediction device, and a battery pack provided by an embodiment of the present invention. It should be noted that 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 making creative work are within the scope of protection of the present invention.

[0021] The embodiment of the present invention provides a method for predicting the open circuit voltage of a battery. Figure 1 As shown, it may include:

[0022] When the absolute value of the current of the battery in the battery pack is not greater than the threshold current, the battery can be considered to be in a pseudo-static state, and then the open circuit voltage prediction can be started. Therefore, the following process can be performed:

[0023] S101, collecting the voltage of the battery according to a preset collection cycle;

[0024] In some embodiments, collecting the voltage of the battery according to a preset collection cycle may include: collecting the voltage of the battery at a preset initial moment, and collecting the voltage of the battery according to a preset collection cycle starting from the preset initial moment. In this way, the timing can be started from the preset initial moment, and the voltage of the battery can be collected once every preset collection cycle, so that multiple voltages of the battery can be collected.

[0025] The preset collection period can be, but is not limited to, set to 60s to 900s, and the number of collection times n can be set, for example, but not limited to setting the value of n to 3 to 10, so that the battery voltage is collected once every preset collection period, and collected n times, plus the voltage collected at the preset initial moment, a total of n+1 voltages can be collected.

[0026] Moreover, when the preset collection period is set to a small value, the voltages of multiple batteries can be collected in a short time without a long time. Therefore, even if the pseudo-static state does not last very long, more voltages can still be obtained, thereby realizing the prediction of the open circuit voltage and avoiding the battery from being stationary for a long time.

[0027] In addition, the method for determining the preset initial moment may include: determining the preset initial moment according to the sum of the moment when the absolute value of the battery current is determined to be not greater than the threshold current and the preset time. The preset time may be, but is not limited to, set to 1s to 60s. For example, the moment when the absolute value of the battery current is determined to be not greater than the threshold current is t0, and the preset time is t1, then the preset initial moment is t0+t1.

[0028] In some embodiments, the collected battery voltage may be but is not limited to: when a battery pack includes multiple batteries, the voltage of each battery may be collected each time, and then the maximum value, minimum value, middle value or average value may be selected from these voltages as the battery voltage during this collection.

[0029] In some embodiments, after each voltage is collected, the collected voltage may be filtered to remove noise in the collected voltage and improve the signal-to-noise ratio, thereby improving the accuracy of the predicted open circuit voltage and reducing the calculation error caused by noise. The filtering method may be any method known to those skilled in the art that can achieve the filtering function, such as but not limited to the sliding average filtering method, which is not limited here.

[0030] S102, sorting the collected voltages according to the order of collection time, and calculating the first difference between any two adjacent voltages;

[0031] S103, determining a prediction coefficient according to each first difference;

[0032] In some embodiments, the implementation method of S103 may include: determining whether each first difference meets the prediction condition; if so, determining the prediction coefficient according to the average value corresponding to the reciprocal of each first difference; if not, determining the prediction coefficient to be zero.

[0033] That is to say, when each first difference meets the prediction condition, it means that the depolarization trend of the battery is obvious. At this time, the prediction coefficient can be determined according to the average value corresponding to the reciprocal of each first difference to take the depolarization of the battery into consideration. When each first difference does not meet the prediction condition, it means that the depolarization trend of the battery is not obvious. At this time, the prediction coefficient can be directly determined as zero to exclude the depolarization of the battery, so that the predicted open circuit voltage is more in line with the actual situation of the battery, and the accuracy of the prediction result is improved.

[0034] Among them, the prediction condition may include: each first difference is not zero, and the absolute value of the sum of each first difference is not less than a preset voltage. The preset voltage may be, but is not limited to, 2mV, 3mV, or 4mV, etc., and may be set according to actual conditions. Of course, the prediction condition is not limited to this, and may also include that each first difference is within a preset range, as long as each first difference can reflect the depolarization of the battery.

[0035] Furthermore, determining the prediction coefficient according to the average value corresponding to the reciprocals of the first differences includes: when the prediction coefficient includes the first coefficient and the second coefficient, recording the reciprocals of the first differences as the first reciprocals, calculating the second difference between any two adjacent first reciprocals, and then calculating the first average value corresponding to the second differences, and determining the first average value as the first coefficient (i.e., F mentioned in the subsequent content). 1 ); Calculate the second average value corresponding to each first reciprocal, and determine the second average value as the second coefficient (i.e., F mentioned in the subsequent content 2 ).

[0036] For example, starting from the preset initial time, after n preset acquisition cycles, a total of n+1 voltages can be acquired. After these n+1 voltages are sorted according to the acquisition time, the first differences are calculated, which can be expressed as: △U 0 =U 1 -U 0 , △U 1 =U 2 -U 1 , △U 2 =U3 -U 2 ,……,△U n-1 =U n -U n-1 , where these first differences are still arranged in chronological order. At this time, the first coefficient F 1 The calculation formula can be: 1 =[(1 / △U 1 )-(1 / △U 0 )+(1 / △U 2 )-(1 / △U 1 )+…+(1 / △U n-1 )-(1 / △U n-2 )] / (n-1), where F 1 represents the first coefficient, (1 / △U n-1 )-(1 / △U n-2 ) represents the second difference between two adjacent first inverses. The second coefficient F 2 The calculation formula can be: 2 =[(1 / △U 0 )+(1 / △U 1 )+…+(1 / △U n-1 )] / n,F 2 represents the second coefficient.

[0037] S104. Predicting the open circuit voltage of the battery at a first moment in the future according to the prediction coefficient and the prediction formula; wherein the prediction formula is used to describe the relationship between the first moment, the prediction coefficient, the preset collection cycle, the voltage collected in the last preset collection cycle, and the moment of the last preset collection cycle.

[0038] In some embodiments, predicting the open circuit voltage of the battery at a first moment in the future according to the prediction coefficient and the prediction formula includes:

[0039] The following formula is used to predict the open circuit voltage of the battery at the first moment in the future:

[0040] Formula 1: (1 / △W x )=k×F 1 ×(t x -t n ) / T+F 2 , x is a positive integer;

[0041] Formula 2: OCV x =U n +△W 1 +△W 2 +…+△W x ;

[0042] Among them, tx represents the first moment, OCV represents the predicted battery x The open circuit voltage at the moment, T represents the preset acquisition period, t n Indicates the time of the last preset collection cycle, U n represents the voltage collected in the last preset collection cycle, k is a constant, and when the prediction coefficient includes the first coefficient and the second coefficient, F 1 represents the first coefficient, F 2 In addition, the open circuit voltage and the prediction coefficient in Formula 1 and Formula 2 are in a nonlinear relationship.

[0043] Of course, in actual situations, the prediction formula is not limited to the above-mentioned Formula 1 and Formula 2, but can also be other forms used to describe the relationship between the first moment, the prediction coefficient, the preset acquisition cycle, the voltage collected in the last preset acquisition cycle, and the moment of the last preset acquisition cycle, such as but not limited to adding or deleting items on the basis of Formula 1 and Formula 2. It can be adjusted according to actual needs and is not limited here.

[0044] In this way, the open circuit voltage of the battery is predicted when the absolute value of the current of the battery in the battery pack is not greater than the threshold current, that is, the open circuit voltage is predicted when the current of the battery is small, which can help improve the accuracy of the predicted open circuit voltage. In addition, the voltage of the battery is collected according to the preset collection period, the first difference between any two adjacent voltages is calculated, and the prediction coefficient is determined according to each first difference. Then, the open circuit voltage of the battery is predicted according to the prediction coefficient and the prediction formula. Since the first moment in the future is not limited to a specific moment, the first moment in the future can be any moment in the future. In this way, the open circuit voltage of the battery at any moment in the future can be predicted, and the battery can be prevented from being stationary for a long time when predicting the open circuit voltage, and the open circuit voltage can be obtained in a shorter time.

[0045] For example, Figure 2 As shown in the figure, it is a comparison diagram of the actually measured open circuit voltage and the predicted open circuit voltage, wherein solid line 1 represents the actually measured open circuit voltage, solid line 2 represents the predicted open circuit voltage, and solid line 3 represents the error between the actually measured open circuit voltage and the predicted open circuit voltage. By comparison, it is found that the two lines have a high degree of overlap, indicating that the predicted open circuit voltage is closer to the actual open circuit voltage, and the error is smaller and more stable, which means that the prediction result has a high accuracy.

[0046] In some embodiments, when determining that the absolute value of the current of the battery in the battery pack is not greater than the threshold current, the following method may be used:

[0047] Method 1: According to the preset judgment cycle, determine whether the absolute value of the battery current is not greater than the threshold current. The preset judgment cycle can be set longer or shorter according to the actual situation, and it is not strictly required here. Based on this, before executing each step from S101 to S103, it can be determined whether the preset judgment cycle has been reached. If the preset judgment cycle has been reached, it is determined whether the absolute value of the battery current is not greater than the threshold current. If so, the above prediction process can be continued. If not, the above prediction process is stopped; if the preset judgment cycle has not been reached, the above prediction process can be continued. Thereby, it can be ensured that during the prediction process of the open circuit voltage, the current of the battery is always small, so that the battery is always in a pseudo-static state, which can improve the accuracy of the prediction result of the open circuit voltage and reduce the prediction error.

[0048] Method 2: From the beginning of charging and discharging of the battery pack, determine whether the absolute value of the battery current is not greater than the threshold current at regular intervals until the judgment result is yes, then stop judging, and execute S101 to S103 to predict the open circuit voltage of the battery until the prediction is completed. This can reduce the number of judgments and improve the prediction efficiency of the open circuit voltage. When the pseudo-static state of the battery lasts for a long time, this method can also make the prediction result have a higher accuracy.

[0049] Wherein, no matter in the above-mentioned method 1 or method 2, the threshold current can be but not limited to be set to 0 to 0.05C, where C represents the rated capacity of the battery.

[0050] The open circuit voltage prediction process is described below in conjunction with specific embodiments.

[0051] Embodiment 1: Combination Figure 3 As shown, the specific process may include:

[0052] S301, determine whether the absolute value of the battery current is not greater than the threshold current; if so, execute S302; if not, continue to execute this step;

[0053] S302, collecting the voltage of the battery at a preset initial moment, and collecting the voltage of the battery starting from the preset initial moment according to a preset collection cycle; filtering the voltage each time a voltage is collected;

[0054] S303, sorting the collected voltages according to the order of collection time, and calculating the first difference between any two adjacent voltages;

[0055] S304, determining whether each first difference value meets the prediction condition; if so, executing S305; if not, executing S306;

[0056] S305, record the reciprocal of each first difference as the first reciprocal, calculate the second difference between any two adjacent first reciprocals, calculate the first average value corresponding to each second difference, and determine the first average value as the first coefficient; and calculate the second average value corresponding to each first reciprocal, and determine the second average value as the second coefficient; execute S307;

[0057] S306, determining that the first coefficient and the second coefficient are both zero;

[0058] S307: predict the open circuit voltage of the battery at a certain moment in the future according to the prediction coefficient and the prediction formula.

[0059] Embodiment 2: The implementation process of Embodiment 2 is basically similar to that of Embodiment 1, except that: before executing each step (such as step i, where i is any one of S302 to S307), it is first determined whether the preset judgment cycle has been reached. If the preset judgment cycle has been reached and it is determined that the absolute value of the battery current is not greater than the threshold current, or if the preset judgment cycle has not been reached, step i is continued to be executed; if the preset judgment cycle has been reached and it is determined that the absolute value of the battery current is greater than the threshold current, step i is stopped.

[0060] Based on the same inventive concept, an embodiment of the present invention further provides a prediction device for the open circuit voltage of a battery. The implementation principle of the prediction device is similar to that of the aforementioned prediction method. The specific implementation method of the prediction device can refer to the specific embodiment of the aforementioned prediction method, and the repeated parts will not be repeated.

[0061] Specifically, an embodiment of the present invention provides a device for predicting the open circuit voltage of a battery, such as Figure 4 As shown, it may include:

[0062] Memory 401, used for storing program instructions;

[0063] The processor 402 is used to call the program instructions stored in the memory 401 and execute the prediction method introduced in the above content according to the obtained program.

[0064] In some embodiments, the prediction device may be a battery management system, or the prediction device may be a module in the battery management system, and the module may be an existing module in the battery management system and reused as the prediction device, or the module may be a newly added module in the battery management system.

[0065] Based on the same inventive concept, an embodiment of the present invention further provides a battery pack, such as Figure 5 As shown, it may include a battery 501 and a prediction device 502 as described above, and the prediction device 502 is used to predict the open circuit voltage of the battery 501 .

[0066] In some embodiments, the battery pack may further include a box, the battery is located in the box, and the prediction device may be located in the box or outside the box, which may be specifically configured according to actual conditions. In addition, the battery pack may further include other structures for realizing the functions of the battery pack, which may be specifically designed according to actual conditions and are not limited here.

[0067] Based on the same inventive concept, an embodiment of the present invention further provides a method for correcting the state of charge, which may include:

[0068] The open circuit voltage of the battery is predicted using the prediction method described above;

[0069] The estimated state of charge is corrected using the predicted open circuit voltage.

[0070] The method for estimating the state of charge may include, but is not limited to, the ampere-hour integration method, and the specific estimation process may be an estimation process well known to those skilled in the art, which will not be described in detail. The specific correction method may be a correction process well known to those skilled in the art, which will not be described in detail.

[0071] In this way, when the state of charge is corrected using the open circuit voltage predicted by the above method, the corrected state of charge is also more accurate based on the more accurate prediction result of the open circuit voltage, thereby improving the accuracy of the finally determined state of charge.

[0072] Based on the same inventive concept, an embodiment of the present invention also provides a method for estimating SOH (full name in English: State of Health, Chinese meaning: battery health state), which may include: predicting the open circuit voltage of the battery using the prediction method introduced in the above content; correcting the estimated SOC using the predicted open circuit voltage; and estimating SOH using the corrected SOC. In this way, the estimated SOH can also have a high accuracy.

[0073] The specific process of estimating SOH may be an estimation process well known to those skilled in the art, and will not be described in detail.

[0074] Of course, in the embodiment of the present invention, the predicted open circuit voltage can be used not only to correct the state of charge and estimate the SOH, but also to obtain the imbalance of each battery in the battery pack and estimate the remaining time of battery balancing, thereby increasing the update frequency of the balancing information and realizing the balancing processing of each battery, thereby improving the performance of the battery pack.

[0075] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for predicting battery open circuit voltage, It is characterized in that include: When the absolute value of the current of the battery in the battery pack is not greater than the threshold current, the following process is performed: Collecting the voltage of the battery according to a preset collection period, sorting the collected voltages according to the order of collection time, and calculating a first difference between any two adjacent voltages; determining a prediction coefficient according to each of the first differences; Predicting the open circuit voltage of the battery at a first moment in the future according to the prediction coefficient and the prediction formula; The prediction formula is used to describe the relationship between the first moment, the prediction coefficient, the preset acquisition cycle, the voltage collected in the last preset acquisition cycle, and the moment of the last preset acquisition cycle; Predicting the open circuit voltage of the battery at a first moment in the future according to the prediction coefficient and the prediction formula includes: The open circuit voltage of the battery at the first moment in the future is predicted using the following formula: (1 / △W x )=k×F 1 ×(t x -t n ) / T+F 2 , x is a positive integer; CVC x =U n +△W 1 +△W 2 +…+△W x ; Among them, t x represents the first moment, the first moment is any collection moment after the last moment of the preset collection cycle, OCV represents the predicted value of the battery at t x The open circuit voltage at the moment, T represents the preset acquisition period, t n Indicates the time of the last preset collection cycle, U n represents the voltage collected in the last preset collection cycle, k is a constant, and when the prediction coefficient includes the first coefficient and the second coefficient, F 1 represents the first coefficient, F 2 represents the second coefficient.

2. The prediction method according to claim 1, It is characterized in that Determining a prediction coefficient according to each of the first differences comprises: Determining whether each of the first differences meets a prediction condition; If yes, determining the prediction coefficient according to the average value corresponding to the reciprocals of the first differences; If not, the prediction coefficient is determined to be zero.

3. The prediction method according to claim 2, It is characterized in that The prediction condition includes: each of the first differences is not zero, and the absolute value of the sum of the first differences is not less than a preset voltage.

4. The prediction method according to claim 2, It is characterized in that Determining the prediction coefficient according to an average value corresponding to the reciprocals of the first differences comprises: When the prediction coefficient includes a first coefficient and a second coefficient, the reciprocal of each of the first differences is recorded as the first reciprocal, a second difference between any two adjacent first reciprocals is calculated, a first average value corresponding to each of the second differences is calculated, and the first average value is determined as the first coefficient; A second average value corresponding to each of the first reciprocals is calculated, and the second average value is determined as the second coefficient.

5. The prediction method according to claim 1, It is characterized in that The voltage of the battery is collected according to a preset collection period, including: The voltage of the battery at a preset initial moment is collected, and starting from the preset initial moment, the voltage of the battery is collected according to a preset collection cycle.

6. The prediction method according to claim 5, It is characterized in that The method for determining the preset initial time includes: The preset initial time is determined according to the sum of the time when the absolute value of the current of the battery is determined to be not greater than the threshold current and the preset time.

7. The prediction method according to any one of claims 1 to 6, It is characterized in that Also includes: After any voltage of the battery is collected, filtering is performed on the collected voltage.

8. A device for predicting battery open circuit voltage, It is characterized in that include: A memory for storing program instructions; A processor is used to call the program instructions stored in the memory and execute the prediction method according to any one of claims 1 to 7 according to the obtained program.

9. A battery pack, It is characterized in that include: A battery and a prediction device as claimed in claim 8, wherein the prediction device is used to predict the open circuit voltage of the battery.

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