A method and device for calibrating an open-circuit voltage curve of a lithium battery, and an electronic device

Abstract

The application provides a lithium battery open-circuit voltage curve calibration method, device and electronic equipment. The method comprises the following steps: intermittently charging or discharging a lithium battery by using an asymmetric sine wave current; acquiring a first battery terminal voltage and a total charging capacity during intermittent charging or a second battery terminal voltage and a total discharging capacity during intermittent discharging; and determining an open-circuit voltage curve of the lithium battery according to the first battery terminal voltage and the total charging capacity or according to the second battery terminal voltage and the total discharging capacity. The asymmetric sine wave current is used to intermittently charge and discharge the lithium battery, so that the standing time of the open-circuit voltage curve calibration method can be shortened.

Description

Technical Field

[0001] This invention belongs to the field of power battery technology, and specifically relates to a method, apparatus and electronic equipment for calibrating the open-circuit voltage curve of a lithium battery. Background Technology

[0002] Lithium-ion battery systems exist in various application scenarios, such as hybrid electric vehicles, electric vehicles, and energy storage systems. All of these systems require a battery management system (BMS) to control the battery operation. A common feature of all battery application types is that the lithium-ion battery cells in the battery pack undergo various charge and discharge cycles. Therefore, determining the actual state of charge (SOC) of each cell and the battery pack is crucial. The open-circuit voltage-SOC curve is one of the most important parameters for SOC estimation; thus, obtaining an accurate open-circuit voltage curve (OCV-SOC curve) is a prerequisite for accurate estimation of the battery's SOC. However, conventional open-circuit voltage curve testing methods are time-consuming, especially during the intermittent charge and discharge of lithium-ion batteries, requiring a long resting time to ensure the accuracy of the open-circuit voltage. Summary of the Invention

[0003] The purpose of the embodiments in this specification is to provide a method, apparatus, and electronic device for calibrating the open-circuit voltage curve of a lithium battery.

[0004] To solve the above-mentioned technical problems, the embodiments of this application are implemented in the following ways:

[0005] In a first aspect, this application provides a method for calibrating the open-circuit voltage curve of a lithium battery, the method comprising:

[0006] Asymmetrical sinusoidal current is used to intermittently charge or discharge lithium batteries; the first battery terminal voltage and total charging capacity during intermittent charging or the second battery terminal voltage and total discharging capacity during intermittent discharging are obtained.

[0007] The open-circuit voltage curve of the lithium battery is determined based on the terminal voltage of the first battery and the total charging capacity, or based on the terminal voltage of the second battery and the total discharging capacity.

[0008] In one embodiment, the method further includes:

[0009] Determine the period of the asymmetrical sinusoidal current.

[0010] In one embodiment, if the battery equivalent circuit model is a third-order equivalent circuit model, determining the period of the asymmetric sinusoidal current includes:

[0011] The lithium battery was subjected to constant current discharge at room temperature. After the discharge lasted for a preset time, the lithium battery was left to stand. The discharge terminal voltage during the discharge process and the stand voltage during the stand process were continuously recorded.

[0012] The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage.

[0013] The period of the asymmetric sinusoidal current is determined based on the estimated time constant.

[0014] In one embodiment, the time constant of the third-order equivalent circuit model includes a first time constant, a second time constant, and a third time constant;

[0015] The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage, including:

[0016] The voltage change rate during the time interval from the first time point to the second time point in the discharge process is k.

[0017] When the voltage change rate is less than k / 2, record the current time as the third time point;

[0018] When the voltage change rate is less than k / 4, record the current time as the fourth time point.

[0019] When the voltage change rate is less than k / 8, record the current time as the fifth time point.

[0020] The first time constant is determined based on the second and third time points; the second time constant is determined based on the third and fourth time points; and the third time constant is determined based on the fourth and fifth time points.

[0021] In one embodiment, determining the period of the asymmetric sinusoidal current based on a predicted time constant includes:

[0022] The first half-wave period of the asymmetric sinusoidal current is determined based on the first and second time constants.

[0023] The second half-wave period of the asymmetric sinusoidal current is determined based on the second and third time constants.

[0024] In one embodiment, the method further includes:

[0025] Determine the amplitude of the asymmetrical sinusoidal current, where the amplitude of the second half-wave of the asymmetrical sinusoidal current is one-quarter of the amplitude of the first half-wave.

[0026] In one embodiment, when intermittently charging the lithium battery using an asymmetric sinusoidal current, obtaining the first battery terminal voltage and total charging capacity during intermittent charging includes:

[0027] Discharge the lithium battery to its preset total capacity and let it stand at room temperature;

[0028] The lithium battery is intermittently charged using an asymmetric sinusoidal current.

[0029] Entering the resting phase, obtain the first battery terminal voltage and the total charging capacity at the current moment when the resting phase ends;

[0030] Based on the terminal voltage of the first battery and the total charging capacity, determine the open-circuit voltage curve of the lithium battery, including:

[0031] If the total charging capacity is less than the preset total capacity, the lithium battery is intermittently charged using an asymmetrical sinusoidal current until the total charging capacity is greater than or equal to the preset total capacity. The first battery terminal voltage and the total charging capacity at each time point are then curve-fitted to obtain the open-circuit voltage curve of the lithium battery.

[0032] In one embodiment, when using an asymmetric sinusoidal current to intermittently discharge the lithium battery, obtaining the second battery terminal voltage and total discharge capacity during intermittent discharge includes:

[0033] Fully charge the lithium battery at room temperature and let it stand.

[0034] Asymmetrical sinusoidal current is used to intermittently discharge the lithium battery;

[0035] Entering the resting phase, obtain the second battery terminal voltage and the total discharge capacity at the current moment when the resting phase ends;

[0036] Based on the second battery terminal voltage and total discharge capacity, determine the open-circuit voltage curve of the lithium battery, including:

[0037] If the total discharge capacity is less than the full charge capacity, continue to use an asymmetrical sinusoidal current to intermittently discharge the lithium battery until the total discharge capacity is greater than or equal to the full charge capacity. Then, perform curve fitting between the second battery terminal voltage and the total discharge capacity at each time point to obtain the open circuit voltage curve of the lithium battery.

[0038] Secondly, this application provides a lithium battery open-circuit voltage curve calibration device, the device comprising:

[0039] The acquisition module is used to intermittently charge or discharge the lithium battery using an asymmetric sinusoidal current; and to acquire the first battery terminal voltage and total charging capacity during intermittent charging or the second battery terminal voltage and total discharging capacity during intermittent discharging.

[0040] The curve determination module is used to determine the open-circuit voltage curve of the lithium battery based on the terminal voltage of the first battery and the total charging capacity, or based on the terminal voltage of the second battery and the total discharging capacity.

[0041] Thirdly, this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the lithium battery open-circuit voltage curve calibration method of the first aspect.

[0042] As can be seen from the technical solutions provided in the embodiments of this specification above, this solution employs an asymmetric sinusoidal current to intermittently charge and discharge the lithium battery. This suppresses the polarization reaction of the lithium battery and accelerates the decay rate of the lithium battery's polarization voltage, thereby effectively reducing the resting time required after each intermittent charge and discharge cycle. Simultaneously, due to the use of the asymmetric sinusoidal current, the anode or cathode of the lithium battery undergoes the corresponding redox reaction during each intermittent charge and discharge cycle, thus reducing the impact of internal battery temperature changes on the experimental results. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 A schematic flowchart illustrating the lithium battery open-circuit voltage curve calibration method provided in this application;

[0045] Figure 2 A schematic diagram of the asymmetrical sinusoidal current used in the intermittent discharge experiment provided in this application;

[0046] Figure 3 A schematic diagram of the asymmetrical sinusoidal current used in the intermittent charging experiment provided in this application;

[0047] Figure 4 The circuit diagram is for the third-order equivalent circuit model;

[0048] Figure 5 A schematic diagram of the terminal voltage during the constant current discharge process of the lithium battery provided in this application;

[0049] Figure 6 A flowchart illustrating the method for calibrating the open-circuit voltage curve of a lithium battery using an asymmetric sinusoidal current during intermittent discharge, as provided in this application.

[0050] Figure 7This is a schematic diagram of the lithium battery open-circuit voltage curve calibration device provided in this application.

[0051] Figure 8 A schematic diagram of the structure of the electronic device provided in this application. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0053] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0054] Various modifications and variations can be made to the specific embodiments described in this application without departing from the scope or spirit of this application, as will be apparent to those skilled in the art. Other embodiments derived from this application will be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0055] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0056] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0057] Reference Figure 1 This document illustrates a flowchart of the lithium battery open-circuit voltage curve calibration method applicable to the embodiments of this application. It is understood that this method can be applied to lithium batteries in various fields, such as digital devices, mobile phones, power banks, laptops, handling robots, automated guided vehicles, industrial drones, power tools, electric vehicles, electric forklifts, electric motorcycles, electric bicycles, electric toys, medical devices, uninterruptible power supplies, new energy battery storage systems, security equipment, surveying and mapping equipment, and portable devices.

[0058] like Figure 1As shown, the method for calibrating the open-circuit voltage curve of a lithium battery may include:

[0059] S110. Use an asymmetrical sinusoidal current to intermittently charge or discharge the lithium battery; obtain the first battery terminal voltage and total charging capacity during intermittent charging or the second battery terminal voltage and total discharging capacity during intermittent discharging.

[0060] S120. Determine the open-circuit voltage curve of the lithium battery based on the terminal voltage of the first battery and the total charging capacity, or based on the terminal voltage of the second battery and the total discharging capacity.

[0061] Specifically, an asymmetric sine wave refers to a sine wave in which the first and second half-waves have different periods, different amplitudes, or different periods and different amplitudes. Among them, different periods can be caused by the two parts of the rising and falling waves having different shapes or different durations, or different shapes and different durations.

[0062] Intermittent charging of lithium batteries refers to charging the battery for a period of time, then stopping charging to allow it to discharge to a certain level, and then recharging. Intermittent discharging of lithium batteries refers to discharging the battery to a certain level, stopping discharging, and then recharging.

[0063] The first or second battery terminal voltage during intermittent charging or discharging of a lithium battery can be obtained through an equivalent circuit model of the lithium battery.

[0064] The total charging or discharging capacity of a lithium battery during intermittent charging or discharging can be obtained by automatically sampling and statistically analyzing the current using experimental calibration instruments, or by calculation; no limitation is imposed here. For example, the total discharging capacity can be obtained by integrating the asymmetrical sinusoidal current of each discharge to obtain the discharge amount of each intermittent discharge. The total discharge capacity can then be obtained by summing the discharge amounts of each intermittent discharge.

[0065] To reduce the settling time in conventional open-circuit voltage curve testing, this embodiment uses an asymmetrical sinusoidal current instead of a square wave current to intermittently discharge and charge the lithium battery. Figure 2 and Figure 3 These are schematic diagrams of the asymmetrical sinusoidal current used in the intermittent discharge experiment and the intermittent charging experiment, respectively. Figure 2 and Figure 3 It is known that the asymmetrical sinusoidal current causes the lithium battery to undergo a short charging or discharging time during each intermittent discharge or charging process. This causes the polarization voltage of the lithium battery to decay rapidly during each intermittent discharge or charging process, thereby shortening the resting time after each intermittent discharge or charging.

[0066] The lithium battery open-circuit voltage curve calibration method provided in this embodiment uses an asymmetrical sinusoidal current. Since the asymmetrical sinusoidal current has fewer harmonics than the traditional square wave current, the polarization reaction generated during charging and discharging of the lithium battery is weaker, thus suppressing the polarization reaction. Furthermore, each discharge is immediately followed by a period of charging, which allows the two polarization reactions during discharging and charging to be partially canceled out, thereby accelerating the decay rate of the lithium battery polarization voltage and shortening the resting time after each intermittent discharge or charging. In addition, due to the use of the asymmetrical sinusoidal current, the anode or cathode of the lithium battery undergoes the corresponding redox reaction during each intermittent discharge or charging process, which helps to reduce the impact of internal temperature changes in the lithium battery on the experimental results during testing.

[0067] To further reduce the polarization reaction of lithium batteries during each intermittent discharge or intermittent charging process, the lithium battery open-circuit voltage curve calibration method provided in this application embodiment further includes:

[0068] Determine the period of the asymmetrical sinusoidal current.

[0069] Understandably, the period of the asymmetric sinusoidal current differs for different battery equivalent circuit models. For models higher than the three-stage equivalent circuit model, the period of the asymmetric sinusoidal current is relatively complex. The period of the asymmetric sinusoidal current in the first-order equivalent circuit model is R1*C1, where R1 is the polarization resistance of the lithium battery and C1 is the polarization capacitance. The period of the asymmetric sinusoidal current in the second-order equivalent circuit model is (R1*C1+R2*C2) / 2, where R1 and R2 are both polarization resistances of the lithium battery, and C1 and C2 are both polarization capacitances.

[0070] In one embodiment of this application, if the battery equivalent circuit model is a third-order equivalent circuit model, determining the period of the asymmetric sinusoidal current may include:

[0071] The lithium battery was subjected to constant current discharge at room temperature. After the discharge lasted for a preset time, the lithium battery was left to stand. The discharge terminal voltage during the discharge process and the stand voltage during the stand process were continuously recorded.

[0072] The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage.

[0073] The period of the asymmetric sinusoidal current is determined based on the estimated time constant.

[0074] Based on the above embodiments, the time constant of the third-order equivalent circuit model includes a first time constant, a second time constant, and a third time constant;

[0075] The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage, including:

[0076] The voltage change rate during the time interval from the first time point to the second time point in the discharge process is k.

[0077] When the voltage change rate is less than k / 2, record the current time as the third time point;

[0078] When the voltage change rate is less than k / 4, record the current time as the fourth time point.

[0079] When the voltage change rate is less than k / 8, record the current time as the fifth time point.

[0080] The first time constant is determined based on the second and third time points; the second time constant is determined based on the third and fourth time points; and the third time constant is determined based on the fourth and fifth time points.

[0081] Specifically, the circuit diagram of the third-order equivalent circuit model is as follows: Figure 4 As shown in the figure, Voc(SOC) represents the open-circuit voltage curve of the lithium battery, SOC represents the current remaining state of charge of the lithium battery, R0 represents the ohmic internal resistance of the lithium battery, V1, V2, and V3 represent the polarization voltage of the lithium battery at different time constants, R1, R2, and R3 represent the polarization resistance of the lithium battery at different time constants, C1, C2, and C3 represent the polarization capacitance of the lithium battery at different time constants, V represents the terminal voltage of the lithium battery, and I represents the output current of the lithium battery. The product of R1 and C1 is the first time constant T1, the product of R2 and C2 is the second time constant T2, and the product of R3 and C3 is the third time constant T3.

[0082] like Figure 5 The diagram shows the terminal voltage during the constant current discharge process of a lithium battery. The time from 0 to t0 and after t4 represents the resting time of the lithium battery, while t0 to t4 represents the discharge time. The preset duration of discharge is determined by the duration of change in the terminal voltage of the lithium battery; specifically, the preset duration is the time from when the terminal voltage begins to change until it stops changing.

[0083] The voltage change rate is taken as k during the period from the first time point t0 to the second time point t1 during the discharge process. After the lithium battery finishes discharging and enters a resting state, the three time constants T1, T2, and T3 of the lithium battery equivalent circuit model are estimated by continuously monitoring the voltage change rate at the lithium battery terminals. That is, when the voltage change rate after resting is less than k / 2, the current time is recorded as the third time point t2; when the voltage change rate is less than k / 4, the current time is recorded as the fourth time point t3; when the voltage change rate is less than k / 8, the current time is recorded as the fifth time point t4. The first time constant T1 is determined based on the second time point t1 and the third time point t2; the second time constant T2 is determined based on the third time point t2 and the fourth time point t3; and the third time constant T3 is determined based on the fourth time point t3 and the fifth time point t4. For example, the first time constant T1 = t2 - t1, the second time constant T2 = t3 - t2, and the third time constant T3 = t4 - t3.

[0084] In one embodiment of this application, determining the period of the asymmetric sinusoidal current based on a predicted time constant may include:

[0085] The first half-wave period of the asymmetric sinusoidal current is determined based on the first and second time constants.

[0086] The second half-wave period of the asymmetric sinusoidal current is determined based on the second and third time constants.

[0087] Specifically, the first half-wave period of the asymmetrical sinusoidal current can be (T1+T2)÷4, and the second half-wave period of the asymmetrical sinusoidal current is (T2+T3)÷4.

[0088] By using the period of the asymmetric sinusoidal current predicted by three time constants, the polarization reaction of the lithium battery during each intermittent discharge or intermittent charge process can be further reduced, thereby reducing the amplitude of the polarization voltage that decays during the resting period.

[0089] In one embodiment of this application, the lithium battery open-circuit voltage curve calibration method further includes:

[0090] Determine the amplitude of the asymmetrical sinusoidal current, where the amplitude of the second half-wave of the asymmetrical sinusoidal current is one-quarter of the amplitude of the first half-wave.

[0091] In this embodiment, the second half-wave amplitude of the asymmetric sinusoidal current is set to one-quarter of the first half-wave amplitude, which can balance the time of each intermittent discharge or intermittent charge.

[0092] In one embodiment of this application, when using an asymmetric sinusoidal current to intermittently charge a lithium battery, obtaining the first battery terminal voltage and total charging capacity during intermittent charging includes:

[0093] Discharge the lithium battery to its preset total capacity and let it stand at room temperature;

[0094] The lithium battery is intermittently charged using an asymmetric sinusoidal current.

[0095] Entering the resting phase, obtain the first battery terminal voltage and the total charging capacity at the current moment when the resting phase ends;

[0096] Based on the terminal voltage of the first battery and the total charging capacity, determine the open-circuit voltage curve of the lithium battery, including:

[0097] If the total charging capacity is less than the preset total capacity, the lithium battery is intermittently charged using an asymmetrical sinusoidal current until the total charging capacity is greater than or equal to the preset total capacity. The first battery terminal voltage and the total charging capacity at each time point are then curve-fitted to obtain the open-circuit voltage curve of the lithium battery.

[0098] In one embodiment of this application, such as Figure 6 As shown, when an asymmetrical sinusoidal current is used to intermittently discharge a lithium battery, the second battery terminal voltage and total discharge capacity during intermittent discharge are obtained, including:

[0099] Fully charge the lithium battery at room temperature and let it stand.

[0100] Asymmetrical sinusoidal current is used to intermittently discharge the lithium battery;

[0101] Entering the resting phase, obtain the second battery terminal voltage and the total discharge capacity at the current moment when the resting phase ends;

[0102] Based on the second battery terminal voltage and total discharge capacity, determine the open-circuit voltage curve of the lithium battery, including:

[0103] If the total discharge capacity is less than the full charge capacity, continue to use an asymmetrical sinusoidal current to intermittently discharge the lithium battery until the total discharge capacity is greater than or equal to the full charge capacity. Then, perform curve fitting between the second battery terminal voltage and the total discharge capacity at each time point to obtain the open circuit voltage curve of the lithium battery.

[0104] Compared with the conventional open-circuit voltage curve test scheme, this embodiment uses an asymmetrical sinusoidal current to intermittently discharge the lithium battery, thereby reducing the resting time after each intermittent discharge and improving experimental efficiency.

[0105] Example

[0106] Taking the intermittent discharge of a lithium battery using an asymmetrical sinusoidal current as an example, the open-circuit voltage curve of the lithium battery is determined.

[0107] Step 1) Perform constant current discharge on the lithium battery at room temperature;

[0108] Step 2) After discharging for a preset time, let the lithium battery stand still, and continuously record the discharge terminal voltage during the discharge process and the resting terminal voltage during the resting process.

[0109] Step 3) Estimate the time constant of the battery equivalent circuit model based on the recorded discharge terminal voltage and resting terminal voltage;

[0110] Step 4) Calculate the period of the asymmetrical sinusoidal current based on the estimated time constant;

[0111] Step 5) Fully charge the lithium battery at room temperature and let it stand.

[0112] Step 6) Intermittently discharge the lithium battery using an asymmetrical sinusoidal current;

[0113] Step 7) Enter the resting stage, and record the second battery terminal voltage and the total discharge capacity at the current moment when the resting period ends;

[0114] Step 8) Determine whether the total discharge capacity is greater than or equal to the full charge capacity. If the total discharge capacity is greater than or equal to the full charge capacity, proceed to step 9); if the total discharge capacity is less than the full charge capacity, proceed to step 6.

[0115] Step 9) Perform curve fitting on the recorded second battery terminal voltage and total discharge capacity at each time point to obtain the open-circuit voltage curve of the lithium battery.

[0116] Reference Figure 7 The diagram shows a schematic of a lithium battery open-circuit voltage curve calibration device according to an embodiment of this application.

[0117] like Figure 7 As shown, the lithium battery open-circuit voltage curve calibration device 700 may include:

[0118] The acquisition module 710 is used to intermittently charge or discharge the lithium battery using an asymmetric sinusoidal current; and to acquire the first battery terminal voltage and total charging capacity during intermittent charging or the second battery terminal voltage and total discharging capacity during intermittent discharging.

[0119] The curve determination module 720 is used to determine the open-circuit voltage curve of the lithium battery based on the first battery terminal voltage and total charging capacity or based on the second battery terminal voltage and total discharging capacity.

[0120] Optionally, the device may also include:

[0121] The period determination module is used to determine the period of an asymmetrical sinusoidal current.

[0122] Optionally, if the battery equivalent circuit model is a third-order equivalent circuit model, the period determination module is also used for:

[0123] The lithium battery was subjected to constant current discharge at room temperature. After the discharge lasted for a preset time, the lithium battery was left to stand. The discharge terminal voltage during the discharge process and the stand voltage during the stand process were continuously recorded.

[0124] The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage.

[0125] The period of the asymmetric sinusoidal current is determined based on the estimated time constant.

[0126] Optionally, the time constants of the third-order equivalent circuit model include a first time constant, a second time constant, and a third time constant;

[0127] The period determination module is also used for:

[0128] The voltage change rate during the time interval from the first time point to the second time point in the discharge process is k.

[0129] When the voltage change rate is less than k / 2, record the current time as the third time point;

[0130] When the voltage change rate is less than k / 4, record the current time as the fourth time point.

[0131] When the voltage change rate is less than k / 8, record the current time as the fifth time point.

[0132] The first time constant is determined based on the second and third time points; the second time constant is determined based on the third and fourth time points; and the third time constant is determined based on the fourth and fifth time points.

[0133] Optionally, the period determination module is also used for:

[0134] The first half-wave period of the asymmetric sinusoidal current is determined based on the first and second time constants.

[0135] The second half-wave period of the asymmetric sinusoidal current is determined based on the second and third time constants.

[0136] Optionally, the device may also include:

[0137] The amplitude determination module is used to determine the amplitude of the asymmetrical sinusoidal current, where the amplitude of the second half-wave of the asymmetrical sinusoidal current is one-quarter of the amplitude of the first half-wave.

[0138] Optionally, when intermittently charging the lithium battery using an asymmetrical sinusoidal current, the acquisition module 710 is also used for:

[0139] Discharge the lithium battery to its preset total capacity and let it stand at room temperature;

[0140] The lithium battery is intermittently charged using an asymmetric sinusoidal current.

[0141] Entering the resting phase, obtain the first battery terminal voltage and the total charging capacity at the current moment when the resting phase ends;

[0142] The curve determination module 720 is also used for:

[0143] If the total charging capacity is less than the preset total capacity, the lithium battery is intermittently charged using an asymmetrical sinusoidal current until the total charging capacity is greater than or equal to the preset total capacity. The first battery terminal voltage and the total charging capacity at each time point are then curve-fitted to obtain the open-circuit voltage curve of the lithium battery.

[0144] Optionally, when the lithium battery is intermittently discharged using an asymmetrical sinusoidal current, the acquisition module 710 is also used for:

[0145] Fully charge the lithium battery at room temperature and let it stand.

[0146] Asymmetrical sinusoidal current is used to intermittently discharge the lithium battery;

[0147] Entering the resting phase, obtain the second battery terminal voltage and the total discharge capacity at the current moment when the resting phase ends;

[0148] The curve determination module is also used for:

[0149] If the total discharge capacity is less than the full charge capacity, continue to use an asymmetrical sinusoidal current to intermittently discharge the lithium battery until the total discharge capacity is greater than or equal to the full charge capacity. Then, perform curve fitting between the second battery terminal voltage and the total discharge capacity at each time point to obtain the open circuit voltage curve of the lithium battery.

[0150] The lithium battery open-circuit voltage curve calibration device provided in this embodiment can perform the above-described method embodiment, and its implementation principle and technical effect are similar, so it will not be described again here.

[0151] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Figure 8 The diagram shows a structural schematic of an electronic device 800 suitable for implementing embodiments of this application.

[0152] like Figure 8As shown, the electronic device 800 includes a central processing unit (CPU) 801, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 802 or a program loaded from a storage section 808 into a random access memory (RAM) 803. The RAM 803 also stores various programs and data required for the operation of the device 800. The CPU 801, ROM 802, and RAM 803 are interconnected via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0153] The following components are connected to I / O interface 805: an input section 806 including a keyboard, mouse, etc.; an output section 807 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 808 including a hard disk, etc.; and a communication section 809 including a network interface card such as a LAN card, modem, etc. The communication section 809 performs communication processing via a network such as the Internet. A drive 810 is also connected to I / O interface 806 as needed. A removable medium 811, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on drive 810 as needed so that computer programs read from it can be installed into storage section 808 as needed.

[0154] In particular, according to embodiments of this disclosure, the above references Figure 1 The described process can be implemented as a computer software program. For example, embodiments of this disclosure include a computer program product comprising a computer program tangibly embodied on a machine-readable medium, the computer program containing program code for performing the above-described lithium battery open-circuit voltage curve calibration method. In such embodiments, the computer program can be downloaded and installed from a network via communication section 809, and / or installed from removable medium 811.

[0155] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0156] The units or modules described in the embodiments of this application can be implemented in software or hardware. The described units or modules can also be located in a processor. The names of these units or modules do not, in some cases, constitute a limitation on the unit or module itself.

[0157] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, a laptop computer, a mobile phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0158] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0159] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A method for calibrating the open-circuit voltage curve of a lithium battery, characterized in that, The method includes: Asymmetrical sinusoidal current is used to intermittently charge or discharge lithium batteries. The asymmetrical sinusoidal current refers to a sinusoidal current in which the first half-wave and the second half-wave have different periods, different amplitudes, or different periods and different amplitudes. Intermittent charging means that the lithium battery is charged for a period of time, then charging is stopped, allowing it to discharge to a certain extent, and then charging is started again. Intermittent discharging means that the lithium battery is discharged to a certain extent, then discharging is stopped, and then charging is started. Obtain the first battery terminal voltage and total charging capacity during intermittent charging, or the second battery terminal voltage and total discharging capacity during intermittent discharging; The open-circuit voltage curve of the lithium battery is determined based on the first battery terminal voltage and the total charging capacity, or based on the second battery terminal voltage and the total discharging capacity.

2. The method according to claim 1, characterized in that, The method further includes: Determine the period of the asymmetric sinusoidal current.

3. The method according to claim 2, characterized in that, If the battery equivalent circuit model is a third-order equivalent circuit model, determining the period of the asymmetric sinusoidal current includes: The lithium battery was subjected to constant current discharge at room temperature. After the discharge lasted for a preset time, the lithium battery was left to stand still, and the discharge terminal voltage during the discharge process and the stand-up terminal voltage during the stand-up process were continuously recorded. The time constant of the battery equivalent circuit model is estimated based on the discharge terminal voltage and the resting terminal voltage. The period of the asymmetric sinusoidal current is determined based on the estimated time constant.

4. The method according to claim 3, characterized in that, The time constants of the third-order equivalent circuit model include a first time constant, a second time constant, and a third time constant; The step of estimating the time constant of the battery equivalent circuit model based on the discharge terminal voltage and the resting terminal voltage includes: The voltage change rate k is taken as the time period from the first time point to the second time point during the discharge process, where the first time point is the starting time point of the lithium battery discharge time, and the second time point is the time point corresponding to the lowest terminal voltage change during the lithium battery discharge process. When the voltage change rate is less than k / 2, record the current time as the third time point; When the voltage change rate is less than k / 4, record the current time as the fourth time point. When the voltage change rate is less than k / 8, record the current time as the fifth time point. The first time constant is determined based on the second time point and the third time point; the second time constant is determined based on the third time point and the fourth time point; and the third time constant is determined based on the fourth time point and the fifth time point.

5. The method according to claim 4, characterized in that, Determining the period of the asymmetric sinusoidal current based on the estimated time constant includes: The first half-wave period of the asymmetric sinusoidal current is determined based on the first time constant and the second time constant. The second half-wave period of the asymmetric sinusoidal current is determined based on the second time constant and the third time constant.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: The amplitude of the asymmetric sinusoidal current is determined, wherein the amplitude of the second half-wave of the asymmetric sinusoidal current is one-quarter of the amplitude of the first half-wave.

7. The method according to any one of claims 1-5, characterized in that, When using the asymmetric sinusoidal current to intermittently charge the lithium battery, obtaining the first battery terminal voltage and total charging capacity during intermittent charging includes: The lithium battery is discharged to its preset total charge and left to stand at room temperature. The lithium battery is intermittently charged using the aforementioned asymmetric sinusoidal current. Entering the resting phase, obtain the first battery terminal voltage and the total charging capacity at the current moment when the resting phase ends; The step of determining the open-circuit voltage curve of the lithium battery based on the first battery terminal voltage and the total charging capacity includes: If the total charging capacity is less than the preset total capacity, the lithium battery is intermittently charged using the asymmetrical sinusoidal current until the total charging capacity is greater than or equal to the preset total capacity. The first battery terminal voltage and the total charging capacity at each time point are then curve-fitted to obtain the open-circuit voltage curve of the lithium battery.

8. The method according to any one of claims 1-5, characterized in that, When the lithium battery is intermittently discharged using the aforementioned asymmetrical sinusoidal current, obtaining the second battery terminal voltage and total discharge capacity during intermittent discharge includes: The lithium battery was fully charged at room temperature and then left to stand. The lithium battery is intermittently discharged using the aforementioned asymmetric sinusoidal current. Entering the resting phase, obtain the second battery terminal voltage and the total discharge capacity at the current moment when the resting phase ends; The step of determining the open-circuit voltage curve of the lithium battery based on the second battery terminal voltage and the total discharge capacity includes: If the total discharge capacity is less than the full charge capacity, the lithium battery is intermittently discharged using the asymmetrical sinusoidal current until the total discharge capacity is greater than or equal to the full charge capacity. The second battery terminal voltage and the total discharge capacity at each time point are then curve-fitted to obtain the open-circuit voltage curve of the lithium battery.

9. A lithium battery open-circuit voltage curve calibration device, characterized in that, The device includes: The acquisition module is used to intermittently charge or discharge the lithium battery using an asymmetrical sinusoidal current; to acquire the first battery terminal voltage and total charging capacity during intermittent charging or the second battery terminal voltage and total discharging capacity during intermittent discharging, wherein the asymmetrical sinusoidal current refers to a sinusoidal current with different periods, amplitudes, or periods and amplitudes of the first and second half-waves; intermittent charging refers to the lithium battery being charged for a period of time, then stopping charging, allowing it to discharge to a certain extent, and then charging again; intermittent discharging refers to the lithium battery being discharged to a certain extent, then stopping discharging, and then charging again; The curve determination module is used to determine the open-circuit voltage curve of the lithium battery based on the first battery terminal voltage and the total charging capacity or based on the second battery terminal voltage and the total discharging capacity.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the lithium battery open-circuit voltage curve calibration method as described in any one of claims 1-8.

Images