Battery SOC estimation method and apparatus with end correction

Abstract

Disclosed in the present application are a battery SOC estimation method and apparatus with end correction. The method comprises: step (1), when a battery pack does not operate and is in a standing state, acquiring an initial value SOC0 of a battery capacity according to an open-circuit voltage method; step (2), during operation of the battery pack, updating the SOC value of the battery pack in real time on the basis of preset correction factors that affect the battery capacity, the correction factors comprising a charging and discharging current correction factor, a temperature correction factor and a charging and discharging cycle count correction factor; step (3), when the battery pack stops operating, correcting the initial value SOC0 of the battery capacity according to the open-circuit voltage method and the SOC value before stopping of operation; and step (4), if the SOC value of the battery pack is greater than 90% or less than 10%, performing end correction on the SOC value. The present application can improve the accuracy and stability of battery SOC estimation.

Description

Battery SOC estimation method and device with terminal correction

[0001] This application claims priority to the Chinese patent application with application number 202311256358.6 and application name “Battery SOC estimation method and device with terminal correction” filed with the State Intellectual Property Office of China on September 26, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of energy storage battery power management, and in particular to a battery SOC estimation method and device with terminal correction, a storage medium, and a computer device. Background Art

[0003] To address the global energy crisis and reduce carbon emissions, many countries are optimizing the management and operation of energy storage systems to improve their performance and efficiency. Estimating the battery's state of charge (SOC) is particularly important in the household energy storage sector. Accurately estimating the SOC value allows for optimal charging and discharging strategies, better balancing energy supply and demand, and extending battery life. It also provides users with accurate information on available battery energy, allowing them to rationally manage energy usage based on their needs and improving the user experience.

[0004] The current mainstream SOC estimation methods on the market have low estimation accuracy and poor real-time performance.

[0005] Application Contents

[0006] The present application provides a battery SOC estimation method and device with terminal correction, a storage medium, and a computer device, which can improve the accuracy and stability of battery SOC estimation.

[0007] According to one aspect of the present application, a battery SOC estimation method with terminal correction is provided, comprising the following steps:

[0008] Step (1), when the battery pack is not in operation and is in a static state, obtaining an initial value SOC0 of the battery capacity according to an open circuit voltage method;

[0009] Step (2), during the operation of the battery pack, the SOC value of the battery pack is updated in real time based on preset correction factors affecting the battery capacity, the correction factors including a charge and discharge current correction factor, a temperature correction factor, and a charge and discharge cycle number correction factor;

[0010] Step (3), when the battery pack stops working, the initial value SOC0 of the battery capacity is corrected according to the open circuit voltage method and the SOC value before the battery pack stops working;

[0011] Step (4): If the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

[0012] Optionally, step (1) includes:

[0013] Obtaining a corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack determined by a curve fitting method;

[0014] Obtain the open circuit voltage of the battery pack according to the open circuit voltage method, and determine the initial value SOC0 of the battery capacity corresponding to the open circuit voltage of the battery pack based on the corresponding relationship diagram;

[0015] The corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack is drawn by the following steps:

[0016] Discharge the battery pack to the cut-off voltage in a constant current manner and leave it to stand until the battery pack is fully discharged;

[0017] Perform constant current charging on the fully discharged battery pack to 5% of the rated capacity, record the terminal voltage of the battery pack at this time and let it stand for a preset time;

[0018] Continue to charge the battery pack with constant current until it reaches 10% of the rated capacity, record the terminal voltage of the battery pack at this time, and let it stand for a preset time;

[0019] Continue to charge the battery pack at a constant current until the battery is fully charged, charging 5% of the rated capacity each time. After the battery is fully charged, a corresponding relationship diagram between the open circuit voltage and SOC of the battery pack is drawn by curve fitting.

[0020] Optionally, the method further includes:

[0021] When the battery pack has been stationary for more than a certain time, the initial value SOC0 of the battery capacity is obtained again according to the open circuit voltage method, and the initial value SOC0 is updated.

[0022] Optionally, the calculation formula for updating the SOC value in step (2) is:

[0023] Among them, SOC0 is the initial state of charge of the battery pack, C is the total capacity of the battery pack, η is the charge and discharge efficiency of the battery pack, i is the charge and discharge current, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

[0024] Optionally, the charge and discharge current correction factor in step (2) is determined according to a functional relationship between the charge and discharge current correction factor and the discharge current, wherein the functional relationship between the charge and discharge current correction factor and the discharge current is obtained by the following steps:

[0025] Charge the battery pack to full power at a room temperature of 25°C.

[0026] Discharge the fully charged battery pack at a constant current and record the battery discharge capacity at this time;

[0027] While ensuring that the temperature remains constant, change the discharge current to discharge the fully charged battery pack and record the battery discharge capacity at this time;

[0028] Repeat the above steps to obtain the relationship between the discharge current and the actual discharge amount. Based on the relationship between the discharge current and the actual discharge amount, curve fitting is performed through MATLAB to obtain the functional relationship between the discharge current correction factor and the discharge current.

[0029] Optionally, the temperature correction factor in step (2) is determined according to a functional relationship between the temperature and the temperature correction factor, wherein the functional relationship between the temperature and the temperature correction factor is obtained by the following steps:

[0030] Set the thermostat to -20°C, charge the battery pack to full charge, and then place it in the thermostat. Allow it to stand until the temperature of the battery pack is consistent with that of the thermostat. Discharge the battery completely at a standard rate of C / 3, and record the actual discharge capacity of the battery.

[0031] The temperature of the constant temperature box was adjusted to 0°C, 20°C, 25°C, 30°C, and 40°C, respectively, and the above steps were repeated. Based on the actual discharge capacity at different temperature values, the functional relationship between temperature and temperature correction factor was obtained using the MATLAB polynomial fitting algorithm.

[0032] Optionally, the charge-discharge cycle number correction factor in step (2) is determined based on a functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor, wherein the functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor is obtained by the following steps:

[0033] At a room temperature of 25°C, charge and discharge the battery pack at a charge and discharge current of 1C, and record the actual discharge capacity of the battery;

[0034] Let the battery rest and repeat the above steps for a preset number of times;

[0035] The relationship between the number of charge and discharge cycles and the discharge capacity is obtained by using a MATLAB polynomial fitting algorithm, and based on the relationship between the number of charge and discharge cycles and the discharge capacity, the functional relationship between the number of charge and discharge cycles and the charge and discharge cycle correction factor is determined.

[0036] Optionally, in step (3), correction is made based on the SOC value before standing still. When the SOC value before standing still is greater than 70%, the initial value SOC0 is corrected with the maximum cell voltage value. When the SOC is less than 40%, the initial value SOC0 is corrected with the minimum cell voltage value. In other cases, the initial value SOC0 is corrected with the average cell voltage value.

[0037] Optionally, step (4) includes:

[0038] Determine whether the SOC value of the battery pack is greater than 90% or less than 10%;

[0039] If it is greater than 90% or less than 10%, perform terminal correction and record the battery voltage U1 and current I x , and record the BMS closest to I at different magnifications x The currents of the two discharge curves are recorded as I1 and I2, where I1 x <I2;

[0040] Record the remaining power corresponding to I1 and I2 as SOC1 and SOC2 under the terminal voltage U1, and let:

[0041] From the above formula, we can deduce that the current I x Lower corrected SOC x ,in,

[0042] According to another aspect of the present application, a battery SOC estimation device with terminal correction is provided, wherein the device is configured to:

[0043] When the battery pack is not working and is in a static state, the initial value SOC0 of the battery capacity is obtained according to the open circuit voltage method;

[0044] During the operation of the battery pack, the SOC value of the battery pack is updated in real time based on the preset correction factors affecting the battery capacity. The correction factors include the charge and discharge current correction factor, the temperature correction factor, and the charge and discharge cycle number correction factor.

[0045] When the battery pack stops working, the initial value SOC0 of the battery capacity is corrected according to the open circuit voltage method and the SOC value before stopping working;

[0046] If the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

[0047] Optionally, the device is further used for:

[0048] Obtaining a corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack determined by a curve fitting method;

[0049] ​Obtain the open circuit voltage of the battery pack according to the open circuit voltage method, and determine the initial value SOC0 of the battery capacity corresponding to the open circuit voltage of the battery pack based on the corresponding relationship diagram;

[0050] The corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack is drawn by the following steps:

[0051] Discharge the battery pack to the cut-off voltage in a constant current manner and leave it to stand until the battery pack is fully discharged;

[0052] Perform constant current charging on the fully discharged battery pack to 5% of the rated capacity, record the terminal voltage of the battery pack at this time and let it stand for a preset time;

[0053] Continue to charge the battery pack with constant current until it reaches 10% of the rated capacity, record the terminal voltage of the battery pack at this time, and let it stand for a preset time;

[0054] Continue to charge the battery pack at a constant current until the battery is fully charged, charging 5% of the rated capacity each time. After the battery is fully charged, a corresponding relationship diagram between the open circuit voltage and SOC of the battery pack is drawn by curve fitting.

[0055] Optionally, the device is further used for:

[0056] When the battery pack has been stationary for more than a certain time, the initial value SOC0 of the battery capacity is obtained again according to the open circuit voltage method, and the initial value SOC0 is updated.

[0057] Optionally, the calculation formula for updating the SOC value is:

[0058] Among them, SOC0 is the initial state of charge of the battery pack, C is the total capacity of the battery pack, η is the charge and discharge efficiency of the battery pack, i is the charge and discharge current, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

[0059] Optionally, the charge and discharge current correction factor is determined according to a functional relationship between the charge and discharge current correction factor and the discharge current, wherein the functional relationship between the charge and discharge current correction factor and the discharge current is obtained by the following steps:

[0060] Charge the battery pack to full power at a room temperature of 25°C.

[0061] Discharge the fully charged battery pack at a constant current and record the battery discharge capacity at this time;

[0062] While ensuring that the temperature remains constant, change the discharge current to discharge the fully charged battery pack and record the battery discharge capacity at this time;

[0063] Repeat the above steps to obtain the relationship between the discharge current and the actual discharge amount. Based on the relationship between the discharge current and the actual discharge amount, curve fitting is performed through MATLAB to obtain the functional relationship between the discharge current correction factor and the discharge current.

[0064] Optionally, the temperature correction factor is determined according to a functional relationship between the temperature and the temperature correction factor, wherein the functional relationship between the temperature and the temperature correction factor is obtained by the following steps:

[0065] Set the thermostat to -20°C, charge the battery pack to full charge, and then place it in the thermostat. Allow it to stand until the temperature of the battery pack is consistent with that of the thermostat. Discharge the battery completely at a standard rate of C / 3, and record the actual discharge capacity of the battery.

[0066] The temperature of the constant temperature box was adjusted to 0°C, 20°C, 25°C, 30°C, and 40°C, respectively. The above steps were repeated. Based on the actual discharge capacity at different temperature values, the functional relationship between temperature and temperature correction factor was obtained using the MATLAB polynomial fitting algorithm.

[0067] Optionally, the charge-discharge cycle number correction factor is determined based on a functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor, wherein the functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor is obtained by the following steps:

[0068] At a room temperature of 25°C, charge and discharge the battery pack at a charge and discharge current of 1C, and record the actual discharge capacity of the battery;

[0069] Let the battery rest and repeat the above steps for a preset number of times;

[0070] The relationship between the number of charge and discharge cycles and the discharge capacity is obtained by using a MATLAB polynomial fitting algorithm, and based on the relationship between the number of charge and discharge cycles and the discharge capacity, the functional relationship between the number of charge and discharge cycles and the charge and discharge cycle correction factor is determined.

[0071] Optionally, the device is further used for:

[0072] Correction is made based on the SOC value before standing still. When the SOC value before standing still is greater than 70%, the initial value SOC0 is corrected with the maximum cell voltage value. When the SOC is less than 40%, the initial value SOC0 is corrected with the minimum cell voltage value. In other cases, the initial value SOC0 is corrected with the average cell voltage value.

[0073] Optionally, the device is further used for:

[0074] Determine whether the SOC value of the battery pack is greater than 90% or less than 10%;

[0075] If it is greater than 90% or less than 10%, perform terminal correction and record the battery voltage U1 and current I x , and record the BMS closest to I at different magnifications x The currents of the two discharge curves are recorded as I1 and I2, where I1 x <I2;

[0076] Record the remaining power corresponding to I1 and I2 as SOC1 and SOC2 under the terminal voltage U1, and let:

[0077] From the above formula, we can deduce that the current I x Lower corrected SOC x ,in,

[0078] According to another aspect of the present application, a storage medium is provided, on which a computer program is stored. When the program is executed by a processor, the battery SOC estimation method with terminal correction is implemented.

[0079] According to another aspect of the present application, a computer device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein the processor implements the above-mentioned battery SOC estimation method with terminal correction when executing the program.

[0080] By means of the above technical solution, the present application provides a battery SOC estimation method and device with terminal correction, a storage medium, and a computer device. The SOC of the battery pack is updated in real time by improving the ampere-hour integration method, the correction factor affecting the battery capacity is analyzed, and the calculation process of the correction factor is given. When the correction conditions are met, the SOC is corrected according to the voltage value of the battery cell. At the end of charging and discharging, the SOC is terminally corrected according to the charging and discharging conditions of the battery at different rates, thereby improving the accuracy and stability of the battery SOC estimation.

[0081] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work. ​

[0083] FIG1 is a flow chart showing a method for estimating battery SOC with terminal correction according to an embodiment of the present application;

[0084] FIG2 is a schematic diagram showing a relationship between a discharge current and an actual discharge amount provided by an embodiment of the present application;

[0085] FIG3 is a schematic diagram showing the relationship between temperature and discharge capacity provided by an embodiment of the present application;

[0086] FIG4 is a schematic diagram showing the relationship between the number of charge and discharge cycles and the discharge capacity provided by an embodiment of the present application;

[0087] FIG5 shows a schematic diagram of the device structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0088] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0089] The present application provides a battery SOC estimation method with terminal correction in this embodiment, as shown in FIG1 , the method comprising:

[0090] Step (1): When the battery pack is not in operation and is in a static state, an initial value SOC0 of the battery capacity is obtained according to an open circuit voltage method.

[0091] In the embodiment of the present application, since the battery's charge and discharge require periodic updating of SOC0, it is necessary to obtain the initial value SOC0 of the battery capacity according to the open circuit voltage method.

[0092] Optionally, step (1) includes obtaining a corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack determined by a curve fitting method; obtaining the open circuit voltage of the battery pack according to the open circuit voltage method, and determining the initial value SOC0 of the battery capacity corresponding to the open circuit voltage of the battery pack based on the corresponding relationship diagram; wherein the corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack is drawn by the following steps: discharging the battery pack to the cut-off voltage in a constant current manner, and standing until the battery pack is completely discharged; charging the completely discharged battery pack with a constant current to 5% of the rated capacity, recording the terminal voltage of the battery pack at this time and standing for a preset time; continuing to charge the battery pack with a constant current to 10% of the rated capacity, recording the terminal voltage of the battery pack at this time and standing for a preset time; continuing to charge the battery pack with a constant current until the battery is fully charged, charging 5% of the rated capacity each time, and drawing a corresponding relationship diagram between the open circuit voltage and the SOC of the battery pack by a curve fitting method after full charge.

[0093] Optionally, the method further includes: when the rest time of the battery pack exceeds a certain value, re-obtaining the initial value SOC0 of the battery capacity according to the open circuit voltage method, and updating the initial value SOC0.

[0094] In this embodiment, the specific calculation and update process of SOC0 includes the following steps: (1) First, discharge the battery pack to the cut-off voltage in a constant current manner and let it stand to ensure complete discharge. (2) Perform constant current charging on the completely discharged battery pack to 5% of the rated capacity. During the charging process, the output current accuracy must be ensured to be high. The terminal voltage of the battery pack at this time is recorded and the battery pack is left to stand for a period of time. (3) Continue to charge the battery pack with a constant current to 10% of the rated capacity. The terminal voltage of the battery pack at this time is recorded and the battery pack is left to stand for a period of time. (4) Repeat the above steps until the battery is fully charged, and then obtain the corresponding relationship diagram between the open circuit voltage and SOC of the battery cell by curve fitting. (5) Update SOC0 when the battery pack has been standing for more than a certain time.

[0095] Step (2) updates the SOC value of the battery pack in real time during the operation of the battery pack based on preset correction factors affecting the battery capacity, wherein the correction factors include a charge and discharge current correction factor, a temperature correction factor, and a charge and discharge cycle number correction factor.

[0096] In the embodiment of the present application, the SOC of the battery pack needs to be updated in real time based on the improved ampere-hour integration method. The correction factors required by the improved ampere-hour integration method include the charge and discharge current correction factor, the temperature correction factor, and the charge and discharge cycle number correction factor.

[0097] Optionally, the calculation formula for updating the SOC value in step (2) is:

[0098] Among them, SOC0 is the initial state of charge of the battery pack, C is the total capacity of the battery pack, η is the charge and discharge efficiency of the battery pack, i is the charge and discharge current, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

[0099] In this embodiment, the traditional ampere-hour integration method calculates the battery state of charge based on the integration of current and time during the battery pack charging and discharging process, that is:

[0100] Where SOC0 is the battery's initial state of charge, C is the battery's total capacity, η is the battery's charge and discharge efficiency, and i is the charge and discharge current. This method places high demands on the battery's rated capacity and the accuracy of the sampled current. Furthermore, the battery's discharge efficiency varies at different temperatures. Therefore, an improved ampere-hour integration method is proposed to estimate SOC. This improved ampere-hour integration method incorporates charge and discharge current correction factors, temperature correction factors, and charge and discharge cycle number correction factors, namely:

[0101] Among them, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

[0102] Optionally, the charge and discharge current correction factor in step (2) is determined based on the functional relationship between the charge and discharge current correction factor and the discharge current, wherein the functional relationship between the charge and discharge current correction factor and the discharge current is obtained by the following steps: charging the battery pack to a fully charged state at a normal temperature of 25°C; discharging the fully charged battery pack with a constant current, and recording the battery discharge amount at this time; discharging the fully charged battery pack while changing the size of the discharge current while ensuring that the temperature remains unchanged, and recording the battery discharge amount at this time; repeating the above steps to obtain the relationship between the discharge current and the actual discharge amount, and based on the relationship between the discharge current and the actual discharge amount, curve fitting is performed through MATLAB to obtain the functional relationship between the discharge current correction factor and the discharge current.

[0103] In this embodiment, the battery discharge capacity is different under different current conditions. Therefore, when estimating the SOC, the current needs to be corrected to achieve the purpose of correcting the battery capacity. The current correction factor calculation includes the following steps: (1) Charge the battery pack to a fully charged state at a normal temperature of 25°C. (2) Discharge the fully charged battery pack at a constant current and record the battery discharge capacity at this time. (3) Change the size of the discharge current to discharge the fully charged battery pack while ensuring that the temperature remains unchanged, and record the battery discharge capacity at this time. (4) Repeat the above steps to obtain the relationship between the discharge current and the actual discharge capacity as shown in Figure 2, and use MATLAB to perform curve fitting to obtain the functional relationship between the current correction factor and the discharge current. The specific functional relationship is as follows: K i (I) = (2.727e -7 *I 6 -1.358e -5 *I 5 +0.000263*I 4 -0.002466I 3 +0.01156I 2 -0.03206I+1.015) / 12, where I is the discharge current.

[0104] Optionally, the temperature correction factor in step (2) is determined according to the functional relationship between the temperature and the temperature correction factor, wherein the functional relationship between the temperature and the temperature correction factor is obtained by the following steps: setting the thermostat to -20°C, charging the battery pack to a fully charged state and then placing it in the thermostat, leaving it to stand so that the temperature of the battery pack is consistent with the temperature of the thermostat, fully discharging the battery at a standard rate of C / 3, and recording the actual discharge capacity of the battery; adjusting the temperature of the thermostat to 0°C, 20°C, 25°C, 30°C, and 40°C, respectively, repeating the above steps, and obtaining the functional relationship between the temperature and the temperature correction factor based on the actual discharge capacity at different temperature values ​​by using a MATLAB polynomial fitting algorithm.

[0105] In this embodiment, since the chemical substances inside the lithium battery are affected by temperature, the actual discharge capacity of the battery at different temperatures is also different. When the ambient temperature is low, the activity of the chemical substances inside the lithium battery is low, and the actual discharge capacity of the battery becomes smaller. As the temperature increases, the activity of the chemical substances inside the lithium battery increases, and the actual discharge capacity of the battery increases. The actual discharge capacity of the battery at different temperatures can be found out by experimental methods. The temperature correction factor calculation includes the following steps: (1) First charge the battery pack to a fully charged state. (2) Place the battery in a constant temperature box and set its temperature to -20°C. After standing for a period of time, let the battery temperature be consistent with the constant temperature of the constant temperature box. (3) Fully discharge the battery at a standard rate of C / 3 and record the actual discharge capacity of the battery. (4) Adjust the temperature of the constant temperature box to 0°C, 20°C, 25°C, 30°C, and 40°C respectively, and repeat steps (2) and (3). (5) The relationship between temperature and discharge capacity is obtained by using the MATLAB polynomial fitting algorithm as shown in Figure 3. The specific functional relationship is as follows: K t (T) = (-3.824e -7 *T 4 +2.261e -5 *T 3 -0.000661*T 2 +0.06481*T+10.44) / 12, where T is the ambient temperature.

[0106] Optionally, the charge and discharge cycle number correction factor in step (2) is determined based on the functional relationship between the charge and discharge cycle number and the charge and discharge cycle number correction factor, wherein the functional relationship between the charge and discharge cycle number and the charge and discharge cycle number correction factor is obtained by the following steps: charging and discharging the battery pack at a normal temperature of 25°C with a charge and discharge current of 1C, and recording the actual discharge capacity of the battery; allowing the battery to stand and repeating the above steps a preset number of times; obtaining the relationship between the charge and discharge cycle number and the discharge capacity by a MATLAB polynomial fitting algorithm, and determining the functional relationship between the charge and discharge cycle number and the charge and discharge cycle number correction factor based on the relationship between the charge and discharge cycle number and the discharge capacity.

[0107] In this embodiment, the capacity of the lithium battery will decay during use, and the capacity will decay after each charge and discharge cycle. The relationship between the number of charge and discharge cycles and the actual discharge capacity can be found through experimental methods, and the charge and discharge cycle correction factor can be calculated. The calculation of the charge and discharge cycle correction factor includes the following steps: (1) Charge and discharge the battery pack at a normal temperature of 25°C with a charge and discharge current of 1C, and record the actual discharge capacity of the battery. (2) Let the battery stand and repeat the above steps 150 times. (3) The relationship between the number of charge and discharge cycles and the discharge capacity is obtained by using the MATLAB polynomial fitting algorithm, as shown in Figure 4. The specific functional relationship is as follows: K n (N) = 3.704e -10 *N 4 +-1.056e -7 *N 3 +7.72e -6 *N 2 -0.0003367*N+1.001, where N is the number of charge and discharge cycles.

[0108] Step (3): When the battery pack stops working, the initial value SOC0 of the battery capacity is corrected according to the open circuit voltage method and the SOC value before the battery pack stops working.

[0109] In the embodiment of the present application, when the battery pack stops working, the initial SOC of the battery capacity is corrected according to the open circuit voltage method and stored in the single chip microcomputer.

[0110] Optionally, in step (3), correction is made based on the SOC value before standing still. When the SOC value before standing still is greater than 70%, the initial value SOC0 is corrected with the maximum cell voltage value. When the SOC is less than 40%, the initial value SOC0 is corrected with the minimum cell voltage value. In other cases, the initial value SOC0 is corrected with the average cell voltage value.

[0111] In this embodiment, according to the correspondence diagram between the open circuit voltage and SOC value of the battery pack in step (1), a two-dimensional array is established in the software, and its correspondence is written into the code. The initial SOC of the battery capacity is corrected in the static mode by looking up the table. When correcting the initial SOC, the correction is made according to the SOC value before standing still. When the SOC is greater than 70%, the SOC is corrected with the maximum cell voltage value. When the SOC is less than 40%, the SOC is corrected with the minimum cell voltage value. In other cases, the SOC is corrected with the average cell voltage value.

[0112] Step (4): If the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

[0113] In the embodiment of the present application, when the SOC of the battery pack is greater than 90% or less than 10%, the terminal correction of the SOC is performed according to the charging and discharging conditions of the battery at different rates. Since the discharge curve has non-linear characteristics when the SOC of the battery pack is greater than 90% or less than 10%, the voltage change of the battery is relatively small at this time. When the battery SOC is less than 10%, due to the small change in battery voltage, the traditional remaining power estimation method may prematurely estimate the remaining power as 0%, resulting in the battery entering the protection state prematurely and limiting the available energy of the battery. When the battery SOC is greater than 90%, similarly due to the small change in battery voltage, the traditional remaining power estimation method may prematurely estimate the remaining power as 100%, resulting in the battery entering the overcharge state prematurely and wasting the rechargeable energy of the battery. Therefore, terminal correction is required to improve the accuracy of the remaining power estimation.

[0114] Optionally, step (4) includes: determining whether the SOC value of the battery pack is greater than 90% or less than 10%; if it is greater than 90% or less than 10%, perform terminal correction, and record the battery voltage U1 and current I at this time x , and record the currents of the two discharge curves closest to I in different rates by the BMS x , denoted as I1 and I2, where I1 < I x < I2; record the remaining powers corresponding to I1 and I2 as SOC1 and SOC2 at the terminal voltage U1, and let:

[0115] Derive the corrected SOC at the current I from the above formula x , where x In this embodiment, the calculation process of the terminal correction includes the following steps: (1). Determine whether the SOC of the battery pack is greater than 90% or less than 10%, and if it is greater than 90% or less than 10%, perform terminal correction. (2). If the battery pack is in the terminal correction state, record the battery voltage U1 and current I at this time

[0116] , and record the currents of the two discharge curves closest to I in different rates by the BMS x , denoted as I1 and I2, where I1 < I x < I2. x < I2.

[0117] (3). Record the remaining powers corresponding to I1 and I2 as SOC1 and SOC2 at the terminal voltage U1, and let: (4). It can be derived from the third step the corrected SOC at the current I x , that is: x , that is:

[0118] By applying the technical solution of this embodiment, the SOC of the battery pack is updated in real time through an improved ampere-hour integration method, the correction factor affecting the battery capacity is analyzed, and a calculation process of the correction factor is given. When the correction conditions are met, the SOC is corrected according to the voltage value of the battery cell. At the end of charge and discharge, the SOC is corrected according to the charge and discharge conditions of the battery at different rates, thereby improving the accuracy and stability of the battery SOC estimation.

[0119] Furthermore, as a specific implementation of the method of FIG1 , an embodiment of the present application provides a battery SOC estimation device with terminal correction, which is used to:

[0120] When the battery pack is not working and is in a static state, the initial value SOC0 of the battery capacity is obtained according to the open circuit voltage method;

[0121] During the operation of the battery pack, the SOC value of the battery pack is updated in real time based on the preset correction factors affecting the battery capacity. The correction factors include the charge and discharge current correction factor, the temperature correction factor, and the charge and discharge cycle number correction factor.

[0122] When the battery pack stops working, the initial value SOC0 of the battery capacity is corrected according to the open circuit voltage method and the SOC value before stopping working;

[0123] If the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

[0124] Optionally, the device is further used for:

[0125] Obtaining a corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack determined by a curve fitting method;

[0126] Obtain the open circuit voltage of the battery pack according to the open circuit voltage method, and determine the initial value SOC0 of the battery capacity corresponding to the open circuit voltage of the battery pack based on the corresponding relationship diagram;

[0127] The corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack is drawn by the following steps:

[0128] Discharge the battery pack to the cut-off voltage in a constant current manner and leave it to stand until the battery pack is fully discharged;

[0129] Perform constant current charging on the fully discharged battery pack to 5% of the rated capacity, record the terminal voltage of the battery pack at this time and let it stand for a preset time;

[0130] Continue to charge the battery pack with constant current until it reaches 10% of the rated capacity, record the terminal voltage of the battery pack at this time, and let it stand for a preset time;

[0131] Continue to charge the battery pack at a constant current until the battery is fully charged, charging 5% of the rated capacity each time. After the battery is fully charged, a corresponding relationship diagram between the open circuit voltage and SOC of the battery pack is drawn by curve fitting.

[0132] Optionally, the device is further used for:

[0133] When the battery pack has been stationary for more than a certain time, the initial value SOC0 of the battery capacity is obtained again according to the open circuit voltage method, and the initial value SOC0 is updated.

[0134] Optionally, the calculation formula for updating the SOC value is:

[0135] Among them, SOC0 is the initial state of charge of the battery pack, C is the total capacity of the battery pack, η is the charge and discharge efficiency of the battery pack, i is the charge and discharge current, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

[0136] Optionally, the charge and discharge current correction factor is determined according to a functional relationship between the charge and discharge current correction factor and the discharge current, wherein the functional relationship between the charge and discharge current correction factor and the discharge current is obtained by the following steps:

[0137] Charge the battery pack to full power at a room temperature of 25°C.

[0138] Discharge the fully charged battery pack at a constant current and record the battery discharge capacity at this time;

[0139] While ensuring that the temperature remains constant, change the discharge current to discharge the fully charged battery pack and record the battery discharge capacity at this time;

[0140] Repeat the above steps to obtain the relationship between the discharge current and the actual discharge amount. Based on the relationship between the discharge current and the actual discharge amount, curve fitting is performed through MATLAB to obtain the functional relationship between the discharge current correction factor and the discharge current.

[0141] Optionally, the temperature correction factor is determined according to a functional relationship between the temperature and the temperature correction factor, wherein the functional relationship between the temperature and the temperature correction factor is obtained by the following steps:

[0142] Set the thermostat to -20°C, charge the battery pack to full charge, and then place it in the thermostat. Allow it to stand until the temperature of the battery pack is consistent with that of the thermostat. Discharge the battery completely at a standard rate of C / 3, and record the actual discharge capacity of the battery.

[0143] The temperature of the constant temperature box was adjusted to 0°C, 20°C, 25°C, 30°C, and 40°C, respectively. The above steps were repeated. Based on the actual discharge capacity at different temperature values, the functional relationship between temperature and temperature correction factor was obtained using the MATLAB polynomial fitting algorithm.

[0144] Optionally, the charge-discharge cycle number correction factor is determined based on a functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor, wherein the functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor is obtained by the following steps:

[0145] At a room temperature of 25°C, charge and discharge the battery pack at a charge and discharge current of 1C, and record the actual discharge capacity of the battery;

[0146] Let the battery rest and repeat the above steps for a preset number of times;

[0147] The relationship between the number of charge and discharge cycles and the discharge capacity is obtained by using a MATLAB polynomial fitting algorithm, and based on the relationship between the number of charge and discharge cycles and the discharge capacity, the functional relationship between the number of charge and discharge cycles and the charge and discharge cycle correction factor is determined.

[0148] Optionally, the device is further used for:

[0149] Correction is made based on the SOC value before standing still. When the SOC value before standing still is greater than 70%, the initial value SOC0 is corrected with the maximum cell voltage value. When the SOC is less than 40%, the initial value SOC0 is corrected with the minimum cell voltage value. In other cases, the initial value SOC0 is corrected with the average cell voltage value.

[0150] Optionally, the device is further used for:

[0151] Determine whether the SOC value of the battery pack is greater than 90% or less than 10%;

[0152] If it is greater than 90% or less than 10%, perform terminal correction and record the battery voltage U1 and current I x , and record the BMS closest to I at different magnifications x The currents of the two discharge curves are recorded as I1 and I2, where I1 x <I2;

[0153] Record the remaining power corresponding to I1 and I2 as SOC1 and SOC2 under the terminal voltage U1, and let:

[0154] From the above formula, we can deduce that the current I x Lower corrected SOC x ,in, ​

[0155] It should be noted that for other corresponding descriptions of the functional units involved in the battery SOC estimation device with terminal correction provided in the embodiment of the present application, reference can be made to the corresponding descriptions in the methods of Figures 1 to 2, and no further details will be given here.

[0156] The embodiment of the present application also provides a computer device, which can be specifically a personal computer, a server, a network device, etc. As shown in Figure 5, the computer device includes a bus, a processor, a memory and a communication interface, and may also include an input and output interface and a display device. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store location information. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the steps in each method embodiment are implemented.

[0157] Those skilled in the art will understand that the structure shown in FIG5 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0158] In one embodiment, a computer-readable storage medium is provided. The computer-readable storage medium may be non-volatile or volatile, and stores a computer program thereon. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0159] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0160] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0161] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0162] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0163] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that variations and improvements may be made by those skilled in the art without departing from the spirit of the present application, and such variations and improvements are within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A battery SOC estimation method with terminal correction, characterized in that: The following steps are involved: Step (1), when the battery pack is not working and is in a static state, obtaining an initial value SOC0 of the battery capacity according to an open circuit voltage method; Step (2), during the operation of the battery pack, the SOC value of the battery pack is updated in real time based on preset correction factors affecting the battery capacity, the correction factors including a charge and discharge current correction factor, a temperature correction factor, and a charge and discharge cycle number correction factor; Step (3), when the battery pack stops working, correcting the initial value SOC0 of the battery capacity according to the open circuit voltage method and the SOC value before stopping working; Step (4): if the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

2. A battery SOC estimation method with terminal correction according to claim 1, characterized in that: Step (1) comprises: Obtaining a corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack determined by a curve fitting method; Obtaining the open circuit voltage of the battery pack according to the open circuit voltage method, and determining the initial value SOC0 of the battery capacity corresponding to the open circuit voltage of the battery pack based on the corresponding relationship diagram; The corresponding relationship diagram between the open circuit voltage and the SOC value of the battery pack is drawn by the following steps: Discharge the battery pack to the cut-off voltage in a constant current manner and leave it to stand until the battery pack is fully discharged; Perform constant current charging on the fully discharged battery pack to 5% of the rated capacity, record the terminal voltage of the battery pack at this time and leave it alone for a preset time; Continue to charge the battery pack with constant current until it reaches 10% of the rated capacity, record the terminal voltage of the battery pack at this time and leave it alone for a preset time; Continue to charge the battery pack at a constant current until the battery is fully charged, charging 5% of the rated capacity each time. After full charge, the corresponding relationship between the open circuit voltage and SOC of the battery pack is drawn by curve fitting.

3. A battery SOC estimation method with terminal correction according to claim 2, characterized in that: The method further comprises: When the static time of the battery pack exceeds a certain value, the initial value SOC0 of the battery capacity is obtained again according to the open circuit voltage method, and the initial value SOC0 is updated.

4. The battery SOC estimation method with terminal correction according to claim 1, characterized in that: The calculation formula for updating the SOC value in step (2) is: Among them, SOC0 is the initial state of charge of the battery pack, C is the total capacity of the battery pack, η is the charge and discharge efficiency of the battery pack, i is the charge and discharge current, K n K is the charge and discharge cycle correction factor, t is the temperature correction factor, K i is the charge and discharge current correction factor.

5. A battery SOC estimation method with terminal correction according to claim 4, characterized in that: The charge and discharge current correction factor in step (2) is determined according to the functional relationship between the charge and discharge current correction factor and the discharge current, wherein the functional relationship between the charge and discharge current correction factor and the discharge current is obtained by the following steps: Charge the battery pack to full power at a normal temperature of 25°C; Discharge the fully charged battery pack at a constant current and record the battery discharge capacity at this time; While ensuring that the temperature remains unchanged, change the discharge current to discharge the fully charged battery pack and record the battery discharge capacity at this time; Repeat the above steps to obtain the relationship between the discharge current and the actual discharge amount, and based on the relationship between the discharge current and the actual discharge amount, perform curve fitting through MATLAB to obtain the functional relationship between the discharge current correction factor and the discharge current.

6. A battery SOC estimation method with terminal correction according to claim 4, characterized in that: The temperature correction factor in step (2) is determined according to the functional relationship between the temperature and the temperature correction factor, wherein the functional relationship between the temperature and the temperature correction factor is obtained by the following steps: Set the thermostat to -20℃, charge the battery pack to full power and then put it into the thermostat. Let it stand until the temperature of the battery pack is consistent with the temperature of the thermostat. Discharge the battery completely at the standard rate C / 3 and record the actual discharge capacity of the battery. The temperature of the constant temperature box was adjusted to 0°C, 20°C, 25°C, 30°C, and 40°C, respectively, and the above steps were repeated. The functional relationship between temperature and temperature correction factor was obtained through the MATLAB polynomial fitting algorithm based on the actual discharge capacity at different temperature values.

7. The improved ampere-hour integration method for battery SOC estimation with terminal correction according to claim 5, characterized in that: The charge-discharge cycle number correction factor in step (2) is determined based on the functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor, wherein the functional relationship between the charge-discharge cycle number and the charge-discharge cycle number correction factor is obtained by the following steps: At a room temperature of 25°C, charge and discharge the battery pack at a charge and discharge current of 1C, and record the actual discharge capacity of the battery; Let the battery rest and repeat the above steps for a preset number of times; The relationship between the number of charge and discharge cycles and the discharge capacity is obtained through the MATLAB polynomial fitting algorithm, and based on the relationship between the number of charge and discharge cycles and the discharge capacity, the functional relationship between the number of charge and discharge cycles and the charge and discharge cycle correction factor is determined.

8. The improved ampere-hour integration method for battery SOC estimation with terminal correction according to claim 1, characterized in that: In step (3), correction is made based on the SOC value before standing still. When the SOC value before standing still is greater than 70%, the initial value SOC0 is corrected with the maximum cell voltage value. When the SOC is less than 40%, the initial value SOC0 is corrected with the minimum cell voltage value. In other cases, the initial value SOC0 is corrected with the average cell voltage value.

9. The improved ampere-hour integration method for battery SOC estimation with terminal correction according to claim 1, characterized in that: Step (4) comprises: Determine whether the SOC value of the battery pack is greater than 90% or less than 10%; If it is greater than 90% or less than 10%, terminal correction is performed and the battery voltage U1 and current I are recorded. x , and record the BMS closest to I at different magnifications x The currents of the two discharge curves are denoted as I1 and I2, where I1 x <I2;​ Record the remaining power corresponding to I1 and I2 as SOC1 and SOC2 under the terminal voltage U1, and let: From the above formula, we can deduce that the current I x Lower corrected SOC x ,in, 10. A battery SOC estimation device with terminal correction, characterized in that: The device is used for: When the battery pack is not working and is in a static state, the initial value SOC0 of the battery capacity is obtained according to the open circuit voltage method; During the operation of the battery pack, the SOC value of the battery pack is updated in real time based on the preset correction factors affecting the battery capacity. The correction factors include the charge and discharge current correction factor, the temperature correction factor and the charge and discharge cycle number correction factor. When the battery pack stops working, the initial value SOC0 of the battery capacity is corrected according to the open circuit voltage method and the SOC value before stopping working; If the SOC value of the battery pack is greater than 90% or less than 10%, a terminal correction is performed on the SOC value.

Images