Method for determining battery state of charge, battery management system, and power-consuming device

Abstract

The present invention relates to a method for determining the state of charge of a battery, comprising: a) obtaining the state of charge at a current sampling time tn; b) obtaining a voltage Vn, a temperature Tn, and a charge rate Cn at the sampling time tn, and a voltage Vi at a sampling time ti, and calculating a voltage difference Vn-Vi, wherein the sampling time ti is the time at which the state of charge of the battery is obtained within a preset time period before the sampling time tn; c) when the voltage difference Vn-Vi is greater than or equal to a preset voltage threshold, calculating a voltage change rate based on the voltage difference Vn-Vi and the time difference tn-ti; and d) when the voltage change rate is greater than or equal to a preset voltage change rate threshold for the first time, obtaining a corrected state of charge of the battery as the actual state of charge of the battery based on the correspondence between the corrected state of charge of the battery and the preset voltage change rate threshold, temperature, and charge rate according to the temperature Tn and charge rate Cn of the battery at the sampling time tn.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for determining the state of charge of a battery, a battery management system, and an electrical device. Background Art

[0002] The State of Charge (SOC) is the ratio of a battery's remaining capacity to its fully charged capacity, representing the battery's remaining capacity. Accurately and timely understanding of the battery's SOC is crucial during battery life.

[0003] Currently, the main methods for estimating battery SOC are the ampere-hour integration method and the open-circuit voltage method. The ampere-hour integration method is affected by measurement accuracy, sampling frequency, and initial SOC errors, resulting in certain errors in the calculation results. These errors accumulate over time and cannot guarantee the accuracy of the battery's SOC during long-term operation. The open-circuit voltage (OCV) method, on the other hand, produces less accurate SOC because the battery's charging voltage exhibits different voltage curves under the influence of factors such as temperature and rate. The SOC corresponding to the same voltage value varies significantly. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a method for determining the state of charge of a battery, a battery management system (BMS), and a vehicle, so as to improve the estimation accuracy of the SOC.

[0005] In order to achieve the above object, a first aspect of the present invention provides a method for determining the state of charge of a battery, the method comprising:

[0006] a) obtaining the state of charge of the battery at the current sampling time tn;

[0007] b) obtaining the voltage Vn, temperature Tn, and charge rate Cn of the battery at the sampling time tn, and the voltage Vi of the battery at the sampling time ti, and calculating a voltage difference Vn-Vi between the voltage Vn and the voltage Vi, wherein the sampling time ti is a time at which the state of charge of the battery is obtained within a preset time period before the sampling time tn;

[0008] c) when the voltage difference Vn-Vi is greater than or equal to the preset voltage threshold, calculating the voltage change rate according to the voltage difference Vn-Vi and the time difference tn-ti between the sampling time tn and the sampling time ti; and

[0009] d) when the voltage change rate is greater than or equal to a preset voltage change rate threshold, obtaining, based on the temperature Tn and the charge rate Cn of the battery at the sampling time tn, a corrected state of charge of the battery as the actual state of charge of the battery from a correspondence between the corrected state of charge of the battery and the preset voltage change rate threshold, temperature, and charge rate.

[0010] By using the corresponding relationship between the corrected state of charge and the voltage change rate, temperature, and charge rate to correct the actual state of charge of the battery, a more accurate correction of the actual state of charge of the battery is achieved, thereby improving the accuracy of the actual SOC. In a preferred embodiment, the preset voltage threshold is 5mV.

[0011] In some embodiments, the sampling time ti is any one of n-1 sampling times at which the state of charge of the battery is obtained within the preset time period before the sampling time tn, where n is a positive integer, i=1, 2, 3..., n-1, and the method includes:

[0012] The voltage difference Vn-Vi between the voltage Vn and the voltage Vi is calculated in descending order from n-1 according to i. When the voltage difference Vn-Vi is greater than or equal to the preset voltage threshold, the voltage change rate is calculated according to the following formula:

[0013] Voltage change rate = (Vn-Vj) / (tn-tj), or

[0014] Voltage change rate = the preset voltage threshold / (tn-tj),

[0015] Wherein, Vn-Vj is the voltage difference that is greater than or equal to the preset voltage threshold for the first time among the voltage differences Vn-Vi, and tj is the sampling time for obtaining the voltage Vj.

[0016] By calculating the voltage difference Vn-Vi in descending order from n-1 according to i, and comparing the voltage difference Vn-Vi with the preset voltage threshold, on the one hand, the minimum voltage difference value greater than or equal to the preset voltage threshold is obtained, so that the calculated voltage change rate has the highest accuracy, thereby being able to more accurately correct the actual state of charge of the battery; on the other hand, there is no need to calculate all the voltage differences Vn-Vi, thereby reducing the amount of calculation.

[0017] In other embodiments, the sampling time ti is the earliest sampling time for obtaining the battery state of charge within the preset time period before the sampling time tn. In other words, ti is the earliest sampling time t1 among the n-1 sampling times, and only Vn-V1 is calculated each time, thereby reducing the amount of calculation and the amount of intermediate data.

[0018] In a preferred embodiment, when the state of charge of the battery at the sampling time tn is greater than or equal to a preset state of charge threshold, the voltage Vn, temperature Tn and charge rate Cn of the battery at the sampling time tn, as well as the voltage Vi of the battery at the sampling time ti are obtained, and the voltage difference Vn-Vi between the voltage Vn and the voltage Vi is calculated.

[0019] By obtaining the voltage difference Vn-Vi at the high end of charging to calculate the voltage change rate, and using the voltage change rate to modify the battery's state of charge, it is possible to correct the battery's actual state of charge in a wider high-end charging platform area. In the embodiment of the present application, the high end of charging is a state where the battery's state of charge is above the preset state of charge threshold and the battery's voltage change rate is above the preset voltage change rate threshold. Preferably, the preset state of charge threshold is 70%. Those skilled in the art will understand that since the type and composition of the battery used determines the position of the fluctuation in the battery's voltage change rate vs. SOC curve, the preset state of charge threshold can be set to a threshold that is suitable for the type and composition of the battery used.

[0020] In any embodiment, step d) comprises:

[0021] d1) when the voltage change rate is greater than or equal to the preset voltage change rate threshold, comparing the temperature Tn and the charge rate Cn of the battery at the sampling time tn with a preset temperature range and a preset charge rate range corresponding to the preset voltage change rate threshold; and

[0022] d2) When the temperature Tn and the charging rate Cn of the battery at the sampling time tn are both within the preset temperature range and the preset rate range, the corrected state of charge of the battery is obtained as the actual state of charge of the battery based on the corresponding relationship between the corrected state of charge of the battery and the preset voltage change rate threshold, temperature, and charging rate according to the temperature Tn and the charging rate Cn of the battery at the sampling time tn.

[0023] By determining whether the temperature and charging rate are within the preset range, abnormal data outside the corresponding relationship is avoided.

[0024] In any embodiment, wherein the preset voltage change rate threshold comprises a k-level voltage change rate threshold, and the method comprises:

[0025] When the voltage change rate is greater than or equal to an x-th level voltage change rate threshold and the x-th level correction flag is 1, obtaining, according to the temperature Tn and the charge rate Cn of the battery at the sampling time tn, a corrected state of charge of the battery as the actual state of charge of the battery from a correspondence between the corrected state of charge of the battery and the x-th level voltage change rate threshold, the temperature, and the charge rate, and setting the x-th level correction flag to 0;

[0026] When the voltage change rate is less than the x-th level voltage change rate threshold or the x-th level correction flag is 0, comparing the voltage change rate with the x-1-th level voltage change rate threshold;

[0027] Wherein x=k, k-1, ..., 3, 2, and k is greater than or equal to 3, and the x-th level voltage change rate threshold is greater than the x-1-th level voltage change rate threshold;

[0028] When the voltage change rate is greater than or equal to the first level voltage change rate threshold and the first level correction flag is 1, according to the temperature Tn and the charge rate Cn of the battery at the sampling time tn, a corrected state of charge of the battery is obtained as the actual state of charge of the battery from the corresponding relationship between the corrected state of charge of the battery and the first level voltage change rate threshold, temperature, and charge rate, and the first level correction flag is set to 0; and

[0029] When the voltage change rate is less than the first-level voltage change rate threshold or the first-level correction flag is 0, return to step b).

[0030] By setting a multi-level voltage change rate threshold, multiple corrections to the SOC can be achieved. The more levels of the voltage change rate threshold, the more opportunities to correct the SOC, and the lower the voltage change rate threshold, the earlier the correction opportunity can be obtained.

[0031] In any embodiment, the method includes filtering the voltage change rate, and comparing the filtered voltage change rate with the preset voltage change rate threshold in step d).

[0032] Since sampling errors or noise errors may cause voltage fluctuations, filtering can reduce the impact of voltage fluctuations caused by the sampling errors or noise errors.

[0033] In some embodiments, the filtered voltage rate of change is calculated according to the following formula:

[0034] Filtered voltage change rate = K1*(voltage change rate at sampling time tn)+K2*(voltage change rate at sampling time tm),

[0035] The sampling time tm is the most recent sampling time at which the voltage change rate is calculated before the sampling time tn, K1 and K2 are weight coefficients, and K1+K2=1.

[0036] Those skilled in the art should understand that the above algorithm for filtering the voltage change rate is exemplary, and in other embodiments, any suitable filtering algorithm may be used to filter the voltage change rate.

[0037] In any embodiment, the method comprises, before step b):

[0038] a1) determining whether the battery is in a charging state, if so, proceeding to the next step; if not, repeating step a1);

[0039] a2) Detecting and determining whether the charging current is stable and whether the voltage of the battery at the sampling time tn is valid, if so, proceeding to the next step; if not, returning to step a1).

[0040] By determining whether the battery is in a charging state, the SOC is limited to be corrected only during charging. By limiting the charging current to a stable state, the battery is ensured to be in a constant current charging state, thus ensuring the accuracy of the corrected SOC.

[0041] In addition, in the event of an error in the sampling chip, for example, the sampled voltage value may be erroneous. Since the overall concept of the present invention is based on the sampled voltage value, determining whether the current voltage is valid ensures the reliability of the corrected SOC. In some embodiments, whether the current voltage is valid is determined based on whether the voltage of the battery at the sampling time tn exceeds a preset sampling range. That is, the voltage of the battery at the sampling time tn is not a valid voltage when it is outside the preset sampling range. For example, the normal voltage range of a lithium iron phosphate battery is between 1.5V and 4.5V. In one embodiment, whether the voltage is valid is determined based on whether the voltage of the battery at the sampling time tn is between 500mV and 6000mV. That is, a voltage below 500mV or above 6000mV is not a valid voltage.

[0042] Those skilled in the art should understand that the method for correcting the state of charge of a battery described in the first aspect of the present invention and any possible embodiment of the first aspect can be combined with other SOC estimation methods to provide a more accurate SOC estimation for the battery.

[0043] The second aspect of the present invention provides a battery management system, which includes: at least one processor; and a memory connected to the at least one processor; wherein the memory stores instructions, and when the instructions are executed by the at least one processor, the instructions cause the at least one processor to execute the method for correcting the state of charge of a battery as described in the first aspect of the present invention and any possible implementation scheme of the first aspect.

[0044] The third aspect of the present invention provides a device comprising: a battery; and a battery management system according to the second aspect of the present invention. The battery can be used as a power source for the device, or as an energy storage unit for the device. The device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc. The device can select a battery according to its usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some implementation plans of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying any creative work.

[0046] Figure 1 A flow chart illustrating a method for correcting the state of charge of a battery according to one embodiment of the present invention is illustrated.

[0047] Figure 2 A flow chart illustrating a portion of a method for correcting the state of charge of a battery according to one embodiment of the present invention.

[0048] 3( a ) and 3 ( b ) are schematic diagrams illustrating a voltage-SOC curve and a voltage change rate-SOC curve of a lithium iron phosphate battery according to an embodiment of the present invention, respectively.

[0049] Figure 4 FIG. 4 is a schematic diagram of multiple voltage-SOC curves of a battery at different temperatures and charge rates according to an embodiment of the present invention.

[0050] Figure 5 FIG. 1 is a schematic diagram of multiple voltage change rate-SOC curves of a battery at different temperatures and charge rates according to one embodiment of the present invention.

[0051] Figure 6is a schematic diagram of a battery management system according to an embodiment of the present invention.

[0052] Figure 7 FIG. 1 is a schematic diagram of an electric device including a battery management system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0054] Figure 1 The flowchart of the method for correcting the state of charge of a battery according to one embodiment of the present invention is illustrated. The method for correcting the state of charge of a battery according to the present invention mainly corrects the SOC of the battery in the high-end charging region of the battery.

[0055] like Figure 1 As shown, in step 102, it is detected whether the battery is in a charging state according to the direction of the charging current. If the battery is in a charging state, step 104 is entered, otherwise step 102 is repeated. In some embodiments, in step 102, not only whether the battery is in a charging state is detected, but also whether the charging current is stable and whether the current voltage of the battery is valid. Specifically, in some embodiments, the charging current is judged to be in a constant current charging state, that is, having a constant charging rate, by detecting whether the charging current fluctuates. In addition, in some embodiments, whether the current voltage is valid is judged based on whether the current voltage of the battery exceeds a preset sampling range, that is, the current voltage is not a valid voltage when it is outside the preset sampling range. For example, the normal voltage range of a lithium iron phosphate battery is between 2.5V and 3.65V. In one embodiment, whether the voltage is valid is judged based on whether the voltage of the battery at the sampling time tn is between 500mV and 6000mV, that is, a voltage lower than 500mV or higher than 6000mV is not a valid voltage.

[0056] Typically, a battery management system (BMS) uses a preset sampling period to obtain or estimate the battery's SOC and collect data such as the battery's voltage, temperature, and charge rate. Assuming the current sampling time is tn, the voltage collected at sampling time tn is Vn, the temperature is Tn, and the charge rate is Cn. The sampling time immediately preceding the current sampling time tn is tn-1. In the embodiments of the present invention, the current sampling time tn is the most recent sampling time, and sampling time tn-1 is the second most recent sampling time.

[0057] In step 104, the battery's SOC at the current sampling time tn is obtained. Then, in step 106, it is detected whether the battery is in the high-end charging region. In some embodiments, whether the battery is in the high-end charging region is determined by determining whether the battery's SOC is greater than a preset SOC threshold. If the battery is in the high-end charging region, the process proceeds to step 108; otherwise, step 104 is repeated. As shown in Figure 3(b), the voltage change rate-SOC curve of a lithium iron phosphate battery has a significant bump around 20% SOC and around 60% SOC. However, the embodiments of the present invention are not suitable for such voltage change rate fluctuations. Therefore, in the lithium iron phosphate battery embodiments of Figures 3(a) and 3(b), the SOC threshold can be set to 70% to avoid the voltage change rate fluctuations in Figure 3(b). However, Figure 3(a) shows the theoretical range of the high-end charging region, where the SOC threshold is lower than the theoretical range of the high-end charging region. This shows that the SOC threshold is not the theoretical boundary of the high-end charging region but rather an operational strategy. In other embodiments, the type and composition of the battery used may be different, and the SOC at which the voltage change rate-SOC curve fluctuates may be different. Therefore, the state of charge threshold may be set to other appropriate values ​​based on the type and composition of the battery used. In some embodiments, additional conditions (such as voltage, current, etc.) may be added to determine whether the battery is in the high-end charging region.

[0058] In step 108, the voltage Vn, temperature Tn, and charge rate Cn at sampling time tn, as well as the voltage Vi at sampling time ti, are obtained. Sampling time ti is the time at which the battery's state of charge is obtained within a preset period of time before the current sampling time tn. In one embodiment, sampling time ti is any of n-1 sampling times at which the battery's state of charge is obtained within the preset period of time before the current sampling time tn, where n is a positive integer, i = 1, 2, 3, ..., n-1. Then, the voltage difference Vn-Vi between the voltage Vn and the voltage at sampling time ti is calculated, decreasing from n-1, as shown in step 110. Next, in step 112, it is determined whether the calculated voltage difference Vn-Vi is greater than or equal to a preset voltage threshold. If the calculated voltage difference Vn-Vi is less than the preset voltage threshold, the process returns to step 110, where the value of i is subtracted by 1 to calculate the voltage difference Vn-Vi. If the calculated voltage difference Vn-Vi is greater than or equal to the preset voltage threshold, the process proceeds to step 114, eliminating the need to calculate the voltage difference Vn-Vi for smaller values ​​of i. In this way, on the one hand, a minimum voltage difference greater than or equal to the preset voltage threshold is obtained, so that the calculated voltage change rate has the highest accuracy, thereby being able to more accurately correct the actual state of charge of the battery; on the other hand, there is no need to calculate all voltage differences Vn-Vi, which reduces the amount of calculation.

[0059] In one embodiment, in step 114, the voltage change rate is calculated according to the following formula:

[0060] Voltage change rate = (Vn-Vj) / (tn-tj),

[0061] Wherein, Vn-Vj is the voltage difference that is greater than or equal to the preset voltage threshold for the first time in the voltage difference Vn-Vi, and tj is the sampling time for obtaining the voltage Vj.

[0062] In another embodiment, the voltage change rate is calculated according to the following formula:

[0063] Voltage change rate = preset voltage threshold / (tn-tj),

[0064] Wherein, tj is the moment when the voltage Vj corresponding to the minimum value Vn-Vj is obtained when the voltage difference Vn-Vi is greater than or equal to the preset voltage threshold and is the minimum value.

[0065] In another embodiment, only the voltage difference Vn-V1 is calculated, and the voltage difference Vn-V1 is compared with a preset voltage threshold. When the voltage difference Vn-V1 is greater than or equal to the preset voltage threshold, the voltage change rate is calculated according to the following formula:

[0066] Voltage change rate = Vn-V1 / (tn-t1).

[0067] After calculating the voltage change rate, in step 116, the calculated voltage change rate is filtered to obtain a smooth voltage change rate-SOC curve. The voltage-SOC curve and the corresponding voltage change rate-SOC curve of the lithium iron phosphate battery are shown in Figure 3 (a) and Figure 3 (b), respectively. In one embodiment, the filtered voltage change rate can be calculated according to the following formula:

[0068] Filtered voltage change rate = K1*(voltage change rate at sampling time tn) + K2*(voltage change rate at sampling time tm)

[0069] The sampling time tm is the most recent sampling time at which the voltage change rate is calculated before the sampling time tn, K1 and K2 are weight coefficients, and K1+K2=1.

[0070] After obtaining the filtered voltage rate of change, the filtered voltage rate of change is compared with a voltage rate of change threshold selected from a voltage rate of change-SOC relationship table stored in the BMS (step 118). If the filtered voltage rate of change is less than the voltage rate of change threshold or the correction flag is 0, the process returns to step 104. If the filtered voltage rate of change is greater than or equal to the voltage rate of change threshold and the correction flag is 1, the battery's corrected state of charge is obtained by querying the voltage rate of change threshold-SOC lookup table based on the battery's temperature Tn and charge rate Cn at sampling time tn (step 120), and the correction flag is set to 0. Table 1 below lists a voltage rate of change threshold-SOC lookup table according to one embodiment. The lookup table is obtained by setting a specific temperature offline, charging at different charge rates, and recording the SOC value at each rate. The calibrated lookup table is then stored in the BMS.

[0071] Table 1 Voltage change rate threshold-SOC query table

[0072]

[0073] Figure 2 A flow chart illustrating a portion of a method for correcting the state of charge of a battery according to one embodiment of the present invention. Figure 1 The flowchart shown in Figure 2 Three levels of voltage change rate thresholds are set, namely, the third level voltage change rate threshold, the second level voltage change rate threshold, and the first level voltage change rate threshold, among which the third level voltage change rate threshold and the second level voltage change rate threshold are greater than the first level voltage change rate threshold.

[0074] After obtaining the filtered voltage rate of change, the filtered voltage rate of change is compared with a Level 3 voltage rate of change threshold selected from a voltage rate of change-SOC relationship table stored in the BMS (step 118a). This determines whether the filtered voltage rate of change is greater than or equal to the Level 3 voltage rate of change threshold for the first time. If the filtered voltage rate of change is greater than or equal to the Level 3 voltage rate of change threshold and the Level 3 correction flag is 1, the Level 3 correction flag is set to 0 and the battery's corrected state of charge is obtained by querying the Level 3 voltage rate of change threshold-SOC lookup table based on the battery's temperature Tn and charge rate Cn at sampling time tn (step 120).

[0075] When the filtered voltage rate of change is less than the Level 3 voltage rate of change threshold or the Level 3 correction flag is 0, the filtered voltage rate of change is compared with the Level 2 voltage rate of change threshold selected from the voltage rate of change-SOC relationship table stored in the BMS (Step 118b), i.e., determining whether the filtered voltage rate of change is greater than or equal to the Level 2 voltage rate of change threshold for the first time. Similarly, when the filtered voltage rate of change is greater than or equal to the Level 2 voltage rate of change threshold and the Level 2 correction flag is 1, the Level 2 correction flag is set to 0 and the battery's corrected state of charge is obtained by querying the Level 2 voltage rate of change threshold-SOC lookup table based on the battery's temperature Tn and charge rate Cn at sampling time tn (Step 120).

[0076] Similarly, when the filtered voltage rate of change is less than the Level 2 voltage rate of change threshold or the Level 2 correction flag is 0, the filtered voltage rate of change is compared with the Level 1 voltage rate of change threshold selected from the voltage rate of change-SOC relationship table stored in the BMS (Step 118c), i.e., determining whether the filtered voltage rate of change is greater than or equal to the Level 1 voltage rate of change threshold for the first time. If the filtered voltage rate of change is greater than or equal to the Level 1 voltage rate of change threshold and the Level 1 correction flag is 1, the Level 1 correction flag is set to 0, and the battery's corrected state of charge is obtained by querying the Level 1 voltage rate of change threshold-SOC lookup table based on the battery temperature Tn and charge rate Cn at sampling time tn (Step 120). If the filtered voltage rate of change is less than the Level 1 voltage rate of change threshold or the Level 1 correction flag is 0, the process returns to Step 104.

[0077] In a preferred embodiment, the voltage rate of change threshold for level 3 is 0.09, the voltage rate of change threshold for level 2 is 0.07, and the voltage rate of change threshold for level 1 is 0.05. As shown in Figure 3(b), the larger the voltage rate of change threshold, the greater the voltage fluctuation and the higher the correction accuracy; whereas, the smaller the voltage rate of change threshold, the earlier the correction opportunity is obtained. Those skilled in the art will appreciate that the voltage rate of change threshold and its number can be set based on the battery used; using more voltage rate of change thresholds increases the correction opportunities.

[0078] In addition, if Figure 2As shown, between step 118a and step 120, the battery temperature Tn and charge rate Cn at sampling time tn can be compared with the preset temperature range and preset charge rate range corresponding to the third-level voltage change rate threshold, step 119. Only when temperature Tn is within the preset temperature range and charge rate Cn is within the preset charge rate range, the battery's corrected state of charge is obtained by querying the third-level voltage change rate threshold-SOC lookup table based on temperature Tn and charge rate Cn. If temperature Tn is not within the preset temperature range or charge rate Cn is not within the preset charge rate range, the process returns to step 104. In the embodiment of Table 1, the preset temperature range is 10° to 31°C, and the preset charge rate range is 0.045-1.05°C. By determining whether the temperature and charge rate are within the preset ranges, abnormal data outside the third-level voltage change rate threshold-SOC lookup table is avoided. Similarly, between step 118b and step 120, the temperature Tn and the charging rate Cn can be compared with the preset temperature range and preset rate range corresponding to the second level voltage change rate threshold; between step 118c and step 120, the temperature Tn and the charging rate Cn can be compared with the preset temperature range and preset rate range corresponding to the first level voltage change rate threshold.

[0079] The inventors of the present invention have found in their research that the charging voltage of the battery presents different voltage-SOC curves under the influence of factors such as different temperatures (including the starting temperature), charging rate and starting SOC, such as Figure 4 As shown in the figure, in the high-end charging area, the different curves are more dispersed, and the high-end SOC corresponding to the same voltage value is quite different, so the corrected SOC accuracy is low. In contrast, the voltage change rate shows an increasing trend, and the voltage change rate-SOC curve is relatively stable, as shown in the figure. Figure 5 As shown in Table 2, the different curves in the high-end charging region are relatively concentrated, and the high-end SOC corresponding to the same voltage change rate value is relatively close, so the corrected SOC accuracy is high. Based on a large number of experiments and statistics, the SOC correction accuracy based on voltage and voltage change rate in the high-end charging region was obtained.

[0080] Table 2 SOC correction accuracy in the high-end charging area according to voltage and voltage change rate

[0081] SOC 80 85 90 95 100 Voltage <6％ <5％ <3％ <2％ 0 differential <3％ <2％ <2％ <1％ 0

[0082] Based on the same invention concept, please refer to Figure 6, an embodiment of the present invention further provides a battery management system 500, comprising: at least one processor 501; and a memory 502 communicatively connected to the processor 501; wherein the memory 502 stores instructions executable by the processor, and when the instructions are executed by the processor 501, the instructions cause the processor 501 to execute the method for correcting the state of charge of a battery provided in an embodiment of the present invention.

[0083] The processor 501 and the memory 502 are electrically connected, directly or indirectly, to enable data transmission or exchange. For example, these components may be electrically connected via one or more communication buses or signal buses. Each method for correcting the battery state of charge includes at least one software functional module that can be stored in the memory 502 in the form of software or firmware.

[0084] Processor 501 can be an integrated circuit chip with signal processing capabilities. Processor 501 can be a general-purpose processor, including a CPU (Central Processing Unit), an NP (Network Processor), etc.; it can also be a digital signal processor, an application-specific integrated circuit, an off-the-shelf programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present invention. The general-purpose processor can be a microprocessor or any conventional processor.

[0085] Memory 502 can store various software programs and modules, such as program instructions / modules corresponding to the method and apparatus for correcting the state of charge of a battery provided in embodiments of the present invention. Processor 501 executes the software programs and modules stored in memory 502 to perform various functional applications and data processing, thereby implementing the methods provided in embodiments of the present invention.

[0086] The memory 502 may include but is not limited to RAM (Random Access Memory), ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electric Erasable Programmable Read-Only Memory), etc.

[0087] The various embodiments and specific examples of the method for correcting the state of charge of a battery are also applicable to Figure 6 The battery management system 500 shown in FIG. 1 can be clearly understood by those skilled in the art through the detailed description of the method for correcting the state of charge of a battery. Figure 6 The implementation method of the battery management system 500 is not described in detail here for the sake of brevity of the description.

[0088] In addition, the present invention also provides a device, the device comprising: a battery; and Figure 6 The battery management system shown. The battery can be used as a power source or an energy storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a mobile phone, laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc. The battery for the device can be selected based on its usage requirements.

[0089] Figure 7 This is an example device. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Another example device may be a mobile phone, a tablet computer, a laptop computer, etc.

[0090] While the present invention has been described with reference to preferred embodiments, various modifications may be made and equivalent components may be substituted without departing from the scope of the present invention. In particular, the various technical features described in the various embodiments may be combined in any manner, provided no structural conflicts exist. The present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A method for determining a state of charge of a battery, the method comprising: a1) Determine whether the battery is in a charging state based on the direction of the charging current; a) Obtaining the state of charge of the battery at the current sampling time tn; b) obtaining the voltage Vn, temperature Tn, and charge rate Cn of the battery at the sampling time tn, and the voltage Vi of the battery at the sampling time ti, and calculating a voltage difference Vn-Vi between the voltage Vn and the voltage Vi, wherein the sampling time ti is a time at which the state of charge of the battery is obtained within a preset time period before the sampling time tn; c) when the voltage difference Vn-Vi is greater than or equal to a preset voltage threshold, calculating the voltage change rate according to the voltage difference Vn-Vi and the time difference tn-ti between the sampling time tn and the sampling time ti; and d) when the voltage change rate is greater than or equal to a preset voltage change rate threshold, obtaining, based on the temperature Tn and the charge rate Cn of the battery at the sampling time tn, a corrected state of charge of the battery as the actual state of charge of the battery from a correspondence between the corrected state of charge of the battery and the preset voltage change rate threshold, temperature, and charge rate; The sampling time ti is any one of n-1 sampling times for obtaining the state of charge of the battery within the preset time period before the sampling time tn, where n is a positive integer, i=1, 2, 3..., n-1, and the method includes: The voltage difference Vn-Vi between the voltage Vn and the voltage Vi is calculated in descending order from n-1 according to i. When the voltage difference Vn-Vi is greater than or equal to the preset voltage threshold, the voltage change rate is calculated according to the following formula: Voltage change rate = (Vn-Vj) / (tn-tj), or Voltage change rate = the preset voltage threshold / (tn-tj), Wherein, Vn-Vj is the voltage difference that is greater than or equal to the preset voltage threshold for the first time among the voltage differences Vn-Vi, and tj is the sampling time for obtaining the voltage Vj. 2 . The method according to claim 1 , wherein the sampling time ti is the earliest sampling time for obtaining the state of charge of the battery within the preset time period before the sampling time tn.

3. The method according to claim 1 or 2, wherein only when the state of charge of the battery at the sampling time tn is greater than or equal to a preset state of charge threshold, the voltage Vn, temperature Tn, and charge rate Cn of the battery at the sampling time tn, as well as the voltage Vi of the battery at the sampling time ti are obtained, and the voltage difference Vn-Vi between the voltage Vn and the voltage Vi is calculated.

4. The method according to claim 1 or 2, wherein step d) comprises: d1) when the voltage change rate is greater than or equal to a preset voltage change rate threshold, comparing the temperature Tn and the charge rate Cn of the battery at the sampling time tn with a preset temperature range and a preset charge rate range corresponding to the preset voltage change rate threshold; and d2) When the temperature Tn and the charging rate Cn of the battery at the sampling time tn are both within the preset temperature range and the preset rate range, the corrected state of charge of the battery is obtained as the actual state of charge of the battery based on the corresponding relationship between the corrected state of charge of the battery and the preset voltage change rate threshold, temperature, and charging rate according to the temperature Tn and the charging rate Cn of the battery at the sampling time tn.

5. The method according to claim 1 or 2, wherein the preset voltage change rate threshold comprises a k-level voltage change rate threshold, and the method comprises: When the voltage change rate is greater than or equal to an x-th level voltage change rate threshold and the x-th level correction flag is 1, obtaining, according to the temperature Tn and the charge rate Cn of the battery at the sampling time tn, a corrected state of charge of the battery as the actual state of charge of the battery from a correspondence between the corrected state of charge of the battery and the x-th level voltage change rate threshold, the temperature, and the charge rate, and setting the x-th level correction flag to 0; When the voltage change rate is less than the x-th level voltage change rate threshold or the x-th level correction flag is 0, comparing the voltage change rate with the x-1-th level voltage change rate threshold; Wherein x=k, k-1, ..., 3, 2, and k is greater than or equal to 3, and the x-th level voltage change rate threshold is greater than the x-1-th level voltage change rate threshold; When the voltage change rate is greater than or equal to a first-level voltage change rate threshold and the first-level correction flag is 1, according to the temperature Tn and the charge rate Cn of the battery at sampling time tn, and from the corresponding relationship between the corrected state of charge of the battery and the first-level voltage change rate threshold, temperature, and charge rate, obtain the corrected state of charge of the battery as the actual state of charge of the battery, and set the first-level correction flag to 0; and When the voltage change rate is less than the first-level voltage change rate threshold or the first-level correction flag is 0, return to step b).

6. The method according to claim 1 or 2, wherein the method comprises: The voltage change rate is filtered, and in step d), the filtered voltage change rate is compared with the preset voltage change rate threshold.

7. The method of claim 6, wherein the filtered voltage change rate is calculated according to the following formula: Filtered voltage change rate = K1*(voltage change rate at sampling time tn)+K2*(voltage change rate at sampling time tm), The sampling time tm is the most recent sampling time at which the voltage change rate is calculated before the sampling time tn, K1 and K2 are weight coefficients, and K1+K2=1.

8. The method according to claim 1 or 2, wherein the method comprises, before step b): a2) detecting and determining whether the charging current is stable and whether the voltage of the battery at the sampling time tn is valid, and if so, proceeding to the next step; If not, return to step a1).

9. A battery management system, comprising: at least one processor; as well as a memory coupled to the at least one processor; The memory stores instructions, and when the instructions are executed by the at least one processor, the instructions cause the at least one processor to execute the method for determining the state of charge of a battery according to any one of claims 1 to 8.

10. An electrical device, comprising: Battery; as well as The battery management system according to claim 9.

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