Battery state-of-charge estimation method for small electronic device

Abstract

The invention provides a battery state-of-charge estimation method for small electronic equipment, and relates to the technical field of battery state-of-charge estimation. The method comprises the following steps: judging that the current operation mode of the small electronic equipment is a charging mode, a non-on-load discharging mode or an on-load discharging mode; acquiring a voltage-SOC parameter table corresponding to the current operation mode according to the current operation mode; and acquiring a voltage signal of a battery in the small electronic equipment in real time, judging whether the voltage signal exceeds a voltage boundary value of the voltage-SOC parameter table corresponding to the current operation mode, if so, correcting the SOC value, and if not, calculating to obtain the SOC value through a linear interpolation value formula, and setting a corresponding gear mark according to the SOC value. The SOC estimation method is high in precision, low in cost and low in complexity, it can be ensured that a user rapidly and visually knows the electric quantity state of the battery, and the strict limitation of a battery management system in small electronic equipment on hardware cost and computing resources is met.

Description

Technical Field

[0001] The present invention relates to the technical field of battery state of charge estimation, and in particular to a method for estimating the battery state of charge of a small electronic device. Background Art

[0002] Battery State of Charge (SOC) is a key metric used to assess a battery's current remaining energy, providing users with accurate information on the battery's remaining capacity. With the widespread adoption of small electronic devices (such as handheld devices) with simple battery management systems and / or systems that lack complex hardware sensors (such as current sensors), battery SOC estimation has become particularly important. Battery SOC estimation allows users to promptly understand the remaining charge of small electronic devices, allowing them to optimally plan their usage. It also helps prevent overcharging or over-discharging, extending the battery's lifespan. It also avoids safety issues caused by overcharging or over-discharging, improving the overall performance of electronic devices. Existing SOC estimation methods primarily include the open-circuit voltage method and the ampere-hour integration method.

[0003] The open-circuit voltage method estimates battery SOC by measuring the battery's voltage under no-load conditions. However, due to temperature and battery aging, its accuracy is low and it cannot monitor dynamic changes in real time. The ampere-hour integration method relies on a current sensor or shunt to sample current. However, if the electronic device's circuit does not pass through the branch where the current sensor or shunt is located, or if the operating current is too low to meet the minimum resolution for current sampling, then no current can be collected, and battery SOC estimation cannot be performed.

[0004] Currently, for battery SOC estimation of electronic devices with low operating current, a patent proposes a low-power device SOC compensation method. The method calculates the capacity loss caused by the operation of the device and compensates the SOC value by the battery management system when it is powered on next time. This method compares the compensated SOC value with the SOC value found in the voltage-SOC table and analyzes the difference to accurately derive the true SOC value. The accuracy of the table lookup is improved by compensating the voltage, thereby improving the credibility of the calculation results. However, this method relies on the rated current of the device to calculate the power consumption, and the real-time operating current may fluctuate, resulting in a deviation between the power consumption compensation value and the actual loss. In addition, multiple comparisons and calculations are required, which increases the computational burden of the battery management system, especially for low-power devices. Moreover, the weight coefficient needs to be determined based on the operating current of the device and the rated capacity of the battery. In some cases, if the weight distribution is inaccurate, the final SOC estimation result will be affected.

[0005] In order to meet the needs of high-precision, low-cost, and low-complexity SOC estimation, the industry urgently needs to develop a battery state of charge estimation method for small electronic devices to meet the strict limitations of hardware costs and computing resources of battery management systems for small electronic devices. Summary of the Invention

[0006] In response to the above-mentioned problems, the operating current of the electronic device does not reach the sampling resolution, resulting in the ampere-hour integration method being unable to estimate the SOC well; and in the SOC compensation method, the power consumption compensation value will deviate from the actual loss due to the actual operating current fluctuation, and multiple comparisons and calculations increase the computational burden, which affects the SOC estimation results.

[0007] This application proposes a method for estimating the state of charge of a battery of a small electronic device, comprising: S21: Determine whether the current operating mode of the small electronic device is a charging mode, an unloaded discharge mode, or a loaded discharge mode; S22: Acquire a voltage-SOC parameter table corresponding to the current operating mode according to the current operating mode; S23: collecting a voltage signal of a battery in the small electronic device in real time; S24: Determine whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode; if so, correct the SOC value; if not, calculate the SOC value using a linear interpolation formula; and S25: Setting a corresponding gear position flag according to the SOC value.

[0008] Optionally, the step S24 of determining whether the voltage signal exceeds a voltage boundary value of a voltage-SOC parameter table corresponding to the current operating mode, and if so, correcting the SOC value, includes: When the voltage signal is higher than the voltage boundary value of the voltage-SOC parameter table corresponding to the charging mode, the corrected SOC value is 100%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the no-load discharge mode, the corrected SOC value is 0%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the loaded discharge mode, the corrected SOC value is 0%.

[0009] Optionally, if no in step S23, the SOC value is calculated by a linear interpolation formula, including: When the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the current operating mode, the SOC value is calculated using a linear interpolation formula. The linear interpolation formula is: , Wherein, when the current operation mode of the small electronic device is the charging mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage signal; When the current operating mode of the small electronic device is the no-load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage signal; When the current operating mode of the small electronic device is the load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage signal.

[0010] Optionally, before step S21, the method for estimating the state of charge of a battery of a small electronic device further includes: S11: Determine whether the small electronic device is in an initialization state or a dynamic operation state.

[0011] Optionally, when the small electronic device is in the dynamic operating state, after step S23, the method further includes: S231: limiting a change direction of the SOC value according to the current operating mode; Wherein, when the current operating mode of the small electronic device is the charging mode, the SOC value is the larger value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operating mode of the small electronic device is the no-load discharge mode, the SOC value is the smaller value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operating mode of the battery in the small electronic device is the loaded discharge mode, the SOC value is the smaller value between the SOC value calculated at the current moment and the SOC value calculated at the previous moment.

[0012] Optionally, when the small electronic device is in the dynamic operating state, the method for estimating the battery state of charge of the small electronic device further includes: S12: Determine whether the current operating mode has changed. If so, keep the SOC value unchanged within the SOC holding time, and after exceeding the SOC holding time, enter step S22. If not, enter step S22.

[0013] Optionally, setting a corresponding gear position flag according to the SOC value in step S25 includes: When the SOC value is ≤20%, the gear flag is set to 0; When 20%<the SOC value≤40%, the gear position flag is set to 25; When 40%<the SOC value≤60%, the gear position flag is set to 50; When 60%<the SOC value≤80%, the gear position flag is set to 75; When 80%<the SOC value≤100%, the gear flag is set to 100.

[0014] Optionally, the method for estimating the state of charge of a battery of a small electronic device further includes: returning the SOC value and the gear position flag.

[0015] Optionally, before step S21, the following steps are further included: S01: Perform charging test and discharging test on the small electronic device in charging mode, no-load discharge mode and loaded discharge mode respectively, and establish a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the no-load discharge mode and a voltage-SOC parameter table corresponding to the loaded discharge mode respectively.

[0016] Preferably, step S01 of performing a charging test and a discharging test on the small electronic device in a charging mode, an off-load discharge mode, and an on-load discharge mode, respectively, and establishing a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the off-load discharge mode, and a voltage-SOC parameter table corresponding to the on-load discharge mode, respectively, includes: respectively obtaining a charging nominal capacity, a first discharging nominal capacity, and a second discharging nominal capacity; Averaging the charging nominal capacity, the first discharging nominal capacity, and the second discharging nominal capacity to obtain an average nominal capacity; Dividing the average nominal capacity into n equal parts to obtain n+1 SOC values; Obtaining voltage values corresponding to the n+1 SOC values in the charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Obtaining voltage values corresponding to the n+1 SOC values in the no-load discharge mode to establish a voltage-SOC parameter table corresponding to the no-load discharge mode; The voltage values corresponding to the n+1 SOC values in the on-load discharge mode are obtained to establish a voltage-SOC parameter table corresponding to the on-load discharge mode.

[0017] Optionally, before step S21, the following steps are further included: S02: Obtaining a first reference voltage in the on-load discharge mode and a second reference voltage in the charging mode; When the current operation mode of the small electronic device changes, the SOC maintenance time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage is recorded.

[0018] Preferably, obtaining the first reference voltage in the loaded discharge mode and the second reference voltage in the charging mode in step S02 includes: Dividing the average nominal capacity into m equal parts to obtain m+1 SOC values; Obtaining voltage values corresponding to the m+1 SOC values in a charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Obtaining voltage values corresponding to the m+1 SOC values in the on-load discharge mode to establish a voltage-SOC parameter table corresponding to the on-load discharge mode; Calculate and obtain a first reference voltage corresponding to the i-th SOC value in the on-load discharge mode according to a discharge fitting formula; The second reference voltage corresponding to the i-th SOC value in the charging mode is calculated according to the charging fitting formula, where 1 <i<m; In step S02, when the current operating mode of the small electronic device changes, recording the SOC holding time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage includes: First, the current operating mode of the small electronic device is set to the loaded discharge mode. When the voltage of the battery in the small electronic device drops to the first reference voltage, the current operating mode of the small electronic device is switched to the charging mode, and the SOC maintenance time required for the voltage of the battery in the small electronic device to rise from the first reference voltage to the second reference voltage is recorded.

[0019] The beneficial effects of this application include at least: The battery SOC estimation method of this embodiment includes determining whether the current operating mode of the small electronic device is a charging mode, an unloaded discharge mode, or a loaded discharge mode; obtaining a voltage-SOC parameter table corresponding to the current operating mode according to the current operating mode; collecting the voltage signal of the battery in the small electronic device in real time; determining whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode, and if so, correcting the SOC value; if not, obtaining the SOC value by calculating the linear interpolation formula and setting the gear flag according to the SOC value. The SOC values under different operating modes can be obtained by the real-time collected voltage signal, which is not affected by the current and has the advantages of high accuracy, low cost, and low complexity. It can also ensure that users can quickly and intuitively understand the approximate power status of the battery in the small battery device, while meeting the strict restrictions on hardware cost and computing resources of the battery management system in the small electronic device.

[0020] In addition, when the current operating mode changes, keeping the SOC value unchanged within the SOC holding time can effectively ensure that the operating mode switching is relatively smooth, making the SOC value stable and not jumping, and effectively avoiding the problem of SOC value jumping caused by voltage fluctuations.

[0021] The above has generally summarized the features and technical advantages of the present application so that the following detailed description of the application can be better understood. The additional features and advantages of the present application will be described below, which form the subject matter of the claims of the present application. It will be understood by those skilled in the art that the disclosed concepts and specific embodiments can be easily utilized as the basis for modifying or designing other structures or processes for achieving the same purpose of the present application. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present application as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more complete understanding of the present application and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which: Figure 1 A flow chart showing voltage-SOC parameter calibration for a small electronic device in different operating modes according to an embodiment of the present application is shown; Figure 2A flow chart of SOC holding time calibration during operation mode switching of a small electronic device according to an embodiment of the present application is shown; Figure 3 A flow chart showing a method for estimating battery SOC of a small electronic device according to an embodiment of the present application is shown; Figure 4 A voltage-SOC fitting curve diagram of a battery in a small electronic device in a charging mode according to an embodiment of the present application is shown; Figure 5 A voltage-SOC fitting curve diagram of a battery in a small electronic device in an embodiment of the present application in an unloaded discharge mode is shown; Figure 6 A voltage-SOC fitting curve diagram of a battery in a small electronic device in an embodiment of the present application in a loaded discharge mode is shown.

[0023] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0024] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0025] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The terms "first," "second," "third," and so on (if any) in the description and claims of the present invention and in the drawings are used to distinguish similar items and are not necessarily used to describe a particular order or sequential sequence.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "coupled," "connected," and "connected" should be understood broadly. For example, they may refer to electrical connection or mutual communication, direct connection or indirect connection through an intermediary, internal communication between two components, or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0027] In addition, numerous specific details are provided in the following detailed description to better illustrate the present invention. Those skilled in the art will appreciate that the present invention can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of the present invention.

[0028] Existing battery SOC estimation methods require high-precision current sensors to collect current signals, which increases system cost and complexity. In some applications using simple battery management systems and / or systems lacking complex hardware sensors (such as current sensors), existing battery SOC estimation methods are not well-suited because they do not sample current signals or the sampled current signals are inaccurate. However, the battery SOC estimation method for a small electronic device provided in the embodiments of the present application estimates the SOC value in real time using a real-time collected voltage signal, eliminating the need for current signals. This method is well-suited, provides relatively accurate estimations, and effectively reduces costs.

[0029] The battery state of charge estimation method for small electronic devices disclosed in this application is applicable to battery types, such as ternary lithium batteries, whose charge and discharge characteristics have been calibrated and whose voltage-SOC curves under different operating modes are relatively linear. By calibrating the charge and discharge characteristics to obtain a voltage-SOC parameter table under different operating modes and collecting the battery's voltage signal in real time, the battery's SOC value can be estimated based on the voltage-SOC parameter table and voltage signal under different operating modes, allowing users to quickly and intuitively understand the battery's approximate state of charge while meeting the strict hardware cost and computing resource constraints of battery management in small electronic devices.

[0030] This application is applicable to small electronic devices with multiple operating modes (such as charging mode, unloaded discharge mode, and loaded discharge mode), and can dynamically adjust the SOC when switching between operating modes to ensure that the operating mode switching is relatively smooth and the SOC value is stable and does not jump.

[0031] In this application, small electronic devices are generally handheld devices, household electronic devices, etc., such as handheld analyzers. The capacity of the battery in a small electronic device is generally a few ampere hours, such as 4Ah.

[0032] The present invention relates to a method for estimating the state of charge (SOC) of a battery in a small electronic device. The method comprises a preliminary testing phase and an SOC estimation phase. The preliminary testing phase is used to obtain a voltage-SOC parameter table under different operating modes and an SOC holding time, i.e., the SOC value remains unchanged during the SOC holding time.

[0033] The preliminary test phase mainly includes the voltage-SOC parameter table calibration test and the SOC retention time test during the operation mode switching process. The voltage-SOC parameter table calibration test is used to obtain the voltage-SOC parameter table under different operation modes. The SOC retention time test during the operation mode switching process is mainly used to obtain the SOC retention time, so that the battery SOC value remains unchanged during the SOC retention time. However, the SOC value needs to be re-estimated in real time after the SOC retention time. The voltage-SOC parameter table calibration test and the SOC retention time test during the operation mode switching process can be calibrated offline and stored in the memory of a small electronic device for subsequent battery SOC estimation.

[0034] The SOC estimation phase is used to estimate the battery SOC value in real time based on the voltage-SOC parameter table under different operating modes, SOC retention time, and real-time collected voltage signals obtained in the previous test phase. Specifically, the SOC value of the battery in the small electronic device is estimated in real time in the initialization state based on the voltage-SOC parameter table under different operating modes and the real-time collected voltage signals; or the SOC value of the battery in the small electronic device is estimated in real time in the dynamic operating state based on the voltage-SOC parameter table under different operating modes, the real-time collected voltage signals, and SOC retention time.

[0035] See also Figure 1 The flowchart of voltage-SOC parameter calibration for a small electronic device in different operating modes according to an embodiment of the present application is shown. The method for estimating the battery state of charge of a small electronic device includes: Step S01: performing charging tests and discharging tests on the small electronic device in a charging mode, an off-load discharge mode, and an on-load discharge mode, respectively, and establishing a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the off-load discharge mode, and a voltage-SOC parameter table corresponding to the on-load discharge mode, respectively.

[0036] Specifically, step S01 is a voltage-SOC parameter table calibration test during the preliminary testing phase. In step S01, the battery in the small electronic device is subjected to charge and discharge tests in three operating modes (e.g., charging mode, off-load discharge mode, and on-load discharge mode). The corresponding relationship between voltage and SOC values in different operating modes is recorded, and corresponding voltage-SOC parameter tables are established. Specifically, the voltage-SOC parameter table corresponding to the charging mode, the voltage-SOC parameter table corresponding to the off-load discharge mode, and the voltage-SOC parameter table corresponding to the on-load discharge mode are established. The charging mode refers to charging the battery in the small electronic device via an external power source. The off-load discharge mode refers to the small electronic device being disconnected from any external device and consuming its own power when turned on. The on-load discharge mode refers to the small electronic device being connected to the battery management system to obtain data while also providing power to the battery management system. The battery in the small electronic device needs to discharge externally and consumes its own power.

[0037] Furthermore, step S01 performs charging test and discharging test on the small electronic device in charging mode, off-load discharge mode and on-load discharge mode, respectively, and establishes a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the off-load discharge mode, and a voltage-SOC parameter table corresponding to the on-load discharge mode, respectively, including: Step S011: obtaining a charging nominal capacity, a first discharging nominal capacity, and a second discharging nominal capacity respectively; Step S012: averaging the charging nominal capacity, the first discharging nominal capacity, and the second discharging nominal capacity to obtain an average nominal capacity; Step S013: Divide the average nominal capacity into n equal parts to obtain n+1 SOC values; Step S014: obtaining voltage values corresponding to the n+1 SOC values in the charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Step S015: obtaining voltage values corresponding to the n+1 SOC values in the no-load discharge mode to establish a voltage-SOC parameter table corresponding to the no-load discharge mode; Step S016: obtaining voltage values corresponding to the n+1 SOC values in the on-load discharge mode to establish a voltage-SOC parameter table corresponding to the on-load discharge mode.

[0038] Specifically, in step S011, in the charging mode, a full charge test is performed on the battery in the small electronic device, and the host computer is used to collect its voltage, current, and the time required from the start of charging to the voltage reaching the charging cut-off voltage V1, and the charging nominal capacity can be obtained by the ampere-hour integration method. In the unloaded discharge mode, a full discharge test is performed on the battery in the small electronic device, and the host computer is used to collect its voltage, current, and the time required from the full charge state to the voltage reaching the unloaded cut-off voltage V2, and the first discharge nominal capacity can be obtained by the ampere-hour integration method. In the unloaded discharge mode, a full discharge test is performed on the battery in the small electronic device, and the host computer is used to collect its voltage, current, and the time required from the full charge state to the voltage reaching the loaded cut-off voltage V3, and the second discharge nominal capacity can be obtained by the ampere-hour integration method.

[0039] At the same time, record the key voltage parameters during the test: charge cut-off voltage V1, no-load discharge cut-off voltage V2, and load discharge cut-off voltage V3. Use the charge cut-off voltage V1 as the voltage boundary value of the voltage-SOC parameter table corresponding to the charge mode; use the no-load discharge cut-off voltage V2 as the voltage boundary value of the voltage-SOC parameter table corresponding to the no-load discharge mode; and use the load discharge cut-off voltage V3 as the voltage boundary value of the voltage-SOC parameter table corresponding to the load discharge mode.

[0040] Furthermore, in step S012, the charging nominal capacity, the first discharging nominal capacity, and the second discharging nominal capacity are averaged to obtain an average nominal capacity.

[0041] Furthermore, in the charging mode, the battery in the small electronic device is charged and tested, and the voltage, current and time data at each moment are collected by the host computer. The corresponding capacity at each moment can be obtained through the ampere-hour integration method, so that the capacity at each moment corresponds to the voltage one by one.

[0042] In the no-load discharge mode, the battery in the small electronic device is discharged and tested. The voltage, current and time data at each moment are collected by the host computer. The capacity at each moment can be obtained by the ampere-hour integration method, so that the capacity at each moment corresponds to the voltage one by one.

[0043] In the no-load discharge mode, the battery in the small electronic device is discharged and tested. The voltage, current and time data at each moment are collected by the host computer. The capacity at each moment can be obtained by the ampere-hour integration method, so that the capacity at each moment corresponds to the voltage one by one.

[0044] Furthermore, in step S013, the average nominal capacity is divided into n equal parts to obtain n+1 SOC values. Taking n=10 as an example, 11 SOC values can be obtained, namely, SOC=[0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%]. Selecting a larger difference between two SOC values helps avoid errors caused by current fluctuations. In this embodiment, n=10 is used as an example for illustration, but this does not limit the value of n.

[0045] In step S014 , in the charging mode, the voltage value corresponding to each SOC value is obtained to establish a voltage-SOC parameter table corresponding to the charging mode.

[0046] voltage = [3402, 3807, 3839, 3884, 3920, 3953, 3969, 3981, 3993, 4014, 4034] (unit: mV); SOC=[0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%].

[0047] Likewise, in step S015 , in the no-load discharge mode, the voltage value corresponding to each SOC value is obtained to establish a voltage-SOC parameter table corresponding to the no-load discharge mode.

[0048] In step S016 , in the on-load discharge mode, the voltage value corresponding to each SOC value is obtained to establish a voltage-SOC parameter table corresponding to the on-load discharge mode.

[0049] See also Figure 2 The flowchart of SOC holding time calibration during operation mode switching of a small electronic device according to an embodiment of the present application is shown; before step S21, the following steps are also included: S02: Obtaining a first reference voltage in the on-load discharge mode and a second reference voltage in the charging mode; When the current operation mode of the small electronic device changes, the SOC maintenance time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage is recorded.

[0050] Specifically, step S02 is an SOC holding time test during the operation mode switching process in the preliminary test phase. First, a first reference voltage corresponding to the SOC value selected in the load discharge mode and a second reference voltage corresponding to the selected SOC value in the charging mode are obtained. When the current operation mode of the small electronic device changes, for example, switching from the load discharge mode to the charging mode, the SOC holding time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage is recorded. In this embodiment, it is necessary to keep the SOC value unchanged during the SOC holding time so that switching between different operation modes can be smoothly processed, and sudden changes in the SOC value due to voltage fluctuations can be avoided, so that the SOC value is stable and does not jump.

[0051] Furthermore, obtaining the first reference voltage in the loaded discharge mode and the second reference voltage in the charging mode in step S02 includes: Step S021: Divide the average nominal capacity into m equal parts to obtain m+1 SOC values; Step S022: obtaining voltage values corresponding to the m+1 SOC values in the charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Step S023: obtaining voltage values corresponding to the m+1 SOC values in the on-load discharge mode to establish a voltage-SOC parameter table corresponding to the on-load discharge mode; Step S024: Calculating and obtaining a first reference voltage corresponding to the i-th SOC value in the on-load discharge mode according to a discharge fitting formula; Step S025: Calculate and obtain the second reference voltage corresponding to the i-th SOC value in the charging mode according to the charging fitting formula, where 1 <i<m; Step S026: First, set the current operating mode of the small electronic device to the loaded discharge mode. When the voltage of the battery in the small electronic device drops to the first reference voltage, switch the current operating mode of the small electronic device to the charging mode, and record the SOC maintenance time required for the voltage of the battery in the small electronic device to rise from the first reference voltage to the second reference voltage.

[0052] Specifically, in step S021, the average nominal capacity is divided into m equal parts to obtain m+1 SOC values. Taking m=50 as an example, 51 SOC values can be obtained, namely SOC=[0%, 2%, 4%, 6%, ..., 100%]. In this embodiment, m=50 is used as an example for description, but the value of m is not limited to this.

[0053] In step S022 , in the charging mode, the voltage value corresponding to each SOC value is obtained to establish a voltage-SOC parameter table corresponding to the charging mode.

[0054] voltage = [3200, 3300, ..., 4000] (unit: mV); SOC=[0%, 2%, ..., 100%].

[0055] In step S023 , in the on-load discharge mode, the voltage value corresponding to each SOC value is obtained to establish a voltage-SOC parameter table corresponding to the on-load discharge mode.

[0056] The MATLAB Curve Fitting toolbox is used to perform polynomial curve fitting on 51 pairs of voltage-SOC data points in the charging mode, and the mathematical relationship between the SOC value and the voltage value is obtained, that is, the charging fitting formula. Taking the charging fitting formula in the charging mode as an example: y=1356.83158283*x^3–14683.84948891*x^2 + 52951.03320385*x–63619.78476642, where x is the voltage and y is the SOC value.

[0057] The MATLAB Curve Fitting toolbox was used to perform polynomial curve fitting on 51 pairs of voltage-SOC data points in the loaded discharge mode to obtain the mathematical relationship between the SOC value and the voltage value, namely the discharge fitting formula.

[0058] In step S024 , a first reference voltage V4 corresponding to the i-th SOC value in the loaded discharge mode is obtained by calculation according to a discharge fitting formula.

[0059] In step S025, the second reference voltage V5 corresponding to the i-th SOC value in the charging mode is calculated according to the charging fitting formula, where 1 <i<m。

[0060] The first reference voltage V4 and the second reference voltage V5 serve as reference voltages for switching the operation mode.

[0061] In this embodiment, an extreme case can be considered. In the loaded discharge mode, the voltage corresponding to the i-th SOC value is the lowest, while in the charging mode, the voltage corresponding to the i-th SOC value is the highest. The i-th SOC value can be 50%, where i is 26. In the loaded discharge mode, the SOC value of 50% corresponds to the lowest voltage, which is the first reference voltage V4. In the charging mode, the SOC value of 50% corresponds to the highest voltage, which is the second reference voltage V5.

[0062] In step S026, after obtaining a first reference voltage V4 and a second reference voltage V5 based on an extreme case, the battery in the small electronic device begins to discharge under load. When the voltage of the battery in the small electronic device drops to the first reference voltage V4, the current operating mode of the small electronic device is immediately switched to the charging mode. Voltage changes are monitored in real time, and the SOC holding time t required for the voltage to gradually increase from the first reference voltage V4 to the second reference voltage V5 is recorded. The SOC holding time is the time during which the SOC value remains unchanged after the operating mode is switched.

[0063] In this embodiment, the SOC value is 50% in the loaded discharge mode, and its corresponding first reference voltage V4 is the lowest. In the charging mode, the SOC value is 50%, and its corresponding second reference voltage V5 is the highest. Therefore, the SOC holding time t obtained based on the first reference voltage V4 and the second reference voltage V5 is the longest. It is ensured that after this SOC holding time t, no matter how the three operating modes are switched, the SOC value has been stabilized, avoiding SOC value jumps due to voltage fluctuations.

[0064] See also Figure 3 A flowchart of a method for estimating the battery SOC of a small electronic device according to an embodiment of the present application is shown. The method for estimating the battery SOC of a small electronic device provided by an embodiment of the present application includes: S21: Determine whether the current operating mode of the small electronic device is a charging mode, an unloaded discharge mode, or a loaded discharge mode; S22: Acquire a voltage-SOC parameter table corresponding to the current operating mode according to the current operating mode; S23: collecting a voltage signal of a battery in the small electronic device in real time; S24: Determine whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode; if so, correct the SOC value; if not, calculate the SOC value using a linear interpolation formula; and S25: Setting a corresponding gear position flag according to the SOC value.

[0065] Specifically, in step S21 , it is determined whether the current operation mode of the small electronic device is the charging mode, the off-load discharge mode, or the on-load discharge mode.

[0066] In step S22, after determining the current operating mode of the small electronic device, the voltage-SOC parameter table corresponding to the current operating mode is obtained according to the current operating mode, that is, when the current operating mode of the small electronic device is the charging mode, the voltage-SOC parameter table corresponding to the charging mode is obtained; when the current operating mode of the small electronic device is the no-load discharge mode, the voltage-SOC parameter table corresponding to the no-load discharge mode is obtained; when the current operating mode of the small electronic device is the loaded discharge mode, the voltage-SOC parameter table corresponding to the loaded discharge mode is obtained.

[0067] In step S23, a voltage sensor is used to collect a voltage signal of a battery in the small electronic device in real time.

[0068] In step S24, a determination is made as to whether the voltage signal exceeds the voltage boundary value in the voltage-SOC parameter table corresponding to the current operating mode. If the current operating mode is charging mode, the determination is made as to whether the voltage signal exceeds the charge cutoff voltage V1. If the current operating mode is off-load discharge mode, the determination is made as to whether the voltage signal is below the off-load cutoff voltage V2. If the current operating mode is on-load discharge mode, the determination is made as to whether the voltage signal is below the on-load cutoff voltage V3.

[0069] The battery management system in small electronic devices typically automatically manages the SOC value. When the current operating mode is charging mode, the voltage signal exceeds the charge cutoff voltage V1, and the battery management system in the small electronic device corrects the SOC value to 100%. This charge cutoff voltage V1 can float upward by a preset voltage value, which can be 10mV or 20mV, to ensure more complete charging. When the current operating mode is off-load discharge mode, the voltage signal falls below the off-load cutoff voltage V2, and the battery management system in the small electronic device corrects the SOC value to 0%. This off-load cutoff voltage V2 can float downward by a preset voltage value, which can be 10mV or 20mV, to ensure more complete discharge. When the current operating mode is on-load discharge mode, the voltage signal falls below the on-load cutoff voltage V3, and the battery management system in the small electronic device corrects the SOC value to 0%. This on-load cutoff voltage V3 can float downward by a preset voltage value, which can be 10mV or 20mV, to ensure more complete discharge.

[0070] When the current operating mode of the small electronic device is the charging mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the charging mode, and the SOC estimation value is obtained in real time through a linear interpolation formula.

[0071] When the current operating mode of the small electronic device is the no-load discharge mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the no-load discharge mode, and the SOC estimation value is obtained in real time by linear interpolation formula calculation.

[0072] When the current operating mode of the small electronic device is the on-load discharge mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the on-load discharge mode, and the SOC estimation value is obtained in real time through linear interpolation formula calculation.

[0073] In step S25, a corresponding gear position flag is set according to the real-time SOC value. In this embodiment, the gear position flag can be divided into 6 gears, such as 0, 25, 50, 75, 90 and 100, but is not limited thereto and can be set according to needs.

[0074] Furthermore, in step S24, determining whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode, and if so, correcting the SOC value, including: When the voltage signal is higher than the voltage boundary value of the voltage-SOC parameter table corresponding to the charging mode, the corrected SOC value is 100%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the no-load discharge mode, the corrected SOC value is 0%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the loaded discharge mode, the corrected SOC value is 0%.

[0075] Specifically, when the current operating mode of the small electronic device is the charging mode, the voltage signal is higher than the voltage boundary value of the voltage-SOC parameter table corresponding to the charging mode (that is, the charging cut-off voltage V1), the battery management system in the small electronic device will correct the SOC value to 100% to achieve full charge correction, and perform a full charge judgment action to ensure the normal operation of the battery management system.

[0076] When the current operating mode of the small electronic device is the no-load discharge mode, the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the no-load discharge mode (i.e., the no-load cut-off voltage V2), the battery management system in the small electronic device will perform an empty discharge correction action and correct the SOC value to 0% to achieve full discharge correction.

[0077] When the current operating mode of the small electronic device is the loaded discharge mode, the voltage signal is lower than the voltage boundary value (i.e., the loaded cut-off voltage V3) of the voltage-SOC parameter table corresponding to the loaded discharge mode, and the battery management system in the small electronic device will perform an empty discharge correction action and correct the SOC value to 0% to achieve full discharge correction.

[0078] Furthermore, when it is detected that the battery in the small electronic device has reached full charge, the battery management system in the small electronic device will directly correct the SOC value to 100%; when it is detected that the battery in the small electronic device has reached full discharge conditions, the battery management system in the small electronic device will directly correct the SOC value to 0%.

[0079] Furthermore, if the answer is no in step S23, the SOC value is calculated by a linear interpolation formula, including: When the voltage signal (i.e., the currently collected voltage signal) is within the voltage range of the voltage-SOC parameter table corresponding to the current operating mode, the SOC value is calculated using a linear interpolation formula. The linear interpolation formula is: , Wherein, when the current operation mode of the small electronic device is the charging mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage signal; When the current operating mode of the small electronic device is the no-load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage signal; When the current operating mode of the small electronic device is the load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage signal.

[0080] Specifically, when the current operating mode of the small electronic device is the charging mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the charging mode, and the SOC value is calculated by a linear interpolation formula. The linear interpolation formula is: , in, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage signal.

[0081] Taking the current operation mode of the small electronic device as the charging mode as an example, the voltage-SOC parameter table corresponding to the charging mode is: voltage = [3402, 3807, 3839, 3884, 3920, 3953, 3969, 3981, 3993, 4014, 4034] (unit: mV); SOC = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100].

[0082] Assuming that the current voltage signal is 3500mV, which is between the voltages 3402mV and 3807mV in the voltage-SOC parameter table, the SOC value is calculated using a linear interpolation formula.

[0083] When the current operating mode of the small electronic device is the no-load discharge mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the no-load discharge mode, and the SOC value is calculated by a linear interpolation formula. The linear interpolation formula is: , in, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage signal.

[0084] When the current operating mode of the small electronic device is the on-load discharge mode, the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the on-load discharge mode, and the SOC value is calculated by a linear interpolation formula. The linear interpolation formula is: , in, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage signal.

[0085] Furthermore, before step S21, the method further includes: S11: Determine whether the small electronic device is in an initialization state or a dynamic operation state.

[0086] Specifically, initialization can refer to the state when a small electronic device is first operated or powered on after being shut down. Dynamic operation state refers to the state during which a small electronic device is in operation.

[0087] When the small electronic device is in the initial state, the process proceeds to step S21 to perform real-time SOC value estimation.

[0088] When the small electronic device is in a dynamic operation state, it will also enter step S21 to perform dynamic real-time SOC value estimation.

[0089] Furthermore, when the small electronic device is in the dynamic operating state, it further includes: S12: Determine whether the current operating mode has changed. If so, keep the SOC value unchanged within the SOC holding time, and after exceeding the SOC holding time, enter step S22. If not, enter step S22.

[0090] Specifically, when the small electronic device is in the dynamic operating state, there will be an operating mode switching process. Determine whether the current operating mode has changed. If the operating mode has switched, then the SOC value needs to be kept unchanged within the SOC holding time t after the switch, and after exceeding the SOC holding time, enter step S22, that is, obtain the voltage-SOC parameter table corresponding to the current operating mode after the switch and the real-time collected voltage signal to estimate the SOC value in real time. If the operating mode has not switched, then directly enter step S22 to achieve dynamic real-time estimation of the SOC value, that is, obtain the voltage-SOC parameter table corresponding to the current operating mode and the real-time collected voltage signal to estimate the SOC value in real time according to the current operating mode. This embodiment can ensure that the SOC value is stable and does not jump when the operating mode is switched, which is conducive to avoiding the problem of SOC value jumps caused by voltage fluctuations.

[0091] The following example illustrates the switch from on-load discharge mode to charge mode. When a small electronic device switches from on-load discharge mode to charge mode, the SOC value in on-load discharge mode before the switch is maintained for the SOC hold time t. After the SOC hold time t, the SOC value is estimated in real time based on the voltage-SOC parameter table corresponding to the charge mode and the real-time collected voltage signal.

[0092] Furthermore, when the small electronic device is in the dynamic operation state, after step S23, the method further includes: S231: limiting a change direction of the SOC value according to the current operation mode; Wherein, when the current operating mode of the small electronic device is the charging mode, the SOC value is the larger value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operating mode of the small electronic device is the no-load discharge mode, the SOC value is the smaller value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operation mode of the small electronic device is the loaded discharge mode, the SOC value is the smaller value between the SOC value calculated at the current moment and the SOC value calculated at the previous moment.

[0093] Furthermore, setting a corresponding gear position flag according to the SOC value in step S25 includes: When the SOC value is ≤20%, the gear flag is set to 0; When 20%<the SOC value≤40%, the gear position flag is set to 25; When 40%<the SOC value≤60%, the gear position flag is set to 50; When 60%<the SOC value≤80%, the gear position flag is set to 75; When 80%<the SOC value≤100%, the gear flag is set to 100.

[0094] Furthermore, the method for estimating the state of charge of a battery of a small electronic device further includes: returning the SOC value and the gear position flag.

[0095] The approximate power status of the battery in the small electronic device can be intuitively understood through the feedback gear mark.

[0096] See also Figure 4 The figure shows a voltage-SOC fitting curve of a battery in a small electronic device in a charging mode according to an embodiment of the present application. Figure 5 shows a voltage-SOC fitting curve of a battery in a small electronic device in an embodiment of the present application in an unloaded discharge mode, and Figure 6 The voltage-SOC fitting curve of the battery in the small electronic device of the embodiment of the present application in the load discharge mode is shown, wherein Figure 4-Figure 5 In the figure, the horizontal axis represents voltage, the vertical axis represents SOC value, the solid line is the voltage-SOC curve, and the dots are the real-time estimated SOC value. The dots on the graph basically fit the voltage-SOC curve, indicating that the SOC value can be estimated based on the real-time collected voltage signal, and the voltage and SOC values show a linear relationship.

[0097] The battery state of charge estimation method for a small electronic device provided in the present application can estimate the SOC value in real time through the real-time collected voltage signal and the corresponding voltage-SOC parameter table, meet actual needs, and have high accuracy, low cost and low complexity. This estimation method is not affected by the current signal and is suitable for systems that do not have complex sensors, which helps to reduce costs. In addition, this estimation method can ensure that users can quickly and intuitively understand the approximate state of charge of the battery, while meeting the strict restrictions on hardware costs and computing resources of the battery management system in small electronic devices. When the current operating mode changes, the SOC value is kept unchanged within the SOC holding time, which can effectively ensure that the operating mode switching is relatively smooth, so that the SOC value is stable and does not jump, and effectively avoid the problem of SOC value jumping due to voltage fluctuations.

[0098] Although the embodiments of the present application and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

[0099] Furthermore, the scope of this application is not limited to the particular embodiments of the processes, machines, manufactures, compositions of matter, means, methods, and steps described in this specification. Those skilled in the art will readily appreciate from the disclosure of this application that, in accordance with this application, currently existing or later developed processes, machines, manufactures, compositions of matter, means, methods, or steps may be utilized that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein. Accordingly, it is intended that the appended claims include within their scope such processes, machines, manufactures, compositions of matter, means, methods, or steps.

Claims

1. A method for estimating the state of charge of a battery of a small electronic device, characterized in that: include: S21: Determine whether the current operating mode of the small electronic device is a charging mode, an unloaded discharge mode, or a loaded discharge mode; S22: Acquire a voltage-SOC parameter table corresponding to the current operating mode according to the current operating mode; S23: collecting a voltage signal of a battery in the small electronic device in real time; S24: Determine whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode; if so, correct the SOC value; if not, calculate the SOC value using a linear interpolation formula; and S25: Setting a corresponding gear position flag according to the SOC value.

2. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: The step S24 of determining whether the voltage signal exceeds the voltage boundary value of the voltage-SOC parameter table corresponding to the current operating mode, and if so, correcting the SOC value, includes: When the voltage signal is higher than the voltage boundary value of the voltage-SOC parameter table corresponding to the charging mode, the corrected SOC value is 100%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the no-load discharge mode, the corrected SOC value is 0%; When the voltage signal is lower than the voltage boundary value of the voltage-SOC parameter table corresponding to the loaded discharge mode, the corrected SOC value is 0%.

3. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: If not in step S23, the SOC value is calculated by a linear interpolation formula, including: When the voltage signal is within the voltage range of the voltage-SOC parameter table corresponding to the current operating mode, the SOC value is calculated using a linear interpolation formula. The linear interpolation formula is: , Wherein, when the current operation mode of the small electronic device is the charging mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the charging mode, is the voltage signal; When the current operating mode of the small electronic device is the no-load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the no-load discharge mode, is the voltage signal; When the current operating mode of the small electronic device is the load discharge mode, is the SOC lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the SOC upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage upper limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage lower limit value of the voltage-SOC parameter table corresponding to the on-load discharge mode, is the voltage signal.

4. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: Before step S21, the method further includes: S11: Determine whether the small electronic device is in an initialization state or a dynamic operation state.

5. The method for estimating the state of charge of a battery of a small electronic device according to claim 4, wherein: When the small electronic device is in the dynamic operation state, the method further includes: S231: limiting a change direction of the SOC value according to the current operating mode; Wherein, when the current operating mode of the small electronic device is the charging mode, the SOC value is the larger value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operating mode of the small electronic device is the no-load discharge mode, the SOC value is the smaller value of the SOC value calculated at the current moment and the SOC value calculated at the previous moment; When the current operation mode of the small electronic device is the loaded discharge mode, the SOC value is the smaller value between the SOC value calculated at the current moment and the SOC value calculated at the previous moment.

6. The method for estimating the state of charge of a battery of a small electronic device according to claim 4, wherein: When the small electronic device is in the dynamic operating state, the device further includes: S12: Determine whether the current operating mode has changed. If so, keep the SOC value unchanged within the SOC holding time, and after exceeding the SOC holding time, enter step S22. If not, enter step S22.

7. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: Setting the corresponding gear position flag according to the SOC value in step S25 includes: When the SOC value is ≤20%, the gear flag is set to 0; When 20%<the SOC value≤40%, the gear position flag is set to 25; When 40%<the SOC value≤60%, the gear position flag is set to 50; When 60%<the SOC value≤80%, the gear position flag is set to 75; When 80%<the SOC value≤100%, the gear flag is set to 100.

8. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: Also includes: Return the SOC value and the gear position flag.

9. The method for estimating the state of charge of a battery of a small electronic device according to claim 1, wherein: Before step S21, the following steps are also included: S01: Perform charging test and discharging test on the small electronic device in charging mode, no-load discharge mode and loaded discharge mode respectively, and establish a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the no-load discharge mode and a voltage-SOC parameter table corresponding to the loaded discharge mode respectively.

10. The method for estimating the state of charge of a battery of a small electronic device according to claim 9, wherein: Step S01 performs charging test and discharging test on the small electronic device in charging mode, off-load discharge mode and on-load discharge mode, respectively, and establishes a voltage-SOC parameter table corresponding to the charging mode, a voltage-SOC parameter table corresponding to the off-load discharge mode, and a voltage-SOC parameter table corresponding to the on-load discharge mode, respectively, including: respectively obtaining a charging nominal capacity, a first discharging nominal capacity, and a second discharging nominal capacity; Averaging the charging nominal capacity, the first discharging nominal capacity, and the second discharging nominal capacity to obtain an average nominal capacity; Dividing the average nominal capacity into n equal parts to obtain n+1 SOC values; Obtaining voltage values corresponding to the n+1 SOC values in the charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Obtaining voltage values corresponding to the n+1 SOC values in the no-load discharge mode to establish a voltage-SOC parameter table corresponding to the no-load discharge mode; The voltage values corresponding to the n+1 SOC values in the on-load discharge mode are obtained to establish a voltage-SOC parameter table corresponding to the on-load discharge mode.

11. The method for estimating the state of charge of a battery of a small electronic device according to claim 10, wherein: Before step S21, the following steps are also included: S02: Obtaining a first reference voltage in the on-load discharge mode and a second reference voltage in the charging mode; When the current operation mode of the small electronic device changes, the SOC maintenance time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage is recorded.

12. The method for estimating the state of charge of a battery of a small electronic device according to claim 11, wherein: Obtaining the first reference voltage in the loaded discharge mode and the second reference voltage in the charging mode in step S02 includes: Dividing the average nominal capacity into m equal parts to obtain m+1 SOC values; Obtaining voltage values corresponding to the m+1 SOC values in a charging mode to establish a voltage-SOC parameter table corresponding to the charging mode; Obtaining voltage values corresponding to the m+1 SOC values in the on-load discharge mode to establish a voltage-SOC parameter table corresponding to the on-load discharge mode; Calculate and obtain a first reference voltage corresponding to the i-th SOC value in the on-load discharge mode according to a discharge fitting formula; The second reference voltage corresponding to the i-th SOC value in the charging mode is calculated according to the charging fitting formula, where 1 <i<m; In step S02, when the current operating mode of the small electronic device changes, recording the SOC holding time required for the voltage of the battery in the small electronic device to change from the first reference voltage to the second reference voltage includes: First, the current operating mode of the small electronic device is set to the loaded discharge mode. When the voltage of the battery in the small electronic device drops to the first reference voltage, the current operating mode of the small electronic device is switched to the charging mode, and the SOC maintenance time required for the voltage of the battery in the small electronic device to rise from the first reference voltage to the second reference voltage is recorded.

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