SOC following correction method of emergency power supply lithium battery
Through the SOC follow-up correction method of the emergency power lithium battery, the current size is adjusted by using small current charging and discharging, and dynamically approximates the target SOC, solving the problem of large SOC error in the lithium battery in the prior art, achieving higher accuracy and system stability.
Patent Information
- Application Number
- CN202510460082.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-07-01
AI Technical Summary
The existing lithium battery SOC acquisition methods have large errors and are not accurate enough, especially in the process of charging and discharging of high currents, and the inaccuracy of the initial value affects subsequent estimation and cannot be dynamically adjusted, resulting in unstable lithium battery system.
The SOC follow-up correction method of emergency power lithium batteries is adopted. By obtaining the average voltage of a single cell without fluctuation, the current size is adjusted in combination with small current charging and discharge, dynamically approximates the target SOC, reducing errors, and improving accuracy and reliability.
The SOC calculation error range is reduced, the accuracy and reliability of lithium battery SOC is improved, the stability of the system is enhanced, and the stable operation of the lithium battery system is ensured.
Smart Images
Figure CN120233255A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium battery charging and discharging, and particularly to a method for correcting the SOC following of a lithium battery for an emergency power supply. Background Art
[0002] With the continuous development of lithium battery technology, lithium-ion batteries have been widely used in many fields such as electric vehicles, energy storage, emergency starting power supplies, and other portable electronics due to their high energy density, long cycle life, and other advantages.
[0003] During the use of a lithium battery, its state of charge is a very important indicator, that is, the ratio of the actual power that the lithium battery can provide under the current state to the power that can be provided under its rated capacity (fully charged state), which is represented by SOC (state of charge, the state of charge of the battery).
[0004] Through the SOC data value, the remaining power of the lithium battery in the current state can be known, which is convenient for the subsequent management and operation of the battery management system. Therefore, ensuring the timeliness, accuracy, and reliability of the SOC data is the top priority in the management of lithium batteries such as emergency power supplies.
[0005] Currently, the methods for obtaining the SOC of a lithium battery mainly include the SOC-OCV (open circuit voltage) look-up table method and the ampere-hour integration method during the charging and discharging process;
[0006] SOC-OCV look-up table method: Obtain the voltage-electricity relationship array through the SOC-OCV relationship curve of the lithium battery tested by the lithium battery manufacturer. By judging whether the real-time collected voltage (Value) is within the SOC-OCV and through the algorithm formula for dividing the OCV into intervals and summarizing, the calculation of the SOC value is completed. The SOC of the initial state of the lithium battery is generally calculated by this method;
[0007] Ampere-hour integration method: The ampere-hour integration method (Ampere-Hour Integration Method) is a widely used SOC estimation method in a lithium battery management system (BMS). This method estimates the remaining power (SOC) of the battery by cumulatively calculating the charging and discharging current and capacity of the battery on the basis of the initially obtained SOC, and combining with the rated capacity of the battery. Its basic principle is based on the law of conservation of charge, that is, the change in charge during the charging and discharging process of the battery is proportional to the change in SOC; The following are the detailed steps and formulas for calculating the SOC of a lithium battery by the ampere-hour integration method.
[0008] 1. Obtain the initial SOC
[0009] First, it is necessary to determine the initial state of the battery (the initial value of the SOC). The commonly used methods include:
[0010] A. Estimated by open circuit voltage (OCV) look-up table method;
[0011] B. Recorded by the depth of discharge (DoD) of the previous battery;
[0012] C. Manual input or estimation based on historical data;
[0013] Formula:
[0014] 2. Cumulative charge and discharge current
[0015] During the operation of the battery, the charge and discharge current (I) of the battery is measured in real time by a current sensor and integrated. The unit of current is ampere (A), and the unit of time is hour (h).
[0016] Formula:
[0017]
[0018] Among them, Q(t) is the cumulative electric quantity (Ah) from the initial moment to the current moment;
[0019] 3. Calculate the current SOC;
[0020] According to the cumulative electric quantity Q(t), combined with the rated capacity Crated of the battery, calculate the current SOC;
[0021] Formula:
[0022] However, in practical applications, these two methods still have the following technical problems and defects:
[0023] Disadvantages of the SOC-OCV look-up table method:
[0024] Different voltages correspond to different SOC data, but there are some problems with the look-up table method. The table data is not fine enough, and there is a large difference in SOC when the voltage difference is small, resulting in a certain error;
[0025] This method has a large error during high-current charge and discharge, because high-current charge and discharge will cause the relative increase and decrease of the cell voltage, thus unable to accurately reflect the actual cell charge in the static state. Therefore, this look-up table should be used as much as possible under static or low-current charge and discharge conditions.
[0026] Disadvantages of the ampere-hour integration method:
[0027] An accurate initial value is required: the accuracy of the initial SOC directly affects the accuracy of subsequent estimations;
[0028] The error accumulation remains unchanged: The measurement error of the current cumulative calculation will accumulate over time, and it cannot fully guarantee consistency with the lithium battery voltage, which may cause the SOC estimation to deviate from the true value;
[0029] Affected by temperature and aging: The battery capacity will change with temperature changes and aging, and the ampere-hour integration method cannot be dynamically adjusted.
[0030] Therefore, on the basis of these common methods, a method for correcting the SOC following of a lithium battery for an emergency power supply is designed to enrich the way of obtaining the SOC, so that various methods can complement each other and flexibly control the SOC calculation in different situations, which is of great significance for improving the accuracy and reliability of the lithium battery SOC and ensuring the stable operation of the lithium battery system. Summary of the Invention
[0031] The purpose of the present invention is to provide a method for correcting the SOC following of a lithium battery for an emergency power supply, which has the advantages of reducing the error range, improving the accuracy and reliability, and enhancing the system stability.
[0032] The above technical purpose of the present invention is achieved through the following technical solutions:
[0033] A method for correcting the SOC following of a lithium battery for an emergency power supply includes the following operating steps.
[0034] Step 1: Obtain the average voltage of the tabulated single-cell battery and the duration of the non-fluctuation of the average single-cell voltage.
[0035] When the duration of the non-fluctuation of the average single-cell voltage is 0, record the average voltage of the single-cell battery at the initial reference. At the same time, the target SOC is equal to the current SOC. When the target SOC value is not obtained, the target SOC is first assigned the current actual SOC.
[0036] When the duration of the non-fluctuation of the average single-cell voltage is within two minutes and the fluctuation of the average single-cell voltage exceeds 0.2V, that is, the voltage fluctuation is large, the duration of the non-fluctuation of the average single-cell voltage is cleared to 0, and the average single-cell voltage is re-obtained in the next cycle.
[0037] When the duration of the non-fluctuation of the average single-cell voltage exceeds two minutes, record the average voltage of the single-cell battery at this time, and at the same time clear the duration of the non-fluctuation of the average single-cell voltage to 0.
[0038] Step 2: The average voltage of the single-cell battery obtained when the duration of the non-fluctuation of the average single-cell voltage reaches two minutes is the SOC look-up table voltage, and the target SOC is obtained by looking up the SOC-OCV table with this SOC look-up table voltage.
[0039] If the difference between the target SOC and the current SOC exceeds 10%, then obtain the target SOC flag bit; clear the duration of the non-fluctuation of the average single-cell voltage to 0.
[0040] Step 3: The small - current charge - discharge situation continuously approaches the target SOC;
[0041] The dynamic adjustment of the small - current charge - discharge situation calculates the current magnitude and participates in the capacity calculation adjustment to continuously approach the target SOC.
[0042] The preferred solutions are as follows:
[0043] Preferably: In Step 3, the small - current charging current is below 5A, and when obtaining the target SOC flag bit;
[0044] If the current SOC is less than the target SOC, then the current charge capacity += current (1% SOC per minute);
[0045] If the current SOC is greater than the target SOC, then the current charge capacity -= (charging current * 0.5);
[0046] If the current SOC is equal to the target SOC, then clear the target SOC flag bit to 0.
[0047] Preferably: In Step 3, the small - current discharging current is below 5A, and when obtaining the target SOC flag bit;
[0048] If the current SOC is less than the target SOC, then the current charge capacity += current (1% SOC per minute);
[0049] If the current SOC is greater than the target SOC, then the current charge capacity += (discharging current * 0.5);
[0050] If the current SOC is equal to the target SOC, then clear the target SOC flag bit to 0.
[0051] Preferably: In Step 3, when the charging current is greater than 5A and the target SOC flag bit has not been obtained;
[0052] The current charge capacity -= the actual charging current.
[0053] Preferably: In Step 3, when the discharging current is greater than 5A and the target SOC flag bit has not been obtained;
[0054] The current charge capacity += the actual charging current.
[0055] In summary, the present invention has the following beneficial effects:
[0056] 1. Improve the accuracy and reliability. By the small - current average voltage following correction method, reduce the error range, ensure the relative accuracy of the true SOC of the lithium battery and its actual voltage and power, and ensure the accuracy and reliability of the SOC;
[0057] 2. Enhance system stability. The relatively accurate SOC provides stable and objective support for the power system in terms of energy storage and scheduling, ensuring the convenience of user use;
[0058] The present invention has the advantages of reducing the error range, thereby effectively improving the accuracy and reliability of the SOC of the lithium battery in the emergency power supply, and providing an important guarantee for the stable use of user products. Brief Description of the Drawings
[0059] Figure 1 is the working flowchart of the embodiment;
[0060] Figure 2 is the flowchart for obtaining the target SOC flag bit of the embodiment;
[0061] Figure 3 is the flowchart for continuously approaching the target SOC under the small current charge and discharge conditions of the embodiment. Detailed Embodiments
[0062] The present invention will be further described in detail below with reference to the accompanying drawings.
[0063] The SOC following correction method for the lithium battery of the emergency power supply, as Figures 1-3 shown, includes the following operation steps,
[0064] Step 1: Obtain the average voltage of the single cell for table lookup, and the duration of the non-fluctuation of the average voltage of the single cell;
[0065] The duration of the non-fluctuation of the average voltage of the single cell is 0. Record the average voltage of the single cell at the initial reference. At the same time, the target SOC is equal to the current SOC. When the target SOC value is not obtained, the target SOC is first assigned the current actual SOC;
[0066] When the duration of the non-fluctuation of the average voltage of the single cell is within two minutes and the fluctuation of the average voltage of the single cell exceeds 0.2V, that is, the voltage fluctuation is large, the duration of the non-fluctuation of the average voltage of the single cell is cleared to 0, and the average voltage of the single cell is re-obtained in the next cycle;
[0067] When the duration of the non-fluctuation of the average voltage of the single cell exceeds two minutes, record the average voltage of the single cell at this time, and at the same time clear the duration of the non-fluctuation of the average voltage of the single cell to 0;
[0068] Step 2: When the duration of the non-fluctuation of the average voltage of the single cell reaches two minutes, the average voltage of the single cell obtained is the SOC lookup voltage. The target SOC is obtained by looking up the SOC-OCV table with this SOC lookup voltage;
[0069] If the difference between the target SOC and the current SOC exceeds 10%, then obtain the target SOC flag bit; clear the duration of the non-fluctuation of the average voltage of the single cell;
[0070] Step 3: The small current charge and discharge situation continuously approaches the target SOC;
[0071] The dynamic adjustment of the small current charge and discharge situation calculates the current magnitude and participates in the capacity calculation adjustment to continuously approach the target SOC;
[0072] 1) When the small current charging current is below 5A, it is small current charging, and when obtaining the target SOC flag bit;
[0073] If the current SOC is less than the target SOC, then the current charge capacity += current (1% SOC per minute), that is, the current charge capacity increases and is adjusted at a rate of 1% SOC per minute;
[0074] If the current SOC is greater than the target SOC, then the current charge capacity -= (charging current * 0.5), that is, the current charge capacity decreases and is adjusted by 0.5 times the charging current;
[0075] If the current SOC is equal to the target SOC, then clear the target SOC flag bit to 0;
[0076] 2) When the small current discharge current is below 5A, it is small current discharge, and when obtaining the target SOC flag bit;
[0077] If the current SOC is less than the target SOC, then the current charge capacity += current (1% SOC per minute), that is, the current charge capacity increases and is adjusted at a rate of 1% SOC per minute;
[0078] If the current SOC is greater than the target SOC, then the current charge capacity += (discharge current * 0.5), that is, the current charge capacity decreases and is adjusted by 0.5 times the discharge current;
[0079] If the current SOC is equal to the target SOC, then clear the target SOC flag bit to 0;
[0080] 3) When the charging current is greater than 5A, it is large current charging, and when the target SOC flag bit has not been obtained;
[0081] The current charge capacity -= actual charging current, that is, the current charge capacity decreases, and the reduction amount is the actual charging current;
[0082] 4) When the discharge current is greater than 5A, it is large current discharge, and when the target SOC flag bit has not been obtained;
[0083] The current charge capacity += actual discharge current, that is, the current charge capacity increases, and the increase amount is the actual discharge current;
[0084] Step 4: Capacity statistics, calculate SOC using the formula;
[0085] The process of ampere-hour integration is to calculate the cumulative charge / discharge within a certain period of time. When the charge reaches 1 mAh, the used capacity is incremented / decremented by 1, and then the SOC is calculated based on the ratio of the current capacity to the rated capacity.
[0086] The calculation formula is as follows:
[0087] The charge / discharge amount accumulated this time = the charge / discharge amount accumulated + current (mA) * unit time (operation cycle 1 s). For details of the charge / discharge amount accumulated, see Step 3.
[0088] When the charge / discharge amount accumulated this time ≥ 1 mAh (= 1 mA * 60 * 60 s), the currently used capacity is incremented / decremented by 1.
[0089] SOC (percentage system) = currently used capacity * 100 / rated capacity.
[0090] The specific workflow for obtaining the target SOC flag bit is as follows:
[0091] S1. Detect the charge / discharge current.
[0092] S2. When the charge / discharge current is greater than 5 A, it is high-current charge / discharge. At this time, the target SOC flag bit is cleared to 0, and the continuous timing of the average voltage of the single-cell battery core without fluctuation is cleared to 0. Repeat S1.
[0093] S3. When the charge / discharge current does not exceed 5 A, it is low-current charge / discharge, and the target SOC flag bit is 0.
[0094] S4. When the continuous timing of the average voltage of the single-cell battery core without fluctuation reaches two minutes, the continuous timing of the average voltage of the single-cell battery core without fluctuation is 0, the obtained average voltage of the single-cell battery core is the SOC look-up table voltage, and the target SOC is first assigned the current actual SOC. Then enter S5.
[0095] When the continuous timing of the average voltage of the single-cell battery core without fluctuation reaches two minutes and the continuous timing of the average voltage of the single-cell battery core without fluctuation is between 0 and 2 minutes, enter S5.
[0096] S5. Within two minutes, when the continuous timing of the average voltage of the single-cell battery core without fluctuation is less than two minutes, continue timing.
[0097] If the fluctuation of the average voltage of the single cell exceeds 0.2 V beyond the base voltage, then the timing is cleared to 0 and S1 is repeated.
[0098] If the fluctuation of the average voltage of the single cell exceeds within 0.2 V of the base voltage, then repeat S4.
[0099] Within two minutes, when the continuous timing of the average voltage of the single-cell battery core without fluctuation exceeds two minutes, then
[0100] Record the average voltage of the single cell at this time, and clear the continuous timing time when the average voltage of the single cell does not fluctuate;
[0101] S6. The average voltage of the single cell obtained when the continuous timing of the non-fluctuating average voltage of the single cell reaches two minutes is the SOC look-up table voltage, and the target SOC is obtained by looking up the SOC-OCV look-up table with this SOC look-up table voltage;
[0102] S7. If the difference between the target SOC and the current SOC exceeds 10%, then obtain the target SOC flag bit and clear the continuous timing time of the non-fluctuating average voltage of the single cell.
[0103] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.
Claims
1. The SOC following correction method of the emergency power supply lithium battery is characterized by: The following steps are included: Step 1: Obtain the average voltage of the battery cell and the duration of time during which the average voltage of the single cell does not fluctuate; The average voltage of the single cell does not fluctuate and the continuous time is 0, and the average voltage of the single cell of the initial benchmark is recorded. At the same time, the target SOC is equal to the current SOC. When the target SOC value is not obtained, the target SOC is first assigned to the current actual SOC; The average voltage of a single cell does not fluctuate for two minutes. If the average voltage of a single cell fluctuates by more than 0.2V, that is, the voltage fluctuates greatly, the average voltage of a single cell does not fluctuate for two minutes, and the average voltage of a single cell is obtained again in the next cycle. If the average voltage of a single cell does not fluctuate for more than two minutes, the average voltage of the single cell at this time is recorded, and the average voltage of the single cell does not fluctuate for more than two minutes. Step 2: When the average voltage of the single cell does not fluctuate for two minutes, the average voltage of the single cell is obtained as the SOC table voltage, and the SOC table voltage is subtracted from the SOC-OCV table to obtain the target SOC; If the target SOC differs from the current SOC by more than 10%, the target SOC flag is obtained; The time when the average voltage of a single cell does not fluctuate is reset to 0; Step 3: The low current charge and discharge situation continues to approach the target SOC; The dynamic adjustment of small current charging and discharging conditions calculates the current size to participate in capacity calculation and adjustment to continuously approach the target SOC.
2. The SOC following correction method of the emergency power supply lithium battery according to claim 1 is characterized in that: In step 3, the low current charging current is below 5A, and the target SOC flag is obtained; If the current SOC is less than the target SOC, then the current charging capacity + = current (1% SOC per min); If the current SOC is greater than the target SOC, then the current charging capacity = (charging current * 0.5); If the current SOC is equal to the target SOC, the target SOC flag is cleared to 0.
3. The SOC following correction method of the emergency power supply lithium battery according to claim 2 is characterized in that: In step 3, the low current discharge current is below 5A, and the target SOC flag is obtained; If the current SOC is less than the target SOC, then the current charging capacity + = current (1% SOC per min); If the current SOC is greater than the target SOC, then the current charging capacity + = (discharging current * 0.5); If the current SOC is equal to the target SOC, the target SOC flag is cleared to 0.
4. The SOC following correction method of the emergency power supply lithium battery according to claim 2 is characterized in that: In step 3, when the charging current is greater than 5A and the target SOC flag is not obtained; This charging capacity - = actual charging current.
5. The SOC following correction method of the emergency power supply lithium battery according to claim 3 is characterized in that: In step 3, when the current discharge current is greater than 5A and the target SOC flag is not obtained; This charging capacity + = actual charging current.