A power battery full life cycle BMS power correction method

Abstract

This invention relates to the field of battery management technology and discloses a power correction method for a battery management system (BMS) throughout the entire life cycle of a power battery. The method includes: S1, calibrating the battery capacity C0 at 25℃±2℃, adjusting the State of Charge (SOC) based on C0, and testing the discharge Open Voltage (OCV) after resting to thermal equilibrium; S2, calculating the discharge / charge DCR of each SOC point through charge-discharge tests under the same temperature and capacity reference, forming an array and writing it into the BMS, with untested points interpolated using a 0.1% SOC step size; S3, when the vehicle is running and the trigger condition is met, obtaining OCV0 by querying the SOC-OCV curve and obtaining the voltage U1 at the end of X seconds, and calculating the DC internal resistance DCR at this time. SOCt This leads to the determination of the correction factor K, which in turn calculates the final allowable power value from the lookup table. This invention compares the initial DCR with the real-time DCR and dynamically adjusts the power using the correction factor K, thus correcting the battery power in real time. Compared to traditional lookup table correction methods, this provides a more accurate estimate of the usable power.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and specifically to a power battery BMS power correction method throughout the entire life cycle of a power battery. Background Technology

[0002] As the core power component of new energy vehicles, the power battery directly determines the vehicle's acceleration performance and energy recovery efficiency, and these performance indicators are highly dependent on the battery's actual output power. As the battery gradually ages during use, its power performance will irreversibly decline. At this time, the battery management system (BMS) must appropriately limit the output power according to the degree of aging to prevent battery undervoltage or overvoltage faults, thereby ensuring the safe operation of the system.

[0003] Currently, in engineering practice, the pre-defined State of Health (SOH) - power correction coefficient lookup table method is commonly used to implement this limiting strategy. This involves offline calibration of a fixed aging coefficient, interpolating the power limit based on the current SOH throughout the battery's entire lifespan. However, this static lookup method ignores the diversity of battery aging paths, as actual aging characteristics are closely related to the battery's operating conditions (such as temperature, charge / discharge rate, and state of charge window). Under different operating conditions, the evolution of aging mechanisms such as internal resistance growth and active material loss varies, resulting in the same SOH value potentially corresponding to drastically different power output capabilities.

[0004] Therefore, the lookup table method based on fixed coefficients cannot reflect the battery's current true power boundary in real time and accurately. This can easily lead to premature limitation, wasting battery performance, or insufficient limitation, inducing voltage abnormalities, which in turn affects the vehicle's power, economy, and service life. Summary of the Invention

[0005] The present invention aims to provide a power battery BMS power correction method for the entire life cycle of a power battery, and to solve the problem that the existing technology cannot accurately and timely correct the battery power.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a power battery BMS power correction method throughout its entire life cycle, comprising the following steps: S1, Measure the SOC-OCV curve at room temperature: Calibrate the battery capacity C0 at 25℃±2℃, adjust the SOC based on C0, and test the discharge OCV after letting it stand until thermal equilibrium is reached. S2, Construct SOC-DCR MAP: Under the same temperature and capacity reference, calculate the discharge / charge DCR of each SOC point through I charge and discharge test, form an array and write it into BMS, and interpolate the untested points with a step size of 0.1% SOC. S3, Dynamic Correction Triggered by Operating Conditions: When the vehicle is running, when the current I... opWhen the concentration reaches I±10%, the duration t≥2s, and the temperature reaches 25℃±2℃, it is detected by BMS. SOC Find OCV0 from the SOC-OCV curve, obtain the voltage U1 at the end of X seconds, and calculate the DC internal resistance DCR at this time. SOCt Then, the correction coefficient K is obtained, and the final allowable lookup table power value is calculated.

[0007] The principles and advantages of this scheme are: Traditional methods use State of Harmony (SOH) as the sole basis for power correction. However, SOH is essentially a comprehensive indicator and cannot reflect changes in key parameters such as internal resistance in real time. For example, batteries with the same SOH may have significantly different internal resistances at different temperatures and SOCs, resulting in drastically different power capabilities. This mismatch between "static preset" and "dynamic operating conditions" forms a core technical contradiction: limiting power with a conservative fixed coefficient sacrifices the actual usable performance of the battery; setting the coefficient according to ideal conditions may lead to overvoltage or undervoltage faults due to untimely detection of internal resistance increases. It is impossible to simultaneously meet the dual requirements of "precise limiting" and "dynamic adaptation," ultimately making it difficult to achieve accurate power control throughout the entire life cycle.

[0008] In existing technologies, the power limitation of power batteries adopts a lookup table method based on a pre-set State of Health (SOH) and power correction coefficient. The fundamental problem with this method is that it fails to recognize the strong correlation between battery aging characteristics and actual operating conditions. The degradation of battery power performance is not only related to the macroscopic state of health (SOH, such as capacity decay), but also directly related to microscopic internal resistance (especially DC internal resistance DCR), temperature, charge and discharge history, and other dynamic operating conditions.

[0009] The innovation of this solution lies in breaking through traditional understanding and recognizing the strong correlation between battery aging characteristics and actual operating conditions. Therefore, a dynamic correction mechanism is constructed by directly monitoring the DC internal resistance (DCR), which is strongly correlated with power output. By measuring the SOC-OCV curve relationship and SOC-DCR MAP of individual battery cells under standard conditions through S1 and S2, an internal resistance benchmark for the new battery state is established. Subsequently, during vehicle operation, when the operating conditions meet the triggering conditions, the open-circuit voltage corresponding to the current SOC and the terminal voltage after continuous discharge / charge are collected in real time to calculate the real-time internal resistance. Finally, the initial internal resistance is correlated with the real-time internal resistance through a correction coefficient, dynamically adjusting the allowable power in the power map. Essentially, this process replaces "SOH static lookup table" with "real-time internal resistance comparison," allowing power correction to directly anchor to the core parameter affecting power (internal resistance), rather than indirect health indicators.

[0010] This solution resolves the inherent contradiction between "precision" and "adaptability" inherent in traditional methods. It aims to ensure that power limiting accurately reflects the battery's current state (avoiding voltage anomalies caused by aging) while adapting to changes in internal resistance under varying operating conditions throughout the battery's lifespan (e.g., the impact of temperature, SOC, and charge / discharge history on DCR). By using the initial DCR as a baseline and real-time DCR as state feedback, the correction coefficient K dynamically quantifies the degree of aging. This avoids the "one-size-fits-all" problem of fixed coefficients and ensures control stability through interval time and a non-decreasing K value mechanism. It achieves precise power limiting throughout the entire battery lifespan: when battery aging increases internal resistance, the K value decreases, reducing the allowable power and preventing overvoltage / undervoltage faults; conversely, when operating conditions are stable and internal resistance remains relatively unchanged, the K value remains stable, ensuring power utilization efficiency. This dynamic adjustment mechanism solves the technical problem of traditional lookup table methods, which "cannot accurately limit power based on actual conditions," and achieves a balance between safety and performance, enabling efficient and safe management of the power battery throughout its entire lifespan. Attached Figure Description

[0011] Figure 1 This is a schematic flowchart of a power battery BMS power correction method for the entire life cycle of a power battery according to the present invention. Detailed Implementation

[0012] The following detailed description illustrates the specific implementation method: This embodiment presents a power battery full life cycle BMS power correction method. By measuring the battery's SOC-OCV and SOC-DCR MAP at 25℃±2℃ and writing them into the BMS as parameters, when the vehicle is running, under the condition that the discharge or charging current reaches I±10%, the duration is ≥2s, and the temperature is 25℃±2℃, the initial voltage is obtained by looking up the OCV through the BMS and the real-time DCR is calculated by combining it with the test end voltage. Then, the correction coefficient K is obtained to correct the power Map. At the same time, the correction interval is set to avoid repeated correction, so as to accurately limit the power according to the actual operating conditions of the battery.

[0013] A power battery BMS power correction method is provided throughout the entire life cycle of a power battery, as shown in the attached figure. Figure 1 As shown, it includes the following steps: S1, Measure SOC-OCV at room temperature: Calibrate the battery capacity C0 at 25℃±2℃, adjust the SOC based on C0, and test the discharge OCV after letting it stand until thermal equilibrium is reached.

[0014] This embodiment includes the following sub-steps: S1.1, Calibration reference capacity C0: The battery is charged and discharged under an environment of 25℃±2℃ to determine its standard capacity C0, which serves as the reference for subsequent SOC calculation.

[0015] S1.2, Adjust SOC and allow for thermal equilibrium: Using C0 as a reference, adjust the battery's state of charge (SOC) by discharging. In this embodiment, after each adjustment, the battery is allowed to rest in an environment of 25℃±2℃ until thermal equilibrium is reached, i.e., the battery temperature is stable, thus avoiding the influence of temperature fluctuations on voltage testing.

[0016] S1.3, Test Discharge OCV: After thermal equilibrium is reached, measure the open circuit voltage (OCV) of the battery, which is the voltage value of the battery under no-load conditions.

[0017] S1.4 Repeated multi-SOC point test: Repeat the above S1.2 and S1.3 processes according to the set SOC step size to cover the entire SOC range, such as 0%~100%.

[0018] In this embodiment, preferably, the SOC step size is 5%. The smaller the step size, the denser the test points, and the higher the accuracy of the SOC-OCV curve, but the test efficiency is reduced. A step size of 5% is the preferred value that balances accuracy and efficiency.

[0019] This yields open-circuit voltage data under different SOCs, forming SOC-OCV relationship curves or mapping tables.

[0020] S2, Construct SOC-DCR MAP: Under the same temperature and capacity reference, calculate the discharge / charge DCR of each SOC point through I charge-discharge test, form an array and write it into BMS, and interpolate the untested points with a step size of 0.1% SOC.

[0021] The battery capacity C0 is calibrated at 25℃±2℃. Using C0 as the capacity benchmark, the state of charge (SOC) of the battery is adjusted by discharging at 25℃±2℃. After each adjustment, the battery is left to rest at 25℃±2℃ until thermal equilibrium is reached to ensure temperature stability.

[0022] After thermal equilibrium is reached, a current (discharging or charging) of I=0.33C is applied for a duration t to simulate the medium load conditions in actual vehicle operation. This makes the DCR data closer to real-world usage scenarios, and the set duration ensures that the battery's internal resistance is fully reflected. Typically, according to testing standards, t can be set to 30s (the internal resistance data for the corresponding number of seconds can be calculated by extracting the voltage from 2s to the end of 30s). The open-circuit voltage (OCV) before the test and the voltage U at the end of the test are recorded. The ratio of the difference between the two to the current is the DCR, which reflects the battery's internal resistance characteristics at a specific SOC.

[0023] The SOC step size is adjusted to be consistent with the OCV test step size to ensure the correspondence of SOC points, balancing test accuracy and efficiency. The discharge DCR and charge DCR of each SOC point are calculated according to formula (1), and this process is repeated until all SOC points are tested. In this embodiment, formula (1) can be expressed as: ; (1) In the formula, The discharge DCR measured at the i-th SOC point; The charging DCR measured at the i-th SOC point; Let be the open-circuit voltage of the i-th SOC point; Let be the voltage at the i-th SOC point; It represents electric current.

[0024] The DCR values ​​of all SOC points are compiled into discharge values. and charging An array, denoted as an array, can be represented as: ; (2) The DCR values ​​of untested SOC points are written into the BMS software as parameters. The software interpolates the DCR values ​​in steps of 0.1% of SOC to complete the data, ensuring that the SOC-DCR MAP covers the entire SOC range and improving the accuracy of BMS queries. This forms an SOC-DCR MAP relation array containing discharge DCR and charge DCR data under different SOCs.

[0025] S3, Dynamic Correction Triggered by Operating Conditions: When the vehicle is running, when the current I... op When the concentration reaches I±10%, the duration t≥2s, and the temperature reaches 25℃±2℃, it is detected by BMS. SOC From the SOC-OCV curve, obtain OCV0, then obtain the voltage U1 at the end of X seconds, and calculate the DC internal resistance DCR at this time. SOCt Thus, the correction coefficient K is derived.

[0026] During vehicle operation, the discharge or charging current I is monitored in real time. op The duration t and temperature are used to trigger a correction when the following conditions are met: Current condition: I op The current reaches ±10% of the reference current I. In this embodiment, I is the current when testing DCR in S2, i.e., I=0.33C, to ensure the accuracy of DCR calculation. Time condition: The current duration t≥2s to ensure current stability and avoid DCR calculation errors caused by instantaneous fluctuations; Temperature conditions: The battery temperature reaches 25℃±2℃, consistent with the test environment of S1 and S2, to eliminate the influence of temperature on internal resistance and ensure data comparability.

[0027] Obtain the current BMS in real time through BMS SOC (Real-time state of charge), query the SOC-OCV curve relationship obtained in S1, obtain the corresponding open-circuit voltage OCV0, and record the real-time voltage U1 after X seconds.

[0028] The real-time DC internal resistance can be calculated as follows: (3) The pre-stored SOC-DCR MAP array in S2 is called to obtain the initial DCR value under the current SOC, i.e. or The correction coefficient K is calculated according to equation (4) to reflect the difference between the current internal resistance of the battery and its initial state, and is used to dynamically adjust the power limit. It can be expressed as follows: (Discharge) (Charging); (4) Adjust the power lookup table value in the BMS according to the correction factor K, i.e., allowable lookup table power value = K × P 查表 P 查表 The standard power value is from the original power map.

[0029] Set a correction interval, such as not repeating corrections within 7 days, to avoid frequent triggering that could cause power fluctuations. As operating time increases, ensure that the K value does not decrease with operating time; that is, as the battery ages and its internal resistance increases, the K value will not decrease, preventing the relaxation of power limits from causing safety risks.

[0030] The corrected allowable power limit value is obtained, which is the power limit value dynamically adjusted by the BMS based on the current aging state of the battery. It adjusts the power according to the actual internal resistance of the battery to prevent undervoltage and overvoltage faults caused by overcharging / overdischarging, thus extending battery life. This replaces the traditional lookup method with a fixed SOH-power correction coefficient, achieving precise power limiting throughout the entire battery life through real-time DCR comparison. This avoids control deviations caused by the strong correlation between battery aging characteristics and operating conditions, maximizing battery power utilization within a safe range, balancing acceleration performance and energy recovery efficiency, and improving user experience.

[0031] The following is an illustration using a specific implementation case: Taking a 160Ah lithium iron phosphate single cell as an example, the discharge DCR data within 30 seconds at a 0.33C current measured under different SOCs using the S2 test method are shown in Table 1. Table 125℃ SOC-DCR

[0032] These data serve as the internal resistance reference for the battery in its "new state" and are pre-stored in the SOC-DCR MAP array of the BMS.

[0033] When the vehicle is running, the correction is triggered under the following conditions: temperature is 25℃; SOC is 50%; current is 0.33C; duration is 30s. The real-time internal resistance is calculated according to equation (3), and the result is obtained. This value reflects the actual internal resistance of the battery after aging. It is larger than the initial value (0.66 milliohms), indicating that the battery performance has deteriorated.

[0034] The correction coefficient K is calculated according to equation (4). Final BMS allowable power = K × P 查表 This means that the standard power value in the original power map needs to be multiplied by 0.88, reducing the power limit by 12%.

[0035] This embodiment fully demonstrates the "dynamic power correction based on internal resistance changes" process using actual data, proving that the strategy can be implemented. Compared to the traditional lookup method with a fixed SOH-power coefficient, in this example, the battery's internal resistance increases due to aging. The power is dynamically reduced by using the K value, avoiding the overvoltage / undervoltage risks caused by "limiting by a fixed coefficient," thus solving the problem of not being able to accurately limit power based on actual conditions in traditional methods. After correction, the power is reduced by 12%, ensuring battery safety (avoiding abnormal voltage under high current) while making reasonable use of remaining performance after aging (without excessive power limitation), balancing safety and user experience.

[0036] In this embodiment, by comparing the initial DCR with the real-time DCR, the power is dynamically adjusted using a correction coefficient K, thus resolving the contradiction between accuracy and adaptability that cannot be balanced by the traditional SOH lookup table method. When the battery ages and its internal resistance increases, the value of K decreases, reducing the allowable power and preventing voltage anomalies; when the operating conditions are stable, the value of K remains stable to ensure power utilization efficiency, achieving a balance between battery safety and performance throughout its entire life cycle.

[0037] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A power battery BMS power correction method throughout its entire life cycle, characterized in that, Includes the following steps: S1, Measure the SOC-OCV curve at room temperature: Calibrate the battery capacity C0 at 25℃±2℃, adjust the SOC based on C0, and test the discharge OCV after letting it stand until thermal equilibrium is reached. S2, Construct SOC-DCR MAP: Under the same temperature and capacity reference, calculate the discharge / charge DCR of each SOC point through I charge and discharge test, form an array and write it into BMS, and interpolate the untested points with a step size of 0.1% SOC. S3, Dynamic Correction Triggered by Operating Conditions: When the vehicle is running, when the current I... op When the concentration reaches I±10%, the duration t≥2s, and the temperature reaches 25℃±2℃, it is detected by BMS. SOC Obtain OCV0 from the SOC-OCV curve and get the voltage U1 at the end of X seconds. Calculate the DC internal resistance DCR at this time. SOCt Then, the correction coefficient K is obtained, and the final allowable lookup table power value is calculated.

2. The power battery full life cycle BMS power correction method according to claim 1, characterized in that, S1 includes the following sub-steps: S1.1, The battery is charged and discharged under an environment of 25℃±2℃ to determine its standard capacity C0; S1.2, with C0 as the reference, adjust the state of charge (SOC) of the battery by discharging. After each adjustment, let the battery rest in an environment of 25℃±2℃ until thermal equilibrium is reached. S1.3 After thermal equilibrium is reached, the open-circuit voltage OCV of the battery is measured, and the multi-SOC point test is repeated according to the set SOC step size until the entire SOC range is covered.

3. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 2, characterized in that: The SOC step size is 5%.

4. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 1, characterized in that: In S2, with a current duration t of I=0.33C, the discharge / charge DCR of each SOC point is calculated; and the open circuit voltage OCV before the test and the voltage U at the end of the test are recorded.

5. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 1, characterized in that: In S2, the step size of SOC is consistent with the step size of OCV test.

6. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 4, characterized in that: The discharge / charge DCR of each SOC point is expressed as follows: ； ； In the formula, The discharge DCR measured at the i-th SOC point; The charging DCR measured at the i-th SOC point; Let be the open-circuit voltage of the i-th SOC point; Let be the voltage at the i-th SOC point; It represents electric current.

7. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 6, characterized in that: The DCR values ​​of all SOC points were compiled into discharge values. and charging An array, denoted as an array, is represented as... ； 。 8. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 7, characterized in that: In S3, the DC internal resistance DCR SOCt Represented as 。 9. A power battery full life cycle BMS power correction method according to claim 8, characterized in that: In S3, the correction factor K is expressed as ； ； Adjust the power lookup table value in the BMS according to the correction factor K. Allowable lookup power value = K × P 查表 P 查表 The standard power value is from the original power map.

10. The power correction method for BMS throughout the entire life cycle of a power battery according to claim 1, characterized in that: It also includes setting the correction interval and making the K value non-decreasing.

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