Early warning method, program product and battery management system for a battery

Abstract

This invention relates to a warning method for batteries, comprising at least the following steps: S4: obtaining the rated intermediate capacity at an intermediate feature point of the battery; obtaining the calibrated total capacity of the battery; during charging, identifying the intermediate feature point of the battery, and calculating a first charging capacity corresponding to the intermediate feature point based on the rated intermediate capacity; S5: recording a second charging capacity from the intermediate feature point to a fully charged state, and calculating an estimated total capacity of the battery from the first charging capacity and the second charging capacity; S6: comparing the estimated total capacity with the calibrated total capacity, determining whether the battery is at risk based on the comparison result, and issuing a warning signal when a risk is determined to exist. The invention also relates to a corresponding computer program product and battery management system. These methods can detect abnormal aging risks of batteries in a timely and accurate manner without requiring frequent deep charge-discharge cycles.

Description

Technical Field

[0001] This invention relates to the technical field of batteries, and more particularly to a warning method for batteries. The invention also relates to a corresponding computer program product and a corresponding battery management system. Background Technology

[0002] With the rapid development of battery technology, lithium-ion batteries are widely used in electric vehicles. In actual battery use, aging means more than just capacity decay. For lithium-ion batteries, especially lithium iron phosphate batteries, when they reach an abnormal aging state, there are additional risks, such as lithium dendrite precipitation, which threatens battery safety. However, conventional capacity calibration methods are not only time-consuming but also ineffective in detecting this abnormal aging state. Summary of the Invention

[0003] Therefore, the object of this invention is to provide an improved early warning method for batteries, which can detect the risk of abnormal aging of batteries in a timely and accurate manner without the need for frequent deep charge and discharge cycles. The object of this invention also includes a corresponding computer program product and a corresponding battery management system.

[0004] According to a first aspect of the present invention, a warning method for a battery is provided, wherein the warning method includes at least the following steps: S1: Obtain the rated intermediate capacity at the intermediate feature point of the battery; S2: Obtain the total calibrated capacity of the battery; S3: During the charging process, the intermediate feature point of the battery is identified, and the first charging capacity corresponding to the intermediate feature point is calculated based on the rated intermediate capacity. S4: Record the second charging capacity from the intermediate feature point to the fully charged state, and calculate the estimated total capacity of the battery from the first charging capacity and the second charging capacity; S5: Compare the estimated total capacity with the calibrated total capacity, determine whether the battery is at risk based on the comparison result, and issue a warning signal when a risk is detected.

[0005] Within the framework of this invention, "intermediate feature point" should be understood as a feature point caused by the phase transition of the graphite negative electrode during battery charging. This feature point manifests as an inflection point in the plateau region on the charging curve or as a clear peak point on the differential voltage curve. During normal battery cycling, the structure of the graphite material of the negative electrode and its inherent phase transition sequence are very stable, ensuring that the number of lithium ions embedded in the graphite crystal structure remains essentially stable. Consequently, the charging capacity corresponding to the intermediate feature point also remains essentially constant. Therefore, the intermediate feature point can be considered as a capacity anchor point during normal cycling.

[0006] Compared to existing technologies, in the early warning method according to the present invention, during the charging process, an intermediate feature point of the battery is identified, and a first charging capacity corresponding to the intermediate feature point is calculated based on the rated intermediate capacity of that intermediate feature point. Then, a second charging capacity from the intermediate feature point to the fully charged state is recorded. An estimated total capacity is calculated from the first and second charging capacities. The estimated total capacity is compared with the pre-acquired calibrated total capacity. If there is a significant deviation between the estimated total capacity calculated based on the intermediate feature point and the calibrated total capacity, it indicates that a portion of the current is not used to embed lithium ions into the crystal structure of graphite, but instead directly reduces lithium ions to metallic lithium and accumulates on the negative electrode surface to form dendrites, causing damage to the negative electrode material to a certain extent. In this case, the intermediate feature point will shift and can no longer be used as a capacity anchor point. In this situation, it can be determined that the battery has a safety risk of abnormal aging and an early warning signal can be issued. Thus, the abnormal aging risk of the battery can be detected in a timely and accurate manner, thereby achieving a safety early warning without frequent deep charge and discharge cycles.

[0007] For example, when the ratio of the estimated total capacity to the calibrated total capacity is greater than a set threshold, the battery is determined to be at risk.

[0008] For example, when the ratio is greater than the set threshold, the anomaly count is incremented by one; when the anomaly count reaches a preset value, it is determined that the battery is at risk.

[0009] For example, in step S3, the first charging capacity is calculated based on the rated intermediate capacity and a correction factor, the correction factor being determined based on at least one of the following influencing factors: average charging current, initial state of charge, charging temperature, battery aging degree, and battery rated capacity.

[0010] For example, in step S1, the rated intermediate capacity is provided by the battery supplier and stored in the battery management system for the battery.

[0011] For example, in step S2, the total calibration capacity is obtained by performing an open-circuit voltage calibration cycle on the battery.

[0012] For example, in step S3, identifying the intermediate feature point of the battery includes the following steps: S31: Calculate the differential voltage SOC curve during the charging process; S32: Within a preset state of charge range, identify the peak point of the differential voltage SOC curve, where the peak point corresponds to the intermediate feature point.

[0013] For example, the battery is a lithium iron phosphate battery.

[0014] According to a second aspect of the present invention, a computer program product is provided, comprising a computer program that, when executed by one or more processors, enables the processors to perform the early warning method according to the present invention.

[0015] According to a third aspect of the present invention, a battery management system is provided, wherein the battery management system includes a memory and a processor, the processor being configured to implement the warning method according to the present invention using a computer program product according to the present invention. Attached Figure Description

[0016] The invention will now be described in more detail with reference to the accompanying drawings, which will provide a better understanding of its principles, features, and advantages. The drawings include: Figure 1a and Figure 1b Schematic diagrams of voltage SOC curves and differential voltage SOC curves for a battery warning method according to an exemplary embodiment of the present invention are shown respectively. Figure 2 A schematic diagram of open-circuit voltage-capacity curves at different health levels is shown according to an exemplary embodiment of the present invention; Figure 3 A schematic flowchart of a warning method for a battery according to an exemplary embodiment of the present invention is shown; Figure 4 A schematic flowchart of step S3 of an early warning method according to an exemplary embodiment of the present invention is shown. Detailed Implementation

[0017] To make the technical problems to be solved, the technical solutions, and the beneficial technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and several exemplary embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0018] This specification provides the operational steps for the methods described in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only possible execution order.

[0019] Figure 1a and Figure 1b Schematic diagrams of the voltage SOC curve and the differential voltage SOC curve of a warning method for a battery according to an exemplary embodiment of the present invention are shown respectively. Figure 2 A schematic diagram of open-circuit voltage-capacity curves at different health levels is shown according to an exemplary embodiment of the present invention. Here, the battery is particularly a lithium iron phosphate battery having a positive electrode made of lithium iron phosphate and a negative electrode made of graphite, wherein, during operation, lithium ions are inserted and extracted between the positive and negative electrode materials, accompanied by an external flow of electrons.

[0020] like Figure 1a As shown, the voltage-to-charge (SOC) curve is a curve showing the change of battery voltage with charge level. The vertical axis represents the charging voltage (Vol), and the horizontal axis represents the charge level (SOC), expressed as a percentage (%). This voltage-to-charge curve has a low SOC region, a plateau region, and a high SOC region. In the low SOC region (e.g., 0% to 20% SOC), the charging voltage increases rapidly with increasing SOC, and the graphite anode transitions from a lithium-poor state to a lower-order lithium-carbon compound. In the plateau region (e.g., 20% to 90% SOC), the charging voltage remains almost constant within a narrow range, e.g., 3.3V to 3.4V. Within this plateau region, there is a relatively sloping inflection point where the voltage exhibits a relatively significant jump within a small range of SOC variation. This inflection point is the intermediate characteristic point (MFP), at which a transition from LiC to LiC occurs in the anode. 12 The phase transition to LiC6 occurs. In the high SOC region (e.g., 90% to 100% SOC), the charging voltage rises rapidly until it reaches the charging cutoff voltage.

[0021] like Figure 1b As shown, the differential voltage SOC curve is the first derivative curve of the voltage SOC curve and describes the slope of the voltage SOC curve at each point. Its vertical axis is the differential voltage dV / dQ, in mV / Ah, and the horizontal axis is the charge level SOC, in percentage (%). When the voltage SOC curve reaches an inflection point, the differential voltage SOC curve will show a distinct peak point, which corresponds to the intermediate characteristic point MFP.

[0022] like Figure 2As shown, the open-circuit voltage-capacity curve describes the relationship between the open-circuit voltage and the absolute charge added to the battery when it reaches electrochemical equilibrium. The vertical axis represents the open-circuit voltage (OCV) in volts (V), and the horizontal axis represents the capacity (Q) in ampere-hours (Ah). Figure 2 The diagram shows four curves, L1 to L4, representing different State of Health (SOH) levels. Curve L1 corresponds to 100% SOH, curve L2 to 90% SOH, curve L3 to 80% SOH, and curve L4 to 70% SOH. Based on the changes from L1 to L4, it can be seen that during normal battery use, as the battery ages, its health level gradually declines, and the total chargeable capacity decreases accordingly. However, the capacity Q corresponding to the intermediate feature point MPF remains essentially unchanged. Therefore, the intermediate feature point MPF can be used as a capacity anchor during normal battery aging. However, when the battery is in an abnormal aging state, lithium dendrites precipitate, causing a significant shift in the intermediate feature point MPF, resulting in a noticeable change in its corresponding capacity.

[0023] Figure 3 A schematic flowchart of a warning method for batteries according to an exemplary embodiment of the present invention is shown.

[0024] like Figure 3 As shown, the early warning method according to the present invention includes the following steps: S1: Obtain the rated intermediate capacity at the intermediate feature point MFP of the battery; S2: Obtain the total calibrated capacity of the battery; S3: During the charging process, identify the intermediate feature point MFP of the battery and calculate the first charging capacity corresponding to the intermediate feature point MFP based on the rated intermediate capacity. S4: Record the second charging capacity from the intermediate feature point MFP to the fully charged state, and calculate the estimated total capacity of the battery from the first charging capacity and the second charging capacity; S5: Compare the estimated total capacity with the calibrated total capacity, determine whether the battery is at risk based on the comparison result, and issue a warning signal when a risk is detected.

[0025] For example, in step S5, when the estimated total capacity and the calibrated total capacity are substantially equal or their ratio is within a set range, it can be determined that the intermediate feature point (MFP) can still be used normally as a capacity anchor and the battery is in a normal aging state. However, when the ratio of the estimated total capacity to the calibrated total capacity is greater than a set threshold, such as 1.15, it is determined that the battery is at risk. In this case, it can be determined that the intermediate feature point (MFP) has significantly shifted due to the precipitation of lithium dendrites damaging the negative electrode material. Therefore, it can be determined that the battery has an abnormal aging safety risk, and a warning signal can be issued to remind the user to repair the battery, thereby preventing safety accidents. Of course, other set thresholds that are considered meaningful by those skilled in the art can also be considered.

[0026] For example, in step S5, when the ratio of the estimated total capacity to the calibrated total capacity is greater than a set threshold, the anomaly count is incremented by one. When the anomaly count reaches a preset value, such as 3, it is determined that the battery is at risk. This avoids false alarms triggered by a single accidental error, thereby improving the reliability of the warning.

[0027] For example, in step S1, the rated intermediate capacity at the intermediate characteristic point (MFP) should be determined under standard conditions. Standard conditions refer to a brand-new battery or a battery that has undergone a small number of standard cycle activations being charged from 0% SOC to 100% SOC with a small charging current and allowed sufficient resting time to eliminate polarization and ensure voltage stability. Specifically, the rated intermediate capacity at the intermediate characteristic point (MFP) can be directly provided by the battery supplier and stored in the battery management system used for the battery. When implementing the warning method, the rated intermediate capacity at the intermediate characteristic point (MFP) is directly retrieved by the battery management system.

[0028] For example, in step S2, the total calibrated capacity of the battery is obtained by performing an open-circuit voltage calibration cycle on the battery. In the open-circuit voltage calibration cycle, the battery is placed in a low-charge state and left to stand to measure a first open-circuit voltage. Then, the battery is charged to a full charge state and left to stand to measure a second open-circuit voltage. Based on the first and second open-circuit voltages, and combined with a pre-stored open-circuit voltage-state-of-charge (OCV-SOC) curve, the corresponding first and second state-of-charge values ​​are determined. The amount of charge transferred between the first and second state-of-charge values ​​is obtained. Based on the transferred amount of charge and the first and second state-of-charge values, the total calibrated capacity is calculated. Here, this open-circuit voltage calibration cycle can be performed during battery use, and the calculated total calibrated capacity is stored in the battery management system and invoked when implementing the warning method.

[0029] For example, in step S3, the first charging capacity is calculated based on the rated intermediate capacity and a correction factor, which is determined based on at least one of the following influencing factors: average charging current, initial state of charge, charging temperature, battery aging degree, and battery rated capacity. This can compensate for the influence of each influencing factor on the intermediate characteristic point (MFP) and further improve the capacity estimation accuracy during actual charging. Here, each influencing factor is assigned a corresponding individual correction factor; for example, a current correction factor is set for the average charging current, and a state of charge correction factor is set for the initial state of charge, etc. The final correction factor for the first charging capacity can be calculated by combining the individual correction factors of each influencing factor. Of course, other influencing factors that are considered meaningful by those skilled in the art can also be considered.

[0030] Figure 4 A schematic flowchart of step S3 of an early warning method according to an exemplary embodiment of the present invention is shown.

[0031] like Figure 1a and Figure 4 As shown, in step S3, identifying the intermediate feature point MFP of the battery includes the following steps: S31: Calculate the differential voltage SOC curve during the charging process; S32: Within a preset state of charge range, identify the peak point of the differential voltage SOC curve, where the peak point corresponds to the intermediate feature point MFP.

[0032] For example, in step S32, the preset state of charge range is, for instance, 30% to 90%, thereby avoiding the misidentification of peak points in low and high SOC regions, which are unrelated to the phase transition of graphite and should not be considered intermediate feature points (MFPs). This avoids high-noise regions and improves the detection accuracy of intermediate feature points (MFPs). In particular, the identified peak points should be greater than the differential voltage threshold T, which can be pre-determined from experimental and / or empirical data and stored in the battery management system.

[0033] According to the present invention, a computer program product is provided, comprising a computer program that, when executed by one or more processors, enables the processors to perform a battery warning method according to the present invention.

[0034] According to the present invention, a battery management system is also proposed, comprising a memory and a processor, the processor being configured to implement the battery warning method according to the present invention using a computer program product according to the present invention. Here, the memory stores, in particular, the rated intermediate capacity at intermediate characteristic points of the battery and / or the calibrated total capacity of the battery.

[0035] The foregoing description of the embodiments is limited to the framework of the examples given. Of course, the various features of the embodiments can be freely combined with each other without departing from the framework of the invention, as long as it is technically meaningful.

[0036] Other advantages and alternative embodiments of the present invention will be apparent to those skilled in the art. Therefore, the present invention is not, in its broader sense, limited to the specific details, representative structures, and exemplary embodiments shown and described. Rather, those skilled in the art can make various modifications and substitutions without departing from the basic spirit and scope of the invention.

Claims

1. A warning method for batteries, characterized in that, The early warning method includes at least the following steps: S1: Obtain the rated intermediate capacity at the intermediate feature point (MFP) of the battery; S2: Obtain the total calibrated capacity of the battery; S3: During the charging process, the intermediate feature point (MFP) of the battery is identified, and the first charging capacity corresponding to the intermediate feature point (MFP) is calculated based on the rated intermediate capacity; S4: Record the second charging capacity from the intermediate feature point (MFP) to the fully charged state, and calculate the estimated total capacity of the battery from the first charging capacity and the second charging capacity; S5: Compare the estimated total capacity with the calibrated total capacity, determine whether the battery is at risk based on the comparison result, and issue a warning signal when a risk is detected.

2. The early warning method according to claim 1, characterized in that, When the ratio of the estimated total capacity to the calibrated total capacity is greater than a set threshold, the battery is deemed to be at risk.

3. The early warning method according to claim 2, characterized in that, When the ratio is greater than the set threshold, the anomaly count is incremented by one. When the anomaly count reaches a preset value, it is determined that the battery is at risk.

4. The early warning method according to any one of the preceding claims, characterized in that, In step S3, the first charging capacity is calculated based on the rated intermediate capacity and a correction factor, wherein the correction factor is determined based on at least one of the following influencing factors: average charging current, initial state of charge, charging temperature, battery aging degree, and battery rated capacity.

5. The early warning method according to any one of the preceding claims, characterized in that, In step S1, the rated intermediate capacity is provided by the battery supplier and stored in the battery management system for the battery.

6. The early warning method according to any one of the preceding claims, characterized in that, In step S2, the total calibration capacity is obtained by performing an open-circuit voltage calibration cycle on the battery.

7. The early warning method according to any one of the preceding claims, characterized in that, In step S3, identifying the intermediate feature point (MFP) of the battery includes the following steps: S31: Calculate the differential voltage SOC curve during the charging process; S32: Within a preset state of charge range, identify the peak point of the differential voltage SOC curve, where the peak point corresponds to the intermediate feature point (MFP).

8. The early warning method according to any one of the preceding claims, characterized in that, The battery is a lithium iron phosphate battery.

9. A computer program product comprising a computer program, characterized in that, When the computer program is executed by one or more processors, the processors are capable of performing the early warning method according to any one of claims 1 to 8.

10. A battery management system, characterized in that, The battery management system includes a memory and a processor, the processor being configured to implement the warning method according to any one of claims 1 to 8 using the computer program product according to claim 9.

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