Over-discharge battery repairing method and device

Abstract

The invention provides an over-discharge battery repairing method and device, and relates to the field of batteries, and the over-discharge battery repairing method comprises the steps: charging an over-discharge battery to a first capacity with a first current, and standing the over-discharge battery until the voltage of the over-discharge battery reaches a stable state; the over-discharge battery is charged to a rated voltage with a second current, a low-current charging process is repeatedly executed until a first duration is reached, and the low-current charging process comprises the steps that the over-discharge battery is charged to the rated voltage with a third current, and standing is performed for a second duration; the first current and the third current are far smaller than the second current, and the second duration is far smaller than the first duration. The overdischarge battery repairing method and device provided by the embodiment of the invention can be used for solving the technical problems of low output voltage, unstable output voltage and short service life of an overdischarge battery in the prior art.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a method and device for repairing over-discharged batteries. Background Art

[0002] During battery discharge, the positive electrode active material (such as lithium cobalt oxide in lithium-ion batteries) undergoes a redox reaction with the negative electrode active material (such as graphite), causing lithium ions to migrate between the positive and negative electrodes and discharge outward. Battery overdischarge refers to the condition in which a battery continues to discharge even after the voltage has fallen below its safe operating voltage limit. This abnormal operating condition, which significantly harms battery performance and lifespan, is common in various types of rechargeable batteries (such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries). Overdischarge can lead to excessive delithiation of the negative electrode material, lattice distortion of the positive electrode material (such as the collapse of the LiCoO2 structure in lithium-ion batteries), and the inability of lithium dendrites formed at the negative electrode to fully re-embed into the graphite layer, resulting in permanent capacity loss. This can accelerate electrolyte decomposition, generate large amounts of gases (such as CO2 and H2) and heat, and disrupt the battery's internal balance, among other issues.

[0003] After the battery is over-discharged, although there is still a certain output voltage, it is no longer usable. At this time, if the battery is connected to a constant current power supply in the conventional way to charge the over-discharged battery, although the over-discharged lithium battery can be restored to a usable state, a series of problems may occur, such as low battery output voltage, unstable output voltage, and shortened battery life. Summary of the Invention

[0004] In view of this, it is necessary to provide a method and device for repairing an over-discharged battery to solve the technical problems of low output voltage, unstable output voltage and shortened battery life existing in the prior art.

[0005] In order to solve the above technical problems, in a first aspect, the present application provides a method for repairing an over-discharged battery, comprising: charging the over-discharged battery to a first capacity with a first current, and standing the over-discharged battery until the voltage of the over-discharged battery reaches a stable state; charging the over-discharged battery to a rated voltage with a second current, and repeating a low-current charging process until a first duration is reached, wherein the low-current charging process comprises: charging the over-discharged battery to the rated voltage with a third current, and standing the battery for a second duration; wherein the first current and the third current are much smaller than the second current, and the second duration is much smaller than the first duration.

[0006] Compared with the related art, in the over-discharged battery repair method provided in the embodiment of the present application, for an over-discharged battery, the charging process will destroy the charge balance inside the over-discharged battery. Since the charge balance stability inside the over-discharged battery is relatively low, the over-discharged battery is first charged to a first capacity with a relatively low first current, which can avoid excessive damage to the charge balance with relatively low stability inside the over-discharged battery caused by high current charging, thereby causing further damage to the over-discharged battery; after the over-discharged battery is charged to the first capacity, the charge balance stability inside the over-discharged battery is improved, and at this time, the over-discharged battery is charged to the rated voltage with a relatively large second current, and the positive electrode active material precipitated at the negative electrode can be returned to the positive electrode by the relatively large charging current, thereby restoring the structure of the over-discharged battery, and then repeating the process. The over-discharged battery is charged to the rated voltage with a smaller third current for multiple times. On the one hand, the positive electrode active material remaining on the negative electrode can be gradually returned to the positive electrode. On the other hand, it can also avoid the over-discharge problem of the over-discharged battery caused by continuing to charge with a larger second current. After the over-discharged battery is charged to the rated voltage with the third current, the over-discharged battery is left to stand for a second period of time, so that the voltage of the over-discharged battery can be restored to stability. Thereafter, the over-discharged battery is charged to the rated voltage with the third current again. This is repeated multiple times to allow as much positive electrode active material precipitated on the negative electrode during the over-discharge process to return to the positive electrode as possible, thereby completing the repair of the over-discharged battery and solving the technical problems of low output voltage, unstable output voltage and shortened battery life of the over-discharged battery in the prior art.

[0007] In one possible implementation, after the over-discharged battery is allowed to stand for the first period of time, the over-discharged battery repair method further includes: measuring the DC internal resistance of the over-discharged battery with a fourth current, and selecting an over-discharged battery whose difference between the DC internal resistance and the calibrated internal resistance is less than a preset internal resistance threshold. By measuring the DC internal resistance of the over-discharged battery, over-discharged batteries whose difference between the DC internal resistance and the calibrated internal resistance is less than the preset internal resistance threshold are selected, i.e., over-discharged batteries with less damage are selected for subsequent repair. Over-discharged batteries with less damage are less different from normal batteries after repair, reducing the possibility that the over-discharged battery will still not function properly after repair and increasing the possibility that the repaired battery will function properly, thereby improving the overall efficiency of the over-discharged battery repair process and reducing repair costs.

[0008] In one possible implementation, measuring the DC internal resistance of the over-discharged battery with the fourth current includes: charging the over-discharged battery with the fourth current for a third time period, and measuring the charging DC internal resistance during the charging process; allowing the over-discharged battery to stand until a voltage of the over-discharged battery reaches a stable state, discharging the over-discharged battery with the fourth current for the third time period, and measuring the discharge DC internal resistance during the discharge process; the third time period is much shorter than the second time period.

[0009] In one possible implementation, the fourth current is greater than or equal to 1C and less than or equal to 2C, and the third duration is greater than or equal to 5s and less than or equal to 15s. The DC internal resistance is measured with a fourth current greater than or equal to 1C and less than or equal to 2C. A larger current can make the DC internal resistance measurement result more accurate. When measuring the DC internal resistance, charging / discharging is only performed for a period greater than or equal to 5s and less than or equal to 15s, thereby preventing further damage to the over-discharged battery caused by prolonged high-current charging / discharging.

[0010] In one possible implementation, after the over-discharged battery is allowed to stand for a first period of time, the over-discharged battery repair method further includes: alternately fully charging and fully discharging the over-discharged battery with a fifth current, obtaining the battery capacity of the over-discharged battery based on the full-charge data and the full-discharge data, and selecting the over-discharged battery whose difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold. Selecting the over-discharged battery whose difference between the battery capacity and the calibrated capacity is less than the preset capacity threshold means selecting the less severely damaged over-discharged battery for subsequent repair. The less severely damaged over-discharged battery will be less different from a normal battery after repair, reducing the possibility that the over-discharged battery will still not function properly after repair and increasing the possibility that the repaired battery will function properly, thereby improving the overall efficiency of the over-discharged battery repair process and reducing repair costs.

[0011] In one possible implementation, the over-discharged battery is a battery pack including a plurality of battery cells. After the over-discharged battery is allowed to rest for a first period of time, the over-discharged battery repair method further includes: charging / discharging the battery pack to a second capacity with a fifth current; and measuring the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack, and selecting the battery pack having the voltage difference less than a preset voltage difference threshold. By measuring the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack and selecting the battery pack having the voltage difference less than the preset voltage difference threshold, the battery pack with less severe damage is selected for subsequent repair. After repair, the battery pack with less severe damage is less different from a normal battery pack, reducing the possibility that the battery pack will still not function properly after repair and increasing the possibility that the repaired battery pack will function properly, thereby improving the overall efficiency of the battery pack repair process and reducing repair costs.

[0012] In one possible implementation, the fifth current is greater than or equal to 0.1C and less than or equal to 0.33C, the second capacity is less than or equal to 20% SOC, and the preset voltage difference threshold is less than or equal to 100 mV.

[0013] In one possible implementation, the first current is greater than or equal to 0.01C and less than or equal to 0.1C, the first capacity is greater than or equal to 20% SOC and less than or equal to 50% SOC, the second current is greater than or equal to 0.8C and less than or equal to 1.2C, the first duration is greater than or equal to 4h and less than or equal to 10h, the third current is greater than or equal to 0.01C and less than or equal to 0.1C, and the second duration is greater than or equal to 1min and less than or equal to 10min.

[0014] In a second aspect, an embodiment of the present application provides an over-discharged battery repair device, comprising: a constant current power supply and a controller connected to the constant current power supply, wherein the controller is used to execute the over-discharged battery repair method as described above to control the constant current power supply to charge and discharge the over-discharged battery.

[0015] In a possible implementation, the device further includes an internal resistance measuring device connected to the controller, wherein the internal resistance measuring device is used to measure the DC internal resistance of the over-discharged battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A schematic flow chart of the over-discharge battery repair method provided in Example 1 of the present application; Figure 2 A flow chart of the over-discharge battery repair method provided in Example 2 of the present application; Figure 3 A flow chart of the over-discharge battery repair method provided in Example 3 of the present application; Figure 4 A flow chart of the over-discharge battery repair method provided in the fourth embodiment of the present application; Figure 5 The voltage images of the over-discharged battery before and after over-discharge provided in the embodiment of the present application; Figure 6-Figure 8 Voltage images at different stages during the process of implementing the over-discharged battery repair method provided by the embodiment of the present application for the over-discharged battery provided by the embodiment of the present application; Figures 9-12 Schematic diagram of the structure of the over-discharged battery repair device provided in different embodiments of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0019] In the description of the embodiments of this application, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0020] The terms "first," "second," and so on, used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, technical features designated as "first" or "second" may explicitly or implicitly include at least one such feature.

[0021] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] Please refer to Figure 1 The present invention provides a method for repairing an over-discharged battery, which specifically includes the following steps: Step S101 : charging an over-discharged battery to a first capacity with a first current, and leaving the over-discharged battery to stand until the voltage of the over-discharged battery reaches a stable state.

[0023] In this step, the first current is a constant current. Specifically, the first current can be applied to the over-discharged battery by a constant current source to charge the over-discharged battery until the capacity of the over-discharged battery reaches the first capacity. After the first capacity is reached, all loads connected to the over-discharged battery are disconnected, and the over-discharged battery is placed on a horizontal plane and left to stand for a period of time until the voltage of the over-discharged battery reaches a stable state.

[0024] The voltage of the over-discharged battery reaching a stable state can specifically mean that the voltage of the over-discharged battery does not change for a long time or the difference in the change decreases below a preset value. Specifically, the voltage of the over-discharged battery can be measured at intervals during the process of the over-discharged battery being left at rest until the measurement results for multiple consecutive times do not change or the difference in the change decreases below a preset value. In this embodiment, for example, the voltage of the over-discharged battery can be measured once every hour during the process of the over-discharged battery being left at rest until the measurement results for three consecutive times do not change or the difference in the three consecutive measurement results is less than 100 mV. It will be understood that the foregoing is merely an example of a specific implementation method of leaving the over-discharged battery at rest until the voltage of the over-discharged battery reaches a stable state in some embodiments of the present application. In some other embodiments of the present application, for example, the over-discharged battery can be left at rest for a longer period of time, for example, the over-discharged battery can be left at rest for 24 hours or even longer.

[0025] In this step, the first current is greater than or equal to 0.01C and less than or equal to 0.1C, and the first capacity is greater than or equal to 20% SOC and less than or equal to 50% SOC. In embodiments of the present application, the first current and the first capacity can be pre-set based on the actual conditions of the over-discharged battery. The more severe the over-discharge of the over-discharged battery, the smaller the first current and the smaller the first capacity can be set. Conversely, the less severe the over-discharge of the over-discharged battery, the larger the first current and the larger the first capacity can be set. Specifically, the over-discharge degree of the over-discharged battery can be determined based on parameters such as the power-down rate of the over-discharged battery and the ratio of the voltage of the over-discharged battery to the rated voltage. For example, in this embodiment, the first current can be set to 0.05C and the first capacity can be set to 30% SOC. Alternatively, in some other embodiments of the present application, the first current can be set to 0.07C and the first capacity can be set to 35% SOC.

[0026] C represents the ratio of the battery's charge / discharge current to its rated capacity. The calculation formula is: C = I / Q, where I is the battery's charge / discharge current (unit: ampere / A) and Q is the battery's rated capacity (unit: ampere-hour / Ah). For example, for a battery with a rated capacity of 10Ah, if the charge current is 5A, then the charge current is 5A / 10Ah = 0.5C; conversely, if the discharge current is 0.5C, then the charge current is 0.5C * 10Ah = 5A.

[0027] SOC is the battery's state of charge, representing the ratio of the battery's current remaining capacity to its rated capacity, usually expressed as a percentage. SOC = rated capacity / remaining capacity * 100%. For example, if the battery's rated capacity is 100Ah and its current remaining capacity is 50Ah, then SOC = 50Ah / 100Ah * 50%.

[0028] Step S102: charging the over-discharged battery to a rated voltage with a second current.

[0029] In this step, the second current is a constant current, and specifically, the second current can be applied to the over-discharged battery by a constant current source to charge the over-discharged battery until the actual voltage of the over-discharged battery reaches the rated voltage. The constant current source providing the first current and the second current can be the same current source or different current sources.

[0030] In some embodiments of the present application, the second current may be greater than or equal to 0.8 C and less than or equal to 1.2 C. For example, in this embodiment, the second current may be set to 1 C.

[0031] Step S103: Repeat the low-current charging process until the first time duration is reached.

[0032] In this step, the low-current charging process may specifically include: S1: charging the over-discharged battery to the rated voltage with a third current; S2: Stand still for the second time.

[0033] Due to the abnormal internal condition of the over-discharged battery, after the over-discharged battery is charged to the rated voltage with the larger second current in step S102, its internal charge condition is not stable, and the voltage usually drops rapidly, that is, the power is quickly lost. On this basis, the over-discharged battery is recharged to the rated voltage with a third current that is much smaller than the second current. Charging the over-discharged battery again with a small current can avoid excessive interference of the large current charging on the internal charge condition of the discharged battery, making the internal charge condition of the over-discharged battery fluctuate less. Then, the over-discharged battery is allowed to stand for a second time period to make the internal charge condition of the over-discharged battery more stable. This process is repeated multiple times until the total duration of the small current charging process reaches the first time period.

[0034] In an embodiment of the present application, the third current is much smaller than the second current, and the first duration is much larger than the second duration. Specifically, for example, the first duration may be greater than or equal to 4 hours and less than or equal to 10 hours, the third current may be greater than or equal to 0.01C and less than or equal to 0.1C, and the second duration may be greater than or equal to 1 minute and less than or equal to 10 minutes.

[0035] It can be understood that, in the present application, “much greater than” and “much less than” specifically refer to a difference of at least one order of magnitude between the two, that is, a ratio between the two is greater than 10 or less than 0.1.

[0036] Compared with the related art, in the over-discharged battery repair method provided in the first embodiment of the present invention, for an over-discharged battery, the charging process will destroy the charge balance inside the over-discharged battery. Since the charge balance stability inside the over-discharged battery is relatively low, the over-discharged battery is first charged to a first capacity with a relatively low first current, which can avoid excessive damage to the charge balance with relatively low stability inside the over-discharged battery caused by high current charging, thereby causing further damage to the over-discharged battery. After the over-discharged battery is charged to the first capacity, the charge balance stability inside the over-discharged battery is improved. At this time, the over-discharged battery is charged to the rated voltage with a relatively large second current. The positive electrode active material precipitated on the negative electrode can be returned to the positive electrode by the relatively large charging current, thereby restoring the structure of the over-discharged battery. Thereafter, the charging process is repeated multiple times. The over-discharged battery is charged to the rated voltage with a smaller third current for the second time. On the one hand, the positive electrode active material remaining on the negative electrode can be gradually returned to the positive electrode. On the other hand, it can also avoid the over-charging problem of the over-discharged battery caused by continuing to charge with the larger second current. After the over-discharged battery is charged to the rated voltage with the third current, the over-discharged battery is left to stand for a second time, so that the voltage of the over-discharged battery can be restored to stability. Thereafter, the over-discharged battery is charged to the rated voltage with the third current again. This process is repeated multiple times to allow as much positive electrode active material precipitated on the negative electrode during the over-discharge process to return to the positive electrode as possible, thereby completing the repair of the over-discharged battery and solving the technical problems of low output voltage, unstable output voltage and shortened battery life of the over-discharged battery in the prior art.

[0037] Please refer to Figure 2 , the embodiment of the present application provides a method for repairing an over-discharged battery, which specifically includes: Step S201 : charging the over-discharged battery to a first capacity with a first current, and leaving the over-discharged battery to stand until the voltage of the over-discharged battery reaches a stable state.

[0038] Step S202: measuring the DC internal resistance of the over-discharged battery with a fourth current, and selecting an over-discharged battery whose difference between the DC internal resistance and the calibrated internal resistance is smaller than a preset internal resistance threshold.

[0039] In this step, the calibrated internal resistance is the DC internal resistance of the over-discharged battery when it is in normal working condition, which can be obtained by measuring the DC internal resistance of a normal battery of the same model as the over-discharged battery, or by measuring the over-discharged battery when it is still in normal working condition.

[0040] In this step, the DC resistance (DCR) represents the battery's resistance to current in a DC circuit and reflects the difficulty of charge transfer within the battery. In this application, for over-discharged batteries, the DC resistance (DCR) can be used to determine the extent of damage caused by the over-discharge process. Over-discharged batteries whose difference between the DC resistance and the calibrated resistance is less than a preset internal resistance threshold are selected for subsequent repair. Over-discharged batteries with less damage are less different from normal batteries after repair, reducing the possibility that the over-discharged battery will still not function properly after repair and increasing the possibility that the repaired battery will function properly, thereby improving the overall efficiency of the over-discharged battery repair process and reducing repair costs.

[0041] Furthermore, the DC internal resistance includes charging DC internal resistance and discharging DC internal resistance. In embodiments of the present application, measuring the DC internal resistance of an over-discharged battery with a fourth current may specifically involve testing only the charging DC resistance, only the discharging DC resistance, or both the charging and discharging DC resistances. For example, the over-discharged battery may be charged with the fourth current for a third duration, and the charging DC internal resistance during the charging process is measured; the over-discharged battery is allowed to stand until the voltage of the over-discharged battery reaches a stable state; the over-discharged battery is then discharged with the fourth current for a third duration, and the discharging DC internal resistance during the discharging process is measured. The third duration is substantially shorter than the second duration. A period of time is allowed between testing the charging DC internal resistance of the over-discharged battery with the fourth current and testing the discharging DC resistance of the over-discharged battery with the fourth current, and the over-discharged battery is allowed to stand until the voltage of the over-discharged battery reaches a stable state. This reduces voltage fluctuations in the over-discharged battery caused by the charging DC internal resistance measurement process, which could affect subsequent discharge DC internal resistance measurements, thereby improving the stability of the discharge DC resistance measurement results. The order of measuring the charging DC internal resistance and the discharging DC internal resistance may be as follows: first measuring the charging DC internal resistance and then measuring the discharging DC internal resistance, or first measuring the discharging DC internal resistance and then measuring the charging DC internal resistance.

[0042] In the embodiment of the present application, the fourth current can be set to be greater than or equal to 1C and less than or equal to 2C, and the third duration can be set to be greater than or equal to 5s and less than or equal to 15s. That is, the DC internal resistance is measured with a fourth current greater than or equal to 1C and less than or equal to 2C. A larger fourth current can make the measurement result of the DC internal resistance more accurate. When measuring the DC internal resistance, charging / discharging is only performed for greater than or equal to 5s and less than or equal to 15s, which can avoid further damage to the over-discharged battery caused by long-term high-current charging / discharging.

[0043] Step S203: charging the over-discharged battery to a rated voltage with a second current.

[0044] Step S204: Repeat the low-current charging process until the first time duration is reached.

[0045] Specifically, steps S201, S203, and S204 in this embodiment are substantially the same as steps S101 to S103 in the aforementioned embodiment, and reference may be made to the detailed description in the aforementioned embodiment for details.

[0046] Compared with the related art, the over-discharged battery repair method provided in the second embodiment of the present application includes all the technical features of the aforementioned embodiments and has the same technical effects. In addition, before executing steps S203 and S204 to repair the battery, the over-discharged batteries are screened according to the DC internal resistance, and the over-discharged batteries whose difference between the DC internal resistance and the calibrated internal resistance is less than a preset internal resistance threshold are selected, that is, the over-discharged batteries with a lower degree of damage are selected for the subsequent repair process. After repair, the over-discharged batteries with a lower degree of damage are less different from normal batteries, which reduces the possibility that the over-discharged batteries may still not work normally after repair and increases the possibility that the repaired batteries can work normally, thereby improving the overall efficiency of the over-discharged battery repair process and reducing the repair cost.

[0047] Please refer to Figure 3 , the embodiment of the present application provides a method for repairing an over-discharged battery, which specifically includes: Step S301 : charging the over-discharged battery to a first capacity with a first current, and leaving the over-discharged battery to stand until the voltage of the over-discharged battery reaches a stable state.

[0048] Step S302: alternately fully charging and fully discharging the over-discharged battery with a fifth current, obtaining the battery capacity of the over-discharged battery according to the full-charge data and the full-discharge data, and selecting the over-discharged battery whose difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold.

[0049] In this step, the calibrated capacity is the battery capacity of the over-discharged battery when it is in normal working condition, which can be obtained by measuring the battery capacity of a normal battery of the same model as the over-discharged battery, or by measuring the over-discharged battery when it is still in normal working condition.

[0050] In this step, the over-discharged battery is fully charged with the fifth current, i.e., the over-discharged battery is charged with the fifth current until it reaches the rated capacity or rated voltage, or until the capacity or voltage of the over-discharged battery no longer changes. The over-discharged battery is fully discharged with the fifth current, i.e., the over-discharged battery is discharged with the fifth current until it reaches the minimum capacity or minimum voltage.

[0051] In this application, for over-discharged batteries, the extent of damage caused by the over-discharge process can be determined based on their actual battery capacity. Over-discharged batteries whose capacity difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold are selected for subsequent repair. Over-discharged batteries with less damage are less different from normal batteries after repair, reducing the possibility that the over-discharged battery will still not work properly after repair and increasing the possibility that the repaired battery can work properly, thereby improving the overall efficiency of the over-discharged battery repair process and reducing repair costs.

[0052] Step S303: charging the over-discharged battery to a rated voltage with a second current.

[0053] Step S304: Repeat the low-current charging process until the first time duration is reached.

[0054] Specifically, steps S301, S303, and S304 in this embodiment are substantially the same as steps S101 to S103 in the aforementioned embodiment, and reference may be made to the detailed description in the aforementioned embodiment for details.

[0055] Compared with the related art, the over-discharged battery repair method provided in the third embodiment of the present application includes all the technical features of the aforementioned embodiments and has the same technical effects. In addition, before executing steps S303 and S304 to repair the battery, the over-discharged batteries are screened according to the battery capacity, and the over-discharged batteries whose capacity difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold are selected, that is, the over-discharged batteries with a lower degree of damage are selected for the subsequent repair process. After repair, the over-discharged batteries with a lower degree of damage are less different from normal batteries, which reduces the possibility that the over-discharged batteries may still not work normally after repair, and increases the possibility that the repaired batteries can work normally, thereby improving the overall efficiency of the over-discharged battery repair process and reducing the repair cost.

[0056] Please refer to Figure 4 For a battery pack including multiple battery cells, an embodiment of the present application provides a method for repairing an over-discharged battery. That is, in the fourth embodiment, the over-discharged battery is a battery pack including multiple battery cells, which specifically includes: Step S401 : charging the battery pack to a first capacity with a first current, and leaving the battery pack to stand until the voltage of the battery pack reaches a stable state.

[0057] Step S402: charging / discharging the battery pack to a second capacity with a fifth current; measuring the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack, and selecting a battery pack with a voltage difference smaller than a preset voltage difference threshold.

[0058] In this step, the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack is measured. Specifically, each battery cell can be measured to obtain the voltage of all battery cells, and then the maximum voltage and the minimum voltage are selected from them. Finally, the voltage difference between the maximum voltage and the minimum voltage is calculated. The smaller the voltage difference between the battery cells in the battery pack, the smaller the difference between the battery cells, and the less damage to the battery pack as a whole. Selecting a battery pack with a voltage difference less than a preset voltage difference threshold means selecting a battery pack with a lower degree of damage for the subsequent repair process. After repair, a battery pack with a lower degree of damage will be less different from a normal battery pack, reducing the possibility that the battery pack will still not work properly after repair and increasing the possibility that the repaired battery pack can work properly, thereby improving the efficiency of the overall battery pack repair process and reducing repair costs.

[0059] Furthermore, in some embodiments of the present application, the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack may be repeatedly measured multiple times within a period of time, and a battery pack in which all voltage differences are smaller than a preset voltage difference threshold is selected.

[0060] Furthermore, the fifth current may be greater than or equal to 0.1C and less than or equal to 0.33C, the second capacity may be less than or equal to 20% SOC, and the preset voltage difference threshold may be less than or equal to 100mV.

[0061] Step S403: charging the battery pack to a rated voltage with a second current.

[0062] Step S404: Repeat the low-current charging process until the first time duration is reached.

[0063] Specifically, steps S401, S403, and S404 in this embodiment are substantially the same as steps S101 to S103 in the aforementioned embodiment, and reference may be made to the detailed description in the aforementioned embodiment for details.

[0064] Compared with the related art, the battery pack repair method provided in the fourth embodiment of the present application includes all the technical features of the aforementioned embodiments and has the same technical effects. In addition, for over-discharged batteries in the form of battery packs, before executing steps S403 and S404 to repair the batteries, the battery packs are screened according to the voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack, and battery packs whose capacity difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold are selected, that is, battery packs with a lower degree of damage are selected for subsequent repair processes. After repair, battery packs with a lower degree of damage are less different from normal batteries, reducing the possibility that the battery pack may still not work normally after repair, and increasing the possibility that the repaired battery can work normally, thereby improving the overall efficiency of the battery pack repair process and reducing the repair cost.

[0065] Below, the above technical solution will be described in detail with reference to specific data and diagrams.

[0066] Please refer to Figure 5 Taking an over-discharged battery as an example, which is composed of 126 single cells connected in series, the total voltage before over-discharge is 412V, and after 20 days of over-discharge, the total voltage is 136V, the single cell voltage is about 1V, the voltage difference of 126 battery cells is 168mV, the calibrated DC internal resistance is 60mΩ, and the calibrated capacity is 300Ah. The over-discharge repair is carried out.

[0067] First, it was charged with a current of 0.05C to 20% SOC and left to stand for 2 hours. At this time, the maximum voltage of the battery cell was 3.223V, the maximum voltage was 3.221V, and the voltage difference was 2mV.

[0068] Then, please refer to Figure 6 , it was charged with a 2C current for 10s and left to stand for 2h. The charging DCR was 61.72mΩ. It was discharged with a 2C current for 10s and left to stand for 2h. The discharge DCR was 59.04mΩ. After the DCR test, the maximum static voltage was 3.248V, the minimum was 3.244V, and the voltage difference was 4mV. The difference between the charging DCR and the discharging DCR and the calibrated DC internal resistance were all less than the preset resistance threshold of 5mΩ, which met the standard and continued with subsequent operations.

[0069] Then, please refer to Figure 7 , using a 0.33C current for charging and then a 0.33C current for discharging. The test shows that the high-voltage battery system capacity is 298.512Ah, which is less than the preset capacity of 300 Ah by 5Ah, and meets the standard to continue subsequent operations.

[0070] Then, please refer to Figure 8 , use 0.33C current to charge until 20% SOC, disconnect the battery system from all loads, and let it stand for 2 hours. The static voltage 1 of all single cells is collected through the battery management system, with a maximum voltage of 3.271V and a minimum voltage of 3.268V. After standing for 24 hours, the static voltage 2 of all single cells is collected through the battery management system, with a maximum voltage of 3.269V and a minimum voltage of 3.266V. After standing for 48 hours, the static voltage 3 of all single cells is collected through the battery management system, with a maximum voltage of 3.269V and a minimum voltage of 3.266V. After standing for 80 hours, the static voltage 4 of all single cells is collected through the battery management system, with a maximum voltage of 3.269V and a minimum voltage of 3.266V. It is judged that the difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack is 3mV, which is less than the preset voltage difference of 100mV. If it meets the standard, continue with the subsequent operation.

[0071] Finally, charge the battery with a 1C current until the rated voltage of the battery cell or the rated voltage of the entire battery pack is reached, and then end the 1C charge. Charge the battery with a 0.05C current until the rated voltage of the battery cell or the rated voltage of the entire battery pack is reached, then let it rest for 10 minutes. Repeat the 0.05C charging and resting method for a total of 4 hours.

[0072] Combine Figures 5 to 8 It can be seen that the over-discharged battery has been repaired.

[0073] Please refer to Figure 9 Embodiment 5 of the present application provides an over-discharged battery repair device, comprising: a constant current power supply 100 and a controller 200 connected to the constant current power supply 100, wherein the controller 200 is used to execute the over-discharged battery repair method provided in the aforementioned embodiment to control the constant current power supply 100 to charge and discharge the over-discharged battery.

[0074] For further information, please refer to Figure 10 In some embodiments of the present application, the over-discharged battery repair device may further include an internal resistance measuring device 300 connected to the controller 200, and the internal resistance measuring device 300 is used to measure the DC internal resistance of the over-discharged battery.

[0075] For further information, please refer to Figure 11 In some embodiments of the present application, the over-discharged battery repair device may further include a capacity measuring device 400 connected to the controller 200, and the capacity measuring device 400 is used to measure the actual battery capacity of the over-discharged battery.

[0076] For further information, please refer to Figure 12 In some embodiments of the present application, the over-discharged battery repair device may further include a battery management system 500 connected to the controller 200. For a battery pack including multiple battery cells, the battery management system 500 is used to measure the voltage of each battery cell in the battery pack.

[0077] The above is a detailed introduction to the over-discharged battery repair method and device provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core ideas of the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. A method for repairing an over-discharged battery, characterized in that: include: charging the over-discharged battery to a first capacity with a first current, and allowing the over-discharged battery to stand until a voltage of the over-discharged battery reaches a stable state; Charging the over-discharged battery to a rated voltage with a second current, and repeatedly performing a low-current charging process until a first time period is reached, wherein the low-current charging process includes: charging the over-discharged battery to the rated voltage with a third current, and standing for a second time period; The first current and the third current are much smaller than the second current, and the second duration is much smaller than the first duration.

2. The over-discharge battery repair method according to claim 1, characterized in that: After the over-discharged battery is left standing for a first period of time, the over-discharged battery repair method further includes: The DC internal resistance of the over-discharged battery is measured with a fourth current, and the over-discharged battery is selected, the difference between the DC internal resistance and the calibrated internal resistance being smaller than a preset internal resistance threshold.

3. The over-discharge battery repair method according to claim 2, characterized in that: Measuring the DC internal resistance of the over-discharged battery with a fourth current includes: charging the over-discharged battery with the fourth current for a third period of time, and measuring the charging DC internal resistance during the charging process; allowing the over-discharged battery to stand until the voltage of the over-discharged battery reaches a stable state, discharging the over-discharged battery with the fourth current for the third time period, and measuring the discharge DC internal resistance during the discharge process; The third duration is much shorter than the second duration.

4. The over-discharge battery repair method according to claim 3, characterized in that: The fourth current is greater than or equal to 1C and less than or equal to 2C, and the third time duration is greater than or equal to 5s and less than or equal to 15s.

5. The over-discharge battery repair method according to claim 1, characterized in that: After the over-discharged battery is left standing for a first period of time, the over-discharged battery repair method further includes: The over-discharged battery is alternately fully charged and fully discharged with a fifth current, a battery capacity of the over-discharged battery is obtained according to the full charge data and the full discharge data, and the over-discharged battery is selected, wherein the difference between the battery capacity and the calibrated capacity is less than a preset capacity threshold.

6. The over-discharge battery repair method according to claim 1, characterized in that: The over-discharged battery is a battery pack including a plurality of battery cells. After the over-discharged battery is left at rest for a first period of time, the over-discharged battery repair method further includes: charging / discharging the battery pack to a second capacity with a fifth current; The voltage difference between the maximum voltage and the minimum voltage of each battery cell in the battery pack is measured, and the battery pack having the voltage difference smaller than a preset voltage difference threshold is selected.

7. The over-discharge battery repair method according to claim 6, characterized in that: The fifth current is greater than or equal to 0.1C and less than or equal to 0.33C, the second capacity is less than or equal to 20% SOC, and the preset voltage difference threshold is less than or equal to 100mV.

8. The over-discharge battery repair method according to claim 1, characterized in that: The first current is greater than or equal to 0.01C and less than or equal to 0.1C, the first capacity is greater than or equal to 20% SOC and less than or equal to 50% SOC, the second current is greater than or equal to 0.8C and less than or equal to 1.2C, the first duration is greater than or equal to 4h and less than or equal to 10h, the third current is greater than or equal to 0.01C and less than or equal to 0.1C, and the second duration is greater than or equal to 1min and less than or equal to 10min.

9. An over-discharged battery repair device, characterized in that: include: A constant current power supply and a controller connected to the constant current power supply, wherein the controller is used to execute the over-discharge battery repair method according to any one of claims 1 to 8 to control the constant current power supply to charge and discharge the over-discharge battery.

10. The over-discharge battery repair device according to claim 9, characterized in that: It also includes an internal resistance measuring device connected to the controller, and the internal resistance measuring device is used to measure the DC internal resistance of the over-discharged battery.

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