Battery charging mode analysis method and device

Abstract

The invention discloses a battery charging mode analysis method and device, and the method comprises the steps: charging a battery to an initial capacity with a small current for each to-be-tested voltage, and then carrying out the constant-voltage charging with the to-be-tested voltage until the charging current is smaller than a target current or the negative parameter potential is smaller than zero; the target current is a current representing that the battery is fully charged; taking the to-be-tested voltage which is charged until the current is smaller than the target current and has the shortest charging duration as the optimal constant voltage; after the battery is charged to each to-be-tested initial capacity with small current, charging is carried out with the optimal constant voltage; taking the to-be-tested initial capacity with the shortest charging time as the optimal charging initial capacity; and for each to-be-tested temperature, if the battery is fully charged at the constant voltage with the optimal constant voltage, taking the battery as the constant-voltage charging voltage at the to-be-tested temperature, otherwise, continuously reducing the optimal constant voltage to charge the battery until the battery can be fully charged at the constant voltage, and obtaining the constant-voltage charging voltage at the to-be-tested temperature.

Description

Technical Field

[0001] This application relates to the field of battery charging analysis technology, and in particular to a method and apparatus for analyzing battery charging methods. Background Technology

[0002] As a representative of new energy sources, lithium-ion batteries are characterized by high energy density, high discharge voltage, light weight, and environmental friendliness, and are widely used in electric vehicles, energy storage devices, and other fields. However, in the application of electric vehicles, battery charging time has consistently constrained the widespread adoption of the electric vehicle industry and has become one of the bottlenecks in its development. Therefore, analyzing faster battery charging methods is particularly important.

[0003] Currently, the most common fast charging method for batteries is staged constant current charging. Staged constant current charging, based on a multi-step constant current fast charging strategy, continuously increases the charging voltage in the initial stage, allowing for rapid charging with a constant, relatively large current. After the charging voltage reaches a set value, it enters the constant voltage charging stage, where the voltage is reduced in preset steps, performing constant voltage charging in stages.

[0004] However, this method cannot fully utilize the maximum fast charging capability of the battery cells at different remaining states of charge (SOC), especially in the low SOC range, thus limiting the improvement in charging speed. Furthermore, the multi-step constant current fast charging strategy is complex to control and requires high consistency among the individual cells in the battery pack, making it prone to improper current control during charging. When improper control occurs, especially at high SOC levels, it can lead to uneven lithium-ion deposition on the negative electrode surface, causing problems such as lithium deposition or dendrite growth, ultimately affecting the battery's cycle life and safety. Summary of the Invention

[0005] In view of the shortcomings of the prior art, this application provides a method and apparatus for analyzing battery charging methods to solve the problems that the prior art cannot fully utilize the maximum fast charging capability, cannot effectively reduce charging time, and is prone to affecting battery quality.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] The first aspect of this application provides a method for analyzing battery charging methods, including:

[0008] For each voltage to be tested, the target lithium battery is charged to the set initial capacity with a set small current, and then the target lithium battery is charged with constant voltage at the voltage to be tested until the charging current is less than the target current or the negative parameter potential is less than zero; wherein, the target current is the current that characterizes the battery when it is fully charged;

[0009] Among the various test voltages that are charged to a point where the current is less than the target current and then cuts off, the test voltage with the shortest charging time is determined as the optimal constant voltage.

[0010] After charging the target lithium battery to its respective initial capacity for testing with the set small current, the target lithium battery is fully charged with the optimal constant voltage.

[0011] The initial capacity to be tested with the shortest charging time is determined as the optimal initial charging capacity;

[0012] For each test temperature, the target lithium battery is left to stand at the test temperature for a set time, then charged to the optimal charging start capacity with the set small current, and then charged with constant voltage using the current optimal constant voltage.

[0013] If the target lithium battery cannot be fully charged using the current optimal constant voltage, then the target lithium battery is left to stand at room temperature for a preset time and then discharged at a set rate.

[0014] The current optimal constant voltage is reduced by a set margin, and the process returns to the step of placing the target lithium battery at the test temperature for a set duration.

[0015] If the target lithium battery is charged to full capacity using the current optimal constant voltage, then the current optimal constant voltage is determined as the constant voltage charging voltage at the test temperature.

[0016] Optionally, the above-mentioned analysis method for battery charging methods also includes:

[0017] Copper wires are implanted into the stack or core of the target lithium battery, and the copper wires are separated from the positive and negative electrodes of the target lithium battery to form the three electrodes of the target lithium battery.

[0018] The target lithium battery is connected to a charger, and the copper wire is subjected to lithium plating on both sides.

[0019] The target lithium battery is subjected to a set current at room temperature to determine its constant capacity.

[0020] Optionally, the above-mentioned analysis method for battery charging methods also includes:

[0021] Determine the stable voltage of the target lithium battery during the initial stage of constant current charging;

[0022] Within the set range corresponding to the stable voltage, the stable voltage and multiple voltages selected at set intervals are used as the voltage to be tested.

[0023] Optionally, in the above-described analysis method for battery charging methods, after charging the target lithium battery to a set initial capacity with a set small current, and then performing constant voltage charging on the target lithium battery with the voltage to be tested until the charging current is less than the target current or the negative parameter potential is less than zero, the method further includes:

[0024] Determine whether the current charging is stopped when the negative parameter potential is less than zero;

[0025] If the current charging is stopped when the negative parameter potential is less than zero, the target lithium battery is left to stand for a preset standing time, and the charging voltage is reduced according to the set voltage value. Then the target lithium battery is continued to be charged until the charging current is less than the target current or the negative parameter potential is less than zero. Then the process returns to the step of determining whether the current charging is stopped when the negative parameter potential is less than zero.

[0026] If the current charging is cut off when the charging current is less than the target current, then the test of the voltage to be tested ends.

[0027] If the overvoltage is not reduced, record the charging time of this test to obtain the charging time of the voltage to be tested.

[0028] Optionally, the above-mentioned analysis method for battery charging methods also includes:

[0029] Using the set small current and the constant voltage charging voltage at each of the test temperatures, the temperature range charging voltage MAP of the target lithium battery is determined.

[0030] A second aspect of this application provides an apparatus for analyzing battery charging methods, comprising:

[0031] The first voltage testing unit is used to charge the target lithium battery to a set initial capacity with a set small current for each voltage to be tested, and then charge the target lithium battery with the voltage to be tested at a constant voltage until the charging current is less than the target current or the negative parameter potential is less than zero; wherein, the target current is the current characterizing the battery when it is fully charged.

[0032] The first voltage determination unit is used to determine the test voltage with the shortest charging time among the various test voltages that are cut off when the charging current is less than the target current as the optimal constant voltage.

[0033] The capacity testing unit is used to charge the target lithium battery to each initial capacity to be tested using the set small current, and then fully charge the target lithium battery at the optimal constant voltage.

[0034] The capacity determination unit is used to determine the initial capacity to be tested with the shortest charging time as the optimal charging starting capacity.

[0035] The second voltage testing unit is used to, for each test temperature, place the target lithium battery at the test temperature for a set time, charge the target lithium battery with a set small current to the optimal charging start capacity, and perform constant voltage charging on the target lithium battery with the current optimal constant voltage.

[0036] The reset processing unit is used to discharge the target lithium battery at a set rate after the target lithium battery has been left to stand at room temperature for a preset time when the target lithium battery cannot be charged to full capacity at the current optimal constant voltage.

[0037] The down-adjustment unit is used to reduce the current optimal constant voltage by a set amount and return it to the temperature testing unit;

[0038] The second voltage determination unit is used to determine the current optimal constant voltage as the constant voltage charging voltage at the test temperature if the target lithium battery is charged to full capacity at the current optimal constant voltage.

[0039] Optionally, the above-mentioned battery charging method analysis device further includes:

[0040] An electrode implantation unit is used to implant copper wires into the stack or core of the target lithium battery and to separate the copper wires from the positive and negative electrodes of the target lithium battery to form the three electrodes of the target lithium battery.

[0041] A lithium plating unit is used to connect the target lithium battery into a charger and perform positive and negative lithium plating on the copper wire;

[0042] A capacity calibrator is used to calibrate the target lithium battery at room temperature according to a set current, thereby determining the calibrated capacity of the target lithium battery.

[0043] Optionally, the above-mentioned battery charging method analysis device further includes:

[0044] The third voltage determination unit is used to determine the stable voltage of the target lithium battery during the early stage of constant current charging;

[0045] The selection unit is used to select the stable voltage and select multiple voltages at set intervals within a set range corresponding to the stable voltage as the voltage to be tested.

[0046] Optionally, the above-mentioned battery charging method analysis device further includes:

[0047] The cutoff determination unit is used to determine whether the current charging is cut off when the negative parameter potential is less than zero;

[0048] The reduction unit is used to, when the current charging is stopped when the negative parameter potential is less than zero, place the target lithium battery in a resting position for a preset resting time, and reduce the charging voltage according to the set voltage value, and then continue to charge the target lithium battery until the charging current is less than the target current or the negative parameter potential is less than zero, and then return to the cutoff judgment unit.

[0049] The termination unit is used to terminate the test of the voltage to be tested when the current charging current is less than the target current and the charging is stopped.

[0050] The recording unit is used to record the charging duration of this test without reducing the overvoltage, so as to obtain the charging duration of the voltage to be tested.

[0051] Optionally, the above-mentioned battery charging method analysis device further includes:

[0052] The formulation unit is used to formulate the charging voltage MAP of the target lithium battery in the temperature range by using the set small current and the constant voltage charging voltage at each of the test temperatures.

[0053] This application provides an analysis method for battery charging methods. For each test voltage, a target lithium battery is charged to a set initial capacity using a small current. Then, constant voltage charging is applied to the target lithium battery using the test voltage until the charging current is less than the target current or the negative parameter potential is less than zero. The target current is the current characterizing a fully charged battery. This allows the determination of the voltage at which constant voltage charging is possible without lithium plating. Then, among the test voltages where charging to the point where the current is less than the target current is stopped, the test voltage with the shortest charging time is determined as the optimal constant voltage, thus determining the constant voltage voltage with the shortest charging time. Next, the target lithium battery is charged to each test initial capacity using a small current, and then fully charged using the optimal constant voltage. The test initial capacity with the shortest charging time is determined as the optimal charging initial capacity, thus determining the initial capacity for constant voltage charging. Finally, for each test temperature, the target lithium battery is left to stand at the test temperature for a set time, then charged to the optimal charging initial capacity using a small current, and then charged using the current optimal constant voltage. If the target lithium battery cannot be fully charged using the current optimal constant voltage, then the target lithium battery is left to stand at room temperature for a preset time, discharged at a set rate, and the current optimal constant voltage is reduced by a set margin. The process then returns to the previous step of leaving the target lithium battery at the test temperature for a set time. If the target lithium battery is fully charged using the current optimal constant voltage, then this optimal constant voltage is determined as the constant voltage charging voltage at the test temperature. This determines the optimal constant voltage charging voltage at each temperature, i.e., the constant voltage charging voltage with the shortest charging time. This provides information on a constant voltage charging method that can fully utilize the maximum charging capacity, effectively reducing charging time and preventing problems such as lithium deposition or dendrite growth. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0055] Figure 1 A flowchart illustrating an analysis method for a battery charging method provided in an embodiment of this application;

[0056] Figure 2 A flowchart illustrating a method for preparing a target lithium battery, as provided in an embodiment of this application;

[0057] Figure 3A schematic diagram of the rate and negative parameter curves of various constant voltage charging methods provided in the embodiments of this application;

[0058] Figure 4 A schematic diagram of the rate and negative parameter curves of the initial SOC at different constant voltages provided in an embodiment of this application;

[0059] Figure 5 A schematic diagram of the magnification and negative parameter curves at different temperatures provided in an embodiment of this application;

[0060] Figure 6 A schematic diagram showing the comparison curves of stepped constant current charging and constant voltage charging provided for embodiments of this application;

[0061] Figure 7 A schematic diagram of a charging voltage MAP provided in an embodiment of this application;

[0062] Figure 8 This is a schematic diagram of the architecture of an analysis device for a battery charging method provided in an embodiment of this application. Detailed Implementation

[0063] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0064] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] This application provides a method for analyzing battery charging methods, such as... Figure 1 As shown, it includes the following steps:

[0066] S101. For each voltage to be tested, charge the target lithium battery to the set initial capacity with a set small current, and then charge the target lithium battery with the voltage to be tested at a constant voltage until the charging current is less than the target current or the negative parameter potential is less than zero.

[0067] The target current is the current characterizing a fully charged battery, specifically 0.05C0. The target lithium battery is the lithium battery to be analyzed, specifically a lithium iron phosphate battery.

[0068] In this embodiment, a constant voltage charging method is used to analyze the relevant charging data of the battery's maximum charging capacity. Therefore, by conducting charging tests on various voltages, the voltage that can be charged to full capacity with constant voltage and has the shortest charging time is investigated, so as to obtain the fastest constant charging voltage.

[0069] It's important to note that because the battery voltage is low when the State of Charge (SOC) is low, the difference between this voltage and the constant-voltage charging voltage is significant, resulting in a large charging current (I=U / R). This means the current during constant-voltage charging gradually decreases, reaching its maximum at the beginning. To allow lithium ions to slowly intercalate and open the lithium intercalation channels in the graphite, the battery needs to be charged to a certain SOC with a smaller current first. In other words, the target lithium battery is first charged to a set initial capacity with a small current before constant-voltage charging begins. This reduces lithium plating, decreases polarization voltage, and makes the actual battery voltage closer to the theoretical voltage, thus minimizing energy loss.

[0070] Optionally, the low current can be selected from the current range of 0.1C0 to 0.5C0, where C0 is the target lithium battery's rated capacity. The initial capacity can be selected from 10% of the battery's state of charge (SOC), for example, 2% SOC.

[0071] After charging the target lithium battery to a set initial capacity using a set small current, constant voltage charging is then performed on the target lithium battery at the voltage to be tested. To promptly stop charging after full charge and determine the time required for full charge, the charging current needs to be monitored in real time in this embodiment. Charging is stopped when the monitored charging current is less than the target current indicating a full charge, and the charging time is obtained to determine the charging duration of the voltage to be tested. Furthermore, considering charging safety, this application aims to prevent lithium deposition during constant voltage charging. Therefore, the negative parameter potential is monitored during constant voltage charging. When the negative parameter potential is detected to be less than zero, it indicates lithium deposition, and the voltage to be tested is unusable for charging. Therefore, further charging is not necessary, and charging should be stopped at this point. This improves detection efficiency and avoids wasting detection resources.

[0072] Optionally, in order to avoid analyzing a large number of test voltages and thus speed up the analysis, in another embodiment of this application, before performing step S101, the following is further included:

[0073] Determine the stable voltage of the target lithium battery during the initial stage of constant current charging, and within the set range corresponding to the stable voltage, select the stable voltage and select multiple voltages at set intervals as the voltages to be tested.

[0074] The inventors discovered that the stable voltage during the initial stage of constant current charging of the target lithium battery, and the voltage near it, are most likely the voltages for the most efficient constant voltage charging. Therefore, they determined the stable voltage during the initial stage of constant current charging of the target lithium battery, and within a set range corresponding to the stable voltage, selected voltages and multiple voltages at set intervals as test voltages. The initial stage of constant current charging refers to the period before the preset state of charge (SOC). For example, based on the voltage curve of constant current charging, the voltage is basically stable at around 3.5V during the first 80% SOC; therefore, the stable voltage is determined to be 3.5V. Voltages near 3.5V are selected for constant voltage charging to explore the optimal charging voltage. Selecting multiple test voltages within the range of 3.5 ± 0.03V improves analysis efficiency and saves testing resources.

[0075] Since the target lithium battery's fixed capacity and negative parameter potential need to be measured in this embodiment, optionally, in another embodiment, the target lithium battery is prepared before performing step S101. Figure 2 As shown in the embodiment of this application, a method for preparing a target lithium battery includes:

[0076] S201. Insert copper wires into the stack or core of the target lithium battery and separate the copper wires from the positive and negative electrodes of the target lithium battery to form the three electrodes of the target lithium battery.

[0077] Specifically, copper wires are embedded as three electrodes during the fabrication of the target lithium battery core or stack. Optionally, the copper wires are embedded between the positive and negative electrodes in the penultimate layer of the stack or core, and are separated from the positive and negative electrodes. The position of the penultimate layer can better reflect the overall electrochemical behavior of the battery. Since the electrode reactions occur gradually from the outer layer to the inner layer during charging and discharging, the position of the penultimate layer can better balance the electrochemical reaction characteristics of the outer and inner layers, thus providing more representative electrode potential data.

[0078] S202. Connect the target lithium battery to the charger and perform lithium plating on both sides of the copper wire.

[0079] It should be noted that after lithium is plated on the surface of the copper wire, the potential of the three electrodes becomes the potential of lithium. Therefore, when lithium is deposited on the surface of the negative electrode, the potential difference between the negative electrode and the three electrodes is <0V. Thus, by monitoring the potential between the negative electrode and lithium, i.e., monitoring the negative parameter potential, it can be determined whether lithium is deposited during the battery charging process.

[0080] Alternatively, a small current can be used to plate the copper wire with lithium, for example, a current ≤50μA can be used and lithium plating can be performed with a charging time of 2-8h.

[0081] S203. At room temperature, the target lithium battery is subjected to a set current to determine its constant capacity.

[0082] Optionally, the battery can be calibrated at a low current for 3 weeks at room temperature according to a set current, and the discharge capacity of the third week can be taken as the calibrated capacity C0.

[0083] S102. Among the various test voltages that are charged to a point where the current is less than the target current and then cut off, the test voltage with the shortest charging time is determined as the optimal constant voltage.

[0084] It's important to note that constant-voltage charging is performed using a test voltage until the current falls below the target current, not until the negative parameter potential drops below zero. Therefore, this test voltage allows the target lithium battery to be charged to full capacity using a constant voltage, thus obtaining the charging time corresponding to the test voltage. The charging method analysis aims to determine the charging method with the maximum charging capacity, i.e., the fastest charging method. Therefore, the test voltage with the shortest charging time among all the test voltages that stop charging when the current falls below the target current is selected as the optimal constant voltage. Simultaneously, the negative parameter potential is monitored. If the negative parameter potential is below zero, charging is stopped to prevent lithium plating. However, at this point, the test voltage is no longer the optimal constant voltage.

[0085] Since step-down voltage reduction better aligns with the battery's charging behavior when setting constant-voltage charging, and allows for investigation of whether the charging curve changes with the next voltage, for example, starting with a voltage of 3.5V and 3.51V (the initial voltage being the stable voltage), and then reducing the voltage to 3.5V or 3.51V after charging to the set initial capacity, it's possible to investigate whether the current changes at the two constant-voltage charging voltages are consistent, leading to a better understanding of constant-voltage charging. Therefore, optionally, in another embodiment of this application, a step-down voltage reduction method is used for investigation. Thus, in another embodiment of this application, after executing step S101, the following is further included:

[0086] Determine whether the current charging is stopped when the negative parameter potential is less than zero.

[0087] If the current charging is stopped when the negative parameter potential is less than zero, the target lithium battery is left to stand for a preset standing time, and the charging voltage is reduced according to the set voltage value. Then the target lithium battery is continued to be charged until the charging current is less than the target current or the negative parameter potential is less than zero. Then the system returns to determine whether the current charging is stopped when the negative parameter potential is less than zero.

[0088] If the current charging current is less than the target current and the charging is stopped, then the test of the voltage to be tested ends.

[0089] If the overvoltage is not reduced, record the charging time for this test to obtain the charging time of the voltage to be tested.

[0090] This means that the voltage to be tested is used as the initial charging voltage to begin constant voltage charging. If a negative parameter potential falls below zero, charging is stopped to avoid lithium plating. The target lithium battery is then allowed to rest for a preset time, and the charging voltage is reduced according to the set voltage value before continuing constant voltage charging. If a negative parameter potential falls below zero again, charging is again stopped, and the target lithium battery is allowed to rest for a preset time before the charging voltage is reduced according to the set voltage value before continuing constant voltage charging. This process of continuously reducing the voltage continues until the charging current falls below the target current, at which point charging is stopped, and no further voltage reduction is needed. This allows the same test to be performed on the next voltage to be tested.

[0091] Optionally, the preset rest period can be 1 second to improve detection efficiency. It should be noted that the reason for choosing a rest period is that if the battery is set to charge at 3.51V, directly switching to 3.5V charging would prevent it from continuing to charge at 3.5V. Therefore, adding a rest period allows the battery voltage to drop rapidly. Then, switching back to 3.5V charging at this point creates a voltage difference, allowing charging to continue.

[0092] Alternatively, because the voltage plateau of lithium iron phosphate batteries is relatively stable, a change of 0.01V already results in a significant difference, so a voltage setting of 0.01V can be selected. Of course, voltage changes can also be 0.005V, 0.015V, or 0.02V, etc., usually selected within the range of 0.005V to 0.02V, in order to explore a more precise optimal charging voltage and improve analytical accuracy.

[0093] It should also be noted that if a single target lithium battery is used to test each voltage in sequence, the battery must be discharged after each voltage is tested, for example, discharged at 0.33C, before testing the next voltage.

[0094] For example, taking a 218Ah LFP three-electrode pouch cell as an example, after three cycles of charge-discharge at 0.33C to achieve a constant capacity, the third discharge capacity of 220Ah was obtained. The following tests were then performed on the four voltages to be tested:

[0095] 1. Charge at 73.3A (0.33C0) for 3.6 minutes, setting the initial capacity to 2% SOC. Then charge at a constant voltage of 3.49V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, adjust the charging voltage to a constant voltage of 3.48V, again with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.47V. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.46V. If the charge is cut off when the charging current <0.05C0, end the charging and discharge at 0.33C.

[0096] 2. Charge at 73.3A (0.33C0) for 3.6 minutes, then charge at a constant voltage of 3.5V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.49V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.48V. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.47V. If the charge is cut off when the charging current <0.05C0, end the charging process and discharge at 0.33C.

[0097] 3. Charge at 73.3A (0.33C0) for 3.6 minutes, then charge at a constant voltage of 3.51V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.50V, again with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.49V. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.48V. If the charge is cut off when the charging current <0.05C0, end the charging process and discharge at 0.33C.

[0098] 4. Charge at 73.3A (0.33C0) for 3.6 minutes, then charge at a constant voltage of 3.52V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.51V, with the charging current <0.05C0 or the negative parameter potential reaching 0V as the cutoff condition. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.50V. If the charge is cut off at the negative parameter potential of 0V, after resting for 1 second, charge at a constant voltage of 3.49V. If the charge is cut off when the charging current <0.05C0, end the charging process and discharge at 0.33C.

[0099] The charging time curves during the aforementioned test process, specifically the rate and negative parameter curves for each constant voltage charging step, are as follows: Figure 3 As shown in the table below, the specific charging data is shown in Table 1. Therefore, it can be seen that constant voltage charging at 3.49V and 3.5V can be used for the entire SOC range. However, 3.51V and 3.52V both exhibit negative parameter potentials (<0V) during constant voltage charging, so these two voltages cannot be used for charging the entire SOC. Since the charging time at 3.5V is shorter, the optimal charging voltage is determined to be 3.5V.

[0100] Table 1

[0101]

[0102] S103. After charging the target lithium battery to the initial capacity of each test using a set small current, the target lithium battery is fully charged with constant voltage using the optimal constant voltage.

[0103] It should be noted that the initial capacity set is only a rough estimate, intended to determine the optimal constant voltage. After determining the optimal constant voltage, the optimal initial capacity still needs to be analyzed. Therefore, multiple initial capacities to be tested are selected, such as 5%, 8%, 10%, and 15% SOC. Then, the target lithium battery is charged to each of these initial capacities using a set small current, followed by constant voltage charging at the optimal constant voltage until fully charged. The charging time corresponding to each initial capacity to be tested can then be obtained. The initial capacity to be tested is greater than the set initial capacity to improve the detection range and enhance the reliability of the analysis.

[0104] It should be noted that setting the optimal constant voltage for initial capacity analysis is the foundation of the entire analysis process. After determining the optimal constant voltage, the charging efficiency at different initial SOCs is tested to ensure that constant voltage charging from that point can be completed most efficiently.

[0105] S104. The initial capacity to be tested with the shortest charging time is determined as the optimal initial charging capacity.

[0106] Similarly, what needs to be analyzed is the charging method with the shortest charging time. Therefore, the starting capacity to be tested with the shortest charging time is determined as the optimal starting charging capacity.

[0107] For example, using the above example, we select initial capacities of 5%, 8%, 10%, and 15% SOC for testing. The specific testing process is as follows: 1. Charge at 73.3A for 9 minutes to charge the battery to 5% SOC, then charge at 3.5V at a constant voltage to full charge, followed by constant current discharge at 0.33C to facilitate the next initial capacity test. 2. Charge at 73.3A for 14.4 minutes to charge the battery to 8% SOC, then charge at 3.5V at a constant voltage to full charge, and finally discharge at 0.33C at a constant current. 3. Charge at 73.3A for 18 minutes to charge the battery to 10% SOC, then charge at 3.5V at a constant voltage to full charge, and finally discharge at 0.33C at a constant current. 4. Charge at 73.3A for 27 minutes to charge the battery to 15% SOC, then charge at 3.5V at a constant voltage to full charge, and finally discharge at 0.33C at a constant current.

[0108] Correspondingly, the obtained charging time curve is as follows: Figure 4 The table shows the rate of return and negative parameter curves for different initial SOCs during constant voltage charging. The corresponding charging data and stepped constant current data are shown in Table 2. According to these data, the charging time is shortest with an initial constant voltage SOC of 5%, therefore 5% SOC is the optimal initial SOC for constant voltage charging. Similarly, as shown in Table 2, at 25℃, the lowest negative parameter potential for stepped constant current fast charging is 4.66mV, lower than the negative parameter unit (28.97mV) for constant voltage charging with an initial SOC of 5%. This means that the stepped constant current charging method at 25℃ has reached its maximum charging capacity within the negative parameter tolerance range. However, the charging time for constant voltage charging with an initial SOC of 5% in the 5%~90% SOC fast charging range is 10.61% shorter than the stepped constant current charging time = (2223-1987) / 2223. Constant voltage charging can shorten the battery charging time; that is, selecting an appropriate initial capacity for constant voltage charging can improve charging efficiency and avoid lithium plating.

[0109] Table 2

[0110]

[0111] S105. For each test temperature, after the target lithium battery has been left to stand at the test temperature for a set time, the target lithium battery is charged to the optimal charging start capacity with a set small current, and the target lithium battery is charged with constant voltage using the current optimal constant voltage.

[0112] It should be noted that ambient temperature affects charging, and the previously determined optimal constant voltage was tested at a single temperature, typically room temperature (25°C). However, in reality, charging involves various ambient temperatures. To investigate the applicability of the optimal charging voltage under different temperatures and to adjust the charging voltage accordingly, specific temperatures that might be encountered in actual environments are tested.

[0113] Therefore, the target lithium battery is first placed at the test temperature for a set time, such as 2 hours, to ensure that its temperature reaches the test temperature, thus ensuring temperature balance and improving test accuracy before starting the test. Next, the target lithium battery is charged to its optimal initial charging capacity using a set small current, and then constant voltage charging is performed using the current optimal constant voltage.

[0114] S106. Determine whether the target lithium battery should be charged to full capacity using the current optimal constant voltage.

[0115] If the target lithium battery cannot be fully charged using the current optimal constant voltage, it indicates that the current optimal constant voltage is too high at the test temperature, preventing the target lithium battery from being fully charged. Therefore, the test needs to be repeated, and step S107 is executed. If the target lithium battery can be fully charged using the current optimal constant voltage, it indicates that the current optimal constant voltage is usable, and step S109 is executed.

[0116] S107. After the target lithium battery has been left to stand at room temperature for a preset time, discharge it at the set rate.

[0117] Since a retest is required, the battery must first be fully discharged at the set charging rate. During the previous charging process, the lithium battery may have been at high or low temperatures, which could affect subsequent tests. For example, if the test temperature is low, directly discharging the lithium battery at this low temperature would result in significant battery polarization, preventing the battery from reaching its full capacity. Therefore, the target lithium battery must be allowed to stand at room temperature for a preset time before the next test. The preset standing time at the test temperature and the preset standing time at room temperature can be the same or different, depending on the requirements.

[0118] S108. Adjust the current optimal constant voltage according to the set range.

[0119] It should be noted that since the current optimal constant voltage is too high, it needs to be lowered, for example, by 0.01V. Then, the voltage after the lowering needs to be tested. Therefore, it is necessary to return to step S105 at this point. The set range can be set as needed, and this application does not impose any restrictions. However, to improve the analysis accuracy, the set range can be set to a smaller value.

[0120] S109. Determine the current optimal constant voltage as the constant voltage charging voltage at the test temperature.

[0121] Since the current optimal constant voltage determined at this time can charge the battery to full capacity normally at the test temperature, it is determined as the constant voltage charging voltage at the test temperature.

[0122] Temperature has a significant impact on battery performance, and charging strategies need to be adjusted at different temperatures to ensure charging efficiency and safety. In this application, the optimal charging voltage is initially determined, followed by the optimal initial charging capacity to optimize the charging strategy. Furthermore, the constant-voltage charging voltage at different temperatures is determined, applicable to different application scenarios. These three steps are closely linked and interdependent, allowing for the exploration of the battery's maximum charging capacity at different temperatures, thereby improving charging efficiency and safety. For example, using the above example, since data at 25°C has already been obtained in the previous tests, data at 0°C and -10°C are obtained as follows:

[0123] 1. Let the battery stand at 0℃ for 2 hours, then charge at 73.3A for 9 minutes to reach 5% SOC (State of Charge). Continue charging at a constant voltage of 3.5V until fully charged. Then let it stand at 25℃ for 2 hours, and finally discharge it completely at 0.33C. 2. Let the battery stand at -10℃ for 2 hours, then charge at 73.3A for 9 minutes, followed by a constant voltage charge of 3.5V until fully charged. Then let it stand at 25℃ for 2 hours, and finally discharge it completely at 0.33C.

[0124] The corresponding charging time curve is as follows Figure 5 As shown, the magnification and negative parameter curves at different temperatures are as follows: Figure 5 As shown, the corresponding charging data is shown in Table 3. From Figure 5 As shown in Table 3, at 0℃, the charging time of constant voltage charging within the 5%~90% SOC range is 33.31% shorter than that of stepped constant current charging. At -10℃, the charging time of constant voltage charging within the 5%~90% SOC range is 42% shorter than that of stepped constant current charging. Specifically, the comparison curves between stepped constant current charging and constant voltage charging at low temperatures are shown below. Figure 6 As shown. At 0℃, the minimum negative parameter potential for stepped constant current is 34.34mV, and the minimum negative parameter for constant voltage is 12.09mV. The stepped constant current charging current of this 0℃ design is relatively conservative and does not reach the battery's maximum charging capacity. On the other hand, constant voltage charging maintains a large current when the negative parameter is >0V, thus maximizing the battery's maximum charging capacity. The same principle applies to stepped constant current at -10℃.

[0125] Maximum battery charging capacity: Under the premise of no lithium plating (negative parameter potential > 0V), the battery's charging current reaches its maximum. The larger the charging current, the smaller the negative parameter potential. When the charging current exceeds the battery's capacity, the negative parameter potential < 0V, and lithium plating occurs. The relatively high negative parameter at 0℃ with stepped constant current indicates that the designed charging current is too small, failing to utilize the battery's charging capacity.

[0126] Table 3

[0127]

[0128] Optionally, in another embodiment of this application, one specific implementation of step S109 includes:

[0129] By setting a small current and a constant voltage charging voltage at various test temperatures, the charging voltage MAP of the target lithium battery over the temperature range is determined.

[0130] To facilitate subsequent use, the constant voltage charging voltages at various test temperatures were summarized and analyzed to formulate the MAP of the charging voltage for the target lithium battery temperature range.

[0131] For example, taking the example above, 3.5V can complete charging within the full SOC range at -10℃, 0℃, and 25℃, thus proving that constant voltage charging with 3.5V can be used within the range of -10℃ to 25℃. Therefore, the established charging voltage MAP can be as follows: Figure 7 As shown.

[0132] This application provides an analysis method for battery charging methods. For each test voltage, a target lithium battery is charged to a set initial capacity using a small current. Then, the target lithium battery is charged at a constant voltage using the test voltage until the charging current is less than the target current or the negative parameter potential is less than zero. The target current is the current representing a fully charged battery. This allows the determination of the voltage at which constant voltage charging is possible without lithium plating. Then, among the test voltages where charging stops when the current is less than the target current, the test voltage with the shortest charging time is determined as the optimal constant voltage, thus determining the constant voltage voltage with the shortest charging time. Then, the target lithium battery is charged to each test initial capacity using a small current, and then fully charged at a constant voltage using the optimal constant voltage. The test initial capacity with the shortest charging time is determined as the optimal charging initial capacity, thus determining the initial capacity for constant voltage charging. Then, for each test temperature, the target lithium battery is left to stand at the test temperature for a set time, and then charged to the optimal initial charging capacity with a set small current. The target lithium battery is then charged at a constant voltage using the current optimal constant voltage. If the target lithium battery cannot be fully charged at the current optimal constant voltage, it is left to stand at room temperature for a preset time, discharged at a set rate, and the current optimal constant voltage is reduced by a set margin. The process then returns to leaving the target lithium battery at the test temperature for the set time. If the target lithium battery is fully charged at the current optimal constant voltage, this current optimal constant voltage is determined as the constant voltage charging voltage at the test temperature. This determines the optimal constant voltage charging voltage for each temperature, i.e., the constant voltage charging voltage with the shortest charging time. This provides information on a constant voltage charging method that can fully utilize the maximum charging capacity, effectively reducing charging time and avoiding problems such as lithium deposition or dendrite growth.

[0133] Another embodiment of this application provides a battery charging mode analysis device, such as... Figure 8 As shown, it includes:

[0134] The first voltage testing unit 801 is used to charge the target lithium battery to a set initial capacity with a small current for each voltage to be tested, and then charge the target lithium battery with a constant voltage at the voltage to be tested until the charging current is less than the target current or the negative parameter potential is less than zero. The target current is the current that characterizes when the battery is fully charged.

[0135] The first voltage determination unit 802 is used to determine the test voltage with the shortest charging time among the various test voltages that are cut off when the charging current is less than the target current as the optimal constant voltage.

[0136] The capacity testing unit 803 is used to charge the target lithium battery to each initial capacity to be tested with a set small current, and then fully charge the target lithium battery with a constant voltage at the optimal constant voltage.

[0137] The capacity determination unit 804 is used to determine the initial capacity to be tested with the shortest charging time as the optimal initial charging capacity.

[0138] The second voltage testing unit 805 is used to, for each test temperature, place the target lithium battery at the test temperature for a set time, charge the target lithium battery with a set small current to the optimal charging start capacity, and perform constant voltage charging on the target lithium battery with the current optimal constant voltage.

[0139] The reset processing unit 806 is used to discharge the target lithium battery at a set rate after letting it stand at room temperature for a preset time when the target lithium battery cannot be charged to full capacity at the current optimal constant voltage.

[0140] The down-adjustment unit 807 is used to reduce the current optimal constant voltage by a set amount and return it to the temperature test unit.

[0141] The second voltage determination unit 808 is used to determine the current optimal constant voltage as the constant voltage charging voltage at the test temperature if the target lithium battery is charged to full capacity at the current optimal constant voltage.

[0142] Optionally, in another embodiment of the battery charging method analysis device provided in this application, the device further includes:

[0143] An electrode implantation unit is used to implant copper wires into the stack or core of a target lithium battery and to separate the copper wires from the positive and negative electrodes of the target lithium battery, forming the three electrodes of the target lithium battery.

[0144] The lithium plating unit is used to connect the target lithium battery into the charger and perform positive and negative lithium plating on the copper wire.

[0145] The capacity calibrator is used to calibrate the target lithium battery at room temperature according to a set current, thereby determining the calibrated capacity of the target lithium battery.

[0146] Optionally, in another embodiment of the battery charging method analysis device provided in this application, the device further includes:

[0147] The third voltage determination unit is used to determine the stable voltage of the target lithium battery during the early stage of constant current charging.

[0148] The selection unit is used to select a stable voltage within a set range corresponding to the stable voltage, and to select multiple voltages at set intervals as the voltages to be tested.

[0149] Optionally, in another embodiment of the battery charging method analysis device provided in this application, the device further includes:

[0150] The cutoff judgment unit is used to determine whether the current charging is cut off when the negative parameter potential is less than zero.

[0151] The reduction unit is used to, when charging is currently stopped when the negative parameter potential is less than zero, place the target lithium battery in a resting state for a preset resting time, reduce the charging voltage according to the set voltage value, and then continue charging the target lithium battery until the charging current is less than the target current or the negative parameter potential is less than zero, and then return to the cutoff judgment unit.

[0152] The termination unit is used to end the test of the voltage under test when the current charging current is less than the target current and the charging is stopped.

[0153] The recording unit is used to record the charging duration of this test without reducing the overvoltage, so as to obtain the charging duration of the voltage to be tested.

[0154] Optionally, in another embodiment of the battery charging method analysis device provided in this application, the device further includes:

[0155] The specification unit is used to specify the charging voltage MAP of the target lithium battery within a specific temperature range by using a set small current and a constant voltage charging voltage at various test temperatures.

[0156] It should be noted that the specific working process of each unit provided in the above embodiments of this application can be referred to the implementation process of the corresponding steps in the above method embodiments, and will not be repeated here.

[0157] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0158] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for analyzing battery charging methods, characterized in that, include: For each voltage to be tested, the target lithium battery is charged to the set initial capacity with a set small current, and then the target lithium battery is charged with constant voltage at the voltage to be tested until the charging current is less than the target current or the negative parameter potential is less than zero; wherein, the target current is the current that characterizes the battery when it is fully charged; Among the various test voltages that are charged to a point where the current is less than the target current and then cuts off, the test voltage with the shortest charging time is determined as the optimal constant voltage. After charging the target lithium battery to its respective initial capacity for testing with the set small current, the target lithium battery is fully charged with the optimal constant voltage. The initial capacity to be tested with the shortest charging time is determined as the optimal initial charging capacity; For each test temperature, the target lithium battery is left to stand at the test temperature for a set time, then charged to the optimal charging start capacity with the set small current, and then charged with constant voltage using the current optimal constant voltage. If the target lithium battery cannot be fully charged using the current optimal constant voltage, then the target lithium battery is left to stand at room temperature for a preset time and then discharged at a set rate. The current optimal constant voltage is reduced by a set margin, and the process returns to the step of placing the target lithium battery at the test temperature for a set duration. If the target lithium battery is charged to full capacity using the current optimal constant voltage, then the current optimal constant voltage is determined as the constant voltage charging voltage at the test temperature.

2. The method according to claim 1, characterized in that, Also includes: Copper wires are implanted into the stack or core of the target lithium battery, and the copper wires are separated from the positive and negative electrodes of the target lithium battery to form the three electrodes of the target lithium battery. The target lithium battery is connected to a charger, and the copper wire is subjected to lithium plating on both sides. The target lithium battery is subjected to a set current at room temperature to determine its constant capacity.

3. The method according to claim 1, characterized in that, Also includes: Determine the stable voltage of the target lithium battery during the initial stage of constant current charging; Within the set range corresponding to the stable voltage, the stable voltage and multiple voltages selected at set intervals are used as the voltage to be tested.

4. The method according to claim 1, characterized in that, After charging the target lithium battery to a set initial capacity with a set small current, the process further includes constant voltage charging of the target lithium battery with the test voltage until the charging current is less than the target current or the negative parameter potential is less than zero. Determine whether the current charging is stopped when the negative parameter potential is less than zero; If the current charging is stopped when the negative parameter potential is less than zero, the target lithium battery is left to stand for a preset standing time, and the charging voltage is reduced according to the set voltage value. Then the target lithium battery is continued to be charged until the charging current is less than the target current or the negative parameter potential is less than zero. Then the process returns to the step of determining whether the current charging is stopped when the negative parameter potential is less than zero. If the current charging is cut off when the charging current is less than the target current, then the test of the voltage to be tested ends. If the overvoltage is not reduced, record the charging time of this test to obtain the charging time of the voltage to be tested.

5. The method according to claim 1, characterized in that, Also includes: Using the set small current and the constant voltage charging voltage at each of the test temperatures, the temperature range charging voltage MAP of the target lithium battery is determined.

6. An analysis device for battery charging methods, characterized in that, include: The first voltage testing unit is used to charge the target lithium battery to a set initial capacity with a set small current for each voltage to be tested, and then charge the target lithium battery with the voltage to be tested at a constant voltage until the charging current is less than the target current or the negative parameter potential is less than zero; wherein, the target current is the current characterizing the battery when it is fully charged. The first voltage determination unit is used to determine the test voltage with the shortest charging time among the various test voltages that are cut off when the charging current is less than the target current as the optimal constant voltage. The capacity testing unit is used to charge the target lithium battery to each initial capacity to be tested using the set small current, and then fully charge the target lithium battery at the optimal constant voltage. The capacity determination unit is used to determine the initial capacity to be tested with the shortest charging time as the optimal charging starting capacity. The second voltage testing unit is used to, for each test temperature, place the target lithium battery at the test temperature for a set time, charge the target lithium battery with a set small current to the optimal charging start capacity, and perform constant voltage charging on the target lithium battery with the current optimal constant voltage. The reset processing unit is used to discharge the target lithium battery at a set rate after the target lithium battery has been left to stand at room temperature for a preset time when the target lithium battery cannot be charged to full capacity at the current optimal constant voltage. The down-adjustment unit is used to reduce the current optimal constant voltage by a set amount and return it to the temperature testing unit; The second voltage determination unit is used to determine the current optimal constant voltage as the constant voltage charging voltage at the test temperature if the target lithium battery is charged to full capacity at the current optimal constant voltage.

7. The apparatus according to claim 6, characterized in that, Also includes: An electrode implantation unit is used to implant copper wires into the stack or core of the target lithium battery and to separate the copper wires from the positive and negative electrodes of the target lithium battery to form the three electrodes of the target lithium battery. A lithium plating unit is used to connect the target lithium battery into a charger and perform positive and negative lithium plating on the copper wire; A capacity calibrator is used to calibrate the target lithium battery at room temperature according to a set current, thereby determining the calibrated capacity of the target lithium battery.

8. The apparatus according to claim 6, characterized in that, Also includes: The third voltage determination unit is used to determine the stable voltage of the target lithium battery during the early stage of constant current charging; The selection unit is used to select the stable voltage and select multiple voltages at set intervals within a set range corresponding to the stable voltage as the voltage to be tested.

9. The apparatus according to claim 6, characterized in that, Also includes: The cutoff determination unit is used to determine whether the current charging is cut off when the negative parameter potential is less than zero; The reduction unit is used to, when the current charging is stopped when the negative parameter potential is less than zero, place the target lithium battery in a resting position for a preset resting time, and reduce the charging voltage according to the set voltage value, and then continue to charge the target lithium battery until the charging current is less than the target current or the negative parameter potential is less than zero, and then return to the cutoff judgment unit. The termination unit is used to terminate the test of the voltage to be tested when the current charging current is less than the target current and the charging is stopped. The recording unit is used to record the charging duration of this test without reducing the overvoltage, so as to obtain the charging duration of the voltage to be tested.

10. The apparatus according to claim 6, characterized in that, Also includes: The formulation unit is used to formulate the charging voltage MAP of the target lithium battery in the temperature range by using the set small current and the constant voltage charging voltage at each of the test temperatures.

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