A method and system for improving the dynamic voltage drop during charging of lithium iron phosphate battery packs.

Abstract

This invention proposes a grouping method and system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs. The method includes: charging each battery to a characteristic voltage using a constant current method, then continuing to charge in a constant current method until a charging cutoff voltage is reached, obtaining a first charging capacity corresponding to the characteristic voltage and a second charging capacity corresponding to the charging cutoff voltage; after each battery reaches the charging cutoff voltage, switching to a constant voltage method to continue charging until the battery current drops to the cutoff current, at which point each battery is fully charged and charging stops; discharging each fully charged battery to a discharge cutoff voltage using a constant current method, obtaining the discharge capacity corresponding to the discharge cutoff voltage; grouping all batteries once based on the discharge capacity to obtain at least one initial battery group; and further grouping each initial battery group based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. Using this method can improve battery consistency and reduce the dynamic voltage difference during charging and discharging.

Description

Technical Field

[0001] This invention relates to the field of power grid frequency regulation technology, and in particular to a grouping method and system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs. Background Technology

[0002] Lithium-ion batteries are widely used in various portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. In the production process of lithium-ion batteries, cell pairing is a crucial step that directly affects battery performance and lifespan. The main purpose of cell pairing (also known as battery packing) is to combine cells with similar characteristics to ensure the overall performance of the battery pack.

[0003] Existing lithium-ion battery cell grouping methods primarily involve conducting charge-discharge tests on the cells to obtain electrochemical parameters such as charge-discharge capacity and internal resistance, and then grouping the cells based on these parameters. The specific steps include: first, charging and discharging the cells, and then grouping them according to the discharge test results. However, existing cell grouping methods have some problems. For example, this method only groups cells based on their discharge capacity, without addressing grouping techniques for charging capacity. During the charging and discharging process, the BMS monitors the voltage of each battery connected in series in the battery pack, generally requiring a dynamic voltage difference within 300mV (maximum voltage minus minimum voltage). Existing battery grouping methods can only improve the dynamic voltage difference during discharge, not during charging. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, the first objective of this invention is to propose a grouping method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs, so as to improve the dynamic voltage difference during charging and discharging while improving battery consistency.

[0006] The second objective of this invention is to propose a grouping system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs.

[0007] The third objective of this invention is to provide an electronic device.

[0008] The fourth objective of this invention is to provide a computer-readable storage medium.

[0009] To achieve the above objectives, the first aspect of this invention proposes a method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs, comprising:

[0010] Each battery is charged to a characteristic voltage using a constant current method, and then charged to a charging cutoff voltage using a constant current method. The first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage are obtained.

[0011] After each battery is charged to the charging cutoff voltage, the constant voltage mode is switched to continue charging each battery until the battery current drops to the cutoff current. At this time, each battery is fully charged and charging stops.

[0012] Each fully charged battery is discharged to the discharge cutoff voltage using a constant current method, and the discharge capacity corresponding to the discharge cutoff voltage is obtained.

[0013] Based on the discharge capacity, all batteries are grouped once to obtain at least one initial battery group;

[0014] Each initial battery group is grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs.

[0015] In the method of the first aspect of the present invention, the step of grouping each initial battery group based on the first charging capacity and / or the second charging capacity to obtain multiple target lithium-ion battery packs includes: further grouping each initial battery group based on one of the first charging capacity and the second charging capacity to obtain multiple target lithium-ion battery packs.

[0016] In a method of a first aspect of the present invention, the step of grouping each initial battery group based on the first charging capacity and / or the second charging capacity to obtain multiple target lithium-ion battery packs includes: grouping each initial battery group a second time based on the second charging capacity to obtain multiple intermediate battery groups; and grouping each intermediate battery group a third time based on the first charging capacity to obtain multiple target lithium-ion battery packs.

[0017] In the method of the first aspect of the present invention, the step of determining the characteristic voltage includes: selecting a plurality of experimental lithium-ion batteries, conducting charging experiments on all experimental lithium-ion batteries to determine the capacity range values ​​when charged to different voltages; filtering out the capacity range values ​​that are greater than a set capacity range to obtain a candidate capacity range value set; removing charging voltages equal to the charging cut-off voltage from the charging voltages corresponding to the candidate capacity range value set to obtain a candidate charging voltage set; and selecting one from the candidate charging voltage set as the characteristic voltage.

[0018] In the method of the first aspect of the present invention, the step of grouping all batteries once based on the discharge capacity to obtain at least one initial battery group includes: determining a first gear ratio based on demand; sorting the discharge capacities of all batteries and calculating the difference in discharge capacity between any two batteries; calculating a first ratio based on the discharge capacity difference and the rated capacity of the batteries; and grouping all batteries once based on the first ratio and the first gear ratio to obtain at least one initial battery group.

[0019] In the method of the first aspect of the present invention, the step of grouping each initial battery group based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs includes: determining a corresponding second ratio and a third ratio based on the first charging capacity and / or the second charging capacity and the rated capacity of the battery; and grouping each initial battery group based on the second ratio and / or the third ratio, combined with a corresponding gear ratio, to form multiple target lithium-ion battery packs.

[0020] The method of the first aspect of the present invention further includes: removing batteries corresponding to abnormal points in battery internal resistance, abnormal points in K value, and abnormal points in voltage difference in each target lithium-ion battery pack.

[0021] To achieve the above objectives, a second aspect of the present invention provides a battery pack matching system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs, comprising:

[0022] The capacity control module is used to charge each battery to a characteristic voltage in a constant current mode and then continue to charge it to the charging cutoff voltage in a constant current mode. After each battery is charged to the charging cutoff voltage, it switches to a constant voltage mode to continue charging each battery until the battery current drops to the cutoff current. At this time, each battery is fully charged and charging stops. Then, each fully charged battery is discharged to the discharge cutoff voltage in a constant current mode.

[0023] The acquisition module is used to acquire the first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage, and also to acquire the discharge capacity corresponding to the discharge cutoff voltage.

[0024] The grouping module is used to group all batteries once based on the discharge capacity to obtain at least one initial battery group; and to group each initial battery group based on the first charging capacity and / or the second charging capacity to obtain multiple target lithium-ion battery packs.

[0025] To achieve the above objectives, a third aspect of the present invention provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor; the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory to implement the method proposed in the first aspect of the present invention.

[0026] To achieve the above objectives, a fourth aspect of the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the method proposed in the first aspect of the present invention.

[0027] The present invention provides a grouping method, system, electronic device, and storage medium for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs. This involves charging each battery to a characteristic voltage using a constant current method, then continuing to charge it to a charging cutoff voltage using the same method, obtaining a first charging capacity corresponding to the characteristic voltage and a second charging capacity corresponding to the charging cutoff voltage. After each battery reaches the charging cutoff voltage, charging is switched to a constant voltage method until the battery current drops to the cutoff current, at which point charging stops. The fully charged batteries are then discharged to a discharge cutoff voltage using a constant current method, obtaining the discharge capacity corresponding to the discharge cutoff voltage. Based on the discharge capacity, all batteries are grouped once to obtain at least one initial battery group. Each initial battery group is then further grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. In this case, by combining the discharge capacity corresponding to the discharge cutoff voltage, the first charging capacity corresponding to the characteristic voltage, and the second charging capacity corresponding to the charging cutoff voltage, and grouping all batteries multiple times, both discharge and charging capacities are considered, thus improving the dynamic voltage difference during charging and discharging and enhancing battery consistency.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 This is a schematic flowchart of a method for improving the dynamic voltage difference during charging of a lithium iron phosphate battery pack, provided in an embodiment of the present invention.

[0031] Figure 2 This is a constant current and constant voltage charging curve of a lithium iron phosphate battery provided in an embodiment of the present invention;

[0032] Figure 3 This is a block diagram of a matching system for improving the dynamic voltage difference during charging of a lithium iron phosphate battery pack, provided in an embodiment of the present invention. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] The following describes, with reference to the accompanying drawings, a method and system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs.

[0035] This invention provides a grouping method to improve the dynamic voltage difference during charging of lithium iron phosphate battery packs, thereby improving the dynamic voltage difference during charging and discharging while enhancing battery consistency.

[0036] Figure 1 This is a schematic flowchart of a grouping method for improving the dynamic voltage difference during charging of a lithium iron phosphate battery pack, provided in an embodiment of the present invention.

[0037] like Figure 1 As shown, the grouping method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs includes the following steps:

[0038] Step S101: Charge each battery to its characteristic voltage using constant current and then continue charging to the charging cutoff voltage using constant current to obtain the first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage.

[0039] In step S101, the constant charging current during constant current charging can be selected, but is not limited to, 0.5C.

[0040] In step S101, the characteristic voltage value cannot be higher than the charging cutoff voltage.

[0041] In step S101, the characteristic voltage determination step includes: selecting multiple experimental lithium-ion batteries, conducting charging experiments on all experimental lithium-ion batteries to determine the capacity range values ​​when charged to different voltages; filtering out capacity range values ​​greater than the set capacity range to obtain a candidate capacity range value set; removing charging voltages equal to the charging cutoff voltage from the charging voltages corresponding to the candidate capacity range value set to obtain a candidate charging voltage set; and selecting one from the candidate charging voltage set as the characteristic voltage. For example, the candidate charging voltage set could be [3.5V, 3.75V].

[0042] In step S101, the charging cutoff voltage of the lithium iron phosphate battery pack can be, for example, 3.75V.

[0043] In step S101, the first charging capacity corresponding to charging to a characteristic voltage and the second charging capacity corresponding to charging to a charging cutoff voltage are obtained. Specifically, the first charging capacity is calculated by integration based on the battery's charging current and the charging time from the start of charging to the characteristic voltage. Similarly, the second charging capacity is calculated by integration based on the battery's charging current and the charging time from the start of charging to the charging cutoff voltage.

[0044] Step S102: After each battery is charged to the charging cutoff voltage, switch to constant voltage mode to continue charging each battery until the battery current drops to the cutoff current. At this time, each battery is fully charged and charging stops.

[0045] In step S102, the cutoff current is, for example, 0.05C.

[0046] Step S103: Discharge each fully charged battery to the discharge cutoff voltage using a constant current method, and obtain the discharge capacity corresponding to the discharge cutoff voltage.

[0047] In step S103, the discharge cutoff voltage is, for example, 2.5V.

[0048] In step S103, the discharge capacity corresponding to the discharge cutoff voltage is obtained. The discharge capacity corresponding to this discharge cutoff voltage is the full discharge capacity. The full discharge capacity refers to the capacity released from the start of discharge to the moment when the discharge reaches the discharge cutoff voltage.

[0049] Step S104: Group all batteries once based on their discharge capacity to obtain at least one initial battery group.

[0050] In step S104, all batteries are grouped once based on their discharge capacity to obtain at least one initial battery group, including: determining a first grade ratio based on demand; sorting the discharge capacity of all batteries and calculating the difference in discharge capacity between any two batteries; calculating a first ratio based on the discharge capacity difference and the rated capacity of the batteries; and grouping all batteries once based on the first ratio and the first grade ratio to obtain at least one initial battery group.

[0051] Step S105: Group each initial battery group based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs.

[0052] In step S105, when grouping the initial battery groups based on the first charging capacity and / or the second charging capacity, there are two grouping methods. The first grouping method is to further group the initial battery groups based on one of the first charging capacity and the second charging capacity to obtain multiple target lithium-ion battery packs. The second grouping method is to further group the initial battery groups based on the second charging capacity to obtain multiple intermediate battery groups; and then further group the intermediate battery groups based on the first charging capacity to obtain multiple target lithium-ion battery packs.

[0053] In step S105, each initial battery group is grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. This includes: determining a corresponding second ratio and a third ratio based on the first charging capacity and / or the second charging capacity, and the rated capacity of the battery; and grouping each initial battery group based on the second ratio and / or the third ratio, combined with the corresponding gear ratio, to form multiple target lithium-ion battery packs.

[0054] For the first grouping method: when selecting the first charging capacity for secondary grouping, the first charging capacity corresponds to the second tier ratio; sort the first charging capacity of each initial battery group, and calculate the difference in the first charging capacity of any two batteries in each initial battery group; calculate the second ratio based on the difference in the first charging capacity and the rated capacity of the battery; and perform secondary grouping of each initial battery group based on the second ratio and the second tier ratio to obtain multiple target lithium-ion battery packs.

[0055] For the first grouping method: when selecting the second charging capacity for secondary grouping, the second charging capacity corresponds to the third tier ratio; sort the second charging capacity of each initial battery group, and calculate the difference in the second charging capacity of any two batteries in each initial battery group; calculate the third ratio based on the difference in the second charging capacity and the rated capacity of the battery; and perform secondary grouping of each initial battery group based on the third ratio and the third tier ratio to obtain multiple target lithium-ion battery packs.

[0056] For the second grouping method: sort the second charging capacity of each initial battery group, and calculate the difference in second charging capacity between any two batteries in each initial battery group; calculate a third ratio based on the second charging capacity difference and the battery's rated capacity; group each initial battery group a second time based on the third ratio and the third grade ratio to obtain multiple intermediate battery groups; sort the first charging capacity of each intermediate battery group, and calculate the difference in first charging capacity between any two batteries in each intermediate battery group; calculate a second ratio based on the first charging capacity difference and the battery's rated capacity; group each intermediate battery group a third time based on the second ratio and the second grade ratio to obtain multiple target lithium-ion battery packs.

[0057] In embodiments of the present invention, the grouping method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs further includes: eliminating batteries corresponding to abnormal points in battery internal resistance, abnormal points in K value, and abnormal points in voltage difference from each target lithium-ion battery pack. The normal range for battery internal resistance is, for example, 0.3 ± 0.05 mΩ, and the normal range for K value (lithium battery self-discharge rate) is, for example, ≤ 0.05 mV / h.

[0058] In embodiments of the present invention, the process of eliminating batteries corresponding to abnormal voltage difference points specifically includes: after each battery is discharged to the discharge cutoff voltage, it is charged to a set state of charge; the voltage difference between any two batteries in each target lithium-ion battery pack is obtained when each battery is charged to the set state of charge; and abnormal batteries in each target lithium-ion battery pack whose voltage difference exceeds the set voltage difference are eliminated. Specifically, to improve battery performance and stability, after discharging to the discharge cutoff voltage, each lithium-ion battery is left to stand for a certain period of time before being charged to the set state of charge. The set state of charge is, for example, 30% SOC (state of charge), and the set voltage difference is, for example, 5mV. That is, in each target lithium-ion battery pack, a voltage difference ≤ 5mV is considered a normal battery, and a voltage difference > 5mV is considered an abnormal battery.

[0059] In the embodiments of the invention, the target lithium-ion battery packs are connected in series to obtain the corresponding battery packs.

[0060] Taking a constant charging current of 0.5C, a characteristic voltage of 3.6V, and two-stage grouping as an example, the grouping method of the present invention for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs includes the following steps:

[0061] 1) Select a batch of new lithium batteries with the same model and specifications to better ensure the consistency and accuracy of the experiment.

[0062] 2) Perform the capacity grading process on this batch of lithium batteries. Specifically: Charge the batteries with a constant current of 0.5C until the battery voltage reaches the characteristic voltage of 3.6V. Continue charging with a constant current of 0.5C until the battery voltage reaches 3.75V, which is the charging cutoff voltage. Then, switch the charging mode to constant voltage charging and continue charging until the battery current drops to 0.05C, which is the cutoff current.

[0063] 3) Select a charging cutoff voltage V1 of 3.75V. At this voltage, collect the charging capacity C1 (i.e., the second charging capacity) corresponding to the constant current charging to the charging cutoff voltage V1. This charging capacity C1 is obtained by recording the battery charging current and charging time from the start of charging to the charging cutoff voltage V1 through the battery testing system, and then calculating the charging capacity C1 by integration.

[0064] 4): It is also possible to collect the charging capacity C3 (i.e., the first charging capacity) corresponding to the constant current charging to the characteristic voltage V3.

[0065] 5) Discharge the fully charged battery using a constant current until the battery voltage drops to 2.5V, which is the discharge cutoff voltage V2. Then, collect the discharge capacity C2 corresponding to the discharge cutoff voltage V2. Specifically, using a battery testing system, record the battery's discharge current and discharge time from the start of discharge until the discharge cutoff voltage V2, and then calculate the discharge capacity C2 through integration.

[0066] 6) Group the batteries by discharge capacity C2. Specifically, sort all batteries by discharge capacity C2, and then group batteries with similar discharge capacities together. For example, based on demand, determine the range ratio to be 1%; sort all batteries by discharge capacity, calculate the difference between the discharge capacities C2 of any two batteries; calculate the ratio based on this difference and the battery's rated capacity; group batteries with ratios ≤1% into an initial battery group.

[0067] 7): Select either charging capacity C1 or charging capacity C3 for secondary grouping. Taking secondary grouping using charging capacity C1 as an example, sort the charging capacity C1 in the initial battery groups and determine the level ratio to be 5%; calculate the difference in charging capacity C1 between any two batteries in each initial battery group; calculate the ratio based on this difference and the battery's rated capacity; group the initial battery groups with this ratio ≤ 5% into a target lithium-ion battery pack.

[0068] 8) Group the batteries in the target lithium-ion battery pack according to the following requirements: internal resistance 0.3±0.05mΩ, voltage difference ≤5mV, and K value ≤0.05mV / h. Select batteries and connect them in series to form the battery pack.

[0069] To better illustrate the effectiveness of the method of the present invention, 100 lithium iron phosphate 150Ah batteries were selected for charging experiments. Figure 2 This is a constant current and constant voltage charging curve of a lithium iron phosphate battery provided in an embodiment of the present invention. Figure 2 The vertical axis represents the charging voltage during the charging process, and the horizontal axis represents the charging capacity during the charging process. (Combined with...) Figure 2 The constant current and constant voltage charging voltage curve of the lithium iron phosphate battery is shown. Figure 2It is not difficult to find that the voltage curves of batteries ①, ②, and ③ are inconsistent during the charging process. Abnormal batteries ①, ②, and ③ are eliminated based on the constant current charging capacity data. The screening method is as follows: Battery ① has a constant current charging capacity of 110Ah, battery ② has a constant current charging capacity of 113Ah, battery ③ has a constant current charging capacity of 120Ah, and other batteries have a constant current charging capacity of 114-117Ah. In this embodiment, lithium batteries <114Ah and >117Ah are eliminated, and batteries with a constant current charging capacity of 114-117Ah are selected as a group. This improves the consistency of battery charging. Batteries grouped according to their constant current charging capacity have a simulated dynamic voltage difference of approximately 75mV during battery pack charging. Batteries not grouped have a simulated dynamic voltage difference of 170mV during battery pack charging. The method of this invention can effectively improve the accuracy of battery grouping and avoid battery grouping errors caused by charge / discharge test errors.

[0070] To achieve the above embodiments, the present invention also proposes a grouping system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs.

[0071] Figure 3 This is a block diagram of a matching system for improving the dynamic voltage difference during charging of a lithium iron phosphate battery pack, provided in an embodiment of the present invention.

[0072] like Figure 3 As shown, the grouping system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs includes a capacity control module, an acquisition module, and a grouping module, wherein:

[0073] The capacity control module is used to charge each battery to its characteristic voltage in a constant current mode and then continue to charge it to the charging cut-off voltage in a constant current mode. After each battery is charged to the charging cut-off voltage, it switches to a constant voltage mode to continue charging each battery until the battery current drops to the cut-off current. At this time, each battery is fully charged and charging stops. Then, each fully charged battery is discharged to the discharge cut-off voltage in a constant current mode.

[0074] The acquisition module is used to acquire the first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage, and also to acquire the discharge capacity corresponding to the discharge cutoff voltage.

[0075] The grouping module is used to group all batteries once based on their discharge capacity to obtain at least one initial battery group; and to group each initial battery group based on a first charging capacity and / or a second charging capacity to obtain multiple target lithium-ion battery packs.

[0076] Furthermore, in one possible implementation of this invention, the characteristic voltage determination step in the capacity control module includes: selecting multiple experimental lithium-ion batteries, conducting charging experiments on all experimental lithium-ion batteries to determine the capacity range values ​​when charged to different voltages; filtering out capacity range values ​​greater than the set capacity range to obtain a candidate capacity range value set; removing charging voltages equal to the charging cut-off voltage from the charging voltages corresponding to the candidate capacity range value set to obtain a candidate charging voltage set; and selecting one from the candidate charging voltage set as the characteristic voltage.

[0077] Furthermore, in one possible implementation of this invention, the grouping module, when grouping all batteries once based on their discharge capacity to obtain at least one initial battery group, is specifically configured to: determine a first grade ratio based on demand; sort all batteries by their discharge capacity and calculate the difference in discharge capacity between any two batteries; calculate a first ratio based on the discharge capacity difference and the rated capacity of the batteries; and group all batteries once based on the first ratio and the first grade ratio to obtain at least one initial battery group.

[0078] Furthermore, in one possible implementation of the present invention, the grouping module, when used to group each initial battery group based on a first charging capacity and / or a second charging capacity to form multiple target lithium-ion battery packs, is specifically used to: determine corresponding second ratio and third ratio based on the first charging capacity and / or the second charging capacity and the rated capacity of the battery; and group each initial battery group based on the second ratio and / or the third ratio, combined with corresponding gear ratios, to form multiple target lithium-ion battery packs.

[0079] Furthermore, in one possible implementation of the present invention, the grouping module grouping the initial battery groups based on the first charging capacity and / or the second charging capacity includes two grouping methods: one method is to group the initial battery groups a second time based on one of the first charging capacity and the second charging capacity to obtain multiple target lithium-ion battery groups; the other method is to group the initial battery groups a second time based on the second charging capacity to obtain multiple intermediate battery groups; and to group the intermediate battery groups a third time based on the first charging capacity to obtain multiple target lithium-ion battery groups.

[0080] Furthermore, in one possible implementation of the present invention, the matching system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs further includes an anomaly processing module. The anomaly processing module is used to remove batteries corresponding to abnormal points in battery internal resistance, abnormal points in K value, and abnormal points in voltage difference in each target lithium-ion battery pack.

[0081] It should be noted that the foregoing explanation of the pairing method embodiment for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs also applies to the pairing system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs in this embodiment, and will not be repeated here.

[0082] In this embodiment of the invention, each battery is charged to a characteristic voltage using a constant current method, and then charged to a charging cutoff voltage using the same method. The first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage are obtained. After each battery is charged to the charging cutoff voltage, the charging is switched to a constant voltage method until the battery current drops to the cutoff current, at which point each battery is fully charged and charging stops. The fully charged batteries are then discharged to a discharge cutoff voltage using a constant current method, and the discharge capacity corresponding to the discharge cutoff voltage is obtained. Based on the discharge capacity, all batteries are grouped once to obtain at least one initial battery group. Each initial battery group is then further grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. In this case, by combining the discharge capacity corresponding to the discharge cutoff voltage, the first charging capacity corresponding to the characteristic voltage, and the second charging capacity corresponding to the charging cutoff voltage, all batteries are grouped multiple times, taking into account both discharge and charging capacities. This improves the dynamic voltage difference during charging and discharging and enhances battery consistency.

[0083] The method and system of this invention introduce capacity grouping during the charging stage into existing battery grouping methods, thereby further improving battery consistency and dynamic voltage difference during the charging process of the battery pack. This invention has a short production cycle, is easy to implement, and is simple to replicate, further improving the consistency between lithium batteries in the same group and extending the cycle life of the lithium battery pack. Through the grouping method of this invention, no additional facilities are required; secondary or tertiary grouping can be performed by selecting the charging capacity during constant current charging, making it simple to operate and highly efficient. Improving grouping consistency: The battery grouping method of this invention is based on the actual electrochemical parameters of the batteries, introducing constant current capacity grouping during charging, thereby improving the dynamic voltage difference during the charging process of the battery pack. The battery packs assembled using the grouping method of this invention have improved consistency, reducing the dynamic voltage difference during charging from 170mV to within 70mV, improving the working efficiency of the battery pack, and also increasing the cycle life of the battery pack.

[0084] To implement the above embodiments, the present invention also proposes an electronic device, including: a processor and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the method provided in the foregoing embodiments.

[0085] To implement the above embodiments, the present invention also proposes a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the methods provided in the foregoing embodiments.

[0086] To implement the above embodiments, the present invention also proposes a computer program product, including a computer program that, when executed by a processor, implements the methods provided in the foregoing embodiments.

[0087] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0088] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0089] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0090] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0091] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any of the following techniques known in the art, or a combination thereof: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0092] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0093] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0094] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs, characterized in that, include: Each battery is charged to a characteristic voltage using a constant current method, and then charged to a charging cutoff voltage using a constant current method. The first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage are obtained. After each battery is charged to the charging cutoff voltage, the constant voltage mode is switched to continue charging each battery until the battery current drops to the cutoff current. At this time, each battery is fully charged and charging stops. Each fully charged battery is discharged to the discharge cutoff voltage using a constant current method, and the discharge capacity corresponding to the discharge cutoff voltage is obtained. Based on the discharge capacity, all batteries are grouped once to obtain at least one initial battery group; Each initial battery group is grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. The process of grouping initial battery groups based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs includes: Based on the second charging capacity, each initial battery group is further grouped to obtain multiple intermediate battery groups; Based on the first charging capacity, each intermediate battery group is divided into three groups to obtain multiple target lithium-ion battery packs. The steps for determining the characteristic voltage include: Multiple experimental lithium-ion batteries were selected, and charging experiments were conducted on all experimental lithium-ion batteries to determine the capacity range when charged to different voltages. The capacity range values ​​that are greater than the set capacity range are selected to obtain a candidate capacity range value set; Remove the charging voltages that are equal to the charging cut-off voltage from the charging voltages corresponding to the candidate capacity range set to obtain the candidate charging voltage set; Choose one from the set of candidate charging voltages as the characteristic voltage.

2. The method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs according to claim 1, characterized in that, The step of grouping all batteries based on the discharge capacity to obtain at least one initial battery group includes: Determine the first-tier ratio based on demand; sort all batteries by discharge capacity and calculate the difference in discharge capacity between any two batteries; calculate the first ratio based on the discharge capacity difference and the battery's rated capacity. Based on the first ratio and the first gear ratio, all batteries are grouped once to obtain at least one initial battery group.

3. The grouping method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs according to claim 1, characterized in that, The process of grouping initial battery groups based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs includes: Based on the first charging capacity and / or the second charging capacity, and the rated capacity of the battery, a corresponding second ratio and a third ratio are determined. Based on the second ratio and / or the third ratio, and combined with the corresponding gear ratio, each initial battery group is grouped into multiple target lithium-ion battery packs.

4. The grouping method for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs according to claim 1, characterized in that, Also includes: Remove batteries from each target lithium-ion battery pack that have abnormal internal resistance, abnormal K value, or abnormal voltage difference.

5. A battery pack matching system for improving the dynamic voltage difference during charging of lithium iron phosphate battery packs, characterized in that, include: The capacity control module is used to charge each battery to a characteristic voltage in a constant current mode and then continue to charge it to the charging cutoff voltage in a constant current mode. After each battery is charged to the charging cutoff voltage, it switches to a constant voltage mode to continue charging each battery until the battery current drops to the cutoff current. At this time, each battery is fully charged and charging stops. Then, each fully charged battery is discharged to the discharge cutoff voltage in a constant current mode. The acquisition module is used to acquire the first charging capacity corresponding to the characteristic voltage and the second charging capacity corresponding to the charging cutoff voltage, and also to acquire the discharge capacity corresponding to the discharge cutoff voltage. A grouping module is used to group all batteries into groups based on the discharge capacity to obtain at least one initial battery group. Each initial battery group is grouped based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs. The process of grouping initial battery groups based on the first charging capacity and / or the second charging capacity to form multiple target lithium-ion battery packs includes: Based on the second charging capacity, each initial battery group is further grouped to obtain multiple intermediate battery groups; Based on the first charging capacity, each intermediate battery group is divided into three groups to obtain multiple target lithium-ion battery packs. The steps for determining the characteristic voltage include: Multiple experimental lithium-ion batteries were selected, and charging experiments were conducted on all experimental lithium-ion batteries to determine the capacity range when charged to different voltages. The capacity range values ​​that are greater than the set capacity range are selected to obtain a candidate capacity range value set; Remove the charging voltages that are equal to the charging cut-off voltage from the charging voltages corresponding to the candidate capacity range set to obtain the candidate charging voltage set; Choose one from the set of candidate charging voltages as the characteristic voltage.

6. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory to implement the method as described in any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-4.

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