Method and system for rapidly calibrating fast charging current of battery pack

Abstract

The invention discloses a method and system for quickly calibrating fast charging current of a battery pack, and the method comprises the steps: calibrating the maximum charging current of a battery cell at different temperatures and SOC in advance, and taking the maximum charging current as initial fast charging current of the battery pack; according to the temperature boundary of the battery pack and the SOC boundary of the battery pack, establishing a fast charging current matrix of the battery pack; and based on the battery fast charging current matrix, assigning a target matrix unit in the battery fast charging current matrix to carry out fast charging current calibration on the battery pack. According to the method, SOC interval is carried out on battery pack fast charging current, the influence of negative electrode relative reference electrode potential and battery cell temperature rise is synchronously considered at battery cell fast charging current marking time, sub-matrix unit calibration is carried out, and finally a battery pack fast charging ampere meter is formed and corresponds to a battery pack. And finally, the technical defect that the quick charging performance of the battery pack cannot be exerted due to the fact that the battery pack is calibrated by directly adopting a cell level quick charging flow calibration method in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery pack fast-charging current calibration, and specifically relates to a method and system for quickly calibrating a battery pack fast-charging current. Background Art

[0002] Lithium-ion batteries have become the mainstream power source in electric vehicles and energy storage systems due to their high energy density, long cycle life, and good charge and discharge efficiency. Stepped fast charging technology can significantly improve the fast charging capability of battery packs, shorten fast charging time, and improve customer experience; however, the fast charging capability of batteries at different SOCs and temperatures varies greatly, so quickly and accurately calibrating the fast charging current thresholds at different SOCs and temperatures is one of the important tasks in the battery pack development process.

[0003] Currently, the more common method is to calibrate the fast charging current at the cell level. However, because the battery cell and the battery pack exhibit different temperature rise paths under the same fast charging current, the fast charging current of the battery cell is directly used for the fast charging current of the battery pack. This method does not take into account the different temperature rise paths of the battery during the fast charging process, which often leads to certain differences when the fast charging current calibrated by the battery cell is directly used for the fast charging of the battery pack, resulting in the inability to fully utilize the fast charging performance of the battery pack. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for quickly calibrating the fast charging current of a battery pack, so as to solve the technical defect that the battery pack cannot be calibrated by directly using the cell-level fast charging current calibration method in the prior art, resulting in the inability to exert the fast charging performance of the battery pack.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a method for quickly calibrating a fast charging current of a battery pack is provided, comprising: Pre-calibrate the maximum charging current of the battery cell at different temperatures and SOCs, and use the maximum charging current as the initial fast charging current of the battery pack; Establishing a battery pack fast charging current matrix according to the temperature boundary of the battery pack and the SOC boundary of the battery pack; Based on the battery fast charge current matrix, a target matrix unit within the battery fast charge current matrix is ​​designated to perform fast charge current calibration on the battery pack.

[0006] Furthermore, according to the temperature boundary of the battery pack and the SOC boundary of the battery pack, a battery pack fast charging current matrix is ​​established, which specifically includes: Setting basic elements for establishing a fast charge current matrix, and establishing a battery pack fast charge current matrix according to the set basic elements; Among them, the basic elements include the lowest temperature at which the battery pack can be charged, the highest temperature at which the battery pack can be charged, the maximum temperature at which the battery pack can be used, the lowest SOC at which the battery pack can operate, and the maximum SOC at which the battery pack can operate.

[0007] Furthermore, the lowest chargeable temperature of the battery pack is set as Tmin.

[0008] Furthermore, the maximum chargeable temperature of the battery pack is set to Tmax.

[0009] Furthermore, the minimum operating SOC of the battery pack is set to SOCmin.

[0010] Furthermore, the maximum operating SOC of the battery pack is set to SOCmax.

[0011] Further, based on the battery fast charge current matrix, specifying a target matrix unit in the battery fast charge current matrix to perform fast charge current calibration on the battery pack specifically includes: Adjust the pre-calibrated normal temperature of the battery cell to the SOC in the specified target matrix unit; Performing temperature balancing at the target matrix SOC so that both the inside and outside of the battery cell reach the target SOC; Charge the battery cells with different fast charge currents, and record the potential of the negative electrode of the battery cell relative to the reference electrode and the temperature rise of the battery cell; The amplified verification current judgment value is set to verify the relative reference electrode potential of the negative electrode of the battery cell and the temperature rise of the battery cell, and the fast charging current of other matrix units is calibrated synchronously to form a battery panel fast charging current matrix to fast charge the battery pack.

[0012] Furthermore, the battery cells are charged with different fast charging currents, including: The battery cells are charged with different charging currents of 4C, 3C, 2C, 1C, 0.8C, 0.5C, 0.3C and 0.2C.

[0013] Furthermore, temperature equalization is performed under the SOC of the target matrix, specifically, the battery cells are placed in an environmental box for temperature equalization.

[0014] In a second aspect, a system for quickly calibrating a fast charging current of a battery pack is provided, comprising: The first calibration module is used to calibrate the maximum charging current of the battery cell at different temperatures and SOCs; A fast charge current matrix establishment module is used to establish a battery pack fast charge current matrix according to the temperature boundary and the SOC boundary of the battery pack; The second calibration module is used to perform fast charging current calibration on the battery pack based on the battery fast charging current matrix and specify the target matrix unit in the battery fast charging current matrix.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This method performs SOC intervals on the fast-charging current of the battery pack, and simultaneously considers the influence of the negative electrode relative reference electrode potential and the temperature rise of the battery cell when calibrating the fast-charging current of the battery cell, performs matrix unit calibration, and finally forms a fast-charging current table for the battery pack. Compared with the traditional battery pack fast-charging current calibration, the maximum charging current at different temperatures and SOCs is first calibrated with the battery cell to form the initial fast-charging current of the battery pack; then the fast-charging path and temperature of the battery pack are calibrated, that is, the actual fast-charging temperature rise and fast-charging path of the battery pack at different temperatures and different starting SOC fast-charging conditions. If there is a large deviation from the fast-charging current at the battery cell end, the rate needs to be reduced according to the measured temperature rise of the battery pack, which solves the technical defect that the battery pack cannot be calibrated by directly using the fast-charging current calibration method at the cell level in the prior art, resulting in the inability to exert the fast-charging performance of the battery pack.

[0016] 2. By setting the minimum and maximum chargeable temperatures of the battery pack, as well as the maximum available temperature, the battery can be charged within a safe temperature range to avoid safety issues caused by overheating or overcooling. At the same time, by setting the minimum and maximum SOC of the battery pack, the battery can be prevented from being overcharged or over-discharged, further protecting the safety of the battery. The established battery pack fast-charging current matrix can dynamically adjust the charging current according to the real-time temperature and SOC conditions to ensure that the battery is charged at the optimal charging rate, which can not only improve the charging efficiency, but also reduce the energy loss during the charging process, thereby optimizing the entire charging strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A flow chart of the method for quickly calibrating the fast charging current of a battery pack provided by the present invention; Figure 2 A schematic diagram of a battery pack fast charging current matrix in the method for quickly calibrating a battery pack fast charging current provided by the present invention; Figure 3 A schematic diagram of the system for quickly calibrating the fast-charging current of a battery pack provided by the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0022] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0023] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] Lithium-ion batteries have become the mainstream power source in electric vehicles and energy storage systems due to their high energy density, long cycle life, and good charge and discharge efficiency. Stepped fast charging technology can significantly improve the fast charging capability of battery packs, shorten fast charging time, and improve customer experience; however, the fast charging capability of batteries at different SOCs and temperatures varies greatly, so quickly and accurately calibrating the fast charging current thresholds at different SOCs and temperatures is one of the important tasks in the battery pack development process.

[0025] Currently, the more common method is to calibrate the fast charging current at the cell level. However, because the battery cell and the battery pack exhibit different temperature rise paths under the same fast charging current, the fast charging current of the battery cell is directly used for the fast charging current of the battery pack. This method does not take into account the different temperature rise paths of the battery during the fast charging process, which often leads to certain differences when the fast charging current calibrated by the battery cell is directly used for the fast charging of the battery pack, resulting in the inability to fully utilize the fast charging performance of the battery pack.

[0026] In order to solve the above technical defects, the inventor provides a method and system for quickly calibrating the fast charging current of a battery pack.

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings: like Figure 1-Figure 2 As shown, in a first aspect of an embodiment of the present invention, a method for quickly calibrating a fast charging current of a battery pack is provided, comprising: S101. Pre-calibrate the maximum charging current of the battery cell at different temperatures and SOCs, and use the maximum charging current as the initial fast-charging current of the battery pack; illustratively, test the battery cell under different temperatures and SOC conditions to determine its maximum tolerable charging current, record these test data, and use the maximum charging current under each condition as a reference for the initial fast-charging current of the battery pack. By pre-calibrating the maximum charging current of the battery cell at different temperatures and SOCs, it can be ensured that the charging current of the battery pack is accurately controlled within a safe range during the fast charging process, avoiding safety issues such as battery overheating, damage, or even explosion caused by excessive current, and also avoiding problems such as long charging time and low efficiency caused by too small current. With these accurate test data, the charging strategy of the battery pack can be further optimized.

[0028] S102: Establish a battery pack fast charge current matrix according to the temperature boundary and the SOC boundary of the battery pack; illustratively, Figure 2 As shown, firstly, the basic elements of the fast charge current matrix are set, and then the battery pack fast charge current matrix is ​​established according to the set basic elements; wherein the basic elements include the lowest temperature at which the battery pack can be charged, the highest temperature at which the battery pack can be charged, the highest temperature at which the battery pack can be used, the lowest SOC of the battery pack, and the highest SOC of the battery pack. Figure 2It can be seen that the lowest temperature at which the battery pack can be charged is set to Tmin, the highest temperature at which the battery pack can be charged is set to Tmax, the lowest SOC of the battery pack is set to SOCmin, and the highest SOC of the battery pack is set to SOCmax. Among them, the lowest temperature at which the battery pack can be charged is recorded as Tmin, the lowest temperature at which the battery can be used, such as -20°C; the highest temperature at which the battery can be charged is recorded as Tmax, the highest temperature at which the battery can be used, such as 55°C; the lowest SOC of the battery is recorded as SOCmin, such as 3% SOC; the highest SOC is recorded as SOCmax, such as 97% SOC. Figure 2 In the matrix, each matrix SOC span is recorded as ΔSOC; each matrix temperature span is recorded as ΔT. In the 12th matrix unit, ΔSOC=20%-10%=10%SOC; ΔT=(-10)-(-15)=5°C. Through the establishment of the matrix, the temperature boundary and SOC boundary data are divided into multiple intervals according to the temperature boundary and SOC boundary of the battery pack. Each matrix unit in this matrix represents the maximum charging current that the battery pack can withstand under specific temperature and SOC conditions.

[0029] S103, based on the battery fast charge current matrix, specify the target matrix unit in the battery fast charge current matrix to calibrate the battery pack for fast charge current. Exemplarily, the normal temperature of the pre-calibrated battery cell is adjusted to the SOC in the specified target matrix unit, for example, the SOC for starting charging in the target matrix unit, such as the 12th matrix unit, the starting SOC is 10% SOC; then, temperature balancing is performed under the SOC of the target matrix so that the inside and outside of the battery cell reach the target SOC, and the battery cell is placed at the target ambient temperature until the inside and outside of the battery cell reach the target ambient temperature, that is, the temperature balance state is reached. The specific balancing process is to place the battery cell in an environmental box for temperature balancing; when the battery cell works within a specific temperature range, its performance is the best, and temperature balancing ensures that the battery cell works under the optimal temperature conditions, thereby improving its charging and discharging efficiency, energy density and cycle life, while temperature imbalance may cause thermal stress inside the battery cell, increase safety risks such as short circuit and thermal runaway, and temperature balancing can effectively reduce these risks and improve the safety of the battery cell. Secondly, different fast charging currents are selected to charge the battery cells, such as 4C, 3C, 2C, 1C, 0.8C, 0.5C, 0.3C and 0.2C. Different charging currents are used to charge the battery cells, and the relative reference electrode potential of the battery cell and the temperature rise of the battery cell are recorded. By understanding the changes in the negative electrode potential and temperature rise of the battery cell under different charging currents, the charging strategy can be optimized to balance the relationship between charging speed and battery life and safety. For example, when fast charging is required, an appropriate charging current can be selected to minimize the temperature rise and potential offset of the battery cell; when fast charging is not required, a lower charging current can be selected to extend the battery life. At the same time, excessive charging current may cause the battery cell temperature to be too high and the potential offset to be too large, thereby increasing the risk of thermal runaway and short circuit of the battery. It is worth noting that the negative electrode reference electrode potential, that is, the negative electrode potential to lithium, and the battery cell temperature rise, that is, the temperature of the same temperature monitoring point of the battery cell after charging - the temperature before charging; it must also meet the negative electrode relative reference electrode potential ≥ negative reference potential safety threshold; and the battery cell temperature rise ≤ ΔT.

[0030] like Figure 2In the fast charging current calibration of the 12th matrix unit: after the battery sample is charged to 10% SOC at room temperature, it is placed in a -15℃ environmental chamber thermostat for temperature balance. As above, the target verification current is initially charged according to the fast charging current set according to the battery development indicators, such as 4C, 3C, 2C, 1C, 0.8C, 0.5C, 0.3C, 0.2C, etc. (xC). At the same time, temperature sensing lines are arranged at different parts of the battery cell to monitor the temperature of the negative electrode relative to the reference electrode potential and the battery cell charging temperature rise; if the negative electrode relative to the reference electrode potential is greater than 10mV (negative reference potential safety threshold), and the battery cell charging process temperature rise is less than 5℃. Set the amplified verification current judgment value, and verify the relative reference electrode potential of the negative electrode of the battery cell and the temperature rise of the battery cell according to the above steps until the relative reference electrode potential of the negative electrode is ≥10mV, and the temperature rise of the battery cell is 5°C. At this time, the verification current is the maximum fast charging current in the 12th matrix unit; then take the 12th matrix unit as an example, perform the fast charging current verification method of the matrix unit, and synchronously calibrate the fast charging current of other matrix units, finally forming a battery pack fast charging current matrix, which can be directly used for battery pack fast charging. For example, adjust the battery cell to 10% SOC at room temperature, adjust the environmental chamber to -18℃±2℃, put the battery cell into the environmental chamber for temperature balance (stand for 12 hours), and ensure that the internal and external temperatures of the battery cell reach -20℃≤T≤-15℃; charge for 15 minutes with the current charging current of 0.2C, monitor whether the battery cell temperature rise and the negative reference electrode potential reach the set judgment value, whether the negative electrode potential relative to the reference electrode is greater than 10mV, and whether the battery cell temperature rise during charging is less than 5℃; if the negative electrode potential relative to the reference electrode is too high, such as 50mV, and the charging process If the temperature rise is far less than 5°C, such as 2°C, the charging current is increased, such as adjusting to 0.5C for charging for 6 minutes, and the negative electrode relative reference electrode potential and the temperature rise of the battery cell during charging are continuously monitored; if the set judgment value is still not reached; the charging current is further increased, such as 0.8C; if the judgment value has been triggered, the charging current is reduced, such as 0.3C; this method performs SOC interval on the fast charging current of the battery pack, and simultaneously considers the influence of the negative electrode relative reference electrode potential and the temperature rise of the battery cell when calibrating the fast charging current of the battery cell, performs matrix unit calibration, and finally forms a fast charging current table for the battery pack. Compared with the traditional battery pack fast charging current calibration, the maximum charging current at different temperatures and SOCs is first calibrated with the battery cells to form the initial fast charging current of the battery pack; then the battery pack fast charging path and temperature are calibrated, that is, the actual fast charging temperature rise and fast charging path of the battery pack under different temperatures and different starting SOC fast charging conditions. If there is a large deviation from the fast charging current at the battery cell end, it is necessary to reduce the rate according to the actual temperature rise of the battery pack, which solves the technical defect of the prior art that the battery pack is calibrated directly by the cell-level fast charging current calibration method, resulting in the inability to exert the fast charging performance of the battery pack; at the same time, by setting the minimum and maximum chargeable temperatures of the battery pack, as well as the maximum available temperature, it can ensure that the battery is charged within a safe temperature range to avoid safety problems caused by overheating or overcooling.At the same time, by setting the minimum and maximum SOC of the battery pack, the battery can be prevented from being overcharged or over-discharged, further protecting the safety of the battery. The established battery pack fast-charging current matrix can dynamically adjust the charging current according to the real-time temperature and SOC conditions to ensure that the battery is charged at the optimal charging rate, which can not only improve the charging efficiency, but also reduce the energy loss during the charging process, thereby optimizing the entire charging strategy.

[0031] In a second aspect of an embodiment of the present invention, a system for quickly calibrating a fast charging current of a battery pack is provided. Figure 3 As shown, including: The first calibration module is used to calibrate the maximum charging current of the battery cell at different temperatures and SOCs; A fast charge current matrix establishment module is used to establish a battery pack fast charge current matrix according to the temperature boundary and the SOC boundary of the battery pack; The second calibration module is used to perform fast charging current calibration on the battery pack based on the battery fast charging current matrix and specify the target matrix unit in the battery fast charging current matrix.

[0032] In the process of calibrating the fast charging current of the battery pack using this system, the first calibration module can accurately calibrate the maximum charging current of the battery cell at different temperatures and SOCs, so as to use the maximum charging current as the The first version of the fast charging current of the battery pack; and the fast charging current matrix establishment module establishes the battery pack fast charging current matrix according to the temperature boundary and SOC boundary of the battery pack, providing the optimal current selection for fast charging of the battery pack under different conditions, thereby achieving a balance between charging efficiency and safety. Finally, the second calibration module specifies the target matrix unit to calibrate the battery pack for fast charging current based on the battery fast charging current matrix, which ensures that the battery pack can be charged at the optimal current during the fast charging process, improves the accuracy and efficiency of charging, and by accurately calibrating the fast charging current, the system can avoid the battery pack from generating excessive heat during the fast charging process, thereby reducing the damage to the battery material caused by thermal stress. This helps to extend the service life of the battery and increase the number of battery cycles.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A method for quickly calibrating the fast charging current of a battery pack, characterized in that: include: Pre-calibrate the maximum charging current of the battery cell at different temperatures and SOCs, and use the maximum charging current as the initial fast charging current of the battery pack; Establishing a battery pack fast charging current matrix according to the temperature boundary of the battery pack and the SOC boundary of the battery pack; Based on the battery fast charge current matrix, a target matrix unit within the battery fast charge current matrix is ​​designated to perform fast charge current calibration on the battery pack.

2. The method for quickly calibrating the fast charging current of a battery pack according to claim 1, characterized in that: According to the temperature boundary of the battery pack and the SOC boundary of the battery pack, a battery pack fast charging current matrix is ​​established, specifically including: Setting basic elements for establishing a fast charge current matrix, and establishing a battery pack fast charge current matrix according to the set basic elements; Among them, the basic elements include the lowest temperature at which the battery pack can be charged, the highest temperature at which the battery pack can be charged, the maximum temperature at which the battery pack can be used, the lowest SOC at which the battery pack can operate, and the maximum SOC at which the battery pack can operate.

3. The method for quickly calibrating the fast charging current of a battery pack according to claim 2, characterized in that: The lowest temperature at which the battery pack can be charged is set as Tmin.

4. The method for quickly calibrating the fast charging current of a battery pack according to claim 2, characterized in that: The maximum temperature at which the battery pack can be charged is set to Tmax.

5. The method for quickly calibrating the fast charging current of a battery pack according to claim 2, characterized in that: The minimum operating SOC of the battery pack is set to SOCmin.

6. The method for quickly calibrating the fast charging current of a battery pack according to claim 2, characterized in that: The maximum operating SOC of the battery pack is set to SOCmax.

7. The method for quickly calibrating the fast charging current of a battery pack according to claim 1, characterized in that: Based on the battery fast charge current matrix, specifying a target matrix unit in the battery fast charge current matrix to perform fast charge current calibration on the battery pack specifically includes: Adjust the pre-calibrated normal temperature of the battery cell to the SOC in the specified target matrix unit; Performing temperature balancing at the target matrix SOC so that both the inside and outside of the battery cell reach the target SOC; Charge the battery cells with different fast charge currents, and record the potential of the negative electrode of the battery cell relative to the reference electrode and the temperature rise of the battery cell; The amplified verification current judgment value is set to verify the relative reference electrode potential of the negative electrode of the battery cell and the temperature rise of the battery cell, and the fast charging current of other matrix units is calibrated synchronously to form a battery panel fast charging current matrix to fast charge the battery pack.

8. The method for quickly calibrating the fast charging current of a battery pack according to claim 7, characterized in that: Charge the battery cells with different fast charge currents, including: The battery cells are charged with different charging currents of 4C, 3C, 2C, 1C, 0.8C, 0.5C, 0.3C and 0.2C.

9. The method for quickly calibrating the fast charging current of a battery pack according to claim 1, characterized in that: Temperature balancing is performed under the SOC of the target matrix, specifically, the battery cells are placed in an environmental chamber for temperature balancing.

10. A system for quickly calibrating the fast charging current of a battery pack, characterized in that: include: The first calibration module is used to calibrate the maximum charging current of the battery cell at different temperatures and SOCs; A fast charge current matrix establishment module is used to establish a battery pack fast charge current matrix according to the temperature boundary and the SOC boundary of the battery pack; The second calibration module is used to perform fast charging current calibration on the battery pack based on the battery fast charging current matrix and specify the target matrix unit in the battery fast charging current matrix.

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