A method for controlling the thermal management of a power battery

Abstract

The present invention discloses a thermal management control method for power batteries, which includes the following steps: First, perform CFD simulation analysis on each single cell in the battery, and classify them into categories A and B according to the heat dissipation performance; divide a single heating film into two regions, A1 and B1, according to the type of the corresponding single cell, and control the on / off of the single heating film in different regions by setting separate corresponding on / off switches A2 and B2; add a thermal insulation layer to the outside of the cells of category A; then, according to parameters such as the ambient temperature, etc., control the on / off of the single heating film in the same region to achieve the temperature difference control of the single-module cells and the whole-pack cells. The present invention first designs heating schemes with different power densities according to the different heat dissipation performances of single cells at different positions, and cooperates with local thermal insulation design and a dual heating system for the module to achieve independent control of different regions, and heats the power batteries in need according to the temperatures of the power batteries at different positions in different modules, so as to reduce the temperature difference between the single module and the whole pack.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal management, and particularly to a control method for power battery thermal management. Background Art

[0002] At present, lithium-ion batteries have been widely used in the fields of automobiles, electronic products, and energy storage due to their high specific capacity, good charge and discharge performance, and high cycle life, etc., and their comprehensive performance is superior to other types of batteries. Along with this, the requirements for the safety and reliability of batteries are getting higher and higher. Temperature is an important factor affecting the safety and reliability of lithium-ion power batteries. At the same time, in order to ensure that lithium-ion power batteries have good performance, the temperature of the batteries should be controlled within a certain range.

[0003] For cylindrical cell natural cooling battery packs, a wound heating film is commonly used to heat the side of the cell or an epoxy board heating film is used to heat the cell pole. In the related art, although the above-mentioned scheme is adopted for the thermal management scheme design and it is determined whether to heat the power battery based on the power battery temperature, the thermal management design scheme only simply controls the total power of the heating film, that is, calculates the total required power of the heating film according to the thermal property parameters and the temperature rise rate target requirements of the power battery, and performs uniform distribution; the control method is only a simple on-off control, that is: when the power battery temperature exceeds a certain set value, the thermal control system heats the power battery, and the control method is single. This thermal management design scheme and control method cannot meet the thermal management requirements of different-position cells. In actual use, the temperature difference between single modules and the whole pack is large, and the thermal management effect is not ideal, which further affects the battery consistency and charge and discharge performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a control method for power battery thermal management, which can design heating schemes with different power densities according to the actual positions and heat dissipation performances of the cells to reduce the temperature difference generated during heating.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A control method for power battery thermal management includes the following steps:

[0007] A: First, perform CFD simulation analysis on each cell in the battery, classify them into category A and category B according to the heat dissipation performance, and obtain the corresponding cell heat dissipation coefficients Ka and Kb for each category after classification, where Ka is greater than Kb;

[0008] B: Divide the single-chip heating film into two areas, A1 and B1, according to the type of the corresponding battery cell. The heating power density ratio of the two areas is A1 > B1, and the on-off control of the single-chip heating film in different areas is realized by setting the corresponding on-off switches A2 and B2 separately; to ensure that the temperature comparison of the two types of battery cells, A and B, is A > B during the heating stage, so as to balance and reduce the temperature difference caused by the difference in heat dissipation performance during the non-heating stage;

[0009] C: Add a thermal insulation layer to the outside of the type-A battery cells;

[0010] D: Then, according to the ambient temperature, the maximum temperature Tmax of the whole pack, the minimum temperature Tmin of the whole pack, the minimum temperature Tmina of the type-A battery cells, the minimum temperature Tminb of the type-B battery cells, the maximum temperature difference △T0 = Tmax - Tmin of the whole pack, and the minimum temperature difference △T1 = Tmina - Tminb between the type-A and type-B battery cells, coordinate the on-off control of the single-chip heating film in the same area to achieve the temperature difference control of the single-module battery cells and the whole-pack battery cells.

[0011] The specific steps of step D are as follows:

[0012] D1: When entering the charging state judgment mode:

[0013] Execute determination 1: Judge whether Tamt meets the first temperature threshold;

[0014] If the judgment result is no: Then enter the non-low-temperature charging mode, and control the on-off switches A2 and B2 to both perform the disconnection operation;

[0015] If the judgment result is yes: Then execute determination 2: Judge whether △T1 meets the second temperature threshold;

[0016] If the determination result is no, then execute determination 3: If the judgment result is yes: Then execute determination 4:

[0017] Execute determination 3: Judge whether △T1 meets the third temperature threshold, and the third temperature threshold is the maximum value of the second temperature threshold;

[0018] If the judgment result is no: Then enter the low-temperature slow charging and temperature equalization 1 mode, at this time, the A relay performs the closing operation, and the B relay performs the disconnection operation;

[0019] If the judgment result is yes: Then enter the low-temperature slow charging and temperature equalization 2 mode, at this time, the A relay performs the disconnection operation, and the B relay performs the closing operation;

[0020] Execute determination 4: Judge whether Tmin meets the fourth temperature threshold;

[0021] If the judgment result is no: Then enter the low-temperature slow charging and temperature equalization 3 mode, and both the A and B relays perform the disconnection operation;

[0022] If the judgment result is yes: enter the low-temperature slow charging heating mode, and both relay A and relay B perform closing operations;

[0023] D2: When entering the non-low-temperature charging mode:

[0024] Execute determination 5: Determine whether Tamt meets the fifth temperature threshold, where the first temperature threshold > the fifth temperature threshold;

[0025] If the judgment result is no: continue to stay in the non-low-temperature charging mode;

[0026] If the judgment result is yes: then return to the charging state judgment mode;

[0027] D3: When entering the low-temperature slow charging temperature equalization 1 mode:

[0028] Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold;

[0029] If the judgment result is no: then return to the charging state judgment mode;

[0030] If the judgment result is yes: then execute determination 7: Determine whether △T1 meets the seventh temperature threshold, where the seventh temperature threshold > 0°C and is within the second temperature threshold range;

[0031] If the judgment result is no: continue to stay in the low-temperature slow charging temperature equalization 1 mode;

[0032] If the judgment result is yes: enter the low-temperature slow charging temperature equalization 3 mode;

[0033] D4: When entering the low-temperature slow charging temperature equalization 2 mode:

[0034] Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold;

[0035] If the judgment result is no: then enter the charging state judgment mode;

[0036] If the judgment result is yes: then execute determination 8: Determine whether △T1 meets the eighth temperature threshold, where the eighth temperature threshold < 0°C and is within the second temperature threshold range;

[0037] If the judgment result is no: then continue to stay in the low-temperature slow charging temperature equalization 2 mode;

[0038] If the judgment result is yes: then enter the low-temperature slow charging temperature equalization 3 mode;

[0039] D5: When entering the low-temperature slow charging temperature equalization 3 mode:

[0040] Execution determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold;

[0041] If the judgment result is no: Then return to the charging state judgment mode;

[0042] If the judgment result is yes: Then execute determination 2: Determine whether △T1 meets the second temperature threshold;

[0043] If the judgment result is no: Then execute determination 3, if the judgment result is yes: Execute determination 4;

[0044] Execute determination 3: Determine whether △T1 meets the third temperature threshold;

[0045] If the judgment result is no: Then enter the low-temperature slow charge temperature equalization 1 mode;

[0046] If the judgment result is yes: Then enter the low-temperature slow charge temperature equalization 2 mode;

[0047] Execute determination 4: Determine whether Tmin meets the fourth temperature threshold;

[0048] If the determination result is no: Then continue to stay in the low-temperature slow charge temperature equalization 3 mode;

[0049] If the determination result is yes: Then enter the low-temperature slow charge heating mode;

[0050] D6: When entering the low-temperature slow charge heating mode:

[0051] Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold (Tamt ≤ 15°C);

[0052] If the judgment result is no: Then enter the charging state judgment mode;

[0053] If the judgment result is yes: Then execute determination 9;

[0054] Execute determination 9: Determine whether Tmin meets the ninth temperature threshold, where the ninth temperature threshold > the fourth temperature threshold;

[0055] If the judgment result is no: Then continue to stay in the low-temperature slow charge heating mode;

[0056] If the judgment result is yes: Then enter the low-temperature slow charge temperature equalization 3 mode.

[0057] It also includes step E. During the above entire control process, Tmax and ΔT0 are monitored in real time, and it is judged whether Tmax and ΔT0 meet the tenth temperature threshold. If the judgment result is yes, directly exit the current mode, enter the charging protection mode, and send an alarm signal to let the customer know the current state of the battery pack in time. If the judgment result is no, then continue to stay in the current mode to achieve the purpose of protecting the battery pack.

[0058] After entering the charging protection mode, Tmax and ΔT0 are monitored in real time, and it is judged whether Tmax and ΔT0 meet the eleventh temperature threshold. The eleventh temperature threshold > the tenth temperature threshold. If the judgment result is yes, exit the charging protection mode and return to the charging state judgment mode.

[0059] The power density described is achieved by changing the diameter and density of the copper wire.

[0060] The present invention first designs heating schemes with different power densities according to the different heat dissipation performances of single cells at different positions to reduce the temperature difference of a single module. Secondly, according to the different heat dissipation performances of single cells at different positions, local heat preservation design is carried out on the module to reduce the temperature difference of a single module. Then, according to the different heat dissipation performances of single cells at different positions, a dual heating system is designed to achieve independent control of different regions. Finally, a dual-loop heating control scheme is adopted in combination with the different heat dissipation performances of single cells at different positions, and the power batteries with requirements are heated according to the temperatures of the power batteries at different positions of different modules to reduce the temperature difference between a single module and the whole pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0062] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0064] As Figure 1 shown, the present invention includes the following steps:

[0065] The number of classifications for heat dissipation performance can be determined according to actual requirements. In theory, the more classifications, the more refined. Coupled with the subsequent heat insulation and control, the effect will be better. The following takes three categories as an example for illustration.

[0066] A: First, perform CFD simulation analysis on each battery cell in the battery. Classify them into categories A, B, and C according to the heat dissipation performance, and obtain the heat dissipation coefficients Ka and Kb of each category after classification, where Ka is greater than Kb;

[0067] Specifically, the design of heating power differentiation:

[0068] Based on the theoretical analysis results or CFD simulation analysis results, classify the battery cells in the module into three categories A, B, and C according to the single-cell heat dissipation performance (placing the module with balanced temperature in a low-temperature environment and the rate of temperature drop of the battery cells). The comparison of their heat dissipation performance is A > B > C.

[0069] The calculation method of the single-cell heating power of category A battery cells is as follows:

[0070] Pa = Ka * c * m * △t

[0071] In the formula: Pa—the single-cell heating power of category A battery cells; Ka—the heat dissipation coefficient of category A battery cells, usually obtained through CFD simulation analysis;

[0072] c—the specific heat capacity of the battery cell; m—the mass of a single battery cell; △t—the required temperature rise rate of the power battery pack.

[0073] The calculation method of the single-cell heating power of category B battery cells is as follows:

[0074] Pb = Kb * c * m * △t

[0075] In the formula: Pb—the single-cell heating power of category B battery cells; Kb—the heat dissipation coefficient of category B battery cells, usually obtained through CFD simulation analysis;

[0076] The calculation method of the single-cell heating power of category C battery cells is as follows:

[0077] Pc = Kc * c * m * △t

[0078] In the formula: Pc—the single-cell heating power of category C battery cells; Kc—the heat dissipation coefficient of category C battery cells, usually obtained through CFD simulation analysis;

[0079] Differentiated design of heat insulation measures

[0080] B: Divide the single-piece heating film into three areas, namely A1, B1, and C1, according to the types of corresponding battery cells. The comparison of their heating power densities is A1 > B1 > C1. The power density can be achieved by changing methods such as the diameter and density of copper wires, but it is not limited to the above two methods. And the on-off control of the single-piece heating film in different areas is carried out by setting separate corresponding on-off switches A2, B2, and C2; to ensure that the temperature comparison of the three types of battery cells A, B, and C during the heating stage is A > B > C, so as to balance and reduce the temperature difference caused by the difference in heat dissipation performance during the non-heating stage.

[0081] C: Add a thermal insulation layer to the outside of the type-A battery cells; for the battery cell categories distinguished above, additional thermal insulation measures are added to the type-A battery cells, such as methods like wrapping the battery cells with thermal insulation cotton. To reduce the difference in heat dissipation performance among various battery cells.

[0082] According to the theoretical analysis results or CFD simulation analysis results, divide the battery cells in the entire power battery pack into two categories, A and B, according to the heat dissipation performance of a single battery cell (this specification takes the dual heating system as an example for illustration, but it is not limited to the dual heating system). The comparison of their heat dissipation performance is A > B. Connect the heating film areas corresponding to the two types of battery cells A and B in series to form two independent heating circuits, and use two relays, A and B (not limited to relays), to independently control according to the temperature states of the two types of battery cells A and B.

[0083] D: Then, according to the ambient temperature, the maximum temperature Tmax of the whole pack, the minimum temperature Tmin of the whole pack, the minimum temperature Tmina of the type-A battery cells, the minimum temperature Tminb of the type-B battery cells, the maximum temperature difference △T0 = Tmax - Tmin of the whole pack, and the temperature difference △T1 = Tmina - Tminb between the minimum temperatures of the type-A and type-B battery cells, coordinate the on-off control of the single-piece heating film in the same area to achieve the temperature difference control of the single-module battery cells and the whole-pack battery cells; for the convenience of explanation, the control is described through different modes, specifically as follows:

[0084] D1: When entering the charging state judgment mode:

[0085] Execute determination 1: Judge whether Tamt satisfies the first temperature threshold (Tamt ≤ 10°C);

[0086] If the judgment result is no: Then enter the non-low-temperature charging mode, and control the on-off switches A2 and B2 to both execute the disconnection operation;

[0087] If the judgment result is yes: Then execute determination 2: Judge whether △T1 satisfies the second temperature threshold (-5°C ≤ △T1 ≤ 5°C);

[0088] If the determination result is no, then execute determination 3: If the judgment result is yes, then execute determination 4:

[0089] Execution determination 3: Determine whether △T1 meets the third temperature threshold, where the third temperature threshold is the maximum value of the second temperature threshold (△T1 > 5°C);

[0090] If the judgment result is no: Then enter the low-temperature slow charging temperature equalization 1 mode, at this time the A relay performs a closing operation and the B relay performs an opening operation;

[0091] If the judgment result is yes: Then enter the low-temperature slow charging temperature equalization 2 mode, at this time the A relay performs an opening operation and the B relay performs a closing operation;

[0092] Execution determination 4: Determine whether Tmin meets the fourth temperature threshold (Tmin ≤ 5°C);

[0093] If the judgment result is no: Then enter the low-temperature slow charging temperature equalization 3 mode, and both the A and B relays perform opening operations;

[0094] If the judgment result is yes: Then enter the low-temperature slow charging heating mode, and both the A and B relays perform closing operations;

[0095] D2: When entering the non-low-temperature charging mode:

[0096] Execution determination 5: Determine whether Tamt meets the fifth temperature threshold, where the first temperature threshold > the fifth temperature threshold (Tamt ≤ 5°C);

[0097] If the judgment result is no: Remain in the non-low-temperature charging mode;

[0098] If the judgment result is yes: Then return to the charging state judgment mode;

[0099] D3: When entering the low-temperature slow charging temperature equalization 1 mode:

[0100] Execution determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold, (Tamt ≤ 15°C);

[0101] If the judgment result is no: Then return to the charging state judgment mode;

[0102] If the judgment result is yes: Then perform execution determination 7: Determine whether △T1 meets the seventh temperature threshold, where the seventh temperature threshold is greater than 0°C and within the range of the second temperature threshold (△T1 ≥ 1°C);

[0103] If the judgment result is no: Remain in the low-temperature slow charging temperature equalization 1 mode;

[0104] If the judgment result is yes: Enter the low-temperature slow charging temperature equalization 3 mode;

[0105] D4: When entering the low-temperature slow charging temperature equalization 2 mode:

[0106] Execution determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold (Tamt ≤ 15°C);

[0107] If the judgment result is no: Then enter the charging state judgment mode;

[0108] If the judgment result is yes: Then execute determination 8: Determine whether △T1 meets the eighth temperature threshold, where the eighth temperature threshold < 0°C and is within the second temperature threshold range (△T1 ≤ -1°C)

[0109] If the judgment result is no: Then continue to stay in the low-temperature slow charging and temperature equalization 2 mode;

[0110] If the judgment result is yes: Then enter the low-temperature slow charging and temperature equalization 3 mode;

[0111] D5: When entering the low-temperature slow charging and temperature equalization 3 mode:

[0112] Execution determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold (Tamt ≤ 15°C);

[0113] If the judgment result is no: Then return to enter the charging state judgment mode;

[0114] If the judgment result is yes: Then execute determination 2: Determine whether △T1 meets the second temperature threshold (-5°C ≤ △T1 ≤ 5°C)

[0115] If the judgment result is no: Then execute determination 3, if the judgment result is yes: Execute determination 4;

[0116] Execution determination 3: Determine whether △T1 meets the third temperature threshold (△T1 > 5°C);

[0117] If the judgment result is no: Then enter the low-temperature slow charging and temperature equalization 1 mode;

[0118] If the judgment result is yes: Then enter the low-temperature slow charging and temperature equalization 2 mode;

[0119] Execution determination 4: Determine whether Tmin meets the fourth temperature threshold (Tmin ≤ 5°C)

[0120] If the determination result is no: Then continue to stay in the low-temperature slow charging and temperature equalization 3 mode;

[0121] If the determination result is yes: Then enter the low-temperature slow charging and heating mode.

[0122] D6: When entering the low-temperature slow charging and heating mode:

[0123] Execution determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold (Tamt ≤ 15°C);

[0124] If the judgment result is no: enter the charging state judgment mode;

[0125] If the judgment result is yes: execute Judgment 9;

[0126] Execute Judgment 9: Determine whether Tmin meets the ninth temperature threshold, and the ninth temperature threshold > the fourth temperature threshold (Tmin ≥ 10°C);

[0127] If the judgment result is no: continue to stay in the low-temperature slow charge heating mode;

[0128] If the judgment result is yes: enter the low-temperature slow charge temperature equalization 3 mode.

[0129] It also includes step E. During the above entire control process, monitor Tmax and △T0 in real time, and determine whether Tmax and △T0 meet the tenth temperature threshold (Tmax ≥ 30°C or △T0 ≥ 15°C); if the judgment result is yes, directly exit the current mode, enter the charging protection mode, and send an alarm signal to let the customer know the current state of the battery pack in a timely manner; if the judgment result is no, continue to stay in the current mode to achieve the purpose of protecting the battery pack.

[0130] After entering the charging protection mode, monitor Tmax and △T0 in real time, and determine whether Tmax and △T0 meet the eleventh temperature threshold, and the eleventh temperature threshold > the tenth temperature threshold (Tmax ≤ 20°C or △T0 ≤ 10°C). If the judgment result is yes, exit the charging protection mode and return to enter the charging state judgment mode.

[0131] During the above control process, the thresholds can be different according to the charge and discharge characteristics of different system battery cells, not limited to the above values, but should satisfy the following relationships:

[0132] Related to Tamt: The sixth temperature threshold > the first temperature threshold > the fifth temperature threshold;

[0133] Related to △T1: The third temperature threshold is the upper limit of the second temperature threshold, the seventh temperature threshold > 0°C, the eighth temperature threshold < 0°C, and the seventh and eighth temperature thresholds are within the range of the second temperature threshold;

[0134] Related to Tmin: The ninth temperature threshold > the fourth temperature threshold

[0135] Related to Tmax and △T0: The eleventh temperature threshold > the tenth temperature threshold

[0136] This implementation effectively reduces the difficult problem of large temperature differences during low-temperature charging of the battery pack through methods such as differential design of heating power, thermal insulation measures, and independent control of the dual heating system, which is of great significance for protecting the battery pack and the safe use of electric vehicles. The present invention classifies single-module battery cells according to the heat dissipation performance of different single battery cells; classifies the entire-pack battery cells according to the heat dissipation performance of different single battery cells; designs a regionally differentiated heating power density for the heating film according to the classification results of the battery cells in the single module; designs a differentiated thermal insulation measure according to the classification results of the battery cells in the single module; designs a dual heating system according to the classification results of the entire-pack battery cells to achieve independent control of various types of battery cells; obtains the battery pack temperature and the ambient temperature; designs various control modes such as a charging state judgment mode, a non-low-temperature charging mode, a low-temperature charging mode, a low-temperature slow charging heating mode, a low-temperature slow charging temperature equalization mode, a low-temperature slow charging temperature equalization 1 mode, a low-temperature slow charging temperature equalization 2 mode, and a low-temperature slow charging temperature equalization 3 mode, and realizes automatic switching of various control modes according to different temperature thresholds to achieve the purpose of minimizing the temperature difference of the battery pack, minimizing heating energy consumption, and shortening the charging time. At the same time, a charging protection mode is designed to protect the power battery and the driving safety of the electric vehicle. The battery pack temperature is displayed to the user in real time, and an alarm signal is issued after the charging protection mode is triggered.

[0137] According to the different heat dissipation performances of single battery cells at different positions, the present invention designs heating schemes with different power densities to reduce the temperature difference of the single module; designs local thermal insulation for the module according to the different heat dissipation performances of single battery cells at different positions to reduce the temperature difference of the single module; designs a dual heating system according to the different heat dissipation performances of single battery cells at different positions to achieve independent control of different regions. The different heat dissipation performances of single battery cells at different positions adopt a dual-loop heating control scheme, and the power batteries in need are heated according to the temperatures of the power batteries at different positions in different modules to reduce the temperature differences of the single module and the entire pack.

[0138] In the description of the present invention, it should be noted that for orientation terms, such as the terms "center", "horizontal", "vertical"

[0139] "direction", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the orientation and position relationships indicated are based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention.

[0140] It should be noted that the terms "comprising" and "having" in the description and claims of this application, as well as any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0141] Note that the above is only a preferred embodiment of the present invention and the application of technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the specific embodiments described herein. Without departing from the concept of the present invention, more other effective embodiments can also be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A thermal management control method for a power battery, characterized in that: It includes the following steps: A: First, perform CFD simulation analysis on each cell in the battery, classify them into categories A and B according to the heat dissipation performance, and obtain the corresponding cell heat dissipation coefficients Ka and Kb for each category after classification, where Ka is greater than Kb; B: Divide a single heating film into two regions A1 and B1 according to the type of the corresponding cell, and the heating power density ratio of the two regions is A1 > B1. And the on-off control of the single heating film in different regions is carried out by setting separate corresponding on-off switches A2 and B2; to ensure that the temperature comparison of the two types of cells A and B is A > B during the heating stage, so as to balance and reduce the temperature difference caused by the heat dissipation performance difference during the non-heating stage; C: Add a thermal insulation layer outside the cells of category A; D: Then, according to the ambient temperature, the maximum temperature Tmax of the whole pack, the minimum temperature Tmin of the whole pack, the minimum temperature Tmina of the cells of category A, the minimum temperature Tminb of the cells of category B, the maximum temperature difference of the whole pack △T0 = Tmax - Tmin, and the minimum temperature difference of the cells of categories A and B △T1 = Tmina - Tminb, coordinate the on-off control of the single heating film in the same region to achieve the temperature difference control of the single-module cells and the whole-pack cells; The specific steps of step D include the following steps: D1: When entering the charging state judgment mode: Execute determination 1: Judge whether Tamt meets the first temperature threshold; If the judgment result is no: Then enter the non-low-temperature charging mode, and control the on-off switches A2 and B2 to both perform the disconnection operation; If the judgment result is yes: Then execute determination 2: Judge whether △T1 meets the second temperature threshold; If the determination result is no, then execute determination 3: If the judgment result is yes: Then execute determination 4: Execute determination 3: Judge whether △T1 meets the third temperature threshold, and the third temperature threshold is the maximum value of the second temperature threshold; If the judgment result is no: Then enter the low-temperature slow charging temperature equalization 1 mode, at this time the A relay performs the closing operation, and the B relay performs the disconnection operation; If the judgment result is yes: Then enter the low-temperature slow charging temperature equalization 2 mode, at this time the A relay performs the disconnection operation, and the B relay performs the closing operation; Execute determination 4: Judge whether Tmin meets the fourth temperature threshold; If the judgment result is no: Then enter the low-temperature slow charging temperature equalization 3 mode, and both the A and B relays perform the disconnection operation; If the judgment result is yes: Then enter the low-temperature slow charging heating mode, and both the A and B relays perform the closing operation; D2: When entering the non-low-temperature charging mode: Execute determination 5: Judge whether Tamt meets the fifth temperature threshold, the first temperature threshold > the fifth temperature threshold; If the judgment result is no: Continue to stay in the non-low-temperature charging mode; If the judgment result is yes: Then return to enter the charging state judgment mode; D3: When entering the low-temperature slow charging temperature equalization 1 mode: Execute determination 6: Judge whether Tamt meets the sixth temperature threshold, the sixth temperature threshold > the first temperature threshold; If the judgment result is no: Then return to enter the charging state judgment mode; If the judgment result is yes: Then execute determination 7: Determine whether △T1 meets the seventh temperature threshold, where the seventh temperature threshold is greater than 0°C and within the second temperature threshold range; If the judgment result is no: Remain in the low-temperature slow charging temperature equalization 1 mode; If the judgment result is yes: Enter the low-temperature slow charging temperature equalization 3 mode; D4: When entering the low-temperature slow charging temperature equalization 2 mode: Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold; If the judgment result is no: Then enter the charging state judgment mode; If the judgment result is yes: Then execute determination 8: Determine whether △T1 meets the eighth temperature threshold, where the eighth temperature threshold is less than 0°C and within the second temperature threshold range; If the judgment result is no: Then continue to remain in the low-temperature slow charging temperature equalization 2 mode; If the judgment result is yes: Then enter the low-temperature slow charging temperature equalization 3 mode; D5: When entering the low-temperature slow charging temperature equalization 3 mode: Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold; If the judgment result is no: Then return to enter the charging state judgment mode; If the judgment result is yes: Then execute determination 2: Determine whether △T1 meets the second temperature threshold; If the judgment result is no: Then execute determination 3, if the judgment result is yes: Execute determination 4; Execute determination 3: Determine whether △T1 meets the third temperature threshold; If the judgment result is no: Then enter the low-temperature slow charging temperature equalization 1 mode; If the judgment result is yes: Then enter the low-temperature slow charging temperature equalization 2 mode; Execute determination 4: Determine whether Tmin meets the fourth temperature threshold; If the determination result is no: Then continue to remain in the low-temperature slow charging temperature equalization 3 mode; If the determination result is yes: Then enter the low-temperature slow charging heating mode; D6: When entering the low-temperature slow charging heating mode: Execute determination 6: Determine whether Tamt meets the sixth temperature threshold, where the sixth temperature threshold > the first temperature threshold; If the judgment result is no: Then enter the charging state judgment mode; If the judgment result is yes: Then execute determination 9; Execute determination 9: Determine whether Tmin meets the ninth temperature threshold, where the ninth temperature threshold > the fourth temperature threshold; If the judgment result is no: Then continue to remain in the low-temperature slow charging heating mode; If the judgment result is yes: Then enter the low-temperature slow charging temperature equalization 3 mode.

2. The power battery thermal management control method according to claim 1, characterized in that: It further includes step E. During the above entire control process, Tmax and △T0 are monitored in real time, and it is determined whether Tmax and △T0 meet the tenth temperature threshold; if the judgment result is yes, directly exit the current mode, enter the charging protection mode, and send out an alarm signal to let the customer know the current state of the battery pack in a timely manner; if the judgment result is no, then continue to remain in the current mode to achieve the purpose of protecting the battery pack.

3. The power battery thermal management control method according to claim 2, characterized in that: After entering the charging protection mode, monitor Tmax and △T0 in real time, and determine whether Tmax and △T0 meet the eleventh temperature threshold, where the eleventh temperature threshold > the tenth temperature threshold. If the judgment result is yes, exit the charging protection mode and return to the charging state judgment mode.

4. The power battery thermal management control method according to claim 3, characterized in that: The power density is distinguished by changing the diameter and density of the copper wire.

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