CN113782872A - Lithium battery pack and heating method thereof - Google Patents
Lithium battery pack and heating method thereof Download PDFInfo
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- CN113782872A CN113782872A CN202111080781.6A CN202111080781A CN113782872A CN 113782872 A CN113782872 A CN 113782872A CN 202111080781 A CN202111080781 A CN 202111080781A CN 113782872 A CN113782872 A CN 113782872A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/61—Types of temperature control
- H01M10/615—Heating or keeping warm
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
- H01M10/486—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for measuring temperature
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/63—Control systems
- H01M10/635—Control systems based on ambient temperature
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/65—Means for temperature control structurally associated with the cells
- H01M10/657—Means for temperature control structurally associated with the cells by electric or electromagnetic means
- H01M10/6571—Resistive heaters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Automation & Control Theory (AREA)
- Secondary Cells (AREA)
- Battery Mounting, Suspending (AREA)
Abstract
The embodiment of the invention provides a lithium battery pack and a heating method thereof, wherein the lithium battery pack comprises the following components: the heating film is folded to form a folding structure, the folding structure comprises a plurality of folding positions, the adjacent folding surfaces of the same folding position form folding spaces, and the plurality of battery cores are arranged in the plurality of folding spaces. According to the lithium battery pack provided by the embodiment of the invention, the problem that the temperature of the battery cell cannot be accurately controlled in the prior art is solved through the structural stacking mode that the battery cell is wrapped by the heating film, the purposes of ensuring the quick temperature rise of the battery cell and reducing the temperature rise of the battery cell in the discharging process are achieved, and the service life of the lithium battery pack is prolonged.
Description
Technical Field
The invention relates to a lithium battery pack technology, in particular to a lithium battery pack and a heating method of the lithium battery pack.
Background
Along with the continuous development of science and technology, the range of application of little power lithium cell group is more and more wide, begins to develop to direction of littleer volume, higher performance, like unmanned aerial vehicle, robot, electric tool etc. of sweeping the floor. However, at low ambient temperature, the viscosity of the electrolyte of the lithium battery pack is increased, the chemical reaction rate is reduced, the internal resistance and the polarization voltage are increased, so that the problems of rapid deterioration of the charging and discharging performance and even incapability of charging and discharging can occur, the battery can permanently damage the battery after working in a low-temperature environment for a long time, the service life of the battery is shortened, and the low-temperature characteristic of the battery seriously hinders the development and popularization of the product.
The heating strategy in the prior art is usually to stop or start heating when the temperature reaches a specified temperature, after the heating is stopped, if the external heat dissipation condition is suddenly improved, the temperature of the battery cell may be reduced, the heating film starts to work again, the heating film is frequently opened and closed, the service life of the heating film is reduced, and the probability of the heating film occurring in the environment with large wind speed change is obviously increased.
Disclosure of Invention
The embodiment of the invention provides a lithium battery pack and a heating method of the lithium battery pack, and solves the problem that the temperature of a battery cell cannot be accurately controlled in the prior art by wrapping the battery cell by a heating film folding structure.
In a first aspect, an embodiment of the present invention provides a lithium battery pack, including: the heating film is folded to form a folding structure, the folding structure comprises a plurality of folding positions, the adjacent folding surfaces of the same folding position form folding spaces, and the plurality of battery cores are arranged in the plurality of folding spaces.
Optionally, the heating film includes a first insulating film, a second insulating film and a heating resistance wire, the heating resistance wire is disposed between the first insulating film and the second insulating film, and the power density of the heating resistance wire in the two end regions of the heating film is smaller than the power density of the heating resistance wire in the middle region of the heating film.
Optionally, the power density of the two end regions of the heating film is less than or equal to 20% of the power density of the middle region of the heating film.
Optionally, the folding directions of adjacent folding positions in the folding structure are opposite.
Optionally, the battery pack further comprises a temperature sensor and a temperature control switch, the temperature sensor is arranged on at least one of the plurality of battery cells, the temperature sensor detects that the temperature of the plurality of battery cells is a first current temperature, the temperature control switch is arranged at the top of the plurality of battery cells, and the detection temperature of the temperature control switch is a second current temperature.
Optionally, when the lithium battery pack needs to be charged at a low temperature, if the first current temperature is higher than a first preset temperature, the lithium battery pack is charged; if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
Optionally, when the lithium battery pack needs to be discharged at a low temperature, if the first current temperature is higher than a second preset temperature, the lithium battery pack is controlled to be discharged; and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
Optionally, if the second current temperature of the heating film is greater than or equal to a third preset temperature in the heating process, the heating of the heating film is stopped and warning information is sent, wherein the third preset temperature is in a range of 40-50 ℃.
In a second aspect, an embodiment of the present invention further provides a heating method applied to any one of the lithium battery packs, including:
obtaining first current temperatures of the plurality of battery cells;
acquiring the current working state of the lithium battery pack, wherein the current working state comprises low-temperature charging and low-temperature discharging;
when the lithium battery pack needs to be charged at the low temperature, if the first current temperature is higher than a first preset temperature, the lithium battery pack is charged;
if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
Optionally, the method further includes:
when the lithium battery pack needs to be discharged at the low temperature, if the first current temperature is higher than a second preset temperature, controlling the lithium battery pack to discharge;
and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
According to the lithium battery pack and the heating method of the lithium battery pack, provided by the embodiment of the invention, the structure stacking mode that the heating film wraps the battery cell is adopted, so that the purposes of ensuring the quick temperature rise of the battery cell and reducing the temperature rise of the battery cell in the discharging process are achieved, and the service life of the lithium battery pack is prolonged.
Drawings
FIG. 1 is one of the structural diagrams of a heating film in the embodiment of the present invention;
FIG. 2 is a second structural diagram of a heating film according to an embodiment of the present invention;
FIG. 3 is a structural view of a foam in an embodiment of the present invention;
fig. 4 is a structural diagram of a lithium battery pack according to an embodiment of the present invention;
FIG. 5 is a block diagram of a lithium battery system according to an embodiment of the present invention;
fig. 6 is a flowchart illustrating a method for heating a lithium battery pack according to an embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Furthermore, the terms "first," "second," and the like may be used herein to describe various orientations, actions, steps, elements, or the like, but the orientations, actions, steps, or elements are not limited by these terms. These terms are only used to distinguish one direction, action, step or element from another direction, action, step or element. For example, the first speed difference may be referred to as a second speed difference, and similarly, the second speed difference may be referred to as a first speed difference, without departing from the scope of the present application. The first speed difference and the second speed difference are both speed differences, but they are not the same speed difference. The terms "first", "second", etc. are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
Referring to fig. 1, fig. 1 is a structural diagram of a heating film according to an embodiment of the present invention, and a lithium battery pack according to the embodiment includes: the heating film 10 is folded to form a folding structure, the folding structure includes a plurality of folding positions 101, adjacent folding surfaces of the same folding position 101 form a folding space 102, and the plurality of battery cells are disposed in the plurality of folding spaces 102.
In this embodiment, the heating film 10 is a Polyimide (PI) heating film 10, the PI heating film 10 is an insulating polymer material containing phthalimide or succinimide, and the PI heating film 10 has the advantages of small occupied volume, high heating efficiency, and the like, and is more advantageous to lightweight design. When the battery discharges at low temperature, if the external environment temperature is very low and the battery discharge current is very small, the heat generated by the battery core is very little, and the temperature of the battery core is possibly still very low, the battery core needs to be properly heated during discharging, so that the temperature of the battery core is increased, the discharge performance of the battery is improved, and the discharge time of the battery is prolonged. The electric core is very sensitive to the temperature, and high temperature can cause serious influence to the battery performance equally, and higher temperature can accelerate battery electrode degradation and electrolyte decomposition, causes irreversible damage to battery inner structure, if temperature sensor NTC became invalid, then heating film 10 can open the heating always, along with the extension of heating time, electric core temperature can far exceed the limit that its temperature allowed, need consider to carry out duplicate protection and report an emergency and ask for help or increased vigilance the output, improves its reliability. The heating film 10 has a rectangular shape as a whole, and is formed by bending a plurality of times in the present embodiment to form a folded structure, on which a plurality of folding positions 101 are provided, and optionally, folding directions of adjacent folding positions in the folded structure are opposite. As shown in fig. 1, the folding directions of the adjacent folding positions 101 are opposite, so that the heating film 10 forms an S-shaped bending, the adjacent folding surfaces of the same folding position 101 of the heating film 10 form a folding space 102, one battery cell is placed in each folding space 102, and accordingly, the plurality of battery cells are sequentially arranged in the plurality of folding spaces 102, so that a structure that the heating film 10 wraps the plurality of battery cells is formed, the battery cells are rapidly heated, meanwhile, the temperature rise of the battery cells in the discharging process is reduced, the heat exchange between the battery cells is enhanced, and the temperature rise and the temperature difference of the battery cells in the discharging process are reduced.
According to the lithium battery pack and the heating method of the lithium battery pack, the structure stacking mode that the heating film wraps the battery core is adopted, the quick temperature rise of the battery core is ensured, meanwhile, the temperature rise of the battery core in the discharging process is reduced, and the service life of the lithium battery pack is prolonged.
Optionally, the heating film 10 further includes a plurality of positioning holes 103, and the heating film 10 is fixedly connected to the plurality of battery cells through the plurality of positioning holes 103.
In the present embodiment, the whole fixed connection between the heating film 10 and the battery core is achieved by providing a plurality of positioning holes 103 on the heating film 10, for example, three positioning holes 103 are provided on the folding surface of each folding space 102, and the number of the positioning holes 103 can be adaptively adjusted according to actual situations, which is not specifically limited in the present embodiment.
Optionally, the heating film further comprises a conductive wire 20 and a positive and negative electrode connecting section 30, wherein one end of the conductive wire 20 is connected with the heating resistance wire, the other end of the conductive wire 20 is connected with the positive and negative electrode connecting section 30, and the positive and negative electrode connecting section 30 is fixedly connected with one end of the heating film 10.
In this embodiment, one end of the conductive wire 20 is connected to the heating resistance wire, and the other end of the conductive wire 20 is connected to an external heating device through the positive and negative electrode connecting sections 30. Specifically, the external heating device supplies the working current to the conductive wire 20 to cause the heating resistance wire to generate heat, so as to heat the battery core. Typically, the conductive wire 20 is connected to the end of a heating resistance wire.
Optionally, the heating film 10 includes a first insulating film, a second insulating film, and a heating resistance wire disposed between the first insulating film and the second insulating film.
In the present embodiment, the heating resistance wire is preferably made of nichrome, brass is selected as a second choice, and the heating wire is uniformly arranged between the first insulating film and the second insulating film and has a thickness of 0.05 mm. Illustratively, the heating wire traverses the whole heating film 10 in an S-shaped arrangement manner between two layers of insulating films, and the two layers of insulating films are used for preventing the heating wire from being in direct contact with the battery cell, so that the normal charging and discharging effects of the battery cell are affected.
Optionally, the power density of the heating resistance wire in the two end regions 104 of the heating film 10 is less than the power density of the heating resistance wire in the middle region 105 of the heating film 10, and the power density of the two end regions 104 of the heating film is less than or equal to 20% of the power density of the middle region 105 of the heating film.
Referring to fig. 2, fig. 2 is a structural diagram of the heating film 10 in this embodiment, the heating resistance wires are divided into a middle region 105 and two end regions 104, wherein the resistance wires of the two end regions 104 are sparsely arranged, or the width of the heating wires is wider, so as to implement a low power density design, the resistance wires and the heating wires of the middle region 105 are densely arranged, the width of the heating wires is narrower, so as to implement a high power density design, the total thickness after molding is 0.2mm, and a terminal lead wire is provided to connect with an external heating device. In this embodiment, the heating power of both end regions 104 is 1.0W, the heating power of the middle region 105 is 34.99W, and the power density of the low power region heating film 10 is 13.6% of the power density of the middle region 105 heating film 10. For example, the area of the two end regions 104 may be 1/4 of the area of the middle region 105, or 1/3 of the area of the middle region 105, and the specific heating power distribution needs to be obtained by a simulation means in combination with requirements of the ambient temperature, the battery temperature rise rate, the maximum cell temperature difference, and the like, which is not specifically limited in this embodiment. Specifically, the small-power lithium battery pack in this embodiment is applied to the field of unmanned aerial vehicles, and requires a low-temperature charging environment temperature of-20 machines, a cell temperature rise rate of >2K/min, and a maximum temperature difference of < 6K. Except for the leftmost and rightmost electric cores, a PI heating film 10 region is uniformly arranged between every two other electric cores, the heating region is shared to heat one single face of the electric cores, the utilization efficiency of the heating film 10 is improved, the use amount of the heating film 10 is reduced, the low-power region heating film 10 is only attached to the leftmost and rightmost electric cores, and the leftmost and rightmost electric cores are subjected to heating compensation. The non-uniform PI heating film 10 heating power's arrangement mode can compensate certain heat dissipation capacity of end electric core about the most, ensures that electric core is heating to appointed temperature after, the homogeneity of temperature distribution between the electric core, at the battery cooling in-process, can reduce the difference in temperature between the electric core, postpones the time that the maximum difference in temperature appears simultaneously.
Optionally, the heating film further comprises a plurality of strip-shaped foam 40, and the strip-shaped foam 40 is adhered to the surface of the heating film 10.
Referring to fig. 3, fig. 3 is a structural diagram of the foam 40 in this embodiment, the foam 40 is arranged around the battery cell, and the foam 40 is provided with a back adhesive, and is directly adhered to the battery pack after the batteries are grouped, so as to enhance the heat preservation effect of the battery cell. Referring to fig. 4, fig. 4 is a structural diagram of the lithium battery pack in this embodiment, a plurality of battery cells 50 are sequentially stacked, the leftmost battery cell and the rightmost battery cell are one, and the other battery cells are paired to form a group, and the battery cells are separated by foam 40. Specifically, in the process of assembling the lithium battery pack, during assembly, the 1 st electric core is fixed firstly, then the 10 region of the heating film is attached, the 10 th heating film is folded, the 2 nd electric core is placed to realize single-side attachment, the 3 rd electric core is placed later, the 10 th heating film is gradually folded and the electric core is placed, and finally grouping is performed. The lithium battery pack in this embodiment has 12 cells 50 in total, except for two end portions, the remaining 10 cells are all heating films 10 whose single surfaces share the same partial area, and exemplarily, the heating films 10 heat the No. 5 cell and the No. 6 cell at the same time. The heating film 10 and the battery core are tightly attached through a double-sided adhesive tape or a heat-conducting double-sided adhesive tape, the thickness of the heating film is 0.05mm, and the double-sided adhesive tape or the heat-conducting double-sided adhesive tape is fixed on the surface of the battery core at the beginning.
In this embodiment, as can be known from simulation experiment data, in the lithium battery pack designed at this time, the heating powers of the two end regions 104 and the middle region 105 are both 1.0W, the heating power of the 101 region is 34.39W, and the total heating power is 36.39W, and a simulation result shows that the temperature of the battery cell is raised from-20 junction ambient temperature to 20 ℃, the maximum temperature difference of the battery cell is 2.55 max, the temperature distribution between the battery cells is very uniform, and the temperature rise rate is 3.26K/min. After the electric cores are heated to 20 times, the electric cores are cooled at-20 times of ambient temperature, the temperature difference between the electric cores is increased and then reduced, the maximum temperature difference is 5.7, and the temperature difference appears 1560s after the heating is stopped.
Referring to fig. 5, fig. 5 is a structural diagram of a lithium battery pack system in this embodiment, the lithium battery pack system includes a lithium battery pack 1, a control board 2, an upper case 3, and a lower case 4, and since the thermal conductivity of the heating film 10 itself is not low and there is thermal capacity, when the electric core discharges with a large rate, the temperature rise of the electric core is reduced by the heating film 10 compared with the structural arrangement scheme without the heating film 10. Optionally, the battery pack further comprises a temperature sensor and a temperature control switch, the temperature sensor is arranged on at least one of the plurality of battery cells, the temperature sensor detects that the temperature of the plurality of battery cells is a first current temperature, the temperature control switch is arranged at the top of the plurality of battery cells, and the detection temperature of the temperature control switch is a second current temperature. Illustratively, the Negative Temperature Coefficient (NTC) of the Temperature sensor is placed on the No. 6 Battery cell, the Temperature acquisition module acquires a resistance value of the NTC and converts the resistance value into a Temperature value to obtain a first current Temperature T1 of the Battery cell, and the Battery charging or discharging state is determined by a Battery Management System (BMS). The temperature control switch is arranged at the peak of the central battery core, and the detected temperature is a second current temperature T2.
Optionally, when the lithium battery pack needs to be charged at a low temperature, if the first current temperature is higher than a first preset temperature, the lithium battery pack is charged; if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
In this embodiment, the first preset temperature is T3, an external power source is connected during low-temperature charging, if T1> T3 and T3 is 15-18 ℃, the battery is directly charged, otherwise, the battery is not charged, the PI heating film is directly supplied with power to heat the battery cell, and when T1 is T3+ (2-5) ° c, the heating film is turned off to start charging the battery, and the heating film is turned on and off with a temperature difference of [ T3+ (2-5) -T1] ° c, so that frequent turning on and turning off of the heating film can be avoided.
Optionally, when the lithium battery pack needs to be discharged at a low temperature, if the first current temperature is higher than a second preset temperature, the lithium battery pack is controlled to be discharged; and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
In this embodiment, the second preset temperature is T4, and during low-temperature discharge, if T1> T4 and T4 is 5-8 ℃, the current situation is maintained, otherwise, a small current I is used to heat the heating film, I is 0.05-0.1C, and heating is stopped until T1 is T4+ (2-5) ℃ so as to properly increase the temperature of the battery cell itself in a low-temperature environment and increase the discharge time of the low-power battery. Similarly, the heating film is opened and closed by a temperature return difference of [ T4+ (2-5) -T1] ° C, so that frequent opening and closing of the heating film can be avoided.
Optionally, if the second current temperature of the heating film is greater than or equal to a third preset temperature in the heating process, the heating of the heating film is stopped and warning information is sent, wherein the third preset temperature is in a range of 40-50 ℃.
In this embodiment, the third preset temperature is T5, and in the heating process of the heating film, once the temperature T2 of the thermostat is T5 and the temperature T5 is 40-50 ℃, the power supply of the I heating film is forcibly turned off, and meanwhile, an alarm message is issued to prompt the user that the NTC sensor may fail at this time.
The lithium battery pack provided by the embodiment has the advantages that the structure of wrapping the battery core by the heating film is stacked, the purpose of ensuring the quick temperature rise of the battery core is achieved, the temperature rise of the battery core in the discharging process is reduced, and the service life of the lithium battery pack is prolonged.
Fig. 6 is a heating method of a lithium battery pack according to an embodiment of the present invention, where the heating method is applied to the lithium battery pack in the above embodiment, specifically, the method includes:
and step 610, acquiring first current temperatures of the plurality of battery cells.
The temperature sensor is arranged on at least one battery cell in the plurality of battery cells, and the temperature sensor detects that the temperature of the plurality of battery cells is a first current temperature. Illustratively, the Negative Temperature Coefficient (NTC) of the Temperature sensor is disposed on the No. 6 Battery cell, the Temperature acquisition module acquires a resistance value of the NTC and converts the resistance value into a Temperature value, a first current Temperature of the Battery cell is obtained, and a Battery charging or discharging state is determined by a Battery Management System (BMS).
And step 620, acquiring the current working state of the lithium battery pack, wherein the current working state comprises low-temperature charging and low-temperature discharging.
In this embodiment, first temperature of predetermineeing is the first temperature of predetermineeing that the user set up, when being less than this first temperature of predetermineeing, indicates that electric core needs to heat this moment, and then control this moment is carried out the circular telegram to the heating film generates heat and gives electric core with heat transfer, thereby improves the current temperature of electric core.
And 630, when the lithium battery pack needs to be charged at the low temperature, if the first current temperature is higher than a first preset temperature, charging the lithium battery pack.
In this embodiment, the second preset temperature is a heating upper limit temperature set by a user, and when the electric core reaches the temperature, the heating film stops heating the electric core.
And 640, if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
In this embodiment, when the lithium battery pack is in a charging state, a first current temperature of the NTC is obtained in real time, the refresh time requirement is less than 1s, the current time is set to 1s, and the current time is compared with a first preset temperature of a preset threshold, where the first preset temperature is 15-185, and the first preset temperature in this example is 15 cases, if the first current temperature is less than 15 degrees, the external power source directly supplies power to the heating film to heat the heating film, otherwise, the external power source directly charges the battery cell, the current temperature is obtained by continuously refreshing, the current temperature is continuously increased and compared with a preset threshold, which is the first preset temperature plus (2-5) DEG C, and the current threshold is set to 20 degrees, and once the current temperature reaches 20 deniers, the heating is stopped, and the external power source starts to charge the battery. The strategy can ensure that the temperature of the battery cell is always higher than a first preset temperature when the battery cell is charged, and meanwhile, the heating film is opened and closed by a temperature return difference before [ the first preset temperature + (2-5) -the current temperature ], so that frequent opening and closing of the heating film are avoided. The temperature when this example electricity core charges is higher than 15 electricity all the time, and the temperature return difference is 5 degrees.
When charging at low temperature, access external power supply, if first current temperature > first preset temperature, first preset temperature is 15 ~ 185, then directly charge to the battery, otherwise not charge to the battery, directly power supply heats electric core for PI heating film, when first current temperature is first preset temperature + (2 ~ 5) DEG C, the heating film is closed, begin to charge to the battery, the heating film opens and closes and has the temperature return difference before [ first preset temperature + (2 ~ 5) -current temperature ], can avoid frequent opening and closing of heating film. Specifically, when low temperature charges, the NTC gathers electric core temperature, if the temperature is higher than a certain appointed temperature, external power source directly charges to the battery, otherwise the external power source power supply heats electric core for the heating film, the temperature when guaranteeing that electric core charges is higher than a certain setting value all the time, opening and closing of PI heating film sets up the temperature return difference, can avoid frequent opening and closing of heating film, prolongs the life of heating film.
Optionally, the method further includes: when the lithium battery pack needs to be discharged at the low temperature, if the first current temperature is higher than a second preset temperature, controlling the lithium battery pack to discharge;
and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
When the lithium battery pack is in a discharging state, if the first current temperature is lower than a second preset temperature, and the second preset temperature is 5-85 degrees, the battery is discharged at a low current I to supply power to the PI heating film, wherein the I is 0.05C-0.1C, C is the capacity and the Ah is a unit, otherwise, the existing state is maintained, and the battery does not act. When first current temperature < second preset temperature, the temperature rise power of battery this moment derives from the two sides, and firstly, insert the heating film after, battery self discharge heat production, secondly the heat production of PI heating film, directly heats electric core, and the temperature rise rate can obtain obviously rising, this I be 0.05C. Constantly refreshing the temperature of the current temperature, wherein the refreshing time is also required to be less than 1s, the refreshing time is 1s, the temperature is compared with a preset threshold value of second preset temperature + (2-5) DEG C in real time, once the temperature reaches the second preset temperature + (2-5) DEG C, heating is stopped, the second preset temperature is 5 and the threshold value is set to be 10. The strategy can properly increase the temperature of the battery core when the battery discharges at low temperature, and realize longer discharge time of the lithium battery pack. Before the temperature return difference for opening and closing the PI heating film is set to be [ the second preset temperature + (2-5) -the current temperature ], frequent opening and closing of the heating film can be avoided, the service life of the PI heating film is prolonged, and the temperature return difference set at this time is 5 degrees.
During low-temperature discharge, if the first current temperature is greater than the second preset temperature, and the second preset temperature is 5-85, the current situation is maintained unchanged, otherwise, the heating film is heated by adopting a small current I, wherein the I is 0.05-0.1C, and the heating is stopped until the current temperature is equal to the second preset temperature plus (2-5) DEG C, so that the self temperature of the battery cell in the low-temperature environment can be properly increased, and the discharge time of the small power battery is prolonged. Similarly, the heating film is opened and closed by the temperature return difference before the [ second preset temperature + (2-5) -first current temperature ], so that frequent opening and closing of the heating film can be avoided. Specifically, during low-temperature discharge, when the cell temperature is low, a small current supplies power to the PI heating film, the cell temperature is rapidly increased, and the battery discharge time is increased.
Optionally, second current temperatures of the plurality of battery cells are obtained;
if the second current temperature of the heating film is greater than or equal to a third preset temperature in the heating process, stopping heating the heating film and giving out warning information, wherein the third preset temperature is 40-50 ℃.
In this embodiment, a temperature control switch is additionally disposed at a peak of the central electric core, the temperature control switch is disposed on top of the plurality of electric cores, and a detected temperature of the temperature control switch is a second current temperature. In the heating process, if the temperature sensor fails, once the temperature continues to rise to the specified temperature, the temperature control switch acts to forcibly disconnect the power supply of the PI heating film, the battery cell is protected from being overheated, and meanwhile, alarm information is output to prompt that the NTC possibly fails. No matter in the low-temperature charging or low-temperature discharging process, the temperature control switch is connected in series in a path of the PI heating film, once the PI heating film is started, current is generated, the temperature control switch is automatically switched on, once the current temperature is monitored to be the third preset temperature, and the third preset temperature is 40-500, the power supply of the PI heating film is forcibly switched off, heating is stopped, meanwhile, an alarm signal is issued, the fact that the NTC is possibly damaged is prompted to a user, and the third preset temperature is set to be 50. It should be noted that, the maximum allowable operating temperature of the lithium battery pack is generally 60 hours, the temperature-controlled switch needs to ensure that the cell temperature is powered off from the PI heating film before reaching the maximum allowable temperature, and the specific temperature set value is related to the selected position and the given margin.
According to the heating method of the lithium battery pack, when low-temperature charging is carried out, the NTC acquires the temperature of the battery core, if the temperature is higher than a certain specified temperature, the external power supply directly charges the battery, otherwise, the external power supply supplies power to the heating film to heat the battery core, the temperature when the battery core is charged is always higher than a certain given value, the temperature return difference is set when the PI heating film is opened and closed, frequent opening and closing of the heating film are avoided, and the service life of the heating film is prolonged; during low-temperature discharge, when the temperature of the battery core is lower, the small current supplies power to the PI heating film, the temperature of the battery core is rapidly increased, and the discharge time of the battery is prolonged.
The foregoing is a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and refinements can be made without departing from the principle described in the present application, and these modifications and refinements should be regarded as the protection scope of the present application.
Claims (10)
1. A lithium battery pack, comprising: the heating film is folded to form a folding structure, the folding structure comprises a plurality of folding positions, the adjacent folding surfaces of the same folding position form folding spaces, and the plurality of battery cores are arranged in the plurality of folding spaces.
2. The lithium battery pack as claimed in claim 1, wherein the heating film comprises a first insulating film, a second insulating film, and a resistance heater wire disposed between the first insulating film and the second insulating film, wherein a power density of the resistance heater wire in a region at both ends of the heating film is smaller than a power density of the resistance heater wire in a region in the middle of the heating film.
3. The lithium battery pack of claim 2, wherein the power density of the regions at the two ends of the heating film is less than or equal to 20% of the power density of the region in the middle of the heating film.
4. The lithium battery pack of claim 1, wherein adjacent fold locations in the folded configuration are folded in opposite directions.
5. The lithium battery pack of claim 1, further comprising a temperature sensor disposed on at least one of the plurality of cells, the temperature sensor configured to detect a first current temperature of the plurality of cells, and a temperature-controlled switch disposed on a top of the plurality of cells, the temperature-controlled switch configured to detect a second current temperature of the plurality of cells.
6. The lithium battery pack according to claim 5, wherein when the lithium battery pack needs to be charged at a low temperature, if the first current temperature is higher than a first preset temperature, the lithium battery pack is charged; if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
7. The lithium battery pack according to claim 5, wherein when the lithium battery pack requires low-temperature discharge, the lithium battery pack is controlled to discharge if the first current temperature is higher than a second preset temperature; and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
8. The lithium battery pack as claimed in claim 5, wherein if the second current temperature of the heating film is greater than or equal to a third preset temperature during the heating process, the heating of the heating film is stopped and a warning message is issued, and the third preset temperature is in a range of 40 to 50 ℃.
9. A heating method applied to the lithium battery pack according to any one of claims 1 to 8, comprising:
obtaining first current temperatures of the plurality of battery cells;
acquiring the current working state of the lithium battery pack, wherein the current working state comprises low-temperature charging and low-temperature discharging;
when the lithium battery pack needs to be charged at the low temperature, if the first current temperature is higher than a first preset temperature, the lithium battery pack is charged;
if the first current temperature is less than or equal to the first preset temperature, heating the heating film until the first current temperature is equal to the sum of the first preset temperature and a first temperature return difference, wherein the first preset temperature is 15-18 ℃, and the range of the first temperature return difference is 2-5 ℃.
10. The method of claim 9, further comprising:
when the lithium battery pack needs to be discharged at the low temperature, if the first current temperature is higher than a second preset temperature, controlling the lithium battery pack to discharge;
and if the first current temperature is less than or equal to the second preset temperature, heating the heating film by adopting a first current until the first current temperature is equal to the sum of the second preset temperature and a second temperature return difference, wherein the range of the second preset temperature is 5-8 ℃, the range of the second temperature return difference is 2-5 ℃, and the range of the first current is 0.05-0.1 ℃.
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