CN111948543B - Thermal runaway chain reaction judgment system and method for energy storage battery pack - Google Patents
Thermal runaway chain reaction judgment system and method for energy storage battery pack Download PDFInfo
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- CN111948543B CN111948543B CN202010700595.7A CN202010700595A CN111948543B CN 111948543 B CN111948543 B CN 111948543B CN 202010700595 A CN202010700595 A CN 202010700595A CN 111948543 B CN111948543 B CN 111948543B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
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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
- H01M10/44—Methods for charging or discharging
- H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
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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
- H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
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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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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a thermal runaway chain reaction judgment system and method for an energy storage battery pack. According to the thought, a battery thermal runaway test is designed, so that the triggered power and energy, and the released power and energy can be quantitatively reflected; in the testing process, two factors of direct heating of the adjacent batteries on the contact surfaces and indirect heating of smoke on the side surfaces of the adjacent batteries are considered, so that the design is closer to the actual situation. When the power and the energy of indirect flue gas heating of the adjacent side batteries are finally calculated, the difference between the actual battery module and the test battery is considered, the number of the batteries in the actual battery module is large, and the flue gas heating effect is dispersed, so that an n/3 treatment mode is introduced.
Description
[ technical field ] A
The invention belongs to the technical field of battery pack thermal runaway judgment, and relates to a system and a method for judging thermal runaway chain reaction of an energy storage battery pack.
[ background ] A method for producing a semiconductor device
In recent years, many fire accidents occur in lithium ion battery energy storage power stations, particularly in korea, 29 accidents have occurred so far, and the safety problem of the energy storage battery has attracted high attention inside and outside the industry. Because the material that the lithium ion energy storage battery adopted is combustible material, for example, electrolyte is combustible organic electrolyte, diaphragm and graphite negative pole are also combustible material to energy storage battery can take place thermal runaway reaction under the abuse condition, these all make lithium ion energy storage battery have potential safety risk, and when lithium ion energy storage battery is in abnormal operating condition (overcharge, overheated etc.), can initiate lithium ion energy storage battery's thermal runaway reaction, and then just probably the incident such as the fire, burning even explosion appears. The thermal runaway refers to the phenomenon that after an energy storage battery is stimulated by an external stimulus, complex physicochemical and electrochemical side reactions occur inside the battery, the side reactions often have a heat release effect, the heat release effect can further increase the temperature of the battery until large-scale heat release side reactions occur inside the battery, at the moment, the surface temperature of the battery can rapidly rise (approximately linearly rise), and the consequence is that the internal pressure of the battery is rapidly increased, a pressure release valve is broken, a large amount of high-temperature gas and liquid are sprayed out, and the high-temperature gas and liquid can ignite under certain conditions and then burn violently.
It is known from accident reports and related research documents of battery energy storage power stations that individual batteries in a lithium ion energy storage power station further form a thermal runaway chain reaction after thermal runaway occurs, that is, thermal runaway of individual batteries causes adjacent batteries to generate thermal runaway successively, so as to cause a global fire accident. The reason for triggering the thermal runaway chain reaction is that the external energy impact on the battery exceeds the triggering critical condition of the thermal runaway reaction of the battery, and the energy released by the thermal runaway of the battery exceeds the critical energy for triggering the thermal runaway reaction of the battery.
In order to improve the safety of the energy storage power station, various measures are required to prevent the thermal runaway chain reaction of the lithium ion energy storage battery from occurring, or comprehensive protection measures are required to be taken in a targeted manner according to the severity of the thermal runaway chain reaction of the lithium ion energy storage battery to inhibit the speed and the strength of the thermal runaway chain reaction. Therefore, the critical condition of the thermal runaway chain reaction of the lithium ion energy storage battery needs to be judged, and only the targeted protection measures can be taken, for example, when the energy released by the thermal runaway of the battery is judged to exceed the critical energy for triggering the thermal runaway reaction of the battery, and is easy to occur or is possible to occur the thermal runaway chain reaction, the corresponding protection structure design and the protection measures need to be designed in an enhanced manner, and the dosage and the spraying requirements of the fire extinguishing agent also need to be enhanced in the configuration of a fire-fighting system; when the energy released by the battery thermal runaway is judged to be insufficient to trigger the critical energy of the battery thermal runaway reaction, and the battery thermal runaway reaction is not easy to occur or has low possibility, the requirements can be met by adopting a conventional protection design and a conventional fire-fighting fire-extinguishing configuration.
Therefore, the method for quantitatively judging the critical condition of the thermal runaway chain reaction of the lithium ion energy storage battery has important significance for improving the safety of the energy storage power station and optimizing and designing the safety protection measures of the energy storage system. However, a corresponding determination method and means are still lacking. The conventional method is that for a lithium ion energy storage battery pack or a lithium ion energy storage module, one battery is thermally out of control directly in an external excitation source stimulation mode, and then whether chain reaction occurs or not is observed. Most importantly, the method judges whether the chain reaction occurs or not only from the phenomenon, and the critical conditions of the chain reaction cannot be determined, so that a quantitative basis cannot be provided for the thermal management, protection design and fire extinguishing system design of the battery, for example, if the thermal runaway chain reaction of the battery is observed through the test of the battery pack, if the thermal runaway is inhibited by a method of reducing the temperature through forced heat dissipation, the thermal runaway can be inhibited by adopting large heat dissipation power or achieving large cooling effect of the battery, and the data with reference values cannot be provided through the prior art.
In the prior art, a test method is used, for example, overcharging or heating test is performed on one battery in a battery pack, and whether thermal runaway chain reaction occurs or not is actually judged through pressure test.
Although this method is simple and effective, it is impossible to extract the critical condition of the thermal runaway chain reaction of the battery, i.e. the judgment basis, i.e. this method only needs to perform the experiment of the thermal runaway chain reaction again only for a specific battery pack after the same battery is used and replaced by another battery module and another grouping method. Moreover, the method can only see whether the chain reaction occurs, and can not provide a basis for the design of the battery, the design of the battery pack, the safety protection structure design of the system and the heat dissipation design.
[ summary of the invention ]
The invention aims to solve the problems in the prior art and provides a system and a method for judging the thermal runaway chain reaction of an energy storage battery pack.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a method for judging thermal runaway chain reaction of an energy storage battery pack comprises the following steps:
calculating the energy required by one battery thermal runaway in the battery pack triggered by overcharge;
calculating the energy released after the battery is triggered by the overcharge thermal runaway;
judging whether the battery pack has thermal runaway chain reaction;
under a certain overcharge power, when the energy required by the battery for causing the thermal runaway is more than or equal to the energy released after the triggering of the battery for causing the thermal runaway, the battery is under the overcharge power: thermal runaway chain reaction can not occur; otherwise, the battery at the overcharge power: a thermal runaway chain reaction can occur.
The method is further improved in that:
in the step 1, a specific method for calculating the energy required by the thermal runaway of the battery triggered by the overcharge is as follows:
step 1-1, fully charging the battery according to an operation instruction for battery delivery;
step 1-2, closely attaching 3 batteries to each other, and arranging a temperature measuring device with the thickness of 1-10mm between the batteries and on the side surface of the battery, which is in contact with air; the outer sides of the two outermost batteries are tightly attached with a layer of high heat resistance material;
step 1-3, overcharge testing was performed on the cells using various powers ranging from 0.1P 0 ～10P 0 In which P is 0 Is the rated power of the battery;
step 1-4, recording the moment when the thermal runaway of the battery occurs, and calculating the overcharged energy E:
E＝∫f(P 1 )dt
wherein, P 1 Is the power of overcharge, t is the time of overcharge;
step 1-5, when the battery power is reduced to a certain value, the battery can not generate thermal runaway, and the value is the minimum power P generated by the thermal runaway of the battery min ；
Step 1-6, drawing a battery surface temperature-time curve in an overcharge experiment;
and 1-7, drawing a power-energy curve for charging the battery, wherein the curve represents a critical value of the battery for triggering thermal runaway under an overcharge condition, the upper part of the curve represents that the battery has thermal runaway, and the lower part of the curve represents that the battery has no thermal runaway.
In the step 2, a specific method for calculating the energy released after the battery overcharge thermal runaway trigger is as follows:
step 2-1, recording the temperature between the batteries at two sides of the overcharged battery when the step 1-3 is executed, and drawing a surface temperature-time curve of the overcharged battery;
step 2-2, comparing the battery surface temperature-time curves drawn in the step 1-6, searching the battery surface temperature-time curve corresponding to the closest heating test, and estimating overchargeElectric battery surface heating power P 2 And calculating the heat generation energy Q of the overcharged battery surface based on the calculated heat generation energy Q 1 ：
Q 1 ＝∫f(P 2 )dt
The heating energy is the heating energy of the contact surface of the adjacent battery;
step 2-3, drawing a temperature-time curve of the side face of the adjacent battery, which is in contact with the air; finding the battery surface temperature-time curve corresponding to the closest heating test, and estimating the heating power P of the smoke to the adjacent battery 3 And calculating the heating energy Q based on the calculated values 2 ：
Q 2 ＝∫f(P 3 )dt
Said heating energy Q 2 The heating energy of the contact surface between the adjacent battery and the air;
step 2-4, calculating the energy Q released after the battery overcharging thermal runaway is triggered:
where n is the number of cells in a battery module or battery box in which the cells are grouped.
The step 3 specifically comprises the following steps:
when E is larger than or equal to Q, the battery does not generate thermal runaway chain reaction under the overcharge power;
when E < Q, thermal runaway chain reaction of the battery can occur under the overcharge power.
The utility model provides an energy storage battery group thermal runaway chain reaction judgement system, includes:
the battery overcharge energy calculation module is used for calculating overcharge energy when the battery is in thermal runaway;
the battery overcharge thermal runaway release energy calculation module is used for calculating the release energy of the battery after thermal runaway;
and the judging module is used for judging whether the thermal runaway chain reaction occurs in the battery according to the overcharged energy and the released energy.
A test device, comprising:
the testing box is internally provided with 3 batteries which comprise overcharged batteries and adjacent batteries arranged on two sides of the overcharged batteries; the top, two sides and the front-back spacing of the 3 batteries and the inner side of the box body of the test box are consistent with the distance between the battery in the battery module and the box body;
a temperature measuring device including a first temperature sensor disposed between the battery and the battery, and a second temperature sensor of a side of the battery that is in contact with air;
the thermal resistance layer is arranged on the outer side surfaces of the two outermost batteries;
the upper computer is connected with the temperature measuring device and internally provided with the thermal runaway chain reaction judgment system of the energy storage battery pack according to claim 5.
The test device is further improved in that:
and a third temperature sensor is also arranged above the safety valve of the battery and used for recording the open fire temperature of the combustion gas-liquid mixture sprayed out in the thermal runaway process.
The thickness of the first temperature sensor and the second temperature sensor is 1-10 mm.
Compared with the prior art, the invention has the following beneficial effects:
the invention approximately quantificationally provides the basis of whether the battery has chain reaction or not, and the related numerical value and the judgment step can be used as the basis of the safety protection design of the battery, such as in the heat management of the battery; the calculated heating power and energy of the battery can be used for the heat dissipation design of the battery, and the heating power and energy of the battery are lower than the critical condition of thermal runaway of the battery through heat dissipation, or a thermal protection material is introduced in the safety design of the battery; the thermal protection parameter indexes which need to be met by the thermal protection material are designed according to the calculated thermal runaway heating power and energy of the battery, or when a battery fire-fighting system is designed; the calculated heating power and energy of the thermal runaway of the battery are used for designing the amount of the adopted cooling fire extinguishing medium, so that the fire extinguishing dosage required to be configured is calculated.
[ description of the drawings ]
In order to more clearly explain the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic structural view of a battery module, in which (a) is a front view and (b) is a plan view;
FIG. 2 is a schematic structural view of a test chamber of the present invention, wherein (a) is a front view and (b) is a top view;
FIG. 3 is a schematic view showing the structure of a battery pack in a test chamber according to the present invention;
fig. 4 is a power-energy curve for battery charging.
Wherein: 1-a battery module; 2-a test chamber; 3-a first temperature sensor; 4-a second temperature sensor; 5-thermal resistance layer.
[ detailed description ] embodiments
In order to make the objects, 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 with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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 invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined or explained in subsequent figures.
In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. are used for indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually arranged when the product of the present invention is used, the description is merely for convenience and simplicity, and the indication or suggestion that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, cannot be understood as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
Furthermore, the term "horizontal", if present, does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the embodiments of the present invention, it should be further noted that unless otherwise explicitly stated or limited, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The invention is described in further detail below with reference to the accompanying drawings:
the invention discloses a method for judging thermal runaway chain reaction of an energy storage battery pack, which comprises the following steps of:
1. calculating the energy required to trigger thermal runaway of the battery by overcharge:
1.0 the test environment is a semi-closed test chamber 2, the design of the test chamber is as follows: the distance between the box body and the battery is consistent with the distance between the box body of the battery module 1 and the battery in the module; the size of a vent of the test box is reduced in an equal proportion according to the size of the vent of the battery module box body and the number of batteries; as shown in fig. 1 and 2, fig. 1 is a front view and a top view of the battery module, and fig. 2 is a front view and a top view of the test chamber, in which the upper, left, right, front, and rear spacing distances of the test battery and the chamber in the test chamber are maintained to be identical to the distances of the battery and the chamber in the battery module.
1.1 fully charging the battery according to the operation instruction of battery delivery, and standing for 12h;
1.2 tightly attaching the 3 test batteries to each other, as shown in fig. 3, arranging a first temperature sensor 3 between the test batteries, arranging a second temperature sensor 4 on the side surface of the test battery, which is in contact with air, and controlling the thickness to be 1-10mm; the outer side surfaces (the side surface with the largest surface area) of the two outermost batteries are tightly attached to a thermal resistance layer 5, and the thermal resistance layer is made of high-thermal-resistance materials such as superfine glass wool, high-silicon cotton, vacuum insulation boards, aerogel, foam plastics, foam cotton, polyurethane and the like; the contact between the outer side surface of the battery and air is avoided, more specifically, the contact between the outer side surface of the battery and flue gas generated after thermal runaway of the battery is avoided, and the outer side surface is prevented from being heated by the flue gas;
1.3 overcharge testing of the cells with various powers ranging from 0.1P 0 ～10P 0 In which P is 0 Is the rated power of the battery;
1.4 recording the moment when the thermal runaway of the battery occurs, calculating the overcharged energy E:
E＝∫f(P 1 )dt
wherein, P 1 Is the power of overcharge, t is the time of overcharge;
1.5 when the power of the battery is reduced to a certain value, the battery can not generate thermal runaway, and the value represents the minimum power P of the battery in thermal runaway min ；
1.6, drawing a battery surface temperature-time curve in an overcharge experiment;
1.7, drawing a power-energy curve for charging the battery, wherein the curve represents a critical value of the battery for triggering thermal runaway under an overcharge condition, namely energy values corresponding to different powers required for triggering the thermal runaway of the battery, the upper part of the curve represents that the thermal runaway of the battery has occurred, and the lower part of the curve represents that the thermal runaway of the battery has not occurred.
2. Calculating the energy released after the battery overcharge thermal runaway trigger:
2.1 recording the temperature between the batteries on both sides of the overcharged battery during the operation of step 1.3, and drawing a surface temperature-time curve of the overcharged battery;
2.2 comparing the surface temperature-time curve of the battery in the step 1.6, finding out the surface temperature-time curve of the battery corresponding to the heating test close to the surface temperature-time curve, estimating the surface heating power of the overcharged battery, and calculating the surface heating energy Q of the overcharged battery according to the surface heating power 1 ：
Q 1 ＝∫f(P 2 )dt
The heating energy is the heating energy of the adjacent battery contact surface;
2.3 when the operation is carried out in the step 1.3, a temperature measuring device is arranged above the battery safety valve, a gas-liquid mixture is sprayed out in the thermal runaway process, and if the gas-liquid mixture is burnt after the gas-liquid mixture is sprayed out, the recorded temperature is the temperature of open fire;
2.4, drawing a temperature-time curve recorded by a temperature measuring device of the side surface of the adjacent battery, which is in contact with the air; finding out the surface temperature-time curve of the battery corresponding to the heating test close to the surface temperature-time curve, and estimating the heating power P of the smoke to the adjacent battery 3 I.e. the heating power of the contact side of the adjacent battery and the air (smoke), and calculating the heating energy Q according to the heating power 2 ：
Q 2 ＝∫f(P 3 )dt
This heating energy Q 2 The heating energy of the contact surface of the adjacent battery and the air;
2.5 taking into account the number of cells in the battery module or battery box into which the cells are grouped is denoted as n;
2.6 calculating the energy Q released after the battery overcharge thermal runaway is triggered:
the sum is the heating energy for the adjacent cell after thermal runaway of the overcharged cell.
3. Judging whether the battery has thermal runaway chain reaction
3.1 under a certain overcharge power, when the energy out of control caused by overcharge of the battery is more than or equal to the energy released by thermal out of control caused by overcharge of the battery, judging that the thermal out of control chain reaction can not occur in the battery under the overcharge power;
3.2 under a certain overcharge power, when the energy of the battery caused by the runaway by the overcharge is less than the energy released by the thermal runaway caused by the overcharge, judging that the battery can generate thermal runaway chain reaction under the overcharge power.
The invention also discloses a thermal runaway chain reaction judgment system of the energy storage battery pack, which comprises an overcharge energy calculation module for causing thermal runaway by overcharge of the battery, a release energy calculation module for causing thermal runaway by overcharge of the battery and a judgment module. The battery overcharge energy calculation module is used for calculating overcharge energy when the battery is out of control due to overcharge; the battery overcharge thermal runaway release energy calculation module is used for calculating the release energy of the battery after thermal runaway; and the judging module is used for judging whether the thermal runaway chain reaction occurs in the battery according to the overcharged energy and the released energy.
In order to realize the test method, the invention also provides a test device which comprises a test box, a temperature measuring device, a thermal resistance layer and an upper computer. The test box is internally provided with 3 batteries, and the top, two sides and the front-back distance between the batteries and the inner side of the box body of the test box are consistent with the distance between the batteries in the battery module and the box body of the battery module; the temperature measuring device comprises a first temperature sensor arranged between batteries, a second temperature sensor arranged on the side surface of the battery, which is in contact with air, and a third temperature sensor arranged above a safety valve of the battery, wherein the thicknesses of the first temperature sensor and the second temperature sensor are 1-10mm, and the third temperature sensor is used for recording the open flame temperature of a combustion gas-liquid mixture sprayed out in the thermal runaway process; the thermal resistance layer is arranged on the outer side surfaces of the two batteries on the outermost side; the upper computer is connected with the temperature measuring device, and the energy storage battery pack thermal runaway chain reaction judgment system is arranged in the upper computer.
The principle of the invention is as follows:
the cells can undergo a thermal runaway reaction under overcharge and overheating conditions, releasing a large amount of heat that heats adjacent cells, potentially triggering adjacent cells to also thermally runaway.
Whether a thermal runaway reaction chain reaction occurs or not is determined, and the key is to judge the magnitude relation between the power and the energy required for triggering the thermal runaway of the battery and the power and the energy of the heat released after the thermal runaway of the battery. If the thermal power and energy released by the battery after thermal runaway is greater than the power and energy required for triggering the thermal runaway of the battery, namely the energy released by the battery is greater than the energy absorbed by the battery, the thermal runaway can occur, otherwise, the thermal runaway cannot occur. The energy passively absorbed by the battery includes electric energy and heat energy, while the energy released after the thermal runaway of the battery is converted from the electric energy and the heat energy absorbed before the thermal runaway of the battery into the energy (chemical energy and reaction heat) generated by the thermal runaway side reaction in the battery, and there is no clear magnitude relationship between the two.
According to the thermal balance principle of heating and heat release of the battery, when the received energy exceeds the thermal runaway critical condition, the battery thermally runaway and releases energy, and when the energy released by the thermal runaway of the battery is greater than the received energy required for triggering the thermal runaway, a thermal runaway chain reaction occurs. According to the thought, a battery thermal runaway test is designed, so that the triggered power and energy, and the released power and energy can be quantitatively reflected;
in the testing process, two factors of direct heating of the adjacent batteries on the contact surface and indirect heating of the smoke on the side surfaces of the adjacent batteries are considered, so that the design is closer to the actual situation.
When the power and the energy of indirect flue gas heating of the adjacent side batteries are finally calculated, the difference between the actual battery module and the test battery is considered, the number of the batteries in the actual battery module is large, and the flue gas heating effect is dispersed, so that an n/3 treatment mode is introduced.
The invention also has the following advantages:
the invention determines the critical condition of the thermal runaway of the battery through overcharge tests with various powers, and determines the energy released in the whole process of the thermal runaway of the battery through the temperature change of adjacent batteries and smoke in the overcharge tests. According to the invention, whether the battery has a chain reaction or not is judged by comparing the power and the energy received by the battery with the power and the energy released by thermal runaway of the battery.
According to the method, the heating power judgment method of the temperature of the side battery in contact with the air is introduced, the heating path of the battery in the battery pack to the surrounding batteries after thermal runaway is comprehensively considered, on one hand, heat is transferred in a side contact mode, on the other hand, heat is transferred in a mode that smoke is in contact with the side, and the treatment is closer to the real condition.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A method for judging thermal runaway chain reaction of an energy storage battery pack is characterized by comprising the following steps:
the energy required by one battery thermal runaway in the battery pack triggered by overcharge is calculated by the following specific method:
step 1-1, fully charging the battery according to an operation instruction for battery delivery;
step 1-2, closely attaching 3 batteries to each other, and arranging a temperature measuring device with the thickness of 1-10mm between the batteries and on the side surface of the battery, which is in contact with air; the outer sides of the two batteries at the outermost side are tightly attached with a layer of high thermal resistance material;
step 1-3, carrying out overcharge test on the battery by adopting various powers, wherein the range of the power is from 0.1P 0 ～10P 0 In which P is 0 Is the rated power of the battery;
step 1-4, recording the moment when the thermal runaway of the battery occurs, and calculating the overcharged energy E:
E＝∫f(P 1 )dt
wherein, P 1 Is the power of the overcharge, t is the time of the overcharge;
step 1-5, when the battery power is reduced to a certain value, the battery can not generate thermal runaway, and the value is the minimum power P generated by the thermal runaway of the battery min ；
Step 1-6, drawing a battery surface temperature-time curve in an overcharge experiment;
step 1-7, drawing a power-energy curve for charging the battery, wherein the curve represents a critical value of the battery for triggering thermal runaway under an overcharge condition, the upper part of the curve represents that the thermal runaway of the battery occurs, and the lower part of the curve represents that the thermal runaway of the battery does not occur;
step 2: calculating the energy released after the battery is triggered by the overcharge thermal runaway;
and 3, step 3: judging whether the battery pack has thermal runaway chain reaction;
under a certain overcharge power, when the energy required by the battery for causing thermal runaway due to overcharge is more than or equal to the energy released after the battery is triggered by causing thermal runaway due to overcharge, the battery is under the overcharge power: thermal runaway chain reaction can not occur; otherwise, the battery at the overcharge power: a thermal runaway chain reaction can occur.
2. The method for judging the thermal runaway chain reaction of the energy storage battery pack according to claim 1, wherein in the step 2, a specific method for calculating the energy released after the battery overcharge thermal runaway trigger is as follows:
step 2-1, recording the temperature between the batteries at two sides of the overcharged battery when the step 1-3 is executed, and drawing a surface temperature-time curve of the overcharged battery;
step 2-2, comparing the battery surface temperature-time curves drawn in the step 1-6, searching the battery surface temperature-time curve corresponding to the closest heating test, and estimating the overcharged battery surface heating power P 2 And calculating the heat generation energy Q of the overcharged battery surface based on the calculated heat generation energy Q 1 ：
Q 1 ＝∫f(P 2 )dt
The heating energy is the heating energy of the contact surface of the adjacent battery;
step 2-3, drawing a temperature-time curve of the side face of the adjacent battery, which is in contact with the air; finding out the battery surface temperature-time curve corresponding to the closest heating test, and estimating the heating power P of the smoke to the adjacent battery 3 And calculating the heating energy Q based on the calculated values 2 ：
Q 2 ＝∫f(P 3 )dt
Said heating energy Q 2 The heating energy of the contact surface of the adjacent battery and the air;
step 2-4, calculating the energy Q released after the battery overcharging thermal runaway is triggered:
where n is the number of cells in a battery module or battery box in which the cells are grouped.
3. The method for judging the thermal runaway chain reaction of the energy storage battery pack according to claim 2, wherein the step 3 specifically comprises:
when E is more than or equal to Q, the battery does not generate thermal runaway chain reaction under the overcharge power;
when E is less than Q, thermal runaway chain reaction of the battery can occur under the overcharge power.
4. An energy storage battery pack thermal runaway chain reaction judgment system for realizing the method according to any one of claims 1 to 3, characterized by comprising:
the battery overcharge energy calculation module is used for calculating overcharge energy when the battery is out of control due to overcharge;
the battery overcharge thermal runaway release energy calculation module is used for calculating the release energy of the battery after thermal runaway;
and the judging module is used for judging whether the thermal runaway chain reaction occurs in the battery according to the overcharged energy and the released energy.
5. A test device for carrying out the method of any one of claims 1 to 3, comprising:
the testing box is internally provided with 3 batteries which comprise overcharged batteries and adjacent batteries arranged on two sides of the overcharged batteries; the top, two sides and the front-back spacing of the 3 batteries and the inner side of the box body of the test box are consistent with the distance between the battery in the battery module and the box body;
a temperature measuring device including a first temperature sensor disposed between the battery and the battery, and a second temperature sensor of a side of the battery that is in contact with air;
the thermal resistance layer is arranged on the outer side surfaces of the two outermost batteries;
the upper computer is connected with the temperature measuring device and internally provided with the thermal runaway chain reaction judgment system of the energy storage battery pack according to claim 4.
6. The testing apparatus according to claim 5, wherein a third temperature sensor is further provided above the safety valve of the battery for recording the open flame temperature of the combustion gas-liquid mixture ejected during thermal runaway.
7. The testing device according to claim 5 or 6, wherein the thickness of the first and second temperature sensors is 1 to 10mm.
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