CN112886082A - Power battery thermal runaway early warning method and device, electronic equipment and medium - Google Patents

Abstract

The invention relates to the field of power batteries, and in particular, provides a power battery thermal runaway warning method, device, electronic equipment and medium. The power battery thermal runaway early warning method includes the following steps: determining a power battery thermal runaway level according to battery voltage, battery temperature and battery expansion force; and performing power battery thermal runaway early warning according to the power battery thermal runaway level. On the basis of the traditional thermal runaway warning based on battery voltage and battery temperature, the present invention adds an important judgment basis of battery expansion force, and determines the thermal runaway level according to battery voltage, battery temperature and battery expansion force. According to the level, the corresponding thermal runaway warning is carried out. This method can effectively judge whether the power battery has thermal runaway, and give an alarm signal before the battery has obvious thermal runaway. .

Description

Power battery thermal runaway warning method, device, electronic device and medium

technical field

The invention relates to the field of power batteries, and in particular, to a method, device, electronic device and medium for early warning of thermal runaway of a power battery.

Background technique

In the past ten years, the domestic new energy vehicle industry has developed rapidly. In 2018 and 2019, China's new energy vehicle sales reached 1.256 million and 1.206 million respectively, ranking first in the world for four consecutive years. It is estimated that by 2025, my country's new energy vehicle sales will strive to account for 20% of the total vehicle sales. Therefore, as the core driving force for the transformation and upgrading of the automobile industry, new energy vehicles will be the key development direction in the next few decades.

However, in recent years, new energy vehicle fire accidents have continued to increase, and fire safety accidents of different vehicle types and application scenarios have continued to increase, which has become an important obstacle to the large-scale popularization and application of electric vehicles. Comprehensive analysis of various types of electric vehicle fire accidents and their potential causes have the following typical characteristics: (1) The accident models are diverse, covering passenger cars, electric buses, special vehicles and other types of vehicles; (2) Accidents and seasons (ambient temperature) shows a high correlation, and summer is a high accident season; (3) the source of the accident is highly correlated with the power battery, and the power battery is the core power source of electric vehicles, and many electric vehicle fire accidents are directly related to it; ( 4) The cause of the accident is ambiguous. Many accident clues disappear along with the fire. It is technically difficult to accurately locate the source of the accident.

By counting the state of electric vehicles when they catch fire and analyzing the possible causes of accidents, it can be seen that among all kinds of fire accidents of electric vehicles, the fire accidents caused by the thermal runaway of lithium-ion power batteries account for a large proportion. In this type of event, the occurrence process mainly includes three stages: "accumulation of thermal runaway causes of battery cells", "thermal runaway occurrence of battery cells" and "thermal runaway diffusion of battery systems". In order to improve the safety of the power battery system, the above three stages must be monitored and controlled step by step. One of the very important links is to provide accurate early warning when the thermal runaway of the battery occurs, and to give the occupants a clear signal to reserve enough time for the accident vehicle to be disposed of and the personnel to escape.

At present, the judgment methods used in the industry for battery thermal runaway warning are mainly based on temperature, voltage, gas, smoke, etc. For example, when the combination of temperature and voltage meets the following conditions, it can be determined that the battery has thermal runaway: voltage drop and temperature change Both the maximum temperature and the temperature change rate exceed their respective set values. In addition, it also includes that when the concentration of certain gases or smoke reaches a certain value, it can be determined that the battery has thermal runaway: when the battery system detects a significant change in gas components such as CO and H ₂ or a large amount of smoke is generated. However, when the battery reaches the above conditions, the battery has already experienced obvious thermal runaway, so it is necessary to develop more effective means to give an alarm signal before the battery has obvious thermal runaway.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a power battery thermal runaway early warning method, device, electronic device and medium, so as to achieve the effect of giving an alarm signal before the battery has obvious thermal runaway.

In order to realize the above-mentioned purpose of the present invention, the following technical solutions are specially adopted:

In a first aspect, the present invention provides a power battery thermal runaway warning method, comprising the following steps:

Determine the thermal runaway level of the power battery according to the battery voltage, battery temperature and battery expansion force;

According to the power battery thermal runaway level, a power battery thermal runaway warning is performed.

As a further preferred technical solution, the thermal runaway level of the power battery is determined according to the battery voltage, battery temperature and battery expansion force, including:

The thermal runaway level of the power battery is determined according to the change value of the battery voltage, the battery temperature, the rate of change of the battery temperature and the change value of the battery expansion force.

As a further preferred technical solution, the thermal runaway level of the power battery is determined according to the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value, including:

If at least two of the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value exceed their respective preset values, it is judged that the power battery is thermally out of control; and then the power battery is determined according to the condition category exceeding the preset value. Thermal runaway rating.

As a further preferred technical solution, the thermal runaway level of the power battery is determined according to the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value, including:

If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, and the change value of the battery voltage exceeds the initial battery voltage of the set ratio, the thermal runaway level of the power battery is determined to be Level 1;

If the battery expansion force change value exceeds the expansion force change value threshold, and the battery temperature exceeds the battery temperature threshold, it is determined that the thermal runaway level of the power battery is Level 2;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the thermal runaway level of the power battery is determined to be Level 3;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery voltage change value exceeds the set ratio of the initial battery voltage, the battery temperature change rate exceeds the temperature change rate threshold and the time exceeds the time threshold, the thermal runaway level of the power battery is determined as four;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature exceeds the battery temperature threshold, and the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the power battery thermal runaway level is determined to be level 5.

As a further preferred technical solution, the threshold value of the expansion force change is 1500-2500N.

As a further preferred technical solution, the set proportion of the initial battery voltage is 15%-25% of the battery initial voltage.

As a further preferred technical solution, the temperature change rate threshold is 1-5°C for 5s.

In a second aspect, the present invention provides a power battery thermal runaway warning device, comprising:

The power battery thermal runaway level determination module is used to determine the power battery thermal runaway level according to the battery voltage, battery temperature and battery expansion force;

The thermal runaway early warning module is used for early warning of the thermal runaway of the power battery according to the thermal runaway level of the power battery.

In a third aspect, the present invention provides an electronic device, comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

The memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method described above.

In a fourth aspect, the present invention provides a medium on which computer instructions are stored, and the computer instructions are used to cause the computer to execute the above method.

The beneficial effects of the present invention are:

The power battery thermal runaway early warning method provided by the present invention determines the power battery thermal runaway level according to the battery voltage, battery temperature and battery expansion force; and then performs power battery thermal runaway early warning according to the power battery thermal runaway level. The inventors of the present invention have found that when the battery is thermally out of control, gas will be generated inside the battery and the positive and negative electrodes will expand, resulting in an increase in the battery expansion force. When the battery expansion force is smaller than the square or cylindrical battery pressure relief The valve opening pressure and the rupture pressure of the aluminum-plastic film of the pouch battery are reflected in the continuous increase of the expansion force, and the change of this characteristic is usually earlier than the change of the battery voltage and battery temperature; in addition, because the expansion force acquisition is convenient, fast and accurate, and The acquisition of temperature is inconvenient and slower than the expansion force, and there is a certain hysteresis. Therefore, the change of the battery expansion force is first displayed in the early stage of thermal runaway. Therefore, the present invention combines battery voltage, battery temperature and battery expansion force, specifically according to four aspects of battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value, and combines these four aspects when thermal runaway actually occurs. According to the order of occurrence, emergency situation, severity of thermal runaway and accuracy of early warning, the five-level thermal runaway level is determined, and then corresponding thermal runaway early warning is carried out according to the level.

This method can effectively judge whether the power battery has thermal runaway, give an alarm signal before the battery has obvious thermal runaway, and can provide different early warnings for different thermal runaway levels, so that users can take corresponding response strategies according to different thermal runaway levels. .

Description of drawings

1 is a flowchart of a power battery thermal runaway warning method provided by an embodiment of the present invention;

Fig. 2 is a graph of temperature, voltage and expansion force in the overcharge and thermal runaway of a 25Ah square hard shell lithium iron phosphate 5 graphite battery of the present invention;

Fig. 3 is a graph showing the changes of temperature, voltage and expansion force during overcharge thermal runaway of a 37Ah square hard shell Ni _0.5 Co _0.2 Mn _0.3 ternary material 5 graphite battery of the present invention;

Fig. 4 is a graph showing the change of temperature, voltage and expansion force during heating thermal runaway of a 37Ah square hard shell Ni _0.5 Co _0.2 Mn _0.3 ternary material 5 graphite battery of the present invention;

5 is a schematic structural diagram of a power battery thermal runaway warning device provided by an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

Icons: 501-power battery thermal runaway level determination module; 502-thermal runaway warning module; 601-processor; 602-memory; 603-input device; 604-output device.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer.

FIG. 1 is a flowchart of a thermal runaway warning method for a power battery provided by this embodiment. This embodiment is suitable for thermal runaway warning of a power battery in a normal placement state, a charging state, and a discharging state. The method can be performed by a power battery thermal runaway warning device, which can be composed of software and hardware or generally integrated in electronic equipment.

As shown in FIG. 1 , this embodiment provides a power battery thermal runaway warning method, including the following steps:

S110. Determine the thermal runaway level of the power battery according to the battery voltage, the battery temperature, and the battery expansion force.

It should be noted:

The above-mentioned "cell voltage" refers to the difference between the positive electrode potential and the negative electrode potential of the battery. The battery voltage can be acquired by using a voltage sensor.

The above "battery temperature" refers to the temperature of the battery surface, including at least one of the battery positive electrode temperature, battery negative electrode temperature or battery case temperature, for example: battery positive electrode temperature, battery negative electrode temperature, battery case temperature, battery positive electrode temperature and battery negative temperature, battery negative temperature and battery case temperature, battery positive temperature and battery case temperature, or battery positive temperature, battery negative temperature and battery case temperature, preferably battery positive temperature, battery negative temperature and battery case temperature . When the battery temperature is two or more of the battery positive temperature, the battery negative temperature or the battery case temperature, the higher temperature value shall prevail. The battery temperature can be acquired by using a temperature sensor.

The above-mentioned "battery swelling force" refers to the pressure on the side of the battery module or the single battery case in the battery pack. The battery expansion force can be acquired by using a pressure sensor.

Optionally, according to the battery voltage, battery temperature and battery expansion force, determine the thermal runaway level of the power battery, including:

If the battery expansion force exceeds the expansion force threshold, the thermal runaway level of the power battery is determined to be Level 1;

If the battery voltage exceeds the battery voltage threshold, the thermal runaway level of the power battery is determined to be Level 2;

If the battery temperature exceeds the battery temperature threshold, the thermal runaway level of the power battery is determined to be level 3.

Optionally, the above expansion force threshold takes a corresponding value according to the state of the battery; the above battery voltage threshold takes a corresponding value according to the model and type of the battery; the above battery temperature threshold takes a corresponding value according to the maximum operating temperature specified by the battery manufacturer, For example, it is 75-85°C.

Only the battery temperature (ie, the current temperature of the battery) is considered in the above method of determining the thermal runaway of the power battery. In actual situations, if the battery temperature changes too quickly, there is also a risk of thermal runaway. Therefore, in a preferred embodiment, the determination of the thermal runaway level of the power battery according to the battery voltage, the battery temperature and the battery expansion force includes:

The thermal runaway level of the power battery is determined according to the change value of the battery voltage, the battery temperature, the rate of change of the battery temperature and the change value of the battery expansion force.

It should be noted:

The above-mentioned "battery voltage change value" refers to the difference between the current moment voltage of the battery and the voltage at the previous moment adjacent to the battery, and the battery voltage variation value is collected by a voltage sensor.

The above-mentioned "battery temperature change rate" refers to the instantaneous change rate of the battery surface temperature, including at least one of the battery positive temperature change rate, the battery negative temperature change rate or the battery case temperature change rate, for example: the battery positive temperature change rate, Battery negative temperature change rate, battery case temperature change rate, battery positive temperature change rate and battery negative temperature change rate, battery negative temperature change rate and battery case temperature change rate, battery positive temperature change rate and battery case temperature change rate , or the rate of change of the temperature of the positive electrode of the battery, the rate of change of the temperature of the negative electrode of the battery, and the rate of change of the temperature of the battery case. When the battery temperature change rate is two or more of the battery positive temperature change rate, the battery negative temperature change rate or the battery case temperature change rate, the higher temperature change rate value shall prevail. The battery temperature change rate can be acquired by using a temperature sensor.

The above-mentioned "change value of battery expansion force" refers to the difference between the current expansion force of the battery and the initial expansion force of the battery. The initial expansion force of the battery refers to the normal expansion force when the battery is in different states without abnormal conditions such as thermal runaway, and the different states include a normal placement state, a charging state, and a discharging state. The initial expansion force of the battery can take a corresponding value according to the type and type of the battery, and the initial expansion force usually increases gradually with the aging of the battery. Generally speaking, in the normal placement state, the change value of the battery expansion force due to changes in ambient temperature is 20-80N, and in the normal charging and discharging state, the battery expansion force change value is 100-1000N.

Optionally, determining the thermal runaway level of the power battery according to the battery voltage change value, the battery temperature, the battery temperature change rate and the battery expansion force change value, including:

If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, the thermal runaway level of the power battery is determined to be Level 1;

If the battery pressure change value exceeds the battery pressure change value threshold, it is determined that the thermal runaway level of the power battery is Level 2;

If the battery temperature exceeds the battery temperature threshold, or the battery temperature change rate exceeds the temperature change rate threshold, the power battery thermal runaway level is determined to be level three.

In fact, when thermal runaway occurs in the power battery, due to the uncertainty of the thermal runaway mode, usually not only one of the aspects exceeds the threshold, but also in order to further improve the accuracy of the judgment, in a preferred implementation of this embodiment. , determining the thermal runaway level of the power battery according to the battery voltage change value, the battery temperature, the battery temperature change rate and the battery expansion force change value, including:

If at least two of the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value exceed their respective preset values, it is judged that the power battery is thermally out of control; and then the power battery is determined according to the condition category exceeding the preset value. Thermal runaway rating.

It should be noted:

The above "at least two items" refers to at least two of the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value, for example: battery voltage change value and battery temperature, battery temperature change rate and battery expansion force Change value, battery temperature and battery temperature change rate, battery voltage change value, battery temperature and battery temperature change rate, battery temperature, battery temperature change rate and battery expansion force change value, or battery voltage change value, battery temperature, battery temperature change value rate and battery expansion force change value, etc.

The above "condition category" refers to the above battery voltage change value, battery temperature, battery temperature change rate or battery expansion force change value, which is obtained according to the actual situation exceeding the preset value.

Optionally, if at least two of the battery voltage change value, battery temperature, battery temperature change rate, and battery expansion force change value exceed their respective preset values, it is determined that the power battery is thermally out of control; Condition category, which determines the thermal runaway level of the power battery, including:

If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, and the change value of the battery voltage exceeds the initial battery voltage of the set ratio, the thermal runaway level of the power battery is determined to be Level 1;

If the battery expansion force change value exceeds the expansion force change value threshold, and the battery temperature exceeds the battery temperature threshold, it is determined that the thermal runaway level of the power battery is Level 2;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the thermal runaway level of the power battery is determined to be Level 3;

If the battery voltage change value exceeds the set proportion of the battery initial voltage, the battery temperature change rate exceeds the temperature change rate threshold and the time exceeds the time threshold, the power battery thermal runaway level is determined to be level four.

The thermal runaway level of the power battery determined according to the above conditions is more in line with the actual situation and the accuracy of the early warning is higher than the thermal runaway level determined by only one indicator. However, this optional method still has room for improvement in terms of reflecting the severity of thermal runaway and the accuracy of early warning. Therefore, in a preferred implementation of this embodiment, the change value of battery voltage, battery temperature, battery temperature change The rate and battery expansion force change value to determine the thermal runaway level of the power battery, including:

If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, and the change value of the battery voltage exceeds the initial battery voltage of the set ratio, the thermal runaway level of the power battery is determined to be Level 1;

If the battery expansion force change value exceeds the expansion force change value threshold, and the battery temperature exceeds the battery temperature threshold, it is determined that the thermal runaway level of the power battery is Level 2;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the thermal runaway level of the power battery is determined to be Level 3;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery voltage change value exceeds the set ratio of the initial battery voltage, the battery temperature change rate exceeds the temperature change rate threshold and the time exceeds the time threshold, the thermal runaway level of the power battery is determined as four;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature exceeds the battery temperature threshold, and the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the power battery thermal runaway level is determined to be level 5.

In this preferred embodiment, the severity of the actual power battery thermal runaway is fully considered, and a graded early warning is performed according to the severity, which significantly improves the accuracy and reliability of the early warning.

It should be noted:

The above "initial voltage" refers to the voltage when the battery is fully charged.

Preferably, the threshold value of the expansion force change value is 1500-2500N. The expansion force change threshold is typically but not limited to 1500N, 1600N, 1700N, 1800N, 1900N, 2000N, 2100N, 2200N, 2300N, 2400N or 2500N. Through extensive research by the inventors, it is found that when the threshold value of the change in expansion force is within the above range, it can indicate that the battery has a high risk of thermal runaway. If the threshold is too small, it is generally caused by the change of the normal expansion force inside the battery, which cannot fully explain the existence of thermal runaway; if the threshold is too large, it means that the battery has experienced obvious thermal runaway. Judgment will undoubtedly delay the time when the warning is issued, which is not good for timely warning.

Preferably, the initial battery voltage of the set ratio is 15%-25% of the initial battery voltage. The battery initial voltage of the set ratio is typically but not limited to 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25% of the battery initial voltage Voltage. When the initial battery voltage of the set ratio is within the above range, it means that the battery voltage changes greatly, and there is a great risk of thermal runaway; if the initial battery voltage of the above set ratio is too small, it may be caused by the normal operation of the battery. The voltage change cannot reflect the thermal runaway of the battery; if the initial battery voltage of the above set ratio is too large, it means that the battery has undergone a relatively obvious thermal runaway. At this time, relying on an excessively large value for judgment will undoubtedly delay the time for the warning to be issued. , which is not conducive to timely warning.

Preferably, the temperature change rate threshold is 1-5°C for 5s. The temperature change rate threshold is typically but not limited to 1°C for 5s, 2°C for 5s, 3°C for 5s, 4°C for 5s, or 5°C for 5s. When the temperature change rate threshold is within the above range, it means that the temperature of the battery changes rapidly, and there is a greater risk of thermal runaway; if the temperature change rate threshold above is too small, it is mainly due to the temperature change during the normal operation of the battery, which cannot be reflected. The battery is thermally out of control; if the above temperature change rate threshold is too large, it means that the battery has experienced a relatively obvious thermal runaway. At this time, relying on an excessively large threshold for judgment will undoubtedly delay the time for issuing the warning, which is not good for timely warning.

Optionally, the time threshold is 2.5-3.5s. The time threshold is typically but not limited to 2.5s, 2.6s, 2.7s, 2.8s, 2.9s, 3s, 3.1s, 3.2s, 3.3s, 3.4s or 3.5s.

S120 , according to the power battery thermal runaway level, perform a power battery thermal runaway warning.

The thermal runaway warning in this embodiment shows that the severity of thermal runaway gradually increases with the increase of the thermal runaway level. In actual early warning, different early warning methods can be adopted according to the different thermal runaway levels. The buzzer sound can be used to reflect the different levels of thermal runaway through different tones; if lights are used during early warning, the different light colors can be used to reflect the different levels of thermal runaway. The specific form of the warning is not particularly limited in this embodiment, and any one that can be implemented in the art may be used, such as sound warning, light warning, sound and light warning, or vibration warning.

The inventors of the present invention have carried out a systematic study on the thermal runaway of the power battery in the following manner, and have determined the importance of the battery expansion force in the thermal runaway of the battery.

1) Carry out the thermal runaway test of the power battery. In order to more realistically simulate the thermal runaway scenario of the battery in actual use, the methods used to trigger the thermal runaway of the battery include overcharge, external heating, etc.

2) Test the characteristic parameters of the battery in the process of thermal runaway, including battery temperature, voltage, and expansion force, where the battery temperature includes the temperature of the positive and negative pole pieces of the battery and the temperature of the shell, which are obtained by a temperature sensor. The voltage is the positive and negative terminal voltage of the battery, which is obtained by the voltage sensor. The expansion force of the battery is the expansion force of the side of the square hard case or soft pack battery, which is obtained by the pressure sensor. The pressure sensor in the battery system can obtain the overall expansion force of the battery module by arranging a pressure sensor in a single battery module, or The expansion force value of each cell is obtained by arranging it on the side of a single battery cell. Figures 2, 3, and 4 are respectively the test results of temperature, voltage and expansion force in the process of thermal runaway of batteries with different material systems under different triggering modes.

Taking a 25Ah square hard case lithium iron phosphate 5 graphite system lithium-ion battery and a 37Ah square hard case Ni _0.5 Co _0.2 Mn _0.3 ternary material 5 graphite system battery as examples, the thermal runaway test under overcharge conditions was carried out.

1. Experimental test

1) According to the product specification, test the discharge capacity of the power battery, and then fully charge the power battery.

2) Use 2C current rate to test the overcharge and thermal runaway of the battery cell, simulate the abuse of the BMS of the electric vehicle battery system in the scenarios of functional safety failure or voltage signal acquisition failure, and record the voltage, temperature and expansion of the battery cell force, the sampling frequency is 100Hz, and the battery changes are observed through the camera.

3) When the triggered battery has obvious thermal runaway characteristics (such as pressure relief valve release, smoke, fire or explosion), stop charging the battery. In this test, it was observed that after the battery was released from the pressure relief valve and started to smoke at the same time, the charging of the battery was stopped, and then the battery continued to smoke. Keep the data acquisition device working continuously until there is no more phenomenon, and the temperature of all temperature sensors tested is lower than 50 ℃ and stop recording data.

2. When the experiment is over, save the test data and process the experimental samples.

3. Data analysis

From the test data shown in Figure 2, it can be seen that after the start of the test, along with the slow rise of the battery voltage of the 25Ah square hard shell lithium iron phosphate 5 graphite system, the battery expansion force increases rapidly, and the change value of the expansion force within 150s It reached 1500N, and the battery temperature was only 27 °C at this time. At the moment when the pressure relief valve opens, the expansion force reaches its maximum value. After the pressure relief valve is opened, the expansion force of the battery is significantly reduced. Due to the continuous occurrence of various side reactions inside the battery, a large amount of gas and smoke are generated, and the expansion force is maintained at about 2800N. When the battery is completely disconnected, the temperature does not continue to rise, the voltage drops to zero, and the expansion force gradually disappears to zero.

By comparing the changes of the battery voltage, temperature, expansion force and other signals, it can be seen that the time when the expansion force starts to increase significantly is earlier than the temperature change. When the change value exceeds the expansion force change range corresponding to normal charge and discharge, this There is still 150s before the thermal runaway of the battery occurs, so the change value of the battery expansion force can be used to realize the alarm for the thermal runaway of the battery.

From the test data shown in Figure 3, it can be seen that after the start of the test, along with the slow rise of the battery voltage of the 37Ah square hard shell Ni _0.5 Co _0.2 Mn _0.3 ternary material 5 graphite system, the battery expansion force and temperature began to increase. , the expansion force change value reached 1500N within 650s, and the battery temperature was only 24℃. When the pressure relief valve is opened, the expansion force reaches the maximum value of 4958N. After that, after the pressure relief valve is opened, the expansion force of the battery gradually decreases. After a period of time, the expansion force drops to zero. This process is accompanied by a gradual decrease in the battery temperature.

By comparing the changes of the battery voltage, temperature, expansion force and other signals, it can be seen that, similar to the lithium iron phosphate 5 graphite material system battery, the time when the expansion force starts to increase significantly is earlier than the temperature change. When the change value exceeds the normal value In the range of expansion force change corresponding to charge and discharge, there is still 260s before the thermal runaway of the battery occurs. Therefore, the change value of the battery expansion force can also be used to realize an effective early warning of thermal runaway of the battery.

Taking a 37Ah square hard shell Ni _0.5 Co _0.2 Mn _0.3 ternary material 5 graphite system lithium-ion battery as an example, the thermal runaway test under heating conditions was carried out.

1. Experimental test

1) According to the product specification, test the discharge capacity of the power battery, and then fully charge the power battery.

2) Use the external heating method (using an electric heater to heat the battery, and the electric heater is powered by a programmable power supply) to conduct a heating thermal runaway test for the battery cell, and the heater power is set to 800W, simulating the electric vehicle battery system. The thermal diffusion scene caused by the self-heating runaway caused by the internal defects of some battery cells is recorded. The voltage, temperature and expansion force of the battery cells are recorded during the process. The sampling frequency is 100Hz, and the battery changes are observed through the camera.

3) When the triggered battery has obvious thermal runaway characteristics (such as pressure relief valve, smoke, fire or explosion), turn off the heating power. In this test, after the battery was observed to be decompressed by the pressure relief valve and smoke began to be emitted at the same time, the external power supply of the electric heater was stopped, and then the battery continued to emit smoke. Keep the data acquisition device working continuously until there is no more phenomenon, and the temperature of all temperature sensors tested is lower than 50 ℃ and stop recording data.

2. When the experiment is over, save the test data and process the experimental samples.

3. Data analysis

From the test data shown in Figure 4, it can be seen that after the start of the test, under the action of the external electric heater, along with the increase of the battery temperature of the ternary material 5 graphite system, the battery expansion force also increased rapidly, and the battery expansion force also increased rapidly during the test. After 400s, it increased at a faster rate, and after 510s, the change value of the expansion force exceeded 1500N, and the battery voltage was still changing at this time. At 602s, the battery voltage becomes 0V due to an internal short circuit.

By comparing the changes of the battery voltage, temperature, expansion force and other signals, it can be seen that the time when the expansion force starts to increase significantly is earlier than the voltage change. When the change value exceeds the expansion force change range corresponding to normal charge and discharge, this There is still 92s before the internal short circuit occurs in the battery, so the change value of the battery expansion force can be used to realize an earlier alarm for the thermal runaway of the battery.

FIG. 5 is a schematic structural diagram of a power battery thermal runaway early warning device provided in this embodiment. This embodiment is suitable for thermal runaway early warning of power batteries in a normal placement state, a charging state, and a discharging state. The apparatus may consist of software and 5 or hardware, and is typically integrated in electronic equipment.

As shown in FIG. 5 , this embodiment provides a power battery thermal runaway warning device, including:

The power battery thermal runaway level determination module 501 is configured to determine the power battery thermal runaway level according to the battery voltage, battery temperature and battery expansion force.

Preferably, the power battery thermal runaway level determination module 501 includes:

The battery expansion force change value comparison unit is used to compare the battery expansion force change value and the expansion force change value threshold;

The battery voltage change value comparison unit is used to compare the battery voltage change value with the battery initial voltage of the set ratio;

A battery temperature comparison unit for comparing battery temperature and battery temperature threshold;

The battery temperature change rate comparison unit is used to compare the battery temperature change rate and the temperature change rate threshold;

The thermal runaway level determination unit is configured to determine the thermal runaway level according to the comparison result of the comparison unit.

Preferably, determining the thermal runaway level of the power battery according to the battery voltage, battery temperature and battery expansion force includes:

If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, and the change value of the battery voltage exceeds the initial battery voltage of the set ratio, the thermal runaway level of the power battery is determined to be Level 1;

If the battery expansion force change value exceeds the expansion force change value threshold, and the battery temperature exceeds the battery temperature threshold, it is determined that the thermal runaway level of the power battery is Level 2;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the thermal runaway level of the power battery is determined to be Level 3;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery voltage change value exceeds the set ratio of the initial battery voltage, the battery temperature change rate exceeds the temperature change rate threshold and the time exceeds the time threshold, the thermal runaway level of the power battery is determined as four;

If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature exceeds the battery temperature threshold, and the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the power battery thermal runaway level is determined to be level 5.

Preferably, the threshold value of the change in expansion force is 1500-2500N.

Preferably, the initial battery voltage of the set ratio is 15%-25% of the initial battery voltage.

Preferably, the temperature change rate threshold is 1-5°C for 5s.

The thermal runaway early warning module 502 is configured to perform early warning of the thermal runaway of the power battery according to the thermal runaway level of the power battery.

The above-mentioned power battery thermal runaway early warning device is used to execute the power battery thermal runaway early warning method in the embodiment of the present invention, and at least has functional modules and beneficial effects corresponding to the above-mentioned power battery thermal runaway early warning method.

As shown in FIG. 6 , an embodiment of the present invention further provides an electronic device, including:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

The memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method described above. At least one processor in the electronic device is capable of executing the above method and thus has at least the same advantages as the above method.

Optionally, the electronic device further includes interfaces for connecting various components, including a high-speed interface and a low-speed interface. The various components are interconnected using different buses and may be mounted on a common motherboard or otherwise as desired. The processor may process instructions for execution within the electronic device, including storing in or on memory to display a GUI (Graphical User Interface) on an external input and output device, such as a display device coupled to the interface instruction for graphic information. In other embodiments, multiple processors and 5 or more buses may be used with multiple memories and multiple memories, if desired. Likewise, multiple electronic devices may be connected, each providing some of the necessary operations (eg, as a server array, a group of blade servers, or a multiprocessor system). A processor 601 is taken as an example in FIG. 6 .

As a computer-readable storage medium, the memory 602 can be used to store software programs, computer-executable programs, and modules, such as the program instruction 5 module corresponding to the power battery thermal runaway warning method in the embodiment of the present invention (for example, power battery thermal runaway). The power battery thermal runaway level determination module 501 and the thermal runaway warning module 502 in the early warning device). The processor 601 executes various functional applications and data processing of the device by running the software programs, instructions and modules stored in the memory 602 , that is, to implement the above-mentioned power battery thermal runaway warning method.

The memory 602 may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to the use of the terminal, and the like. Additionally, memory 602 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some instances, memory 602 may further include memory located remotely from processor 601, which may be connected to the device through a network. Examples of such networks include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

The electronic device may further include: an input device 603 and an output device 604 . The processor 601 , the memory 602 , the input device 603 and the output device 604 may be connected by a bus or in other ways, and the connection by a bus is taken as an example in FIG. 6 .

The input device 603 can receive input numerical or character information, and the output device 604 can include a display device, an auxiliary lighting device (eg, LED), and a tactile feedback device (eg, a vibration motor), and the like. The display device may include, but is not limited to, a liquid crystal display (LCD), a light emitting diode (LED) display, and a plasma display. In some implementations, the display device may be a touch screen.

An embodiment of the present invention further provides a medium, where computer instructions are stored on the medium, and the computer instructions are used to cause the computer to execute the above method. The computer instructions on the medium are used to cause a computer to perform the above-described method, and thus have at least the same advantages as the above-described method.

The medium in the present invention may adopt any combination of one or more computer-readable mediums. The medium may be a computer-readable signal medium or a computer-readable storage medium. The medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, or a combination of any of the above. More specific examples (non-exhaustive list) of media include: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read only memory (ROM), erasable Programmable read only memory (EPROM or flash memory), fiber optics, portable compact disk read only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. In this document, a medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signal in baseband or as part of a carrier wave with computer-readable program code embodied thereon. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the foregoing. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device .

The program code contained on the computer-readable medium can be transmitted by any suitable medium, including but not limited to wireless, wire, optical fiber cable, RF (Radio Frequency, radio frequency), etc., or any suitable combination of the above.

Computer program code for carrying out operations of the present invention may be written in one or more programming languages, including object-oriented programming languages—such as Java, Smalltalk, C++, but also conventional procedural languages, or a combination thereof. Programming Language - such as the "C" language or similar programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (eg, using an Internet service provider through Internet connection).

It should be understood that steps may be reordered, added or deleted using the various forms of flow shown above. For example, the steps described in the present application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in the present application can be achieved, no limitation is imposed herein.

Although specific embodiments of the present invention have been illustrated and described, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications as fall within the scope of this invention be included in the appended claims.

Claims (10)

1. a power battery thermal runaway warning method, is characterized in that, comprises the following steps: Determine the thermal runaway level of the power battery according to the battery voltage, battery temperature and battery expansion force; According to the power battery thermal runaway level, a power battery thermal runaway warning is performed. 2. The power battery thermal runaway early warning method according to claim 1, wherein the determining the power battery thermal runaway level according to the battery voltage, battery temperature and battery expansion force comprises: The thermal runaway level of the power battery is determined according to the change value of the battery voltage, the battery temperature, the rate of change of the battery temperature and the change value of the battery expansion force. 3 . The power battery thermal runaway warning method according to claim 2 , wherein, the power battery thermal runaway level is determined according to the battery voltage change value, the battery temperature, the battery temperature change rate and the battery expansion force change value, including: 4 . : If at least two of the battery voltage change value, battery temperature, battery temperature change rate and battery expansion force change value exceed their respective preset values, it is judged that the power battery is thermally out of control; and then the power battery is determined according to the condition category exceeding the preset value. Thermal runaway rating. 4. The power battery thermal runaway warning method according to claim 2 or 3, wherein the power battery thermal runaway level is determined according to the battery voltage change value, the battery temperature, the battery temperature change rate and the battery expansion force change value ,include: If the change value of the battery expansion force exceeds the threshold value of the expansion force change value, and the change value of the battery voltage exceeds the initial battery voltage of the set ratio, the thermal runaway level of the power battery is determined to be Level 1; If the battery expansion force change value exceeds the expansion force change value threshold, and the battery temperature exceeds the battery temperature threshold, it is determined that the thermal runaway level of the power battery is Level 2; If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the thermal runaway level of the power battery is determined to be Level 3; If the battery expansion force change value exceeds the expansion force change value threshold, the battery voltage change value exceeds the set proportion of the battery initial voltage, the battery temperature change rate exceeds the temperature change rate threshold and the time exceeds the time threshold, the thermal runaway level of the power battery is determined as four; If the battery expansion force change value exceeds the expansion force change value threshold, the battery temperature exceeds the battery temperature threshold, and the battery temperature change rate exceeds the temperature change rate threshold and the exceeding time exceeds the time threshold, the power battery thermal runaway level is determined to be level 5. 5 . The thermal runaway warning method for a power battery according to claim 4 , wherein the threshold value of the expansion force change value is 1500-2500N. 6 . 6 . The power battery thermal runaway warning method according to claim 5 , wherein the battery initial voltage of the set ratio is 15%-25% of the battery initial voltage. 7 . 7 . The power battery thermal runaway warning method according to claim 5 or 6 , wherein the temperature change rate threshold is 1-5° C. for 5 s. 8 . 8. A power battery thermal runaway warning device, characterized in that, comprising: The power battery thermal runaway level determination module is used to determine the power battery thermal runaway level according to the battery voltage, battery temperature and battery expansion force; The thermal runaway early warning module is used for early warning of the thermal runaway of the power battery according to the thermal runaway level of the power battery. 9. An electronic device, characterized in that, comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the process of any one of claims 1-7 method. 10. A medium, wherein computer instructions are stored on the medium, and the computer instructions are used to cause the computer to execute the method of any one of claims 1-7.

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