A method and system for calculating the value of a battery abnormal temperature rise monitoring rate

Abstract

The application discloses a kind of battery abnormal temperature rise monitoring rate value calculation method and system, comprising: battery monomer is carried out battery thermal runaway test by overcharge, obtains battery surface temperature and battery voltage value;Draw the battery temperature, voltage and time relationship curve of battery overcharge thermal runaway whole process;According to the relationship curve of battery temperature, voltage and time determines thermal runaway time;In the range of calculation interval time, take multiple values, and draw multiple battery temperature rise and time relationship curve;Determine that the inflection point before battery thermal runaway time is on the battery temperature rise and time relationship curve of straight line y=2T error On, battery abnormal temperature rise monitoring rate value is the ratio of the temperature rise value corresponding to inflection point and the calculation interval time corresponding to inflection point.The method proposed in the application can make early warning in the early stage of temperature rise anomaly (not reaching thermal runaway), improve the timeliness of temperature monitoring.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of energy storage batteries, in particular to the technical field of thermal management of energy storage batteries, and specifically relates to a calculation method and system for monitoring the abnormal temperature rise rate of a battery. BACKGROUND

[0002] Lithium-ion energy storage batteries generate heat during normal charging and discharging, causing the temperature to rise, resulting in overheating of the battery, rapid capacity decline of the battery, and reduced service life of the battery. In abnormal situations, the battery may undergo thermal runaway reactions, generating more heat and a greater temperature rise rate, which not only adversely affects the battery itself but also affects other batteries, causing the spread of thermal runaway and expanding the scope of the safety accident.

[0003] Therefore, it is necessary to monitor the temperature of lithium-ion energy storage batteries in real time. When the temperature of the battery exceeds the pre-set value, the battery management system will initiate appropriate protective actions to prevent the temperature of the battery from rising further. From the current engineering application, it is not enough to only monitor the temperature of the battery. It is also necessary to detect the temperature rise rate of the battery, the concentration of various gas components in the environment of the battery module, and the like. Therefore, many battery thermal runaway early warning technologies and monitoring schemes for multiple state quantities have emerged.

[0004] However, the abnormal state of the battery is still most directly related to the change in the surface temperature of the battery, and the core quantity of battery state monitoring is still the temperature and temperature rise rate of the battery.

[0005] Patent CN201310729273 proposes a battery adiabatic temperature rise rate test method, including judging the adiabatic environment of the battery thermal runaway, selecting the initial state of charge of the battery, and testing the termination condition. This patent truly reflects the adiabatic temperature rise of the battery during full discharge and avoids the explosion of the battery due to thermal runaway. However, the method proposed in this patent cannot be used in the actual working environment of the battery.

[0006] Patent CN201910364952 proposes a battery thermal runaway detection method and device, including obtaining voltage detection data of multiple voltage detection points in the battery and multiple temperature detection data of multiple temperature detection points in the battery; calculating the temperature rise rate of the battery according to the multiple temperature detection data; and determining whether the battery has thermal runaway according to the multiple voltage detection data, the multiple temperature detection data, and the temperature rise rate.

[0007] Patent CN201911251125 proposes a temperature threshold determination method for thermal runaway early warning, which mainly tests the self-generated heat starting temperature under the current health state of the power battery and the maximum temperature that may occur under non-self-generated heat conditions, and makes a further judgment by comparing the two temperatures.

[0008] Patent CN202010249516 proposes a method and detection system for determining the thermal runaway boundary condition of lithium ion battery, including: charging the lithium ion battery to be tested; performing a thermal runaway experiment on the charged lithium ion battery and monitoring the temperature and voltage of the lithium ion battery during the thermal runaway experiment; determining the boundary condition of the thermal runaway of the lithium ion battery according to the obtained temperature and voltage.

[0009] Patent CN202110217156 proposes a method for determining battery thermal runaway, by obtaining the actual detection value of the temperature parameter of the target battery module in the target battery module at the associated sampling point, if the actual detection value of the temperature parameter meets the preset thermal runaway condition, it is determined that the target battery module has thermal runaway.

[0010] Patent CN202111659286 proposes a test method for lithium ion battery thermal runaway temperature, including placing the lithium ion battery at a starting temperature, and heating at a first heating rate until the self-heat rate of the lithium ion battery is >1℃ / min, obtaining a rough thermal runaway temperature T; then placing the lithium ion battery in another temperature range, and heating at a second heating rate until the self-heat rate of the lithium ion battery is >1℃ / min, obtaining the thermal runaway temperature.

[0011] The above patent technologies are about the detection and judgment method of battery thermal runaway temperature and temperature rise, but there are two common problems, namely: ①No consideration of the influence of temperature sampling error in battery engineering application, the error of temperature sampling point in the current energy storage application field is generally ≤1℃(environmental temperature-20~65℃), such error level makes the threshold value of temperature detection and the value of battery self-heat rate proposed by the above patent technologies difficult to apply to thermal runaway monitoring in actual energy storage engineering, because the data "fluctuation" caused by temperature sampling error is enough to cover the real temperature change of the battery, in another aspect, according to the threshold value set by the above patent to monitor the actual temperature of the engineering, frequent alarm but no thermal runaway will occur, which is also the false alarm phenomenon often occurred in current energy storage engineering. ②Although the above patent technologies propose temperature rate monitoring, they do not explicitly propose temperature rise rate calculation and value scheme, in fact, different sampling intervals and calculation methods will result in a large difference in temperature rise rate value, which will significantly affect the accurate judgment of whether the battery is in abnormal state. SUMMARY

[0012] To overcome the problems in the prior art, the purpose of the present application is to provide a battery abnormal temperature rise monitoring rate value calculation method and system, which fully considers the influence of temperature sampling error and distinguishes the calculation differences caused by different sampling intervals. The early warning monitoring threshold of the battery temperature rise rate calculated by the method of the present application can exclude the influence of sampling error and make early warning in the early stage of abnormal temperature rise (without reaching thermal runaway), thereby improving the timeliness of temperature monitoring.

[0013] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0014] A battery abnormal temperature rise monitoring rate value calculation method, comprising the following steps:

[0015] Performing a battery thermal runaway test by overcharging a battery monomer to obtain the battery surface temperature and the battery voltage value;

[0016] Drawing a battery temperature, voltage and time relationship curve of the whole process of battery overcharging leading to thermal runaway; determining the thermal runaway time according to the battery temperature, voltage and time relationship curve;

[0017] Taking multiple values within the calculation interval time range and drawing multiple battery temperature rise and time relationship curves;

[0018] Determining the battery temperature rise and time relationship curve that meets the inflection point before the battery thermal runaway time on the straight line y=2T error , the calculation interval time corresponding to the inflection point is t cross , and the temperature rise value corresponding to the inflection point is T △-cross , then the battery abnormal temperature rise monitoring rate value is T △-cross / t cross ; wherein T error is the error of the set temperature sampling point.

[0019] Further, the battery thermal runaway test by overcharging is performed at 0.5C-5C rate.

[0020] Further, the period for obtaining the battery surface temperature and the battery voltage value is 1s.

[0021] Further, the value range of the calculation interval time is [1s, 60s].

[0022] Further, the time axis of the battery temperature rise and time relationship curve and the time axis of the temperature and time relationship curve are consistent.

[0023] Further, the battery temperature rise is determined by the following process: the difference between the battery temperature at the current calculation time and the battery temperature at the last calculation time, and the interval between the current calculation time and the last calculation time is the calculation interval time.

[0024] Further, the error T of the set temperature sampling point is set error in the range of [0.5℃, 2℃].

[0025] Further, the inflection point before the thermal runaway of the battery is determined by the following process: the maximum curvature point of the corresponding temperature rise and time curve from the initial moment of overcharging of the battery to the moment when the battery reaches the highest temperature is the inflection point.

[0026] A calculation system for the value of the abnormal temperature rise monitoring rate of a battery, comprising:

[0027] A battery surface temperature and battery voltage value acquisition module for performing an overcharging to thermal runaway test on a battery monomer to obtain the battery surface temperature and battery voltage value;

[0028] A battery temperature, voltage and time relationship curve drawing module for drawing a battery temperature, voltage and time relationship curve of the whole process of overcharging to thermal runaway of the battery; and determining the thermal runaway time according to the battery temperature, voltage and time relationship curve;

[0029] A battery temperature rise and time relationship curve drawing module for taking multiple values within a calculation interval time range and drawing multiple battery temperature rise and time relationship curves;

[0030] A battery abnormal temperature rise monitoring rate value calculation module for determining that the inflection point before the thermal runaway time of the battery is on the battery temperature rise and time relationship curve on the straight line y=2T error , the calculation interval time corresponding to the inflection point is t cross , and the temperature rise value corresponding to the inflection point is T △-cross , then the battery abnormal temperature rise monitoring rate value is T △-cross / t cross ; wherein T error is the error of the set temperature sampling point.

[0031] Compared with the prior art, the present application has the beneficial effects of:

[0032] The present application can distinguish the calculation difference caused by different sampling intervals, and does not reduce the sensitivity due to long interval time, and not only can effectively eliminate the interference of sampling error, but also can give an early warning, which is more time-efficient than the monitoring and early warning of the interval time of s level, and fully considers the influence of temperature sampling error, can eliminate the influence of sampling error, and eliminate the battery monitoring without alarm caused by sampling error. The method proposed in the present application can give an early warning in the early stage of abnormal temperature rise (not reaching thermal runaway), and improves the timeliness of temperature monitoring.

[0033] Furthermore, since the calculated temperature rise rate values ​​differ greatly due to the use of different sampling intervals, the present invention, by reasonably determining the battery thermal runaway temperature rise rate value for battery state monitoring, is of great significance for ensuring battery safety and avoiding thermal runaway. Attached Figure Description

[0034] Figure 1 This is a curve showing the relationship between battery temperature, voltage, and time in this invention;

[0035] Figure 2 This is the curve showing the relationship between battery temperature rise and time in this invention.

[0036] Figure 3 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings.

[0038] The present invention provides a method for calculating the abnormal temperature rise monitoring rate of a battery, comprising the following steps:

[0039] 1) Define the acquisition error of the temperature sampling point as ≤ the set error T of the temperature sampling point. error The battery surface temperature value is T. true That is, the temperature value T collected by the temperature sampling point is in the range [T true -T error T true +T error Fluctuations between [0, 0, 0]. The error T of the set temperature sampling point. error The value ranges from [0.5℃ to 2℃].

[0040] 2) For individual battery cells, conduct overcharge-induced thermal runaway tests at rates of 0.5C-5C. Set the acquisition period to 1s and collect and record the battery surface temperature and battery voltage values, i.e., record the battery surface temperature and battery voltage every 1s.

[0041] 3) Plot the relationship curves between battery temperature, voltage, and time throughout the entire process of thermal runaway caused by overcharging. Determine the thermal runaway time based on the relationship curves.

[0042] 4) Define the calculation interval for battery temperature rise as t, where t ranges from [1s to 60s]. That is, extract the time and corresponding temperature data required for calculating temperature rise from the battery surface temperature and battery voltage data collected in step 2) with t as the time interval.

[0043] 5) Define the battery temperature rise value T △ Let T be the battery temperature at the current calculation moment. present Compared to the battery temperature T at the previous calculation time previousThe difference, i.e., T △ =T present -T previous The interval between the current calculation time and the previous calculation time is t. The battery temperature rise rate at the current calculation time is T. △ / t.

[0044] 6) Plot the battery temperature rise versus time curves calculated at intervals t = 1s and 60s (i.e., battery temperature rise vs. time curves). The time axis of this curve should be consistent with the time axis of the temperature versus time curve in step 3).

[0045] 7) Define the inflection point: The point corresponding to the maximum curvature of the temperature rise vs. time curve during the process from the start of overcharging to the moment when the battery reaches its highest temperature is the inflection point of the battery temperature rise.

[0046] 8) Based on the definitions in steps 1) and 5), the maximum error in the calculated battery temperature rise can reach 2T. error ;

[0047] T △ =T present -T previous

[0048] T present -T previous ≤(T present-true +T error )-(T previous-true -T error )

[0049] (T present-true +T error )-(T previous-true -T error )=(T present-true -T previous-true )+2T error =T △-ture +2T error ,

[0050] That is, T △ -T △-ture ≤2T error

[0051] Among them, T present-true The actual temperature value at the current calculation time; T previous-true The actual temperature value at the previous calculation time; T △-ture This represents the actual temperature rise from the previous calculation time to the current calculation time.

[0052] 8) In the curve drawn in step 6), based on the error in step 7), draw a straight line equal to twice the sampling error, i.e., y = 2T.error a straight line.

[0053] 9) Adjust the value of the calculation interval time t, draw the battery temperature rise vs. time curve corresponding to the calculation interval time t, which should be drawn in the two curves of t = 1 s, 60 s, when the value of t is taken as a certain value, the corresponding temperature rise and time relationship curve (i.e. temperature rise vs. time curve) at the inflection point before the battery thermal runaway and y = 2T error , then define the calculation interval time corresponding to the curve as t cross , the temperature rise value at the inflection point is T △-cross .

[0054] 10) Thus, under the condition that the collection error of the temperature sampling point is ≤T error , the calculation interval time t of the battery thermal runaway temperature rise should be ≥t cross , and the value of the battery abnormal temperature rise monitoring rate should be T △-cross / t cross .

[0055] If the battery abnormal temperature rise monitoring rate exceeds T △-cross / t cross , take appropriate measures such as power off, reduce power operation, strengthen heat dissipation or issue a warning.

[0056] Figure 1 is the battery voltage, battery surface temperature vs. time curve of a certain type of lithium ion battery under overcharge condition from the initial overcharge time to the whole process of battery thermal runaway. From the curve, it can be seen that after overcharging for 55 min, the battery surface temperature rises to about 100℃, at which time the battery pressure relief valve breaks, then the battery voltage rises rapidly, and the battery temperature also rises, until about 70 min when the battery occurs internal short circuit, the voltage drops to 0V, at which time the battery occurs thermal runaway, and the temperature rises from 200℃ to about 500℃.

[0057] Figure 2 is the temperature rise vs. time curve calculated by selecting different calculation interval times, from bottom to top are the temperature rise vs. time curves corresponding to the time sampling interval of 1 s, 10 s, 30 s, 60 s.

[0058] For the case where the sampling error is less than or equal to 1℃, from Figure 2It can be seen that the thermal runaway inflection point of the temperature rise vs. time curve calculated by 1s sampling interval and 10s sampling interval is below 2℃, which means that the thermal runaway critical temperature rise calculated by 1s sampling interval and 10s sampling interval will be masked by the temperature fluctuation caused by sampling error, that is, effective thermal runaway temperature rise monitoring cannot be achieved. If the thermal runaway temperature rise inflection point rate calculated by the two sampling intervals is monitored, when the alarm is given, the battery thermal runaway has already occurred, and it cannot play a role in early warning. Especially for 10s sampling interval, it is more difficult to reflect the temperature change corresponding to the battery pressure relief valve breakage.

[0059] For the temperature rise vs. time curve with a sampling interval of 30s, it can be seen from the figure that the thermal runaway temperature rise inflection point of the curve coincides with 2Terror(2℃), and at about 55min, it reflects the temperature change corresponding to the battery pressure relief valve breakage in advance.

[0060] For the temperature rise vs. time curve with a sampling interval of 60s, it can be seen from the figure that the thermal runaway temperature rise inflection point of the curve is above 2℃, and the time corresponding to the inflection point is significantly earlier than the temperature time of thermal runaway, and at about 50min, it reflects the temperature change corresponding to the battery pressure relief valve breakage in advance.

[0061] Therefore, for the monitoring of the thermal runaway temperature rise rate of a certain type of lithium ion battery, the temperature rise rate should be calculated with a temperature calculation sampling interval of at least 30s, and the specific value is recommended to be 2℃ / 30s.

[0062] Especially need to point out that in the above examples, although the calculation interval is 30s, the sensitivity is not reduced due to the long interval time, on the contrary, the effect not only effectively eliminates the interference of sampling error, but also can give an early warning, which is more time-efficient than the s-level monitoring and warning of the interval time. Moreover, from the 1s calculation time interval, the effect is actually not good, because of the sampling problem, the temperature rise curve has many burrs and random points, which makes it difficult to be used for temperature rise monitoring.

[0063] Referring to Figure 3 A battery abnormal temperature rise monitoring rate value calculation system, comprising:

[0064] A battery surface temperature and battery voltage value acquisition module 1 for performing a battery thermal runaway test by overcharging a battery monomer to obtain a battery surface temperature and a battery voltage value;

[0065] A battery temperature, voltage and time relationship curve drawing module 2 for drawing a battery temperature, voltage and time relationship curve of the whole process of battery overcharging leading to thermal runaway; determining the thermal runaway time according to the battery temperature, voltage and time relationship curve;

[0066] The battery temperature rise-time curve drawing module 3 is configured to take multiple values in the range of the calculation interval time and draw multiple battery temperature rise-time curves.

[0067] The battery abnormal temperature rise monitoring rate value calculation module 4 is configured to determine that the battery temperature rise-time curve before the inflection point of the battery thermal runaway time is on the straight line y=2T error , the calculation interval time corresponding to the inflection point is t cross , and the temperature rise value corresponding to the inflection point is T △-cross , and the battery abnormal temperature rise monitoring rate value is T △-cross / t cross ; wherein T error is the error of the set temperature sampling point.

Claims

1. A method for calculating the value of the battery abnormal temperature rise monitoring rate, characterized in that, The method comprises the following steps: a battery monomer is subjected to overcharge to cause battery thermal runaway test, and battery surface temperature and battery voltage value are obtained; a battery temperature, voltage and time relationship curve of the whole process of battery overcharge to cause thermal runaway is drawn; and thermal runaway time is determined according to the battery temperature, voltage and time relationship curve; a plurality of values in the range of the calculation interval time are taken, and a plurality of battery temperature rise and time relationship curves are drawn; Adjust the value of the calculation interval time t, draw the battery temperature rise-time curve corresponding to the calculation interval time t, when the value of t is a certain value, the corresponding temperature rise-time curve has an inflection point before the battery thermal runaway, and the inflection point intersects with the straight line y=2T error , and the calculation interval time corresponding to the curve is defined as t cross , the temperature rise value at the inflection point is T △-cross , and y=2T error is a straight line with a 2-fold sampling error; Under the condition that the collection error of the temperature sampling point is less than or equal to T error , the calculation interval time t of the battery thermal runaway temperature rise is greater than or equal to t cross , and the abnormal temperature rise monitoring rate of the battery is T △-cross / t cross .

2. The method of claim 1, wherein the method comprises: the overcharge to cause battery thermal runaway test is carried out at 0.5C-5C rate.

3. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, The period for obtaining the battery surface temperature and the battery voltage value is 1s.

4. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, The value range of the calculation interval time is [1s, 60s].

5. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, The time axis of the battery temperature rise and time relationship curve and the time axis of the temperature and time relationship curve are consistent.

6. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, The battery temperature rise is determined by the following process: the difference between the battery temperature at the current calculation time and the battery temperature at the last calculation time, and the interval between the current calculation time and the last calculation time is the calculation interval time.

7. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, Error T of the set temperature sampling point error is in the range [0.5°C, 2°C].

8. The method for calculating the abnormal temperature rise monitoring rate of a battery according to claim 1, characterized in that, The inflection point before the battery thermal runaway is determined by the following process: from the battery overcharge starting time to the time when the battery reaches the highest temperature, the point corresponding to the maximum curvature value of the temperature rise and time relationship curve is the inflection point.

9. A system for calculating battery abnormal temperature rise monitoring rate values, comprising: The method comprises the following steps: a battery surface temperature and battery voltage value obtaining module is configured to subject a battery monomer to overcharge to cause battery thermal runaway test, and obtain battery surface temperature and battery voltage value; a battery temperature, voltage and time relationship curve drawing module is configured to draw a battery temperature, voltage and time relationship curve of the whole process of battery overcharge to cause thermal runaway; and determine thermal runaway time according to the battery temperature, voltage and time relationship curve; a battery temperature rise and time relationship curve drawing module is configured to take a plurality of values in the range of the calculation interval time, and draw a plurality of battery temperature rise and time relationship curves. The battery abnormal temperature rise monitoring rate value calculation module is configured to adjust the value of the calculation interval time t, draw a curve of the battery temperature rise corresponding to the calculation interval time t and time, and when the value of t is a certain value, the curve of the temperature rise corresponding to the calculation interval time t and time has an inflection point before the thermal runaway of the battery and a straight line y=2T error , and the calculation interval time corresponding to the curve is defined as t cross , the temperature rise value at the inflection point is T △-cross , and y=2T error is a straight line with a 2 times sampling error. Under the condition that the collection error of the temperature sampling point is less than or equal to T error , the calculation interval time t of the battery thermal runaway temperature rise is greater than or equal to t cross , and the abnormal temperature rise monitoring rate of the battery is T △-cross / t cross .

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