Power battery thermal runaway monitoring and alarming method

Abstract

The invention relates to the technical field of new energy automobiles, and discloses a power battery thermal runaway monitoring and alarming method, which comprises the following steps: acquiring a battery pressure value in real time, and entering a mode 1 when in a low power consumption mode; entering a mode 2 when in a high power consumption mode; mode 1, the whole vehicle and the BMS system are in a dormant state, a pressure slope value is calculated through a pressure sensor, when the pressure slope value is larger than or equal to a threshold value and continuous N cycles reach a set condition, the BMS is awakened, fault information and battery pack information are received and judged, and when thermal runaway is detected, reporting is carried out; and mode 2, the pressure value is only transmitted to the BMS, the BMS calculates the pressure slope value of the BMS, and when the pressure slope value is larger than or equal to a threshold value and N continuous periods reach set conditions respectively, the BMS receives and judges the fault information and the battery pack information and then reports the thermal runaway fault. According to the method, the thermal runaway signal can be accurately reported on the premise of not adding extra equipment, and the thermal runaway alarm time can be greatly shortened on the premise that false alarm is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a method for monitoring and alarming thermal runaway of a power battery. Background Art

[0002] With the rapid development of electric vehicles and energy storage systems, the safety of power batteries has become the focus of industry attention. Thermal runaway is one of the most serious safety issues of power batteries. Its characteristic is that the temperature inside the battery rises sharply, accompanied by a large amount of gas generation, which may cause the battery to catch fire or explode, causing safety accidents. Therefore, it is necessary to detect thermal runaway in a timely and accurate manner and trigger an alarm to reduce the accident rate and improve the safety of power batteries.

[0003] At present, the detection and alarm of thermal runaway of power batteries mainly rely on the combined detection of sensor signals (such as temperature, voltage, air pressure, etc.). When these parameters reach the preset threshold, the system will trigger an alarm. However, for battery types with slower gas production rates, such as lithium iron phosphate batteries, due to the relatively mild changes in their temperature, voltage and air pressure, traditional single parameter detection methods often have difficulty in capturing early signs of thermal runaway in a timely manner, resulting in delayed or missed alarms.

[0004] In order to solve this problem, the prior art proposes an alarm method based on a pressure sensor, which includes two solutions:

[0005] 1. Pressure increment detection, by comparing the current pressure value with the pressure value in a set time period, such as 2 minutes ago, if the increment exceeds the set threshold and lasts for a certain period, such as 3 periods, an alarm is triggered.

[0006] 2. Pressure slope detection, by calculating the pressure change rate per unit time, that is, the slope. If the slope exceeds the set threshold and continues for a certain period, such as 2 periods, an alarm is triggered.

[0007] Although the above schemes have improved the sensitivity of thermal runaway detection to a certain extent, there are still some problems in practical applications, especially in battery types with slow gas production rates such as lithium iron phosphate batteries. Due to the slow gas production rate and small gas production of lithium iron phosphate batteries, the pressure signal changes relatively gently when the pressure sensor is used for detection. It takes a long time to accumulate to reach the pressure increment threshold, which greatly prolongs the alarm time. At the same time, its slowly changing pressure signal is also difficult to meet the threshold requirements of slope detection, making it difficult for the system to achieve timely and rapid prediction. However, if the increment or slope threshold is lowered in order to shorten the alarm time, the pressure signal will fluctuate due to external environmental interference when facing special working conditions (such as vehicles passing through tunnels, wading, downhill, etc.), thereby increasing the risk of false alarms. Therefore, how to achieve fast and reliable thermal runaway warning while ensuring the accuracy of the alarm is still a key problem that current technology needs to solve. Summary of the invention

[0008] The present invention aims to provide a power battery thermal runaway monitoring and alarm method to solve the problem that the existing battery thermal runaway monitoring cycle is long and prone to false alarm risks.

[0009] To achieve the above object, the present invention adopts the following technical scheme: a power battery thermal runaway monitoring and alarm method, comprising: using a pressure sensor to periodically obtain a battery pressure value in real time, determining the current power consumption mode of the pressure sensor, and entering mode 1 when the pressure sensor is in a low power consumption mode; entering mode 2 when the pressure sensor is in a high power consumption mode;

[0010] Method 1: put the vehicle and BMS system in dormant state, calculate the battery pack pressure slope value through the pressure sensor, and wake up the BMS system when the pressure slope value is ≥ the threshold value and reaches the set conditions for N consecutive cycles, receive and judge the fault information and battery pack information, and report when thermal runaway is detected;

[0011] Method 2: The monitored pressure value is transmitted only to the BMS system. The BMS system calculates the pressure slope value based on the pressure value. When the pressure slope value ≥ the threshold value and meets the set conditions for N consecutive cycles, the BMS receives and judges the battery pack information and reports a thermal runaway fault; where N ≥ 1.

[0012] The principles and advantages of this solution are:

[0013] In traditional battery thermal runaway detection methods, thermal runaway judgment is usually based on a single signal, such as temperature or voltage, but these signals may not change significantly in the early stages of thermal runaway, resulting in insufficient detection sensitivity. Therefore, in order to improve the accuracy and reliability of detection, it is necessary to introduce more dimensional signals, such as gas concentration, smoke concentration, etc., and these signals require additional hardware equipment to collect.

[0014] Especially when facing battery types like lithium iron phosphate lithium-ion batteries with slow gas production rates and low gas production, the abnormal reactions inside the battery are even weaker. Whether it is the pressure increment judgment method or the slope value judgment method within the unit cycle, relying solely on the existing BMS sensor to directly capture internal changes will result in a long time accumulation period or a small change that is not enough to be judged as abnormal. Based on this, we have also considered adding peripherals to assist in the detection of such batteries, such as using smoke sensors to alarm lithium iron phosphate batteries. Although this method can reduce the thermal runaway warning time, it has a major problem, that is, the battery pack may not be clean enough, or the parts may be worn to produce particulate impurities, causing the smoke sensor to sense the particulate matter and send a thermal runaway alarm signal, increasing the risk of false alarms. In addition, this method requires the use of additional detection equipment to achieve this, which will also increase the space occupied by the equipment and heat emissions, and also increase the corresponding production costs.

[0015] In view of this, how can we achieve accurate thermal runaway detection of lithium iron phosphate batteries with existing pressure sensors and BMS without adding additional detection equipment, and effectively shorten the monitoring cycle and reduce the risk of false alarms. Therefore, we creatively introduced a dual-mode switching mechanism to set the pressure sensor to low power mode and high power mode, but this also introduced a new problem, that is, in the low-power operation state, because traditional thermal runaway detection relies on high-power sensors, the continuous operation of high-power sensors will greatly increase the energy consumption of the system, which conflicts with the design goal of the low-power mode, making these devices unable to continue to work in low-power mode, resulting in the inability to achieve real-time detection. In addition, in low-power mode, the data processing capability and signal acquisition frequency are also greatly reduced, and it is difficult to process complex multi-dimensional signals in real time, resulting in its limitation in low-power mode. This is why even if the existing sensors have high-power and low-power modes, they are not used in thermal runaway detection.

[0016] To overcome this problem, this solution breaks away from the inherent logic in low-power mode and uses a pressure sensor instead of a BMS to calculate the pressure slope value. It also uses different monitoring cycles and uses the intelligent wake-up mechanism of the pressure sensor to wake up the BMS and give an alarm to the entire vehicle after the pressure sensor determines that thermal runaway has occurred. This allows real-time detection of abnormal pressure slopes in low-power mode, solving the problem that traditional methods cannot achieve real-time detection in low-power mode.

[0017] At the same time, without adding other components to the battery pack, this solution creatively adopts a new judgment logic method by optimizing the judgment logic and detection cycle of the voltage slope threshold, that is, the values ​​of the subsequent monitoring cycles are only compared with the current atmospheric pressure value (or the set threshold). Compared with the atmospheric pressure value, that is, the threshold value has a certain increment, which means that the pressure in the pack has increased, which is the most obvious feature of thermal runaway gas production. Instead of using a continuous incremental judgment method, the existing pressure sensor and BMS are used to achieve high-precision detection, avoiding hardware redundancy, and being able to more accurately monitor and report thermal runaway signals. Under the condition of no false alarms, the thermal runaway alarm time of batteries such as those with low gas production and low exhaust rate can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the process framework of method 1 in the present invention.

[0019] Figure 2 This is a schematic diagram of the process framework of method 2 in the present invention.

[0020] Figure 3 It is a schematic diagram of the slope cycle cumulative value calculation method of the present invention. DETAILED DESCRIPTION

[0021] The following is further described in detail through specific implementation methods:

[0022] Embodiment 1

[0023] A power battery thermal runaway monitoring and alarm method in this embodiment determines the operating power consumption of the pressure sensor and distinguishes it, so that the pressure value slope is calculated through different modules, thereby optimizing the thermal runaway alarm strategy of the pressure sensor or BMS system. And by optimizing the slope parameter value and increasing the determination cycle of the thermal runaway signal, it can be ensured that the lithium iron phosphate battery can send out a thermal runaway alarm signal in time after thermal runaway, thereby greatly shortening the alarm cycle and reducing the risk of false alarms. In this embodiment, the alarm method is to use a pressure sensor to periodically obtain the battery pressure value in real time, and determine the power consumption mode currently operated by the pressure sensor. When it is determined that the current pressure sensor is in low power consumption mode, it enters monitoring mode 1; when it is determined that the current pressure sensor is in high power consumption mode, it enters monitoring mode 2.

[0024] In this embodiment, a pressure sensor is used to periodically monitor and obtain the battery pressure value in real time. When in low power consumption mode, it is generally set to 1s as a cycle, and when in high power consumption mode, it is set to 30ms as a cycle. The real-time voltage value obtained is sent in each cycle.

[0025] In this embodiment, as shown in the attached Figure 1As shown, monitoring mode 1 is that the pressure sensor is in low power mode. At this time, the pressure sensor is still in working state, but in low power mode, and continuously monitors the pressure changes of the battery pack. The whole vehicle and BMS system are in dormant state to save power. At this time, the pressure slope value of the battery pack pressure, that is, the pressure change rate, is calculated by the pressure sensor. When the pressure slope value ≥ the threshold value and reaches the set condition for N consecutive cycles, the sensor will wake up the BMS system; where N ≥ 1, and the threshold is 0.3 ~ 0.5kPa / s. The specific monitoring cycle can be adaptively adjusted according to the actual working conditions to illustrate that the detection of this scheme is not a continuous increase, but as long as it is higher than the first basic value, that is, the monitored atmospheric pressure value or the set threshold, it can be increased compared to it; at the same time, by increasing the additional measurement cycle, the value of the pressure slope value can be reduced to meet the alarm when the value is reached, and avoid false alarms.

[0026] In this embodiment, when in low power consumption mode, the pressure slope value of the battery pack is directly calculated by the pressure sensor, and the threshold is set to 0.3kPa / s. When the pressure slope value is monitored to be ≥0.3kPa / s, the pressure slope value of the next four consecutive cycles is continuously monitored, and it is determined whether the value of each cycle reaches the set condition. Among them, the set condition is to continuously determine the cumulative pressure slope value within 4 cycles to simplify the monitoring method, and the cumulative value continues to increase within 4 cycles to reach the set value, that is, to determine whether the pressure slope value of the four cycles exceeds the threshold value. If it exceeds continuously, it is considered that the corresponding condition is met, and the BMS system, that is, the battery management system, will be awakened.

[0027] In traditional thermal runaway detection, based on the empirical summary of battery thermal runaway characteristics and the trade-off of system performance, during normal charging and discharging, the battery may experience pressure fluctuations due to factors such as temperature changes and mechanical vibrations. If the slope threshold is set too low (such as 0.3kPa / s), these normal fluctuations may be misjudged as thermal runaway, resulting in false alarms. Therefore, in order to ensure that the detection sensitivity and false alarm rate are balanced in most cases, the slope threshold is set to 0.5kPa / s based on the empirical value obtained from a large amount of experimental data for two cycles, and both cycles are determined in an incremental manner, that is, a continuous growth method is required to avoid increasing the risk of false alarms, and the threshold will not be adjusted downward. In addition, traditional thermal runaway detection is mainly aimed at ternary lithium batteries, which have a high gas production rate and obvious pressure changes during thermal runaway. The threshold of 0.5kPa / s can effectively capture this rapidly changing pressure signal, and for batteries with high gas production rates, a lower threshold may lead to premature alarms, while a higher threshold may delay alarms. And limited by the accuracy and sampling frequency of the pressure sensor, a lower threshold may cause signal noise interference, affecting the accuracy of the test results, while a threshold of 0.5kPa / s can achieve reliable detection within the sensor performance range, so it is generally not considered to adjust the threshold, or even adjust it downward. And for lithium iron phosphate batteries with a slower gas production rate or ternary batteries with a faster but discontinuous increase in gas production rate, there may also be a problem of late alarm time or missed alarms.

[0028] However, after fully considering the characteristics of lithium iron phosphate batteries, this solution boldly breaks through the inherent thinking of threshold setting and instead adjusts the threshold downward to achieve more accurate detection while overcoming the risk of false alarms.

[0029] At the same time, this solution creatively abandons the original determination method that requires continuous increments of consecutive cycles, and instead uses a cumulative calculation method to determine the voltage value of each cycle and the size of the set threshold. Figure 3 As shown, the time nodes of the four cycles are marked as A, B, C, D, and E respectively, that is, starting from 0 o'clock, the pressure before point A is below the threshold, which can be equivalent to the atmospheric pressure value. When the monitoring determines that the pressure slope value is ≥0.3kPa / s, the first cycle segment node is A, the second cycle segment node is B, and so on, then B, C, D, and E are the cycles collected from point A. Then determine the cumulative pressure slope values ​​of the four cycles respectively, that is, the following conditions must be met at the same time, then the sensor will wake up the BMS system:

[0030] AB ≥ 0.3 kPa / s; that is, the pressure slope value in the first cycle is ≥ 0.3 kPa / s.

[0031] And accumulated to the second cycle AC≥0.6kPa / s; that is, the accumulated pressure slope value in the second cycle is ≥0.6kPa / s.

[0032] And accumulated to the third cycle AD≥0.9kPa / s; that is, the accumulated pressure slope value in the third cycle is ≥0.9kPa / s.

[0033] And accumulated to the fourth cycle AE≥1.2kPa / s; that is, the accumulated pressure slope value in the fourth cycle is ≥1.2kPa / s.

[0034] Through this judgment logic, even if the battery thermal runaway is triggered, the pressure of the battery gas production cannot continue to rise, because the gas production is fast and slow, and the pressure will drop a little when it is slow. At this time, the above-threshold method of this solution is used for judgment, which can effectively avoid missed reports or false alarms and improve monitoring accuracy.

[0035] And because thermal runaway is a rapidly developing process, especially in ternary lithium batteries, it may only take a few seconds to a few minutes from gas production to thermal runaway. Shorter cycles (such as 3 cycles) can ensure that the system responds quickly and alarms in time, while longer cycles may cause alarm delays and fail to prevent the further development of thermal runaway in time. The setting of a shorter cycle can verify whether the change of the pressure slope is stable in a short time, avoid false alarms caused by instantaneous fluctuations, and quickly confirm the validity of the signal, while longer cycles may introduce more noise interference. Therefore, conventional thermal runaway detection will shorten the detection cycle to shorten the detection time. And in this scheme, if in order to shorten the detection time, the continuous detection cycle should be further shortened. However, this scheme goes the other way. Its purpose is that this scheme first reduces the slope threshold, and because lithium iron phosphate batteries have the characteristics of slow gas production rate and small gas production, the gas volume produced in the same cycle time is less, which makes it difficult to capture. In order to predict the abnormality, it takes a longer time. Therefore, in order to more accurately detect the changes in the internal voltage of the battery, the monitoring cycle can be appropriately extended, and at the same time, the threshold can be lowered, so that the detection time is greatly shortened, which seems to extend the duration. It can also ensure the accuracy and timeliness of the detection and reduce the risk of false alarms. Secondly, this solution optimizes the judgment logic and does not use a continuous step-by-step method to make judgments. Instead, it compares each cycle value with the set threshold. Therefore, it can appropriately increase the monitoring cycle, improve monitoring accuracy, and reduce the risk of missed or false alarms.

[0036] When the above conditions are met, the pressure sensor will wake up the BMS. After being awakened, the BMS will promptly receive and judge the fault information and battery pack information reported by the sensor, and report to the vehicle in a timely manner when thermal runaway is detected so that corresponding measures can be taken.

[0037] In this embodiment, the BMS will receive the sensor fault flag signal reported by the sensor, as well as other temperature and voltage signals of the battery pack, and determine whether there is a risk of thermal runaway based on the received signal. If a thermal runaway fault is detected, the fault information will be reported in a timely manner. The pressure sensor is used to monitor the pressure changes of the battery pack to determine whether there is an abnormal situation. When the pressure slope is detected to continue to increase and reach the set value, the BMS is awakened for further analysis and processing to ensure the safety of the battery.

[0038] In this embodiment, a sliding window algorithm may be used to calculate the pressure slope to ensure the real-time and accuracy of the data.

[0039] When it is detected that the pressure sensor is in high power consumption mode, monitoring mode 2 is used for detection. Figure 2 As shown, at this time, the pressure sensor is in high power consumption mode, and the pressure value it monitors is only transmitted to the BMS system, that is, the pressure sensor continues to send the detected pressure value to the BMS. Compared with the low power consumption mode, the pressure sensor is no longer responsible for calculating the pressure slope, but uses the BMS to calculate the pressure value.

[0040] After the BMS system receives the pressure value sent by the pressure sensor, it actively calculates the pressure slope value of the battery pack. When the pressure slope value is ≥ the threshold, that is, ≥0.3kPa / s, and continues to meet the set conditions for N cycles, the BMS will consider that there is an abnormality in the battery pack. At this time, the BMS receives and judges the battery pack information and reports a thermal runaway fault.

[0041] In this embodiment, the calculation method of the set conditions is the same as the calculation method in method 1, that is, the accumulated pressure slope value in 4 cycles is continuously judged. When AB ≥ 0.3 kPa / s in the first cycle; and AC ≥ 0.6 kPa / s in the second cycle; and AD ≥ 0.9 kPa / s in the third cycle; and AE ≥ 1.2 kPa / s in the fourth cycle, it indicates that the pressure slope continues to increase in 4 consecutive cycles, and the accumulated slope of each cycle reaches the set value. At this time, the BMS will determine that there is an abnormality.

[0042] At the same time, BMS not only relies on the pressure slope, but also combines battery pack information such as temperature, voltage and other signals for comprehensive judgment. When BMS determines that the battery pack is at risk of thermal runaway, that is, the pressure slope meets the above conditions, it will promptly obtain the temperature, voltage and other signals related to the battery pack. When the temperature and voltage are also abnormal, it will comprehensively determine that the battery pack is at risk of thermal runaway and report it to the vehicle in a timely manner. After receiving the fault information, the vehicle system can take corresponding safety measures, such as cutting off the power supply, starting the cooling system or reminding the driver, to ensure safety.

[0043] In high power consumption mode, the pressure sensor is only responsible for sending the pressure value, while the BMS is responsible for calculating the pressure slope value and combining other signals to determine whether the battery pack is at risk of thermal runaway. When the pressure slope value continues to increase and reaches the set value, and other signals also indicate abnormalities, the BMS will promptly report the thermal runaway fault to the vehicle system to ensure battery safety. In this embodiment, the calculation task is assigned to the BMS, which reduces the power consumption and complexity of the sensor, while effectively improving the reliability of the system, enabling the battery pack to alarm the thermal runaway signal within 10 seconds, greatly shortening the alarm cycle.

[0044] In this embodiment, based on the intelligent switching of high power consumption mode and low power consumption mode, without adding additional hardware, the dual-mode operation mechanism is adopted which not only solves the problems of high false alarm rate and slow response speed in traditional thermal runaway detection, but also optimizes the detection logic specifically for the characteristics of lithium iron phosphate batteries, such as low gas production and low exhaust rate, reduces the slope threshold and increases the judgment period, significantly shortens the alarm time, and realizes high-precision detection and rapid alarm of thermal runaway of the battery pack.

[0045] While traditional thermal runaway detection usually requires the addition of additional gas sensors or complex monitoring equipment, this embodiment only uses existing pressure sensors and BMS, and through dual-mode switching and optimized judgment strategies, it fully utilizes hardware resources and avoids the problem of hardware redundancy in traditional methods. Traditional methods usually adopt a single operating mode, which cannot take into account both power consumption and detection accuracy. This embodiment achieves a balance between the two through dual-mode switching. In addition, traditional methods usually cannot achieve real-time detection in low-power mode. This solution overcomes this technical problem through the intelligent wake-up mechanism of the pressure sensor, taking into account high-precision detection and low power consumption requirements, and is suitable for different working conditions. In particular, in view of the characteristics of lithium iron phosphate batteries with low gas production and low exhaust rate, the voltage slope threshold is reduced, the judgment cycle is increased, and the risk of false alarms is reduced, so that it can also accurately alarm through the slope value, overcoming the previous situation where only pressure increments can be used for detection, which causes false alarms, and greatly shortens the detection time.

[0046] Embodiment 2

[0047] In this embodiment, the BMS system also includes that after receiving the battery pack information, it first determines whether the battery pack temperature has reached an abnormal state. When the temperature is determined to be abnormal, the battery pack voltage is judged as abnormal. When at least two indicators among the pressure slope, temperature and voltage meet the abnormal value judgment, a thermal runaway report is performed. That is, as long as two of the indicators meet the abnormal judgment conditions, a thermal runaway report will be performed. The method of using two combined signals for alarm can effectively reduce the probability of false alarms and improve the accuracy of thermal runaway alarms.

[0048] Among them, the battery pack information includes pressure signals, temperature signals, voltage signals and signal synchronization. The pressure signal is that the pressure sensor monitors the internal pressure of the battery pack in real time and sends the pressure value to the BMS. The temperature signal is to arrange multiple temperature sensors (such as NTC or thermocouples) inside the battery pack to monitor the temperature of the battery cells and modules in real time. The voltage signal is to monitor the voltage of the battery cells and modules in real time through the voltage acquisition module of the BMS. Signal synchronization means that the BMS needs to synchronize the pressure, temperature and voltage signals in time to ensure that the data acquired at the same time point is matched.

[0049] First, according to the set conditions in Example 1, when it is determined that the pressure slope meets the conditions and is determined to be abnormal, the BMS will enter the next step of temperature and voltage judgment to determine the abnormal conditions of temperature and voltage in real time.

[0050] Among them, temperature is a direct indicator of thermal runaway. BMS determines the battery pack temperature based on the data from the temperature sensor, including the temperature rise rate, temperature absolute value and temperature distribution status.

[0051] For the temperature rise rate, the battery cell temperature rise rate is determined to be ≥1°C / s; for the absolute value of temperature, the battery cell temperature is determined to be ≥60°C; for the temperature distribution state, it is determined whether the temperature difference at different positions in the battery pack exceeds the limit value, such as 10°C. If it exceeds the limit value, it indicates local overheating.

[0052] When the temperature signal meets any of the above conditions, it is determined that the temperature signal is abnormal. At this time, the pressure slope and temperature are monitored to meet the abnormal indicators, that is, two indicators are abnormal, which can trigger the thermal runaway report. If the current temperature is detected to be normal, that is, the abnormal temperature signal is not triggered, the voltage signal is determined.

[0053] The voltage signal is an indirect indicator of thermal runaway. The BMS determines the voltage based on the data from the voltage acquisition module, including the voltage drop rate, voltage absolute value and voltage consistency.

[0054] For the voltage drop rate, the battery cell voltage drop rate is determined to be ≥ 0.1V / s; for the voltage absolute value, the battery cell voltage is determined to be lower than the set value; for the voltage consistency, it is determined whether the voltage difference between different cells in the battery pack exceeds the set range. If it exceeds, it indicates that the battery consistency has deteriorated. If the voltage signal meets any of the above conditions, the BMS will determine that there is a risk of thermal runaway and perform early warning processing.

[0055] At the same time, in this embodiment, when it is determined that the pressure slope does not meet the conditions, that is, the pressure slope is not abnormal, the BMS will also enter the next step of temperature and voltage judgment to determine the abnormal conditions of temperature and voltage in real time. If the detected temperature and voltage are also abnormal at the same time, that is, there are two indicators that are abnormal at the same time, the BMS will also determine that there is a risk of thermal runaway and perform early warning processing.

[0056] When at least two of the pressure slope, temperature and voltage signals meet their respective judgment conditions, the BMS can confirm that the battery pack is at risk of thermal runaway in order to improve the accuracy of the judgment.

[0057] In this embodiment, when processing temperature and voltage signals, a filtering algorithm can be used to smooth the temperature and voltage to reduce noise interference and improve the accuracy and effectiveness of the calculation. By combining pressure, temperature and voltage signals, comprehensive detection and accurate judgment of thermal runaway of the battery pack can be achieved. At the same time, the pressure slope is used as an early indicator, and temperature and voltage are used as direct and indirect indicators. The combination of the three can significantly improve the accuracy and reliability of thermal runaway detection, and through reasonable calculation methods, the efficiency and stability of the system can be ensured, the detection alarm cycle can be greatly shortened, and the risk of false alarms can be reduced.

[0058] Embodiment 3

[0059] In this embodiment, the external environmental parameters of the battery pack are also acquired in real time, and the thermal runaway judgment threshold is dynamically adjusted according to changes in environmental factors. The external environmental parameters include ambient temperature, humidity, vibration, and charge and discharge rate.

[0060] In actual applications, the working state of the battery pack will be affected by many factors such as ambient temperature, humidity, vibration, charge and discharge rate, etc., which will have a certain impact on the monitoring accuracy of the battery pack, resulting in inaccurate detection and false alarms.

[0061] In this embodiment, an ambient temperature sensor is arranged outside the battery pack to monitor the ambient temperature in real time. A humidity sensor is arranged outside the battery pack to monitor the ambient humidity in real time. Excessive humidity may affect the sealing of the battery pack. A vibration sensor is arranged outside the battery pack to monitor the vibration of the vehicle in real time. Severe vibration may cause damage to the internal structure of the battery. The charging and discharging current and power of the battery pack are monitored in real time through the BMS. By acquiring real-time data such as external ambient temperature, humidity, vibration, and charging and discharging rate, the pressure slope value threshold is dynamically adjusted to ensure the rationality and accuracy of the judgment.

[0062] In this embodiment, the adjustment formula for setting the pressure slope value is:

[0063] P=P 0 ×(1+k T×ΔT+k V ×ΔV+k H ×ΔH);

[0064] Where, P is the pressure slope threshold after dynamic adjustment (kPa / s); P 0 is the basic pressure slope threshold, in this embodiment, the value is 0.3 kPa / s. T is the temperature influence coefficient, which indicates the influence of temperature change on the pressure slope threshold, and can be 0.01-0.05. ΔT is the difference between the ambient temperature and the reference temperature (℃); k V is the vibration influence coefficient, which indicates the influence of vibration intensity on the pressure slope threshold, and can be 0.02-0.1. ΔV is the difference between the vibration intensity and the reference vibration intensity (g, unit of gravity acceleration); k H is the humidity influence coefficient, which indicates the influence of humidity change on the pressure slope threshold, and can be 0.005-0.02. ΔH is the difference between ambient humidity and reference humidity (%RH).

[0065] The pressure slope threshold is dynamically adjusted according to changes in external environmental factors. When in a high temperature environment, that is, ΔT>0, the pressure slope threshold is automatically adjusted to increase to avoid false alarms due to the natural increase in pressure caused by high temperature; when in a low temperature environment, that is, ΔT<0, the pressure slope threshold is automatically adjusted to decrease, which can increase the sensitivity to abnormal pressure and improve the timeliness and accuracy of monitoring.

[0066] In a high vibration environment, that is, ΔV>0, the pressure slope threshold is automatically adjusted to increase, which can effectively reduce false alarms caused by vibration interference; in a low vibration environment, that is, ΔV<0, the pressure slope threshold is automatically adjusted to decrease, which can improve the detection sensitivity.

[0067] In a high humidity environment, that is, ΔH>0, the pressure slope threshold is automatically adjusted to increase, which can avoid false alarms of pressure fluctuations caused by humidity changes; in a low vibration environment, that is, ΔH<0, the pressure slope threshold is automatically adjusted to decrease, which can improve the detection sensitivity.

[0068] Example 1: The current environment is high temperature, low vibration, and normal humidity.

[0069] If the current ambient temperature is detected to be 40°C and the standard temperature is 25°C, then ΔT = 15°C. If the current vibration intensity is 0.3g and the standard vibration intensity is 0.5g, then ΔV = -0.2g. If the current ambient humidity is 50%RH and the standard ambient humidity is 50%RH, then ΔH = 0. At the same time, parameter k T , k V , k HThe values ​​are 0.02, 0.05, and 0.01 respectively. According to the adjustment formula, P can be calculated as 0.387 kPa / s. At this time, the pressure slope threshold is adjusted from 0.3 kPa / s to 0.387 kPa / s to improve detection accuracy and reduce the risk of false alarms.

[0070] Example 2: The current environment is low temperature, high vibration, and high humidity.

[0071] If the current ambient temperature is detected to be 10°C, the vibration intensity is 1.0g, and the ambient humidity is 80%RH, the corresponding standard values ​​of each indicator remain unchanged. Then ΔT=-15°C, ΔV=0.5g, ΔH=30. At the same time, parameter k T , k V , k H The values ​​remain unchanged, that is, they are 0.02, 0.05, and 0.01 respectively. According to the adjustment formula, P can be calculated as 0.3075 kPa / s. At this time, the pressure slope threshold is adjusted from 0.3 kPa / s to 0.3075 kPa / s to improve the detection sensitivity and reduce the risk of false alarms.

[0072] In this embodiment, the pressure slope threshold is dynamically adjusted based on the real-time acquisition of external environmental temperature, humidity, vibration and other influencing factors to ensure that the thermal runaway judgment is more reasonable and accurate. At the same time, the calculation method in this embodiment is simple and the amount of calculation is small. The pressure sensor can adjust the sampling frequency and filter parameters in real time according to the environmental data to ensure the accuracy of the pressure value. The BMS can calculate the pressure slope threshold in real time according to the environmental data and the dynamic adjustment formula, and make thermal runaway judgments in combination with temperature, voltage and other signals, shortening the judgment time while reducing the risk of false alarms, improving detection efficiency, and effectively improving the safety and reliability of the battery pack.

[0073] While traditional thermal runaway judgment usually relies only on internal battery signals (such as pressure, temperature, and voltage) for thermal runaway detection, this embodiment innovatively introduces external environmental data (temperature, humidity, and vibration), and dynamically adjusts the pressure slope threshold to achieve collaborative analysis of internal and external data, allowing the system to distinguish between real thermal runaway inside the battery and pressure fluctuations caused by environmental factors, thereby significantly reducing the false alarm rate. At the same time, the calculation formula used is simple and efficient, with extremely small calculation amount, suitable for running in resource-limited embedded systems (such as BMS), and can complete environmental data processing and threshold updates within milliseconds to ensure the real-time nature of thermal runaway judgment. Furthermore, the pressure sensor not only serves as a data acquisition device, but can also dynamically adjust the sampling frequency and filtering parameters according to environmental data to ensure the accuracy of the pressure value, so that the sensor can adapt to complex and changeable environmental conditions and further improve data reliability.

[0074] In this embodiment, by combining multi-dimensional data such as temperature, humidity, and vibration, the battery status can be evaluated more comprehensively, avoiding misjudgment caused by a single signal, significantly reducing the false alarm rate of thermal runaway, and at the same time improving detection efficiency, providing strong protection for the safe management of battery packs.

[0075] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A power battery thermal runaway monitoring and alarm method, characterized in that: The pressure sensor is used to periodically obtain the battery pressure value in real time to determine the current power consumption mode of the pressure sensor. When the pressure sensor is in the low power consumption mode, mode 1 is entered; when the pressure sensor is in the high power consumption mode, mode 2 is entered; Method 1: put the vehicle and BMS system in dormant state, calculate the battery pack pressure slope value through the pressure sensor, and wake up the BMS system when the pressure slope value is ≥ the threshold value and reaches the set conditions for N consecutive cycles, receive and judge the fault information and battery pack information, and report when thermal runaway is detected; Method 2: The monitored pressure value is transmitted only to the BMS system. The BMS system calculates the pressure slope value based on the pressure value. When the pressure slope value ≥ the threshold value and meets the set conditions for N consecutive cycles, the BMS receives and judges the battery pack information and reports a thermal runaway fault; where N ≥ 1.

2. A power battery thermal runaway monitoring and alarm method according to claim 1, characterized in that: The setting condition is to continuously determine the accumulated pressure slope value within 4 cycles, and the accumulated value continuously increases within the 4 cycles to reach the set value.

3. A power battery thermal runaway monitoring and alarm method according to claim 1, characterized in that: The threshold value is 0.3-0.5 kPa / s.

4. A power battery thermal runaway monitoring and alarm method according to claim 2, characterized in that: The setting value is calculated by setting the time nodes of the four cycles to be A, B, C, D, and E respectively; the judgment method is expressed as AB≥0.3kPa / s in the first cycle; and accumulated to AC≥0.6kPa / s in the second cycle; and accumulated to AD≥0.9kPa / s in the third cycle; and accumulated to AE≥1.2kPa / s in the fourth cycle.

5. A power battery thermal runaway monitoring and alarm method according to claim 1, characterized in that: The fault information is a sensor fault flag signal.

6. A power battery thermal runaway monitoring and alarm method according to claim 1, characterized in that: The battery pack information includes battery pack temperature and voltage.

7. A power battery thermal runaway monitoring and alarm method according to claim 6, characterized in that: It also includes that after receiving the battery pack information, the BMS system first determines whether the battery pack temperature has reached an abnormal state. When the temperature is determined to be abnormal, the battery pack voltage is judged as abnormal. When at least two of the pressure slope, temperature and voltage meet the abnormal value judgment, a thermal runaway report is made.

8. A power battery thermal runaway monitoring and alarm method according to claim 7, characterized in that: The determination of the battery pack temperature includes the temperature rise rate, the absolute value of the temperature and the temperature distribution state; the determination of the voltage includes the voltage drop rate, the absolute value of the voltage and the voltage consistency.

9. A power battery thermal runaway monitoring and alarm method according to claim 1, characterized in that: It also includes real-time acquisition of the external environmental parameters of the battery pack and dynamic adjustment of the thermal runaway judgment threshold according to changes in environmental factors.

10. A power battery thermal runaway monitoring and alarm method according to claim 9, characterized in that: The external environmental parameters include ambient temperature, humidity, vibration, and charge and discharge rate.

Images