Battery box and temperature acquisition and fire detection method thereof

Abstract

The present application relates to a kind of battery box and its temperature acquisition and fire detection method, acquisition covers the infrared thermal imaging of all temperature sampling points of battery box in the temperature to be measured;In the acquisition area of infrared thermal imaging, the infrared light spot of known temperature is projected by infrared emission reference source, and the temperature of infrared light spot is used as reference temperature to determine the temperature value of each position on infrared thermal imaging;When there is a point on infrared thermal imaging that exceeds the temperature of thermal safety risk value, the position of the point in the battery box is obtained and alarm is given.This battery box temperature acquisition and fire detection method can solve the problem of few acquisition points, unable to cover all key points and monitoring blind area of prior art on battery box.

Description

Technical Field

[0001] This invention belongs to the field of temperature acquisition and control of high-voltage power supply systems for electric vehicles, and in particular relates to a battery box and its temperature acquisition and fire detection method. Background Technology

[0002] Temperature monitoring within the battery pack of an electric vehicle (EV) is crucial for its safety. Typically, EV battery cells are connected in series via aluminum alloy bars, then fastened with bolts and connected to aluminum / copper busbars for charging and discharging. Battery temperature monitoring usually requires checking the temperature of all individual cells, the aluminum alloy bars, and the bolt fastening points of the busbars to prevent internal loosening, increased contact resistance, which could lead to overheating, arcing, or even fire. Figure 1 The battery box shown requires temperature monitoring of 48 individual cells, 96 aluminum bars, and 10 bolt fastening points, totaling 154 temperatures. The requirement for 6 internal battery temperature sampling points is relatively high.

[0003] like Figure 2 As shown, currently, NTC sampling sensors are typically used to select a few typical temperature sampling points 6 inside the battery box, while other temperature points are estimated using interpolation methods. This method suffers from insufficient temperature sampling data due to the limited number of temperature detection points, leading to monitoring blind spots. Furthermore, it requires high consistency from the NTC sensors; when discrepancies occur between NTC sensors, the temperature sampling error inside the battery box is significant due to different reference standards.

[0004] Chinese patent application CN111403836A discloses a battery pack temperature detection system and method. This system combines the temperatures of multiple temperature points within the battery pack detected by the battery management system with an overall infrared thermal image of all individual battery cells. Using the temperatures of the temperature points as a reference temperature, the system calculates the temperature of each individual battery cell on the overall infrared thermal image, thus collecting the temperature of each battery cell within the battery pack. However, this patent only detects the temperature of a portion of the batteries and cannot monitor the temperatures of welding points and bolt fastening points, nor can it quickly locate the maximum or minimum temperature values ​​within the battery pack. Therefore, it cannot accurately determine the fire situation within the battery pack and promptly issue alarm and fire extinguishing signals. Summary of the Invention

[0005] The purpose of this invention is to provide a battery box and its temperature acquisition and fire detection method to solve the problem of incomplete temperature acquisition of battery boxes in the prior art, which leads to the risk of missing fire detection.

[0006] To achieve the above objectives, the present invention includes:

[0007] A technical solution for a battery box temperature acquisition and fire detection method involves acquiring infrared thermal images covering all temperature sampling points inside the battery box; projecting infrared spots of known temperature into the acquisition area of ​​the infrared thermal image using an infrared emission reference source, and using the temperature of the infrared spots as a reference temperature to determine the temperature values ​​at various locations on the infrared thermal image; when a point on the infrared thermal image has a temperature exceeding the thermal safety risk value, obtaining the location of that point inside the battery box and triggering an alarm.

[0008] The beneficial effects of this invention are as follows: By projecting an infrared light spot of known temperature onto the battery box using an infrared emission reference source, the temperature and location of the temperature sampling point within the battery box can be determined. Comprehensive collection of temperature data within the battery box enables the acquisition of all critical information, solving the problems of limited temperature sampling points, inability to cover all critical points, and blind spots in existing technologies. Based on the temperature conditions within the battery box, early warnings are issued for points exceeding thermal safety risk values, enabling timely assessment of fire situations within the battery box and the issuance of alarm and fire extinguishing signals, thus contributing to the maintenance of electric vehicle battery safety.

[0009] Furthermore, the process of determining whether there are points on the infrared thermal image with temperatures exceeding the thermal safety risk value includes the following steps: dividing the infrared thermal imaging coverage area into regions according to the distribution of different types of temperature sampling points inside the battery box, and setting different thermal safety risk values ​​according to the temperature characteristics of temperature sampling points in different regions; when there are points on the infrared thermal image with temperatures higher than the set value, determining whether the temperature of the point exceeds the thermal safety risk value of the region where the point is located, and if it does, then there are points on the infrared thermal image with temperatures exceeding the thermal safety risk value.

[0010] The beneficial effects of this invention are as follows: different thermal safety risk values ​​are set according to the temperature characteristics of temperature sampling points in different areas inside the battery box. First, it is determined whether there are points in the infrared thermal imaging that exceed a single set value. Then, it is determined to determine the area to which the points that exceed the set values ​​belong, and whether the temperature of the point exceeds the thermal safety risk value.

[0011] Furthermore, the corresponding positions of points on the infrared thermal image inside the battery box are determined by the following method: an infrared emission reference source projects an infrared spot at a designated position inside the battery box; based on the position of the infrared spot inside the battery box and the relative position of the infrared spot with any other point on the infrared thermal image, the position of any other point inside the battery box is obtained.

[0012] The beneficial effects of this invention are as follows: Using the position of the infrared emission reference source projected inside the battery box as a positional reference, and combining the relative positions of the infrared thermal image spot and the other temperature sampling points with the position of the infrared spot inside the battery box, the positions of the other temperature sampling points inside the battery box can be obtained. Without adding other positioning equipment, the location of points inside the battery box can be achieved using an existing infrared emission reference source and simple calculations. This positioning method is simple and has high accuracy.

[0013] Furthermore, when the battery box is liquid-cooled, the infrared light spot is projected onto the coolant inlet.

[0014] The beneficial effects of this invention are as follows: Based on the relatively constant temperature at the coolant inlet of the battery box, and by using an infrared emission reference source to emit an infrared spot at a constant power, the superposition of these two constant temperatures ensures that the temperature of the infrared spot projected at the coolant inlet remains relatively constant, serving as a constant temperature reference. This makes the temperature determination of points collected inside the battery box relatively accurate.

[0015] Furthermore, the types of temperature sampling points include: temperature sampling points on each individual cell, temperature sampling points on the welding points of the aluminum bars used for connecting the electrodes of the individual cells, and temperature sampling points on the bolt fastening points of the conductive busbars connecting the individual cells to the positive and negative terminals of the battery box.

[0016] The beneficial effects of this invention are as follows: Since the individual cells, aluminum busbar welding points, and conductive busbar bolt fastening points within the battery box have different heat generation powers and specific heat capacities, three zones are set up according to these three types. Different temperature thresholds set based on the temperature characteristics of these three zones can make the battery box temperature warning results more accurate and minimize false alarms.

[0017] Furthermore, the thermal safety risk value is calculated using the temperature and the rate of temperature rise at the temperature sampling point.

[0018] The beneficial effects of this invention are as follows: the early warning result of a single battery box temperature may still have false alarms. By taking into account the temperature rise rate and calculating the thermal safety risk value based on these two parameters, the early warning result of the battery box temperature can be made more accurate.

[0019] A battery box includes individual battery cells, aluminum bars for connecting the electrodes of the individual cells, and conductive busbars for connecting the individual cells to the positive and negative terminals of the battery box. It also includes an infrared camera and an infrared emission reference source disposed within the battery box. The infrared camera is used to acquire infrared thermal images covering the locations of all individual cells, aluminum bar welding points, and conductive busbar bolt fastening points within the battery box. The infrared emission reference source projects an infrared spot of known temperature within the acquisition area of ​​the infrared thermal image, using the temperature of the infrared spot as a reference temperature to determine the temperature value at each location on the infrared thermal image. When a point on the infrared thermal image has a temperature exceeding a thermal safety risk value, the location of that point inside the battery box is obtained, and an alarm is triggered.

[0020] Furthermore, the process of determining whether there are points on the infrared thermal image with temperatures exceeding the thermal safety risk value includes the following steps: dividing the infrared thermal imaging coverage area into regions according to the distribution of different types of temperature sampling points inside the battery box, and setting different thermal safety risk values ​​according to the temperature characteristics of temperature sampling points in different regions; when there are points on the infrared thermal image with temperatures higher than the set value, determining whether the temperature of the point exceeds the thermal safety risk value of the region where the point is located, and if it does, then there are points on the infrared thermal image with temperatures exceeding the thermal safety risk value.

[0021] Furthermore, the corresponding positions of points on the infrared thermal image inside the battery box are determined by the following method: an infrared emission reference source projects an infrared spot at a designated position inside the battery box; based on the position of the infrared spot inside the battery box and the relative position of the infrared spot with any other point on the infrared thermal image, the position of any other point inside the battery box is obtained.

[0022] Furthermore, when the battery box is liquid-cooled, the infrared light spot is projected onto the coolant inlet. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the internal temperature detection requirements of the battery box in the battery system of the present invention;

[0024] Figure 2 This is a schematic diagram showing the distribution of temperature detection points inside the battery box according to the present invention;

[0025] Figure 3 This is a schematic diagram of the gridded division for battery box temperature acquisition according to the present invention;

[0026] Figure 4 This is a schematic diagram of the battery box temperature acquisition and fire detection of the present invention;

[0027] Figure 5 The present invention provides a method for determining the thermal safety risk of a single battery cell.

[0028] Figure 6The flowchart of the temperature acquisition and fire detection method of the present invention is as follows;

[0029] Explanation of reference numerals in the attached figures:

[0030] 1. Aluminum bar welding point; 2. Bolt fastening point; 3. Total positive; 4. Total negative; 5. MSD; 6. Temperature sampling point; 7. Infrared camera; 8. Infrared emission reference source; 9. Laser emitter. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] An embodiment of a method for collecting battery box temperature and detecting fire:

[0033] This invention employs a method for acquiring battery box temperature and detecting fires. Three components—an infrared camera 7, an infrared emission reference source 8, and a laser emitter 9—are installed on one side inside the battery box to acquire its temperature. The infrared thermal image of the battery box's internal temperature is acquired using a monocular or binocular infrared camera 7.

[0034] An infrared emission reference source 8, serving as an electronic reference source for battery box temperature acquisition, is installed below the infrared camera 7. It emits an infrared light spot at a constant power to the acquisition area of ​​the infrared camera 7 for acquisition. The emission power of the infrared emission reference source 8 is adjustable, allowing for experimental calibration of the infrared light spot that generates a constant, defined temperature on the material at the irradiation point. This defined constant temperature is also reflected in the infrared thermal image, serving as a reference temperature for the infrared thermal image. Based on the reference temperature generated by the emitted infrared light spot, the temperature at various locations on the acquired infrared thermal image can be further obtained.

[0035] The infrared emission reference source 8 also provides a primary reference for locating other temperature sampling points 6, i.e., it provides a positional reference. The location of the infrared spot projected by the infrared emission reference source 8 onto a designated location inside the battery box is used as the positional reference. By projecting the infrared spot onto the designated location inside the battery box, the position of the infrared spot inside the battery box is known; based on the relative position of the spot on the infrared thermal image with the other temperature sampling points 6, and combined with the position of the infrared spot inside the battery box, the positions of the other temperature sampling points 6 inside the battery box can be obtained.

[0036] A green (or other non-red color) laser emitter 9 is installed below the infrared camera 7, forming a grid of laser lines inside the battery compartment. This grid covers all areas within the battery compartment requiring temperature sampling. The laser lines are numbered to locate the grid within the temperature sampling area, thus aiding in the positioning of each temperature sampling point 6. Furthermore, if the infrared emission reference source 8 installed inside the battery compartment is inaccurate, or in other situations, the grid of laser light emitted by the laser emitter 9 is used as a reference to calibrate the infrared emission reference source 8 or adjust its spot emission position.

[0037] In another implementation, for a battery box cooled by liquid cooling, an infrared light spot is projected onto the coolant inlet. The temperature of the infrared light spot at the coolant inlet, captured by infrared thermal imaging, is used as a temperature reference for determining the temperature of the remaining areas in the infrared thermal imaging. The temperature at the coolant inlet of the battery box is relatively stable. When the temperature sensor detects temperature fluctuations inside the battery box, it adjusts other factors such as the coolant flow rate accordingly, thereby achieving a cooling effect on the battery box while maintaining a constant coolant temperature. Therefore, for a constant coolant inlet temperature, the infrared emission reference source 8 emits an infrared light spot with a constant power, thus maintaining a relatively constant temperature of the infrared light spot projected onto the coolant inlet in the infrared thermal imaging. Therefore, the temperature of the infrared light spot projected onto the coolant inlet can be used as a temperature reference, improving the overall temperature sampling accuracy of the battery box.

[0038] After obtaining the infrared thermal image, the temperature at each location in the infrared thermal image is obtained based on the reference temperature. The temperature threshold of the area with the lowest temperature value in different regions of the infrared thermal image within the battery box is used as the set value. When a point with a temperature higher than the set value is detected in the infrared thermal image, the location of that point is determined, an alarm is triggered for that point within the battery box, and the temperature value of that point is output. The location of this point is determined based on the type of area where the temperature sampling point 6 is located within the battery box. There are three types of temperature sampling points 6: temperature sampling points 6 on individual cells, temperature sampling points 6 on the aluminum bar welding points 1 used for connecting the electrodes between individual cells, and temperature sampling points 6 on the conductive busbar bolt fastening points 2 connecting the individual cells to the battery box's positive 3 and negative 4. After obtaining the location and temperature of all temperature sampling points, the temperature sampling points 6 that exceed the set temperature threshold are identified, and an alarm is triggered for that point. Figure 3 The three color-intensity regions are derived based on the temperature characteristics of different sampling points 6. The temperature characteristics of different sampling points 6 differ because the heat output and specific heat capacity of the internal components in the three regions—the individual cells, aluminum foil, and bolt fastening points 2—are different. Therefore, different temperature warning thresholds are set for each region. The management strategies for the three regions are similar, but the management thresholds differ.

[0039] This invention uses machine vision analysis algorithms to calculate the temperature value of each grid unit within the sampling plane range, locate the maximum and minimum temperature of the same type of grid unit within the entire sampling plane, and provide the location number of the maximum and minimum value; it can also calculate the temperature rise rate of all observation points, set corresponding detection thresholds in different grid management units, and when the corresponding alarm threshold is exceeded, the accurate location of the point in the battery box can be obtained, and the temperature value of the point can be given.

[0040] The infrared camera 7 contains a photosensitive element (CCD or CMOS) that can detect infrared radiation. The photosensitive element is a rectangular plate densely covered with photosensitive dots. When infrared radiation shines on these photosensitive dots, they are activated, causing electron transitions and generating potential differences. These potential differences are converted into digital signals by an analog-to-digital converter and transmitted to a display for display, resulting in an infrared image. Analyzing the infrared image can reveal the temperature distribution and its changing patterns inside the battery box, thus enabling effective diagnosis of battery box faults.

[0041] The temperature acquisition and fire detection method of the present invention involves arranging an infrared camera 7 in one corner inside the battery box, such as... Figure 4 As shown, Figure 4 The infrared camera 7 in the upper right corner should cover all temperature sampling points 6 inside the battery box, and each temperature sampling point 6 should be matched with a grid number. An infrared emission reference source 8 is installed below the infrared camera 7 to project an infrared spot onto a designated location for the infrared camera 7 to collect, serving as the electronic reference source for temperature acquisition. If the battery box is liquid-cooled, the temperature of the coolant inlet can also be used as the temperature acquisition reference to further improve the temperature sampling accuracy. The temperature of the battery coolant inlet is controllable, and the temperature difference between the coolant inlets of each battery box is small. Therefore, the temperature of the inlet is used as the temperature reference for visual imaging. Through machine vision analysis algorithms, the temperature value of each grid unit within the sampling plane is calculated, and the maximum and minimum temperatures of the same type of grid units within the entire sampling plane are located, while the location number of the maximum and minimum values ​​is given.

[0042] The temperature acquisition and fire detection method categorizes temperature sampling points 6 into three types: the temperature of individual cells in region 1, the temperature of aluminum battery welding point 1 in region 2, and the temperature of bolt tightening point 2 in region 3. Different judgment conditions are set for different temperature sampling points 6. For example, the judgment conditions for the thermal safety risk of individual battery cells are as follows: Figure 5As shown: the X-axis represents the battery temperature coefficient, ranging from -40 to 120℃, normalized to (0,1); the Y-axis represents the battery temperature rise coefficient, with a temperature rise rate ranging from -10 to 10℃ / min, normalized to (0,1); the Z-axis represents the battery thermal safety risk value, which can be determined using an empirical formula Z = f(X,Y). When the value of Z is less than the threshold, the battery can be considered to have no thermal safety risk. The thermal safety risks of aluminum bar welding point 1 and bolt fastening point 2 can be judged using a similar method.

[0043] The process of temperature acquisition and fire detection methods is as follows: Figure 6 As shown. Scan the reference temperature on the infrared acquired image, scan the temperature on the infrared acquired image in sequence, determine the grid cell to which the temperature point belongs, and determine whether the thermal safety index (i.e., thermal safety risk value) exceeds the threshold Z = f(Ti, δTi) > Zi. If it exceeds, report the corresponding area thermal safety warning and report the temperature number and temperature value of the corresponding point; if it does not exceed, send the normal temperature value and temperature number.

[0044] The present invention has the following advantages: (1) In order to improve the positioning effect, a green (or other non-red color) laser projection is installed below the infrared camera 7 to locate each temperature sampling point 6, and the positioning is achieved by numbering the grid intersections. (2) In order to make the temperature sampling more accurate, an infrared emission reference source 8 is installed below the infrared camera 7 to project infrared light spots to the designated positions for the infrared camera 7 to collect, serving as the reference for temperature collection. (3) For battery valve, thermal runaway, and thermal diffusion faults, alarms can be set according to the characteristic safety thresholds of valve, thermal runaway, and thermal diffusion, and the captured accurate infrared images of battery valve and fire can be sent to the monitoring platform for further analysis by after-sales maintenance personnel. (4) The present invention uses infrared + machine vision method, which covers the temperature data collection area and can collect all key information. It solves the problem of existing technologies having few collection points, not being able to cover all key points, and having blind spots in monitoring. (5) The present invention uses the same temperature reference for all temperature sampling points 6, resulting in high temperature collection accuracy. It can solve the problem of large temperature sampling errors in the battery box due to different references when there are deviations between NTCs. (6) This invention addresses battery valve, thermal runaway, and thermal diffusion faults. It allows for real-time monitoring via machine vision, accurately capturing fault phenomena related to battery valves and fires, and promptly issuing alarm signals. This solves the problem of not being able to quickly determine the fire situation inside the battery box and not being able to issue alarm and fire extinguishing signals in a timely manner. (7) This invention can accurately and efficiently detect latent thermal hazards at high-voltage mechanical connection points. It solves the problem of the inability to detect changes in contact resistance and temperature at existing high-voltage connection points.

[0045] An embodiment of a battery box:

[0046] The battery box of the present invention includes battery cells, aluminum busbars, and bolt fastening points 2 for conductive busbars. An infrared camera 7, an infrared emission reference source 8, and a laser emitter 9 are installed inside the battery cells to collect temperature data and detect fires within the battery box. This enables the implementation of the battery box temperature collection and fire detection method of the present invention. The method and the battery box of the present invention have been sufficiently clearly described in the method embodiments and will not be repeated here.

Claims

1. A battery case temperature acquisition and fire detection method, characterized by, Infrared thermal imaging is acquired using an infrared camera, covering all temperature sampling points within the battery box. A grid-like laser line is formed within the battery box, with each temperature sampling point corresponding to one grid. These temperature sampling points include: temperature sampling points on each individual battery cell, temperature sampling points on the welding points of the aluminum bars connecting the electrodes of the individual batteries, and temperature sampling points on the bolt fastening points of the conductive busbars connecting the individual batteries to the positive and negative terminals of the battery box. An infrared spot of known temperature is projected from an infrared emission reference source within the infrared thermal imaging acquisition area. The temperature of this infrared spot is used as a reference temperature to determine the temperature value of the battery box at each grid location based on the infrared thermal imaging. Corresponding detection thresholds are set for different grid locations: when the thermal safety risk value of any temperature sampling point exceeds the detection threshold for that grid, the location of that point inside the battery box is obtained, and an alarm is triggered. The thermal safety risk value is calculated using an empirical formula combining a temperature coefficient and a temperature rise coefficient. The temperature coefficient is obtained by normalizing the temperature value, and the temperature rise coefficient is obtained by normalizing the temperature rise rate.

2. The battery case temperature acquisition and fire detection method according to claim 1, characterized by, The grid-like laser lines are not red.

3. The battery pack temperature acquisition and fire detection method of claim 1, wherein, Using the grid-like laser lines as a reference, the infrared emission reference source is calibrated or the position of the infrared spot emitted by the infrared emission reference source is adjusted.

4. The battery pack temperature acquisition and fire detection method of claim 1, wherein, When the battery box is liquid-cooled, the infrared light spot is projected onto the coolant inlet.

5. The battery pack temperature acquisition and fire detection method of claim 1, wherein, The infrared camera is a binocular infrared camera.

6. The battery pack temperature acquisition and fire detection method of claim 1, wherein, For the temperature sampling points on a single cell, the temperature range is -40℃ to 120℃, and the normalized temperature coefficient ranges from (0,1); the temperature rise rate ranges from -10℃ / min to 120℃ / min, and the normalized temperature rise coefficient ranges from (0,1).

7. A battery case comprising a battery cell, an aluminum busbar for connection between electrodes of the cell, and a conductive bar for connection of the cell to a total positive and a total negative of the battery case, characterized in that, It also includes an infrared camera and an infrared emission reference source installed inside the battery box; the infrared camera is used to collect infrared thermal images covering the locations of all individual cells, aluminum busbar welding points and conductive busbar bolt fastening points inside the battery box. A grid-like laser line is formed inside the battery box, with temperature sampling points corresponding one-to-one with each grid. These temperature sampling points include: temperature sampling points on each individual cell, temperature sampling points on the welding points of the aluminum bars used to connect the electrodes of the individual cells, and temperature sampling points on the bolt fastening points of the conductive busbars connecting the individual cells to the positive and negative terminals of the battery box. An infrared emission reference source projects an infrared spot of known temperature into the infrared thermal imaging acquisition area. Using the temperature of the infrared spot as a reference temperature, the temperature value of the battery box at each grid is determined based on the infrared thermal imaging. Different judgment conditions are set for different temperature sampling points: when the thermal safety risk value of the grid corresponding to any temperature sampling point exceeds the threshold at that grid, the location of that point inside the battery box is obtained, and an alarm is triggered. The thermal safety risk value is calculated using an empirical formula combining a temperature coefficient and a temperature rise coefficient. The temperature coefficient is obtained by normalizing the temperature value, and the temperature rise coefficient is obtained by normalizing the temperature rise rate.

8. The battery pack of claim 7, wherein, The grid-like laser lines are not red.

9. The battery pack of claim 7, wherein, With the grid-shaped laser line as a reference, the infrared emission reference source is calibrated or the position of the infrared light spot emitted by the infrared emission reference source is adjusted.

10. The battery pack of claim 7, wherein, When the battery box adopts a liquid cooling mode, the infrared light spot is projected at a cooling liquid inlet.

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