Method for reporting power battery thermal runaway fault

Abstract

The present invention discloses a method for reporting thermal runaway faults of power batteries. The main design concept of the present invention is that, on the one hand, by detecting the deviation changes in the single-cell voltage of the battery module in sequence and synchronously monitoring the state of the explosion-proof valve to identify thermal runaway faults, and on the other hand, by arranging flexible printed circuit boards around the battery module in a specific structure to ensure timely acquisition of battery voltage data and effectively prevent the failure of single-cell voltage acquisition when the battery cell undergoes thermal runaway, resulting in the interruption of the vehicle's power. The present invention effectively reduces the power interruption phenomenon caused by the failure of single-cell voltage acquisition during thermal runaway, and based on this, on the premise of continuously obtaining the single-cell voltage of the battery in sequence, comprehensively considering the multi-dimensional timing characteristics of the battery, thereby greatly reducing the false alarm rate and minimizing the risk of power battery faults, and further reliably protecting the safety of the vehicle and the occupants.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery protection, and particularly to a method for reporting thermal runaway faults of power batteries. Background Art

[0002] The thermal runaway protection design of power batteries is the basis for ensuring the stable operation of power battery systems. During vehicle use, if a single cell thermal runaway fault occurs, it is necessary to ensure that the vehicle does not lose power, the thermal runaway signal is accurately and timely reported, and the entire battery pack does not catch fire or explode.

[0003] The thermal runaway protection design is of great significance for reducing the losses of vehicles and personnel property and ensuring the safety of personnel lives. Therefore, an effective thermal runaway protection design that can accurately diagnose and report power battery thermal runaway faults is a functional safety item that cannot be ignored in power battery systems. Thus, the thermal runaway protection design and diagnosis method of power batteries are very important technical points in the field of new energy vehicles.

[0004] Currently, the diagnostic methods adopted in the market are mainly based on monitoring boards and thermal runaway sensors. Problem vehicles are diagnosed and screened by the pull-up level of the monitoring board and the fault flag reported by the thermal runaway sensor. However, after practice, it is found that this method has two prominent problems. On the one hand, there is a phenomenon of false fault reporting, and on the other hand, the cost is too high. Summary of the Invention

[0005] In view of the above, the present invention aims to provide a method for reporting thermal runaway faults of power batteries to solve the phenomenon of false fault reporting and reduce the cost of the battery pack.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for reporting thermal runaway faults of power batteries, which includes:

[0008] Step S1: Continuously collect the cell voltage at a preset period through a flexible printed circuit board disposed at the edge of the battery module, and continuously monitor the state of a preset explosion-proof valve; wherein, the root of the nickel strip of the flexible printed circuit board is locally weakened to prevent the current collector from warping and causing the flexible printed circuit board to tear.

[0009] Step S2: Calculate the voltage difference between the current moment and the previous moment of each cell.

[0010] Step S3: Make a fault reporting decision according to different working condition modes of the vehicle, and in combination with the voltage difference, a preset voltage difference threshold, and the state of the explosion-proof valve.

[0011] In at least one possible implementation manner, the state of the explosion-proof valve is provided by a level signal generated by the on-off action of a micro switch of the explosion-proof valve.

[0012] In at least one possible implementation, the reporting of a fault decision includes:

[0013] When the vehicle is in the discharge mode, if the current voltage difference of any one battery cell is less than or equal to a preset first voltage difference threshold, and the difference between the current voltage difference and the other voltage differences is less than or equal to the first voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, a fault is reported.

[0014] In at least one possible implementation, the reporting of a fault decision includes:

[0015] When the vehicle is in the charging mode, if the current voltage difference of any one battery cell is less than or equal to a preset second voltage difference threshold, and the difference between the current voltage difference and the other voltage differences is less than or equal to the second voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, a fault is reported.

[0016] In at least one possible implementation, the reporting of a fault decision includes:

[0017] When the vehicle is in the static state and is powered on and awakened, calculate the voltage deviation between the voltages of all battery cells at the awakening moment and the voltages of all battery cells at the previous power-off moment;

[0018] If the voltage deviation of any one battery cell is less than or equal to a preset third voltage difference threshold, and the difference between the voltage deviation and the other voltage deviations is less than or equal to the third voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, a fault is reported.

[0019] In at least one possible implementation, the reporting method further includes:

[0020] When it is detected that the battery cell voltage is in a disordered state and it is detected that the explosion-proof valve reports a low level, a fault is reported.

[0021] In at least one possible implementation, the reporting method further includes:

[0022] When it is detected that the battery cells with the minimum and maximum single-cell voltages at any moment are adjacent battery monomers, determine whether the explosion-proof valve reports a low level at the current moment;

[0023] If the explosion-proof valve reports a low level at this time, a fault is reported.

[0024] In at least one possible implementation, if it is determined that the explosion-proof valve does not report a low level at the current moment, the fault diagnosis of this pair of adjacent battery cells is ignored, and this pair of adjacent battery cells is excluded from the fault diagnosis pending detection target.

[0025] The main design concept of the present invention lies in that, on the one hand, by detecting the deviation changes of the single-cell voltage of the battery module in sequence and synchronously monitoring the state of the explosion-proof valve to identify thermal runaway faults, and on the other hand, by arranging flexible printed circuit boards around the battery module in a specific structure to ensure timely acquisition of battery voltage data and effectively prevent the failure of single-cell voltage acquisition when the battery cell undergoes thermal runaway, resulting in the interruption of the vehicle's power. The present invention effectively reduces the power interruption phenomenon caused by the failure of battery cell voltage acquisition during thermal runaway, and based on this, on the premise of continuously obtaining the battery single-cell voltage in sequence, comprehensively considering the multi-dimensional time-sequence characteristics of the battery, thereby greatly reducing the false alarm rate and minimizing the risk of power battery failures, and further reliably protecting the safety of the vehicle and its occupants. Description of the Drawings

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described below in conjunction with the drawings, where:

[0027] Figure 1 It is a flowchart of the method for reporting thermal runaway faults of power batteries provided by an embodiment of the present invention;

[0028] Figure 2 It is a structural reference diagram of the partial weakening treatment of the flexible printed circuit board provided by an embodiment of the present invention. Detailed Embodiments

[0029] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0030] Before elaborating on the present invention, the relevant technologies and their deficiencies in the current stage of the art are analyzed again, which is also the original intention and foothold of the design concept of the present invention.

[0031] Currently, for the diagnosis of thermal runaway faults of the monitoring board, after the successful initialization of the BMS, the on-off status of the monitoring board is continuously collected. The mechanism for the monitoring board to report thermal runaway faults is as follows: when the battery cell explodes and sprays, the high temperature will cause the fuse in the monitoring board to melt and break, resulting in an open circuit, and the BMS detects the fuse status and reports the fault; however, due to the complex structure of the monitoring board itself, a special mold needs to be developed and the cost is relatively high. In addition, the fuse in the monitoring board is also prone to wear and breakage during vehicle operation. Therefore, using only this method to diagnose thermal runaway is likely to cause false alarms, causing inconvenience to users and increasing the difficulty of market services at the same time.

[0032] Another way to diagnose a thermal runaway sensor is when the sensor is working in low power mode. Once the sensor detects that the aerosol concentration after the battery cell explodes and triggers the set threshold, the sensor will set the wake-up signal to a high level, and wake up the BMS through the CAN signal to report the thermal runaway fault. In the above-mentioned method of diagnosing a thermal runaway fault, the sensor is sensitive to factors such as the battery pack environment and temperature. Since the various glues currently used in the power battery PACK will interfere with the thermal runaway sensor under high temperature conditions, it will cause the thermal runaway sensor to misreport or component failure. Of course, the cost of the thermal runaway sensor is also relatively high.

[0033] Based on this analysis, the present invention proposes an embodiment of a method for reporting a thermal runaway fault of a power battery. Specifically, Figure 1 shown, including:

[0034] Step S1, the battery controller continuously collects the cell voltage according to a preset period through a flexible circuit board (FPC) provided at the edge of the battery module, and the battery management system continuously monitors the status of the preset explosion-proof valve;

[0035] Step S2, calculating the voltage difference between the current moment and the previous moment of each battery cell;

[0036] Step S3: making a fault reporting decision according to the different operating modes of the vehicle and in combination with the voltage difference, the preset voltage difference threshold and the state of the explosion-proof valve.

[0037] Among them, the root of the nickel sheet of the flexible circuit board is locally weakened, so that when the battery cell thermal runaway occurs, the collector sheet will be lifted up, causing the FPC body to tear, and then the battery controller will no longer be able to collect voltage normally, directly causing the power interruption of the whole vehicle. The local weakening treatment is an improvement at the mechanical structure level, such as Figure 2 In the example shown, the flexible circuit board 1 located at the edge of the entire battery module and avoiding the top of the battery cell 100 is connected to the current collector 2 by an open folding structure 11. The open folding structure 11 is a local weakening treatment, which has a buffering effect. When driven by a thermal runaway battery cell, there is ample mechanical buffer space to avoid the entire FPC being directly pulled.

[0038] Furthermore, the state of the explosion-proof valve is provided by a level signal generated by the on-off action of a micro switch of the explosion-proof valve.

[0039] Regarding the aforementioned decision to report a fault, here we can combine the real scenario and provide the following four solutions that can be combined and applied or implemented independently:

[0040] First, it is set that the battery controller collects the cell (single cell) voltages of all battery modules at a preset period (such as 10 s), that is, t0 = 0 s, t1 = 10 s, t2 = 20 s..., and records all the voltages at time t as V1(t)~Vn(t); then, calculate the voltage difference between the cells at time t and time t - 1, that is, record ΔV1(t) = V1(t) - V1(t - 1)..., ΔVn(t) = Vn(t) - Vn(t - 1).

[0041] (1) When the vehicle is in the discharge mode, if at a certain moment, there is a certain single cell with ΔVm(t) ≤ -20 mV, and the difference between this ΔVm(t) and all other ΔV(t) is ≤ -20 mV, and the BMS detects that the explosion-proof valve reports a high level (micro switch closed), then a fault is reported;

[0042] (2) When the vehicle is in the charging mode, if at a certain moment, there is a certain single cell with ΔVm(t) ≤ -50 mV, and the difference between this ΔVm(t) and all other ΔV(t) is ≤ -50 mV, and the BMS detects that the explosion-proof valve reports a high level (micro switch closed), then a fault is reported;

[0043] (3) When the vehicle is in the static state, when powered on and awakened (KEY ON), the battery controller calculates the voltage difference between all the cells at the awakening moment and the voltage at the previous power-off (KEY OFF). If there is a certain single cell with ΔVm(t) ≤ -20 mV, and the difference between this ΔVm(t) and all other ΔV(t) is ≤ -20 mV, and the BMS detects that the explosion-proof valve reports a high level (micro switch closed), then a fault is reported;

[0044] (4) When it is detected that the battery voltage is in a disordered state and at the same time it is detected that the explosion-proof valve reports a low level (micro switch open), then a fault is reported;

[0045] (5) In addition, it can be further explained in the present invention that the reporting method further includes that when it is detected that the battery cells with the minimum single cell voltage and the maximum single cell voltage at a certain moment are adjacent cells, and it is detected that the explosion-proof valve reports a low level (micro switch open), then a fault is reported; otherwise, no fault diagnosis is performed on this adjacent battery cell, and this adjacent battery cell is excluded from the fault diagnosis target to be detected.

[0046] In summary, the main design concept of the present invention is that, on the one hand, by detecting the deviation changes in the individual voltages of the battery modules occurring in sequence and synchronously monitoring the state of the explosion-proof valve to identify thermal runaway faults, and on the other hand, by arranging flexible printed circuit boards around the battery module in a specific structure to ensure timely acquisition of battery voltage data and effectively prevent the failure of individual voltage acquisition when a battery cell undergoes thermal runaway, resulting in the interruption of the vehicle's power. The present invention effectively reduces the power interruption phenomenon caused by the failure of battery cell voltage acquisition during thermal runaway, and based on this, on the premise of continuously obtaining the individual battery voltages in sequence, comprehensively considering the multi-dimensional sequential characteristics of the battery, thereby greatly reducing the false alarm rate and minimizing the risk of power battery failure, and further reliably protecting the safety of the vehicle and the occupants.

[0047] In the embodiments of the present invention, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent the situation where A exists alone, A and B exist simultaneously, or B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one of the following" and its similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0048] The structure, features, and effects of the present invention have been described in detail based on the embodiments shown in the drawings above. However, the above are only the preferred embodiments of the present invention. It should be noted that for the technical features involved in the above embodiments and their preferred modes, those skilled in the art can reasonably combine and match them into various equivalent solutions without departing from or changing the design concept and technical effects of the present invention; therefore, the scope of implementation of the present invention is not limited by the drawings shown. Any changes made in accordance with the concept of the present invention or modifications to equivalent embodiments with equivalent changes that still do not exceed the spirit covered by the description and the drawings should be within the protection scope of the present invention.

Claims

1. A method for reporting thermal runaway faults of power batteries, characterized in that, it includes: Step S1: Continuously collect the voltage of the battery cells at a preset period through a flexible circuit board provided at the edge of the battery module, and continuously monitor the state of a preset explosion-proof valve; wherein, the root of the nickel strip of the flexible circuit board is locally weakened to prevent the current collector from warping and causing the flexible circuit board to tear; Step S2: Calculate the voltage difference between the current moment and the previous moment of each battery cell; Step S3: Make a decision on reporting faults according to different working condition modes of the vehicle, and in combination with the voltage difference, a preset voltage difference threshold, and the state of the explosion-proof valve; The reporting method further includes: When it is detected that the battery cells with the minimum and maximum single-cell voltages at any moment are adjacent battery monomers, it is judged whether the explosion-proof valve reports a low level at the current moment: If the explosion-proof valve reports a low level at this time, report the fault; If the explosion-proof valve does not report a low level at this time, ignore the fault diagnosis of this pair of adjacent battery cells, and exclude this pair of adjacent battery cells from the objects to be detected for fault diagnosis.

2. The method for reporting thermal runaway faults of power batteries according to claim 1, characterized in that, the state of the explosion-proof valve is provided by a level signal generated by the on-off action of the microswitch of the explosion-proof valve.

3. The method for reporting thermal runaway faults of power batteries according to claim 1, characterized in that, the making a decision on reporting faults includes: When the vehicle is in the discharge mode, if the current voltage difference of any battery cell is less than or equal to a preset first voltage difference threshold, and the difference between the current voltage difference and the other voltage differences is less than or equal to the first voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, report the fault.

4. The method for reporting thermal runaway faults of power batteries according to claim 1, characterized in that, the making a decision on reporting faults includes: When the vehicle is in the charging mode, if the current voltage difference of any battery cell is less than or equal to a preset second voltage difference threshold, and the difference between the current voltage difference and the other voltage differences is less than or equal to the second voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, report the fault.

5. The method for reporting thermal runaway faults of power batteries according to claim 1, characterized in that, the making a decision on reporting faults includes: When the vehicle is in the static state and is powered on and awakened, calculate the voltage deviation between the voltages of all battery cells at the awakening moment and the voltages of all battery cells at the previous power-off; If the voltage deviation of any battery cell is less than or equal to a preset third voltage difference threshold, and the difference between the voltage deviation and the other voltage deviations is less than or equal to the third voltage difference threshold, and it is detected that the explosion-proof valve reports a high level, report the fault.

6. The method for reporting thermal runaway faults of power batteries according to any one of claims 1 to 5, characterized in that, the reporting method further includes: When it is detected that the voltage of the battery cells is in a disordered state and it is detected that the explosion-proof valve reports a low level, report the fault.

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