Battery pack nitrogen protection system and control method

Abstract

This invention discloses a nitrogen protection system and control method for a battery pack. The system includes an air compressor, a filter and dryer, a heating device, and a molecular membrane separator connected in sequence. The output of the molecular membrane separator is connected to a gas supply pipeline. An electronic expansion valve and a gas detection unit are installed on the gas supply pipeline. The gas detection unit detects at least the oxygen concentration. The gas supply pipeline connects to corresponding battery packs via several battery pack sub-valve units. The main controller adjusts the opening of the electronic expansion valve based on the oxygen concentration feedback from the gas detection unit, ensuring the output nitrogen concentration is higher than a set value. It also controls the opening and closing of each sub-valve unit based on the pressure difference between the battery pack's internal pressure and atmospheric pressure to perform gas filling. This invention eliminates the need for a gas storage tank, pressure reducing valve, and flow limiting valve. It utilizes the electronic expansion valve and gas parameter feedback to achieve real-time and precise adjustment of nitrogen concentration and pressure. The structure is simplified, the response is fast, and it possesses functions for airtightness detection, gas replacement, and fault diagnosis, significantly improving the safety protection level of the battery pack.

Description

Technical Field

[0001] This invention relates to the field of power battery safety protection technology, and in particular to a battery pack nitrogen protection system and control method. Background Technology

[0002] With the increasing popularity of new energy vehicles, the thermal runaway safety issue of power batteries has received growing attention. Injecting high-purity nitrogen into the battery to create a dry, oxygen-free environment is an effective technical approach to reduce the risk of thermal runaway.

[0003] Existing battery pack nitrogen protection systems generally include a nitrogen generation module, a nitrogen storage tank, and mechanical regulating valves such as pressure reducing valves and flow limiting valves. For example, patent document CN115337571A discloses a battery pack nitrogen protection system that generates nitrogen through an air compressor, a dryer filter, a heating module, and a nitrogen separation module, and stores it in a nitrogen storage tank. An electromagnetic pressure detection module and a pressure / flow regulating module are installed on the gas supply pipeline, and pressure reducing valves and flow limiting valves are used to control the charging of the battery pack. Another patent document, CN114889428A, focuses on controlling the activation and power supply timing of the nitrogen protection system at the vehicle level.

[0004] The existing solutions generally have the following shortcomings: relying on nitrogen storage tanks as buffers results in large system size, limited layout, and high cost; using pressure reducing valves and flow limiting valves for open-loop mechanical regulation of pressure and flow results in slow response speed, making it difficult to control accurately in real time according to operating conditions, and the stability of nitrogen concentration and supply pressure is poor when system parameters change; in addition, the existing systems have relatively simple functions and lack comprehensive maintenance functions such as airtightness detection and gas replacement. Summary of the Invention

[0005] To address the existing problems, this invention provides a battery pack nitrogen protection system and its control method, the specific solution of which is as follows:

[0006] A battery pack nitrogen protection system, comprising:

[0007] The nitrogen generation circuit includes an air compressor, a filter and dryer, a heating device and a molecular membrane separator connected in sequence, with the output end of the molecular membrane separator connected to the gas supply pipeline;

[0008] An electronic expansion valve and a gas detection unit are installed on the gas supply pipeline. The gas detection unit is used to detect the oxygen concentration and pressure of the gas in the gas supply pipeline.

[0009] Multiple battery pack sub-valve, also known as battery box valve, with the input end of each battery pack sub-valve connected to the air supply pipeline and the output end used to connect to the corresponding battery pack;

[0010] The main controller is connected to the electronic expansion valve, the gas detection unit, and the compartment valves of each battery pack, respectively.

[0011] The main controller adjusts the opening of the electronic expansion valve according to the oxygen concentration detected by the gas detection unit, so that the nitrogen concentration output by the gas supply pipeline is greater than the preset concentration threshold; and controls the opening and closing of the corresponding battery pack sub-valve according to the difference between the internal pressure of each battery pack and the atmospheric pressure, so as to charge the battery pack with nitrogen.

[0012] Preferably, the main controller is further configured to adjust the opening of the electronic expansion valve according to the gas supply line pressure detected by the gas detection unit, so as to maintain the gas supply line pressure within a preset pressure range.

[0013] Preferably, it also includes an exhaust valve, which is installed on an exhaust pipe connected to the gas supply pipe; when the main controller detects that the oxygen concentration fed back by the gas detection unit has not reached the preset concentration threshold, it controls the exhaust valve to open and discharge the unqualified gas.

[0014] Preferably, the main controller is also used to perform airtightness detection: control all battery pack compartment valves to open, fill the battery pack with nitrogen through the air supply pipeline to a first preset pressure and then close the electronic expansion valve, and monitor the decrease value of the internal pressure of the battery pack within a set time to determine the airtightness.

[0015] Preferably, when the system airtightness test fails, the main controller sequentially performs a single-pack airtightness test on each battery pack.

[0016] Preferably, the main controller is also used to perform gas replacement when the triggering conditions are met: open all battery pack compartment valves and electronic expansion valves, fill the battery pack with nitrogen to a second preset pressure and maintain it for a predetermined time, then open the exhaust valve to release pressure and complete the gas replacement.

[0017] This invention also discloses a battery pack nitrogen protection control method, applied to the system described in any of the above claims, comprising:

[0018] S1. Start the nitrogen generation process, obtain the oxygen concentration in the gas supply pipeline through the gas detection unit, and adjust the opening of the electronic expansion valve according to the oxygen concentration so that the nitrogen concentration of the gas output by the molecular membrane separator is greater than the preset concentration threshold.

[0019] S2. After the nitrogen concentration is qualified, the internal pressure of each battery pack is periodically checked in turn. For battery packs whose internal pressure difference with atmospheric pressure is less than the lower limit threshold, the corresponding battery pack sub-valve is opened to charge the battery pack with nitrogen, and the sub-valve is closed when the difference reaches the upper limit threshold.

[0020] Preferably, step S1 further includes:

[0021] S11. Detect the pressure in the gas supply line and adjust the opening of the electronic expansion valve according to the pressure to maintain the gas supply line pressure within a preset pressure range; wherein, the main controller adjusts the electronic expansion valve by superimposing the opening adjustment amount obtained based on the oxygen concentration and the opening adjustment amount obtained based on the gas supply line pressure.

[0022] S12. The main controller times the nitrogen generation process. When the oxygen concentration fed back by the gas detection unit fails to reach the preset concentration threshold within a period of time exceeding the set duration, the main controller outputs a fault signal and closes the electronic expansion valve to terminate the nitrogen generation process.

[0023] Preferably, a battery pack nitrogen protection control method further includes step S3: after receiving an airtightness detection trigger command, performing an airtightness detection, wherein the airtightness detection includes: opening all battery pack compartment valves, charging each battery pack with nitrogen through the gas supply pipeline to a first preset gauge pressure, closing the electronic expansion valve and keeping the battery compartment valves open, monitoring the pressure drop value inside the battery pack within a set time, and determining that the airtightness is qualified if the drop value is less than the preset value, otherwise determining that the airtightness is unqualified.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention eliminates the nitrogen storage tank, pressure reducing valve, and flow limiting valve, using an electronic expansion valve as a unified flow and pressure regulating actuator. Combined with real-time oxygen concentration and pressure signals from a gas detection unit, it forms a closed-loop control system, enabling precise and rapid adjustment of nitrogen concentration and supply pressure. This significantly simplifies the system structure, reducing size and cost. Furthermore, the main controller integrates functions such as alternating filling, airtightness detection, gas replacement, and fault self-diagnosis, comprehensively enhancing the battery pack's safety and maintenance convenience. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0028] Figure 2 This invention relates to the battery pack pressure detection and inflation process. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A battery pack nitrogen protection system, such as Figure 1 As shown, the system's workflow is as follows: An air compressor pressurizes the air, which is then filtered under the control of the main unit's valves. The main unit then heats the filtered air and separates high-purity nitrogen through a molecular membrane. The main controller periodically opens the battery pack's compartment valves in turn. Once the internal pressure of the battery pack balances with the pipeline pressure, this pipeline pressure becomes the battery pack pressure. Inflation begins when the pressure is below a threshold and stops when it exceeds the threshold. The system also features airtightness detection and fault self-diagnosis functions.

[0031] Example 1:

[0032] A battery pack nitrogen protection system, comprising:

[0033] The nitrogen protection system for the battery pack in this embodiment mainly includes: an air compressor, a filter and dryer, a heating device, a molecular membrane separator, an electronic expansion valve, a gas detection unit, multiple battery compartment valves, an exhaust valve, and a main controller. The air compressor, filter and dryer, heating device, and molecular membrane separator are connected sequentially via pipelines. The output end of the molecular membrane separator is connected to the air supply pipeline. An electronic expansion valve and a gas detection unit are installed on the air supply pipeline; multiple branches extend from the end of the air supply pipeline, each branch connecting to a battery pack via a battery compartment valve. An exhaust valve is located on the exhaust pipeline, which is connected to the air supply pipeline. The main controller is connected to the electronic expansion valve, the gas detection unit, each battery compartment valve, and the exhaust valve via signal lines for data acquisition and control command output.

[0034] The air compression unit can use the vehicle's own air compressor or an external oil-free air compressor to provide compressed air. The filtration and drying unit has multi-stage drying and precision filtration functions, capable of removing moisture and fine particles from the compressed air. The heating unit heats the filtered air to a suitable temperature, improving the efficiency of the molecular membrane separation. The molecular membrane separation unit uses a polymer membrane to separate nitrogen and oxygen in the air, outputting high-concentration nitrogen. This system does not have a nitrogen storage tank; the nitrogen generated by the molecular membrane separation unit 4 directly enters the air supply pipeline, and is regulated in real time by an electronic expansion valve.

[0035] The gas detection unit integrates oxygen, pressure, temperature, and humidity sensors, simultaneously detecting the oxygen concentration, pressure, temperature, and humidity of the gas in the gas supply pipeline. The main controller reads these parameters and adjusts the opening of the electronic expansion valve primarily based on oxygen concentration: when the oxygen concentration is above 2%, the opening of the electronic expansion valve is reduced to increase the gas residence time within the molecular membrane, thereby increasing the nitrogen concentration; when the oxygen concentration is below 2%, the opening is appropriately increased to increase the gas production flow rate, ensuring a nitrogen concentration greater than 98% while maintaining sufficient production output. Furthermore, the main controller monitors the gas supply pipeline pressure, increasing the opening of the electronic expansion valve when the pressure is below 115 kPa and decreasing it when it is above 115 kPa, maintaining the pressure within a reasonable range and preventing overpressure or insufficient flow. Through dual-parameter closed-loop regulation of oxygen concentration and pressure, the pressure reducing valve and flow limiting valve required in traditional solutions are eliminated.

[0036] During the inflation phase, the main controller periodically checks the internal pressure of each battery pack. The detection method is as follows: the electronic expansion valve is closed, the battery compartment valve of the battery pack under test is opened, and after the pressure in the gas supply line and the internal pressure of the battery pack are balanced, the pressure value is read by the pressure sensor in the gas detection unit. This pressure value represents the internal pressure of the battery pack. The main controller calculates the difference between this pressure and atmospheric pressure. If the difference is less than 150 Pa, the nitrogen generation process is started. After the nitrogen is qualified, the compartment valve of the battery pack is opened for inflation. When the pressure difference rises to 800 Pa, the compartment valve is closed, completing the inflation of this battery pack, and then the process begins for the next battery pack. All battery packs are executed in a cyclical manner to ensure that the battery packs are always under a slightly positive pressure nitrogen environment.

[0037] To ensure the quality of nitrogen supplied to the battery pack, the system performs a purging process at the initial stage of nitrogen generation: the main controller first opens the vent valve to release substandard gas into the atmosphere, while simultaneously monitoring the oxygen concentration. Once the oxygen concentration drops below the preset threshold and the humidity meets the requirements, the vent valve is closed, and the battery pack is then charged. If the nitrogen generation fails to meet the standard after 20 minutes of continuous operation, the main controller records the fault and stops the current process, waiting to retry in the next cycle.

[0038] The system also has a complete airtight detection function. It can enter the airtight detection mode in response to an external trigger instruction. The airtight detection process of the system is as follows: The main controller opens all the battery pack sub-box valves, controls the nitrogen production and fills nitrogen into the battery pack until the gauge pressure is not less than 1.5 kPa, then closes the electronic expansion valve and keeps the battery sub-box valves open, starts timing, monitors the pressure drop value after 2 minutes. If the drop value is less than 1 kPa, it is determined that the airtightness is qualified, otherwise it is unqualified. If the airtight detection of the system is unqualified, it can automatically enter the single-box airtight detection: sequentially perform the above pressurization and pressure holding tests on each battery pack separately to locate the leaking battery pack. If necessary, all the battery sub-box valves can also be closed, and only the air supply pipeline is subjected to the pressure holding test to check whether there is leakage in the main unit and the pipeline.

[0039] The gas replacement function is used to completely replace the original gas in the battery pack after the vehicle has been stationary for a long time or during maintenance. After receiving the trigger instruction, the main controller opens all the battery pack sub-box valves, fills qualified nitrogen and keeps the gauge pressure not less than 1.5 kPa for 10 minutes, and then opens the exhaust valve to release the pressure below 800 Pa, completing the replacement and automatically performing the air leakage detection. The trigger conditions for this function can include automatic judgment logics such as the vehicle being parked for more than 5 days.

[0040] The main controller also undertakes the task of fault self-diagnosis, including detecting abnormal temperature of the heating device, oxygen sensor failure, battery pack air leakage (too low pressure rise rate during the inflation process), and air leakage in the main chassis, etc., and can report the status information to the vehicle controller and the cloud platform through the CAN bus.

[0041] Among them, the above gas replacement needs to perform the "battery pack air leakage" and "system airtight detection" processes simultaneously.

[0042] The airtight replacement should be a trigger function (non-automatic detection), generally carried out at the time of factory shipment or during repair and maintenance. The airtight replacement is not restricted by the 20-minute inflation duration.

[0043] There is a function to save the last power-off time (constantly update and save the latest received time message). When powering on again, calculate the parking duration.

[0044] It is triggered once when the parking duration exceeds 5 days. The RTC stores once every 30 minutes.

[0045] Specifically, the functions of each component in the system are as follows:

[0046] 1. Filter and drying device:

[0047] The filter and drying device is an air filter. This air filter has a drying function, adopts multi-stage drying and automatic drainage functions, and can significantly reduce the humidity of the compressed air; at the same time, it can filter tiny solid and liquid micro-particles.

[0048] 2. Nozzle:

[0049] The nozzle is the nitrogen injection port for the battery pack and has waterproof and breathable functions.

[0050] 3. Battery pack compartment valve:

[0051] The battery pack compartment valve (i.e., the battery box valve) controls the opening and closing of the air supply line between the internal environment of the battery pack and the air supply line.

[0052] 4. Main valve:

[0053] The main valve is the master control valve for the air input, located on the pipeline between the air filter and the air compressor. When closed, it disconnects the connection to the air source.

[0054] 5. Air heating unit:

[0055] The air heating component preheats the compressed air entering the molecular membrane to 50-60°C, thereby increasing the nitrogen concentration produced by the molecular membrane. It includes a housing (cavity), heating element (membrane), NTC temperature sensor, and pipe connectors.

[0056] 6. Molecular membrane separation device:

[0057] The molecular membrane is an important component of the system, which functions to separate nitrogen and oxygen in the air. It includes a molecular membrane, a heating membrane, insulation cotton, an NTC temperature sensor, and pipe fittings.

[0058] 7. Electronic expansion valve:

[0059] The electronic expansion valve is an inflatable on / off valve that also has the functions of adjusting opening degree and flow rate. It can provide precise flow control and is widely used in refrigeration, air conditioning and heat pump applications. It achieves precise, efficient and energy-saving flow control through an electromagnetic stepper motor.

[0060] 8. Heating control power relay:

[0061] Air heating and film heating require significant power. To reduce the main control current requirements, a main control relay is used, which controls the operation of the heating film. Automotive-grade relays can be selected, or the relay can be placed on the main control board for direct output.

[0062] The heating logic of the air heating component and the molecular membrane separation device is the same. After the main controller is powered on, it collects the temperature of the two heating components. When the temperature is below 5 degrees, the heating membrane starts to heat up, and when the temperature is above 15 degrees, it stops heating up.

[0063] 8. Exhaust valve:

[0064] When the nitrogen quality is substandard, the exhaust valve is opened to release the substandard gas until the nitrogen quality is up to standard, at which point the valve is closed, and the battery pack is then refilled.

[0065] 9. Main unit waterproof and breathable valve

[0066] The main unit's waterproof and breathable valve is used to balance the pressure between the inside of the main unit and the atmosphere, ensuring that the pressure is the same, while also providing a waterproof function.

[0067] 10. Main unit case:

[0068] The components are installed inside the main unit chassis to provide support and protection. They are made using steel plate bending and welding processes, and the surface is powder coated.

[0069] 11. Gas detection unit:

[0070] The gas detection unit, also known as a pipeline gas detector, is used to measure the concentration, humidity, and temperature of nitrogen gas filling the battery pack, as well as the internal pressure of the pipeline. It mainly consists of a housing, pipe joints, an oxygen sensor, and a pressure assembly, which includes both a temperature and humidity sensor and a pressure sensor.

[0071] 12. Main Controller

[0072] The main controller is the system's master controller, collecting signals such as temperature, voltage, and detector data, supplying power to the detectors, and issuing control signals based on logic. It mainly consists of a housing, PCBA, and connectors.

[0073] Example 2:

[0074] This invention also discloses a method for controlling nitrogen protection in a battery pack. It includes the following steps:

[0075] S1. Start the nitrogen generation process, obtain the oxygen concentration in the gas supply pipeline through the gas detection unit, and adjust the opening of the electronic expansion valve according to the oxygen concentration to make the nitrogen concentration of the gas output by the molecular membrane separator greater than the preset concentration threshold; step S1 also includes:

[0076] S11. Detect the pressure in the gas supply line and adjust the opening of the electronic expansion valve according to the pressure to maintain the gas supply line pressure within a preset pressure range; wherein, the main controller adjusts the electronic expansion valve by superimposing the opening adjustment amount obtained based on the oxygen concentration and the opening adjustment amount obtained based on the gas supply line pressure.

[0077] S12. The main controller times the nitrogen generation process. When the oxygen concentration fed back by the gas detection unit fails to reach the preset concentration threshold within a period of time exceeding the set duration, the main controller outputs a fault signal and closes the electronic expansion valve to terminate the nitrogen generation process.

[0078] The nitrogen generation logic of this invention is as follows:

[0079] When the air heating temperature is greater than 50 degrees, first open the exhaust valve, then open the inflation valve, and finally open the main valve; continuously detect the oxygen concentration, temperature, and humidity through the 485 bus until the nitrogen concentration is higher than 95% and the humidity is lower than 20%. At this time, the nitrogen is qualified and the battery pack can be inflated. If the nitrogen production process lasts for 20 minutes and the nitrogen quality is always unqualified, report a fault and terminate this process; it can be restarted in the next cycle. Since the nitrogen gas storage tank is cancelled, the nitrogen production process generally does not work alone but serves as a pre-process for other processes, such as "battery pack inflation, airtight detection", etc.

[0080] S2. After the nitrogen concentration is qualified, periodically and alternately detect the internal pressure of each battery pack. For a battery pack with the difference between the internal pressure and the atmospheric pressure less than the lower threshold, open its corresponding battery pack sub-box valve to fill the battery pack with nitrogen, and close the sub-box valve when the difference reaches the upper threshold.

[0081] Specifically, the battery pressure detection and inflation process is as Figure 2 shown:

[0082] The system opens the battery pack sub-box valve (at this time, the main valve, exhaust valve, and inflation valve are closed) every 2 hours, waits for 1 minute for the pressure in the battery pack and the pipeline to balance, and the pipeline pressure at this time is the battery pack pressure; when the difference between this pressure and the atmospheric pressure ≤ 150 pa, inflate the battery pack, and stop inflating when the pressure difference ≥ 800 pa.

[0083] The "nitrogen production process" needs to be carried out before inflation, and inflation is only carried out after the nitrogen is qualified.

[0084] After the detection and inflation (if necessary) of the current battery pack are completed, the detection and inflation of the next battery pack are carried out, and the cycle is carried out alternately.

[0085] Within 2 hours of the system, the cumulative inflation duration (including the nitrogen production process) does not exceed 20 minutes. When the cumulative inflation duration reaches 20 minutes, stop further inflation and continue the unfinished part in the next cycle. All thresholds and condition judgments should be judged multiple times (or take the average value) to prevent misjudgment; when the pressure sensor and oxygen sensor fail, no battery pack will be inflated.

[0086] A nitrogen protection control method for a battery pack further includes step S3: perform an airtight detection after receiving an airtight detection trigger instruction. The airtight detection includes: opening all battery pack sub-box valves, filling each battery pack with nitrogen through the air supply pipeline to the first preset gauge pressure, closing the electronic expansion valve and keeping the battery sub-box valve open, monitoring the pressure drop value inside the battery pack within the set time, and if the drop value is less than the preset value, it is determined that the airtightness is qualified, otherwise it is determined that the airtightness is unqualified.

[0087] Specifically, the system opens all the battery pack valves, fills the battery packs with nitrogen gas having a qualified pressure not less than 1.5 kPa (gauge pressure), closes the main valve and the inflation valve, keeps the sectional valves open, and starts timing. After 2 minutes, if the pressure drop is less than 1 kPa, it indicates that the airtightness is qualified; otherwise, it is unqualified.

[0088] Single - box airtightness detection:

[0089] When the system airtightness detection is unqualified, single - pack airtightness detection is carried out. Nitrogen gas having a qualified pressure not less than 1.5 kPa (gauge pressure) is sequentially filled into the battery packs in turn. The main valve and the inflation valve are closed, the sectional valves are kept open, and timing is started. After 2 minutes, if the pressure drop is less than 1 kPa, it indicates that the airtightness is qualified; otherwise, it is unqualified. After the detection of this battery pack is completed, the next battery pack is tested.

[0090] Main unit airtightness detection:

[0091] If the single - pack detection is also unqualified, considering that the main unit may leak air, all the battery pack valves are closed, nitrogen gas not less than 1.5 kPa (gauge pressure) is filled into the pipeline, the main valve is closed, and timing is started. After 2 minutes, if the pressure drop is less than 1 kPa, it indicates that the airtightness is qualified; otherwise, it is unqualified

[0092] The airtightness detection should be a trigger detection (not an automatic detection). For the three detection modes, three independent trigger instructions can be designed, which are generally carried out at the time of factory shipment or during maintenance. The airtightness detection is not restricted by the 20 - minute inflation duration.

[0093] This invention also has a function of fault self - detection: <000019�>

[0094] 1. Fault judgment of NTC temperature detection for the heating function in the molecular membrane separation component:

[0095] If the NTC temperature deviates from the reasonable normal range, it is judged as a fault, tentatively defined as being lower than - 45 degrees or higher than + 95 degrees.

[0096] 2. Oxygen sensor fault

[0097] When the oxygen sensor is offline or has a fault code, the reported fault code can distinguish the fault mode, which is specifically described in the communication protocol.

[0098] 3. Leakage fault

[0099] Battery pack leakage: <00,00208>During the inflation process of the battery pack, if the pressure rise is less than 200 Pa in 1 minute, it is judged that the battery pack leaks.

[0101] Main unit leakage:

[0102] The host unit has an IP67 protection rating and is basically airtight. The current atmospheric pressure is recorded after each power-on. If the atmospheric pressure rises by more than 12 kPa (at an altitude of 1 km, tentative) within 30 minutes, or the atmospheric pressure exceeds 110 kPa, the host unit is considered to be leaking internally.

[0103] This invention also features maintenance reminders, debugging, after-sales service, and preset maintenance functions:

[0104] The system will remind you to perform maintenance once it has accumulated one year of inflation time or has undergone 110 gas replacements. The earlier of these dates will be used to remind you to perform maintenance.

[0105] It has functions for setting and reading maintenance dates; after the maintenance date is updated, the cumulative inflation time and number of gas replacements are reset to zero and re-accumulated.

[0106] It has the function of setting and reading device serial numbers.

[0107] It has software and hardware version reading capabilities.

[0108] It has battery pack inflation threshold, stop inflation threshold setting, and reading functions.

[0109] It has an online upgrade function.

[0110] It has an automatic encoding function for the detector.

[0111] The system defaults to normal operating mode upon power-up, but can enter debug mode via commands. In debug mode, all outputs are no longer automatically controlled, but each output port can be controlled via commands. In both normal and debug modes, all detection parameters and system status (including but not limited to the status of each valve, concentration, pressure, temperature, etc., with the battery expansion valve status) must be uploaded.

[0112] This invention eliminates the nitrogen storage tank, pressure reducing valve, and flow limiting valve, using an electronic expansion valve as a unified flow and pressure regulating actuator. Combined with real-time oxygen concentration and pressure signals from a gas detection unit, it forms a closed-loop control system, enabling precise and rapid adjustment of nitrogen concentration and supply pressure. This significantly simplifies the system structure, reducing size and cost. Furthermore, the main controller integrates functions such as alternating filling, airtightness detection, gas replacement, and fault self-diagnosis, comprehensively enhancing the battery pack's safety and maintenance convenience.

[0113] Example 3:

[0114] Embodiments 1 and 2 of this invention involve filling the battery pack with nitrogen gas for active protection. This application can also provide passive protection.

[0115] like Figure 1In emergency situations such as battery pack malfunction and fire, the main controller receives signals from sensors within the battery pack, opens the valve corresponding to the faulty battery pack, and simultaneously sends a control signal to activate the suppression device. The medium generated in the suppression device is preferably a fire extinguishing medium. Once activated, the generated medium flows along the opened valve into the faulty battery pack to eliminate the emergency malfunction.

[0116] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps are described above in a generalized manner in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the invention.

[0117] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery pack nitrogen protection system, characterized by, include: The nitrogen generation circuit includes an air compressor, a filter and dryer, a heating device and a molecular membrane separator connected in sequence, with the output end of the molecular membrane separator connected to the gas supply pipeline; An electronic expansion valve and a gas detection unit are installed on the gas supply pipeline. The gas detection unit is used to detect the oxygen concentration and pressure of the gas in the gas supply pipeline. Multiple battery pack sub-valve, also known as battery box valve, with the input end of each battery pack sub-valve connected to the air supply pipeline and the output end used to connect to the corresponding battery pack; The main controller is connected to the electronic expansion valve, the gas detection unit, and the compartment valves of each battery pack, respectively. The main controller adjusts the opening of the electronic expansion valve according to the oxygen concentration detected by the gas detection unit, so that the nitrogen concentration output by the gas supply pipeline is greater than the preset concentration threshold; and controls the opening and closing of the corresponding battery pack sub-valve according to the difference between the internal pressure of each battery pack and the atmospheric pressure, so as to charge the battery pack with nitrogen.

2. The battery pack nitrogen protection system of claim 1, wherein: The main controller is also used to adjust the opening of the electronic expansion valve according to the gas supply line pressure detected by the gas detection unit, so as to maintain the gas supply line pressure within a preset pressure range.

3. The battery pack nitrogen protection system according to claim 1, characterized in that: It also includes an exhaust valve, which is installed on the exhaust pipe connected to the gas supply pipe; when the main controller detects that the oxygen concentration fed back by the gas detection unit has not reached the preset concentration threshold, it controls the exhaust valve to open and discharge the unqualified gas.

4. The battery pack nitrogen protection system according to claim 1, characterized in that, The main controller is also used to perform airtightness detection: control all battery pack compartment valves to open, fill the battery pack with nitrogen through the air supply line to the first preset pressure and then close the electronic expansion valve, and monitor the decrease value of the internal pressure of the battery pack within a set time to determine the airtightness.

5. The battery pack nitrogen protection system according to claim 4, characterized in that: When the system airtightness test fails, the main controller sequentially performs a single-pack airtightness test on each battery pack.

6. The battery pack nitrogen protection system according to claim 1, characterized in that, The main controller is also used to perform gas replacement when the triggering conditions are met: open all battery pack compartment valves and electronic expansion valves, fill the battery pack with nitrogen to the second preset pressure and maintain it for a predetermined time, then open the exhaust valve to release pressure and complete the gas replacement.

7. A method for controlling nitrogen protection in a battery pack, applied to the system described in any one of claims 1 to 6, characterized in that, include: S1. Start the nitrogen generation process, obtain the oxygen concentration in the gas supply pipeline through the gas detection unit, and adjust the opening of the electronic expansion valve according to the oxygen concentration so that the nitrogen concentration of the gas output by the molecular membrane separator is greater than the preset concentration threshold. S2. After the nitrogen concentration is qualified, the internal pressure of each battery pack is periodically checked in turn. For battery packs whose internal pressure difference with atmospheric pressure is less than the lower limit threshold, the corresponding battery pack sub-valve is opened to charge the battery pack with nitrogen, and the sub-valve is closed when the difference reaches the upper limit threshold.

8. The battery pack nitrogen protection control method according to claim 7, characterized in that, Step S1 also includes: S11. Detect the pressure in the gas supply line and adjust the opening of the electronic expansion valve according to the pressure to maintain the gas supply line pressure within a preset pressure range; wherein, the main controller adjusts the electronic expansion valve by superimposing the opening adjustment amount obtained based on the oxygen concentration and the opening adjustment amount obtained based on the gas supply line pressure. S12. The main controller times the nitrogen generation process. When the oxygen concentration fed back by the gas detection unit fails to reach the preset concentration threshold within a period of time exceeding the set duration, the main controller outputs a fault signal and closes the electronic expansion valve to terminate the nitrogen generation process.

9. The battery pack nitrogen protection control method according to claim 7 or 8, characterized in that, It also includes step S3: after receiving the air tightness test trigger command, perform the air tightness test. The air tightness test includes: opening all battery pack compartment valves, charging each battery pack with nitrogen through the air supply pipeline to the first preset gauge pressure, closing the electronic expansion valve and keeping the battery compartment valve open, monitoring the pressure drop value inside the battery pack within a set time, and if the drop value is less than the preset value, the air tightness is determined to be qualified; otherwise, the air tightness is determined to be unqualified.

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