Battery pack safety monitoring system

Abstract

The invention discloses a battery pack safety monitoring system, and relates to the technical field of multi-parallel battery pack monitoring, and the system comprises a battery pack voltage and current monitoring module which is responsible for monitoring the voltage and current states of a battery pack in real time; the temperature rise monitoring and calculating module is used for monitoring and judging the temperature of the single battery; the single battery parallel module forms a power supply by connecting a plurality of single battery cells in series and in parallel through conductive connecting pieces; the BMS safety monitoring module performs data communication with other modules, monitors the working state of the battery pack in real time, and timely discovers and diagnoses faults. Compared with traditional battery pack overall temperature monitoring, the scheme has the advantages that besides basic battery pack voltage and current monitoring, a battery monomer sensor and a monomer temperature rise and inter-monomer temperature difference calculation module are additionally arranged, and battery monomer temperature data are recorded and judged in time. The method can be used for carrying out safety control on various series-parallel connection modes such as parallel connection and series connection, series connection and parallel connection, modular series-parallel connection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of battery pack safety monitoring, and in particular to a battery pack safety monitoring system. Background Art

[0002] Whether it is during the manufacturing process of the battery (differences in process or raw material), or during the installation and use of the battery pack (ambient temperature or charge and discharge depth, battery connection, etc.), the battery inconsistency will be more or less caused. The root cause is the difference in the actual capacity and internal resistance of each battery cell, which can be more intuitively presented to a certain extent from the battery voltage data.

[0003] In addition to causing degradation of battery performance, battery inconsistency also creates great difficulties for detecting battery pack parameter information. In parallel modules, due to the limited space and cost of multi-parallel battery packs and the resistance of the connecting piece itself, it is almost impossible to measure the voltage across each parallel cell. When single cells are connected in parallel, theoretically, the inconsistency will be reflected through the branch current of the parallel resistance. However, due to the volume, mass and cost requirements of the parallel battery pack module itself, it is not realistic to install a Hall sensor for each single branch to measure the branch current. In addition, due to the unmeasurable voltage of the single cell and the inconsistency of the internal resistance of the battery, the information about the battery status that can be obtained by measuring the branch current is very limited. When the parallel battery pack is only regarded as a large-capacity single cell for control, if a single cell is overcharged / over-discharged during charging or operation, but the total current or total voltage is not fully detected, this hidden danger will be overlooked. The next time it is used, the battery that has already failed will be further overcharged / over-discharged, and the hidden dangers of failure will gradually accumulate. Although the battery cells themselves have a small capacity and pose little safety risk, once combustion or explosion occurs, it will trigger a chain reaction in large-capacity, high-voltage multi-parallel and multi-series battery packs, ultimately leading to a huge safety accident.

[0004] In order to solve the above defects, a battery pack temperature monitoring method and a safety control system process structure in the BMS are improved. Summary of the invention

[0005] The object of the present invention is to provide a battery pack safety monitoring system.

[0006] The object of the present invention can be achieved by the following technical solution: A battery pack safety monitoring system, characterized in that it includes: A battery pack voltage and current monitoring module, which is responsible for real-time monitoring of the voltage and current status of the battery pack; A temperature rise monitoring and calculation module, which is used to monitor and judge the temperature of the battery cells; A single-cell parallel module, wherein a plurality of single-cell batteries are connected in series and parallel through conductive connectors to form a power source; The BMS safety monitoring module communicates data with other modules to monitor the working status of the battery pack in real time, detect faults in time and perform diagnosis.

[0007] As a preferred solution of the present invention, each battery cell of the battery parallel module uses a temperature sensor for temperature measurement, and the temperature sensor is electrically connected to one or more analog-to-digital converters, or one or more analog input terminals of one or more microprocessors.

[0008] As a preferred solution of the present invention, the BMS safety monitoring module is communicatively connected with the battery pack voltage and current monitoring module and the temperature rise monitoring and calculation module. The temperature rise monitoring and calculation module detects the battery cell temperature once every 1 to 500 ms (settable) and sends temperature data to the BMS safety monitoring module. The temperature rise monitoring and calculation module also monitors the temperature difference between battery cells in the single cell parallel module collected at a certain time t.

[0009] As a preferred solution of the present invention, the BMS safety monitoring module sets the upper and lower limits of the temperature difference between the battery cells at time t, and the BMS safety monitoring module determines whether the temperature difference between the battery cells is less than a preset difference threshold value. If the temperature difference between the battery cells is less than the preset difference threshold value ΔT, there is no need to record the normal operation. If the temperature difference between the battery cells is greater than the preset difference threshold value ΔT, the corresponding battery serial number is recorded in time, and it is determined that if the number of times the preset difference threshold value ΔT is exceeded is greater than N times (which can be set to 1 to 20 times), an alarm is issued in time to replace the faulty battery cell.

[0010] As a preferred solution of the present invention, the N times (which can be set to 1 to 20 times) is the allowed number of times set by the BMS safety monitoring module, which is used to determine whether the battery may have a fault or performance degradation.

[0011] As a preferred solution of the present invention, the BMS safety monitoring module performs graded judgment on the temperature records collected by the temperature rise monitoring and calculation module, and the graded judgment is divided into three levels: Normal operation gear X0: When T <T ref When the system temperature is normal, the data is temporarily retained; Record judgment file X1: When T ref <T<T upper When the system temperature is abnormal, it does not affect normal operation. The data is stored for a long time and the number of abnormalities is checked. If the number of abnormalities exceeds N (which can be set to 1 to 20 times), an alarm is sent; Safety alarm level X2: When T ≥ T upperWhen the system is disconnected, it will immediately send a disconnect command to maintain system safety.

[0012] As a preferred solution of the present invention, the BCU unit in the BMS safety monitoring module determines whether the temperature data sent by the temperature rise monitoring and calculation module exceeds the limit, and the BCU unit sends the data of temperature, temperature rise and temperature difference values ​​in the recording interval to the storage unit for archiving.

[0013] As a preferred solution of the present invention, the battery pack voltage and current monitoring module and the temperature rise monitoring and calculation module are powered by an external power supply or a controlled battery pack. The temperature, voltage, current and insulation status detection data of the single battery parallel module are sampled and sent to the BCU unit through the SPI isolation bus, and the BCU unit calculates and judges them.

[0014] Beneficial effects of the present invention: 1. Real-time temperature monitoring of each battery cell ensures the safety and performance of the entire battery pack. This comprehensive monitoring helps to promptly detect inconsistencies between battery cells, such as differences in internal resistance, voltage, and capacity, which may lead to uneven heat release between batteries.

[0015] 2. The system gives priority to judging the battery temperature. The battery cell temperature judgment combined with the voltage and current detection of the parallel battery pack can meet the safety requirements of battery charging and discharging.

[0016] 3. In addition to monitoring the temperature of a single battery cell, the system also monitors the degree of temperature increase (temperature rise) and the temperature difference between different cells in the same battery pack. If the temperature rise is too fast or the temperature difference is too large, this may indicate that there are problems with some battery cells, such as poor heat dissipation or uneven internal resistance.

[0017] 4. In order to reduce system sensitivity and reduce operating difficulty, it will not respond to every slight temperature anomaly. Instead, it will trigger a more in-depth investigation and repair process only when a battery cell has multiple abnormal conditions. This can avoid unnecessary maintenance work and ensure that real problems can be dealt with in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] Figure 1 It is a simplified diagram of monitoring of parallel battery packs of the present invention; Figure 2 It is a schematic diagram of the temperature rise reference curve and upper and lower limits of the temperature of a single cell of the present invention; Figure 3 It is a schematic diagram of the hardware design of the present invention; Figure 4This is a schematic diagram of the hardware design of the present invention (taking the battery module connected in parallel first and then in series as an example); Figure 5 is a control flow chart of the present invention; Figure 6 It is a temperature detection circuit diagram of the present invention; Figure 7 This is a 24V to 5V circuit diagram of the present invention; Figure 8 It is a circuit diagram of 5V to 3.3V conversion of the present invention; Fig. 9 It is an isolated power supply circuit diagram of the CAN bus of the present invention; Fig.10 The CAN bus transceiver circuit diagram of the present invention is Fig.11 It is a block diagram of the system module of the present invention; Fig.12 It is the electronic circuit principle diagram of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Fig.11As shown in the figure, the present invention is a battery pack safety monitoring system, including a battery pack voltage and current monitoring module, a temperature rise monitoring and calculation module, a single battery parallel connection module, and a BMS safety monitoring module. The battery pack voltage and current monitoring module is responsible for real-time monitoring of the voltage and current status of the battery pack to understand the working conditions of the battery pack and provide basic data for subsequent analysis and decision-making. For example, by monitoring the voltage, the charging or discharging degree of the battery pack can be judged, and by monitoring the current, the energy transmission situation of the battery pack can be known. The temperature rise monitoring and calculation module monitors and judges the temperature of the battery cells. It detects the temperature of the battery cells once every 1 to 500 ms (settable) and sends the temperature data to the BMS safety monitoring module once. It can timely detect abnormal changes in the temperature of the battery cells and provide guarantee for the safe operation of the battery. The temperature difference between the battery cells in the single battery parallel connection module collected at a certain moment t is monitored to help judge the working state differences of each single battery in the battery pack. If the temperature difference is too large, it may mean that some batteries have problems. The single battery parallel connection module forms a power supply by connecting several single battery cells in series and parallel through conductive connectors. Each battery cell uses a temperature sensor for temperature measurement. The temperature sensor is electrically connected to one or more analog-to-digital converters, or one or more analog input terminals of one or more microprocessors, so as to realize accurate measurement and data transmission of the temperature of each battery cell. The BMS safety monitoring module communicates with other modules, real-time monitors the working state of the battery pack, timely discovers faults and conducts diagnosis, and is the core brain of the entire monitoring system. The upper and lower limits of the temperature difference between the battery cells at the set moment t are set, and it is judged whether the temperature difference between the battery cells is less than the preset difference threshold ΔT. According to the judgment result, corresponding records and processing are carried out, such as recording the corresponding battery serial number, alarming, suggesting to replace the faulty battery cell, etc. The temperature records collected by the temperature rise monitoring and calculation module are judged in different grades, divided into three grades: normal operation grade X0, record judgment grade X1, and safety alarm grade X2. Different measures are taken according to different temperature conditions, such as temporarily retaining data, permanently retaining data and checking the number of abnormalities, sending a disconnection instruction, etc. The BCU unit in it judges whether the temperature data sent by the temperature rise monitoring and calculation module exceeds the limit, and sends the data with the temperature, temperature rise, and temperature difference values within the recording range to the storage unit for archiving, which is convenient for subsequent query and analysis.

[0022] Specifically, the grading judgment is divided into three grades: Normal operation grade X0: When T < Tref, the system temperature is normal and the data is temporarily retained; Record judgment file X1: When Tref < T < Tupper, the system temperature is somewhat abnormal, but it does not affect normal operation. The data is processed for long-term retention, and the number of anomalies is checked. When the number of anomalies exceeds the number N (which can be set from 1 to 20 times), an alarm is sent; Safety alarm file X2: When T ≥ Tupper, the system immediately sends a disconnection instruction to maintain system safety.

[0023] Specifically, for the single-cell parallel module, according to the analysis of battery connection reliability and the costs and production status of various batteries, the single-cell parallel module usually adopts three series-parallel connection methods: parallel first and then series, series first and then parallel, and modular series-parallel. The single-cell parallel module newly adds a temperature sensor for the battery cell. Through the temperature rise monitoring and calculation module, the temperature data of the battery cell is recorded and judged in a timely manner. This method can be used for safety control regardless of various series-parallel connection methods such as parallel first and then series, series first and then parallel, and modular series-parallel. In this embodiment, the single-cell parallel module detects the temperature through the PT1 temperature sensor, and realizes signal differential amplification through the post-stage differential amplification circuit in the temperature detection circuit and transmits it to the temperature rise monitoring and calculation module. See the specific circuit connection in Figure 6 The power supply of the temperature detection circuit uses the LM2596-5.0 chip and the supporting circuit to convert the input voltage into 5V. See the specific circuit connection in Figure 7 Here, the input voltage is supplied by the single-cell parallel module as the controlled battery pack or an external power supply. The 5V voltage can be converted into 3.3V through the AMS1117-3.3 chip and the supporting circuit. See the specific circuit connection in Figure 8 After sampling the temperature, voltage, current, and insulation status detection data of the single-cell parallel module, they are sent to the BCU unit through the SPI isolation bus. The BCU unit calculates and judges them. Between the BCU unit and the CAN bus, communication is enabled through the CAN bus transceiver circuit, and electrical isolation of the signal is achieved. The CAN bus transceiver circuit is realized through the ISO1050DUB chip and the peripheral circuit. See the specific circuit connection in Fig.10 The isolated power supply of the CAN bus uses the CF0505 of Jin Shengyang to isolate the CAN bus power supply and generate an isolated power supply. See the specific circuit connection in Fig. 9 It converts the input +5V voltage into an isolated +5V CAN voltage for the CAN bus.

[0024] In the judgment of temperature rise data by the BMS safety monitoring module, because the most obvious feature of abnormal battery charging and discharging is a large amount of heat dissipation, which manifests as a sharp increase in temperature, in the BMS safety monitoring module, the first step when the system starts cyclic operation is to detect the temperature, and judge the single cell temperature detection program and the temperature rise detection program. The sampling time interval is fixed, and the temperature rise rate per unit time can be obtained by calculating the temperature difference between two time periods. When the same model and the same batch of battery cells leave the factory, the battery consistency is good, and the heat generation per unit time at different rates is not much different. The average heat dissipation data of the new battery cells can be collected to form an ideal heat dissipation reference database for the battery cells, which can be used as a reference for the temperature rise data of the single cells when the battery pack is put into operation. Figure 4 As shown, the upper and lower limits of battery temperature in the operation stage are generally 2-3 degrees away from the reference value. As the use time increases, the internal resistance of the battery gradually increases. When the temperature rise data repeatedly exceeds the upper limit of the set database, it means that the battery life has expired or an abnormality has occurred. You can contact the manufacturer for repair / replacement. The lower limit of the setting temperature is mainly considered to consider the consistency of the battery pack. The lower limit is set to prevent a large temperature difference between each battery cell. During the operation of the battery pack, if the temperature and temperature rise rate of a battery cell exceed the upper and lower limits, it will be recorded and stored, and the alarm will be processed according to the degree.

[0025] In the BMS safety monitoring module's judgment of temperature difference data, the most intuitive manifestation of the inconsistency of parallel battery packs is the uneven branch current. The main influencing factors leading to this phenomenon are the inconsistency of internal resistance, voltage, and capacity. Among them, when the voltage is inconsistent, a voltage difference is formed between the two strings of batteries, which will generate a relatively large instantaneous current, resulting in an increase in the instantaneous heat release of a certain battery, which can be monitored from the real-time temperature data. Single cells with lower capacity often have faster SOC changes and larger internal resistance, which will eventually be reflected in the inconsistency of heat release with other normal batteries, which can also be monitored from the real-time temperature data. It can be seen that monitoring the temperature difference between single cells in the battery pack collected at a certain time t can effectively infer the real-time status of the inconsistency between cells when the battery pack is running. Therefore, after judging the single cell temperature and the single cell temperature rise, it is necessary to compare the temperature data of multiple batteries in real time and calculate the temperature difference. As shown in Table 1, the temperature of each battery in the battery pack is collected at time t.

[0026] Table 1. Battery temperature data set at time t Cell temperature data set Tij 1 skewer 2 skewers 3 skewers … j string 1 and T11(t) T12(t) T13(t) … T1j(t) 2 and T21(t) T22(t) T23(t) … T2j(t) 3 and T31(t) T32(t) T33(t) … T3j(t) … … … … … … i merge Ti1(t) Ti2(t) Ti3(t) … Tij(t) like Figure 3As shown, set the upper and lower limits of the temperature difference between groups at time t, determine the maximum and minimum values ​​of each group of temperature values, calculate the temperature difference, and determine whether the actual difference is less than the preset difference threshold (usually 5~6°C). If the actual temperature difference is less than the preset difference threshold ΔT, there is no need to record normal operation. If it is greater than the threshold, record the corresponding battery number in time. And judge, if the number of times exceeding the range is greater than N times (can be set to 1~20 times), timely alarm to replace the faulty battery cell.

[0027] like Figure 2 The embodiment of the present invention further provides a battery pack safety monitoring system control method, comprising: S1, initialization phase: the system starts, initializes the temperature rise monitoring calculation module and the BMS safety monitoring module. Calibrate the temperature sensor of each battery cell in the single battery parallel module to ensure measurement accuracy.

[0028] S2. Data collection: The temperature rise monitoring and calculation module detects the temperature of the single battery every 1-500ms (settable), and stores the detected temperature data in the cache of the temperature rise monitoring and calculation module.

[0029] S3. Data transmission: The temperature rise monitoring and calculation module sends temperature data to the BMS safety monitoring module through the communication module every 1~500ms (configurable).

[0030] S4, data reception and preliminary judgment: The BMS safety monitoring module receives the temperature data from the temperature rise monitoring and calculation module. The BMS safety monitoring module judges whether the received temperature exceeds the limit every 1~500ms (settable).

[0031] S5. Temperature rise calculation and judgment: The BMS safety monitoring module calculates the temperature change rate (△T) every 1~500ms (settable) and compares it with the preset threshold.

[0032] S6, data recording and archiving: If the temperature, temperature rise, and temperature difference are within the recording range, the BCU unit in the BMS safety monitoring module will send the data to the storage unit for archiving. The BMS safety monitoring module monitors the number and frequency of archiving. If it exceeds the preset number N (which can be set from 1 to 20 times), it is ready to send a warning.

[0033] S7, warning and alarm processing: When the number of archives exceeds N (can be set from 1 to 20 times), the BMS safety monitoring module sends a warning to the master control through the communication module. If the temperature exceeds the highest temperature, the BMS safety monitoring module immediately sends a disconnection command to the safety protection execution module.

[0034] S8. Safety protection execution: The safety protection execution module receives the disconnection instruction and executes the operation of disconnecting the battery to prevent overheating.

[0035] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A battery pack safety monitoring system, characterized in that: include: A battery pack voltage and current monitoring module, which is responsible for real-time monitoring of the voltage and current status of the battery pack; A temperature rise monitoring and calculation module, which is used to monitor and judge the temperature of the battery cells; A single-cell parallel module, wherein a plurality of single-cell batteries are connected in series and parallel through conductive connectors to form a power source; The BMS safety monitoring module communicates data with other modules, monitors the working status of the battery pack in real time, and promptly detects and diagnoses faults.

2. A battery pack safety monitoring system according to claim 1, characterized in that: Each battery cell of the battery cell parallel module uses a temperature sensor to measure the temperature, and the temperature sensor is electrically connected to one or more analog-to-digital converters, or one or more analog input terminals of one or more microprocessors.

3. A battery pack safety monitoring system according to claim 1, characterized in that: The BMS safety monitoring module is communicatively connected with the battery pack voltage and current monitoring module and the temperature rise monitoring and calculation module. The temperature rise monitoring and calculation module detects the battery cell temperature once every 1 to 500 ms (settable) and sends temperature data to the BMS safety monitoring module. The temperature rise monitoring and calculation module also monitors the temperature difference between battery cells in the single cell parallel module collected at a certain time t.

4. A battery pack safety monitoring system according to claim 3, characterized in that: The BMS safety monitoring module sets the upper and lower limits of the temperature difference between the battery cells at time t. The BMS safety monitoring module determines whether the temperature difference between the battery cells is less than a preset difference threshold. If the temperature difference between the battery cells is less than the preset difference threshold ΔT, there is no need to record normal operation. If the temperature difference between the battery cells is greater than the preset difference threshold ΔT, the corresponding battery serial number is recorded in time, and it is determined that if the number of times the preset difference threshold ΔT is exceeded is greater than N times, an alarm is issued in time to replace the faulty battery cell.

5. A battery pack safety monitoring system according to claim 4, characterized in that: The N times is the allowed number of times set by the BMS safety monitoring module, and the range of N is 1 to 20, which is used to determine whether the battery may have a fault or performance degradation.

6. A battery pack safety monitoring system according to claim 1, characterized in that: The BMS safety monitoring module performs graded judgment on the temperature records collected by the temperature rise monitoring and calculation module. The graded judgment is divided into three levels: Normal operation gear X0: When T <T ref When the system temperature is normal, the data is temporarily retained; Record judgment file X1: When T ref <T<T upper When the system temperature is abnormal, it does not affect normal operation. The data is stored for a long time and the number of abnormalities is checked. If the number of abnormalities exceeds N, an alarm is sent; Safety alarm level X2: When T ≥ T upper When the system is disconnected, it will immediately send a disconnect command to maintain system safety.

7. A battery pack safety monitoring system according to claim 3, characterized in that: The BCU unit in the BMS safety monitoring module determines whether the temperature data sent by the temperature rise monitoring and calculation module exceeds the limit, and the BCU unit sends the data of temperature, temperature rise and temperature difference values ​​in the recording interval to the storage unit for archiving.

8. A battery pack safety monitoring system according to claim 7, characterized in that: The battery pack voltage and current monitoring module and the temperature rise monitoring and calculation module are powered by an external power supply or a controlled battery pack. The temperature, voltage, current and insulation status detection data of the single battery parallel module are sampled and sent to the BCU unit through the SPI isolation bus, and the BCU unit calculates and judges them.

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