Truck starting type lithium battery pack charging and discharging current detection method

Abstract

The invention discloses a truck starting type lithium battery pack charging and discharging current detection method, which comprises the steps of receiving and storing circuit signals, establishing a simulation detection model by reserving data, determining current conditions by analyzing a sampling circuit, and realizing temperature compensation operation during detection while determining current. The invention relates to the technical field of lithium battery charging and discharging detection. According to the truck starting type lithium battery pack charging and discharging current detection method, a simulation detection model is established by reserving data, detection data is amplified through the simulation detection model, then the current condition is determined by analyzing a sampling circuit, temperature compensation operation during detection is achieved while the current is determined, and the detection accuracy is improved. According to the invention, accurate detection of the current is realized, the response speed is high, the temperature of the current is compensated when the current passes through the detection resistor, the efficiency and accuracy of charge and discharge current detection are effectively improved, multi-platform use can be realized, and the detection cost is reduced while the applicability is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium battery charge and discharge detection, and in particular to a method for detecting charge and discharge current of a truck starter type lithium battery pack. Background Art

[0002] The pulse discharge current of existing truck starter lithium battery packs may reach 1000-2000A under the control of the BMS control system. The differential current detection port of AFE is often used for current detection. The input voltage range of the differential current detection terminal of AFE is generally ±100-200mV. To detect such a large current, it is necessary to reduce the resistance of the current detection resistor. Considering the resolution of the ADC in the AFE, a smaller current detection resistor value will reduce the accuracy of smaller current detection, resulting in inaccurate execution of the BMS algorithm and the risk of system failure.

[0003] The reference patent name is: A bidirectional dual-current detection method for a 12V24V starting lithium battery pack (patent publication number: CN116430099A, patent publication date: 2023-07-14), which includes the following steps: Step 1: During the charging and discharging of the starting lithium battery pack, the current acquisition resistor gives the collected differential voltage signal to the AFE and the current sampling circuit respectively; Step 2: The AFE is internally amplified and given to the main control unit MCU through IIC communication, and the voltage signal collected by the current sampling circuit is also amplified and given to the MCU. The MCU uses a specific algorithm to convert and compare the two groups of currents to obtain an accurate current value, thereby realizing current sampling of the 12V24V starting lithium battery pack in any application scenario, and improving the accuracy of current sampling, providing accurate current for the battery pack SOC algorithm, and improving the flexibility of battery application.

[0004] Based on the description in the above-mentioned document, the AFE front end in the existing BMS detects medium and small current signals. For the detection of large discharge current, the main circuit current signal is converted into a voltage signal through the Hall sensor and given to the BMS main control system. In order to improve the accuracy of current detection, the Hall sensor requires a low ripple power supply, and the output value of the sensor needs to be processed by software and hardware filtering algorithms, which will inevitably bring about system response delays and increased costs. In addition, the installation layout of the Hall sensor also requires a larger structural space. On the other hand, the AFE front end detection current will generate temperature rise when passing through the current sensing resistor. Large temperature changes will affect the resistance of the current sensing resistor, and thus affect the accuracy of current sampling. For this reason, the present invention provides a method for detecting charging and discharging current of a truck starting lithium battery pack. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for detecting the charging and discharging current of a truck starting lithium battery pack, which solves the problem that the AFE front-end in the existing BMS detects small current signals and converts the main circuit current signal into a voltage signal through a Hall sensor and gives it to the BMS main control system. However, the algorithm processing of the Hall sensor has response hysteresis, high cost, and requires a large space for layout. In addition, when the AFE front-end detects current, a temperature rise is generated through the current sensing resistor, and a large temperature change will affect the resistance value of the current sensing resistor.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for detecting the charging and discharging current of a truck starting type lithium battery pack, specifically comprising the following steps:

[0007] A1. A collection sensor is set on the charging and discharging circuit of the truck starter lithium battery pack to collect circuit signals;

[0008] A2. Receive circuit signals and process them. The specific steps are as follows:

[0009] a21. Receive and store circuit signals, filter and retain the circuit signals, and form a data set required for subsequent analysis and processing;

[0010] a22. Establish a simulation detection model by retaining data, amplify the detection data by the simulation detection model, and then determine the current situation by analyzing the sampling circuit, and realize temperature compensation operation during detection while determining the current;

[0011] a23. The determination result is transmitted to the MCU for conversion to obtain an accurate current value;

[0012] A3. The results obtained from the detection, processing and analysis are digitally displayed on the display terminal, and the charging and discharging strategy is adjusted based on the analysis results.

[0013] Preferably, the collection of circuit signals in A1 is achieved by setting a current multi-interval sampling circuit located on the measured circuit to perform data collection, and the current multi-interval sampling circuit is composed of a plurality of groups of small and medium current sampling circuits and current threshold detection circuits with different gain combinations, and the small and medium current sampling circuits are composed of a secondary operational amplifier circuit, and the current threshold detection circuit compares with the collected data by setting the current threshold, and controls and processes the current through the MCU after exceeding the threshold.

[0014] Preferably, the operation of a21 for screening and retaining circuit signals is:

[0015] B1. Set up a filter table for the required data, with the row headings of the table set as data categories and the column headings of the table set as collection node areas;

[0016] B2. Map the collected data to the screening table for data filling, match the category of the collected data and the corresponding collection node area with the row and column headers of the screening table, and after matching the data features with the same title content, fill the values ​​corresponding to the data features into the result grid where the row and column headers intersect;

[0017] B3. After all the collected data have been traversed, the screening table containing the numerical results is divided to form the required analysis data set according to the data category, and the data not mapped to the screening table is removed.

[0018] Preferably, the operation of establishing a simulation detection model by retaining data in a22 is:

[0019] C1. First, a basic detection model is established based on the charging and discharging circuit of the truck starter lithium battery pack, and then the analysis data set is introduced into the detection model to form a simulation detection model and realize the operation;

[0020] C2. Based on the analog detection model, a current multi-interval sampling circuit is introduced to perform regulation analysis, and multiple data measurement operations are implemented to obtain the final current value.

[0021] Preferably, the operation of amplifying the detection data by simulating the detection model in a22 is:

[0022] D1, connect a multimeter in parallel to the circuit node area to be tested for data detection, and connect a current-sensing resistor in the single line of the multimeter;

[0023] D2. Arrange NTC sampling resistor near the current sensing resistor to collect temperature value;

[0024] D3. Use a secondary operational amplifier circuit to perform gain amplification operation on the data in the detection area.

[0025] Preferably, the specific operation of the secondary operational amplifier in D3 is:

[0026] d31. The first stage circuit adopts a subtractor input configuration to amplify the voltage drop caused by the main circuit current on the current sensing resistor. Different gain adjustments can be achieved by changing the resistance value in the subtractor circuit.

[0027] d32. The second stage circuit is an amplifier circuit, which further amplifies the output signal of the first stage, so that the gain effect is amplified in a multiplication manner.

[0028] Preferably, the operation of determining the current condition by analyzing the sampling circuit in a22 is:

[0029] E1. Extract the parameters of the current sensing resistor and the NTC sampling resistor, and then analyze them in combination with the data detected by the multimeter and the temperature measurement data;

[0030] E2. Through multiple measurements, the voltage value at the current sensing resistor is marked as U n {U 1 , U 2 ,…,U n}, and calculate the measured current value of the current circuit node area based on the voltage value of the current sensing resistor, marked as I m ;

[0031] The temperature value at the NTC sampling resistor is obtained through multiple measurements and marked as T n {T 1 , T 2 , …, T n}, extract the RT comparison table of NTC sampling resistor from the historical database, and calculate the temperature deviation value marked as △T;

[0032] E3. Temperature compensation is implemented based on the measured temperature deviation value, and the actual current value is calculated according to the compensation formula and marked as I t .

[0033] Preferably, the current value I measured in E2 is m The calculation formula is:

[0034] I m =U m / R m ;

[0035] I m Indicates the calculated current value of the current circuit node area, U m Indicates the calculated voltage value of the current sensing resistor, R m Indicates the resistance value of the current sensing resistor;

[0036] U m =(U 1 +U 2 +…+U n ) / n;

[0037] U n It is represented as the detection voltage value of the nth detection resistor, and the abnormal detection voltage value is removed. If U n ≥U y or U n ≤U x , then the detected voltage value at this time is the abnormal voltage value, U y is the maximum threshold of the detection voltage, and U x is the minimum threshold of the detection voltage.

[0038] Preferably, the temperature deviation value calculation formula in E2 is:

[0039] △T=T b -T m ;

[0040] △T is the temperature deviation value. The resistance value of the NTC sampling resistor during the detection process is calculated by the instrument as R z , and T b is the resistance value R z Corresponding to the reference temperature value in the NTC sampling resistor RT comparison table, T m Then it is the calculated temperature value of the current NTC sampling resistor;

[0041]

[0042] T p is the average temperature value of the NTC sampling resistor for multiple times, |T n -T p | is the absolute value of the current sampled temperature minus the average temperature value, and the value under the square root is the absolute value of the average temperature value T p The deviation threshold between

[0043] T p =(T 1 +T 2 +…+T n ) / n;

[0044] T n It is expressed as the detected temperature value of the nth NTC sampling resistor.

[0045] Preferably, the compensation formula in E3 is:

[0046] I t =I m ×(1+k×△T);

[0047] I t is the actual current value after temperature compensation, k is the temperature compensation coefficient;

[0048] And the maximum current threshold in the current threshold detection circuit is set to I max , if I t ≥I max , it detects that the current value is greater than the set current threshold, and transmits the signal to the MCU to implement interrupt processing.

[0049] The present invention provides a method for detecting the charging and discharging current of a truck starter lithium battery pack. Compared with the prior art, it has the following beneficial effects:

[0050] 1. The truck starter lithium battery pack charge and discharge current detection method establishes a simulation detection model by retaining data, amplifies the detection data through the simulation detection model, and then determines the current situation by analyzing the sampling circuit. While determining the current, temperature compensation operation is implemented during detection, thereby realizing accurate current detection with fast response speed. At the same time, the temperature when the current passes through the detection resistor is compensated, effectively improving the efficiency and accuracy of charge and discharge current detection, and can be used on multiple platforms, thereby improving applicability and reducing detection costs.

[0051] 2. The method for detecting the charging and discharging current of the truck starting lithium battery pack maps the collected data to the screening table to fill in the data, matches the category of the collected data and the corresponding collection node area with the row title and column title of the screening table, and after matching the data features with the same title content, fills the numerical value corresponding to the data feature into the result grid where the row title and column title intersect, thereby realizing rapid screening of the collected data, and mapping and screening according to the categories used later can better facilitate the use of subsequent data extraction and search.

[0052] 3. The truck starter lithium battery pack charge and discharge current detection method extracts the parameters of the current detection resistor and the parameters of the NTC sampling resistor, and then analyzes the data detected by the multimeter and the temperature measurement data, and obtains the temperature compensation value based on the measurement, and obtains the final current value based on the temperature compensation value, thereby effectively improving the fault tolerance rate in the detection operation, and maintaining the accuracy of the detection value through multiple experimental data, thereby achieving an improvement in the current value detection response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is an operation flow chart of the charge and discharge current detection method of the present invention;

[0054] Figure 2 Operational flow chart reserved for signal screening of the circuit of the present invention. DETAILED DESCRIPTION

[0055] 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.

[0056] See also Figure 1-Figure 2 , the present invention provides two technical solutions:

[0057] Embodiment 1: A method for detecting charging and discharging current of a truck starter lithium battery pack, comprising the following steps:

[0058] A1. A collection sensor is set on the charging and discharging circuit of the truck starter lithium battery pack to collect circuit signals;

[0059] A2. Receive circuit signals and process them. The specific steps are as follows:

[0060] a21. Receive and store circuit signals, filter and retain the circuit signals, and form a data set required for subsequent analysis and processing;

[0061] a22. Establish a simulation detection model by retaining data, amplify the detection data by the simulation detection model, and then determine the current situation by analyzing the sampling circuit, and realize temperature compensation operation during detection while determining the current;

[0062] a23. The determination result is transmitted to the MCU for conversion to obtain an accurate current value;

[0063] A3. The results obtained from the detection, processing and analysis are digitally displayed on the display terminal, and the charging and discharging strategy is adjusted based on the analysis results.

[0064] The simulation detection model is a simulation model established based on the parameter data of the truck starting lithium battery pack. It aims to realize data analysis operations after simulation operations after the introduction of variable parameters, which not only improves the convenience of data analysis, but also improves the safety of data analysis processing.

[0065] Among them, an analog detection model is established by retaining data, and the detection data is amplified by the analog detection model. Then, the current situation is determined by analyzing the sampling circuit. While determining the current, temperature compensation operation is implemented during detection, thereby realizing accurate detection of current with fast response speed. At the same time, the temperature when the current passes through the detection resistor is compensated, which effectively improves the efficiency and accuracy of charge and discharge current detection, and can be used on multiple platforms, thereby improving applicability and reducing detection costs.

[0066] In an embodiment of the present invention, the collection of circuit signals in A1 is realized by setting a current multi-interval sampling circuit located on the measured circuit to perform data collection, and the current multi-interval sampling circuit is composed of a plurality of groups of small and medium current sampling circuits and current threshold detection circuits with different gain combinations, and the small and medium current sampling circuits are composed of a secondary operational amplifier circuit. The current threshold detection circuit compares with the collected data by setting the current threshold, and controls and processes the current through the MCU after exceeding the threshold.

[0067] In the embodiment of the present invention, the operation of a21 for screening and retaining the circuit signal is:

[0068] B1. Set up a filter table for the required data, with the row headings of the table set as data categories and the column headings of the table set as collection node areas;

[0069] B2. Map the collected data to the screening table for data filling, match the category of the collected data and the corresponding collection node area with the row and column headers of the screening table, and after matching the data features with the same title content, fill the values ​​corresponding to the data features into the result grid where the row and column headers intersect;

[0070] B3. After all the collected data have been traversed, the screening table containing the numerical results is divided to form the required analysis data set according to the data category, and the data not mapped to the screening table is removed.

[0071] In the embodiment of the present invention, the operation of establishing the simulation detection model by retaining data in a22 is:

[0072] C1. First, a basic detection model is established based on the charging and discharging circuit of the truck starter lithium battery pack, and then the analysis data set is introduced into the detection model to form a simulation detection model and realize the operation;

[0073] C2. Based on the analog detection model, a current multi-interval sampling circuit is introduced to perform regulation analysis, and multiple data measurement operations are implemented to obtain the final current value.

[0074] Among them, by mapping the collected data to the screening table for data filling operation, the category of the collected data and the corresponding collection node area are matched with the row title and column title of the screening table, and after matching the data features with the same title content, the values ​​corresponding to the data features are filled into the result grid where the row title and column title intersect, thereby realizing rapid screening of the collected data, and mapping and screening according to the categories used later can better facilitate the use of subsequent data extraction and search.

[0075] In the embodiment of the present invention, the operation of amplifying the detection data by the simulation detection model in a22 is:

[0076] D1, connect a multimeter in parallel to the circuit node area to be tested for data detection, and connect a current-sensing resistor in the single line of the multimeter;

[0077] D2. Arrange NTC sampling resistor near the current sensing resistor to collect temperature value;

[0078] D3. Use a secondary operational amplifier circuit to perform gain amplification operation on the data in the detection area.

[0079] In the embodiment of the present invention, the specific operation of the secondary operational amplifier in D3 is:

[0080] d31. The first stage circuit adopts a subtractor input configuration to amplify the voltage drop caused by the main circuit current on the current sensing resistor. Different gain adjustments can be achieved by changing the resistance value in the subtractor circuit.

[0081] d32. The second stage circuit is an amplifier circuit, which further amplifies the output signal of the first stage, so that the gain effect is amplified in a multiplication manner.

[0082] After the above amplification operation, if the first data amplification is 10 times and the second data amplification is also 10 times, the final data gain amplification factor is 10×10=100 times.

[0083] In the embodiment of the present invention, the operation of determining the current condition by analyzing the sampling circuit in a22 is:

[0084] E1. Extract the parameters of the current sensing resistor and the NTC sampling resistor, and then analyze them in combination with the data detected by the multimeter and the temperature measurement data;

[0085] E2. Through multiple measurements, the voltage value at the current sensing resistor is marked as U n {U 1 , U 2 , …, U n}, and calculate the measured current value of the current circuit node area based on the voltage value of the current sensing resistor, marked as I m ;

[0086] The temperature value at the NTC sampling resistor is obtained through multiple measurements and marked as T n {T 1 , T 2 ,…,T n}, extract the RT comparison table of NTC sampling resistor from the historical database, and calculate the temperature deviation value marked as △T;

[0087] E3. Temperature compensation is implemented based on the measured temperature deviation value, and the actual current value is calculated according to the compensation formula and marked as I t .

[0088] Among them, the NTC sampling resistor, that is, the negative temperature coefficient thermistor, is a sensor resistor whose resistance value decreases as the temperature increases, and the current sensing resistor Rshunt is actually a power resistor, which is usually placed in the circuit and connected in series with the load to measure the current flowing through the load. By measuring the voltage drop across Rshunt, the current value flowing through the load can be calculated. The RT comparison table is a table that describes the relationship between the resistance value of thermistor and temperature. By looking up this table, you can know the resistance value of the thermistor at a specific temperature, or calculate the corresponding temperature based on the known resistance value.

[0089] In the embodiment of the present invention, the current value I is calculated in E2 m The calculation formula is:

[0090] I m =U m / R m ;

[0091] I m Indicates the calculated current value of the current circuit node area, U m Indicates the calculated voltage value of the current-sense resistor, R m Indicates the resistance value of the current sensing resistor;

[0092] U m =(U 1 +U 2 +…+U n ) / n;

[0093] U n It is represented as the detection voltage value of the nth detection resistor, and the abnormal detection voltage value is removed. If U n ≥U y or U n ≤U x , then the detected voltage value at this time is the abnormal voltage value, U y is the maximum threshold of the detection voltage, and U x is the minimum threshold of the detection voltage.

[0094] In the embodiment of the present invention, the temperature deviation value calculation formula in E2 is:

[0095] △T=T b -T m ;

[0096] △T is the temperature deviation value. The resistance value of the NTC sampling resistor during the detection process is calculated by the instrument as R z , and T b is the resistance value R z Corresponding to the reference temperature value in the NTC sampling resistor RT comparison table, T m Then it is the calculated temperature value of the current NTC sampling resistor;

[0097]

[0098] T p is the average temperature value of the NTC sampling resistor for multiple times, |T n -T p | is the absolute value of the current sampled temperature minus the average temperature value, and the value under the square root is the absolute value of the average temperature value T p The deviation threshold between

[0099] T p =(T 1 +T 2 +…+T n ) / n;

[0100] T n It is expressed as the detected temperature value of the nth NTC sampling resistor.

[0101] In the embodiment of the present invention, the compensation formula in E3 is:

[0102] I t =I m ×(1+k×△T);

[0103] I t is the actual current value after temperature compensation, k is the temperature compensation coefficient;

[0104] And the maximum current threshold in the current threshold detection circuit is set to I max , if I t ≥I max , it detects that the current value is greater than the set current threshold, and transmits the signal to the MCU to implement interrupt processing.

[0105] The temperature compensation coefficient is a constant value, and is calculated through experiments on the physical parameters of the thermal expansion coefficient of the material, which is an existing parameter.

[0106] Among them, by extracting the parameters of the current sensing resistor itself and the parameters of the NTC sampling resistor, and then analyzing them in combination with the data detected by the multimeter and the temperature measurement data, the temperature compensation value is obtained according to the measurement, and the final current value is obtained based on the temperature compensation value, so as to effectively improve the fault tolerance rate in the detection operation, and maintain the accuracy of the detection value through multiple experimental data, so as to achieve an improvement in the response speed of current value detection.

[0107] The difference between the second embodiment and the first embodiment is that the existing charge and discharge current detection method and the charge and discharge current detection method of the present invention are applied, and the charge and discharge detection operation is performed on the same truck starting type lithium battery, and the time taken to complete the detection and obtain the data and the accuracy of the data are recorded. The specific results are shown in Table 1:

[0108] Table 1 Data record table

[0109]

[0110] In summary, by adopting the charge and discharge current detection method of the present invention to implement application operations, the average time after multiple detections is shorter, and the final result value matches the known result value with higher accuracy. Therefore, the charge and discharge current detection method of the present invention can be better applied to actual operations.

[0111] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0112] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0113] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for detecting the charging and discharging current of a truck starter lithium battery pack, characterized in that: The specific steps include: A1. A collection sensor is set on the charging and discharging circuit of the truck starter lithium battery pack to collect circuit signals; A2. Receive circuit signals and process them. The specific steps are as follows: a21. Receive and store circuit signals, filter and retain the circuit signals, and form a data set required for subsequent analysis and processing; a22. Establish a simulation detection model by retaining data, amplify the detection data by the simulation detection model, and then determine the current situation by analyzing the sampling circuit, and realize temperature compensation operation during detection while determining the current; a23. The determination result is transmitted to the MCU for conversion to obtain an accurate current value; A3. The results obtained from the detection, processing and analysis are digitally displayed on the display terminal, and the charging and discharging strategy is adjusted based on the analysis results.

2. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 1, characterized in that: The circuit signal acquisition in A1 is realized by setting a current multi-interval sampling circuit located on the measured circuit to perform data acquisition, and the current multi-interval sampling circuit is composed of a plurality of groups of small and medium current sampling circuits and current threshold detection circuits with different gain combinations, and the small and medium current sampling circuits are composed of a secondary operational amplifier circuit. The current threshold detection circuit compares with the collected data by setting the current threshold, and controls and processes the current through the MCU after exceeding the threshold.

3. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 1, characterized in that: The operation of a21 to screen and retain the circuit signal is: B1. Set up a filter table for the required data, with the row headings of the table set as data categories and the column headings of the table set as collection node areas; B2. Map the collected data to the screening table for data filling, match the category of the collected data and the corresponding collection node area with the row and column headers of the screening table, and after matching the data features with the same title content, fill the values ​​corresponding to the data features into the result grid where the row and column headers intersect; B3. After all the collected data have been traversed, the screening table containing the numerical results is divided to form the required analysis data set according to the data category, and the data not mapped to the screening table is removed.

4. The method for detecting charging and discharging current of a truck starter lithium battery pack according to claim 3, characterized in that: The operation of establishing a simulation detection model by retaining data in a22 is: C1. First, a basic detection model is established based on the charging and discharging circuit of the truck starter lithium battery pack, and then the analysis data set is introduced into the detection model to form a simulation detection model and realize the operation; C2. Based on the analog detection model, a current multi-interval sampling circuit is introduced to perform regulation analysis, and multiple data measurement operations are implemented to obtain the final current value.

5. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 1, characterized in that: The simulation detection model in a22 realizes the operation of amplifying the detection data as follows: D1, connect a multimeter in parallel to the circuit node area to be tested for data detection, and connect a current-sensing resistor in the single line of the multimeter; D2. Arrange NTC sampling resistor near the current sensing resistor to collect temperature value; D3. Use a secondary operational amplifier circuit to perform gain amplification operation on the data in the detection area.

6. The method for detecting charging and discharging current of a truck starter lithium battery pack according to claim 5, characterized in that: The specific operation of the secondary operational amplifier in D3 is: d31. The first stage circuit adopts a subtractor input configuration to amplify the voltage drop caused by the main circuit current on the current sensing resistor. Different gain adjustments can be achieved by changing the resistance value in the subtractor circuit. d32. The second stage circuit is an amplifier circuit, which further amplifies the output signal of the first stage, so that the gain effect is amplified in a multiplication manner.

7. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 1, characterized in that: The operation of determining the current condition by analyzing the sampling circuit in a22 is as follows: E1. Extract the parameters of the current sensing resistor and the NTC sampling resistor, and then analyze them in combination with the data detected by the multimeter and the temperature measurement data; E2. Through multiple measurements, the voltage value at the current sensing resistor is marked as U n {U1, U2, ..., U n }, and calculate the measured current value of the current circuit node area based on the voltage value of the current sensing resistor, marked as I m ; The temperature value at the NTC sampling resistor is obtained through multiple measurements and marked as T n {T1, T2, ..., T n }, extract the RT comparison table of NTC sampling resistor from the historical database, and calculate the temperature deviation value marked as △T; E3. Temperature compensation is implemented based on the measured temperature deviation value, and the actual current value is calculated according to the compensation formula and marked as I t .

8. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 7, characterized in that: The current value I is calculated in E2 m The calculation formula is: I m =U m / R m ; I m Indicates the calculated current value of the current circuit node area, U m Indicates the calculated voltage value of the current sensing resistor, R m Indicates the resistance value of the current sensing resistor; U m =(U1+U2+…+U n ) / n; U n It is represented as the detection voltage value of the nth detection resistor, and the abnormal detection voltage value is removed. If U n ≥U y or U n ≤U x , then the detected voltage value at this time is the abnormal voltage value, U y is the maximum threshold of the detection voltage, and U x is the minimum threshold of the detection voltage.

9. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 7, characterized in that: The temperature deviation value calculation formula in E2 is: △T=T b -T m ; △T is the temperature deviation value. The resistance value of the NTC sampling resistor during the detection process is calculated by the instrument as R z , and T b is the resistance value R z Corresponding to the reference temperature value in the NTC sampling resistor RT comparison table, T m Then it is the calculated temperature value of the current NTC sampling resistor; T p is the average temperature value of the NTC sampling resistor for multiple times, |T n -T p | is the absolute value of the current sampled temperature minus the average temperature value, and the value under the square root is the absolute value of the average temperature value T p The deviation threshold between T p =(T1+T2+…+T n ) / n; T n It is expressed as the detected temperature value of the nth NTC sampling resistor.

10. The method for detecting charging and discharging current of a truck starting type lithium battery pack according to claim 9, characterized in that: The compensation formula in E3 is: I t =I m ×(1+k×△T); I t is the actual current value after temperature compensation, k is the temperature compensation coefficient; And the maximum current threshold in the current threshold detection circuit is set to I max , if I t ≥I max , it detects that the current value is greater than the set current threshold, and transmits the signal to the MCU to implement interrupt processing.

Images