Battery Pack Acquisition Line Impedance and Fault Detection Method and System

Abstract

This invention discloses a method and system for impedance acquisition and fault detection of a battery pack, comprising: obtaining the electrical signal of each cell transmitted by the acquisition line when the discharge current is 0, including the voltage difference V across the cell. iD Let i = 1, 2, 3…n. The system determines whether the acquisition line is broken based on the electrical signal. When the discharge current I is the first current value (0.1A, 1A), the system acquires the positive voltage V of the first cell transmitted by the acquisition line. 1PC and the voltage difference V across the two ends 1DC According to V 1PC V 1DC and V 1D Calculate the impedance of the acquisition line connecting the positive and negative terminals of the first battery cell; starting from i=2, control the discharge current I of the i-th battery cell to the first current value, and acquire the voltage difference V across the i-th battery cell transmitted by the acquisition line through the acquisition circuit. iDC According to V iD V iDC and R w(i‑1) Calculate the impedance of the acquisition line at the positive terminal of the i-th cell; increment i by 1 and repeat the above steps until i = n, thus obtaining the impedance R of all acquisition lines. w0 -R wn Compared with existing technologies, the present invention has higher accuracy in detection and diagnosis.

Description

Technical Field

[0001] This invention relates to the field of battery data acquisition and fault diagnosis technology, and in particular to a method and system for detecting the acquisition line impedance and faults of battery packs. Background Technology

[0002] Most lithium batteries on the market today come with a battery protection board. Generally, this board connects to the battery pack via voltage acquisition lines and collects information such as the voltage of individual cells, thus enabling charging or discharging protection based on the battery status information. During prolonged use, vibration or battery assembly issues can cause faults such as poor contact or loosening of the voltage acquisition lines, affecting the accuracy of battery status information acquisition or preventing correct detection. When a lithium-ion battery voltage acquisition line malfunctions (e.g., poor contact or breakage), it can trigger false protection, preventing the battery system from charging or discharging. Furthermore, the inability to diagnose the fault in time can lead to safety hazards such as overcharging or over-discharging during use. Therefore, it is necessary to promptly detect faults in the acquisition lines.

[0003] Current technologies typically detect battery disconnections by injecting a small current (mA level). The same ADC is used to measure the voltage change before and after the current injection. If the voltage change exceeds a threshold, it is diagnosed as normal; otherwise, it is diagnosed as abnormal. This method can diagnose battery disconnections, but it cannot effectively detect the impedance range of the voltage acquisition line.

[0004] Therefore, there is an urgent need for a method and system for acquiring line impedance and detecting faults in battery packs that can solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for acquiring line impedance and detecting faults in battery packs, which achieves higher accuracy in detection and diagnosis.

[0006] To achieve the above objectives, this invention provides a method for impedance and fault detection of a battery pack's acquisition line. The battery pack contains n cells, arranged sequentially from the negative terminal to the positive terminal, with n being greater than or equal to 2. Several acquisition lines are provided to acquire the electrical signal of each cell in the battery pack. The method for impedance and fault detection of the acquisition line is used to detect the continuity and impedance of the acquisition lines, including: Step 1, controlling the discharge current of the battery pack to 0, and acquiring each electrical signal output by the acquisition lines. The electrical signal includes the voltage difference between the terminals of the first to nth cells to obtain the voltage difference V across the i-th cell. iDLet i = 1, 2, 3…n. Based on the electrical signal, determine if the acquisition line is broken. If so, report a breakage fault; otherwise, proceed to the next step. Step 2: Control the discharge current I of the first cell to a first current value, where the first current value belongs to [0.1A, 1A]. Acquire the positive voltage V of the first cell output by the acquisition line. 1PC The voltage difference V between the two ends of the first cell 1DC Step 3, according to formula R w0 = (V 1PC -V 1DC ) / I, calculate the impedance R of the acquisition line of the negative terminal of the first cell. w0 According to formula R w1 =(V 1D -V 1PC ) / I, calculate the impedance R of the acquisition line of the positive terminal of the first cell. w1 Step 4: Starting from i=2, control the discharge current I of the i-th cell to the first current value, and collect the voltage difference V across the i-th cell output by the acquisition line. iDC Step 5, use formula R wi =[(V iD -V iDC )- I*R w（i-1） ] / I Calculate the impedance of the acquisition line of the positive terminal of the i-th cell; Step 6, increment i by 1, and repeat steps 4 to 5 until i = n, thereby calculating the impedance R of all acquisition lines. w0 R w1 R w2 …R wn .

[0007] Preferably, the first current value is 0.5A.

[0008] Preferably, the method for detecting impedance and faults of the acquisition line further includes step 7, which determines whether an impedance fault exists based on the impedance of the acquisition line.

[0009] Specifically, in step 7, the judgment formula V iD / (R wi +R w(i-1) If the result is less than the preset current value I, then report an impedance overload fault.

[0010] Specifically, in step 7, R is determined. wn and R w(n-1) If the impedance range is within the preset resistance range, the impedance is normal; otherwise, an impedance fault alarm is triggered. More specifically, the preset resistance range is [0.1Ω, 1Ω].

[0011] In step 1, the collected electrical signals also include the positive and negative voltages of the first to nth cells, in order to obtain the positive voltage V of the i-th cell. iP The negative terminal voltage V of the i-th cell iN According to the positive voltage V iP Negative voltage V iN and voltage difference V iD Determine if the acquisition line is broken. This invention obtains the positive electrode voltage V of the first to nth cells respectively. iP Negative voltage V iN and the voltage difference V across the two ends iD The system uses three ADCs to acquire voltage data, performing both single-point and differential voltage acquisition, and incorporates redundancy detection, effectively improving the reliability of the acquisition.

[0012] This invention also provides a battery pack impedance acquisition and fault detection system, including acquisition lines, a selection switch circuit, a discharge module, an acquisition circuit, and a control module. The acquisition lines are multiple and connected to the positive and negative terminals of each cell in the battery pack. The input terminal of the selection switch circuit is connected to the output terminal of each acquisition line, and selects two of the electrical signals acquired by the acquisition lines before transmitting them to the discharge module through the two output terminals of the selection switch circuit. The discharge module receives the electrical signals output from the two output terminals and forms a discharge circuit that allows the two output terminals of the selection switch circuit to discharge externally with a controllable discharge current. The acquisition circuit acquires the electrical signals from the two output terminals. The control module controls the operation of the selection switch circuit and the discharge module, and obtains the electrical signals acquired by the acquisition circuit. The control module includes a processor, a memory, and one or more operating programs stored in the memory. The processor executes the operating programs to implement the battery pack impedance acquisition and fault detection method described above.

[0013] Preferably, the discharge module is a bidirectional constant current DC / DC power supply or a constant current DC discharge circuit.

[0014] Preferably, the output terminal of the discharge module is connected to the positive and negative terminals of the total output of the battery pack to form a discharge circuit.

[0015] Compared with existing technologies, this invention uses both a charging current of 0A and a discharging current of ≥0.1A for comparative detection, resulting in a larger voltage difference under different discharging currents. This allows for more effective and accurate detection of small impedance values ​​(e.g., 0.1Ω) on the acquisition line. Furthermore, the calculation formula of this invention is more reasonable, taking into account the case of unequal impedance values ​​on the acquisition line and performing targeted detection accordingly, further improving the accuracy of the detection. Attached Figure Description

[0016] Figure 1This is a structural diagram of the battery pack acquisition line impedance and fault detection system of the present invention.

[0017] Figure 2 This is a structural diagram of the battery pack acquisition line impedance and fault detection method of the present invention. Detailed Implementation

[0018] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0019] refer to Figure 1 The present invention discloses a battery pack acquisition line impedance and fault detection system 100, including acquisition lines L1-Ln, a selection switch circuit 20, a discharge module 30, an acquisition circuit 50 and a control module 40.

[0020] refer to Figure 1 The battery pack can be a lithium-ion battery pack, consisting of n cells connected in series, where n is greater than or equal to 2. The n cells connected in series correspond to n+1 data acquisition lines L0-L1. n Above, the acquisition line L0-L n There are n+1 wires connected to the positive and negative terminals of each cell in the battery pack, and n+1 data acquisition lines L0-L n The corresponding impedances are Rw0 and Rwn, respectively.

[0021] refer to Figure 1 The selection switch circuit 20 has connections to each of the acquisition lines L j It has an input terminal and two output terminals, j=0, 1, 2…n, and its input terminal is connected to each of the aforementioned acquisition lines L. j and the acquisition line L0-L n After selecting two of the acquired electrical signals, they are transmitted to the discharge module 30 through two output terminals. The electrical signals output from the two output terminals are CELL+ and CELL-. The selection switch circuit is a MUX switch matrix, used to select the channel of the battery cell.

[0022] The MUX switch matrix is ​​based on opposing MOSFETs or relay switches, and the switching of individual battery channels is completed in a time-division manner under the control of logic circuits. This is a well-known technology in the industry and will not be described in detail here.

[0023] refer to Figure 1 The discharge module 30 receives electrical signals CELL+ and CELL- from the two output terminals and forms a discharge circuit that allows the two output terminals of the selection switch circuit 20 to discharge to the outside with a controllable discharge current, so that the selection switch circuit 20 selects the two ends of the battery cell connected by the two acquisition lines to discharge with a corresponding current.

[0024] The discharge module 30 is either a bidirectional constant current DC / DC power supply or a constant current DC discharge circuit, and the control module 40 controls the discharge current of the discharge module 30. The bidirectional constant current DC / DC power supply is only used for its discharge function.

[0025] The bidirectional constant current DC / DC power supply can be a flyback power supply architecture or a BUCK-Boost power supply architecture. The control module 40 dynamically outputs a current control signal (generally a PWM duty cycle and switching direction) based on the information of its internal discharge current to control the bidirectional constant current DC-DC power supply to achieve constant current output. The above are technologies known in the industry and will not be described in detail here.

[0026] The output terminal of the discharge module 30 is connected to the positive terminal P+ and the negative terminal P- of the battery pack to form a discharge circuit.

[0027] refer to Figure 1 The acquisition circuit 50 acquires the voltage signals from the two output terminals of the gating switch circuit 20.

[0028] Specifically, the acquisition circuit 50 acquires the positive voltage, negative voltage, and voltage difference between the two terminals of the first to nth cells, respectively. This acquisition circuit 50 is a voltage and current acquisition circuit containing multiple ADCs, capable of acquiring the single-point voltage of CELL+, the voltage V- of CELL-, and the voltage difference VD between CELL+ and CELL-. The discharge current value is obtained by converting the voltage across the shunt resistor.

[0029] refer to Figure 1 The control module 40 controls the selection channel of the selection switch circuit 20, controls the discharge current of the discharge module 30, and obtains the electrical signal acquired by the acquisition circuit 50. Specifically, the acquisition circuit 50 acquires the voltage of the corresponding battery cell and the selected discharge current.

[0030] Specifically, the control module 40 includes a processor, a memory, and one or more operating programs stored in the memory. The processor executes the operating programs to implement the battery pack acquisition line impedance and fault detection method.

[0031] refer to Figure 2 The method for collecting line impedance and fault detection includes steps S11 to S19.

[0032] S11, control the discharge current of the battery pack to 0 (for example, control the discharge module 30 to turn off).

[0033] S12, the control selection switch circuit 20 sequentially selects the electrical signals of the positive and negative terminals of the first to nth cells, and the acquisition circuit 50 acquires the electrical signals of the first to nth cells respectively.

[0034] S13, determine whether the acquisition line is broken based on the electrical signal. If it is not broken, continue to the next step; if it is broken, report the breakage fault.

[0035] Specifically, the acquisition circuit 50 acquires the positive electrode voltage, negative electrode voltage, and voltage difference between the positive and negative terminals of the first to nth cells respectively, to obtain the positive electrode voltage V of the i-th cell. iP The voltage V at the negative terminal iN and the voltage difference V across the two ends iD i = 1, 2, 3…n, based on the positive voltage V iP Negative voltage V iN and voltage difference V iD Determine if the acquisition cable is broken.

[0036] Among them, when the negative voltage V iN If the voltage difference is not within the threshold range (e.g., [1V, 5V]), the acquisition line is considered broken. iD If the voltage is outside the threshold range (e.g., [1V, 5V]), the acquisition line is considered broken. If the negative voltage V... iN and voltage difference V iD If it falls within the threshold range, it is determined to be a data acquisition line connection.

[0037] S14, the selection switch circuit 20 is controlled to select the electrical signals of the positive and negative terminals of the first battery cell, so that the discharge module 30 discharges the battery cell, and the discharge current I of the first battery cell is controlled to be a first current value, which is greater than or equal to 0.1A and less than or equal to 1A. In this embodiment, the first current value is 0.5A.

[0038] S15, the positive voltage V of the first battery cell is acquired through the acquisition circuit 50. 1PC The voltage difference V between the two ends of the first cell 1DC .

[0039] S16, according to V 1PC V 1DC and V 1D Calculate the impedance of the acquisition lines L1 and L0 that connect the positive and negative terminals of the first battery cell.

[0040] Specifically, according to formula R w0 = (V 1PC -V 1DC ) / I Calculate the impedance R of the acquisition line L0 of the negative terminal of the first cell. w0 According to formula R w1 =(V 1D -V 1PC ) / I Calculate the impedance R of the acquisition line L1 of the positive terminal of the first cell.w1 .

[0041] When the discharge current I = 0, the impedance R on the acquisition line L1 is... w1 and the impedance R on the acquisition line L0 w0 The voltage drop across the battery is close to 0, so the voltage of the first cell is V1≈V1D, denoted as Equation 1.

[0042] When the discharge current is the first current value, the acquisition circuit 50 acquires the positive voltage V of the first cell. 1PC This corresponds to the single-point voltage of CELL+, and the voltage difference V across the first cell acquired by the acquisition circuit 50. 1DC It is the differential voltage between CELL+ and CELL-.

[0043] Therefore, (V1-V 1PC )=I*R w1 Let this be denoted as Equation 2. (V1-V 1DC )=I*R w1 +I*R w0 Let this be denoted as Equation 3.

[0044] Substituting equation 1 into equation 2, we obtain R. w1 =(V 1D -V 1PC Equation 4, impedance R of acquisition line L1 w1 It is a positive number greater than 0.

[0045] Substituting equations 1 and 4 into equation 3, we get:

[0046] R w0 =[(V 1D -V 1DC )-(V 1D -V 1PC )] / I=(V 1PC -V 1DC ) / I --- Equation 5.

[0047] S17, starting from i=2, the selection switch circuit 20 is controlled to select the electrical signals of the positive and negative terminals of the i-th cell, which are then discharged through the discharge module 30. The discharge current I of the i-th cell is controlled to be a first current value, and the voltage difference V across the i-th cell is acquired by the acquisition circuit 50. iDC .

[0048] S18, based on voltage difference V iD Voltage difference V iDC and acquisition line L j-1 impedance R w(i-1) Calculate the acquisition line L of the positive electrode of the i-th cell. j impedance R wi, i=j.

[0049] Specifically, using formula R wi =[(V iD -V iDC )- I*R w（i-1） ] / I Calculate the acquisition line L of the positive electrode of the i-th cell j impedance R wi .

[0050] Among them, (V) iD -V iDC )=I*R wi +I*R w（i-1） ---Equation 6;

[0051] Substituting equation 4 into equation 6, we get R wi =[(V i D -V i DC )- I*R w（i-1） ] / I, and use this to obtain R wi .

[0052] S19, increment i by 1, and repeat steps S17 to 18 until i = n, thereby calculating the impedance R of all acquisition lines L0-L1 in the battery pack. w0 R w1 R w2 …R wn .

[0053] Preferably, the method for detecting impedance and faults of the acquisition line further includes S20, which determines whether an impedance fault exists based on the impedance of the acquisition line.

[0054] Specifically, in step S20, the judgment formula V is determined. iD / (R wi +R w(i-1) If the result is less than the preset current value I, then report an impedance overload fault.

[0055] Specifically, in step S20, the R is determined. wn and R w(n-1) If the impedance range is within the preset resistance range, the impedance is normal; otherwise, an impedance fault alarm is triggered. Specifically, the preset resistance range is [0.1Ω, 1Ω].

[0056] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the scope of the present invention are still within the scope of the present invention.

Claims

1. A method for detecting the impedance and fault of a harvesting line of a battery pack, the battery pack having n cells, and comprising the first cell to the nth cell in sequence from the negative electrode to the positive electrode of the battery pack, n being greater than or equal to 2, the harvesting line having a plurality of lines and harvesting the electrical signal of each cell in the battery pack. The acquisition line impedance and fault detection method is used for detecting the on-off and impedance of the acquisition line, and is characterized in that: It comprises: Step 1, control the discharge current of the battery pack to be 0, collect each electrical signal output by the collection line, the electrical signal including voltage differences between the first and nth battery cells, to obtain the voltage difference V between the ith battery cell iD , i = 1, 2, 3…n, determine whether the collection line is broken according to the electrical signal, if yes, report a broken line fault, if not, proceed to the next step; Step 2, control the discharge current I of the first battery cell to be a first current value, the first current value belongs to [0.1A, 1A], and collect the positive electrode voltage V of the first battery cell output by the collection line 1PC and the voltage difference V across the first battery cell 1DC ; Step 3, according to formula R w0 = (V 1PC -V 1DC ) / I, calculate the impedance R of the acquisition line of the negative terminal of the first cell. w0 According to formula R w1 =(V 1D -V 1PC ) / I, calculate the impedance R of the acquisition line of the positive terminal of the first cell. w1 ; Step 4, starting from i = 2, controlling the discharging current I of the i-th battery cell to be the first current value, collecting the voltage difference V across the i-th battery cell output by the collection line iDC ; Step 5, calculate the impedance of the collection wire of the positive electrode of the ith battery cell using the formula R wi = [(V iD -V iDC )- I*R w（i-1） ] / I Step 6, i+1, repeat steps 4 to 5 until i=n, so that the impedance R of all acquisition lines is calculated w0 , R w1 , R w2 …R wn .

2. The method of harvesting line impedance and fault detection for a battery pack of claim 1, wherein: The first current value is 0.5 A.

3. The method of harvesting line impedance and fault detection for a battery pack of claim 1, wherein: It further comprises a step 7 of determining whether there is an impedance fault according to the impedance of the acquisition line.

4. The method of harvesting line impedance and fault detection for a battery pack of claim 3, wherein: In step 7, it is judged whether the result of the formula V iD / (R wi +R w(i-1) ) is less than a preset current value I, and if yes, an impedance too large fault is reported.

5. The method of harvesting line impedance and fault detection for a battery pack of claim 3, wherein: In step 7, it is judged whether the impedance range of R wn and R w(n-1) is within a preset resistance range. If yes, the impedance is normal, and if not, an impedance fault alarm is performed.

6. The method of harvesting line impedance and fault detection for a battery pack of claim 5, wherein: The preset resistance range is [0.1Ω, 1Ω].

7. The method of harvesting line impedance and fault detection for a battery pack of claim 1, wherein: In the step 1, the collected electric signal further includes the positive electrode voltage, the negative electrode voltage of the 1st to the nth battery cell, so as to obtain the positive electrode voltage V iP of the i th battery cell, the negative electrode voltage V iN of the i th battery cell, and the voltage difference V iP between the positive electrode voltage V iN and the negative electrode voltage V iD , and the determination of whether the collection line is disconnected is based on the positive electrode voltage V iP , the negative electrode voltage V iN and the voltage difference V iP .

8. A battery pack harvesting line impedance and fault detection system, characterized by: It comprises an acquisition line, a gating switch circuit, a discharge module, an acquisition circuit and a control module, the acquisition line has a plurality of lines and is connected to the positive and negative poles of each cell in the battery pack, the input end of the gating switch circuit is connected to the output end of each acquisition line, and the electrical signals collected by the acquisition line are selected and sent to the discharge module through two output ends of the gating switch circuit, the discharge module connects the electrical signals output from the two output ends and forms a discharge circuit that enables the two output ends of the gating switch circuit to discharge externally and the discharge current to be controllable, the acquisition circuit acquires the electrical signals of the two output ends, and the control module controls the gating switch circuit and the discharge module to act and acquires the electrical signals collected by the acquisition circuit. The control module comprises a processor, a memory, one or more operation programs stored in the memory, and the processor executes the operation programs to realize the acquisition line impedance and fault detection method of the battery pack according to any one of claims 1-7.

9. The battery pack harvest line impedance and fault detection system of claim 8, wherein: The discharge module is a bidirectional constant-current DC / DC direct-current power supply or a constant-current direct-current discharge circuit.

10. The battery pack harvest line impedance and fault detection system of claim 8, wherein: The output end of the discharge module is connected to the positive and negative poles of the total output of the battery pack to form a discharge circuit. The output end of the discharge module is connected to the positive and negative poles of the total output of the battery pack to form a discharge circuit.

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