A battery external short circuit test and short circuit data analysis device and method

Abstract

The present invention relates to the technical field of battery testing, and in particular to a device and method for battery external short circuit testing and short circuit data analysis, comprising a host computer, a data acquisition unit, a control unit and a power unit; the host computer and the control unit are connected via serial communication, and the host computer is electrically connected to a camera; the data acquisition unit is electrically connected to the host computer and the battery under test, and the data acquisition unit includes a measurement board and an acquisition card; the power unit includes n The system consists of a single, identical short-circuit branch, composite busbar, and total absorption loop. The control unit communicates with the power unit and data acquisition unit via optical fiber. This system simulates the short-circuit response of a real battery from the moment it begins to short-circuit until the fuse blows, making the short-circuit current adjustable and the short-circuit duration controllable. It also analyzes battery short-circuit data, demonstrating the characteristics of the battery at each stage of the short-circuit, providing a reliable analysis tool for selecting battery electrical models and identifying parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of battery testing, and in particular to a device and method for battery external short-circuit testing and short-circuit data analysis. Background Art

[0002] Lithium-ion batteries, as a green energy storage method, offer high energy density, long life, fast charging, and environmental friendliness. Battery systems composed of lithium-ion batteries are widely used in wind and solar energy storage systems, electric vehicles, substations, and data center backup power systems. Battery systems are characterized by high voltage levels and large capacities. However, if an external short circuit occurs, it can easily cause large-scale thermal runaway, leading to serious safety incidents. Therefore, scientific and rational external short-circuit protection design is essential for battery systems.

[0003] At present, there are the following problems in the design of external short-circuit protection: the battery external short-circuit scenario is difficult to reproduce; the testing cost is high and the external short-circuit protection simulation model and calculation analysis tools have not been established.

[0004] External short-circuit protection in battery systems typically involves the coordinated use of tiered fuses in conjunction with the battery management system (BMS). The period from the onset of a short circuit to fuse blowout is characterized by a high discharge rate and a short discharge time. In practical applications, the external short-circuit protection time for battery systems is measured in milliseconds, and the short-circuit current can reach thousands or even tens of thousands of amperes. In laboratory environments, commercially viable equipment capable of high-rate battery discharge is battery charging and discharging equipment and large-scale short-circuit testing machines, but both have their limitations.

[0005] Battery charging and discharging equipment can control the short-circuit time, but the short-circuit current cannot reach thousands of amperes due to equipment channel limitations. At the same time, the equipment cannot truly show the change of short-circuit current over time. From the perspective of current size and current change over time, it does not meet the requirements of external short-circuit protection experiments; large-scale short-circuit testing machines can truly show the change relationship between short-circuit current and time, but the contactor breaking time is on the scale of seconds, which is mainly used for uncontrolled short-circuit experiments. When the cooperation of fuses is required, the experimental cost is high and it is difficult to reproduce the external short-circuit scenario of the battery.

[0006] For high-voltage battery systems, any external short-circuit device is difficult to guarantee the safety of external short-circuit testing, and testing carries significant risks and costs. Furthermore, effective testing and analysis methods are lacking, and simulation models and computational analysis tools for battery system external short-circuit testing have not yet been established. To simulate the short-circuit response of a real battery from the onset of the short circuit to the blown fuse protection, and to reproduce short-term, high-current scenarios, it is necessary to build a time-controllable, current-adjustable external short-circuit experimental device. Based on this experimental platform, the short-circuit characteristics of lithium-ion batteries at different time and current scales can be analyzed. This serves as a foundation for establishing simulation models and computational analysis tools for battery system external short-circuit protection. This has important practical engineering implications for damage analysis of high-rate batteries and fuse selection.

[0007] Currently, battery external short-circuit testing is primarily performed using battery charging and discharging equipment, large-scale short-circuit testing machines, and battery external short-circuit testing platforms. Due to the limited number of channels in these equipment, battery charging and discharging equipment cannot apply discharge currents exceeding several thousand amperes to measure the battery's short-circuit current. Furthermore, the discharge current provided by battery charging and discharging equipment is controlled by the equipment itself and fails to reflect the battery's true short-circuit state.

[0008] Large-scale short-circuit testing machines can simulate the actual short-circuit state of a battery, but the contactor disconnection time is on the order of seconds. Generally, destructive short-circuit tests are conducted. Batteries are disposable, and the experimental cost is high. In addition, the magnitude of the short-circuit current cannot be controlled, making it difficult to analyze the damage caused to the battery by different short-circuit currents.

[0009] The battery external short-circuit test platform can achieve adjustable short-circuit current and controllable short-circuit time by controlling the on and off of multiple parallel MOSFETs, but its temperature acquisition function requires professional equipment and is not controlled by a single software; at the hardware level, the equipment does not have overcurrent protection for MOSFETs; the parallel connection of MOSFET units uses a busbar, and spike voltages will be generated at both ends of the drain and source when the MOSFET is turned off. If the main line current is too large, it is easy to break down the MOSFET, thereby damaging the equipment; the number of MOSFETs that are turned on and off can be controlled by the program, but the MOSFET that needs to be turned on cannot be arbitrarily selected, and the device does not have feedback information on whether the MOSFET is successfully turned on, which is not conducive to equipment inspection and maintenance.

[0010] When selecting a suitable fuse to provide fuse protection for a high-voltage energy storage battery system, it is necessary to establish an external short-circuit simulation model and calculation analysis tools for the battery system.

[0011] The above three devices can only record preliminary short-circuit data. Simulation model selection currently requires the use of third-party programming tools to extract and analyze short-circuit data, which is inefficient. Furthermore, none of the above three devices can provide synchronized video monitoring of battery status, requiring an external camera and resulting in poor synchronization. Summary of the Invention

[0012] In response to the shortcomings of the existing technology, the present invention provides a battery external short-circuit testing and short-circuit data analysis device and method, which can simulate the short-circuit response of a real battery from the start of the short circuit to the fuse blowing protection, making the short-circuit current adjustable and the short-circuit time controllable; it can analyze battery short-circuit data and intuitively display the characteristics of the battery at each short-circuit stage, providing a reliable analysis tool for battery electrical model selection and parameter identification.

[0013] The present invention is achieved through the following technical solutions:

[0014] Provided is a battery external short-circuit test and short-circuit data analysis device, comprising a host computer, a data acquisition unit, a control unit, and a power unit;

[0015] The host computer and the control unit are connected via a serial communication port, and the host computer is also electrically connected to a camera for monitoring the external state of the battery.

[0016] The data acquisition unit is electrically connected to the host computer and the battery under test respectively. The data acquisition unit includes a measurement board and an acquisition card, which are used to collect battery short-circuit characteristic parameters and upload them to the host computer.

[0017] The power unit includes n The same short-circuit branches, composite busbars and total absorption circuits are connected in parallel through the composite busbars. The composite busbars are provided with copper cables for connecting to the battery under test. The total absorption circuit is connected in parallel to the positive and negative terminals of the composite busbars. The total absorption circuit includes capacitors. C 1 ,resistance R 1 and Schottky diodes D 1 ,resistance R 1 and Schottky diodes D 1 After connecting in parallel with the capacitor C 1 Series connection.

[0018] The control unit is connected to the power unit and the data acquisition unit through optical fibers. The control unit includes a serial communication module, a digital signal processing module, and a photoelectric conversion module. The serial communication module communicates with the host computer. The digital signal processing module includes a single-chip microcomputer and a programmable logic device (CPLD), calculates and sends logic signals, and receives feedback signals transmitted by the data acquisition unit. The photoelectric conversion module includes a driver chip, an optical fiber transmitter n1, an optical fiber receiver n2, and multiple optical fiber transmitters m. The optical fiber transmitter n1 is connected to the optical fiber receiver n1 of the measurement board through optical fiber, and is used to transmit the number of MOSFET conduction to the measurement board. The optical fiber receiver n2 is connected to the optical fiber transmitter n2 of the measurement board through optical fiber, and is used to receive the calculation results of the measurement board. The optical fiber transmitter m is connected to the optical fiber receiver m of the power unit and the power unit through optical fiber, and is used to control the conduction and shutdown of the MOSFET.

[0019] Furthermore, each short-circuit branch in the power unit includes an optical fiber receiving and signal driving module, a MOSFET and branch absorption loop module, and a MOSFET conduction display and current limiting module.

[0020] Furthermore, the optical fiber receiving and signal driving module includes an optical fiber receiver and a driving chip for driving the MOSFET to turn on and off.

[0021] Furthermore, the MOSFET and the branch absorption circuit in the branch absorption circuit module are connected in parallel at both ends of the drain-source stage of the MOSFET, and the branch absorption circuit includes a Schottky diode D 2 ,resistance R 4 and capacitors C 2 , Schottky diode D 2 and resistors R 4 After connecting in parallel with the capacitor C 2 When the MOSFET is turned on, the resistor R 4 To discharge the capacitor C 2 The energy stored in the capacitor when the MOSFET is turned off C 2 Absorb the magnetic field energy in the parasitic inductance of the composite busbar and circuit board loop, C 1 、C 2 The choice of capacitance value satisfies the formula:

[0022] (1);

[0023] Where,C 1 Represents the capacitance of the total absorption circuit, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the MOSFET rated voltage, n Indicates the number of short-circuit branches in the power unit, L 1 represents the stray inductance value between the copper cable and the composite busbar. L 2 represents the stray inductance value in a single short-circuit branch. I d(DC) Indicates the continuous DC current rating of the MOSFET.

[0024] Furthermore, the MOSFET conduction display and current limiting module includes a constantan wire resistor R5, a constantan wire resistor R 6 With light-emitting diodes D 3 , Constantan wire resistor R 5 With light-emitting diodes D 3 Then connect it in series with the constantan wire resistor R 6 in parallel.

[0025] Furthermore, the measurement board in the data acquisition unit includes a power supply module, a sensor module and a current comparison module. The power supply module converts 220V AC power into ±15V DC power by the ACDC module to power the sensor; the sensor module includes a thermocouple, a Hall voltage sensor, a Hall current sensor and corresponding peripheral circuits; the current comparison module has a built-in single-chip microcomputer, which compares the current collected by the Hall current sensor with the current threshold that the MOSFET device can withstand, and stops the battery short-circuit process when the threshold is exceeded.

[0026] A method for using a battery external short-circuit test and short-circuit data analysis device comprises the following steps:

[0027] S1: The battery under test is connected to both ends of the copper cable extending from the composite busbar. The head end of the thermocouple in the data acquisition unit is attached to the surface of the battery. The primary side of the Hall voltage sensor is connected to a pair of tabs of the battery under test. The Hall current sensor is connected in series on the copper cable.

[0028] S2: Connect the camera cable, the serial port data cable of the control unit, and the high-speed transmission cable of the acquisition card of the data acquisition unit to the host computer respectively, open the host computer interface, and connect the serial port.

[0029] S3: Collect total battery voltage U 0, and enter the battery's internal resistance in ohms R 0, calculate the minimum number of channels that are turned on;

[0030] When a short circuit begins, the voltage and current in the device satisfy the formula:

[0031] (2);

[0032] U 0 is the initial voltage of the measured battery, that is, the total battery voltage collected, is the total resistance of a single short-circuit branch when the MOSFET is turned on, is the current flowing through a single short-circuited branch, The resistance of the composite busbar and copper cable of the main circuit; is the ohmic internal resistance of the measured battery. Since the DC internal resistance in the actual short-circuit process needs to be measured by short-circuit, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into the formula (2). Replacement of DC internal resistance R DC; is the current flowing through the main circuit, n Indicates the number of short-circuited branches in the power unit.

[0033] Indicates the continuous DC current rating of the MOSFET, which is used to prevent the current flowing through a single short-circuit branch during a short circuit. Due to exceeding the rated value And burning, must meet ≤ , the number of short-circuit branches in the power unit n Satisfy formula (3), that is:

[0034] (3);

[0035] According to formula (3), the short circuit n The minimum value taken N min , that is, the minimum number of channels that are turned on.

[0036] S4: The control unit sends instructions to the power unit by inputting the short-circuit time, cycle, number of short-circuits, acquisition frequency, and the number and serial number of the MOSFETs to be turned on through the host computer.

[0037] S5: After the command is executed, the display interface of the host computer can observe the real-time voltage and current data and waveform of the tested battery, as well as the video image during the battery short circuit process. The data and video are saved synchronously.

[0038] S6: After the command is executed, the temperature measurement data of the tested battery and the video data of the changes in the battery appearance information are continuously recorded.

[0039] S7: Using the measured battery short-circuit data, various electrical characteristics of the battery under short-circuit conditions can be analyzed. The characteristic quantities include the battery DC internal resistance R DC , the rate of change of current over time di / dt Curve, battery AH discharge capacity C d , actual short-circuit time, maximum short-circuit current I max , maximum temperature T max .

[0040] Furthermore, the control unit sends the number of MOSFETs that are turned on in a single short-circuit branch in the form of a square wave to the microcontroller of the current comparison module through the optical fiber transmitter n1 and the optical fiber receiver n1, and converts the current collected by the Hall current sensor into IH The current threshold of the MOSFET device Id(DC) For comparison, let the number of MOSFETs turned on be n ,when When the battery is short-circuited, a stop signal is sent to the control unit through the optical fiber transmitter n2 and the optical fiber receiver n2, so that the MOSFET is turned off in time to stop the battery short-circuit process.

[0041] The minimum number of channels that are turned on can be calculated by the total battery voltage. In the calculation formula of this method, the battery ohmic internal resistance is used. R 0 DC internal resistance of alternative batteries R DC , in the initial stage of actual short circuit, the DC internal resistance of the battery R DC Usually smaller than the ohmic internal resistance measured under normal battery conditions R 0 , resulting in the minimum number of channels turned on measured by formula (2) N min According to formula (2), the smaller the channel conduction number n is, the smaller the current flowing through a single short-circuit branch is. I 支 The larger the current is, the more likely it is to be lost. To prevent the MOSFET from burning out due to overcurrent caused by setting the channel conduction number too small, it is necessary to compare the current in real time. I H The current threshold of the MOSFET device I d(DC) Size, in terms of hardware to achieve MOSFET overcurrent protection, this protection method is a supplement to step S3, playing the role of double insurance.

[0042] Furthermore, in step S7,

[0043] The DC internal resistance of the battery includes ohmic internal resistance and polarization internal resistance. The calculation formula is as follows:

[0044] (4);

[0045] in, R DC is the DC internal resistance of the battery; OCV(SOC) represents the open circuit voltage of the battery when it is not connected to a load. Usually, the average terminal voltage value is obtained by averaging the terminal voltage values ​​that change with capacity when the battery is charged and discharged at 0.05C, that is, the OCV-SOC curve; U is the operating voltage of the battery, I For U The current at the same moment;

[0046] Current rate of change over time di / dt The curve calculation formula is as follows:

[0047] (5);

[0048] in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, k The number of interval points of the current data selected when calculating the rate of change of current over time, Δ t The minimum time interval for the acquisition card to collect current data; is no more than a real number The largest integer;

[0049] Battery AH discharge capacity C d Indicates the amount of electricity discharged by the battery. The calculation formula is as follows:

[0050] (6);

[0051] in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, T d is the time when the short circuit ends, Δ t The minimum time interval for the acquisition card to collect current data.

[0052] Beneficial effects of the present invention:

[0053] The present invention can achieve adjustable short-circuit current and controllable short-circuit time; it can simulate the short-circuit response of a real battery from the start of the short circuit to the fuse blowing protection, and reproduce the short-term high-current scenario. It can be achieved that at the moment the battery short circuit begins, the appearance of the battery is recorded by a camera connected to the device, and the temperature data of the battery surface is recorded by a thermocouple. The busbar is replaced by a composite busbar, and multiple groups of RCD absorption circuits are connected in parallel at both ends of the composite busbar, so that the peak voltage generated by the device when it is turned off at the highest current is smaller than the breakdown voltage at both ends of the MOSFET drain source. The present invention can arbitrarily select the MOSFET that needs to be turned on by controlling the number of MOSFETs that are turned on and off, and has feedback information on whether the MOSFET is successfully turned on, which is beneficial to the inspection and maintenance of the equipment.

[0054] In terms of testing, in addition to being able to replicate short-term, high-current scenarios, the present invention also enables the collection of video monitoring data and temperature data; MOSFET overcurrent and overvoltage protection; flexible selection of MOSFET on and off states; and MOSFET on and off information feedback. In terms of data analysis, the present invention can analyze the short-circuit data of the tested battery, visually displaying the characteristics of the battery at each short-circuit stage, providing a reliable analysis tool for building short-circuit simulation models for battery systems and selecting fuses. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a block diagram of the overall structure of the present invention.

[0056] Figure 2 This is a principle block diagram of the control unit in the present invention.

[0057] Figure 3 This is a structural diagram of the power unit in the present invention.

[0058] Figure 4 This is a principle block diagram of a single short-circuit branch of a power unit in the present invention.

[0059] Figure 5 This is a principle block diagram of the data acquisition unit in the present invention.

[0060] Figure 6 It is the workflow diagram of the host computer in the present invention.

[0061] As shown in the figure:

[0062] 1. Camera, 2. Host computer, 3. Control unit, 31. Serial communication module, 32. Digital signal processing module, 33. Photoelectric conversion module, 4. Power unit, 41. Short-circuit branch, 411. Optical fiber receiving and signal driving module, 412. MOSFET and branch recovery module, 413. MOSFET conduction display and current limiting module, 42. Composite busbar, 43. Copper cable, 44. Total absorption circuit, 5. Battery under test, 6. Data acquisition unit, 61. Measurement board, 62. Acquisition card, 611. Power module, 612. Sensor module, 613. Current comparison module, 614. ACDC module, 615. Thermocouple, 616. Hall voltage sensor, 617. Hall current sensor, 618. AT89C microcontroller, 619. A / D conversion module. 7. RS232 interface, 8. MAX232 level conversion chip, 9. C8051F340 microcontroller, 10. CPLD, 11. Fiber optic transmitter m, 12. Fiber optic receiver m, 13. Fiber optic transmitter n1, 14. Fiber optic receiver n2, 15. Fiber optic receiver n1, 16. Fiber optic receiver n2, 17. MOSFET, 18. Driver chip. DETAILED DESCRIPTION

[0063] In order to clearly illustrate the technical features of this solution, this solution is described below through specific implementation methods.

[0064] A battery external short-circuit test and short-circuit data analysis device comprises a host computer 2, a data acquisition unit 6, a control unit 3 and a power unit 4.

[0065] Host computer 2 and control unit 3 are connected via a serial communication module using an RS232 interface. This RS232 interface requires a level shifter chip to communicate with the microcontroller. These level shifters include the MAX232ESE and the SN74LVC1T45DBVR. The MAX232ESE is a line driver / receiver chip that converts RS232 signal levels from the computer's serial port to the TTL signal levels used by the microcontroller. The SN74LVC1T45DBVR is a dual-power bus transceiver with data transmission capabilities. It converts data sent from the microcontroller and received from the MAX232ESE from +5V to +3.3V.

[0066] Host computer 2 is also electrically connected to camera 1, which monitors the battery's external status. Camera 1 is a high-definition camera with a USB port. The USB port of camera 1 is connected to host computer 2, and images from the USB camera are captured using the Vision Toolkit. The host computer controls the start and end of video file recording.

[0067] Host computer 2 is responsible for data communication with control unit 3, displaying and storing measured battery data and battery short-circuit videos, and analyzing various electrical characteristics of the battery under short-circuit conditions. Developed based on Labview, host computer 2 enables signal communication with control unit 3. By inputting the short-circuit time, cycle, number of short-circuits, acquisition frequency, and the number and serial number of MOSFETs to be turned on, it sends data to the control unit's microcontroller and receives feedback from the control unit. It can control operation and forced shutdown, receive data from acquisition card 62, and monitor voltage, current, and temperature data in real time. It also saves voltage, current, and temperature data under short-circuit conditions in real time. Connecting to camera 1, it can monitor and save battery short-circuit videos in real time. It also calculates various electrical characteristics of the battery under short-circuit conditions, including the battery's DC internal resistance, the rate of change of current over time, the battery's discharge capacity, the actual short-circuit time, the maximum short-circuit current during the battery short-circuit, and the maximum temperature.

[0068] Controlling the battery short-circuit current means controlling the battery short-circuit external resistance. When MOSFET 17 is on, it has an on-state resistance, also known as the drain-source resistance. MOSFET 17 can be considered a pure resistor in this on-state state. Based on the principle that the total resistance decreases when resistors are connected in parallel, the value of the battery short-circuit external resistance can be varied by controlling the number of parallel MOSFETs 17 that are on, thereby achieving different short-circuit currents.

[0069] The short-circuit time is the on-time of MOSFET 17 within a cycle, requiring it to be both on and off simultaneously. The period is the ratio of the short-circuit time to the duty cycle; the number of short-circuits is the number of cycles; the number and number of MOSFETs 17 to be turned on is determined by numbering all MOSFETs 17. First, enter the number of MOSFETs 17 to be turned on, then click the number of the selected MOSFET 17.

[0070] The data acquisition unit 6 is also electrically connected to the host computer 2 and the battery under test 5. It comprises a measurement board 61 and an acquisition card 62, and is used to collect characteristic parameters of the battery short circuit and upload them to the host computer 2. The data acquisition unit 6 primarily collects voltage, current, and temperature data during a battery short circuit, and uploads this data to the host computer 2 in real time. It also provides overcurrent protection for the MOSFET 17. This device can replicate various actual external short-circuit conditions of energy storage batteries.

[0071] The power unit 4 includes 50 identical short-circuit branches 41, a composite busbar 42, and a total absorption loop 44. The composite busbar 42 connects the individual short-circuit branches 41 in parallel, and has the characteristics of short circuit, low impedance, and low inductance, while improving the integration and reliability of the equipment. There are threaded holes on the composite busbar 42, and the short-circuit branch 41 PCB circuit board has nut terminals that match the threaded holes of the composite busbar 42. The composite busbar 42 is connected to the short-circuit branch 41 by screws. A copper cable 43 for connecting to the battery 5 under test is provided on the composite busbar 42. The total absorption loop 44 is connected in parallel to the positive and negative ends of the composite busbar 42. The total absorption loop 44 includes capacitors. C 1 ,resistance R 1 and Schottky diodes D 1 ,resistance R 1 and Schottky diodes D 1 After connecting in parallel with the capacitor C 1 By controlling the on-time and number of MOSFET17, the battery short-circuit current and short-circuit time can be controlled.

[0072] The total absorption circuit 44 in power unit 4, also known as the RCD absorption circuit, is directly connected in parallel across the positive and negative terminals of the composite busbar 42. Composite busbar 42 and the battery under test 5 are connected via a copper cable 43, which has its own stray inductance. When MOSFET 17 is turned off, most of the magnetic field energy in the parasitic inductance of copper cable 43 is absorbed by capacitor C1, thereby reducing the drain-source spike voltage at the time of shutdown and protecting the device.

[0073] The control unit 3 is connected to the power unit 4 and the data acquisition unit 6 through optical fibers. The control unit 3 includes a serial communication module 31, a digital signal processing module 32 and a photoelectric conversion module 33. The serial communication module 31 communicates with the host computer 2; the digital signal processing module 32 includes a single-chip microcomputer and a programmable logic device CPLD10, which calculates and sends logic signals and receives feedback signals transmitted by the data acquisition unit 6; in this embodiment, the single-chip microcomputer in the digital signal processing module 32 serves as a CPU, model C8051F340 single-chip microcomputer 9, which is responsible for receiving and processing instructions transmitted by the host computer 2 and the data acquisition unit 6, and sending the processed signals to the CPLD10; the CPLD10 serves as a complex programmable logic device, model EPM240T100C5N, which is responsible for processing the instructions sent by the single-chip microcomputer and finally sending logic signals acting on the photoelectric conversion module 33; the photoelectric conversion module 33 can achieve electrical isolation between circuit boards and is responsible for signal transmission between the control unit 3, the power unit 4 and the data acquisition unit 6.

[0074] The photoelectric conversion module 33 includes a driver chip, a fiber optic transmitter n113, a fiber optic receiver n214, and multiple fiber optic transmitters m11. Fiber optic transmitter n113 is connected to the measurement board 61 and transmits the number of MOSFETs 17 that are on. Fiber optic receiver n214 is connected to the measurement board 61 via fiber optic transmitter n216 and receives the calculation results from the measurement board 61. Fiber optic transmitters m11 are connected to the power unit 4 via fiber optic receiver m12 and control the on and off state of the MOSFETs 17. The photoelectric conversion module 33 uses the HFBR-1522Z as the fiber optic transmitter and the HFBR-2522Z as the fiber optic receiver.

[0075] Each short-circuit branch in the power unit 4 includes an optical fiber receiving and signal driving module, a MOSFET and branch absorption loop module, and a MOSFET conduction display and current limiting module.

[0076] The optical fiber receiving and signal driving module 411 includes an optical fiber receiver and a driver chip 18 for driving the MOSFET 17 on and off. HFBR-2522Z is ​​used as the optical fiber receiver; IXDI609SIA is used as the MOSFET driver chip 18 to drive the MOSFET 17 on and off.

[0077] The branch absorption circuit in the MOSFET and branch absorption circuit module 412 is connected in parallel at both ends of the drain-source stage of the MOSFET17 to absorb the energy generated by the stray inductance in the composite busbar 42 when the MOSFET17 is turned off, thereby reducing the drain-source voltage spike when the MOSFET17 is turned off.

[0078] The branch absorption circuit includes a Schottky diode D 2 ,resistance R 4 and capacitors C 2 , Schottky diode D 2 and resistors R 4 After connecting in parallel with the capacitor C 2 in series; when MOSFET17 is turned on, the resistor R 4 To discharge the capacitor C 2 The energy stored; when MOSFET17 is turned off, the capacitor C 2 Absorb the magnetic field energy in the parasitic inductance of the composite busbar 42 and the circuit board loop, C 1 、C 2The choice of capacitance value satisfies the formula:

[0079] (1);

[0080] Where, C 1 Represents the capacitance of the total absorption circuit, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the MOSFET rated voltage, n Indicates the number of short-circuit branches in the power unit, L 1 represents the stray inductance value between the copper cable and the composite busbar. L 2 represents the stray inductance value in a single short-circuit branch. I d(DC) Indicates the continuous DC current rating of the MOSFET.

[0081] MOSFET conduction display and current limiting module 413 includes a constantan wire resistor R 5 , Constantan wire resistor R 6 With light-emitting diodes D 3 , Constantan wire resistor R 5 With light-emitting diodes D 3 Then connect it in series with the constantan wire resistor R 6 When the MOSFET is turned on, current flows through the LED D 3 , emitting a light signal determines that the selected MOSFET is in the on state.

[0082] The measurement board 61 in the data acquisition unit 6 includes a power supply module 611, a sensor module 612, and a current comparison module 613. The power supply module 611 converts 220V AC power into ±15V DC power via an ACDC module 614 to power the sensor. The sensor module 612 includes a thermocouple 615, a Hall voltage sensor 616, a Hall current sensor 617, and corresponding peripheral circuits. The current comparison module 613 has a built-in single-chip microcomputer. In this embodiment, the single-chip microcomputer is an AT89C51 single-chip microcomputer 618, which is connected to the Hall current sensor 617 via an A / D conversion module. The current collected by the Hall current sensor 617 can be compared with the current threshold that the MOSFET 17 can withstand. If the threshold is exceeded, the battery short circuit process is stopped.

[0083] The control unit 3 sends the number of MOSFET17 turns on in a single short-circuit branch in the form of a square wave to the microcontroller 618 of the current comparison module 613 through the optical fiber transmitter n113 and the optical fiber receiver n115, and converts the current collected by the Hall current sensor 617 into IH The current threshold of the MOSFET device Id(DC) For comparison, let the number of MOSFETs turned on be n ,when When the battery is short-circuited, a stop signal is sent to the control unit 3 through the optical fiber transmitter n216 and the optical fiber receiver n214, so that the MOSFET is turned off in time to stop the battery short-circuit process.

[0084] A method for using a battery external short-circuit test and short-circuit data analysis device comprises the following steps:

[0085] S1: The battery under test 5 is connected to the two ends of the copper cable extending from the composite busbar 42. The head end of the thermocouple 615 in the data acquisition unit 6 is attached to the surface of the battery under test 5. The primary side of the Hall voltage sensor 616 is connected to a pair of tabs of the battery under test 5. The Hall current sensor 617 is connected in series on the copper cable.

[0086] S2: Connect the camera 1 connection line, the serial port data line of the control unit 3, and the high-speed transmission line of the acquisition card 62 of the data acquisition unit 6 to the host computer 2 respectively, open the interface of the host computer 2, and connect the serial port.

[0087] S3: Collect total battery voltage U 0, and enter the battery's internal resistance in ohms R 0, calculate the minimum number of channels that are turned on;

[0088] When a short circuit begins, the voltage and current in the device satisfy the formula:

[0089] (2);

[0090] U 0 is the initial voltage of the measured battery, that is, the total battery voltage collected, is the total resistance of a single short-circuit branch when the MOSFET is turned on, is the current flowing through a single short-circuited branch, The resistance of the composite busbar and copper cable of the main circuit; is the ohmic internal resistance of the measured battery. Since the DC internal resistance in the actual short-circuit process needs to be measured by short-circuit, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into the formula (2). Replacement of DC internal resistance R DC; is the current flowing through the main circuit, n Indicates the number of short-circuited branches in the power unit.

[0091] Indicates the continuous DC current rating of the MOSFET, which is used to prevent the current flowing through a single short-circuit branch during a short circuit. Due to exceeding the rated value And burning, must meet ≤ , the number of short-circuit branches in the power unit n Satisfy formula (3), that is:

[0092] (3);

[0093] According to formula (3), the short circuit n The minimum value Nmin is the minimum number of channels that are turned on.

[0094] S4: The short-circuit time, cycle, number of short-circuits, acquisition frequency, and the number and serial number of the MOSFETs to be turned on are input through the host computer 2, and the control unit 3 sends an instruction to the power unit 4.

[0095] S5: After the command is executed, the display interface of the host computer 2 can observe the real-time voltage and current data and waveform of the tested battery 5, as well as the video image during the battery short circuit process. The data and video are saved synchronously.

[0096] S6: After the command execution is completed, the temperature measurement data of the tested battery 5 and the video data of the changes in the battery appearance information are continuously recorded.

[0097] S7: Using the measured battery short-circuit data, various electrical characteristics of the battery under short-circuit conditions can be analyzed. The characteristic quantities include the battery DC internal resistance R DC , the rate of change of current over time di / dt Curve, battery AH discharge capacity C d , actual short-circuit time, maximum short-circuit current I max , maximum temperature T max .

[0098] The DC internal resistance of the battery includes ohmic internal resistance and polarization internal resistance, and the calculation formula is as follows:

[0099] (4);

[0100] in, R DC is the DC internal resistance of the battery; OCV(SOC) represents the open circuit voltage of the battery when it is not connected to a load. Usually, the average terminal voltage value is obtained by averaging the terminal voltage values ​​that change with capacity when the battery is charged and discharged at 0.05C, that is, the OCV-SOC curve;U is the operating voltage of the battery, I For U The current at the same moment.

[0101] Current rate of change over time di / dt The curve calculation formula is as follows:

[0102] (5);

[0103] in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, k The number of interval points of the current data selected when calculating the rate of change of current over time, Δ t The minimum time interval for the acquisition card to collect current data; is no more than a real number The maximum integer.

[0104] Battery AH discharge capacity C d Indicates the amount of electricity discharged by the battery. The calculation formula is as follows:

[0105] (6);

[0106] in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, T d is the time when the short circuit ends, Δ t The minimum time interval for the acquisition card to collect current data.

[0107] Of course, the above description is not limited to the above examples. Technical features not described in the present invention can be achieved by or by adopting existing technologies, which will not be described here. The above embodiments and drawings are only used to illustrate the technical solutions of the present invention and are not limitations of the present invention. The present invention is described in detail with reference to the preferred implementation methods. Ordinary technicians in this field should understand that changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention do not depart from the purpose of the present invention and should also fall within the scope of protection of the claims of the present invention.

Claims

1. A battery external short circuit test and short circuit data analysis device, characterized by: Including host computer, data acquisition unit, control unit and power unit; The host computer and the control unit are connected via a serial communication port, and the host computer is also electrically connected to a camera for monitoring the external status of the battery; The data acquisition unit is electrically connected to the host computer and the battery under test respectively. The data acquisition unit includes a measurement board and an acquisition card, which is used to collect battery short-circuit characteristic parameters and upload them to the host computer; The power unit includes n The same short-circuit branches, composite busbars and total absorption circuits are connected in parallel through the composite busbars. The composite busbars are provided with copper cables for connecting to the battery under test. The total absorption circuit is connected in parallel to the positive and negative terminals of the composite busbars. The total absorption circuit includes capacitors. C 1 ,resistance R 1 and Schottky diodes D 1 ,resistance R 1 and Schottky diodes D 1 After connecting in parallel with the capacitor C 1 Series connection; The control unit is connected to the power unit and the data acquisition unit through optical fibers. The control unit includes a serial communication module, a digital signal processing module, and a photoelectric conversion module. The serial communication module communicates with the host computer. The digital signal processing module includes a single-chip microcomputer and a programmable logic device (CPLD), calculates and sends logic signals, and receives feedback signals transmitted by the data acquisition unit. The photoelectric conversion module includes a driver chip, an optical fiber transmitter n1, an optical fiber receiver n2, and multiple optical fiber transmitters m. The optical fiber transmitter n1 is connected to the optical fiber receiver n1 of the measurement board through an optical fiber and is used to transmit the number of MOSFET conduction to the measurement board. The optical fiber receiver n2 is connected to the optical fiber transmitter n2 of the measurement board through an optical fiber and is used to receive the calculation results of the measurement board. The optical fiber transmitter m is connected to the optical fiber receiver m of the power unit through an optical fiber and is used to control the conduction and shutdown of the MOSFET. Each short-circuit branch in the power unit includes an optical fiber receiving and signal driving module, a MOSFET and branch absorption circuit module, and a MOSFET conduction display and current limiting module; the branch absorption circuit in the MOSFET and branch absorption circuit module is connected in parallel at both ends of the drain-source stage of the MOSFET, and the branch absorption circuit includes a Schottky diode D 2 , resistor R4 and capacitor C 2 , Schottky diode D 2 and resistors R 4 After connecting in parallel with the capacitor C 2 When the MOSFET is turned on, the resistor R 4 To discharge the capacitor C 2 The energy stored in the capacitor when the MOSFET is turned off C 2 Absorb the magnetic field energy in the parasitic inductance of the composite busbar and circuit board loop, C 1 、C 2 The choice of capacitance value satisfies the formula: (1)； Where, C 1 Represents the capacitance of the total absorption circuit, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the MOSFET rated voltage, n Indicates the number of short-circuit branches in the power unit, L 1 represents the stray inductance value between the copper cable and the composite busbar. L 2 represents the stray inductance value in a single short-circuit branch. I d(DC) Indicates the continuous DC current rating of the MOSFET.

2. The battery external short-circuit test and short-circuit data analysis device according to claim 1, characterized in that: The optical fiber receiving and signal driving module includes an optical fiber receiver and a driver chip for driving the MOSFET on and off.

3. The battery external short-circuit test and short-circuit data analysis device according to claim 1, characterized in that: MOSFET conduction display and current limiting module including constantan wire resistor R 5 , Constantan wire resistor R 6 With light-emitting diodes D 3 , Constantan wire resistor R 5 With light-emitting diodes D 3 Then connect it in series with the constantan wire resistor R 6 in parallel.

4. The battery external short-circuit test and short-circuit data analysis device according to claim 1, characterized in that: The measurement board in the data acquisition unit includes a power module, a sensor module and a current comparison module. The power module converts 220V AC power into ±15V DC power through the ACDC module to power the sensor; the sensor module includes a thermocouple, a Hall voltage sensor, a Hall current sensor and corresponding peripheral circuits; the current comparison module has a built-in microcontroller that compares the current collected by the Hall current sensor with the current threshold that the MOSFET device can withstand. If the threshold is exceeded, the battery short-circuit process is stopped.

5. A method for using the battery external short-circuit testing and short-circuit data analysis device according to claim 1, characterized in that: The following steps are involved: S1: Connect the battery under test to both ends of the copper cable extending from the composite busbar. The thermocouple head in the data acquisition unit is attached to the battery surface. The primary side of the Hall voltage sensor is connected to a pair of tabs of the battery under test. The Hall current sensor is connected in series on the copper cable. S2: Connect the camera cable, the serial port data cable of the control unit, and the high-speed transmission cable of the acquisition card of the data acquisition unit to the host computer respectively, open the host computer interface, and connect the serial port; S3: Collect total battery voltage , and enter the battery ohmic internal resistance , calculate the minimum number of channels that are turned on; When a short circuit begins, the voltage and current in the device satisfy the formula: (2)； is the initial voltage of the measured battery, that is, the total battery voltage collected, is the total resistance of a single short-circuit branch when the MOSFET is turned on, is the current flowing through a single short-circuited branch, The resistance of the composite busbar and copper cable of the main circuit; is the ohmic internal resistance of the measured battery. Since the DC internal resistance in the actual short-circuit process needs to be measured by short-circuit, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into the formula (2). Replacement of DC internal resistance R DC; is the current flowing through the main circuit, n Indicates the number of short-circuit branches in the power unit; Indicates the continuous DC current rating of the MOSFET, which is used to prevent the current flowing through a single short-circuit branch during a short circuit. Due to exceeding the rated value And burning, must meet ≤ , the number of short-circuit branches in the power unit n Satisfy formula (3), that is: (3)； By using formula (3), we can get the short circuit n The minimum value taken N min, that is, the minimum number of channels that are turned on; S4: The control unit sends instructions to the power unit through the input of short-circuit time, cycle, number of short-circuits, acquisition frequency, and the number and serial number of the MOSFETs to be turned on via the host computer; S5: After the command is executed, the display interface of the host computer can observe the real-time voltage and current data and waveform of the tested battery, as well as the video image during the battery short circuit process. The data and video are saved synchronously; S6: After the command is executed, the temperature measurement data of the tested battery and the video data of the changes in the battery appearance information are continuously recorded; S7: Using the measured battery short-circuit data, various electrical characteristics of the battery under short-circuit conditions can be analyzed. The characteristic quantities include the battery DC internal resistance R DC , the rate of change of current over time di / dt Curve, battery AH discharge capacity C d , actual short-circuit time, maximum short-circuit current I max , maximum temperature T max .

6. The method for using the battery external short-circuit test and short-circuit data analysis device according to claim 5, characterized in that: The control unit sends the number of MOSFETs that are turned on in a single short-circuit branch in the form of a square wave to the microcontroller of the current comparison module through the optical fiber transmitter n1 and the optical fiber receiver n1, and converts the current collected by the Hall current sensor into IH The current threshold of the MOSFET device Id(DC) For comparison, let the number of MOSFETs turned on be n ,when When the battery is short-circuited, a stop signal is sent to the control unit through the optical fiber transmitter n2 and the optical fiber receiver n2, so that the MOSFET is turned off in time to stop the battery short-circuit process.

7. The method for using the battery external short-circuit test and short-circuit data analysis device according to claim 5, characterized in that: In step S7, The DC internal resistance of the battery includes ohmic internal resistance and polarization internal resistance. The calculation formula is as follows: (4)； in, R DC is the DC internal resistance of the battery; OCV(SOC) represents the open circuit voltage of the battery when it is not connected to a load. Usually, the average terminal voltage value is obtained by averaging the terminal voltage values ​​that change with capacity when the battery is charged and discharged at 0.05C, that is, the OCV-SOC curve; U is the operating voltage of the battery, I For U The current at the same moment; Current rate of change over time di / dt The curve calculation formula is as follows: (5)； in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, k The number of interval points of the current data selected when calculating the rate of change of current over time, Δ t The minimum time interval for the acquisition card to collect current data; is no more than a real number The largest integer; Battery AH discharge capacity C d Indicates the amount of electricity discharged by the battery. The calculation formula is as follows: (6)； in, i ( t ) is the current of the battery at a certain moment, i (0) is the current of the battery at the initial moment of short circuit, n is the total number of short-circuit current collection points, T d is the time when the short circuit ends, Δ t The minimum time interval for the acquisition card to collect current data.

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