Battery external short circuit test and short circuit data analysis device and method

Abstract

The invention relates to the technical field of battery testing, in particular to a battery external short circuit testing and short circuit data analysis device and method, and the device comprises an upper computer, a data collection unit, a control unit and a power unit. The upper computer is in communication connection with the control unit through a serial port, and meanwhile, the upper computer is electrically connected with the camera; the data acquisition unit is electrically connected with the upper computer and the tested battery, and comprises a measuring plate and an acquisition card; the power unit comprises n identical short-circuit branches, a composite busbar and a total absorption loop; the control unit is in communication connection with the power unit and the data acquisition unit through optical fibers. According to the invention, the short-circuit response of a real battery in the time from short circuit to fuse protection of a fuse can be simulated, and the short-circuit current and the short-circuit time can be controlled; the battery short-circuit data is analyzed, the characteristics of the battery in each short-circuit stage are displayed, and a reliable analysis tool is provided for selection and parameter identification of a battery electrical model.

Description

Technical Field

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

[0002] As a green energy storage method, lithium-ion batteries have the characteristics of high energy density, long life, fast charging, and environmental protection. 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 have the characteristics of high voltage level and large capacity. Once an external short circuit occurs, it is very easy to cause large-scale thermal runaway, thus causing serious safety accidents. Therefore, it is necessary to carry out scientific and reasonable external short circuit protection design for the battery system.

[0003] At present, the following problems exist 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 measures in battery systems usually adopt the method of step-by-step coordination of fuses and the battery management system BMS. The battery has the characteristics of high discharge rate and short discharge time from the beginning of short circuit to the fuse blowing protection. In practical applications, the external short-circuit protection time of the battery system is in milliseconds, and the short-circuit current is thousands or even tens of thousands of amperes. In a laboratory environment, the equipment that can discharge the battery at a high rate and can be used commercially is the battery charging and discharging equipment and the large short-circuit test machine, but both of these equipment have their own 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 how the short-circuit current changes over time. From the perspective of current size and current changes over time, it does not meet the requirements of external short-circuit protection experiments. Large-scale short-circuit testing machines can truly show the relationship between short-circuit current and time, but the contactor breaking time is in seconds, which is mainly used for uncontrolled short-circuit experiments. When a fuse 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, it is difficult for any external short-circuit device to ensure the safety of external short-circuit testing, and the test has huge risks and costs; at the same time, there is a lack of effective test and analysis methods, and the battery system external short-circuit simulation model and calculation analysis tools have not been established. In order to simulate the short-circuit response of a real battery from the beginning of the short circuit to the fuse blowing protection, and to reproduce the short-term high-current scenario, it is necessary to build a time-controllable and current-adjustable external short-circuit experimental device. At the same time, based on this experimental platform, the short-circuit characteristics of lithium-ion batteries at different time and current scales are analyzed, and on this basis, a battery system external short-circuit protection simulation model and calculation analysis tools are established. This has important practical engineering significance for the damage analysis of high-rate batteries and the selection of fuses.

[0007] At present, the external short-circuit test of batteries is mainly carried out through battery charging and discharging equipment, large short-circuit test machines and battery external short-circuit test platforms. Due to the limitation of the number of equipment channels, battery charging and discharging equipment cannot apply a discharge current of several thousand amperes as the short-circuit current of the battery; secondly, the discharge current provided by the battery charging and discharging equipment is controlled by the equipment itself, which fails to show the real short-circuit state of the battery.

[0008] Large-scale short-circuit testing machines can simulate the actual short-circuit state of a battery, but the contactor breaking time is in seconds, and destructive short-circuit tests are generally performed. Batteries are disposable items, and the experimental cost is high. In addition, the size 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 make the short-circuit current adjustable and the short-circuit time controllable by controlling the on and off of multiple parallel MOSFETs, but its temperature acquisition function relies on professional equipment and is not controlled by a single software; at the hardware level, the equipment does not have overcurrent protection for MOSFETs; the MOSFET units are connected in parallel using 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, the MOSFET will easily break down, thereby damaging the equipment; the number of MOSFET on and off can be controlled by a program, but the MOSFET that needs to be turned on cannot be selected arbitrarily, and the device does not have feedback information on whether the MOSFET is successfully turned on, which is not conducive to the inspection and maintenance of the equipment.

[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 and analysis tools for the battery system.

[0011] The above three devices can only record preliminary short-circuit data. The selection of simulation models still requires the use of third-party programming tools to extract and analyze short-circuit data, which is inefficient. In addition, the above three devices are unable to perform synchronous video monitoring of the battery status and require an external camera, which has poor synchronization. Summary of the invention

[0012] In view of the deficiencies in the prior art, the present invention provides a battery external short-circuit test and short-circuit data analysis device and method, which can simulate the short-circuit response of a real battery from the start of short circuit to the blowing of a fuse, so that the short-circuit current can be adjusted and the short-circuit time can be controlled; it can analyze the battery short-circuit data and intuitively display the characteristics of the battery at each stage of short circuit, providing a reliable analysis tool for the selection of battery electrical models and parameter identification.

[0013] The present invention is achieved through the following technical solutions: 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; The host computer is connected to the control unit via a serial communication port, and the host computer is also electrically connected to a camera for monitoring the external state of the battery.

[0014] The data acquisition unit is electrically connected to the host computer and the battery under test respectively. The data acquisition unit includes a measuring board and an acquisition card, which are used to collect the short-circuit characteristic parameters of the battery and upload them to the host computer.

[0015] The power unit includes n The short-circuit branches are connected in parallel through the composite busbar. The composite busbar is provided with a copper cable for connecting to the battery under test. The total absorption circuit is connected in parallel to the positive and negative ends of the composite busbar. 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 capacitor C 1 Series connection.

[0016] The control unit is respectively connected to the power unit and the data acquisition unit through optical fibers, and 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 measuring board through optical fiber, and is used to transmit the number of MOSFET conduction to the measuring board; the optical fiber receiver n2 is connected to the optical fiber transmitter n2 of the measuring board through optical fiber, and is used to receive the calculation result of the measuring board; the optical fiber transmitter m is connected to the power unit through optical fiber and the optical fiber receiver m of the power unit, and is used to control the conduction and shutdown of the MOSFET.

[0017] 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.

[0018] 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.

[0019] Furthermore, 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 ,resistance R 4 and capacitor C 2 , Schottky diode D 2 and resistor R 4 After connecting in parallel with capacitor C 2 When the MOSFET is turned on, the resistor R 4 To discharge 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 the circuit board loop, C 1 、C 2 The choice of capacitor value satisfies the formula: (1); In the formula, C 1Represents the capacitance of the total absorption loop, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the rated voltage of MOSFET, 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.

[0020] Furthermore, the MOSFET conduction display and current limiting module includes a constantan wire resistor R5, a constantan wire resistor R 6 With LED D 3 , Constantan wire resistor R 5 With LED D 3 Connect in series with constantan wire resistor R 6 in parallel.

[0021] Furthermore, 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 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 is equipped with a 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.

[0022] A method for using a battery external short circuit test and short circuit data analysis device comprises the following steps: S1: The battery under test is connected to the two 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 pole ears of the battery under test, and the Hall current sensor is connected in series on the copper cable.

[0023] S2: Connect the camera connection 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.

[0024] S3: Collect the total battery voltage U 0, and enter the battery's ohmic internal resistance R 0, calculate the minimum number of channels that are turned on; When the short circuit starts, the voltage and current in the device satisfy the formula: (2); 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-circuiting, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into 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.

[0025] 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. Exceeding the rated value And burning, need to meet ≤ , the number of short-circuit branches in the power unit n Satisfies formula (3), that is: (3); According to formula (3), the short circuit n The minimum value taken N min , which is the minimum number of channels that are turned on.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 .

[0030] Furthermore, the control unit sends the number of MOSFET conduction of 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 the current collected by the Hall current sensor is 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.

[0031] The minimum number of channels that are turned on can be calculated using the total battery voltage. In this method, the battery ohmic internal resistance is used in the calculation formula. 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 number of channel conduction 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 that the MOSFET will burn out due to overcurrent. I H The current threshold of the MOSFET device I d(DC) Size, in terms of hardware, MOSFET over-current protection is achieved. This protection method is a supplement to step S3 and plays a double insurance role.

[0032] Further, 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 DCis 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 terminal voltage value that changes with the capacity when the battery is charged and discharged at 0.05C is averaged to obtain the average terminal voltage value, that is, the OCV-SOC curve; U is the operating voltage of the battery, I For U The current at the same moment; Current change rate 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 collecting current data by the acquisition card; is not more than a real number The largest integer of ; 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.

[0033] Beneficial effects of the present invention: 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 short circuit to the blown fuse protection, and reproduce the short-time high current scenario. It can be realized that at the moment when the battery short circuit begins, the appearance state 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 less than the breakdown voltage at both ends of the MOSFET drain source. The present invention can control the number of MOSFETs that are turned on and off, and can also arbitrarily select the MOSFET that needs to be turned on, and has feedback information on whether the MOSFET is successfully turned on, which is beneficial to the inspection and maintenance of the equipment.

[0034] In terms of testing, in addition to being able to reproduce short-term high-current scenarios, the present invention can also collect video monitoring data and temperature data; protect MOSFET from overcurrent and overvoltage; flexibly select MOSFET on and off; and provide information feedback on MOSFET on and off. In terms of data analysis, the present invention can analyze the short-circuit data of the tested battery, intuitively display the characteristics of the battery at each stage of the short circuit, and provide a reliable analysis tool for the construction of a short-circuit simulation model outside the battery system and the selection of fuses. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a block diagram of the overall structure of the present invention.

[0036] Figure 2 It is a principle block diagram of the control unit in the present invention.

[0037] Figure 3 It is a structural diagram of the power unit in the present invention.

[0038] Figure 4 It is a principle block diagram of a single short-circuit branch of a power unit in the present invention.

[0039] Figure 5 It is a principle block diagram of the data acquisition unit in the present invention.

[0040] Figure 6 It is the working flow chart of the host computer in the present invention.

[0041] As shown in the figure: 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 loop, 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 single chip microcomputer, 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

[0042] In order to clearly illustrate the technical features of this solution, this solution is described below through a specific implementation method.

[0043] 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.

[0044] The host computer 2 and the control unit 3 are connected via serial communication. The serial communication module uses the RS232 interface. The RS232 interface needs to communicate with the microcontroller through a level conversion chip. The level conversion chips include MAX232ESE and SN74LVC1T45DBVR. MAX232ESE is a line driver / receiver chip that is mainly used to convert the RS232 signal level of the computer's serial port to the TTL signal level used by the microcontroller. SN74LVC1T45DBVR is a dual-power bus transceiver with data transmission characteristics. It can convert the data sent by the microcontroller and the data received from MAX232ESE from +5V to +3.3V.

[0045] The host computer 2 is also electrically connected to a camera 1 for monitoring the external state of the battery. The camera 1 is a high-definition camera with a USB interface. The USB interface of the camera 1 is connected to the host computer 2, and the USB camera image is collected through the Vision toolkit. The start and end of the video file recording are controlled by the host computer.

[0046] The host computer 2 is responsible for data communication with the control unit 3, displaying and storing the measured battery data and battery short-circuit video, and analyzing various electrical characteristic quantities under the battery short-circuit state. The host computer 2 is developed based on Labview, and can realize signal communication with the control unit 3. By inputting the short-circuit time, cycle, number of short-circuit times, acquisition frequency, and the number and number of MOSFETs required to be turned on, the data is sent to the single-chip microcomputer of the control unit, and the feedback data of the control unit is received; it can control operation and forced shutdown; realize the function of receiving data from the acquisition card 62, and monitor the voltage, current, and temperature data in real time; save the voltage, current, and temperature data under the short-circuit state in real time; connect with the camera 1, and can monitor and save the battery short-circuit video in real time; calculate various electrical characteristics under the battery short-circuit state, and the characteristic quantities include the battery DC internal resistance, the current change rate over time, the battery discharge capacity, the actual short-circuit time, the maximum short-circuit current during the battery short-circuit, and the maximum temperature.

[0047] Controlling the short-circuit current of the battery means controlling the short-circuit external resistance of the battery. When MOSFET17 is turned on, it will have an on-state resistance, that is, the drain-source resistance. When MOSFET17 is turned on, it can be regarded as a pure resistance. According to the principle that the total resistance of resistors in parallel becomes smaller, the resistance value of the short-circuit external resistance of the battery can be changed by controlling the number of parallel MOSFET17s that are turned on, thereby obtaining short-circuit currents of different sizes.

[0048] The short-circuit time is the conduction time of MOSFET17 in one cycle, and it needs to be turned on and off at the same time. The cycle 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 MOSFET17 to be turned on, that is, all MOSFET17 are numbered, first enter the number of MOSFET17 to be turned on, and then click the selected MOSFET17 number.

[0049] The data acquisition unit 6 is also electrically connected to the host computer 2 and the battery under test 5, respectively. The data acquisition unit 6 includes a measurement board 61 and an acquisition card 62, which are used to collect the characteristic parameters of the battery short circuit and upload them to the host computer 2. The data acquisition unit 6 mainly collects the voltage, current, and temperature data when the battery is short-circuited, and uploads the data to the host computer 2 in real time, and can also perform overcurrent protection on the MOSFET 17. The device can reproduce various actual external short-circuit states of the energy storage battery.

[0050] 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. The composite busbar 42 is provided with threaded holes, 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. The composite busbar 42 is provided with a copper cable 43 for connecting to the battery 5 under test. 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 a capacitor C 1 ,resistance R 1 and Schottky diodes D 1 ,resistance R 1 and Schottky diodes D 1 After connecting in parallel with capacitor C 1 By controlling the conduction time and quantity of MOSFET17, the short-circuit current and short-circuit time of the battery can be controlled.

[0051] The total absorption circuit 44 in the power unit 4, i.e., the RCD absorption circuit, is directly connected in parallel to the positive and negative ends of the composite busbar 42. The composite busbar 42 is connected to the battery 5 under test via a copper cable 43, which has stray inductance. When the MOSFET 17 is turned off, most of the magnetic field energy in the parasitic inductance in the copper cable 43 will be absorbed by the capacitor C1, thereby reducing the drain-source peak voltage at the turn-off moment, thereby protecting the device.

[0052] The control unit 3 is respectively 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, and the model is a C8051F340 single-chip microcomputer 9, which is responsible for receiving and processing the 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, and the model is EPM240T100C5N, which is responsible for processing the instructions sent by the single-chip microcomputer, and finally sends 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.

[0053] The photoelectric conversion module 33 includes a driver chip, a fiber optic transmitter n113, a fiber optic receiver n214, and a plurality of fiber optic transmitters m11. The fiber optic transmitter n113 is connected to the measuring board 61 to transmit the number of MOSFET 17 conduction to the measuring board 61. The fiber optic receiver n214 is connected to the measuring board 61 through the fiber optic transmitter n216 to receive the calculation result of the measuring board 61. The fiber optic transmitter m11 is connected to the power unit 4 through the fiber optic receiver m12 to control the conduction and shutdown of the MOSFET 17. The photoelectric conversion module 33 uses HFBR-1522Z as a fiber optic transmitter and HFBR-2522Z as a fiber optic receiver.

[0054] 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.

[0055] The optical fiber receiving and signal driving module 411 includes an optical fiber receiver and a driving chip 18 for driving the MOSFET 17 to turn on and off. HFBR-2522Z is ​​used as the optical fiber receiver; IXDI609SIA is used as the driving chip 18 of the MOSFET to drive the MOSFET 17 to turn on and off.

[0056] 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 MOSFET17 to absorb the energy generated by the stray inductance in the composite busbar 42 when MOSFET17 is turned off, thereby reducing the drain-source voltage spike when MOSFET17 is turned off.

[0057] The branch absorption circuit includes a Schottky diode D 2 ,resistance R 4 and capacitor C 2 , Schottky diode D 2 and resistor R 4 After connecting in parallel with capacitor C 2 When MOSFET17 is turned on, the resistor R 4 To discharge 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 capacitor value satisfies the formula: (1); In the formula, C 1 Represents the capacitance of the total absorption loop, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the rated voltage of MOSFET, 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.

[0058] MOSFET conduction display and current limiting module 413 includes constantan wire resistor R 5 , Constantan wire resistor R 6 With LED D 3 , Constantan wire resistor R 5 With LED D 3 Connect in series with constantan wire resistor R 6 When the MOSFET is turned on, current flows through the LED D 3 , the emission of a light signal determines that the selected MOSFET is in the on state.

[0059] The measuring board 61 in the data acquisition unit 6 includes a power module 611, a sensor module 612 and a current comparison module 613. The power module 611 converts 220V AC power into ±15V DC power by 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 is equipped with a 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 through an A / D conversion module. The current collected by the Hall current sensor 617 can be compared with the current threshold that the MOSFET17 can withstand. If the threshold is exceeded, the battery short circuit process is stopped.

[0060] The control unit 3 sends the number of MOSFET17 conduction of a single short-circuit branch in the form of a square wave to the single-chip microcomputer 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.

[0061] A method for using a battery external short circuit test and short circuit data analysis device comprises the following steps: S1: The battery 5 under test 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 5 under test, the primary side of the Hall voltage sensor 616 is connected to a pair of pole ears of the battery 5 under test, and the Hall current sensor 617 is connected in series on the copper cable.

[0062] 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.

[0063] S3: Collect the total battery voltage U 0, and enter the battery's ohmic internal resistance R 0, calculate the minimum number of channels that are turned on; When the short circuit starts, the voltage and current in the device satisfy the formula: (2); 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-circuiting, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into 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.

[0064] 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. Exceeding the rated value And burning, need to meet ≤ , the number of short-circuit branches in the power unit n Satisfies formula (3), that is: (3); According to formula (3), the short circuit n The minimum value Nmin is the minimum number of channels that are turned on.

[0065] 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 instructions to the power unit 4.

[0066] S5: After the command is executed, the display interface of the host computer 2 can observe the data and waveform of the real-time voltage and current of the tested battery 5, as well as the video image during the battery short circuit process, and the data and video are saved synchronously.

[0067] S6: After the command is executed, the temperature measurement data of the tested battery 5 and the video data of the changes in the battery appearance information are continuously recorded.

[0068] 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 .

[0069] Among them: The DC internal resistance of the battery includes ohmic internal resistance and polarization internal resistance, and 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 terminal voltage value that changes with the capacity when the battery is charged and discharged at 0.05C is averaged to obtain the average terminal voltage value, that is, the OCV-SOC curve; U is the operating voltage of the battery, I For U The current at the same time.

[0070] Current change rate 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 collecting current data by the acquisition card; is not more than a real number The maximum integer.

[0071] 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.

[0072] 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 using existing technologies, which will not be described here. The above embodiments and drawings are only used to illustrate the technical scheme 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 in that: It includes 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 also electrically connected to a camera for monitoring the external state 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 measuring board and an acquisition card, which are used to collect the short-circuit characteristic parameters of the battery and upload them to the host computer; The power unit includes n The short-circuit branches are connected in parallel through the composite busbar. The composite busbar is provided with a copper cable for connecting to the battery under test. The total absorption circuit is connected in parallel to the positive and negative ends of the composite busbar. 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 capacitor C 1 Series connection; The control unit is respectively connected to the power unit and the data acquisition unit through optical fibers, and 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 measuring board through optical fiber, and is used to transmit the number of MOSFET conduction to the measuring board; the optical fiber receiver n2 is connected to the optical fiber transmitter n2 of the measuring board through optical fiber, and is used to receive the calculation result of the measuring board; the optical fiber transmitter m is connected to the optical fiber receiver m of the power unit through optical fiber, and is used to control the conduction and shutdown of the MOSFET.

2. The battery external short circuit test and short circuit data analysis device according to claim 1, characterized in that: 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.

3. The battery external short circuit test and short circuit data analysis device according to claim 2, characterized in that: 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.

4. The battery external short circuit test and short circuit data analysis device according to claim 2, characterized in that: 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. The branch absorption circuit includes a Schottky diode. D 2 , resistor R4 and capacitor C 2 , Schottky diode D 2 and resistor R 4 After connecting in parallel with capacitor C 2 When the MOSFET is turned on, the resistor R 4 To discharge 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 the circuit board loop, C 1 、C 2 The choice of capacitor value satisfies the formula: (1)； In the formula, C 1 Represents the capacitance of the total absorption loop, C 2 Represents the capacitance in the branch absorption circuit, U ds Indicates the rated voltage of MOSFET, 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.

5. The battery external short circuit test and short circuit data analysis device according to claim 2, characterized in that: MOSFET conduction display and current limiting module including constantan wire resistor R 5 , Constantan wire resistor R 6 With LED D 3 , Constantan wire resistor R 5 With LED D 3 Connect in series with constantan wire resistor R 6 in parallel.

6. 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 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.

7. A method for using the battery external short-circuit test and short-circuit data analysis device according to claim 1, characterized in that: The following steps are involved: S1: The battery under test is connected to the two 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, and the Hall current sensor is connected in series on the copper cable; S2: Connect the camera connection 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 the total battery voltage , and enter the battery ohmic internal resistance , calculate the minimum number of channels that are turned on; When the short circuit starts, the voltage and current in the device satisfy the formula: (2)； is the measured battery initial voltage, 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-circuiting, the ohmic internal resistance provided by the battery manufacturer or measured by the battery charging and discharging equipment is usually converted into 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. Exceeding the rated value And burning, need to meet ≤ , the number of short-circuit branches in the power unit n Satisfies 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 turned on; S4: The control unit sends instructions to the power unit through the input of the short-circuit time, cycle, number of short-circuit times, acquisition frequency, and the number and serial number of the MOSFETs to be turned on by 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 .

8. The method for using the battery external short circuit test and short circuit data analysis device according to claim 7, characterized in that: The control unit sends the number of MOSFET conduction of 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.

9. The method for using the battery external short circuit test and short circuit data analysis device according to claim 7, 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 terminal voltage value that changes with the capacity when the battery is charged and discharged at 0.05C is averaged to obtain the average terminal voltage value, that is, the OCV-SOC curve; U is the operating voltage of the battery, I For U The current at the same moment; Current change rate 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 collecting current data by the acquisition card; is not more than a real number The largest integer of ; 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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