A testing method for the reuse of retired car batteries

Abstract

This Hong Kong-based short-term disclosure discloses a testing method for reusing retired automotive batteries, comprising: Step 1, preliminary testing of the battery to determine its condition; Step 2, measuring the open-circuit voltage of the battery; Step 3, charging each battery cell to its full voltage; Step 4, calculating the actual capacity of the battery; Step 5, recharging the battery to its full voltage; Step 6, measuring the battery's internal resistance and self-discharge effect; Step 7, connecting the batteries in series to form a battery pack; Step 8, using a battery management system (BMS) to balance the voltage of all cells in the battery pack to the same value, and installing the battery and BMS control board into a battery cabinet. This testing method is a universal testing method applicable to different models of retired batteries, improving the testing efficiency of retired batteries and reducing testing costs.

Description

Specification 1 A Test Method for Reusing Retired Automotive Batteries Technical Field This Hong Kong short-term research relates to the fields of energy storage technology research and electrical engineering technology, and particularly to a test method for reusing retired automotive batteries. Background Technology The rapid upgrading and iteration of electric vehicles has brought about the problem of waste battery disposal. The replaced waste batteries are usually only inadequate in performance to meet automotive specifications, but their health can still support other uses. Studies have shown that retired electric vehicle batteries still have 80% health. Existing methods for handling waste automotive batteries usually involve direct material recycling. Due to the differences in battery management systems among different batteries, and the technical and legal barriers protecting battery management systems, there are high barriers to reusing different models of waste automotive batteries. Existing standards such as UL1974 only provide operational guidelines for the reuse of retired batteries; currently, there is still a lack of a systematic and specifically implementable test method for reusing different models of retired batteries. To address this critical issue, this Hong Kong short-term study proposes a testing method for the reuse of retired automotive batteries of different models. This method enables these retired batteries to be combined and safely used in energy storage battery cabinets, improving the economic efficiency of retired batteries and reducing the environmental burden of material recycling. The specific technical solution is as follows: A test method for reusing retired automotive batteries includes the following steps: Step 1: After the batteries are collected, a preliminary test is performed to determine their condition; Step 2: Measure the open-circuit voltage of the battery: Connect a voltmeter to the positive and negative terminals of each cell in the battery pack, read the cell voltage, confirm whether the cell is overcharged (too high) or over-discharged (too low), and record the voltage data of all cells in a battery; Step 3: Charge each cell of the battery independently to full voltage. The charging adopts a standard charging procedure, i.e., constant current charging first, followed by constant voltage charging. The DC power output voltage during the charging process can be adjusted according to the chemical type of the retired battery; Step 4: After the battery is fully charged, connect it to a load via a circuit board. Measure the circuit board to control the battery discharge to the termination voltage value, thereby calculating the actual capacity of the battery; Step 5: Repeat the operation of Step 3 to recharge the battery to full voltage; Step 6: Measure the battery's internal resistance and self-discharge effect; Step 7: Connect the batteries in series to form a battery pack, and use the BMS control board to control the cells within the battery pack. Step 8: Use the BMS to balance the voltage of all cells in the battery pack to the same value, and then install the batteries and BMS control board into the battery cabinet. Furthermore, the preliminary inspection in Step 1 includes: checking the integrity of the battery surface to confirm whether there are any abnormalities such as damage, deformation, bending, bulging, and / or leakage. If any abnormalities are found, the battery will not be used.Further, in step 2, during the open-circuit voltage measurement, the nominal voltage, full-charge voltage, and termination voltage of the retired battery are obtained based on the battery's own information. The actual measured cell voltage is compared with the battery's nominal voltage, full-charge voltage, and termination voltage to determine whether overcharging or over-discharging has occurred. Further, when the retired battery is a nickel-cobalt-manganese lithium battery, step 3 includes: Step 3.1 Constant current charging: The output voltage of the DC adjustable power supply is set to 4.0V, and the current is set to 10A. When the battery voltage has not reached 4.0V, the DC adjustable power supply will charge the battery with a fixed current of 10A based on the actual battery voltage; Step 3.2 Constant voltage charging: After the battery voltage reaches the full-charge voltage, it enters constant voltage charging mode. At this time, the fixed voltage output of the DC adjustable power supply is 4.0V, and the current decreases as the battery gradually fills. When the current decreases to 0.1A, the battery can be considered fully charged. Furthermore, step 4 of measuring the circuit board includes: the measuring circuit board adopts a modular design, consisting of a main circuit and a control circuit. The main circuit connects the battery and the load, and is controlled by the control circuit via a metal-oxide-semiconductor field-effect transistor (MOSFET). The control circuit uses an ESP32 microcontroller, which is connected to the main circuit board via GPIO pin 32. The microcontroller reads the battery voltage and current data via GPIO and controls the MOSFET to control the opening and closing of the main circuit. During the discharge process, the microcontroller reads the battery output voltage and output current in real time via GPIO and integrates them over time to calculate the battery capacity. When the microcontroller detects that the battery voltage has reached a low voltage of 3.3V, it changes the gate voltage of the MOSFET to open the main circuit and terminate the discharge. Furthermore, in step 4, the microcontroller runs a lightweight web server based on the Linux system, which can be accessed via a wireless access point. After the complete discharge process, the server records the calculated battery capacity and records the battery capacity value in the battery management system (BMS) as the basis for calculating battery health.Further, the measurement steps in step 6 include: Step 6.1, Measuring internal resistance: Fully charge the battery at room temperature, let it stand for 30 minutes to 4 hours, discharge it to 80-90% capacity with a constant current I1, then instantaneously discharge it for 1 to 10 seconds with a current I2, repeating this five times. Record the voltage V1i, V2i and the current values ​​I1i, I2i for each measurement, and calculate using the formula R=(V1i-V2i) / (I2i-I1i), where i=1,2,3,4,5; Step 6.2, Measuring self-discharge: Fully charge the battery as in step 3, and let it stand at room temperature (25°C) for at least one day. Measure the open-circuit voltage of the battery 5 minutes, 1 hour, and 24 hours after the start of the test. A voltage drop of no more than 0.02V at 5 minutes is considered normal, a drop of no more than 0.03V at 1 hour is considered normal, and a drop of no more than 0.05V at 24 hours is considered normal. This is within a reasonable range. Further, in step 7, N batteries are connected in series to form a battery pack, N≥4. One BMS control board controls M cells, M≥2 / N. The BMS control board consists of a main circuit, a circuit controller, and a signal circuit. The main circuit connects different cells and is responsible for voltage balancing between them. A GPIO 40-pin slot is reserved on the main board for connection to the circuit controller. Further, in step 7, the controller controls the current of the main circuit via a MOSFET connected to the main circuit. The controller communicates via a GPIO interface, using the MODBUS protocol and an RS485 physical interface. Further, in step 7, the BMS control board receives pulse width modulation signals from the circuit controller. When a signal is received, cell voltage balancing begins; when the signal is disconnected, cell voltage balancing stops. When the signal is high, the MOSFET is on; when the signal is low, the MOSFET is off. This short-term testing method for the reuse of retired automotive batteries, proposed in Hong Kong, clarifies the various operations from the recycling of retired batteries (HK 30134886 A, Instruction Manual 4) to the completion of testing, as well as the key indicators measured during these operations. After following this method, the following indicators required for reuse can be measured: open-circuit voltage, short-circuit current, self-discharge effect, battery internal resistance, battery capacity, and battery health. These indicators not only serve as the basis for determining whether a battery can be reused but also provide information needed by the subsequent Battery Management System (BMS).Brief Description of the Drawings To more clearly illustrate the technical solutions in the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention, wherein: Figure 1 is a flowchart of the test method for reusing retired automobile batteries; Figure 2 is a schematic diagram of the battery series connection embodiment in step 7. Detailed Description of the Embodiments The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The structures, proportions, sizes, etc., shown in the drawings are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention. Meanwhile, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of implementation in Hong Kong in the short term. Changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of implementation in Hong Kong in the short term. This Hong Kong short term proposes a testing method for the reuse of retired automotive batteries. As shown in Figure 1, the testing method includes the following steps: Step 1: After the batteries are collected, a preliminary inspection is conducted to determine their condition. Specifically, the preliminary inspection includes: Step 1.1: Inspecting the integrity of the battery surface to confirm whether there is any damage, deformation, bending, bulging, or leakage. If any abnormalities are found, the battery should not be used. Step 2: Measuring the open-circuit voltage of the battery. The specific method is to use a voltmeter connected to the positive and negative terminals of each cell in the battery pack to read the cell voltage. Confirm whether the cell voltage is too high (overcharged) or too low (over-discharged). The voltage data of all cells in a battery are recorded. In the open-circuit voltage measurement in step 2, the nominal voltages of different battery systems differ significantly. Therefore, based on the information of the retired battery itself, the nominal voltage, full-charge voltage, and termination voltage of the battery can be determined. Based on this and the actual measured cell voltages, it can be determined whether overcharging or over-discharging has occurred. In step 3, each battery cell is charged independently. The charging adopts a standard charging procedure, first constant current charging, then constant voltage charging. Taking a nickel-cobalt-manganese lithium battery as an example, the specific steps are: Step 3.1, constant current charging. Set the output voltage of the DC adjustable power supply to 4.0V and the current to 10A.When the battery voltage has not reached 4.0V, the DC adjustable power supply will charge the battery with a fixed current of 10A based on the actual battery voltage. Step 3.2, constant voltage charging. After the battery voltage reaches the full charge voltage, it enters the constant voltage charging mode. At this time, the fixed voltage output of the DC adjustable power supply is 4.0V, and the current decreases as the battery gradually fills. When the current decreases to 0.1A, the battery can be considered fully charged. It should be noted that, based on the chemical properties of the battery itself, a series of key voltages of the battery are mainly determined by the electrochemical potential difference between the positive and negative electrode materials. Therefore, although a nickel-cobalt-manganese lithium battery is used as an example in step 3, this method can actually be used for batteries of different chemical types. It is only necessary to adjust the DC power supply output voltage in step 3 to the voltage value of the corresponding chemical type of battery. In step 4, after the battery is fully charged, it will be connected to the load via a circuit board. The measuring circuit board controls the battery to discharge to the termination voltage value, thereby calculating the actual capacity of the battery. Specifically, the structure and operation of the measuring circuit board are as follows: The measuring circuit board adopts a modular design and consists of a main circuit and a control circuit. The main circuit connects the battery and the load, and is controlled by a control circuit via a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The load terminal of the main circuit is a 1kΩ resistor. The control circuit uses an ESP32 microcontroller, connected to the main circuit board via GPIO pin 32. The microcontroller reads the battery voltage and current data via GPIO and controls the MOSFET to control the opening and closing of the main circuit. During discharge, the microcontroller reads the battery's output voltage and current in real time via GPIO and integrates them over time to calculate the battery capacity. When the microcontroller detects that the battery voltage has reached a low voltage of 3.3V, it changes the gate voltage of the MOSFET, opening the main circuit and terminating the discharge. The microcontroller runs a lightweight web server based on Linux, accessible via a Wi-Fi wireless access point. After the complete discharge process, the server records the calculated battery capacity. Connect the microcontroller's access point to obtain the actual capacity. This actual capacity will be recorded in the Battery Management System (BMS) in subsequent steps as a basis for calculating battery health. Step 5: Following the same steps as step 3, recharge the battery to its full voltage. Step 6: Measure the battery's internal resistance and self-discharge effect. Specifically, the detection steps include: Step 6.1, Measuring internal resistance: Fully charge the battery at room temperature, let it stand for 30 minutes to 4 hours, discharge it with a constant current I1 to 80-90% capacity, then instantaneously discharge it with a current I2 for 1 to 10 seconds, repeating five times.Record the voltages V1i and V2i and the current values ​​I1i and I2i for each test, and calculate using the formula R=(V1i-V2i) / (I2i-I1i), where i=1,2,3,4,5. Step 6.2, Measure self-discharge: Fully charge the battery as in Step 3, and let it stand at room temperature (25°C) for at least one day. Measure the open-circuit voltage of the battery 5 minutes, 1 hour, and 24 hours after the start of the test. In Step 6.2, a voltage drop of no more than 0.02 V in 5 minutes is normal, a drop of no more than 0.03 V in 1 hour is normal, and a drop of no more than 0.05 V in 24 hours is within a reasonable range. Step 7, Connect the batteries in series: Connect N batteries in series to form a battery pack, N≥4. One BMS control board controls M cells, M≥2 / N. In one embodiment, as shown in Figure 2, a battery pack can be composed of four cells connected in series. Each pair of battery cells is controlled by a BMS control board. In step 7, the BMS control board consists of a main circuit, a circuit controller, and a signal circuit. The main circuit connects different battery cells and is responsible for voltage balancing between them. A GPIO 40-pin slot is reserved on the main board for connection to the circuit controller. In step 7, the controller controls the current of the main circuit via a MOSFET connected to it. The controller communicates via a GPIO interface, using the MODBUS protocol and an RS485 physical interface. In step 7, the control board receives a pulse width modulation signal from the circuit controller. When the signal is received, cell voltage balancing begins; when the signal is disconnected, cell voltage balancing stops. When the signal is high, the MOSFET is on; when the signal is low, the MOSFET is off. After completing step 7, the voltage of all cells in the battery pack is balanced to the same value. The battery and BMS control board can then be installed in the battery cabinet. The testing method proposed in this Hong Kong short-term study is specific and feasible, with clear operational steps. It enables retired batteries to be combined and safely used in energy storage battery cabinets, improving the economic efficiency of retired batteries and reducing the environmental burden of material recycling. The above description is merely a preferred embodiment of this Hong Kong short-term study and is not intended to limit it. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this Hong Kong short-term study should be included within its protection scope.HK 30134886 A Claim 1 1. A testing method for reusing retired automotive batteries, characterized by comprising the following steps: Step 1, after the batteries are collected, a preliminary inspection is performed on the batteries to determine their condition; Step 2, the open-circuit voltage of the batteries is measured: a voltmeter is connected to the positive and negative terminals of each cell in the battery pack, the voltage of the cells is read, and it is confirmed whether the cells are overcharged (too high) or over-discharged (too low), and the voltage data of all cells in a battery are recorded; Step 3, each cell of the battery is charged independently to full voltage, using a standard charging procedure, i.e., constant current charging followed by constant voltage charging, and the DC power supply output voltage during the charging process can be adjusted according to the chemical type of the retired battery; Step 4, after the battery is fully charged, it is connected to a load via a circuit board, and the circuit board is used to control the battery to discharge to a termination voltage value, thereby calculating the actual capacity of the battery; Step 5, the operation of Step 3 is repeated to recharge the battery to full voltage; Step 6, the internal resistance and self-discharge effect of the battery are measured; Step 7: Connect the batteries in series to form a group, and use the BMS control board to control the cells in the battery. Step 8: Use the BMS to balance the voltage of all cells in the battery group to the same value, and install the batteries and BMS control board into the battery cabinet. 2. The test method according to claim 1, characterized in that the preliminary inspection in step 1 includes: checking the integrity of the battery surface, confirming whether there are any abnormal conditions such as damage, deformation, bending, bulging and / or leakage, and if there are any abnormal conditions, it is not used. 3. The test method according to claim 1, characterized in that in step 2, in measuring the open circuit voltage, the nominal voltage, full charge voltage and termination voltage of the battery itself are obtained based on the information of the retired battery itself, and the actual measured cell voltage is compared with the nominal voltage, full charge voltage and termination voltage of the battery itself to determine whether overcharging and over-discharging have occurred. 4. The test method according to claim 1, characterized in that, when the retired battery is a nickel-cobalt-manganese lithium battery, step 3 includes: Step 3.1, constant current charging: setting the output voltage of the DC adjustable power supply to 4.0V and the current to 10A, when the battery voltage has not reached 4.0V, the DC adjustable power supply will charge the battery with the actual battery voltage and a fixed current of 10A (HK 30134886 A, claim 2); Step 3.2, constant voltage charging: after the battery voltage reaches the full charge voltage, it enters the constant voltage charging mode. At this time, the fixed voltage output of the DC adjustable power supply is 4.0V, and the current decreases as the battery is gradually fully charged. When the current decreases to 0.1A, the battery can be considered fully charged.5. The test method according to claim 1, characterized in that the step of measuring the circuit board in step 4 includes: the measuring circuit board adopts a modular design, consisting of a main circuit and a control circuit. The main circuit is connected to the battery and the load, and is controlled by the control circuit via a metal-oxide-semiconductor field-effect transistor (MOSFET). The control circuit uses an ESP32 microcontroller, which is connected to the main circuit circuit board via GPIO 32 pins. The microcontroller reads the battery voltage and current data via GPIO and controls the MOSFET to control the opening and closing of the main circuit. During the discharge process, the microcontroller reads the battery output voltage and output current in real time via GPIO and integrates them over time to calculate the battery capacity. When the microcontroller detects that the battery voltage reaches a low voltage of 3.3V, it changes the gate voltage of the MOSFET to open the main circuit and terminate the discharge. 6. The test method according to claim 5 is further characterized in that, in step 4, the microcontroller runs a lightweight web server based on the Linux system, which can be accessed through a wireless access point. After a complete discharge process, the server records the calculated battery capacity and records the battery capacity value in the battery management system (BMS) as the basis for calculating battery health. 7. The test method according to claim 1, characterized in that the measurement steps in step 6 include: Step 6.1, measuring internal resistance: fully charge the battery at room temperature, let it stand for 30 minutes to 4 hours, discharge it to 80-90% capacity with constant current I1, and then discharge it instantaneously with current I2 for 1 to 10 seconds, repeating five times, recording the voltage V1i, V2i and the current values ​​I1i, I2i for each time, and calculating it according to the formula R=(V1i-V2i) / (I2i-I1i), where i=1,2,3,4,5; Step 6.2, measuring self-discharge: fully charge the battery according to step 3, let the battery stand at room temperature (25°C) for at least one day, and measure the open circuit voltage of the battery 5 minutes, 1 hour and 24 hours after the start of the test, where the voltage drop of no more than 0.02V in 5 minutes is normal, and the voltage drop of HK 30134886 A in 1 hour is normal. Claim 3 states that a voltage drop of no more than 0.03V is normal, and a 24-hour voltage drop of no more than 0.05V is within a reasonable range.8. The test method according to claim 1, characterized in that, in step 7, N batteries are connected in series to form a battery pack, N≥4, and a BMS control board controls M cells, M≥2 / N; the BMS control board consists of a main circuit, a circuit controller, and a signal circuit, the main circuit connects different cells and is responsible for voltage balance between cells, and a GPIO 40pin slot is reserved on the main board for connection with the circuit controller. 9. The test method according to claim 8, characterized in that, in step 7, the controller controls the current of the main circuit via a MOSFET connected to the main circuit. The controller communicates via a GPIO interface, using the MODBUS protocol and an RS485 physical interface. 10. The test method according to claim 9, characterized in that, in step 7, the BMS control board receives a pulse width modulation signal from the circuit controller; when the signal is received, cell voltage balancing begins; when the signal is disconnected, cell voltage balancing stops; when the signal is high, the MOSFET is turned on; when the signal is low, the MOSFET is turned off. HK 30134886 A Instruction Manual Appendix 1 Figure 1 HK 30134886 A Instruction Manual Appendix 2 Cell 1 Cell 2 Cell 3 Cell 4 Figure 2 HK 30134886 A.

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