A method for screening a cascade battery

Abstract

The application discloses a kind of cascade lithium battery consistency screening methods, comprising the following steps: step I: appearance inspection;Step II: voltage and resistance measurement;Step III: dynamic screening, to be screened battery is carried out charge-discharge test, export charge-discharge data, obtain average voltage curve;According to voltage deviation control to move curve to obtain the upper control line of voltage deviation, move curve to obtain the lower control line of voltage deviation, and the battery in voltage curve is located in the upper control line and the lower control line, that is, qualified battery;Step IV: after standing, according to new measurement voltage, resistance and other static sorting data grouping.Compared with prior screening method, the application combines dynamic and static comprehensively, further obtains battery performance parameter data, according to which batch sorting battery, consistency is better, later operation is longer, and safety is more reliable.

Description

Technical Field

[0001] This invention belongs to the field of safe application technology of cascaded lithium batteries, and particularly relates to a consistency screening method for cascaded batteries. Background Technology

[0002] Second-hand batteries refer to batteries that have degraded after a period of use and are subsequently recycled for use in other industries. For example, lithium iron phosphate batteries used in automobiles with capacity degradation below 80% can be used as backup power for communication base stations and for energy storage. How to handle retired power batteries is becoming an important issue in the development of the new energy vehicle industry. Second-hand utilization of power batteries is a crucial step in achieving this goal. Currently, the mainstream sorting method involves directly measuring battery voltage and internal resistance before matching them for use. However, in the later stages of use, second-hand batteries often experience problems such as sudden loss of voltage retention, false voltage readings, and battery management systems reporting differential voltage protection failures and stopping operation. Therefore, ensuring the safe use of second-hand batteries remains a challenge. Summary of the Invention

[0003] The purpose of this invention is to provide a method for screening the consistency of batteries used in tiered applications. This solves the problems of excessively long sorting time and high cost of current tiered battery sorting methods, which also fail to consider the different performance characteristics of batteries.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A method for screening secondary batteries, wherein the selected prismatic battery comprises a battery, a pressure relief valve, positive and negative terminals, and a casing, characterized by comprising the following steps:

[0006] Step 1: Visual Inspection

[0007] Use visual inspection or optical inspection equipment to check for appearance defects in the sorted batteries. If there are no appearance defects, proceed to step II sorting. If the batteries have appearance defects, they are deemed unqualified.

[0008] Step II: Voltage and Internal Resistance Measurement

[0009] The qualified batteries after sorting by the method described in step I are then sorted using the following steps:

[0010] a) Measure the open-circuit voltage; batteries whose voltage measured by the voltage meter is lower than the voltage limit will be rejected.

[0011] b) Measure the battery's internal resistance. Batteries whose internal resistance exceeds the resistance limit measured by the internal resistance tester will be rejected.

[0012] After the above steps I and II, the first batch of qualified batteries were initially sorted out and entered step III for screening;

[0013] Step III: Dynamic screening. The batteries to be screened are subjected to charge and discharge tests, and the charge and discharge data are exported to obtain the average voltage curve.

[0014] The charge-discharge cycle is performed according to the standard charging current and temperature specified in the battery datasheet, charging to the battery charging cut-off voltage, resting for 10-15 minutes, and then discharging to the battery cut-off voltage according to the standard discharging current and temperature specified in the battery datasheet, resting for 10-15 minutes, and then charging to 20%-40% of the battery capacity. The charge-discharge data is then exported to generate a time-voltage curve. Within the set charging and discharging voltage ranges, curve segments with voltage deviations exceeding 20mV at the same time are removed, retaining 40-60% of the curves. The arithmetic mean of the voltage values ​​of these retained curves is then calculated to obtain an average voltage curve. Based on the voltage deviation control, the curve is shifted upwards by +50mV to +400mV to obtain the upper control line for voltage deviation, and downwards by -50mV to -400mV to obtain the lower control line for voltage deviation. Batteries whose voltage curves fall within the upper and lower control lines are considered qualified batteries and proceed to the next sorting step.

[0015] Step IV: After standing for 5-7 days, measure the open circuit voltage again. Discard any batteries that are 20mV lower than the average open circuit voltage. Group the batteries according to the new measured voltage, internal resistance and other static sorting data. Pair them up according to a deviation of 10mV in the average voltage and a deviation of 20% in the average internal resistance.

[0016] Furthermore, the appearance defects in the first step of the appearance inspection include any one of the following appearance defects a) to e):

[0017] c) Any dents or deformations on the battery surface;

[0018] d) Electrolyte leakage at the damaged pressure relief valve on the battery terminal or at other damaged parts of the battery;

[0019] c) The battery casing or terminals are corroded;

[0020] d) Pressure relief valve rupture and pressure release;

[0021] e) The battery thickness specification is measured to be more than 15% greater than the value given in the battery specification sheet.

[0022] Furthermore, in the second step of voltage and internal resistance measurement, the voltage limit is 2.6V.

[0023] Furthermore, the second step involves measuring the battery's internal resistance, with the internal resistance limit being +10% of the internal resistance value given in the battery specifications.

[0024] Furthermore, in step III, the charging voltage curve segment is set within the range of 3.4V-3.6V.

[0025] Furthermore, in step III, the range of the discharge voltage curve segment is set between 3.0V and 2.85V.

[0026] Technical effects of this technical solution:

[0027] Compared to existing screening methods, this invention combines dynamic and static methods to obtain more comprehensive battery performance parameter data. Based on this data, batteries are sorted in batches with better consistency, longer operating time, and greater safety and reliability. This solves the problems of excessively long sorting times and high costs associated with current battery sorting methods for secondary use, while also failing to consider the different performance characteristics of each battery. Attached Figure Description

[0028] Figure 1 Battery raw charge and discharge data fitting curve

[0029] Figure 2 Identify batteries with high curve ionization.

[0030] Figure 3 Curve relative to polymer battery charge / discharge data curve

[0031] Figure 4 The average charge / discharge curve of this batch of batteries

[0032] Figure 5 The upper and lower limits of the voltage curve fitting for this batch of batteries

[0033] Figure 6 Bundle Figure 5 Voltage curve fitting upper and lower limit curves serve as the selection range for the batteries to be screened.

[0034] Figure 7 Filter out in Figure 6 A schematic diagram of the battery curves within the selected range shown. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0036] Example 1

[0037] The following embodiment screens 35 lithium iron phosphate batteries. The selected prismatic batteries consist of a battery, a pressure relief valve, positive and negative terminals, and a casing. The method is characterized by the following steps:

[0038] Step 1: Visual Inspection

[0039] The sorted batteries are inspected for appearance defects using visual inspection or optical inspection equipment. These appearance defects include the following:

[0040] a) The battery surface is dented or deformed at any location;

[0041] b) Electrolyte leakage at the damaged pressure relief valve on the battery terminal or at other damaged parts of the battery;

[0042] c) The battery casing or terminals are corroded;

[0043] d) Pressure relief valve rupture and pressure release;

[0044] e) Battery thickness specifications where the expansion exceeds 15% of the value given in the battery specification sheet.

[0045] If the selected battery does not have any of the appearance defects mentioned in a) to e), it will proceed to step II for sorting. If the battery has any of the appearance defects mentioned in a) to e), it will be deemed unqualified.

[0046] Step II: Voltage and Internal Resistance Measurement

[0047] The qualified batteries after sorting by the method described in step I are then sorted using the following steps:

[0048] a) Measure the open-circuit voltage; batteries with a voltage reading below 2.6V should be discarded.

[0049] b) Measure the battery's internal resistance. Discard any battery whose internal resistance exceeds the value given in the battery specification sheet by 15% when measured by an internal resistance tester.

[0050] After the above steps I and II, the first batch of 28 qualified batteries were initially selected and entered step III for screening.

[0051] Step III: Dynamic Sorting

[0052] (1) After the charge-discharge cycle test, the charge-discharge data is exported as an Excel file. Voltage and capacity data are recorded every minute according to the preset steps. Voltage curve fitting is then performed, such as... Figure 1 As shown.

[0053] (2) Find batteries with high free radical degree on the curve, such as Figure 2 The curve showing the position of the circle.

[0054] (3) Remove batteries with significantly deviated voltages to obtain the relative charge / discharge data curves of the polymer battery. For example... Figure 3 As shown.

[0055] (4) Re-fit the data curve using averages to find the average curve. For example... Figure 4 As shown.

[0056] (5) Based on the required differential voltage range for the selected batteries, provide the upper and lower limits of the curve fitting curves. In this example, the upper and lower deviations are set to 100mV. Figure 5 As shown.

[0057] (6) Place the set range curve into the battery curves to be screened for selection. In this embodiment, the original 28 batteries are selected. Figure 6 As shown.

[0058] (7) Select the batteries within the differential pressure range: battery 5, battery 9, battery 13, battery 14, and battery 15, a total of 5 batteries. For example... Figure 7 As shown.

[0059] Step IV: After letting the 5 batteries sit for 7 days, measure the open circuit voltage again. The measured open circuit voltages are 3.204V, 3.206V, 3.207V, 3.209V, and 3.206V. Discard any batteries with an open circuit voltage 20mV lower than the average value. Measure the internal resistance again. The measured internal resistance values ​​are 0.481mΩ, 0.466mΩ, 0.469mΩ, 0.489mΩ, and 0.474mΩ. Then, pair them up according to an average open circuit voltage deviation of 10mV and an average internal resistance deviation of 20%.

Claims

1. A method for screening graded batteries, wherein the selected prismatic battery comprises a battery, a pressure relief valve, positive and negative terminals, and a casing, characterized in that: Includes the following steps: Step 1: Visual Inspection Use visual inspection or optical inspection equipment to check for appearance defects in the sorted batteries. If there are no appearance defects, proceed to step II sorting. If the batteries have appearance defects, they are deemed unqualified. Step II: Voltage and Internal Resistance Measurement The qualified batteries after sorting by the method described in step I are then sorted using the following steps: a) Measure the open-circuit voltage; batteries whose voltage measured by the voltage meter is lower than the voltage limit will be rejected. b) Measure the battery's internal resistance. Batteries whose internal resistance exceeds the resistance limit measured by the internal resistance tester will be rejected. After the static screening in steps I and II above, the first batch of qualified batteries were initially sorted out and entered step III screening; Step III: Dynamic screening. The batteries to be screened are subjected to charge and discharge tests, and the charge and discharge data are exported to obtain the average voltage curve. The charge-discharge cycle is performed according to the standard charging current and temperature specified in the battery datasheet, charging to the battery charging cut-off voltage, resting for 10-15 minutes, and then discharging to the battery cut-off voltage according to the standard discharging current and temperature specified in the battery datasheet, resting for 10-15 minutes, and then charging to 20%-40% of the battery capacity. The charge-discharge data is then exported to generate a time-voltage curve. Within the set charging and discharging voltage ranges, curve segments with voltage deviations exceeding 20mV at the same time are removed, retaining 40-60% of the curves. The arithmetic mean of the voltage values ​​of these retained curves is then calculated to obtain an average voltage curve. Based on the voltage deviation control, the curve is shifted upwards by +50mV to +400mV to obtain the upper control line for voltage deviation, and downwards by -50mV to -400mV to obtain the lower control line for voltage deviation. Batteries whose voltage curves fall within the upper and lower control lines are considered qualified batteries and proceed to the next sorting step. Step IV: After standing for 5-7 days, measure the open circuit voltage again. Discard any batteries that are 20mV lower than the average open circuit voltage. Group the batteries according to the new measured voltage, internal resistance and other static sorting data. Pair them up according to a deviation of 10mV in the average voltage and a deviation of 20% in the average internal resistance.

2. The method for screening graded batteries according to claim 1, characterized in that, The appearance defects in the first step of the appearance inspection include any one of the following appearance defects a) to e): a) The battery surface is dented or deformed at any location; b) Electrolyte leakage at the damaged pressure relief valve on the battery terminal or at other damaged parts of the battery; c) The battery casing or terminals are corroded; d) Pressure relief valve rupture and pressure release; e) The battery thickness specification is measured to be more than 15% greater than the value given in the battery specification sheet.

3. The method for screening graded batteries according to claim 1, characterized in that, In the second step of voltage and internal resistance measurement, the voltage limit is 2.6V.

4. The method for screening graded batteries according to claim 1, characterized in that, The second step involves measuring the voltage and internal resistance of the battery. The internal resistance limit is 10% of the internal resistance value given in the battery datasheet.

5. The method for screening graded batteries according to claim 1, characterized in that, In step III, the charging voltage curve segment is set within the range of 3.4V-3.6V.

6. The method for screening graded batteries according to claim 1, characterized in that, In step III, the range of the discharge voltage curve segment is set between 3.0V and 2.85V.

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