CN114035081A - Test method for accurately identifying micro-short circuit problem of battery cell before liquid injection - Google Patents
Test method for accurately identifying micro-short circuit problem of battery cell before liquid injection Download PDFInfo
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- CN114035081A CN114035081A CN202111487122.4A CN202111487122A CN114035081A CN 114035081 A CN114035081 A CN 114035081A CN 202111487122 A CN202111487122 A CN 202111487122A CN 114035081 A CN114035081 A CN 114035081A
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- 238000010998 test method Methods 0.000 title claims abstract description 14
- 238000002347 injection Methods 0.000 title claims abstract description 6
- 239000007924 injection Substances 0.000 title claims abstract description 6
- 239000007788 liquid Substances 0.000 title claims abstract description 6
- 238000012360 testing method Methods 0.000 claims abstract description 64
- 238000000034 method Methods 0.000 claims abstract description 37
- 238000005070 sampling Methods 0.000 claims abstract description 19
- 238000007600 charging Methods 0.000 claims abstract description 14
- 230000009194 climbing Effects 0.000 claims abstract description 12
- 238000007599 discharging Methods 0.000 claims description 3
- 238000009413 insulation Methods 0.000 description 12
- 230000005284 excitation Effects 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000010891 electric arc Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
- G01R31/3842—Arrangements for monitoring battery or accumulator variables, e.g. SoC combining voltage and current measurements
Abstract
The invention provides a test method for accurately identifying the micro short circuit problem of a battery core before liquid injection, which controls constant current output to charge the battery core to a stable test voltage, and simultaneously, controls a voltage sampling channel to sample the voltage at two ends of a tested battery core in real time and draw a dynamic voltage change curve in the charging process in a charging voltage climbing and constant voltage maintaining stage; step two, calculating sampling points in the voltage climbing process, wherein the maximum voltage drop value Vd1 appears in the voltage climbing process; step three, calculating a sampling point in the voltage pressure maintaining process, and calculating a maximum voltage drop value Vd2 occurring after the voltage climbs to the set voltage and the test time is finished; step four, comparing the Vd1 and the Vd2 captured with Vd1 and Vd2 thresholds of a good cell test, and identifying instant micro short circuit discharge generated in the test; the invention dynamically monitors the whole testing process of the short circuit of the battery cell, and can accurately identify the micro short circuit problem in the whole process through two state parameters in the testing waveform.
Description
Technical Field
The invention relates to the technical field of micro-short circuit testing of battery cells, in particular to a testing method for accurately identifying the micro-short circuit problem of the battery cells before liquid injection.
Background
The short circuit of the battery can cause abnormal discharge of the battery and even safety accidents. The detection and identification of the short circuit problem of the battery cell (cell for short) before the electrolyte is injected in the production process of the battery are very important, the abnormal discharge and safety accidents caused by the short circuit of the battery can be avoided in the finished battery stage, the short circuit cell can be identified in advance, and the production and processing cost of the short circuit cell is reduced.
In the actual production process, besides the serious short circuit problems caused by material dust puncture, diaphragm breakdown, tab folding and the like, a large proportion of micro-short circuit cells exist, the micro-short circuit points are caused by material dust particles, diaphragm defects, the structural characteristics of the cells and the like, the micro-short circuit points can generate instantaneous discharge after the positive electrode and the negative electrode are excited by high voltage, the micro-short circuit points can be restored to be similar to a normal cell state after being fused in the high-voltage discharge process, but the cells still have the micro-short circuit discharge burning defect or further cause the risk of short circuit, and are the types of cells which are difficult to identify in short circuit cells.
At present, the types of the battery cell short circuit test equipment are more: methods such as multimeter ohm-level measurement, alternating current withstand voltage test, direct current withstand voltage test, insulation resistance test and the like are applied in a plurality of production places, and particularly, the insulation resistance test method is applied more frequently.
Measuring an ohmic level of a multimeter: the method comprises the steps of applying small current, sampling small voltage signals at two ends of the battery cell, calculating the resistance value of the battery cell according to ohm law, and judging whether the battery cell is qualified or not according to the resistance value.
And (3) alternating current withstand voltage test: applying alternating-current high-voltage excitation, sampling leakage current of a test loop, and judging whether the battery core has a short circuit problem or not through a leakage current value.
And (3) testing the insulation resistance: and applying direct-current voltage excitation, sampling the leakage current of the test loop, calculating the resistance value of the battery cell according to the ohm law, and judging whether the battery cell is qualified or not according to the resistance value.
The method for measuring the ohmic gear of the multimeter adopts a mode of applying weak small signals, and does not apply high enough excitation between the positive electrode and the negative electrode of the battery core, and a relatively high proportion of battery core problem points can puncture the problem points to expose the problem only under the test condition of high enough test voltage, so that the method for measuring the ohmic gear of the multimeter can only identify the short-circuit battery cores which are short-circuited and can not effectively identify the short-circuit problem of the battery cores which can be exposed only by high-voltage excitation.
The alternating current high voltage excitation is applied to the tested electric core by the alternating current withstand voltage test method, and the state of the electric core is judged by measuring leakage current. On one hand, the electric core is a capacitor, so that the alternating current withstand voltage test has very large leakage current due to the direct current and alternating current blocking characteristic of the capacitor, the leakage current is greatly influenced by the capacity value of the electric core, and the electric core has large current fluctuation under the conditions of cold pressing, hot pressing and large capacity value change after the electric core is matched, so that accurate identification and judgment cannot be realized; on the other hand, the alternating current withstand voltage test equipment is originally electrical safety performance test equipment in the field of electrical appliance test such as household appliances, the range of the effective value of the test voltage is generally 300 VAC-5000 VAC, the peak value of the test voltage is 424V-7071V, the current battery industry is limited by the withstand voltage of an isolating membrane, the peak value voltage of the test of the battery cell is generally 100V-500V, and the voltage test of 200V or below accounts for most of the tests, so that the alternating current withstand voltage test method is gradually eliminated in the field of the short circuit test of the battery cell.
The insulation resistance test method is also a test method in electrical safety performance tests of electrical appliances such as household appliances, and in a cell short circuit test, the result is judged by measuring the insulation resistance value, the test voltage range is generally 25 VDC-1000 VDC, and the voltage range can meet the cell short circuit test requirement. However, the battery cell is an obvious capacitive tested product, the insulation resistor is in constant current charging (the maximum constant current of the current is generally 1 mA-10 mA) in the initial stage of the charging test, the current output of the insulation resistor test equipment reaches the maximum at the moment, if the insulation resistor test equipment is judged according to the resistance value, the resistance value in the charging stage is 100k omega by taking 100V and 1mA tests as examples, and the lower limit of the resistance value of the battery cell is M omega level, so that the insulation resistor tester cannot judge the problem in the charging stage, and judges the resistance value according to the resistance value when the test time is over. This will "miss" the micro short circuit problem that occurs during charging. On the other hand, in order to obtain stable resistance, the insulation resistance test equipment adopts an algorithm of averaging test results, and the sampling values are averaged by taking 100ms, 250ms, 500ms and the like as refresh cycles, so that the instantaneous discharge problem occurring in ms can be averagely covered, and the insulation resistance test equipment cannot meet the current requirement for identifying and verifying the micro short circuit problem of the battery cell.
The invention aims to solve the problem of identifying and detecting the micro-short circuit cell with the characteristic of instantaneous discharge in the cell stage of the battery, so as to improve the identification capability of a battery production line on the problem cell, support the battery to identify the design defects of a product in the development stage and guide a designer to design the battery according to the correct direction.
Disclosure of Invention
The invention adopts a test method of applying direct-current high-voltage excitation and monitoring voltage waveform to monitor the whole process of the battery cell charging test, and captures and calculates the maximum voltage drop in the test process so as to identify the micro-short circuit instantaneous discharge problem in the high-voltage test.
In order to achieve the purpose, the invention adopts the following technical scheme:
controlling the constant current output to charge the battery cell to a stable test voltage, and simultaneously comprising the following steps of:
step one, in a charging voltage climbing and voltage constant pressure maintaining stage, a voltage sampling channel is controlled to sample voltages at two ends of a tested core in real time and draw a voltage dynamic change curve in a charging process;
calculating sampling points in the voltage climbing process, and calculating a maximum voltage drop value Vd1 in the voltage climbing process;
step three, calculating a sampling point in the voltage pressure maintaining process, and calculating a maximum voltage drop value Vd2 occurring after the voltage climbs to the set voltage and the test time is finished;
and step four, comparing the Vd1 and the Vd2 captured with Vd1 and Vd2 thresholds of a good cell test, and identifying instant micro short circuit discharge generated in the test process.
Preferably, the sampling period of the voltage dynamic change curve in the step one is less than 1us, so that the instant voltage drop of the discharging process in the level of 1ms can be identified.
The invention has the beneficial effects that: the testing method provided by the invention dynamically monitors the whole testing process of the short circuit of the battery cell, can accurately identify the instantaneous micro short circuit discharge state in the charging and pressure maintaining processes and quantize the instantaneous micro short circuit discharge state into Vd1 and Vd2, and can accurately identify the micro short circuit problem in the whole process by testing the two state parameters in the waveform. In the short circuit test of battery electricity core stage, universal meter, interchange withstand voltage tester and insulation resistance tester are the test equipment who transplants from traditional test field, borrow to do not aim at all kinds of short circuit problems that take place among the test procedure of battery electricity core short circuit and carry out the discernment test of pertinence, so can't carry out effective discernment to the little short circuit problem of part that takes place in the electricity core. The testing method provided by the invention is designed for solving the micro short circuit problem in the process of testing the short circuit of the battery cell, and has more accurate purpose and identification capability.
Drawings
FIG. 1 is a schematic view of a negative electrode filament overlapping or approaching a positive electrode;
FIG. 2 is a schematic representation of a high pressure test to short but still retain the charge;
fig. 3 is a schematic diagram of a qualified cell test waveform;
fig. 4 is a schematic diagram of a waveform disqualified from a micro short circuit cell Vd 1;
fig. 5 is a schematic diagram of a waveform disqualified from a micro short circuit cell Vd 2;
FIG. 6 is a flowchart of the test method.
In the figure: 1. a negative electrode; 2. an isolation film; 3. a positive electrode; 4. negative electrode material wires; 5. and (4) melting the short negative electrode material wire.
Detailed Description
The invention is further illustrated by the following specific examples.
First, a case that cannot be detected by the conventional method is exemplified by fig. 1 and 2.
In the figure, the cathode material is dropped and is lapped to the anode through the edge of the battery core, the cathode material is dropped and is lapped to the anode to form a short circuit loop of the anode and the cathode, the short circuit loop can be rapidly melted off due to weak overcurrent capacity and accompanied with electric arc generation when high-voltage excitation is applied between the anode and the cathode, a short circuit channel disappears after a material wire is melted off and is recovered to a non-short circuit state, but a certain degree of burning damage is generated on an isolating membrane due to the fusing of the material wire and the generation of the electric arc, and the traditional method can not detect the situation.
As shown in fig. 3 to 6, the scheme adopted by the present invention is: controlling the constant current output to charge the battery cell to a stable test voltage, and simultaneously comprising the following steps of:
step one, in a charging voltage climbing and voltage constant pressure maintaining stage, a voltage sampling channel is controlled to sample voltages at two ends of a tested core in real time and draw a voltage dynamic change curve in a charging process; the sampling period of the voltage dynamic change curve is less than 1us, so that the instant voltage drop of the discharging process in the level of 1ms can be identified.
Calculating sampling points in the voltage climbing process, and calculating a maximum voltage drop value Vd1 in the voltage climbing process;
step three, calculating a sampling point in the voltage pressure maintaining process, and calculating a maximum voltage drop value Vd2 occurring after the voltage climbs to the set voltage and the test time is finished;
and step four, comparing the Vd1 and the Vd2 captured with Vd1 and Vd2 thresholds of a good cell test, and identifying instant micro short circuit discharge generated in the test process.
The above-described solutions can be implemented by the skilled person in the art without any inventive effort, using existing techniques and the expert knowledge in the field.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Although the present invention has been described with reference to the specific embodiments, it should be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (2)
1. A test method for accurately identifying the micro short circuit problem of a battery cell before liquid injection is characterized by comprising the following steps: controlling the constant current output to charge the battery cell to a stable test voltage, and simultaneously comprising the following steps of:
step one, in a charging voltage climbing and voltage constant pressure maintaining stage, a voltage sampling channel is controlled to sample voltages at two ends of a tested core in real time and draw a voltage dynamic change curve in a charging process;
calculating sampling points in the voltage climbing process, and calculating a maximum voltage drop value Vd1 in the voltage climbing process;
step three, calculating a sampling point in the voltage pressure maintaining process, and calculating a maximum voltage drop value Vd2 occurring after the voltage climbs to the set voltage and the test time is finished;
and step four, comparing the Vd1 and the Vd2 captured with Vd1 and Vd2 thresholds of a good cell test, and identifying instant micro short circuit discharge generated in the test process.
2. The test method for accurately identifying the problem of the micro short circuit of the battery cell before liquid injection according to claim 1, wherein the test method comprises the following steps: in the first step, the sampling period of the voltage dynamic change curve is less than 1us, so that the instant voltage drop of the discharging process in the level of 1ms can be identified.
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| CN202111487122.4A CN114035081A (en) | 2021-12-07 | 2021-12-07 | Test method for accurately identifying micro-short circuit problem of battery cell before liquid injection |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114545165A (en) * | 2022-02-21 | 2022-05-27 | 青岛艾测科技有限公司 | High-voltage insulation detection device special for capacitive load |
| CN115792522A (en) * | 2022-12-08 | 2023-03-14 | 青岛艾测科技有限公司 | Capacitive load insulation detection method, device and equipment |
| CN115877210A (en) * | 2022-12-08 | 2023-03-31 | 青岛艾测科技有限公司 | Pressure-maintaining adjustable capacitive load insulation detection method, device and equipment |
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2021
- 2021-12-07 CN CN202111487122.4A patent/CN114035081A/en active Pending
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN115792522A (en) * | 2022-12-08 | 2023-03-14 | 青岛艾测科技有限公司 | Capacitive load insulation detection method, device and equipment |
| CN115877210A (en) * | 2022-12-08 | 2023-03-31 | 青岛艾测科技有限公司 | Pressure-maintaining adjustable capacitive load insulation detection method, device and equipment |
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