CN111487543A - DCR test method, system, device and medium in lithium ion battery cycle - Google Patents
DCR test method, system, device and medium in lithium ion battery cycle Download PDFInfo
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- 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
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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]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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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]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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Abstract
The invention discloses a DCR test method, a system, equipment and a medium in a lithium ion battery cycle process, wherein the DCR test method comprises the steps of charging a lithium ion battery to a charge cut-off voltage; continuously discharging for a period of time, acquiring the voltage value and the discharge current value of the lithium ion battery before and after discharging, continuously charging for a period of time, acquiring the voltage value and the charge current value of the lithium ion battery before and after charging, then continuously discharging for a period of time, and repeating the step for a plurality of times; performing a plurality of lithium ion battery charge-discharge cycles; and obtaining the discharging DCR and the charging DCR according to the DCR calculation formula. The technical scheme of the invention can better understand the change trends of charging DCR and discharging DCR of the lithium ion battery in the circulation process, identify the risk of abnormal performance of the battery core in advance, save a large amount of test time and avoid the influence on the continuity of battery circulation data caused by the repeated movement of the battery.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery testing, and particularly relates to a method, a system, equipment and a medium for testing DCR (direct current rating) in lithium ion battery circulation.
Background
As is well known, petroleum, coal, and natural gas are major energy sources in the present society, but they are all non-renewable resources. With the rapid development of human society, these non-renewable resources will be used up in the near future, and in addition, the use of these non-renewable resources will cause problems such as environmental pollution. The traditional vehicles and enterprises make sales plans of new energy vehicles and prohibition sales plans of fuel vehicles at a large dispute, and in addition, the wind power energy storage industry using lithium ion batteries as energy has huge development potential, so that the development of the lithium ion batteries is further promoted. The current lithium ion batteries mainly have the following problems: low energy density, short cycle life, poor safety performance and high cost. The direct current internal resistance is one of important electrical properties of the lithium ion battery, and the direct current internal resistance of the lithium ion battery is called DCR for short, and comprises charging DCR and discharging DCR, and is an important index for evaluating the performance of the lithium ion battery, and the energy density and the cycle life of the lithium ion battery are directly influenced. The battery with larger DCR generates larger heat, thereby influencing the safety performance of the lithium ion battery when in use, and therefore, the DCR of the lithium ion battery is necessary to be tested.
At present, the DCR of a lithium ion battery is generally tested independently before the circulation of the lithium ion battery, and as the battery is always subjected to charge-discharge circulation testing, the change condition of the DCR in the battery circulation process is unknown.
Disclosure of Invention
The invention provides a method, a system, equipment and a medium for testing DCR in lithium ion battery circulation, aiming at solving the technical problem that the DCR of a battery cannot be conveniently tested in the prior art.
The invention solves the technical problems through the following technical scheme:
a DCR test method in a lithium ion battery cycle process comprises the following steps:
s1, standing the lithium ion battery for a first time period, and then charging the lithium ion battery to a first charging cut-off voltage;
s2, standing the lithium ion battery for a second time period, then continuously discharging for a third time period t3 at a first current value I1, and obtaining a first voltage value V1 when the lithium ion battery stands and a second voltage value V2 when the lithium ion battery discharges;
s3, standing the lithium ion battery for a fourth time period, then continuously charging the lithium ion battery for a fifth time period t5 at a second current value I2, and acquiring a third voltage value V3 when the lithium ion battery is standing and a fourth voltage value V4 when the lithium ion battery is charging;
s4, standing the lithium ion battery for a sixth time period, and then continuously discharging for a seventh time period t7 at a third current value I3, wherein I3 t7+ I1 t3-I2 t5> 0;
s5, repeating the steps S2-S4 for a plurality of times until the SOC of the lithium ion battery cell is not higher than the first cell SOC value;
s6, carrying out charge-discharge circulation on the lithium ion battery for a plurality of times;
step S3 is followed by: and calculating the discharge DCR and/or the charge DCR of the lithium ion battery according to the following calculation formula:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
Preferably, each charge-discharge cycle in step S6 includes the following steps:
s61, standing the lithium ion battery for an eighth time period, and continuously charging to a second charging cut-off voltage;
and S62, standing the lithium ion battery for a ninth time period, and continuously discharging to a second discharge cut-off voltage.
Preferably, the DCR testing method further includes: steps S1-S6 are repeatedly executed until a loop termination condition is reached.
Preferably, the DCR testing method further includes: the number of charge and discharge cycles is the same each time step S6 is repeatedly executed.
Preferably, the cycle termination condition comprises at least one of: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold.
Preferably, the first threshold value ranges from 50% to 90%, and the third threshold value ranges from 50% to 90%.
Preferably, the first charge cut-off voltage in step S1 is a full charge voltage value of the lithium ion battery.
Preferably, the step S1 further includes the following steps before charging the lithium ion battery:
and standing the lithium ion battery for a tenth time period, and continuously discharging to the first discharge cut-off voltage.
Preferably, in step S4, the value of the seventh time period t7 is (C0 × m1/n1-I1 × t3+ I2 × t5)/I4, where C0 is the total capacity of the lithium ion battery cell, n1 is a positive integer, and m1 is a value between 50% and 100%, and those skilled in the art should understand that the values of I1, I2, t3, and t5 are such that the value of t7 is greater than 0.
Preferably, the DCR testing method further includes: and acquiring the change trend of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or charging DCR.
A DCR test system in a lithium ion battery cycling process, the DCR test system comprising:
the device comprises a preprocessing module, a voltage-limiting module and a voltage-limiting module, wherein the preprocessing module is used for standing a lithium ion battery for a first time period and then charging the lithium ion battery to a first charging cut-off voltage;
the first discharging module is used for standing the lithium ion battery for a second time period, then continuously discharging for a third time period t3 at a first current value I1, and acquiring a first voltage value V1 when the lithium ion battery stands and a second voltage value V2 when the lithium ion battery discharges;
the first charging module is used for standing the lithium ion battery for a fourth time period, then continuously charging the lithium ion battery for a fifth time period t5 at a second current value I2, and acquiring a third voltage value V3 when the lithium ion battery stands still and a fourth voltage value V4 when the charging is finished;
the second discharging module is used for standing the lithium ion battery for a sixth time period, and then continuously discharging for a seventh time period t7 at a third current value I3, wherein I3 t7+ I1 t3-I2 t5> 0;
the first circulation module is used for repeatedly and sequentially calling the first discharging module, the first charging module and the second discharging module for a plurality of times until the SOC of the lithium ion battery cell is not higher than the SOC value of the first cell;
the second circulation module is used for carrying out charging and discharging circulation on the lithium ion battery for a plurality of times;
the calculation module is used for calculating the discharging DCR and/or the charging DCR of the lithium ion battery, and the calculation formula is as follows:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
Preferably, the second cycle module is configured to perform a charge and discharge cycle on the lithium ion battery through a charging unit and a discharging unit, wherein,
the charging unit is used for standing the lithium ion battery for an eighth time period and continuously charging the lithium ion battery to a second charging cut-off voltage;
and the discharging unit is used for standing the lithium ion battery for a ninth time period and continuously discharging to a second discharging cut-off voltage.
Preferably, the DCR testing system further includes a third cycle module, configured to repeatedly and sequentially call the preprocessing module, the first discharging module, the first charging module, the second discharging module, the first cycle module, the second cycle module, and the calculating module until a cycle termination condition is reached.
Preferably, the cycle termination condition comprises at least one of: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold.
Preferably, the first threshold value ranges from 50% to 90%, and the third threshold value ranges from 50% to 90%.
Preferably, the first charge cut-off voltage is a full charge voltage value of the lithium ion battery.
Preferably, the preprocessing module is further configured to allow the lithium ion battery to stand for a tenth time period before the lithium ion battery is charged, and continue to discharge to the first discharge cut-off voltage.
Preferably, the value of the seventh time period t7 in the second discharge module is (C0 × m1/n1-I1 × t3+ I2 × t5)/I4, where C0 is the total capacity of the lithium ion battery cell, n1 is a positive integer, and m1 is a value between 50% and 100%, and those skilled in the art should understand that the values of I1, I2, t3, and t5 are such that the value of t7 is greater than 0.
Preferably, the DCR testing system further includes a variation trend obtaining module, configured to obtain a variation trend of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or charging DCR.
An electronic device comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor executes the computer program to realize the steps of the DCR testing method in the lithium ion battery cycling process.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the aforementioned steps of the DCR testing method in a cycling process of a lithium ion battery.
The positive progress effects of the invention are as follows:
in the charge-discharge cycle process of the lithium ion battery, the DCR of the lithium ion battery, including the charge and/or discharge DCR, is directly tested, so that the change trend of the charge DCR and/or the discharge DCR of the lithium ion battery in the cycle process can be better known, the DCR is used for researching the electrical property change condition of the battery cell in the cycle process, more analysis indexes are provided for attenuation analysis and improvement of the cycle life of the battery cell in the cycle process of the lithium ion battery, and the risk of abnormal performance of the battery cell is identified in advance. In addition, because the DCR test is not required to be carried out separately besides the battery charge-discharge cycle test, a large amount of test time is saved, and the influence on the continuity of the battery cycle data caused by the repeated movement of the battery is avoided.
Drawings
Fig. 1 is a flowchart of a DCR testing method in a lithium ion battery cycle process according to embodiment 1 of the present invention.
Fig. 2 is a discharge DCR variation trend chart obtained in the DCR testing method in the lithium ion battery cycle process in embodiment 1 of the present invention.
Fig. 3 is a charging DCR variation trend chart obtained in the DCR testing method in the lithium ion battery cycle process in embodiment 1 of the present invention.
Fig. 4 is a block diagram of a DCR test system in a lithium ion battery cycling process according to embodiment 2 of the present invention.
Fig. 5 is a block diagram of an electronic device according to embodiment 3 of the present invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
The present embodiment provides a DCR testing method in a lithium ion battery cycle process, as shown in fig. 1, the DCR testing method includes the following steps:
s1, standing the lithium ion battery for a tenth time period, and then continuously discharging the lithium ion battery to a first discharge cut-off voltage; standing a lithium ion battery for a first time period, and then charging the lithium ion battery to a first charge cut-off voltage;
s2, standing the lithium ion battery for a second time period, then continuously discharging for a third time period t3 at a first current value I1, and obtaining a first voltage value V1 when the lithium ion battery stands and a second voltage value V2 when the lithium ion battery discharges;
s3, standing the lithium ion battery for a fourth time period, then continuously charging the lithium ion battery for a fifth time period t5 at a second current value I2, and acquiring a third voltage value V3 when the lithium ion battery is standing and a fourth voltage value V4 when the lithium ion battery is charging;
s4, standing the lithium ion battery for a sixth time period, and then continuously discharging for a seventh time period t7 at a third current value I3, wherein the value of t7 is (C0 m1/n1-I1 t3+ I2 t5)/I3, wherein C0 is the total capacity of the lithium ion battery cell, n1 is a positive integer, and m1 is a numerical value between 50% and 100%;
s5, repeating the steps S2-S4 for a plurality of times until the SOC of the lithium ion battery cell is not higher than the first cell SOC value;
s6, repeating the following charge and discharge cycles several times: standing the lithium ion battery for an eighth time period, and continuously charging to a second charging cut-off voltage; standing the lithium ion battery for a ninth time period, and continuously discharging to a second discharge cut-off voltage;
s7, repeatedly executing the steps S1-S6 until a cycle ending condition is reached;
step S31 is also included after step S3:
s31, calculating the discharging DCR and/or charging DCR of the lithium ion battery, wherein the calculation formula is as follows:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
It should be noted that the step S31 in fig. 1 is just an example before the step S4, and the step S31 may be after the step S3, specifically, the step S31 may be before or after any of the steps S4 to S7.
The DCR testing method of this embodiment may further include: and acquiring the change trend of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or charging DCR.
In step S7, the cycle termination condition may specifically include at least one of the following: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold, and the value range of the corresponding first threshold can be 50% to 90%, the value range of the corresponding third threshold can be 50% to 90%, and specific values can be set according to actual needs.
Preferably, the first charge cut-off voltage in step S1 may be a full charge voltage value.
Taking a square aluminum-shell lithium iron phosphate battery of 105Ah as an example, a specific implementation process of the DCR testing method in the lithium ion battery cycle process of this embodiment is described in detail below, where a testing environment temperature may be set to 25 ± 2 ℃, and the DCR testing method specifically includes the following steps:
s101, standing the lithium ion battery for a tenth time period of 30 minutes, and then continuously discharging the lithium ion battery to a first discharge cut-off voltage of 2.0V at a current of 105A; standing a lithium ion battery for a first time period of 30 minutes, and then charging the lithium ion battery to a first charging cut-off voltage of 3.65V at a constant current and a constant voltage of 105A;
s102, standing the lithium ion battery for a second time period of 60 minutes, then continuously discharging for a third time period of 30 seconds by using current 415A, and obtaining a first voltage value V1 when the lithium ion battery is standing and a second voltage value V2 when the lithium ion battery is discharged;
s103, standing the lithium ion battery for a fourth time period of 40 seconds, continuously charging the lithium ion battery for a fifth time period of 15 seconds by using a current 210A, and acquiring a third voltage value V3 when the lithium ion battery is standing and a fourth voltage value V4 when the lithium ion battery is charged;
s104, standing the lithium ion battery for a sixth time period of 30 minutes, and then continuously discharging for t7 time at a current 105A, wherein the value of t7 is obtained according to the calculation method in the step S104;
s105, repeating the steps S102-S104 until the SOC of the lithium ion battery cell is 0;
in this embodiment, by cyclically executing the discharging operation in steps S102 and S104 and the charging operation in step S103, the reduction value of the SOC value of the battery cell after the end of discharging in each cycle is finally realized to be a fixed value, and preferably, the fixed value is 47.5%; thus, after the first execution of steps S102-S104, the cell SOC value may be reduced from 100% to 52.5%, after the second execution of steps S102-S104, the cell SOC value may be reduced from 52.5% to 5%, and when the third execution of steps S102-S104, since only 5% of the cell SOC value remains, then, when step S104 is executed, the cell SOC value is reduced to 0 and then no discharge occurs;
s106, repeating the following charge-discharge cycle for 100 times: standing the lithium ion battery for an eighth time period of 30 minutes, and charging the lithium ion battery to a second charging cut-off voltage of 3.6V at a constant current of a current 105A; standing the lithium ion battery for a ninth time period of 30 minutes, and continuously discharging at a current 105A until the second discharge cut-off voltage is 2.5V;
s107, repeating the steps S101-S106 until the discharge capacity retention rate is lower than 80% of the initial capacity;
step S103 is followed by: and calculating the discharge DCR and the charge DCR of the lithium ion battery according to the following calculation formula:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
The results of the calculations are shown in the table below. The 100% SOC, 52.5% SOC, and 5% SOC in the following table refer to the cell SOC values after the end of the standing in the foregoing S102 step. The DCR values in the table below are values obtained from testing a particular lithium ion battery under particular environmental conditions for reference only, and one skilled in the art will appreciate that the values obtained may vary from test environment to test environment and from test subject to test subject.
And obtaining the change trends of the discharging DCR and the charging DCR according to the discharging DCR and the charging DCR obtained through calculation. As shown in fig. 2 and 3.
Both discharging DCR and charging DCR are important performance indicators of lithium ion batteries. The charging DCR reflects the charging polarization and the charging heat production capacity of the battery cell, and the discharging DCR reflects the polarization and the heat production capacity of the discharging state of the battery cell. The DCR in the non-cyclic process is the short-term DCR of the battery cell, and polarization accumulation, side reaction accumulation and the like are less due to short time. By the embodiment, the charging and discharging DCR in the cycle process of the lithium ion battery is tested, and the long-term DCR of the battery cell can be reflected, so that the comprehensive conditions of ohmic internal resistance, polarization accumulation, side reaction accumulation, pole piece health state and the like of the battery cell can be known, and then whether the cycle performance is deteriorated or not can be judged according to whether the DCR has sudden change or not.
It should be understood that the time period values, the current values, the voltage values, the cell SOC value reduction values, the discharge capacity retention rate values, the cycle times, and the like appearing in steps S101 to S107 in the embodiment of the present invention are merely examples, and no limitation should be imposed on the execution of the steps in the embodiment of the present invention.
Example 2
This embodiment provides a DCR test system in a lithium ion battery cycle process, as shown in fig. 4, the DCR test system 1 includes:
the pretreatment module 11 is used for standing the lithium ion battery for a tenth time period and then continuously discharging to a first discharge cut-off voltage; standing a lithium ion battery for a first time period, and then charging the lithium ion battery to a first charge cut-off voltage;
the first discharging module 12 is configured to stand the lithium ion battery for a second time period, then continuously discharge for a third time period t3 at a first current value I1, and obtain a first voltage value V1 when the lithium ion battery stands still and a second voltage value V2 when the discharge ends;
the first charging module 13 is configured to place the lithium ion battery for a fourth time period, then continuously charge the lithium ion battery for a fifth time period t5 at a second current value I2, and obtain a third voltage value V3 when the lithium ion battery is placed and a fourth voltage value V4 when the charging is finished;
the second discharging module 14 is configured to leave the lithium ion battery still for a sixth time period, and then continuously discharge for a seventh time period t7 at a third current value I3, where a value of t7 is (C0 × m1/n1-I1 × t3+ I2 × t5)/I3, where C0 is a total capacity of the lithium ion battery cells, n1 is a positive integer, and m1 is a value between 50% and 100%;
the first circulation module 15 is configured to repeatedly and sequentially call the first discharging module, the first charging module and the second discharging module until the SOC of the lithium ion battery cell is not higher than the SOC value of the first cell;
the second cycle module 16 is configured to perform charge and discharge cycles on the lithium ion battery for several times through a charging unit 161 and a discharging unit 162, where the charging unit 161 is configured to stand the lithium ion battery for an eighth time period and continuously charge the lithium ion battery to a second charge cut-off voltage, and the discharging unit 162 is configured to stand the lithium ion battery for a ninth time period and continuously discharge the lithium ion battery to the second discharge cut-off voltage;
a third cycle module 17, configured to repeatedly and sequentially call the preprocessing module 11, the first discharging module 12, the first charging module 13, the second discharging module 14, the first cycle module 15, and the second cycle module 16 until a cycle termination condition is reached;
a calculating module 18, configured to calculate a discharging DCR and/or a charging DCR of the lithium ion battery, where the calculating formula is as follows:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
And the variation trend acquisition module 19 is configured to acquire a variation trend of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or charging DCR.
In the third circulation module 17, the circulation termination condition may specifically include at least one of the following: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold, and the value range of the corresponding first threshold can be 50% to 90%, the value range of the corresponding third threshold can be 50% to 90%, and specific values can be set according to actual needs.
Preferably, the first charge cut-off voltage in the preprocessing module 11 may be a full charge voltage value.
Taking a square aluminum shell lithium iron phosphate battery of 105Ah as an example, a specific implementation process of the DCR test system in the lithium ion battery cycle process of this embodiment is described in detail below, where a test environment temperature may be set to 25 ± 2 ℃, and the DCR test system specifically includes:
the pretreatment module 11 is used for standing the lithium ion battery for a tenth time period of 30 minutes, and then continuously discharging the lithium ion battery to a first discharge cut-off voltage of 2.0V at a current of 105A; standing a lithium ion battery for a first time period of 30 minutes, and then charging the lithium ion battery to a first charging cut-off voltage of 3.65V at a constant current and a constant voltage of 105A;
the first discharging module 12 is configured to allow the lithium ion battery to stand for a second time period of 60 minutes, and then continue to discharge for a third time period of 30 seconds at the current 415A, so as to obtain a first voltage value V1 when the lithium ion battery stands still and a second voltage value V2 when the discharge ends;
the first charging module 13 is configured to place the lithium ion battery for a fourth time period of 40 seconds, and then continuously charge the lithium ion battery for a fifth time period of 15 seconds at the current 210A to obtain a third voltage value V3 when the lithium ion battery is placed and a fourth voltage value V4 when the charging is finished;
the second discharging module 14 is configured to allow the lithium ion battery to stand for a sixth time period of 30 minutes, and then continue to discharge for a time t7 at a current 105A, where a value of t7 is obtained according to the calculation method of the second discharging module 14;
the first circulation module 15 is configured to repeatedly and sequentially call the first discharging module, the first charging module and the second discharging module until the SOC of the lithium ion battery cell is 0;
in this embodiment, the discharging operation of the first discharging module 12 and the second discharging module 14 and the charging operation of the first charging module 13 are called cyclically, so that the reduction value of the SOC value of the battery cell after the end of discharging in each cycle is finally a fixed value, preferably, the fixed value is 47.5%; thus, after the first discharging module 12, the first charging module 13, and the second discharging module 14 are called for the first time, the cell SOC value is reduced from 100% to 52.5%, after the three modules are called for the second time, the cell SOC value is reduced from 52.5% to 5%, and when the three modules are called for the third time, since the cell SOC value is only 5% remained, when the second discharging module 14 is called, the cell SOC value is reduced to 0, and then no discharging is performed;
a second cycle module 16, configured to perform 100 charge and discharge cycles on the lithium ion battery through a charging unit 161 and a discharging unit 162, where the charging unit 1161 is configured to keep the lithium ion battery still for an eighth time period of 30 minutes, and charge the lithium ion battery to a second charge cut-off voltage of 3.6V at a constant current of a current 105A, and the discharging unit 1162 is configured to keep the lithium ion battery still for a ninth time period of 30 minutes, and continuously discharge the lithium ion battery to a second discharge cut-off voltage of 2.5V at the current 105A;
a third cycle module 17, configured to repeatedly and sequentially call the preprocessing module 11, the first discharging module 12, the first charging module 13, the second discharging module 14, the first cycle module 15, and the second cycle module 16 until the discharge capacity retention rate of the lithium ion battery is lower than 80% of the initial capacity;
a calculating module 18, configured to calculate a discharging DCR and a charging DCR of the lithium ion battery, where the calculation formula is as follows:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
The results of the calculations are shown in the table below. The 100% SOC, 52.5% SOC, and 5% SOC in the following table refer to the cell SOC values after the end of the standing in the foregoing S102 step. The DCR values in the table below are values obtained from testing a particular lithium ion battery under particular environmental conditions for reference only, and one skilled in the art will appreciate that the values obtained may vary from test environment to test environment and from test subject to test subject.
And the variation trend acquisition module 19 is configured to acquire variation trends of the discharging DCR and the charging DCR according to the calculated discharging DCR and/or charging DCR. As shown in fig. 2 and 3.
Both discharging DCR and charging DCR are important performance indicators of lithium ion batteries. The charging DCR reflects the charging polarization and the charging heat production capacity of the battery cell, and the discharging DCR reflects the polarization and the heat production capacity of the discharging state of the battery cell. The DCR in the non-cyclic process is the short-term DCR of the battery cell, and polarization accumulation, side reaction accumulation and the like are less due to short time. By the embodiment, the charging and discharging DCR in the cycle process of the lithium ion battery is tested, and the long-term DCR of the battery cell can be reflected, so that the comprehensive conditions of ohmic internal resistance, polarization accumulation, side reaction accumulation, pole piece health state and the like of the battery cell can be known, and then whether the cycle performance is deteriorated or not can be judged according to whether the DCR has sudden change or not.
It is understood that the time period values, the current values, the voltage values, the cell SOC value reduction values, the discharge capacity retention rate values, the cycle times, and the like in the specific application example of the square aluminum-shell lithium iron phosphate battery of 105Ah are merely examples, and should not bring any limitation to the implementation of the steps in the embodiment of the present invention, and those skilled in the art may adopt different values as needed as long as the method of the present invention can be normally implemented.
Example 3
The present invention further provides an electronic device, as shown in fig. 5, the electronic device may include a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program to implement the steps of the DCR testing method in the lithium ion battery cycling process in embodiment 1.
It should be understood that the electronic device shown in fig. 5 is only an example, and should not bring any limitation to the function and the scope of the application of the embodiment of the present invention.
As shown in fig. 5, the electronic device 2 may be embodied in the form of a general purpose computing device, such as: which may be a server device. The components of the electronic device 2 may include, but are not limited to: the at least one processor 3, the at least one memory 4, and a bus 5 connecting the various system components (including the memory 4 and the processor 3).
The bus 5 may include a data bus, an address bus, and a control bus.
The memory 4 may include volatile memory, such as Random Access Memory (RAM)41 and/or cache memory 42, and may further include Read Only Memory (ROM) 43.
The memory 4 may also include a program tool 45 (or utility tool) having a set (at least one) of program modules 44, such program modules 44 including, but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which, or some combination thereof, may comprise an implementation of a network environment.
The processor 3 executes various functional applications and data processing, such as the steps of the DCR testing method during the cycling of the lithium ion battery in the foregoing embodiment 1, by running the computer program stored in the memory 4.
The electronic device 2 may also communicate with one or more external devices 6 (e.g., keyboard, pointing device, etc.), such communication may be through input/output (I/O) interfaces 7, and the model-generated electronic device 2 may also communicate with one or more networks (e.g., a local area network L AN, a wide area network WAN, and/or a public network) through a network adapter 8.
As shown in FIG. 5, the network adapter 8 may communicate with other modules of the model-generated electronic device 2 via a bus 5. It will be appreciated by those skilled in the art that although not shown in the figures, other hardware and/or software modules may be used in conjunction with the model-generated electronic device 2, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems, etc.
It should be noted that although in the above detailed description several units/modules or sub-units/modules of the electronic device are mentioned, such division is merely exemplary and not mandatory. Indeed, the features and functionality of two or more of the units/modules described above may be embodied in one unit/module according to embodiments of the invention. Conversely, the features and functions of one unit/module described above may be further divided into embodiments by a plurality of units/modules.
Example 4
The present embodiment provides a computer-readable storage medium, on which a computer program is stored, and the program, when executed by a processor, implements the steps of the DCR testing method in the cycling process of the lithium ion battery in the foregoing embodiment 1.
More specific ways in which the computer-readable storage medium may be employed may include, but are not limited to: a portable disk, a hard disk, random access memory, read only memory, erasable programmable read only memory, optical storage device, magnetic storage device, or any suitable combination of the foregoing.
In a possible implementation manner, the present invention can also be implemented in the form of a program product, which includes program codes, when the program product runs on a terminal device, the program codes are used for causing the terminal device to execute the steps of implementing the DCR testing method in the lithium ion battery cycling process in the foregoing embodiment 1.
Where program code for carrying out the invention is written in any combination of one or more programming languages, the program code may execute entirely on the user device, partly on the user device, as a stand-alone software package, partly on the user device and partly on a remote device or entirely on the remote device.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (18)
1. A DCR test method in a lithium ion battery cycle process is characterized by comprising the following steps:
s1, standing the lithium ion battery for a first time period, and then charging the lithium ion battery to a first charging cut-off voltage;
s2, standing the lithium ion battery for a second time period, then continuously discharging for a third time period t3 at a first current value I1, and obtaining a first voltage value V1 when the lithium ion battery stands and a second voltage value V2 when the lithium ion battery discharges;
s3, standing the lithium ion battery for a fourth time period, then continuously charging the lithium ion battery for a fifth time period t5 at a second current value I2, and acquiring a third voltage value V3 when the lithium ion battery is standing and a fourth voltage value V4 when the lithium ion battery is charging;
s4, standing the lithium ion battery for a sixth time period, and then continuously discharging for a seventh time period t7 at a third current value I3, wherein I3 t7+ I1 t3-I2 t5> 0;
s5, repeating the steps S2-S4 for a plurality of times until the SOC of the lithium ion battery cell is not higher than the first cell SOC value;
s6, carrying out charge-discharge circulation on the lithium ion battery for a plurality of times;
step S3 is followed by: and calculating the discharge DCR and/or the charge DCR of the lithium ion battery according to the following calculation formula:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
2. The DCR testing method of claim 1, wherein each charge-discharge cycle in step S6 comprises the steps of:
s61, standing the lithium ion battery for an eighth time period, and continuously charging to a second charging cut-off voltage;
and S62, standing the lithium ion battery for a ninth time period, and continuously discharging to a second discharge cut-off voltage.
3. The DCR testing method of claim 1, further comprising: steps S1-S6 are repeatedly executed until a loop termination condition is reached.
4. The DCR testing method of claim 3, wherein the cycle-ending condition comprises at least one of: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold.
5. The DCR testing method of claim 1, wherein the first charge cut-off voltage in step S1 is a full charge voltage value of a lithium ion battery.
6. The DCR testing method of claim 5, wherein the step of charging the lithium ion battery in step S1 further comprises the steps of:
and standing the lithium ion battery for a tenth time period, and continuously discharging to the first discharge cut-off voltage.
7. The DCR testing method of claim 1, wherein in step S4, the value of the seventh time period t7 is (C0 × m1/n1-I1 × t3+ I2 × t5)/I3, wherein C0 is the total cell capacity of the lithium ion battery, n1 is a positive integer, and m1 is a value between 50% and 100%.
8. The DCR testing method of claim 1, further comprising: and acquiring the change trend of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or charging DCR.
9. A DCR test system in a lithium ion battery cycle process, the DCR test system comprising:
the device comprises a preprocessing module, a voltage-limiting module and a voltage-limiting module, wherein the preprocessing module is used for standing a lithium ion battery for a first time period and then charging the lithium ion battery to a first charging cut-off voltage;
the first discharging module is used for standing the lithium ion battery for a second time period, then continuously discharging for a third time period t3 at a first current value I1, and acquiring a first voltage value V1 when the lithium ion battery stands and a second voltage value V2 when the lithium ion battery discharges;
the first charging module is used for standing the lithium ion battery for a fourth time period, then continuously charging the lithium ion battery for a fifth time period t5 at a second current value I2, and acquiring a third voltage value V3 when the lithium ion battery stands still and a fourth voltage value V4 when the charging is finished;
the second discharging module is used for standing the lithium ion battery for a sixth time period, and then continuously discharging for a seventh time period t7 at a third current value I3, wherein I3 t7+ I1 t3-I2 t5> 0;
the first circulation module is used for repeatedly and sequentially calling the first discharging module, the first charging module and the second discharging module for a plurality of times until the SOC of the lithium ion battery cell is not higher than the SOC value of the first cell;
the second circulation module is used for carrying out charging and discharging circulation on the lithium ion battery for a plurality of times;
the calculation module is used for calculating the discharging DCR and/or the charging DCR of the lithium ion battery, and the calculation formula is as follows:
discharge DCR ═ (V1-V2)/I1;
charging DCR ═ (V4-V3)/I2.
10. The DCR testing system of claim 9, wherein the second cycling module is configured to cycle the lithium ion battery through a charging unit and a discharging unit, wherein,
the charging unit is used for standing the lithium ion battery for an eighth time period and continuously charging the lithium ion battery to a second charging cut-off voltage;
and the discharging unit is used for standing the lithium ion battery for a ninth time period and continuously discharging to a second discharging cut-off voltage.
11. The DCR testing system of claim 9, further comprising a third cycle module for repeatedly invoking the preprocessing module, the first discharging module, the first charging module, the second discharging module, the first cycle module, the second cycle module, and the calculating module in sequence until a cycle termination condition is reached.
12. The DCR test system of claim 11, wherein the cycle-ending condition comprises at least one of: the discharge capacity retention rate of the lithium ion battery is not higher than a first threshold, the cycle number of the lithium ion battery is not lower than a second threshold, and the energy retention rate of the lithium ion battery is not higher than a third threshold.
13. The DCR test system of claim 9, wherein the first charge cutoff voltage is a full charge voltage value of a lithium ion battery.
14. The DCR testing system of claim 13, wherein the preprocessing module is further configured to rest the lithium ion battery for a tenth time period before charging the lithium ion battery for discharging to the first discharge cutoff voltage.
15. The DCR testing system of claim 9, wherein the value of the seventh time period t7 in the second discharging module is (C0 m1/n1-I1 t3+ I2 t5)/I3, wherein C0 is the total capacity of the li-ion battery cells, n1 is a positive integer, and m1 is a value between 50% and 100%.
16. The DCR testing system of claim 9, further comprising a trend of change obtaining module for obtaining a trend of change of the discharging DCR and/or the charging DCR according to the calculated discharging DCR and/or the charging DCR.
17. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the DCR testing method according to any of claims 1 to 8 when executing the computer program.
18. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the DCR testing method according to any one of claims 1 to 8.
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