CN113109728A - Method and device for testing shallow DOD (disk on disk) cycle life - Google Patents
Method and device for testing shallow DOD (disk on disk) cycle life Download PDFInfo
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Abstract
The invention discloses a method and a device for testing the cycle life of shallow DOD. The test method for the shallow DOD cycle life comprises the following steps: calibrating the actual capacity and the actual direct current resistance of the battery cell; taking the actual capacity multiplied by the preset depth as a charge-discharge cut-off capacity, and carrying out charge-discharge circulation on the battery cell; after charge and discharge circulation, calibrating the actual capacity and the actual direct current resistance of the battery cell again; and multiplying the actual capacity of the battery cell calibrated after the previous charge-discharge cycle process by a preset depth to be used as a charge-discharge cutoff capacity in the subsequent charge-discharge cycle process, and performing charge-discharge cycle on the battery cell until the battery cell reaches a service life ending state, wherein the preset depth is the difference between the upper limit and the lower limit of a charge-discharge interval. The method of the invention achieves the effect of more reasonable and effective evaluation test.
Description
Technical Field
The embodiment of the invention relates to a battery inspection technology, in particular to a method and a device for testing the cycle life of shallow DOD (disk on demand).
Background
With the development of new energy industry, the power battery industry is also increased vigorously, and the requirements on the power battery tend to be higher in energy density and longer in service life.
The current evaluation method for the service life of the power battery is generally a cycle of 100% DOD, namely a full charge-discharge cycle is carried out in a specified voltage use range, but the 100% charge-discharge working condition is rarely used in the use process of a vehicle, so that the development of the evaluation method for the service life of the shallow DOD cycle is very important.
At present, the shallow DOD cycle is usually evaluated in a voltage cut-off mode, but with the cyclic progress, the battery core is continuously aged, the polarization in the charging and discharging process is continuously increased, so that the capacity and energy throughput attenuation in the shallow DOD cycle process is faster, and the accuracy of an evaluation result is poorer.
Disclosure of Invention
The invention provides a method and a device for testing the cycle life of shallow DOD (disk on disk) so as to improve the accuracy of the cycle life test.
In a first aspect, an embodiment of the present invention provides a method for testing a shallow DOD cycle life, where the method includes:
calibrating the actual capacity and the actual direct current resistance of the battery cell;
taking the actual capacity multiplied by the preset depth as a charge-discharge cut-off capacity, and carrying out charge-discharge circulation on the battery cell;
after charge and discharge circulation, calibrating the actual capacity and the actual direct current resistance of the battery cell again;
and multiplying the actual capacity of the battery cell calibrated after the previous charge-discharge cycle process by a preset depth to be used as a charge-discharge cutoff capacity in the subsequent charge-discharge cycle process, and performing charge-discharge cycle on the battery cell until the battery cell reaches a service life ending state, wherein the preset depth is the difference between the upper limit and the lower limit of a charge-discharge interval.
Optionally, the charge and discharge cycle is charged and discharged in a constant current and constant voltage mode.
Optionally, calibrating the actual capacity and the actual dc resistance of the battery cell includes:
performing first constant current charging on the battery cell until the battery cell reaches a first working upper limit voltage;
carrying out first constant voltage charging on the battery cell until the charging current is close to 0A and the error is not more than 0.1;
performing first standing treatment on the battery cell;
performing first constant current discharge on the battery cell until the battery cell reaches a first working lower limit voltage;
performing first standing treatment on the battery cell;
and repeating the steps, wherein the electric quantity discharged by the secondary discharge is the actual capacity of the battery cell.
Optionally, calibrating the actual dc resistance and the actual dc resistance of the battery cell includes:
under the condition of full capacity of the battery cell, performing first constant current discharge on the battery cell until the electric quantity of the battery cell reaches 1/2 of the actual capacity;
performing second standing treatment on the battery cell;
measuring the voltage at two ends of the battery cell and recording the voltage as a first voltage value U1；
Applying a first current value I to the battery cell1Discharging for a first preset time period;
measuring the voltage at two ends of the battery cell and recording the voltage as a second voltage value U2；
The actual dc resistance value DCIR of the cell is (U)1-U2)/I1。
Optionally, the number of cycles of the charge-discharge cycle is an integer greater than 0.
Optionally, the end-of-life state comprises: the actual capacity is lower than the product of a first preset percentage and the initial actual capacity or/and the actual direct current resistance is higher than the product of a second preset percentage and the initial actual direct current resistance, the initial actual capacity and the initial actual direct current resistance are the actual capacity and the actual direct current resistance calibrated for the first time, and the first preset percentage and the second preset percentage are both larger than or equal to 0 and smaller than 1.
Optionally, the upper limit of the charge-discharge interval is a third preset percentage, the lower limit of the charge-discharge interval is a fourth preset percentage, both the third preset percentage and the fourth preset percentage are greater than or equal to 0 and less than 1, and the third preset percentage is greater than the fourth preset percentage.
Optionally, the time of the first standing treatment is less than or equal to the time of the second standing treatment.
In a second aspect, an embodiment of the present invention further provides a device for testing a shallow DOD cycle life, which is used to implement any one of the foregoing methods for testing a shallow DOD cycle life, and the device includes: the battery cell calibration module and the charge-discharge cycle module; the battery cell calibration module is used for calibrating the actual capacity and the actual direct current resistance of the battery cell and re-calibrating the actual capacity and the actual direct current resistance of the battery cell after charge-discharge circulation; the charge-discharge circulation module is used for performing charge-discharge circulation on the battery cell by taking the actual capacity multiplied by the preset depth as a charge-discharge cutoff capacity, taking the actual capacity of the battery cell calibrated after the previous charge-discharge circulation process multiplied by the preset depth as the charge-discharge cutoff capacity in the next charge-discharge circulation process, and performing charge-discharge circulation on the battery cell until the battery cell reaches a service life end state; wherein, the preset depth is the difference between the upper limit and the lower limit of the charge-discharge interval.
Optionally, the cell calibration module includes: the device comprises a capacity calibration unit and a direct current resistance calibration unit; the capacity calibration unit is used for calibrating the actual capacity of the battery cell; the direct current resistance calibration unit is used for calibrating the actual direct current resistance of the battery cell.
The testing method provided by the invention firstly calibrates the initial real-time capacity and the real-time direct current resistance of the battery cell, and takes the actual capacity of the battery cell as a cut-off condition in the charging and discharging cycle, the real-time capacity of the battery cell is continuously calibrated and updated along with the health degree of the battery cell, and the real-time capacity of the battery cell is taken as the cut-off condition in the next charging and discharging cycle, so that the service life evaluation of the battery cell in a target discharging depth range can be completed under different health states, and the more reasonable and effective effect of the service life testing method is achieved.
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FIG. 1 is a flow chart of a method of testing shallow DOD cycle life in accordance with an embodiment of the present invention;
fig. 2 is a flowchart of a method for calibrating actual capacity of a battery cell according to an embodiment of the present invention;
fig. 3 is a flowchart of a method for calibrating an actual dc resistance of a battery cell according to an embodiment of the present invention;
FIG. 4 is a flow chart of another method for testing shallow DOD cycle life according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a testing apparatus for shallow DOD cycle life according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The embodiment of the invention provides a method for testing the cycle life of shallow DOD. Fig. 1 is a flow chart of a method for testing a shallow DOD cycle life according to an embodiment of the present invention, and referring to fig. 1, the method for testing a shallow DOD cycle life includes:
s101, calibrating the actual capacity and the actual direct current resistance of the battery cell;
for example, when a shallow DOD cycle life test is performed on a battery cell, a constant-current constant-voltage charging and constant-current discharging cycle mode is firstly adopted to perform charging and discharging twice, and the second discharge capacity is the initial real-time capacity of the battery cell. And then, under the condition of full capacity of the battery cell, performing constant current discharge on the battery cell twice, wherein a period of time is required for standing between the two constant current discharges, for example, standing for 60 minutes, so that the initial actual direct current resistance of the battery cell can be represented by a current value of the two discharges and a voltage value after the two discharges.
S102, taking the actual capacity multiplied by a preset depth as a charge-discharge cutoff capacity, and carrying out charge-discharge circulation on the battery cell;
wherein, the charge-discharge circulation adopts a constant current and constant voltage mode to carry out charge-discharge.
For example, because the charge and discharge cycles of the battery cell are performed within a preset cycle interval, before the charge and discharge cycles of the battery cell, the battery cell needs to be subjected to constant current charging to the lower limit of the charge and discharge cycle interval. For example, if the Charge-discharge cycle interval is 20% to 60% of the State of Charge (SOC), the lower limit of the Charge-discharge cycle interval is 20% SOC. Then entering into formal charge-discharge cycle process: firstly, after the temperature of the battery core is restored to a preset test temperature after the battery core is placed for a set time, then the battery core is charged with constant current and constant voltage until the charging capacity is equal to or greater than the actual capacity multiplied by a preset depth, wherein the charging capacity is the electric quantity charged into the battery core in the charging process, and the preset depth is the depth of charge-discharge cycle, namely the difference between the upper limit and the lower limit of a charge-discharge cycle interval. Exemplarily, if the charge-discharge cycle interval is 20% to 60% SOC, the preset depth is 60% to 20% to 40%; and finally, after the battery core temperature is restored to the preset test temperature after the battery core is placed for the set time, constant-current and constant-voltage discharge is carried out on the battery core until the discharge capacity is equal to or larger than the actual capacity multiplied by the preset depth, and at the moment, one charge-discharge cycle is completed. The charge and discharge cycle is performed for a predetermined number of times, which may be 50 times.
S103, after the charge and discharge cycle, calibrating the actual capacity and the actual direct current resistance of the battery cell again;
specifically, after the charge and discharge cycles are performed for the preset number of times, the battery cell is aged to a certain extent, and the actual capacity is changed accordingly, so that the actual capacity of the battery cell and the actual dc resistance need to be calibrated again, and the specific method for calibrating is the same as S101, which is not described herein again.
And S104, multiplying the actual capacity of the battery cell calibrated after the previous charge-discharge cycle process by a preset depth to be used as a charge-discharge cutoff capacity in the next charge-discharge cycle process, and performing charge-discharge cycle on the battery cell until the battery cell reaches a service life end state.
Wherein the preset depth is the difference between the upper limit and the lower limit of the charge-discharge interval.
Specifically, first, after the set time of shelving, the cell temperature is restored to a temperature at which the test can be performed. And then, performing constant-current and constant-voltage charging on the battery cell until the charging capacity is equal to or greater than the actual capacity multiplied by a preset depth, wherein the actual capacity is the actual capacity of the battery cell calibrated after the previous charging and discharging cycle process, the charging capacity is the electric quantity charged into the battery cell in the current charging process, and the preset depth is the depth of the charging and discharging cycle, namely the difference between the upper limit and the lower limit of the charging and discharging cycle interval. Exemplarily, if the charge-discharge cycle interval is 20% to 60% SOC, the preset depth is 60% to 20% to 40%; and finally, after the battery core temperature is restored to the preset test temperature after the battery core is placed for the set time, constant-current and constant-voltage discharge is carried out on the battery core until the discharge capacity is equal to or larger than the actual capacity multiplied by the preset depth, and at the moment, one charge-discharge cycle is completed. After each preset number of times of implementation of the charge-discharge cycle, the actual capacity and the actual direct current resistance of the battery cell need to be calibrated again, and then the next preset number of charge-discharge cycles are performed until the battery cell reaches the end-of-life state, where the actual capacity is lower than the product of the first preset percentage and the initial actual capacity or/and the actual direct current resistance is higher than the product of the second preset percentage and the initial actual direct current resistance, the initial actual capacity and the initial actual direct current resistance are the actual capacity and the actual direct current resistance calibrated for the first time, both the first preset percentage and the second preset percentage are greater than or equal to 0 and less than 1, and exemplarily, the first preset percentage and the second preset percentage are 70% and 50%, respectively.
In the method for testing the shallow DOD cycle life provided by this embodiment, the initial real-time capacity and the real-time direct current resistance of the battery cell are calibrated first, the actual capacity of the battery cell is used as a cut-off condition in a charge-discharge cycle, the actual capacity of the battery cell is calibrated and updated continuously along with the health degree of the battery cell, and the re-calibrated real-time capacity is used as a cut-off condition in a subsequent charge-discharge cycle, so that the influence degree of a polarization phenomenon on the cut-off condition of the charge-discharge cycle is reduced, the problem that the life evaluation loses its effectiveness due to the fast capacity throughput attenuation in the shallow DOD cycle process is solved effectively, the life evaluation of the battery cell in a target discharge depth range under different health states can be completed, and a more reasonable and effective effect of the evaluation.
Fig. 2 is a flowchart of a method for calibrating actual capacity of a battery cell according to an embodiment of the present invention, referring to fig. 2, optionally, the method includes:
s201, performing first constant current charging on the battery cell until the battery cell reaches a first working upper limit voltage;
the first constant current charging is to charge the battery cell with a first constant current. Illustratively, the first constant current is a constant current of 1/3C; the first upper working limit voltage is a battery cell specified upper working limit voltage.
S202, performing first constant voltage charging on the battery cell until the charging current is close to 0A and the error is not more than 0.1;
the first constant voltage charging may be charging the cell with a first constant voltage, which is, for example, a constant voltage within a specified upper limit voltage of the cell; and charging the battery cell by using the first constant voltage until the charging current is reduced to a level close to 0A, wherein the error is not more than 0.1.
S203, performing first standing treatment on the battery cell;
specifically, after charging, the temperature of the battery cell temporarily rises, a certain polarization phenomenon occurs in the battery cell at this time, the battery cell needs to be subjected to standing treatment to reduce the polarization phenomenon and accelerate battery attenuation caused by high temperature, the first standing treatment may be standing for 30 minutes, the time of the first standing treatment is not limited, and the first standing treatment may be set correspondingly according to the type and the capacity of the battery cell.
S204, performing first constant current discharge on the battery cell until the battery cell reaches a first working lower limit voltage;
the first constant current charging is to charge the battery cell with a first constant current, and the first constant current is 1/3C, for example; the first working lower limit voltage is a working lower limit voltage specified by the battery cell.
S205, performing first standing treatment on the battery cell;
specifically, after the discharge, the temperature of the battery cell temporarily rises, and at this time, a certain polarization phenomenon also occurs in the battery cell, and the battery cell needs to be statically placed to reduce the polarization phenomenon and the attenuation acceleration of the battery caused by high temperature, where the first static placement treatment may be static placement for 30 minutes, and the time of the first static placement treatment is not limited, and may be set correspondingly according to the type and the capacity of the battery cell.
And S206, repeating the steps, wherein the electric quantity discharged by the secondary discharge is the actual capacity of the battery cell.
Specifically, S201, S202, S203, S204, and S205 are repeated, and the electric quantity discharged in the first constant current discharge process this time is the actual capacity of the battery cell measured this time.
In the method for testing the shallow DOD cycle life provided by this embodiment, the initial capacity of the battery cell is measured by a constant-current and constant-voltage charging and discharging manner, standing processing is performed after each charging and discharging to reduce the polarization phenomenon caused by heating of the battery cell, and the discharged electric quantity of the second charging and discharging is used as the actual capacity of the battery cell to be tested, so that the measured value is more stable, the measurement of the initial capacity of the battery cell is realized, and the effect of stable and accurate measurement result is achieved.
Fig. 3 is a flowchart of a method for calibrating an actual dc resistance of a battery cell according to an embodiment of the present invention, referring to fig. 3, optionally, the method includes:
s301, under the condition that the battery cell is full of capacity, performing first constant current charging on the battery cell until the electric quantity of the battery cell reaches 1/2 of the actual capacity;
specifically, under the condition that the battery cell is full of capacity, constant current discharge is performed on the battery cell at a first constant current until the remaining capacity of the battery cell reaches half of the initial actual capacity of the battery cell.
S302, performing second standing treatment on the battery cell;
specifically, after the discharge, the temperature of the battery cell temporarily rises, and at this time, a certain polarization phenomenon also occurs in the battery cell, and the battery cell needs to be statically placed to reduce the polarization phenomenon and the attenuation acceleration of the battery caused by high temperature, the second static placement treatment may be static placement for 60 minutes, and the time of the first static placement treatment is less than or equal to the time of the second static placement treatment, and may be set correspondingly according to the type and the capacity of the battery cell.
S303, measuring the voltages at two ends of the battery cell and recording the voltages as a first voltage value U1；
Specifically, the influence of polarization phenomenon of the cell after standing is reduced, and the voltage at both ends of the cell is measured and recorded at the momentAs the first voltage value U1。
S304, applying a first current value I to the battery cell1Discharging for a first preset time period;
specifically, the battery cell is subjected to constant current discharge by using a preset first current value, and the discharge lasts for a first preset time period, where the first current value may be a current value corresponding to 1/3C, and the first preset time period may be 30 seconds.
S305, measuring the voltages at two ends of the battery cell and recording the voltages as a second voltage value U2；
S306, actual dc resistance value DCIR of battery cell ═ U (U)1-U2)/I1。
Specifically, the actual dc resistance value of the battery cell may be represented by the first voltage value U1A second voltage value U2And the first current value I1 is expressed as DCIR ═ U (U)1-U2)/I1。
According to the method for testing the shallow DOD cycle life, the direct current resistance of the battery cell is measured by adopting a constant current discharge mode, the influence of a polarization phenomenon generated by heating in the measurement process on a result can be reduced by standing, the direct current resistance of the battery cell is accurately measured, and the effect of more accurately measuring the direct current resistance of the battery cell is achieved.
Fig. 4 is a flowchart of another method for testing the cycle life of shallow DOD cycles according to an embodiment of the present invention, and referring to fig. 4, the method includes:
s401, calibrating initial actual capacity Q0And an initial actual DC resistance DCIR0；
Illustratively, the cell is charged with constant current at 1/3C until the voltage across the cell reaches the specified upper operating voltage of the cell, and then charged with constant voltage until the charging current drops to 0.02C. And then, standing the battery cell for 30 minutes, discharging to a specified working lower limit voltage by adopting 1/3C constant current, and standing for 30 minutes. Repeating the charge and discharge process once again, wherein the second discharge capacity is the initial actual capacity Q of the battery cell0. After the battery cell is fully charged, the battery cell is subjected to constant current of 1/3CDischarging to 50% of the initial actual capacity, standing for 60 minutes, measuring the voltage at two ends of the battery cell, and recording as a first voltage value U1Using a current I corresponding to 1C magnification1After the battery cell is subjected to constant current discharge for 30s, the voltages at two ends of the battery cell are measured and recorded as a second voltage value U2Initial DC resistance DCIR of cell0＝(U1-U2)/I1。
S402, using initial actual capacity Q0As the off-condition, 50 charge-discharge cycles were performed.
Illustratively, the battery cell is subjected to constant current charging with a constant current of 1/3C to the lower limit of the charge-discharge cycle interval so as to obtain the initial actual capacity Q0As the cut-off condition, a 50-week charge-discharge cycle was then carried out: constant-current and constant-voltage charging is carried out on the battery cell by adopting preset constant current and constant voltage until the charging capacity is equal to or larger than the initial actual capacity Q0Multiplying by the depth of discharge; the charging capacity refers to the amount of electricity charged into the battery cell. It should be noted that, if the charging capacity is equal to or greater than the initial actual capacity Q0If the condition of multiplying by the depth of discharge cannot be satisfied, the charging is stopped when the charging current is 0.05C or less. And then laying aside for a preset time, and after the temperature of the battery cell is recovered to the required test temperature, performing constant-current and constant-voltage discharge with preset constant current and constant voltage until the discharge capacity is more than or equal to the initial actual capacity Q0Multiplying by the depth of discharge; the discharge capacity refers to the amount of electricity discharged from the battery cell. Similarly, if the charging capacity is equal to or greater than the initial actual capacity Q0If the condition of multiplying by the discharge depth cannot be reached, stopping discharging when the discharge current is less than or equal to 0.05C; and finally, the preset time is set aside, and the temperature of the battery cell is recovered to the required test temperature. The above charging and discharging process was repeated 50 times.
S403, recalibrating the actual capacity Q of the battery cell in the current state1And actual DC resistance DCIR1。
Specifically, after 50 charge-discharge cycles, the health degree of the battery cell is reduced, and then the capacity and the direct current resistance of the battery cell are changed, at this time, the actual capacity Q of the battery cell needs to be adjusted1And actual DC resistance DCIR1And carrying out recalibration. Constant current of 1/3C is adopted to charge the battery cell in a constant current mode until the voltage at two ends of the battery cell reaches the specified working upper limit voltage of the battery cell, and constant voltage charging is carried out on the battery cell by adopting constant voltage until the charging current drops to 0.02C. And then, standing the battery cell for 30 minutes, discharging to a specified working lower limit voltage by adopting 1/3C constant current, and standing for 30 minutes. Repeating the charge and discharge process once again, wherein the second discharge capacity is the actual capacity Q of the battery cell1. After the battery cell is fully charged, constant current discharge is carried out on the fully charged battery cell by adopting 1/3C constant current to 50% of actual capacity, the voltage at two ends of the battery cell is measured after the battery cell is placed for 60 minutes, and the voltage is recorded as a first voltage value U1Using a current I corresponding to 1C magnification1After the battery cell is subjected to constant current discharge for 30s, the voltages at two ends of the battery cell are measured and recorded as a second voltage value U2And then the direct current resistance DCIR of the cell1＝(U1-U2)/I1。
S404, actual capacity Q1The 50 th to 100 th charge-discharge cycles were performed as the off-conditions.
Illustratively, the battery cell is subjected to constant current charging with a constant current of 1/3C to the lower limit of the charge-discharge cycle interval so as to obtain the actual capacity Q1As the cut-off condition, a 50-week charge-discharge cycle was then carried out: constant-current and constant-voltage charging is carried out on the battery cell by adopting preset constant current and constant voltage until the charging capacity is equal to or larger than the actual capacity Q1Multiplying by the depth of discharge; the charging capacity refers to the amount of electricity charged into the battery cell. It should be noted that, if the charging capacity is equal to or greater than the actual capacity Q1If the condition of multiplying by the depth of discharge cannot be satisfied, the charging is stopped when the charging current is 0.05C or less. And then laying aside for a preset time, and after the temperature of the battery cell is recovered to the required test temperature, performing constant-current and constant-voltage discharge with preset constant current and constant voltage until the discharge capacity is more than or equal to the actual capacity Q1Multiplying by the depth of discharge; the discharge capacity refers to the amount of electricity discharged from the battery cell. Similarly, if the charging capacity is equal to or greater than the actual capacity Q1The condition of multiplying by the depth of discharge cannot be reached, thenStopping discharging when the discharge current is less than or equal to 0.05C; and finally, the preset time is set aside, and the temperature of the battery cell is recovered to the required test temperature. The above charging and discharging process was repeated 50 times.
S405, recalibrating the actual capacity Q of the battery cell in the current state2And actual DC resistance DCIR2。
Specifically, after 50 charge-discharge cycles, the health degree of the battery cell is reduced, and then the capacity and the direct current resistance of the battery cell are changed, at this time, the actual capacity Q of the battery cell needs to be adjusted2And actual DC resistance DCIR2And carrying out recalibration. Constant current of 1/3C is adopted to charge the battery cell in a constant current mode until the voltage at two ends of the battery cell reaches the specified working upper limit voltage of the battery cell, and constant voltage charging is carried out on the battery cell by adopting constant voltage until the charging current drops to 0.02C. And then, standing the battery cell for 30 minutes, discharging to a specified working lower limit voltage by adopting 1/3C constant current, and standing for 30 minutes. Repeating the charge and discharge process once again, wherein the second discharge capacity is the actual capacity Q of the battery cell2. After the battery cell is fully charged, constant current discharge is carried out on the fully charged battery cell by adopting 1/3C constant current to 50% of actual capacity, the voltage at two ends of the battery cell is measured after the battery cell is placed for 60 minutes, and the voltage is recorded as a first voltage value U1Using a current I corresponding to 1C magnification1After the battery cell is subjected to constant current discharge for 30s, the voltages at two ends of the battery cell are measured and recorded as a second voltage value U2And then the direct current resistance DCIR of the cell2＝(U1-U2)/I1。
And S406, repeating the operations of S404 and S405, and applying the actual capacity calibrated in the previous step to the charge-discharge cycle in the next step as a cut-off condition until the battery cell reaches the end-of-life state.
Specifically, 50 times of charge-discharge cycles are repeatedly performed, the actual capacity and the actual direct-current resistance of the battery cell in the current state are re-calibrated after every 50 times of charge-discharge cycles, the re-calibrated actual capacity is used in the next step of charge-discharge cycles as a cut-off condition until the retention rate of the actual capacity of the battery cell is lower than the preset percentage of the initial actual capacity or the increase rate of the actual direct-current resistance is higher than the preset percentage of the initial actual direct-current resistance, and the test is finished.
The method for testing the life of the shallow DOD cycle provided in this embodiment is to calibrate the actual capacity and the dc resistance of the battery cell in a constant-current and constant-voltage charging and discharging manner, perform charging and discharging cycles with the actual capacity of the battery cell multiplied by a preset depth as a cut-off condition after the calibration, recalibrate the actual capacity and the dc resistance of the battery cell after each 50 times of power supply cycles, and use the recalibration as the cut-off condition of the charging and discharging cycles until the battery cell reaches a life end state, and continuously update the actual capacity as the cut-off condition along with the change of the health degree of the battery during the test, thereby realizing the test of the life of the battery cell, achieving the effects of more accurate test result and easier test realization.
The embodiment of the invention also provides a device for testing the cycle life of shallow DOD, which can implement the method of the embodiment. Fig. 5 is a schematic structural diagram of a testing apparatus for shallow DOD cycle life according to an embodiment of the present invention, and referring to fig. 5, optionally, the apparatus includes: the battery cell calibration module 501 is used for calibrating the actual capacity and the actual direct current resistance of the battery cell, and re-calibrating the actual capacity and the actual direct current resistance of the battery cell after charge and discharge cycle; the charge-discharge cycle module 502 is configured to perform charge-discharge cycle on the battery cell by taking the actual capacity multiplied by the preset depth as a charge-discharge cutoff capacity, and perform charge-discharge cycle on the battery cell by taking the actual capacity of the battery cell calibrated after the previous charge-discharge cycle process multiplied by the preset depth as the charge-discharge cutoff capacity in the subsequent charge-discharge cycle process until the battery cell reaches the end-of-life state; the preset depth is the difference between the upper limit and the lower limit of the charging and discharging interval, the upper limit of the charging and discharging interval is a third preset percentage, the lower limit of the charging and discharging interval is a fourth preset percentage, the third preset percentage and the fourth preset percentage are both greater than or equal to 0 and smaller than 1, and the third preset percentage is greater than the fourth preset percentage. Illustratively, the third predetermined percentage is 60%, the fourth predetermined percentage is 20%, and the predetermined depth is 40%.
The shallow DOD cycle life testing device provided by this embodiment, the battery core calibration module calibrates the actual capacity and the direct current resistance of the battery core in a constant-current constant-voltage charging and discharging mode, the charging and discharging cycle module performs the charging and discharging cycle by taking the actual capacity of the battery core multiplied by the preset depth as a cut-off condition, the actual capacity and the direct current resistance of the battery core are recalibrated after every 50 times of power supply cycle retransmission, and the cut-off condition of the charging and discharging cycle is used as the cut-off condition of the charging and discharging cycle thereafter, until the battery core reaches a service life end state, the service life of the battery core is tested, more accurate test results and easier.
With continued reference to fig. 5, optionally, the cell calibration module 501 includes: a capacity calibration unit 503 and a direct current resistance calibration unit 504; the capacity calibration unit 503 is configured to calibrate the actual capacity of the battery cell; the dc resistance calibration unit 504 is configured to calibrate an actual dc resistance of the battery cell.
The method and the device for testing the shallow DOD cycle life provided by this embodiment calibrate the actual capacity and the direct current resistance of the battery cell in a constant-current constant-voltage charging and discharging manner, perform charging and discharging cycles with the actual capacity of the battery cell multiplied by a preset depth as a cut-off condition after the calibration, recalibrate the actual capacity and the direct current resistance of the battery cell after each 50 times of power supply cycles, and use the recalibration as the cut-off condition of the charging and discharging cycles thereafter until the battery cell reaches a life end state, the actual capacity as the cut-off condition in the testing process is continuously updated along with the change of the health degree of the battery, thereby realizing the test of the life of the battery cell, and achieving the effects of more accurate testing result and easier test realization.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A method for testing the cycle life of shallow DOD is characterized by comprising the following steps:
calibrating the actual capacity and the actual direct current resistance of the battery cell;
taking the actual capacity multiplied by the preset depth as a charge-discharge cut-off capacity, and carrying out charge-discharge circulation on the battery cell;
after charge and discharge circulation, calibrating the actual capacity and the actual direct current resistance of the battery cell again;
and multiplying the actual capacity of the battery cell calibrated after the previous charge-discharge cycle process by a preset depth to be used as a charge-discharge cutoff capacity in the subsequent charge-discharge cycle process, and performing charge-discharge cycle on the battery cell until the battery cell reaches a service life ending state, wherein the preset depth is the difference between the upper limit and the lower limit of a charge-discharge interval.
2. The method for testing shallow DOD cycle life of claim 1, wherein said charge and discharge cycle is charged and discharged in a constant current and voltage mode.
3. The method of testing shallow DOD cycle life of claim 1, wherein calibrating the actual capacity and the actual dc resistance of the cell comprises:
performing first constant current charging on the battery cell until the battery cell reaches a first working upper limit voltage;
carrying out first constant voltage charging on the battery cell until the charging current is close to 0A and the error is not more than 0.1;
performing first standing treatment on the battery cell;
performing first constant current discharge on the battery cell until the battery cell reaches a first working lower limit voltage;
performing first standing treatment on the battery cell;
and repeating the steps, wherein the electric quantity discharged by the secondary discharge is the actual capacity of the battery cell.
4. The method of testing shallow DOD cycle life of claim 3, wherein calibrating said actual dc resistance and said actual dc resistance of said cell comprises:
under the condition of full capacity of the battery cell, performing first constant current discharge on the battery cell until the electric quantity of the battery cell reaches 1/2 of the actual capacity;
performing second standing treatment on the battery cell;
measuring the voltage at two ends of the battery cell and recording the voltage as a first voltage value U1；
Applying a first current value I to the battery cell1Discharging for a first preset time period;
measuring the voltage at two ends of the battery cell and recording the voltage as a second voltage value U2；
The actual dc resistance value DCIR of the cell is (U)1-U2)/I1。
5. The method for testing shallow DOD cycle life of claim 1, wherein said charge and discharge cycles are cycled an integer number greater than 0.
6. A method of testing shallow DOD cycle life as recited in claim 1, wherein said end-of-life condition comprises: the actual capacity is lower than the product of a first preset percentage and the initial actual capacity or/and the actual direct current resistance is higher than the product of a second preset percentage and the initial actual direct current resistance, the initial actual capacity and the initial actual direct current resistance are the actual capacity and the actual direct current resistance calibrated for the first time, and the first preset percentage and the second preset percentage are both larger than or equal to 0 and smaller than 1.
7. The method for testing the shallow DOD cycle life of claim 1, wherein the upper limit of the charge-discharge interval is a third predetermined percentage, the lower limit of the charge-discharge interval is a fourth predetermined percentage, both the third predetermined percentage and the fourth predetermined percentage are greater than or equal to 0 and less than 1, and the third predetermined percentage is greater than the fourth predetermined percentage.
8. A test method of shallow DOD cycle life according to claim 4, wherein the time of said first resting treatment is less than or equal to the time of said second resting treatment.
9. A shallow DOD cycle life testing apparatus for carrying out the method of claims 1-6, the apparatus comprising:
the battery cell calibration module is used for calibrating the actual capacity and the actual direct current resistance of the battery cell and re-calibrating the actual capacity and the actual direct current resistance of the battery cell after charge-discharge circulation;
the charge-discharge circulation module is used for performing charge-discharge circulation on the battery cell by taking the actual capacity multiplied by the preset depth as a charge-discharge cutoff capacity, taking the actual capacity of the battery cell calibrated after the previous charge-discharge circulation process multiplied by the preset depth as the charge-discharge cutoff capacity in the next charge-discharge circulation process, and performing charge-discharge circulation on the battery cell until the battery cell reaches the end-of-life state; wherein, the preset depth is the difference between the upper limit and the lower limit of the charge-discharge interval.
10. The shallow DOD cycle life apparatus of claim 9, wherein said cell calibration module comprises: the device comprises a capacity calibration unit and a direct current resistance calibration unit; the capacity calibration unit is used for calibrating the actual capacity of the battery cell; the direct current resistance calibration unit is used for calibrating the actual direct current resistance of the battery cell.
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