CN111123109A

CN111123109A - Method and device for testing peak current of power battery

Info

Publication number: CN111123109A
Application number: CN201911235761.4A
Authority: CN
Inventors: 夏骥; 夏大兴; 李飞
Original assignee: Evergrande New Energy Vehicle Technology Guangdong Co Ltd
Current assignee: Hengda Hengchi New Energy Automobile Technology Guangdong Co ltd
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2020-05-08

Abstract

The embodiment of the invention provides a method and a device for testing the peak current of a power battery, wherein the method comprises the following steps: acquiring test parameters of a power battery to be tested; wherein the test parameters include at least one of: environmental parameters and residual electric quantity SOC; determining candidate test points according to the value interval of each test parameter, wherein the values of the test parameters of each candidate test point are not completely the same; determining a selected test point from the candidate test points; respectively testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point; and determining the peak current corresponding to all candidate test points of the power battery to be tested by utilizing the peak current corresponding to the selected test point.

Description

Method and device for testing peak current of power battery

Technical Field

The invention relates to the technical field of batteries, in particular to a method and a device for testing peak current of a power battery.

Background

In recent years, the field of new energy automobiles is added continuously by well-known enterprises at home and abroad, and the new energy automobiles become an important development direction of economic growth in China. With the development of new energy automobile industry, the performance requirements on power batteries are higher and higher, and other performances except energy density are paid extensive attention. Therefore, the main parameters of wide attention in the field of power batteries of the existing new energy automobiles are respectively as follows: SOC (State Of Charge).

In the related art, although some peak current testing methods for power batteries exist, the requirements of efficient and accurate testing cannot be met.

Disclosure of Invention

The embodiment of the invention provides a method and a device for testing the peak current of a power battery, which are used for solving at least one of a plurality of problems in the process of testing the power battery in the related art. The technical scheme is as follows:

in one aspect, a method for testing a peak current of a power battery is provided, and the method includes:

acquiring test parameters of a power battery to be tested; wherein the test parameters include at least one of: environmental parameters and residual electric quantity SOC;

determining candidate test points according to the value interval of each test parameter, wherein the values of the test parameters of each candidate test point are not completely the same; determining a selected test point from the candidate test points;

respectively testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point;

and determining the peak current corresponding to all candidate test points of the power battery to be tested by utilizing the peak current corresponding to the selected test point.

In some embodiments, the determining peak currents corresponding to all selected test points of the power battery to be tested by using the peak currents corresponding to the selected test points includes:

and performing linear interpolation and/or exponential fitting according to the obtained peak currents under the test parameters of all the selected test points to obtain the peak currents under the test parameters of all the candidate test points.

In some embodiments, the performing linear interpolation and/or exponential fitting according to the obtained peak currents under the test parameters of all the selected test points to obtain the test results of all the candidate test points includes:

acquiring the peak current of the power battery to be tested under the test parameters of each selected test point in the candidate test points;

when the test parameters are environmental parameters, performing exponential fitting on the peak current of each selected test point under the environmental parameters to obtain the corresponding relation between the environmental parameters and the peak current;

when the test parameter is SOC, fitting the peak current of the SOC of the selected test point by a linear interpolation method to obtain the corresponding relation between the SOC and the peak current;

and obtaining the test results of all candidate test points according to the corresponding relation between the environmental parameters and the peak current and/or the corresponding relation between the SOC and the peak current.

In some embodiments, the separately testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point includes:

determining the charge cut-off voltage of the power battery to be tested;

aiming at the test parameters of each selected test point, charging the power battery to be tested by using the constant working current corresponding to the test parameters of each selected test point so as to determine the cut-off voltage of the power battery to be tested in the charging process;

if the cut-off voltage reaches the charging cut-off voltage, determining the current constant working current value as the peak current of the selected test point;

and if the cut-off voltage does not reach the charging cut-off voltage, determining the current larger than the current constant working current from the testing parameters as the regulated constant working current to charge the testing power battery, and determining the charging constant working current when the testing power battery reaches the charging cut-off voltage as the peak current of the selected testing point until the testing power battery reaches the cut-off voltage in the charging process.

determining the discharge cut-off voltage of the power battery to be tested;

aiming at the test parameters of each selected test point, charging the power battery to be tested by using the constant working current corresponding to the test parameters of each selected test point so as to determine the cut-off voltage of the power battery to be tested in the discharging process;

if the cut-off voltage reaches the discharge cut-off voltage, determining the current constant working current value as the peak current of the selected test point;

and if the cut-off voltage does not reach the discharge cut-off voltage, determining the current larger than the current constant working current from the test parameters as the regulated constant working current to discharge for the test power battery until the power battery to be tested reaches the discharge cut-off voltage in the discharge process, and determining the discharge constant working current when the power battery to be tested reaches the cut-off voltage as the peak current of the selected test point.

In some embodiments, the charge cutoff voltage is the nominal charge cutoff voltage-a first preset protection voltage value, and the discharge cutoff voltage is the nominal discharge cutoff voltage + a second preset protection voltage value.

determining initial constant working current and adjusting step length;

and testing the power battery to be tested by taking the initial constant working current as the constant working current, if the cut-off voltage in the testing process does not reach the charging cut-off voltage and/or the discharging cut-off voltage, increasing the constant working current in the testing process of the power battery to be tested by taking the adjusting step length as an adjusting value until the cut-off voltage is reached in the charging and/or discharging process, and determining the charging and/or discharging constant working current when the power battery to be tested reaches the cut-off voltage as the peak current of the selected testing point.

In some embodiments, the environmental parameter is temperature; and the test parameters are: temperature and SOC.

In some embodiments, the determining a candidate test point according to the value interval of each test parameter includes:

determining a temperature value interval and an SOC value interval;

determining N temperature test points from the temperature value interval, and determining M SOC test points from the SOC value space; and generating M multiplied by N candidate test points, wherein the temperature and/or SOC value of each candidate test point is different.

In another aspect, a device for testing a peak current of a power battery is provided, which includes:

the test parameter acquisition module is used for acquiring test parameters of the power battery to be tested; wherein the test parameters include at least one of: environmental parameters and residual electric quantity SOC;

the sampling point acquisition module is used for determining candidate test points according to the value intervals of each test parameter, wherein the values of the test parameters of each candidate test point are not completely the same; determining a selected test point from the candidate test points;

the peak current determining module is used for respectively testing the power battery to be tested according to the testing parameters corresponding to each selected testing point so as to obtain the peak current of the power battery to be tested under the testing parameters corresponding to each selected testing point;

and the fitting module is used for determining the peak currents corresponding to all candidate test points of the power battery to be tested by utilizing the peak currents corresponding to the selected test points.

In some embodiments, the fitting module is to perform the following operations:

In some embodiments, the sample point acquisition module is configured to:

determining the charge cut-off voltage of the power battery to be tested;

In some embodiments, the sample point acquisition module is configured to:

determining the discharge cut-off voltage of the power battery to be tested;

In some embodiments, the peak current determination module is to:

determining initial constant working current and adjusting step length;

determining a temperature value interval and an SOC value interval;

The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:

according to the various embodiments, the sampling point is selected as the selected test point according to the test parameters of the candidate test point, so that only part of the candidate test points are required to be tested, and the test efficiency is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a working process of testing a power battery to be tested by using a random electricity testing method;

FIG. 2 is a schematic workflow diagram of a method for testing the peak current of a power cell using the JEVS Power test method;

FIG. 3 is a schematic workflow diagram of a method for testing the peak current of a power cell using the HPPC method;

FIG. 4 is a schematic workflow diagram of a method for testing peak current of a power cell according to an embodiment of the present invention;

FIG. 5 is a schematic workflow diagram of another method of testing peak current of a power cell in accordance with an embodiment of the present invention;

FIG. 6 is a schematic workflow diagram of another method for testing peak current of a power cell in accordance with an embodiment of the present invention;

fig. 7 is a schematic structural diagram of another apparatus for testing peak current of a power battery according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a working flow of a stochastic electrical measurement method; it includes:

step 101, obtaining test parameters of a power battery to be tested, wherein the test parameters include at least one of the following: a preset temperature, a preset SOC (state of charge), a preset test time;

102, testing the battery to be tested by using a preset constant working current n under the current test parameters;

103, judging whether the voltage of the power battery to be tested reaches a cut-off voltage; if yes, jumping to step 104; if not, increasing the constant current n, and returning to the step 102;

104, recording the current value of the power battery to be tested to be used as the peak current in the current testing environment;

and 105, changing the test parameters of the power battery to be tested in a mode of increasing the current value, and returning to the step 101.

According to the method, the random electricity testing method is to continuously change the test parameters, then detect the power battery to be tested under each test parameter, and acquire the peak current corresponding to the cut-off voltage under the current test parameter in an incremental current mode.

FIG. 2 is a schematic diagram of a method for measuring peak current of a power battery by a JEVS power test method; it includes:

step 201, obtaining test parameters of a power battery to be tested, wherein the test parameters include at least one of the following: a preset temperature, a preset SOC (state of charge), a preset test time;

step 202, under the current test parameters, respectively testing the battery to be tested by using different constant working currents so as to record the cut-off voltage of the power battery to be tested when charging and discharging are carried out within a preset time m under each constant current;

step 203, fitting the relation between the charge-discharge current and the cut-off voltage linearly by using the cut-off voltages corresponding to the different constant working currents obtained in step 202, and calculating the peak current value under the rated cut-off voltage;

and step 204, changing the test parameters of the power battery to be tested, and returning to the step 201.

Specifically, in step 202, the JEVS method sequentially charges and discharges the power battery to be tested at each constant working current to obtain data of alternate charging and discharging of the battery at the constant working current, and obtains a peak current by fitting a voltage-current relationship.

In the above method, the different constant operating currents may be: 0.1C, 0.5C, 1C, 1.5C, 2C … …. Therefore, the constant working current can be changed continuously, and the power battery to be tested is charged and discharged under each constant working current, so that the relation between the voltage and the current is fitted to obtain the peak current of the power battery to be tested.

FIG. 3 is a schematic workflow diagram of a method for testing the peak current of a power cell using a hybrid pulse capability characteristic test (HPPC) method; it includes:

301, obtaining test parameters of a power battery to be tested, wherein the test parameters include at least one of the following: a preset temperature, a preset SOC (state of charge), a preset test time;

step 302, under the current test parameters, respectively testing the battery to be tested by using different constant working currents so as to record the cut-off voltage of the power battery to be tested when charging and discharging are carried out within a preset time m under each constant current;

step 303, calculating the direct current impedance of the battery by using the relationship between the voltage and the current obtained in the step 302, and calculating the peak current of each constant working current through the direct current impedance, the rated cut-off voltage and the OCV;

and 304, changing the test parameters of the power battery to be tested, and returning to the step 301.

According to the method, the hybrid power pulse capability characteristic test (HPPC) method comprises the steps of conducting 0.75I/1I constant current charging and discharging on the battery under different charge states and temperatures, calculating the internal resistance of the battery under the temperature and charge states through voltage and current, and calculating the peak current through charging and discharging internal resistance.

As can be seen from fig. 1 to 3, there are advantages in the related art:

(1) random electricity measuring method: and (3) randomly and empirically selecting the constant current discharging/charging of the test current to the cut-off voltage under the specific temperature and the specific charge state, and recording the discharging/charging duration time. The method can directly test the peak current of specific temperature, charge state and duration, but the test is quite complicated, and the test efficiency is extremely low due to repeated random test;

(2) hybrid power pulse capability characteristic test (HPPC): the method comprises the steps of carrying out 0.75I/1I constant current charging and discharging on a battery under different charge states and temperatures, calculating internal resistance of the battery under the temperature and charge states through voltage and current, and calculating peak current through the internal resistance of charging and discharging, wherein the method adopts single pulse current to calculate the peak current to be large, and the use has safety risk;

(3) JEVS power test method: selecting different currents, alternately charging and discharging the battery in a certain charge state, and fitting the relation between voltage and current to obtain peak current. However, this test method is less suitable for the case where the peak discharge current is much larger than the peak charge current in the high state of charge.

In the related art, a method for rapidly testing the peak power of the lithium ion battery is provided, the Japanese JEVS power test is changed, test verification is added under a high charge state, and the linear fitting accuracy is optimized. There is also a method for testing the peak current/power of a battery in the related art, and both methods are improved methods of a random current testing method.

However, these existing methods are all to test the power battery under a single temperature and a single charge state, and the rated cut-off voltage is adopted for charging and discharging. The existing method mainly has the problems that: (1) the accurate full-peak current spectrum can be obtained only by a large number of tests under different temperatures and different SOC conditions; (2) the rated cut-off voltage is used as a test condition, the inconsistency of the single battery cell is not considered, and the peak current has risks in the whole package using stage.

As can be seen from the above description, although there are some methods for testing the peak current of the power battery in the related art, these methods have drawbacks; the embodiment of the invention provides a method and a device for testing the peak current of a power battery, which are used for solving at least one defect in the prior art so as to improve the testing efficiency and/or reliability.

As shown in fig. 4, an embodiment of the present invention provides a method for testing a peak current of a power battery, including:

step 401, obtaining test parameters of a power battery to be tested; wherein the test parameters include at least one of: environmental parameters and residual electric quantity SOC;

step 402, determining candidate test points according to the value intervals of each test parameter, wherein the values of the test parameters of each candidate test point are not completely the same; determining a selected test point from the candidate test points;

step 403, testing the power battery to be tested according to the test parameters corresponding to each selected test point, so as to obtain peak current of the power battery to be tested under the test parameters corresponding to each selected test point;

and step 404, determining peak currents corresponding to all candidate test points of the power battery to be tested by using the peak currents corresponding to the selected test points.

The embodiment provides a method for testing the peak current of the power battery, and the sampling point is selected as the selected test point according to the test parameters of the candidate test point, so that only part of the candidate test points are required to be tested, and the test efficiency is improved.

In one embodiment of the invention, the environmental parameter is temperature. As shown in fig. 5, the method includes:

501, obtaining test parameters of a power battery to be tested; wherein the test parameters include: temperature, remaining capacity SOC;

step 502, determining candidate test points according to the value interval of each test parameter, wherein the values of the test parameters of each candidate test point are not completely the same; determining a selected test point from the candidate test points;

step 503, testing the power battery to be tested according to the test parameters corresponding to each selected test point, so as to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point;

and step 504, determining the peak current corresponding to all candidate test points of the power battery to be tested by utilizing the peak current corresponding to the selected test point.

The embodiment provides a method for testing the peak current of the power battery, and the sampling points are selected from the test parameters of the candidate test points to serve as the selected test points, so that the test can be finally carried out only by testing part of the sampling points, and the test efficiency is improved.

For example, the test may be performed at a temperature of-30 ℃ to +55 ℃ and at an interval of 100% to 5% from the SOC. The test points during the test can be determined at intervals of 5 ℃, and the test points of the SOC can be determined at intervals of 5 percentage points, so that the charging/discharging test can be performed on the power battery to be tested under each temperature test point and each SOC test point, and the peak current can be determined according to the cut-off voltage. That is, the candidate test points for temperature are, as shown in Table 1, at-30 ℃, -25 ℃, -20 ℃, -15 ℃, -10 ℃, -5 ℃, 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, respectively; and candidate test points for SOC are 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%. Because the number of the test parameters is two, and each test parameter has a test point in the value range, the final candidate test point is 18 × 12 candidate test points as shown in table 1; namely 18 temperature test points and 12 SOC test points.

Specifically, table 1 may be referred to; all of the test points labeled T in table 1 are selected test points selected from the candidate test points.

TABLE 1

In an embodiment of the present invention, the determining peak currents corresponding to all selected test points of the power battery to be tested by using the peak currents corresponding to the selected test points includes:

In some embodiments, the peak current of the power battery to be tested at the selected test point can be obtained by:

determining the charge cut-off voltage of the power battery to be tested;

determining the discharge cut-off voltage of the power battery to be tested;

Of course, in each test, only the power battery to be tested may be subjected to the charge test or the discharge test, or the charge test may be performed first and then the discharge test may be performed, or the discharge test may be performed first and then the charge test may be performed, or the charge test and the discharge test may be performed alternately.

In one embodiment of the present invention, as shown in fig. 6, the method includes:

601, obtaining test parameters of a power battery to be tested; wherein the test parameters include: environmental parameters and residual electric quantity SOC;

step 602, determining candidate test points according to the value intervals of each test parameter, wherein the test parameters of each candidate test point are not identical in value; determining a selected test point from the candidate test points;

step 603, determining the charge cut-off voltage of the power battery to be tested; aiming at the test parameters of each selected test point, charging the power battery to be tested by using the constant working current corresponding to the test parameters of each selected test point so as to determine the cut-off voltage of the power battery to be tested in the charging process; if the cut-off voltage reaches the charging cut-off voltage, determining the current constant working current value as the peak current of the selected test point; if the cut-off voltage does not reach the charging cut-off voltage, determining the current larger than the current constant working current from the testing parameters as the regulated constant working current to charge the testing power battery, and determining the charging constant working current when the testing power battery reaches the charging cut-off voltage as the peak current of the selected testing point until the testing power battery reaches the cut-off voltage in the charging process;

or

Determining the discharge cut-off voltage of the power battery to be tested; aiming at the test parameters of each selected test point, charging the power battery to be tested by using the constant working current corresponding to the test parameters of each selected test point so as to determine the cut-off voltage of the power battery to be tested in the discharging process; if the cut-off voltage reaches the discharge cut-off voltage, determining the current constant working current value as the peak current of the selected test point; if the cut-off voltage does not reach the discharge cut-off voltage, determining the current larger than the current constant working current from the test parameters as the regulated constant working current to discharge for the test power battery until the power battery to be tested reaches the discharge cut-off voltage in the discharge process, and determining the discharge constant working current when the power battery to be tested reaches the cut-off voltage as the peak current of the selected test point;

and step 604, determining the peak current corresponding to all candidate test points of the power battery to be tested by using the peak current corresponding to the selected test point.

Those skilled in the art will understand that the environmental parameter, SOC (remaining power) in the present embodiment may be consistent with the parameters in the foregoing steps 501 and 505, that is, the environmental parameter may be temperature; please refer to step 501-505 for details, which are not described herein.

The embodiment provides a method for testing the peak current of the power battery, the sampling point is selected as the selected test point according to the test parameters of the candidate test point, and thus the test parameters of the selected test point are only required to be tested, and the test efficiency is improved.

In one embodiment of the invention, the power battery to be tested can be discharged within a first preset test time under the current constant working current, and then the power battery is stood for a first discharge and then for a first standing time; then charging the power battery to be tested within a second preset test time, and then standing for a first charging and standing time; the cut-off voltage during charging and discharging was tested. In a specific example, the initial constant working current is 0.5C, the first discharge-to-rest time is 30 minutes, the first charge-to-rest time is 30 minutes, the first preset test time is 10 seconds, and the second preset test time is 10 seconds; this step 603 may specifically be: discharging at 0.5C constant working current for 10 s, and standing for 30 min; charging is carried out for 10 seconds at a constant working current of 0.5C, then standing is carried out for 30 minutes, and the cut-off voltage of the battery is recorded. Of course, in the above example, the charging and discharging processes may be exchanged, and the sequence of the charging and discharging processes may be determined according to the SOC of the battery, that is, when the SOC of the battery is higher and charging is not allowed, the discharging process must be performed first, and then the charging process must be performed; if the SOC of the battery is low and discharging is not allowed, the charging process must be performed first and then the discharging process must be performed.

In another embodiment of the present invention, in order to avoid the overshoot or the over-discharge, the charge cut-off voltage and the discharge cut-off voltage are obtained according to the rated charge cut-off voltage and the rated discharge cut-off voltage in step 603. Namely: the charge cutoff voltage is the rated charge cutoff voltage-a first preset protection voltage value, and the discharge cutoff voltage is the rated discharge cutoff voltage + a second preset protection voltage value.

For example: when the rated charge cut-off voltage was 4.2V and the rated discharge cut-off voltage was 2.8V, the test charge cut-off voltage was 4.18V and the test discharge cut-off voltage was 2.95V. That is, the charge cutoff voltage is equal to the rated charge cutoff voltage — the first preset protection voltage value, and the discharge cutoff voltage is equal to the rated discharge cutoff voltage + the second preset protection voltage value. In this embodiment, the first predetermined protection voltage is 10 mV-500 mV, and the second predetermined protection voltage is 10 mV-500 mV. By adopting the first preset protection voltage value and the second preset protection voltage value, the problem of overcharge and overdischarge of the battery cell in the whole package test and use process can be effectively avoided. The first preset protection voltage value may be equal to the second preset protection voltage value, or the first preset protection voltage value may not be equal to the second preset protection voltage value. In the above embodiments, it can be seen that the first preset protection voltage value of the above embodiments is 4.2V-4.18V-20 mV, and the second preset protection voltage value is 2.95V-2.8V-150 mV.

In one embodiment of the present invention, the charge cut-off voltage for the test is 4.18V and the discharge cut-off voltage is 2.95V; of course, these values are only examples for illustrating the technical solutions of the embodiments of the present invention. And acquiring the cut-off voltage of the power battery to be detected, which is obtained in the test of the step 605, judging whether the cut-off voltage of the power battery to be detected reaches 4.18V or 2.95V, and if so, stopping the test if the current constant working current reaches the peak current. If the cut-off voltage of the power battery to be detected does not reach 4.18V or 2.95V, the current constant working current needs to be adjusted, and the adjustment step length can be the adjustment step length of the constant working current; and then returns to step 603 to perform the test again.

Taking the initial constant working current as 0.5C and the constant working current adjustment step length as 0.5C as examples, when the test is performed for the first time, the test is performed with the initial constant working current; if it is determined after the test in step 603 that the cut-off voltage does not reach 4.18V or 2.95V when the initial constant operating current is used for the test charging/discharging, the step 603 is executed again after the constant operating current of the test is adjusted. That is: the current constant working current is equal to the current constant working current plus the constant working current adjusting step length of 0.5C; i.e., each time the present constant operating current is adjusted in steps of 0.5C, then it jumps to step 603 and tests again until the cutoff voltage determined in step 604 reaches the charge cutoff voltage or the discharge cutoff voltage.

In one embodiment of the present invention, the test may be performed from the first selected test point in table 1 until each selected test point is tested.

In an embodiment of the present invention, the peak current of each selected test point can be determined through the foregoing steps 601-603; the complete temperature/SOC map may then be calculated by a preset algorithm in step 604. I.e., after determining the peak current for each selected test point through step 603, step 604 includes:

and performing linear interpolation and/or Exponential fitting (explicit Fit) according to the obtained test results of all the selected test points to obtain the test results of all the candidate test points.

Specifically, the step 604 may include:

step A, obtaining a test result of the power battery to be tested under the environmental parameters of a selected test point in the candidate test points;

step B, performing exponential fitting on the test results of the selected test points to obtain the corresponding relation between the temperature and the peak current, and obtaining the test results of all other candidate test points which are marked as C1 and have the same SOC with the selected test points and shown in the table 2;

TABLE 2

Step C, fitting the test results of the selected test points by a linear interpolation method to obtain the corresponding relation between the SOC and the peak current, and obtaining the test results of all other candidate test points which are marked as C2 and have the same temperature with the selected test points and shown in the table 3;

TABLE 3

After the step B and the step C, obtaining peak current of full temperature and full SOC ranges by other test points except the selected test point in the candidate test points through exponential fitting and linear interpolation fitting; compared with the prior art, the test scheme can improve the efficiency of testing the power battery to be tested.

In an embodiment of the present invention, the order of step B and step C may be exchanged, i.e.: the correspondence between the SOC and the peak current (i.e., the candidate test point identified as C2 in table 3) is obtained by linear interpolation, and then the correspondence between the temperature and the peak current (i.e., the candidate test point identified as C1 in table 3) is obtained by exponential fitting.

Of course, it will be understood by those skilled in the art that in any embodiment of the present invention, only the results of the test may be exponentially fitted to obtain the temperature versus peak current correspondence (i.e., the candidate test point identified as C1 in Table 3). In any embodiment of the present invention, only linear interpolation fitting may be performed on the test results to obtain the correspondence between the SOC and the peak current (i.e., the candidate test point identified as C2 in table 3). That is, in any embodiment of the present invention, only step B may be executed, only step C may be executed, and step B and step C may be executed in any order.

One embodiment of the present invention provides a device for testing peak current of a power battery, as shown in fig. 7, including:

In some embodiments, the fitting module is to perform the following operations:

In some embodiments, the sample point acquisition module is configured to:

determining the charge cut-off voltage of the power battery to be tested;

In some embodiments, the sample point acquisition module is configured to:

determining the discharge cut-off voltage of the power battery to be tested;

In some embodiments, the peak current determination module is to:

determining initial constant working current and adjusting step length;

determining a temperature value interval and an SOC value interval;

In the embodiment of the present invention, the process executed by the testing apparatus may be the same as the method in any of the previous embodiments, and therefore, the description thereof is omitted here.

The following describes an embodiment of the present invention with a specific example. Of course, it will be understood by those skilled in the art that this example is only one specific example presented for ease of understanding, and is not intended to limit the scope of the claims of the present invention in any way.

Step 1001, preprocessing a power battery to be tested;

in the embodiment of the invention, the power battery to be tested with the capacity of 50Ah, the rated charge cut-off voltage of 4.2V and the rated discharge cut-off voltage of 2.8V is taken as an example.

Some power cells to be tested may require pre-charging and pre-discharging processes, so in one embodiment of the invention, the power cells to be tested may first be pre-processed before being tested. For example, according to the standard work flow of the power battery to be tested, the power battery to be tested is subjected to standard charge and discharge cycles firstly. Many existing power batteries to be tested are given a standard number of charge and discharge cycles, for example 5 times, in the workbook. Of course, step 1001 is not a necessary step of embodiments of the present invention, but an optional step.

In one embodiment of the present invention, the power battery to be tested may be charged before the test to prepare for the test. For example: the environment temperature can be set to be 25 ℃, the initial standing time is 6 hours, and the initial constant working current is 1C current (namely 50A); the method may then comprise: the battery is placed in an environment incubator at 25 ℃ and is kept still for not less than 6 hours, the SOC of the battery is adjusted to 95 percent by constant current discharge of 1C current (50A), and then the battery is kept still for 1 hour.

Step 1002, determining test parameters of a power battery to be tested; determining candidate test points to be tested according to the value intervals of the test parameters, wherein the test parameters corresponding to each candidate test point are not identical; then selecting sampling points from the candidate test points as selected test points; wherein the test parameters include at least one of: environmental parameters, SOC;

in one embodiment of the present invention, the environmental parameter may be a temperature of the power cell to be tested. Of course, this is merely an example, and the environmental parameter may also include one of the following: humidity and air pressure values … …. In the following examples, the temperature and SOC are exemplified. In the embodiment of the invention, the fact that the test parameters corresponding to each candidate test point are not identical means that when the test parameter is one parameter, two different candidate test points have different test parameters; when the test parameter is two or more than two parameters, then there is at least one different test parameter between two different candidate test points.

In one embodiment of the present invention, in order to test the peak current of the power battery to be tested at different temperatures, the power battery to be tested needs to be subjected to charge/discharge tests at different temperatures, so as to determine the cut-off voltages of the power battery to be tested at different temperatures. Meanwhile, in order to determine the performance of the power battery to be tested under different residual capacities SOC, the power battery to be tested needs to be subjected to charge/discharge tests under different residual capacities SOC.

For example, the test may be performed at-30 ℃ to +55 ℃ and the SOC may be measured in the range of 100% to 5%. The test points during the test can be determined at intervals of 5 ℃, and the test points of the SOC can be determined at intervals of 5 percentage points, so that the charging/discharging test can be performed on the power battery to be tested under each temperature test point and each SOC test point, and the peak current can be determined according to the cut-off voltage. Specifically, table 1 may be referred to; all possible candidate test points are listed in table 1, and all points marked T are selected test points selected as sample points from the candidate test points.

TABLE 1

In the embodiment of the invention, in order to improve the testing efficiency, a plurality of selected testing points are determined and preset instead of testing all the candidate testing points one by one, and only the selected testing points are tested.

For example, as shown in table 1, 18 candidate test points are first determined at 5 ℃ intervals between-30 ℃ and +55 ℃, and 12 candidate test points are determined at 5 percentile intervals between an SOC of 100% and 5 ℃; therefore, if the power battery to be tested is tested one by one, the power battery to be tested needs to be tested at 18 multiplied by 12 candidate test points with different environmental parameters respectively; it can be seen from table 1 that each candidate test point has different operating parameters; that is, the ambient temperature and/or SOC of each candidate test point.

In order to improve the testing efficiency, only a part of the candidate test points in all the different candidate test points are tested in the embodiment of the invention. That is, as shown in table 1, only the candidate test points in which part is identified as T are used as the selected test points; and testing the selected test points one by one in subsequent steps.

Step 1003, determining the charge cut-off voltage and the discharge cut-off voltage of the power battery to be tested;

in one embodiment of the present invention, the rated charge cut-off voltage and the rated discharge cut-off voltage can be determined by the calibration parameters of the power battery to be tested, or by any other possible means.

In another embodiment of the invention, the charge cut-off voltage and the discharge cut-off voltage of the power battery to be tested can just adopt the standard rated charge cut-off voltage and rated discharge cut-off voltage of the power battery to be tested.

In another embodiment of the present invention, in order to avoid the overshoot or the overdischarge, the rated charge cut-off voltage and the rated discharge cut-off voltage for the test are obtained according to the rated charge cut-off voltage and the rated discharge cut-off voltage. For example: when the rated charge cut-off voltage was 4.2V and the rated discharge cut-off voltage was 2.8V, the test charge cut-off voltage was 4.18V and the test discharge cut-off voltage was 2.95V. That is, the charge cutoff voltage is equal to the rated charge cutoff voltage — the first preset protection voltage value, and the discharge cutoff voltage is equal to the rated discharge cutoff voltage + the second preset protection voltage value. In this embodiment, the first predetermined protection voltage is 10 mV-500 mV, and the second predetermined protection voltage is 10 mV-500 mV. By adopting the first preset protection voltage value and the second preset protection voltage value, the problem of overcharge and overdischarge of the battery cell in the whole package test and use process can be effectively avoided. The first preset protection voltage value may be equal to the second preset protection voltage value, or the first preset protection voltage value may not be equal to the second preset protection voltage value. In the above embodiments, it can be seen that the first preset protection voltage value of the above embodiments is 4.2V-4.18V-20 mV, and the second preset protection voltage value is 2.95V-2.8V-150 mV.

Step 1004, obtaining test parameters of the power battery to be tested;

that is, the current test parameters are determined based on the ambient temperature and/or SOC of the selected test points of Table 1.

Step 1005, under the current test parameters, respectively testing the battery to be tested by using different constant working currents so as to record the cut-off voltage of the power battery to be tested when charging and/or discharging are carried out within a preset time m under each constant current;

in one embodiment of the invention, the power battery to be tested can be discharged within a first preset test time under the current constant working current, and then the power battery is stood for a first discharge and then for a first standing time; then charging the power battery to be tested within a second preset test time, and then standing for a first discharge and standing time; the cut-off voltage during charging and discharging was tested. In a specific example, the initial constant working current is 0.5C, the first discharge-to-rest time is 30 minutes, the first preset test time is 10 seconds, and the second preset test time is 10 seconds; this step 1005 may specifically be: discharging at 0.5C constant working current for 10 s, and standing for 30 min; charging at 0.5C constant working current for 10 s, standing for 30 min, and recording the cut-off voltage of the battery. Of course, in the above example, the charging and discharging processes may be exchanged, and the sequence of the charging and discharging processes may be determined according to the SOC of the battery, that is, when the SOC of the battery is higher and charging is not allowed, the discharging process must be performed first, and then the charging process must be performed; if the SOC of the battery is low and discharging is not allowed, the charging process must be performed first and then the discharging process must be performed.

The first execution in step 1005 is then that the present constant operating current is the initial constant operating current, which may be obtained in step 1004. If step 1005 is not performed for the first time, the current constant operating current is equal to the initial constant operating current + the constant operating current adjustment step.

Step 1006, determining whether the cut-off voltage determined in step 1005 has reached a charge cut-off voltage or a discharge cut-off voltage; if yes, jumping to step 1007; if not, adjusting the constant working current, and returning to step 1005 for testing again;

in one embodiment of the present invention, the charge cut-off voltage for the test is 4.18V and the discharge cut-off voltage is 2.95V; of course, these values are only examples for illustrating the technical solutions of the embodiments of the present invention. Acquiring the cut-off voltage of the power battery to be tested, which is obtained in the test of the step 1005, judging whether the cut-off voltage of the power battery to be tested reaches 4.18V or 2.95V, if so, indicating that the current constant working current in the step 1005 reaches the peak current, and stopping the test. If the cut-off voltage of the power battery to be tested does not reach 4.18V or 2.95V, the current constant working current in step 1005 needs to be adjusted, and the adjustment step length can be a constant working current adjustment step length; and then returns to step 1005 to perform the test again.

Taking the initial constant operating current as 0.5C and the constant operating current adjustment step as 0.5C as an example, when step 1005 is executed for the first time, the test is performed with the constant operating current; and if step 1005 is performed again, the present constant operation current is equal to the present constant operation current + the constant operation current adjustment step size of 0.5C. That is, each time the present constant operating current is adjusted by a step of 0.5C, the process then jumps to step 1005 to perform the test again until whether the cutoff voltage determined in step 1005 reaches the charge cutoff voltage or the discharge cutoff voltage.

Step 1007, judging whether all the current selected test points are tested, if so, jumping to step 1008, and if not, jumping to step 1004 according to the test parameters of the next selected test point.

And step 1008, performing linear interpolation and/or Exponential fitting (explicit Fit) according to the obtained test results of all the selected test points to obtain the test results of all the candidate test points.

In an embodiment of the present invention, the test result obtained by testing the selected test point may be as shown in table 1, which includes a plurality of selected test points, and the selected test points may be selected from candidate test points, and the selected test points are non-continuous, that is, certain selected test points are spaced apart from each other between some selected test points as shown in table 1.

Wherein step 1008 comprises:

TABLE 2

TABLE 3

After the step B and the step C, obtaining peak current of full temperature and full SOC ranges by other test points except the selected test point in the candidate test points through exponential fitting and linear interpolation fitting; compared with the prior art, the test scheme can improve the efficiency of testing the power battery to be tested. In an embodiment of the present invention, the order of step B and step C may be exchanged, i.e.: the correspondence between the SOC and the peak current (i.e., the candidate test point identified as C2 in table 3) is obtained by linear interpolation, and then the correspondence between the temperature and the peak current (i.e., the candidate test point identified as C1 in table 3) is obtained by exponential fitting.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units may be merely a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for testing the peak current of a power battery is characterized by comprising the following steps:

2. The method for testing the peak current of the power battery according to claim 1, wherein the determining the peak currents corresponding to all the selected test points of the power battery to be tested by using the peak currents corresponding to the selected test points comprises:

3. The method for testing the peak current of the power battery according to claim 2, wherein the step of performing linear interpolation and/or exponential fitting according to the obtained peak currents under the test parameters of all the selected test points to obtain the test results of all the candidate test points comprises:

4. The method for testing the peak current of the power battery according to claim 1, wherein the step of respectively testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point comprises the following steps:

determining the charge cut-off voltage of the power battery to be tested;

5. The method for testing the peak current of the power battery according to claim 1, wherein the step of respectively testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point comprises the following steps:

determining the discharge cut-off voltage of the power battery to be tested;

6. The method for testing the peak current of the power battery according to claim 4, wherein the charge cut-off voltage is the rated charge cut-off voltage-a first preset protection voltage value, and the discharge cut-off voltage is the rated discharge cut-off voltage + a second preset protection voltage value.

7. The method for testing the peak current of the power battery according to claim 1, wherein the step of respectively testing the power battery to be tested according to the test parameters corresponding to each selected test point to obtain the peak current of the power battery to be tested under the test parameters corresponding to each selected test point comprises the following steps:

determining initial constant working current and adjusting step length;

8. The method for testing the peak current of the power battery according to any one of claims 1-7, wherein the environmental parameter is temperature; and the test parameters are: temperature and SOC.

9. The method for testing the peak current of the power battery according to claim 8, wherein the step of determining the candidate test points according to the value intervals of each test parameter comprises the following steps:

determining a temperature value interval and an SOC value interval;

10. A testing device for peak current of a power battery is characterized by comprising: