CN116626518A - Battery self-discharge detection method and system - Google Patents
Battery self-discharge detection method and system Download PDFInfo
- Publication number
- CN116626518A CN116626518A CN202310908010.4A CN202310908010A CN116626518A CN 116626518 A CN116626518 A CN 116626518A CN 202310908010 A CN202310908010 A CN 202310908010A CN 116626518 A CN116626518 A CN 116626518A
- Authority
- CN
- China
- Prior art keywords
- battery
- self
- ocv
- discharge
- circuit voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 25
- 230000003068 static effect Effects 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000012216 screening Methods 0.000 claims abstract description 7
- 238000007600 charging Methods 0.000 claims description 25
- 238000010277 constant-current charging Methods 0.000 claims description 18
- 230000010287 polarization Effects 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 11
- 230000003287 optical effect Effects 0.000 claims description 8
- 238000004364 calculation method Methods 0.000 claims description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 6
- 229910052744 lithium Inorganic materials 0.000 claims description 6
- 230000002950 deficient Effects 0.000 claims description 3
- 238000004590 computer program Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 230000006870 function Effects 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 230000032683 aging Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000013016 damping Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005562 fading Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000010606 normalization Methods 0.000 description 2
- 238000012797 qualification Methods 0.000 description 2
- 230000000284 resting effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 239000012792 core layer Substances 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application relates to a battery self-discharge detection method and a system, comprising the following steps: the method comprises the steps of obtaining an OCV-SOC curve of each battery, standing the batteries, respectively collecting open-circuit voltages of each battery after standing for a first time period and after standing for a second time period, wherein the second time period is larger than the first time period; calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range; calculating the difference between the open circuit voltage of each battery after standing for a first period of time and the open circuit voltage of each battery after standing for a second period of time, and recording the difference as a battery standing differential pressure value; and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery. The self-discharge consistency screening method can reduce errors of self-discharge consistency screening of the battery, improve detection precision and save detection time.
Description
Technical Field
The application relates to the technical field of battery detection, in particular to a battery self-discharge detection method and system.
Background
Aging of lithium batteries is a natural phenomenon during use. During aging, the consistency gradually worsens, and the consistency of each cell in the battery pack has a significant impact on overall performance. The self-discharge of a battery refers to a phenomenon in which the capacity of the battery spontaneously decreases after the battery is charged in an open state and left for a while, and is also referred to as the charge retention capacity of the battery under certain conditions. Batteries with high self-discharge rates typically result in rapid decay of capacity, resulting in failure of the battery. Since the open circuit voltage is directly related to the SOC or capacity of the battery, and the decrease in the open circuit voltage is the most intuitive representation of the self-discharge of the battery, the self-discharge rate can be analyzed by the decay of the open circuit voltage.
The conventional method for selecting the self-discharge consistency is to fully charge the battery, record the voltage value of the battery, store the battery for a period of time, then carry out open-circuit voltage test record, and take the difference value of the two open-circuit voltages as the basis for selecting the self-discharge. The method can not screen the battery with large self-discharge in a short time, and the situation that the self-discharge difference is small in a short time, but the self-discharge difference is large when the battery is kept stand for a long time, and meanwhile, the influence of polarization after the battery is charged is not considered, for example: patent CN103008261 a; there are also tests to adjust the state of charge of a battery to a discharged state, such as: patent CN 103293481A. Although the methods proposed in these patents all refer to the relationship between the self-discharge and the open circuit voltage difference, an understanding of the self-discharge and the open circuit voltage difference stays on the surface, and the resulting error is large. The reason is that no matter which state of charge the battery is to be regulated, the battery must be charged and discharged, that is, the battery is charged and discharged for many days at constant current and constant voltage by using a small current, and the voltage difference acquired after stopping contains not only self-discharge but also corrosion current caused by polarization. The so-called corrosion current can also be called internal self-balancing current, and the proportion of the corrosion current is large, so that errors exist on the basis of battery sorting related to the prior art, and the actual production needs cannot be met.
Disclosure of Invention
Therefore, the application aims to overcome the technical defects of long time spent on self-discharge detection of the seed battery and poor detection precision in the prior art.
In order to solve the technical problems, the application provides a battery self-discharge detection method, which comprises the following steps:
acquiring an OCV-SOC curve of each battery, wherein the OCV is open circuit voltage and the SOC is state of charge;
standing the batteries, and respectively collecting open-circuit voltages of each battery after the batteries are kept stand for a first time period and after the batteries are kept stand for a second time period, wherein the second time period is greater than the first time period;
calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range;
calculating the difference between the open circuit voltage of each battery after standing for a first period of time and the open circuit voltage of each battery after standing for a second period of time, and recording the difference as a battery standing differential pressure value;
and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
Preferably, the calculating the self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery includes:
open circuit voltage difference ΔOCV corresponding to a battery capacity decay of n% n%,i =△OCV SOC=m%,i -△OCV SOC=（m-n）%, i ;
Where i is the battery serial number, OCV SOC=m%,i Open circuit voltage at m% state of charge for battery i; OCV (optical clear video) SOC=（m-n）%,i Open circuit voltage at soc= (m-n)%; n is more than 0 and less than 100, m is more than 0 and less than or equal to 100, and n is more than m, m and n are natural numbers.
Preferably, the calculating to obtain the difference ratio of each battery according to the self-discharge rate threshold value of the battery and the static pressure difference value of the battery includes:
difference ratio M t1–t2,n%,i =△OCV t1-t2,i / △OCV n%,i ，
Wherein t1 is a first time period, t2 is a second time period, and i is a battery serial number;
△OCV t1-t2,i the difference between the open circuit voltage of the battery i after standing t1 and the open circuit voltage of the battery i after standing t 2;
△OCV n%,i the open circuit voltage difference value corresponding to the capacity attenuation n% of the battery i is more than 0 and less than 100, and n is a natural number.
Preferably, the calculating to obtain the difference ratio of each battery according to the self-discharge rate threshold value of the battery and the static pressure difference value of the battery further comprises:
and setting a qualified threshold value, and screening the batteries with the difference ratio larger than the qualified threshold value as defective products.
Preferably, the acquiring the SOC-OCV curve of each battery includes:
obtaining a battery pack to be detected, wherein the battery pack to be detected comprises a plurality of batteries with the same specification, and the batteries are connected in series or in parallel;
performing constant-current discharge operation on the battery pack to enable all batteries in the battery pack to reach discharge cut-off voltage and standing;
respectively recording the open circuit voltage corresponding to the current state of charge of each battery;
constant-current charging is carried out on the battery pack, the charging is stopped until the charging capacity of the battery pack reaches 5% of the state of charge, and the open-circuit voltage corresponding to the current state of charge of each battery is recorded;
continuously carrying out constant-current charging on the battery pack until the batteries are full, and acquiring open-circuit voltages of each battery under different charge states;
and drawing an OCV-SOC curve of each battery according to the open-circuit voltage under different charge states.
Preferably, the continuously performing constant current charging on the battery pack until the battery is full, collecting and obtaining the open circuit voltage of each battery under different charge states, includes:
s1, charging a battery pack, stopping charging the battery pack every preset time, standing the battery pack to a stable state, and respectively collecting the open-circuit voltage of each battery in the battery pack under the current charge state;
and S2, continuing to charge, and repeating the step S1 until the battery is full.
Preferably, the constant current charging is continuously performed on the battery pack until the battery is fully charged, and the current of the constant current charging is 0.05-0.2 ℃.
Preferably, the constant current discharging operation is performed on the battery pack, so that all the batteries in the battery pack reach a discharge cut-off voltage and stand still, and the method further comprises the following steps:
constant-current discharging is carried out on the battery pack until any one battery in the battery pack reaches a discharge cut-off voltage and standing is carried out;
and carrying out constant-current charging on the battery pack, so that any one battery in the battery pack reaches a charging cut-off voltage and stands still.
Preferably, the first time period is 12 hours, and the second time period is 24 hours.
The application discloses a lithium battery self-discharge rapid detection system, which comprises:
the OCV-SOC curve drawing module is used for drawing an OCV-SOC curve of each battery, wherein the OCV is open-circuit voltage, and the SOC is state of charge;
the first control and data acquisition module is used for respectively acquiring open-circuit voltages of each battery after the first time period is kept still and after the second time period is kept still, wherein the polarization of the battery disappears after the first time period is kept still, and the second time period is larger than the first time period;
the calculation module is used for calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range, and calculating the difference between the open circuit voltage of each battery of the battery pack after the battery is kept stand for a first time period and the open circuit voltage of the battery after the battery is kept stand for a second time period, and the difference is recorded as a battery standing pressure difference value; and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
Compared with the prior art, the technical scheme of the application has the following advantages:
1. according to the application, the self-discharge rate threshold value and the battery static pressure difference value of the battery are calculated by acquiring the OCV-SOC curve of the battery, the difference ratio of each battery can be calculated and obtained by the self-discharge rate threshold value and the battery static pressure difference value of the battery, and the self-discharge condition of each battery is analyzed according to the difference ratio of the battery, wherein the larger the difference ratio of the battery is, the larger the self-discharge rate of the battery is.
2. The application can realize the self-discharge detection of the battery at the battery core layer, can reduce the error of the self-discharge consistency screening of the battery, improves the detection precision, and can complete the detection in a short time, thereby saving the detection time.
Drawings
FIG. 1 is a flow chart of a method for detecting self-discharge of a battery according to the present application;
FIG. 2 is an OCV-SOC curve for a lithium iron phosphate battery;
fig. 3 is a voltage curve of the battery during resting 24h;
FIG. 4 is a graph of OCV-SOC plotted in the present application;
FIG. 5 is a graph showing the differential pressure values after the cell has been stationary for a second period of time;
FIG. 6 is a difference ratio of each cell in the battery;
FIG. 7 is a diagram showing the normalized difference ratio.
Detailed Description
The present application will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the application and practice it.
Referring to fig. 1, the application discloses a battery self-discharge detection method, which comprises the following steps:
an OCV-SOC curve of each battery is obtained, wherein OCV is open circuit voltage and SOC is state of charge.
Standing the batteries, and respectively collecting open-circuit voltages of each battery after the batteries are kept stand for a first time period and after the batteries are kept stand for a second time period, wherein the second time period is greater than the first time period;
calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open-circuit voltage difference value corresponding to a battery capacity attenuation preset range;
calculating the difference between the open circuit voltage of each battery after standing for a first period of time and the open circuit voltage of each battery after standing for a second period of time, and recording the difference as a battery standing differential pressure value;
and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
According to the application, the self-discharge rate threshold value and the battery static pressure difference value of the battery are calculated by acquiring the OCV-SOC curve of the battery, the difference ratio of each battery can be calculated and obtained by the self-discharge rate threshold value and the battery static pressure difference value of the battery, and the self-discharge condition of each battery is analyzed according to the difference ratio of the battery, wherein the larger the difference ratio of the battery is, the larger the self-discharge rate of the battery is. The application can realize the self-discharge detection of the battery at the battery core level, can reduce the error of the self-discharge consistency screening of the battery, and improve the detection precision, and can complete the detection in a short time, and can realize the rapid detection of the self-discharge rate of the battery in 24 hours.
In the present application, calculating the self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery includes:
open circuit voltage difference ΔOCV corresponding to a battery capacity decay of n% n%,i =△OCV SOC=m%,i -△OCV SOC=（m-n）%, i ;
Where i is the battery serial number, OCV SOC=m%,i Open circuit voltage at m% state of charge for battery i; OCV (optical clear video) SOC=（m-n）%,i Open circuit voltage at soc= (m-n)%; n is more than 0 and less than 100, m is more than 0 and less than or equal to 100, and n is more than m, m and n are natural numbers.
Preferably, when m=100, OCV SOC=100%，i Which is the open circuit voltage of battery i when fully charged. The 100% SOC is taken as the initial state of the battery, and the battery is not easily affected by self discharge at the moment, and the value of the battery is accurate.
Further, according to the self-discharge rate threshold value of the battery and the static pressure difference value of the battery, calculating to obtain the difference ratio of each battery comprises the following steps:
difference ratio M t1–t2,n%,i =△OCV t1-t2,i / △OCV n%,i ，
Wherein t1 is a first time period, t2 is a second time period, and i is a battery serial number;
△OCV t1-t2,i for battery iThe difference between the open circuit voltage after standing t1 and the open circuit voltage after standing t2 of battery i;
△OCV n%,i the open circuit voltage difference value corresponding to the capacity attenuation n% of the battery i is more than 0 and less than 100, and n is a natural number.
Calculating to obtain the difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery standing pressure difference value, and then further comprising: and setting a qualified threshold value, and screening the batteries with the difference ratio larger than the qualified threshold value as defective products. Specifically, the larger the difference ratio is, the larger the self-discharge rate is, and therefore, an appropriate threshold is set, when the difference ratio of a certain battery is larger than the qualification threshold, the battery is bad, and when the difference of the certain battery is smaller than the qualification threshold, the battery is good.
Preferably, the first period of time is 12 hours and the second period of time is 24 hours. The selection of the first time period and the second time period may be selected according to the following principles: after the first period, the battery is at a preferred point in time to reduce the effect of battery polarization, and after the second period, the OCV difference of the battery is at a maximum point in time. For the selection of the first time period and the second time period, the battery may be tested in advance to obtain a preferred value.
Further, in the present application, the SOC-OCV curve of each battery is obtained, comprising the steps of:
obtaining a battery pack to be detected, wherein the battery pack to be detected comprises a plurality of batteries with the same specification, and the batteries are connected in series or in parallel;
performing constant current discharge operation on the battery pack so that all batteries in the battery pack reach a discharge cut-off voltage and stand, including: performing constant-current discharge operation on the battery pack until any one battery reaches a discharge cut-off voltage; discharging the rest batteries which do not reach the cut-off voltage independently; ending discharging, and standing all batteries in the battery pack until the batteries are stable;
respectively recording the open circuit voltage corresponding to the current state of charge of each battery;
constant-current charging is carried out on the battery pack, the charging is stopped until the charging capacity of the battery pack reaches 5% of the state of charge, and the open-circuit voltage corresponding to the current state of charge of each battery is recorded;
continuously constant-current charging is carried out on the battery pack until the batteries are full, and the open-circuit voltage of each battery under different charge states is acquired and obtained, wherein the method comprises the following steps:
s1, charging a battery pack, stopping charging the battery pack every preset time, standing the battery pack to a stable state, and respectively collecting the open-circuit voltage of each battery in the battery pack under the current charge state;
and S2, continuing to charge, and repeating the step S1 until the battery is full.
Here, for constant current charging of the battery pack, when the charge capacity of the battery reaches 100% soc, the charging may be stopped; and the current of constant current charging is 0.05-0.2C.
And drawing an OCV-SOC curve of each battery according to the open-circuit voltage under different charge states.
In this example, the purpose of the rest is to stabilize the battery, typically for several minutes before testing, and the rest time may be 5-10 minutes.
In addition, in the charge and discharge of the above-described battery, a plurality of batteries may be connected in series or in parallel to form a battery pack, or a single battery may be respectively charged and discharged, so long as the OCV-SOC curve of each battery can be respectively plotted.
Performing constant current discharge operation on the battery pack so that all batteries in the battery pack reach a discharge cut-off voltage and stand still, and further comprising:
constant-current discharging is carried out on the battery pack until any one battery in the battery pack reaches a discharge cut-off voltage and standing is carried out;
and carrying out constant-current charging on the battery pack, so that any one battery in the battery pack reaches a charging cut-off voltage and stands still. By discharging and charging the battery pack, the batteries in the battery pack are in a relatively stable state.
The application discloses a lithium battery self-discharge rapid detection system which comprises an OCV-SOC curve drawing module, a first control and data acquisition module and a calculation module.
The OCV-SOC curve drawing module is used for drawing an OCV-SOC curve of each battery, wherein the OCV is open circuit voltage, and the SOC is state of charge.
The first control and data acquisition module is used for respectively acquiring open-circuit voltage of each battery after the first time period is kept still and after the second time period is kept still, wherein the polarization of the battery disappears after the first time period is kept still, and the second time period is larger than the first time period.
The calculation module is used for calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range, and calculating the difference between the open circuit voltage of each battery of the battery pack after the battery is kept stand for a first time period and the open circuit voltage of the battery after the battery is kept stand for a second time period, and the difference is recorded as a battery standing pressure difference value; and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
The technical scheme of the application is further described and explained below with reference to specific embodiments.
FIG. 2 is a graph of OCV versus SOC for a lithium iron phosphate battery, where the OCV varies greatly from 0% SOC to 20% SOC, and if the battery pack is charged to this state for self-discharge, there is a risk that a battery with poor performance in the battery pack may overdischarge; OCV corresponding to 20-90% SOC is positioned on a voltage platform, and the variation difference of the OCV of each battery in the battery pack is not obvious, so that the self-discharge analysis is not facilitated; if the battery pack is charged to the state for self-discharge, the OCV corresponding to the 90% SOC-100% SOC is greatly different, so that the self-discharge condition of each battery in the battery pack can be analyzed through the decrease of the OCV in a short time, the batteries with higher self-discharge speed can be screened, the standing time is shortened, and the analysis result of the self-discharge of each battery can be obtained more quickly.
Fig. 3 is a voltage curve of the battery during resting 24h, which is caused by the fact that polarization cannot completely disappear immediately after the battery stops charging. After the battery pack stops charging, ohmic polarization disappears immediately, but the overpotential caused by electrochemical polarization and concentration polarization still exists, the overpotential gradually decreases with time until the overpotential disappears, and the voltage gradually decreases with time to the voltage of the battery, namely the OCV of the battery. In view of the effect of polarization on voltage, it is necessary to select an appropriate point in time during the plateau as the start data in the self-discharge data analysis. Fig. 3 shows that the voltage reached a steady state after 12h during cell rest.
When the battery is in a static state, the OCV data after the battery pack is fully charged and is kept stand for 12h are selected for analysis in consideration of the influence of polarization on voltage and the change trend of OCV under different SOCs.
When self-discharge of a lithium battery is represented as capacity fading, according to the electric automobile battery test procedure handbook of the United States Advanced Battery Consortium (USABC), the chinese industry standard, and the existing references, it can be derived that the self-discharge rate of a lithium battery is 2%/month to 5%/month in general. According to the OCV-SOC curve of each battery, the OCV difference corresponding to the capacity fading of 2%/month-5%/month, namely the month self-discharge rate threshold value, can be obtained. The self-discharge condition of each battery can be analyzed through the ratio of the OCV difference value of each battery to the threshold value of the monthly self-discharge rate (actual decay voltage difference value/theoretical calibration voltage difference value) in the static process, if the voltage difference value in 24h has a large ratio in the theoretical calibration voltage difference value, the self-discharge rate is higher, and if the voltage difference value in 24h has a small ratio in the theoretical calibration voltage difference value, the self-discharge rate is lower.
Next, the battery was tested and calculated.
1. Firstly, selecting a battery pack for testing, wherein the test object of the embodiment is a lithium iron phosphate battery pack with poor consistency, and the battery pack comprises 6 batteries connected in series;
2. then, a test step is set:
standing for 5 minutes;
discharging the battery pack at a constant current of 1C until any one of the batteries reaches a discharge cut-off voltage of 2.7V, and standing for 1 h;
constant-current charging is carried out on the battery pack at 0.2C until any one battery reaches a charging cut-off voltage of 3.6V;
after standing for 1h, discharging the battery pack at a constant current rate of 1C until any one battery reaches a discharge cut-off voltage of 2.7V, and independently discharging the rest batteries which do not reach 2.7V;
after standing for 1 hour, recording the voltage at the end of standing as the OCV corresponding to the SOC;
constant-current charging is carried out on the battery pack at the rate of 0.05-0.2C until the charging capacity reaches 5% of the SOC, and the charging is stopped;
repeating the steps e and f until the charging capacity reaches 100% of the SOC, stopping charging, and drawing an OCV-SOC curve (figure 4);
after 12 minutes of standing h, recording the voltage once every hour until the voltage is stopped for 24 hours, wherein the first time period is selected for 12 hours, and the second time period is selected for 24 hours;
discharging the battery pack at a constant current rate of 1C until any single voltage reaches a discharge cut-off voltage of 2.7V;
3. finally, the difference ratio of each battery is calculated:
according to the OCV-SOC curve of each battery, the self-discharge rate threshold value of each battery is calculated, wherein the self-discharge rate threshold value can be a month self-discharge rate threshold value, so that the accuracy can be improved. SOC ranges corresponding to 2% and 5% of the damping capacity are 98% -100% SOC and 95% -100% SOC, respectively, and the SOC difference corresponding to the damping capacity can correspond to the OCV difference (delta OCV) of each battery 2%/m,i And OCV (optical clear video) 5%/m,i ). The calculation formula is delta OCV 2%/m,i =△OCV SOC=100%,i -△OCV SOC=98%, i ; △OCV 5%/m,i =△OCV SOC=100%,i -△OCV SOC=95%,i . Wherein i is a battery serial number; OCV (optical clear video) SOC=100%,i OCV for battery i at soc=100%; OCV (optical clear video) SOC=98%,i OCV for battery i at soc=98%; OCV (optical clear video) SOC=95%,i OCV for battery i at soc=95%. The self-discharge rate threshold values of the respective cells in the battery pack are shown in table 1.
TABLE 1
The differential pressure value was calculated for each cell in the stack at rest for 12h-24h (fig. 5). The calculation formula is delta OCV 12h-24h,i =OCV 12h,i -OCV 24h, i 。
The difference ratio of each cell in the battery pack was calculated and recorded as the M value (map6). The calculation formula is M 12h–24h,2%/m,i =△OCV 12h-24h,i / △OCV 2%/m,i ；M 12h–24h,5%/m,i =△OCV 12h-24h,i / △OCV 5%/m,i . Due to OCV 2%/m,i And delta OCV 5%/m,i M of the same cell with different values 12h-24h,2%/m,i And M 12h-24h,5%/m,i The distributed relative discrete M values of (c) may be normalized by a normalization method. With the relative position of each point distribution kept unchanged, a set of data is scaled to a range of 0-1 (fig. 7). The normalization formula is M' = (M-M) min )/(M max -M min )。
The results of FIG. 7 show that the two points (M 'for each cell' 12h-24h,2%/m,i And M' 12h-24h,5%/m,i ) Is relatively close to each other and M' 12h-24h,2%/m,i With M' 12h-24h,5%/m,i The similarity of the trend of change is relatively high. Therefore, by analyzing the self-discharge condition of each battery cell in the battery pack through the ratio of the OCV difference value of 12h-24h to the threshold value of the self-discharge rate in the standing process, the battery cells with larger self-discharge can be selected: the self-discharge rates of the batteries No. 1 and No. 5 are larger, and the self-discharge rates of the batteries No. 3 and No. 4 are smaller than those of other batteries.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present application will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the application.
Claims (10)
1. A method for detecting self-discharge of a battery, comprising the steps of:
acquiring an OCV-SOC curve of each battery, wherein the OCV is open circuit voltage and the SOC is state of charge;
standing the batteries, and respectively collecting open-circuit voltages of each battery after the batteries are kept stand for a first time period and after the batteries are kept stand for a second time period, wherein the second time period is greater than the first time period;
calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range;
calculating the difference between the open circuit voltage of each battery after standing for a first period of time and the open circuit voltage of each battery after standing for a second period of time, and recording the difference as a battery standing differential pressure value;
and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
2. The battery self-discharge detection method according to claim 1, wherein the calculating the self-discharge rate threshold value of each battery from the OCV-SOC curve of each battery includes:
open circuit voltage difference ΔOCV corresponding to a battery capacity decay of n% n%,i =△OCV SOC=m%,i -△OCV SOC=（m-n）%, i ;
Where i is the battery serial number, OCV SOC=m%,i Open circuit voltage at m% state of charge for battery i; OCV (optical clear video) SOC=（m-n）%,i Open circuit voltage at soc= (m-n)%; n is more than 0 and less than 100, m is more than 0 and less than or equal to 100, and n is more than m, m and n are natural numbers.
3. The method according to claim 1, wherein calculating a difference ratio for each cell based on the self-discharge rate threshold value of the cell and the cell rest pressure difference value comprises:
difference ratio M t1–t2,n%,i =△OCV t1-t2,i / △OCV n%,i ，
Wherein t1 is a first time period, t2 is a second time period, and i is a battery serial number;
△OCV t1-t2,i the difference between the open circuit voltage of the battery i after standing t1 and the open circuit voltage of the battery i after standing t 2;
△OCV n%,i for the capacity of battery iThe open circuit voltage difference corresponding to the attenuation n% is more than 0 and less than 100, and n is a natural number.
4. The method for detecting self-discharge of a battery according to claim 1, wherein the calculating to obtain the difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery rest pressure difference value further comprises:
and setting a qualified threshold value, and screening the batteries with the difference ratio larger than the qualified threshold value as defective products.
5. The battery self-discharge detection method according to claim 1, wherein the acquiring the SOC-OCV curve of each battery includes:
obtaining a battery pack to be detected, wherein the battery pack to be detected comprises a plurality of batteries with the same specification, and the batteries are connected in series or in parallel;
performing constant-current discharge operation on the battery pack to enable all batteries in the battery pack to reach discharge cut-off voltage and standing;
respectively recording the open circuit voltage corresponding to the current state of charge of each battery;
constant-current charging is carried out on the battery pack, the charging is stopped until the charging capacity of the battery pack reaches 5% of the state of charge, and the open-circuit voltage corresponding to the current state of charge of each battery is recorded;
continuously carrying out constant-current charging on the battery pack until the batteries are full, and acquiring open-circuit voltages of each battery under different charge states;
and drawing an OCV-SOC curve of each battery according to the open-circuit voltage under different charge states.
6. The method for detecting self-discharge of a battery according to claim 5, wherein the step of continuously charging the battery pack with a constant current until the battery is fully charged, collecting and obtaining the open circuit voltage of each battery under different charge states comprises:
s1, charging a battery pack, stopping charging the battery pack every preset time, standing the battery pack to a stable state, and respectively collecting the open-circuit voltage of each battery in the battery pack under the current charge state;
and S2, continuing to charge, and repeating the step S1 until the battery is full.
7. The method for detecting self-discharge of a battery according to claim 5, wherein the constant-current charging is continued until the battery is fully charged, and the current of the constant-current charging is 0.05-0.2 ℃.
8. The method for detecting self-discharge of a battery according to claim 5, wherein said constant-current discharge operation is performed on the battery pack such that all the batteries in the battery pack reach a discharge cut-off voltage and stand still, further comprising before:
constant-current discharging is carried out on the battery pack until any one battery in the battery pack reaches a discharge cut-off voltage and standing is carried out;
and carrying out constant-current charging on the battery pack, so that any one battery in the battery pack reaches a charging cut-off voltage and stands still.
9. The battery self-discharge detection method according to claim 1, wherein the first period of time is 12 hours and the second period of time is 24 hours.
10. A lithium battery self-discharge rapid detection system, comprising:
the OCV-SOC curve drawing module is used for drawing an OCV-SOC curve of each battery, wherein the OCV is open-circuit voltage, and the SOC is state of charge;
the first control and data acquisition module is used for respectively acquiring open-circuit voltages of each battery after the first time period is kept still and after the second time period is kept still, wherein the polarization of the battery disappears after the first time period is kept still, and the second time period is larger than the first time period;
the calculation module is used for calculating a self-discharge rate threshold value of each battery according to the OCV-SOC curve of each battery, wherein the self-discharge rate threshold value is an open circuit voltage difference value corresponding to a battery capacity attenuation preset range, and calculating the difference between the open circuit voltage of each battery of the battery pack after the battery is kept stand for a first time period and the open circuit voltage of the battery after the battery is kept stand for a second time period, and the difference is recorded as a battery standing pressure difference value; and calculating to obtain a difference ratio of each battery according to the self-discharge rate threshold value of the battery and the battery static pressure difference value, wherein the difference ratio is equal to the ratio of the battery static pressure difference value to the self-discharge rate threshold value of the battery.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310908010.4A CN116626518A (en) | 2023-07-24 | 2023-07-24 | Battery self-discharge detection method and system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310908010.4A CN116626518A (en) | 2023-07-24 | 2023-07-24 | Battery self-discharge detection method and system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116626518A true CN116626518A (en) | 2023-08-22 |
Family
ID=87590659
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310908010.4A Pending CN116626518A (en) | 2023-07-24 | 2023-07-24 | Battery self-discharge detection method and system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116626518A (en) |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102303023A (en) * | 2011-07-22 | 2012-01-04 | 万向电动汽车有限公司 | Method for detecting and sorting self-discharge performance of lithium iron phosphate battery |
| CN103008261A (en) * | 2012-12-24 | 2013-04-03 | 天津力神电池股份有限公司 | Method for sorting degrees of self-discharging of lithium ion batteries |
| CN107219468A (en) * | 2017-06-28 | 2017-09-29 | 湖北金泉新材料有限责任公司 | A kind of lithium ion battery self discharge screening technique and Li-ion batteries piles |
| CN110297191A (en) * | 2019-08-07 | 2019-10-01 | 深圳市思商科技有限公司 | A kind of self-discharge of battery test method |
| CN111929603A (en) * | 2020-07-14 | 2020-11-13 | 东风时代(武汉)电池系统有限公司 | Battery monomer self-discharge measuring and calculating method and device and computer readable storage medium |
| CN113285513A (en) * | 2021-06-11 | 2021-08-20 | 湖北亿纬动力有限公司 | Method, device, equipment and storage medium for evaluating self-discharge consistency of battery |
| CN113447838A (en) * | 2021-07-07 | 2021-09-28 | 江铃汽车股份有限公司 | Lithium battery self-discharge detection method and device |
| CN113484773A (en) * | 2021-08-03 | 2021-10-08 | 湖北亿纬动力有限公司 | Screening method for self-discharge of lithium ion battery |
| CN115343639A (en) * | 2022-07-26 | 2022-11-15 | 联动天翼新能源有限公司 | Method for testing self-discharge of battery |
-
2023
- 2023-07-24 CN CN202310908010.4A patent/CN116626518A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102303023A (en) * | 2011-07-22 | 2012-01-04 | 万向电动汽车有限公司 | Method for detecting and sorting self-discharge performance of lithium iron phosphate battery |
| CN103008261A (en) * | 2012-12-24 | 2013-04-03 | 天津力神电池股份有限公司 | Method for sorting degrees of self-discharging of lithium ion batteries |
| CN107219468A (en) * | 2017-06-28 | 2017-09-29 | 湖北金泉新材料有限责任公司 | A kind of lithium ion battery self discharge screening technique and Li-ion batteries piles |
| CN110297191A (en) * | 2019-08-07 | 2019-10-01 | 深圳市思商科技有限公司 | A kind of self-discharge of battery test method |
| CN111929603A (en) * | 2020-07-14 | 2020-11-13 | 东风时代(武汉)电池系统有限公司 | Battery monomer self-discharge measuring and calculating method and device and computer readable storage medium |
| CN113285513A (en) * | 2021-06-11 | 2021-08-20 | 湖北亿纬动力有限公司 | Method, device, equipment and storage medium for evaluating self-discharge consistency of battery |
| CN113447838A (en) * | 2021-07-07 | 2021-09-28 | 江铃汽车股份有限公司 | Lithium battery self-discharge detection method and device |
| CN113484773A (en) * | 2021-08-03 | 2021-10-08 | 湖北亿纬动力有限公司 | Screening method for self-discharge of lithium ion battery |
| CN115343639A (en) * | 2022-07-26 | 2022-11-15 | 联动天翼新能源有限公司 | Method for testing self-discharge of battery |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100903489B1 (en) | Method of testing cycle life of lithium rechargeable battery | |
| CN108333526B (en) | Battery capacity detection method and device | |
| KR101750739B1 (en) | Device for measuring state of charge of secondary battery and method for measuring state of charge of secondary battery | |
| CN108160531B (en) | Battery self-discharge sorting method | |
| CN109663756B (en) | Battery core screening method and medium based on self-discharge rate | |
| CN112858941B (en) | Acceleration test and service life evaluation method for lithium iron phosphate power battery | |
| CN111929603A (en) | Battery monomer self-discharge measuring and calculating method and device and computer readable storage medium | |
| CN113533988B (en) | Long-term circulation capacity attenuation analysis method for lithium ion battery | |
| CN111580003A (en) | Impedance spectrum-based secondary battery inconsistency identification method and apparatus | |
| CN115079026A (en) | SOC automatic calibration method and device suitable for high-voltage energy storage system | |
| CN113578792B (en) | Lithium ion battery self-discharge screening method and device and storage medium | |
| CN113238152A (en) | Lithium battery self-discharge detection method | |
| CN111551868B (en) | Consistency analysis method for lithium iron phosphate battery system | |
| CN116626518A (en) | Battery self-discharge detection method and system | |
| CN116520173A (en) | Method for measuring self-discharge rate of battery | |
| CN112108400A (en) | Test method for predicting cycle performance of soft package battery | |
| CN114720799A (en) | Method for accelerated evaluation of cycle performance of lithium ion battery electrode material | |
| CN115343639A (en) | Method for testing self-discharge of battery | |
| CN112666481B (en) | Battery life detection method and device | |
| CN117169749A (en) | Method for generating battery capacity prediction model, prediction method and device thereof | |
| CN109669136B (en) | Battery box charging and discharging test method | |
| CN111007416A (en) | Method for diagnosing the state of health of a battery | |
| KR102649550B1 (en) | Battery formation process using electrochemical impedance spectroscopy | |
| US10473725B2 (en) | Method and system for calculating low voltage expression level of a secondary battery | |
| CN116165562B (en) | Battery self-discharge detection method, device, apparatus, storage medium and program product |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |