CN113514771A - Battery impedance service life estimation method and system - Google Patents
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- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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- G—PHYSICS
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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Abstract
The invention provides a battery impedance life estimation method, which comprises the steps of collecting the SOC, the temperature and the internal resistance of the discharge change of a battery to construct a new battery impedance table before the battery is put into use; after the battery is put into use, acquiring the current discharging SOC, the temperature and the battery state information of the battery to detect the stable state of the internal resistance of the battery, and acquiring the voltage, the current, the SOC and the temperature of the battery before and after the voltage drop is generated by the battery each time when the internal resistance of the battery is in the stable state; calculating the direct current internal resistance, SOC and temperature under each internal resistance stable state according to the acquired voltage, current, SOC and temperature before and after voltage drop; calculating the reliability, selecting internal resistance in a new battery impedance table through the reliability to obtain new battery impedance and obtaining the current life battery impedance according to the direct current internal resistance in the stable state of the internal resistance; and calculating the discharge impedance life of the battery according to the two impedances. The invention realizes on-line estimation based on the ACB technology and has better robustness and reliability.
Description
Technical Field
The invention relates to the technical field of storage battery management, in particular to a method and a system for estimating the impedance service life of a battery.
Background
Battery impedance lifetime, which may directly affect battery discharge power, is one of the core parameters characterizing battery performance and lifetime. The storage capacity and the charge-discharge capacity of the battery can be reduced along with the repeated use of the battery pack until the use requirement cannot be met. Therefore, battery impedance lifetime is typically observed and reflected in electrical ground internal resistance decay. However, the existing electric/hybrid power battery utilizes a model and an online estimation method to measure the impedance life of the battery, and the methods have the defects of poor estimation robustness, poor precision, high calculation complexity and the like.
Therefore, there is a need for an online estimation method for battery impedance lifetime, which can overcome the problems of the existing online estimation method for battery impedance lifetime and has better robustness and reliability.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a method and a system for estimating a Battery impedance life, which are used for directly measuring the Battery impedance increase based on the characteristic of the pulse working condition generated by the short-time heating of an All-weather Battery (ACB), so as to realize the direct measurement of the Battery impedance life, overcome the problems existing in the existing online estimation of the Battery impedance life, and have better robustness and reliability.
In order to solve the above technical problem, an embodiment of the present invention provides a method for estimating a battery impedance lifetime, where the method includes:
before the battery is put into use, the SOC, the temperature and the internal resistance which change along with the sampling period during the discharge of the battery are collected to construct a new battery impedance table;
after the battery is put into use, acquiring SOC, temperature and battery state information which change along with a sampling period when the battery is discharged at this time to detect the internal resistance stable state of the battery discharged at this time, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the battery discharged at this time generates corresponding voltage drop when the internal resistance is in the stable state each time;
calculating the direct current internal resistance, SOC and temperature of the battery discharging this time when the internal resistance is in a stable state every time according to the acquired voltage, current, SOC and temperature before and after the voltage drop of the battery is generated every time;
acquiring the acquisition time difference of the current discharge of the battery corresponding to the last discharge to obtain the reliability, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and temperature of the current discharge battery with the internal resistance in the stable state each time after the reliability is judged to be greater than or equal to the preset threshold, and calculating the current life battery impedance according to the calculated direct current internal resistance of the current discharge battery with the internal resistance in the stable state each time;
and calculating the discharge impedance life of the battery according to the new battery impedance, the current life battery impedance and the internal resistance given by the manufacturer when the battery life is finished.
Wherein the reliability is determined by freshness and stability; wherein the content of the first and second substances,
the degree of confidence is equal to a product between the freshness and the degree of stability;
the freshness K1 is expressed by the formula K1 ═ a × e(-t/b)Calculating to obtain; wherein a and b are fixed constants and can be obtained by calibration according to the aging test data of the calendar life of the battery; t is the acquisition time difference between the current discharge of the battery and the last discharge of the battery;
the stability K2 is a constant 1.
The step of detecting the internal resistance stable state of the battery discharged this time by acquiring the SOC, the temperature and the battery state information which change along with the sampling period when the battery is discharged this time specifically includes:
if the SOC acquired by the battery in the current sampling period is detected to be within a preset SOC range, the temperature is within a preset temperature range, and the battery state information simultaneously meets the conditions that the discharge current duration is greater than a preset time threshold, the discharge current variation value is smaller than a preset limit value in the discharge current duration, the varied discharge current is greater than a preset current threshold, the balance is not started and no fault exists, the internal resistance of the battery in the current sampling period is determined to be in a stable state; otherwise, determining that the internal resistance of the battery in the current sampling period is not in a stable state.
Wherein the preset SOC range is [ 40%, 60% ]; the preset temperature range is [25 ℃,40 ℃; the discharge current duration is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein, C is 100A.
Calculating the discharge impedance service life of the battery by using a formula SOH (Rpr-Rnew)/(Reol-Rnew); and the SOH is the battery discharge impedance life, the Rnew is the new battery impedance, the Rpr is the current life battery impedance, and the Reol is the internal resistance of the battery at the end of the life given by the manufacturer.
The battery is an all-weather battery, and the all-weather battery comprises a battery body, a switch and a heating sheet.
The new battery impedance meter is formed by collecting SOC, temperature and internal resistance which change along with a sampling period when a battery body in the all-weather battery discharges after a switch is switched off before the all-weather battery is put into use.
Each time, the stable state of the internal resistance is detected by collecting SOC, temperature and battery state information which are changed along with a sampling period when a battery body in the all-weather battery discharges after a switch is switched off after the all-weather battery is put into use;
the voltage drop generated in each stable internal resistance state is generated when the switch of the all-weather battery is closed and the battery body and the heating sheet are electrically connected and conducted on the basis that the internal resistance is in the stable state each time.
Wherein the method further comprises:
and according to the calculated SOC and temperature of the battery discharged this time under the condition that the internal resistance is in a stable state every time, finding the internal resistance in the new battery impedance table and updating the internal resistance by using the corresponding direct current internal resistance to obtain a battery impedance table with the current service life, which is formed after the new battery impedance table is updated.
The embodiment of the invention also provides a battery impedance service life estimation system, which comprises a new battery impedance table construction unit, a current service life battery state online measurement unit, a current service life battery impedance online calculation unit, a current service life battery impedance calculation unit and a current service life battery discharge impedance service life estimation unit; wherein the content of the first and second substances,
the new battery impedance meter constructing unit is used for acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery is discharged to construct a new battery impedance meter before the battery is put into use;
the current-life battery state online measuring unit is used for acquiring SOC, temperature and battery state information which change along with a sampling period when the battery is discharged at this time to detect the internal resistance stable state of the battery discharged at this time after the battery is put into use, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the battery discharged at this time generates corresponding voltage drop when the internal resistance is in the stable state;
the current-life battery state online calculation unit is used for calculating the direct-current internal resistance, SOC and temperature of the battery discharged at this time under the condition that the internal resistance is in a stable state every time according to the acquired voltage, current, SOC and temperature before and after the voltage drop is generated by the battery every time;
the current-life battery impedance calculation unit is used for acquiring the reliability of the battery by acquiring the acquisition time difference of the current discharge corresponding to the last discharge, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and temperature of the current discharge battery with the internal resistance in the stable state each time after the reliability is judged to be greater than or equal to the preset threshold value, and calculating the current-life battery impedance according to the calculated direct current internal resistance of the current discharge battery with the internal resistance in the stable state each time;
and the current-life battery discharge impedance life estimation unit is used for calculating the battery discharge impedance life according to the new battery impedance, the current-life battery impedance and the internal resistance given by the manufacturer when the battery life is finished.
The embodiment of the invention has the following beneficial effects:
the method is used for directly measuring the impedance increase of the Battery based on the characteristic of the All-weather Battery (ACB) under the working condition of pulse generated by short-time heating, thereby realizing the direct measurement of the impedance life of the Battery, overcoming the problems existing in the existing online estimation of the impedance life of the Battery, and having better robustness and reliability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art 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 within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a flowchart of a method for estimating a lifetime of a battery impedance according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for estimating the impedance lifetime of a battery according to an embodiment of the present invention applied to an all-weather battery;
FIG. 3 is a diagram of the application scenario of FIG. 2;
fig. 4 is a schematic structural diagram of a battery impedance lifetime estimation system 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, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a method for estimating a battery impedance life according to an embodiment of the present invention includes the following steps:
step S1, before the battery is put into use, the SOC, the temperature and the internal resistance which change along with the sampling period when the battery is discharged are collected to construct a new battery impedance table;
step S2, after the battery is put into use, collecting SOC, temperature and battery state information which change along with the sampling period when the battery is discharged to detect the internal resistance stable state of the battery discharged this time, and further collecting the voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the battery discharged this time generates corresponding voltage drop when the internal resistance is in the stable state each time;
step S3, calculating the direct current internal resistance, SOC and temperature of the battery discharging this time under the stable state of internal resistance each time according to the collected voltage, current, SOC and temperature before and after voltage drop of the battery each time;
step S4, obtaining the reliability by obtaining the collection time difference of the current discharging of the battery corresponding to the last discharging, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and temperature of the current discharging battery with the internal resistance in the stable state each time after judging that the reliability is more than or equal to the preset threshold value, and calculating the current life battery impedance according to the calculated direct current internal resistance of the current discharging battery with the internal resistance in the stable state each time;
and step S5, calculating the battery discharge impedance life according to the new battery impedance, the current life battery impedance and the internal resistance at the end of the battery life given by the manufacturer.
Specifically, in step S1, the laboratory device is used to measure the internal resistance of the new battery at different SOCs and temperatures during discharging through the battery management system, and a new battery impedance table Tnew (which is kept constant as an evaluation reference of the entire life cycle of the battery) is stored, where the new battery impedance table Tnew is a relationship table formed by associating the SOC, the temperature, and the internal resistance that change with the sampling cycle during discharging of the new battery.
It should be noted that the sampling period may be divided according to time, SOC or temperature, and may be designed according to actual requirements; if each sampling period is set at intervals of 5s, 10s and the like or at random; for another example, each sampling period is set for the SOC with a decreasing rule of 5%, and so on; as another example, each sampling period is set at an increasing rule of 1 ℃ per rise of temperature, and so on.
In step S2, after the battery has been put into use for a period of time (e.g., 1 month, 1 year, etc.), first collecting SOC, temperature and battery state information varying with each sampling period in the current discharging state of the battery through the battery management system; the battery status information includes, but is not limited to, a discharge current duration, a discharge current magnitude, an equilibrium state, and a fault state. It should be noted that the battery discharging at this time can be distinguished from the last discharging and the next discharging by a mark, and the time difference between two adjacent discharging measurements, i.e. the acquisition time difference, is calculated by the starting time of the sampling period.
Secondly, the battery management system judges the internal resistance stable state of the battery according to the SOC, the temperature and the battery state information which change along with each sampling period when the battery discharges at this time, and the method specifically comprises the following steps:
if the battery management system detects that the SOC acquired by the battery in the current sampling period is within a preset SOC range (such as [ 40%, 60%), the temperature is within a preset temperature range (such as [25 ℃,40 ℃), and the battery state information simultaneously meets the conditions that the discharge current duration is greater than a preset time threshold (such as 60s), the discharge current variation value is less than a preset limit value (such as 5A) in the discharge current duration (such as 60s), the discharge current variation value is greater than a preset current threshold (such as 0.8C, C is 100A), the battery internal resistance in the current sampling period is determined to be in a stable state if the balance is not started and no fault exists; on the contrary, it is determined that the internal resistance of the battery in the current sampling period is not in a stable state, that is, if the battery management system detects that the SOC acquired by the battery in the current sampling period exceeds a preset SOC range (e.g., > 60% or < 40%), the temperature exceeds a preset temperature range (e.g., >40 ℃ or <25 ℃), the discharge current duration in the battery state information is less than or equal to a preset time threshold (e.g., <60s), or the discharge current variation value is greater than or equal to a preset limit (e.g., >5A) and the varied discharge current is less than or equal to a preset current threshold (e.g., 0.6C <0.8C) in the discharge current duration (e.g., 60s), and at least one of balanced start and a fault exists, it is determined that the internal resistance of the battery in the current sampling period is not in a stable state. In one embodiment, the predetermined SOC range is [ 40%, 60% ]; the preset temperature range is [25 ℃,40 ℃; the discharge current duration is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein, C is 100A.
It is understood that the battery dc internal resistance identification steady state determination condition may be evaluated according to conditions such as voltage, current, temperature discharge time, and the like, and the combination is not limited to the above-mentioned combination of conditions.
Then, when the internal resistance of the discharging battery is in a stable state every time, the battery management system generates corresponding control pulses to enable the battery to generate voltage drop, further collects the voltage, current, SOC and temperature before and after the voltage drop of the battery is generated every time, and records the current (Ib & Ia), the voltage (Vb & Va), the electric quantity of the battery cell (SOCb & SOCa) and the temperature (Tb & Ta) before and after the voltage drop pulse of the battery is generated every time.
It should be noted that the direct current internal resistance of the battery shows nonlinear change along with the temperature and the SOC state, the internal resistance of the battery has large change at the upper and lower limits of the SOC and the upper and lower limits of the temperature range, and the accuracy of online measurement of the internal resistance is poor, so that the stable state interval of the internal resistance of the battery can be calibrated through experiments, and the stable interval is selected for online internal resistance estimation, so that the accuracy can be improved.
In step S3, according to the formula (1), the direct current internal resistance DCR of the current discharging battery is calculated in each time the internal resistance is in a stable state;
DCR＝(Vb-Va)/(Ib-Ia) (1)：
according to a formula (2), calculating the SOC of the discharging battery when the internal resistance is in a stable state every time;
SOC＝(SOCb+SOCa)/2 (2)；
and (4) calculating the temperature T of the discharge battery in the stable state of the internal resistance every time according to the formula (3).
T＝(Tb+Ta)/2 (3)。
In step S4, first, a reliability K is calculated, which is determined by the freshness K1 and the stability K2.
In one embodiment, the confidence level K is equal to the product of the freshness K1 and the stability K2, i.e., K1K 2, K ranges from [0,1], and the closer the value of K is to 1, the higher the confidence level.
Wherein, the freshness K1 is calculated by formula (4):
K1＝a*e(-t/b) (4)；
wherein a and b are fixed constants and can be obtained by calibration according to the aging test data of the calendar life of the battery; t is the acquisition time difference between the current discharge of the battery and the last discharge of the battery; the stability K2 is constant 1 because the internal resistance is not in the steady state K2 ═ 0.
Secondly, if the judgment reliability K > is equal to a preset threshold value of 0.85, finding corresponding internal resistance in a new battery impedance table Tnew according to the SOC and the temperature calculated when the internal resistance of the discharged battery is in a stable state every time, and calculating new battery impedance Rnew by averaging; meanwhile, according to the direct current internal resistance DCR of the discharge battery in a stable state every time, the battery impedance Rpr of the current service life is calculated by averaging.
It can be understood that, if the reliability K is less than the preset threshold 0.85, it indicates that the calculated direct-current internal resistance is not preferable when the internal resistance of the discharging battery is in a stable state every time, so that the discharging impedance life SOH of the battery in step S5 does not need to be recalculated, and the previous value is continuously maintained, thereby ensuring the accuracy and robustness of the measurement. Meanwhile, the direct current internal resistance of the discharged battery is calculated every time the internal resistance is in a stable state, a model and an estimation algorithm are not needed, and the calculation complexity is reduced.
In step S5, the battery discharge impedance lifetime is calculated by equation (5);
SOH＝(Rpr-Rnew)/(Reol-Rnew) (5)；
where SOH is the battery discharge impedance life and Reol is the internal resistance at the end of battery life as given by the manufacturer.
In an embodiment of the invention, the method further comprises:
and according to the calculated SOC and temperature of the battery discharged this time under the condition that the internal resistance is in a stable state every time, finding the internal resistance in the new battery impedance table and updating the internal resistance by using the corresponding direct current internal resistance to obtain a battery impedance table with the current service life, which is formed after the new battery impedance table is updated.
Referring to fig. 2, taking an all-weather battery (as shown in fig. 3) formed by connecting a battery body, a switch and a heating plate in series as an example, the specific steps of further analyzing the battery impedance lifetime estimation method in the embodiment of the present invention are as follows:
step S10, before the all-weather battery is put into use, collecting the SOC, the temperature and the internal resistance which change along with the sampling period when the battery body in the all-weather battery discharges after the switch is switched off to construct a new battery impedance table;
step S20, after the all-weather battery is put into use, collecting SOC, temperature and battery state information which change along with a sampling period when the battery body in the all-weather battery discharges after a switch is switched off to detect the internal resistance stable state of the battery body discharging this time, and further collecting the voltage, the current, the SOC and the temperature before and after the voltage drop of the battery body is generated each time after the battery body discharging this time generates corresponding voltage drop when the internal resistance is in the stable state each time;
step S30, calculating the direct current internal resistance, SOC and temperature of the battery body discharged this time when the internal resistance is in a stable state each time according to the collected voltage, current, SOC and temperature before and after the voltage drop of the battery body is generated each time;
step S40, obtaining the reliability by acquiring the acquisition time difference of the current discharge of the battery body corresponding to the last discharge, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and the temperature of the current discharge battery body with the internal resistance in the stable state each time after judging that the reliability is more than or equal to the preset threshold value, and calculating the current life battery impedance according to the calculated direct current internal resistance of the current discharge battery body with the internal resistance in the stable state each time;
and step S50, calculating the battery discharge impedance life according to the new battery impedance, the current life battery impedance and the internal resistance at the end of the battery life given by the manufacturer.
In step S10, the laboratory device measures the internal resistances of the battery body of the new all-weather battery at different SOCs and temperatures during discharging after the switch is turned off, and stores a new battery impedance table Tnew (which is kept constant as the evaluation reference of the entire life cycle of the battery) in which the SOC, the temperature, and the internal resistance that change with each sampling period during discharging of the battery body of the new all-weather battery after the switch is turned off are associated with each other. It is understood that the sampling period setting in step S10 is the same as the sampling period setting in step S1, and is not described again here.
In step S20, after the all-weather battery has been put into use for a period of time (e.g., 1 and, 1 year), first, the battery management system collects SOC, temperature and battery state information, which changes with each sampling period when the battery body in the all-weather battery discharges this time after the switch is turned off; the battery status information includes, but is not limited to, a discharge current duration, a discharge current magnitude, an equilibrium state, and a fault state. It should be noted that the battery body can be distinguished from the last discharge and the next discharge by the mark, and the time difference between two adjacent discharge measurements, i.e. the acquisition time difference, is calculated by the starting time of the sampling period.
Secondly, the battery management system judges the internal resistance stable state of the battery according to the SOC, the temperature and the battery state information which are changed along with each sampling period when the battery body discharges the time after the switch is switched off, and the method specifically comprises the following steps:
if the battery management system detects that the SOC acquired by the battery body in the current sampling period is within a preset SOC range (such as [ 40%, 60%), the temperature is within a preset temperature range (such as [25 ℃,40 ℃), and the battery state information simultaneously meets the conditions that the discharge current duration is greater than a preset time threshold (such as 60s), the discharge current variation value is less than a preset limit (such as 5A) in the discharge current duration (such as 60s), the discharge current variation value is greater than a preset current threshold (such as 0.8C, C is 100A), the balance is not started and no fault exists, and the internal resistance of the battery in the current sampling period is determined to be in a stable state; on the contrary, it is determined that the internal resistance of the battery body in the current sampling period is not in a stable state, that is, if the battery management system detects that the SOC acquired by the battery body in the current sampling period exceeds a preset SOC range (e.g., > 60% or < 40%), the temperature exceeds a preset temperature range (e.g., >40 ℃ or <25 ℃), the discharge current duration in the battery state information is less than or equal to a preset time threshold (e.g., <60s), or the discharge current variation value is greater than or equal to a preset limit value (e.g., >5A) and the varied discharge current is less than or equal to a preset current threshold (e.g., 0.6C <0.8C) in the discharge current duration (e.g., 60s), and at least one of balanced start and a fault exists, it is determined that the internal resistance of the battery body in the current sampling period is not in a stable state. In one embodiment, the predetermined SOC range is [ 40%, 60% ]; the preset temperature range is [25 ℃,40 ℃; the discharge current duration is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein, C is 100A.
Then, when the internal resistance of the battery body is in a stable state every time, the battery management system controls the on-off switch of the all-weather battery to realize the electric connection and conduction between the battery body and the heating sheet so as to enable the battery body to generate voltage drop, so that the voltage, the current, the SOC and the temperature before and after the voltage drop is generated by the battery body at the time can be collected, namely, the high-power pulse is generated by utilizing the all-weather battery ACB technology, and the current (Ib & Ia), the voltage (Vb & Va), the electric quantity of the battery cell (SOCb & SOCa) and the temperature (Tb & Ta) before and after the voltage drop pulse is generated by the battery body at the time are recorded.
In one embodiment, in fig. 2, U1 is a battery body, S1 is a switch, and R1 is a heating plate; after the battery management system determines that the battery body U1 is in the stable internal resistance state, the control pulse is generated to switch the switch S1 of the ACB battery to form voltage drop, so that the battery body U1 generates pulse discharge current. The pulse current is not less than 0.8C and the pulse duration is not less than 10 s.
Finally, after the voltage, the current, the SOC and the temperature before and after each voltage drop of the battery body are collected when the internal resistance of the battery body is in a stable state every time, the switch is immediately turned off, so that the battery body is continuously in a discharging state, the SOC, the temperature and the battery state information which change in the next sampling period can be collected again, namely, the battery body can meet the conditions of the stable state of the internal resistance in a plurality of sampling periods, and the current (Ib & Ia), the voltage (Vb & Va), the SOC (SOCb & SOCa) and the temperature (Tb & Ta) before and after voltage drop pulses of a plurality of groups of batteries are conditionally obtained. In one embodiment, there are a plurality of SOCs within the SOC range of [ 40%, 60% ], such as 55%, 50%, 45%, 40%, and the temperatures are within the predetermined temperature range of [25 ℃,40 ℃ ], the battery status information simultaneously satisfies that the discharge current duration is greater than the predetermined time threshold 60s, the discharge current variation value is less than the predetermined limit 5A within the discharge current duration 60s, and the varied discharge current is greater than the predetermined current threshold 0.8C, the equalization is not turned on, and there is no fault. It can be understood that the switch is immediately turned off after the voltage, current, SOC and temperature before and after the voltage drop of the battery body is generated when the internal resistance is in a stable state, so as to avoid the problem of data measurement error caused by the loss of the battery by the heating sheet.
In step S30, the dc internal resistance DCR, SOC and temperature T of the battery body during each time of the internal resistance being in the stable state are calculated according to the formulas (1) to (3) in step S3, and the description thereof is omitted.
In step S40, first, the confidence level K is calculated according to the formula (4) and the related conditions in step S4, please refer to the related contents in step S4, which is not described herein again.
Secondly, if the judgment reliability K > is equal to a preset threshold value of 0.85, finding corresponding internal resistance in a new battery impedance table Tnew according to the SOC and the temperature calculated when the internal resistance of the battery body is in a stable state every time, and calculating new battery impedance Rnew by averaging; meanwhile, according to the direct current internal resistance DCR when the internal resistance of the battery body is in a stable state every time, the battery impedance Rpr of the current service life is calculated by averaging.
It can be understood that, if the reliability K is less than the preset threshold 0.85, it indicates that the calculated direct-current internal resistance is not preferable when the internal resistance of the discharging battery is in a stable state every time, so that the discharging impedance life SOH of the battery in step S5 does not need to be recalculated, and the previous value is continuously maintained, thereby ensuring the accuracy and robustness of the measurement. Meanwhile, the direct current internal resistance of the discharged battery is calculated every time the internal resistance is in a stable state, a model and an estimation algorithm are not needed, and the calculation complexity is reduced.
In step S50, the battery discharge resistance life is calculated according to formula (5) in step S5, which is not described herein again.
In an embodiment of the invention, the method further comprises:
and according to the calculated SOC and temperature of the battery body discharged this time under the condition that the internal resistance is in a stable state every time, finding the internal resistance in the new battery impedance table and updating the internal resistance by using the corresponding direct current internal resistance to obtain a battery impedance table with the current service life, which is formed after the new battery impedance table is updated.
As shown in fig. 4, the system for estimating battery impedance life provided in the embodiment of the present invention includes a new battery impedance table constructing unit 110, a current life battery state online measuring unit 120, a current life battery impedance online calculating unit 130, a current life battery impedance calculating unit 140, and a current life battery discharging impedance life estimating unit 150; wherein the content of the first and second substances,
the new battery impedance table constructing unit 110 is configured to acquire the SOC, the temperature, and the internal resistance that change with the sampling period during battery discharging to construct a new battery impedance table before the battery is put into use;
the current-life battery state online measurement unit 120 is configured to, after the battery is put into use, acquire SOC, temperature, and battery state information that changes with a sampling period during the current discharging of the battery to detect an internal resistance steady state of the battery being discharged, and further acquire voltage, current, SOC, and temperature before and after the voltage drop is generated by the battery each time after the battery being discharged generates a corresponding voltage drop when the internal resistance is in the steady state each time;
the current-life battery state online calculation unit 130 is configured to calculate, according to the collected voltage, current, SOC, and temperature before and after voltage drop is generated by the battery each time, a direct-current internal resistance, SOC, and temperature of the battery being discharged at the time when the internal resistance is in a stable state each time;
the current-life battery impedance calculation unit 140 is configured to obtain a reliability by obtaining an acquisition time difference corresponding to a last discharge of the battery when the battery is discharged this time, find a corresponding internal resistance in the new battery impedance table according to the calculated SOC and temperature of the battery discharged this time in a stable state each time after it is determined that the reliability is greater than or equal to a preset threshold, and calculate a current-life battery impedance according to the calculated direct-current internal resistance of the battery discharged this time in the stable state each time;
the current-life battery discharge impedance life estimation unit 150 is configured to calculate the battery discharge impedance life according to the new battery impedance, the current-life battery impedance, and the internal resistance at the end of the battery life given by the manufacturer.
Wherein the reliability is determined by freshness and stability; wherein the content of the first and second substances,
the degree of confidence is equal to a product between the freshness and the degree of stability;
the freshness K1 is expressed by the formula K1 ═ a × e(-t/b)Calculating to obtain; wherein a and b are fixed constants and can be obtained by calibration according to the aging test data of the calendar life of the battery; t is the acquisition time difference between the current discharge of the battery and the last discharge of the battery;
the stability K2 is a constant 1.
Calculating the discharge impedance service life of the battery by using a formula SOH (Rpr-Rnew)/(Reol-Rnew); and the SOH is the battery discharge impedance life, the Rnew is the new battery impedance, the Rpr is the current life battery impedance, and the Reol is the internal resistance of the battery at the end of the life given by the manufacturer.
Wherein, still include: a current-life battery impedance online update unit 160; the present-life battery impedance online updating unit 160 is configured to find the internal resistance in the new battery impedance table according to the SOC and the temperature calculated when the internal resistance of the battery discharged this time is in the stable state each time, and update the internal resistance with the corresponding direct-current internal resistance, so as to obtain the present-life battery impedance table formed after the new battery impedance table is updated.
The embodiment of the invention has the following beneficial effects:
the method is used for directly measuring the impedance increase of the Battery based on the characteristic of the All-weather Battery (ACB) under the working condition of pulse generated by short-time heating, thereby realizing the direct measurement of the impedance life of the Battery, overcoming the problems existing in the existing online estimation of the impedance life of the Battery, and having better robustness and reliability.
It should be noted that, in the foregoing system embodiment, each included system unit is only divided according to functional logic, but is not limited to the above division as long as the corresponding function can be implemented; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.
It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by relevant hardware instructed by a program, and the program may be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (10)
1. A method for estimating battery impedance lifetime, the method comprising the steps of:
before the battery is put into use, the SOC, the temperature and the internal resistance which change along with the sampling period during the discharge of the battery are collected to construct a new battery impedance table;
after the battery is put into use, acquiring SOC, temperature and battery state information which change along with a sampling period when the battery is discharged at this time to detect the internal resistance stable state of the battery discharged at this time, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the battery discharged at this time generates corresponding voltage drop when the internal resistance is in the stable state each time;
calculating the direct current internal resistance, SOC and temperature of the battery discharging this time when the internal resistance is in a stable state every time according to the acquired voltage, current, SOC and temperature before and after the voltage drop of the battery is generated every time;
acquiring the acquisition time difference of the current discharge of the battery corresponding to the last discharge to obtain the reliability, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and temperature of the current discharge battery with the internal resistance in the stable state each time after the reliability is judged to be greater than or equal to the preset threshold, and calculating the current life battery impedance according to the calculated direct current internal resistance of the current discharge battery with the internal resistance in the stable state each time;
and calculating the discharge impedance life of the battery according to the new battery impedance, the current life battery impedance and the internal resistance given by the manufacturer when the battery life is finished.
2. The battery impedance lifetime estimation method of claim 1, wherein said confidence level is determined by freshness and stability; wherein the content of the first and second substances,
the degree of confidence is equal to a product between the freshness and the degree of stability;
the freshness K1 is expressed by the formula K1 ═ a × e(-t/b)Calculating to obtain; wherein a and b are fixed constants and can be obtained by calibration according to the aging test data of the calendar life of the battery; t is the acquisition time difference between the current discharge of the battery and the last discharge of the battery;
the stability K2 is a constant 1.
3. The battery impedance lifetime estimation method according to claim 1, wherein the step of collecting the SOC, the temperature and the battery state information that vary with the sampling period during the current discharging of the battery to detect the internal resistance steady state of the battery during the current discharging specifically comprises:
if the SOC acquired by the battery in the current sampling period is detected to be within a preset SOC range, the temperature is within a preset temperature range, and the battery state information simultaneously meets the conditions that the discharge current duration is greater than a preset time threshold, the discharge current variation value is smaller than a preset limit value in the discharge current duration, the varied discharge current is greater than a preset current threshold, the balance is not started and no fault exists, the internal resistance of the battery in the current sampling period is determined to be in a stable state; otherwise, determining that the internal resistance of the battery in the current sampling period is not in a stable state.
4. The battery impedance life estimation method of claim 3, wherein the preset SOC range is [ 40%, 60% ]; the preset temperature range is [25 ℃,40 ℃; the discharge current duration is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein, C is 100A.
5. The battery impedance lifetime estimation method of claim 1, wherein the battery discharge impedance lifetime is calculated by the formula SOH ═ (Rpr-Rnew)/(cool-Rnew); and the SOH is the battery discharge impedance life, the Rnew is the new battery impedance, the Rpr is the current life battery impedance, and the Reol is the internal resistance of the battery at the end of the life given by the manufacturer.
6. The on-line testing method for DC internal resistance of battery as claimed in claim 1, wherein the battery is an all-weather battery, and the all-weather battery comprises a battery body, a switch and a heating plate.
7. The battery impedance lifetime estimation method of claim 6, wherein said new battery impedance table is formed by collecting the SOC, temperature and internal resistance of the battery body of said all-weather battery, which change with the sampling period after the switch is turned off, when discharging before said all-weather battery is put into use.
8. The battery impedance lifetime estimation method according to claim 6, wherein each time the internal resistance stable state is based on said all-weather put into use, the SOC, temperature and battery state information of the battery body in the all-weather battery, which changes with the sampling period when the battery body is discharged after the switch is turned off, are collected to realize detection;
the voltage drop generated in each stable internal resistance state is generated when the switch of the all-weather battery is closed and the battery body and the heating sheet are electrically connected and conducted on the basis that the internal resistance is in the stable state each time.
9. The battery impedance life estimation method of claim 1, wherein the method further comprises:
and according to the calculated SOC and temperature of the battery discharged this time under the condition that the internal resistance is in a stable state every time, finding the internal resistance in the new battery impedance table and updating the internal resistance by using the corresponding direct current internal resistance to obtain a battery impedance table with the current service life, which is formed after the new battery impedance table is updated.
10. A battery impedance life estimation system is characterized by comprising a new battery impedance table construction unit, a current life battery state online measurement unit, a current life battery impedance online calculation unit, a current life battery impedance calculation unit and a current life battery discharge impedance life estimation unit; wherein the content of the first and second substances,
the new battery impedance meter constructing unit is used for acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery is discharged to construct a new battery impedance meter before the battery is put into use;
the current-life battery state online measuring unit is used for acquiring SOC, temperature and battery state information which change along with a sampling period when the battery is discharged at this time to detect the internal resistance stable state of the battery discharged at this time after the battery is put into use, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the battery discharged at this time generates corresponding voltage drop when the internal resistance is in the stable state;
the current-life battery state online calculation unit is used for calculating the direct-current internal resistance, SOC and temperature of the battery discharged at this time under the condition that the internal resistance is in a stable state every time according to the acquired voltage, current, SOC and temperature before and after the voltage drop is generated by the battery every time;
the current-life battery impedance calculation unit is used for acquiring the reliability of the battery by acquiring the acquisition time difference of the current discharge corresponding to the last discharge, finding the corresponding internal resistance in the new battery impedance table to calculate the new battery impedance according to the calculated SOC and temperature of the current discharge battery with the internal resistance in the stable state each time after the reliability is judged to be greater than or equal to the preset threshold value, and calculating the current-life battery impedance according to the calculated direct current internal resistance of the current discharge battery with the internal resistance in the stable state each time;
and the current-life battery discharge impedance life estimation unit is used for calculating the battery discharge impedance life according to the new battery impedance, the current-life battery impedance and the internal resistance given by the manufacturer when the battery life is finished.
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