CN113514771B - Battery impedance life estimation method and system - Google Patents
Battery impedance life estimation method and system Download PDFInfo
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- CN113514771B CN113514771B CN202010279581.2A CN202010279581A CN113514771B CN 113514771 B CN113514771 B CN 113514771B CN 202010279581 A CN202010279581 A CN 202010279581A CN 113514771 B CN113514771 B CN 113514771B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- 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]
- G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
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Abstract
The invention provides a battery impedance life estimation method, which comprises the steps of collecting SOC, temperature and internal resistance of battery discharge change to construct a new battery impedance meter before the battery is put into use; after the battery is put into use, collecting the current discharging SOC, temperature and battery state information of the battery to detect the stable state of the internal resistance of the battery, and collecting the voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time when the internal resistance of the battery is in the stable state; calculating the direct current internal resistance, the SOC and the temperature under each internal resistance stable state according to the collected voltage, current, the SOC and the temperature before and after the voltage drop; calculating the reliability, selecting the internal resistance in the new battery impedance table according to 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. By implementing the invention, on-line estimation is realized based on ACB technology, and the method 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 life of a battery.
Background
Battery impedance life, which can directly affect battery discharge power, is one of the core parameters characterizing battery performance and life. The capacity and the charge and discharge capacity of the battery can be stored, and the elicitation is attenuated along with the repetition of the battery pack until the use requirement cannot be met. Therefore, battery impedance life is often examined and reflected in terms of internal resistance decay of the electrical ground. However, the existing electric/hybrid power battery utilizes a model and an online estimation method to measure the battery impedance life, 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 existing in the existing online estimation of battery impedance lifetime, and has better robustness and reliability.
Disclosure of Invention
The technical problem to be solved by the embodiment of the invention is to provide a Battery impedance life estimation method and system, which are used for directly measuring the Battery impedance growth based on the characteristic of pulse working conditions generated by All-weather Battery (All-Climate-Battery, ACB) short-time heating, so that the direct measurement of the Battery impedance life is realized, the problems existing in the existing Battery impedance life online estimation can be overcome, and the method and system have better robustness and reliability.
In order to solve the above technical problems, an embodiment of the present invention provides a battery impedance lifetime estimation method, including the steps of:
Before the battery is put into use, acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery discharges 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 steady state of the discharged battery, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the discharged battery is generated each time after the discharged battery generates corresponding voltage drop when the internal resistance of the discharged battery is in the steady state each time;
According to the collected voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time, calculating the direct current internal resistance, SOC and temperature of the discharging battery in a stable state each time;
Acquiring the acquisition time difference of the current discharge of the battery corresponding to the last discharge to obtain the reliability, and after the reliability is judged to be greater than or equal to a preset threshold value, calculating the impedance of the new battery according to the calculated SOC and temperature of the current discharge battery in a stable state of each internal resistance, finding the corresponding internal resistance in the impedance table of the new battery, and calculating the impedance of the battery with the current service life according to the calculated direct current internal resistance of the current discharge battery in the stable state of each internal resistance;
And calculating the battery discharge impedance life according to the new battery impedance, the current life battery impedance and the internal resistance of the battery at the end of the life given by a manufacturer.
Wherein the credibility is determined by freshness and stability; wherein,
The confidence level is equal to a product between the freshness level and the stability level;
The freshness K1 is calculated by the formula k1=a×e (-t/b); wherein a and b are fixed constants, and can be calibrated according to battery calendar life aging test data; 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.
The step of detecting the internal resistance stable state of the discharging battery by collecting the SOC, the temperature and the battery state information which change along with the sampling period when the discharging battery is discharged at this time specifically comprises the following steps:
If the SOC acquired by the battery in the current sampling period is detected to be in a preset SOC range, the temperature is in a preset temperature range, the battery state information simultaneously meets the conditions that the discharge current duration is larger than a preset time threshold value, the discharge current change value is smaller than a preset limit value in the discharge current duration, and the changed discharge current is larger than the preset current threshold value, and the battery is balanced and is not started and has no fault, 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 duration of the discharge current is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein c=100deg.A.
Wherein, the battery discharge impedance life is calculated by the formula SOH= (Rpr-Rnew)/(Reol-Rnew); wherein SOH is the battery discharge resistance life, rnew is the new battery resistance, rpr is the current life battery resistance, reol is the internal resistance at the end of the battery 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 plate.
The new battery impedance meter is formed by collecting the SOC, the temperature and the internal resistance which change along with a sampling period when the battery body in the all-weather battery discharges after the switch is disconnected before the all-weather battery is put into use.
The method comprises the steps of detecting the internal resistance of an all-weather battery, wherein each internal resistance stable state is based on SOC, temperature and battery state information which change along with a sampling period when a battery body in the all-weather battery discharges after a switch is disconnected after the all-weather battery is put into use;
the voltage drop generated in each internal resistance steady state is based on the switch closing of the all-weather battery in each internal resistance steady state, so that the battery body and the heating plate are electrically connected and conducted.
Wherein the method further comprises:
and finding the internal resistance in the new battery impedance table according to the calculated SOC and the calculated temperature of the current discharge battery in the state that the internal resistance is stable each time, and updating the new battery impedance table by using the corresponding direct current internal resistance to obtain a current life battery impedance table formed after updating the new battery impedance table.
The embodiment of the invention also provides a battery impedance life estimation system, which comprises 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 new battery impedance table construction unit is used for acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery discharges before the battery is put into use to construct a new battery impedance table;
the on-line measurement unit for the current life battery state is used for collecting the SOC, the temperature and the battery state information which change along with the sampling period when the battery is discharged at this time to detect the internal resistance steady state of the battery at this time, and further collecting the voltage, the current, the SOC and the temperature before and after the voltage drop of the battery is generated each time after the battery at this time generates corresponding voltage drop when the internal resistance of the battery at this time is in the steady state;
the current life battery state online calculating unit is used for calculating the direct current internal resistance, the SOC and the temperature of the discharging battery in a stable state each time according to the collected voltage, current, the SOC and the temperature before and after the voltage drop of the battery is generated each time;
The current life battery impedance calculating unit is configured to obtain a reliability by acquiring an acquisition time difference of the current discharge of the battery corresponding to the last discharge, and calculate a new battery impedance according to the calculated SOC and temperature of the current discharge battery in a steady state of each internal resistance after the reliability is determined to be greater than or equal to a preset threshold, and calculate a current life battery impedance according to the calculated dc internal resistance of the current discharge battery in a steady state of each internal resistance;
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 of the battery at the end of the life given by a manufacturer.
The embodiment of the invention has the following beneficial effects:
The invention directly measures the impedance increase of the Battery based on the characteristic of pulse working condition generated by All-weather Battery (All-Climate-Battery, ACB) short-time heating, thereby realizing the direct measurement of the impedance life of the Battery, overcoming the problems existing in the online estimation of the impedance life of the existing Battery and having better robustness and reliability.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that it is within the scope of the invention to one skilled in the art to obtain other drawings from these drawings without inventive faculty.
FIG. 1 is a flowchart of a method for estimating battery impedance lifetime according to an embodiment of the present invention;
FIG. 2 is a flowchart of a battery impedance lifetime estimation method applied to an all-weather battery according to an embodiment of the present invention;
FIG. 3 is an application scenario diagram 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
The present invention will be described in further detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent.
As shown in fig. 1, in an embodiment of the present invention, a method for estimating a battery impedance lifetime is provided, including the following steps:
step S1, before the battery is put into use, acquiring the SOC, the temperature and the internal resistance which change along with a sampling period when the battery discharges to construct a new battery impedance table;
Step S2, 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 steady state of the discharged battery, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the discharged battery generates corresponding voltage drop when the internal resistance of the discharged battery is in the steady state each time;
Step S3, calculating the direct current internal resistance, the SOC and the temperature of the discharge battery in a stable state according to the collected voltage, current, the SOC and the temperature before and after the voltage drop of the battery is generated each time;
Step S4, acquiring the acquisition time difference of the last discharge corresponding to the current discharge of the battery to obtain the reliability, and after the reliability is judged to be greater than or equal to a preset threshold value, calculating the impedance of the new battery according to the calculated SOC and temperature of the current discharge battery in a stable state of each internal resistance, finding the corresponding internal resistance in the impedance table of the new battery, and calculating the impedance of the battery with the current service life according to the calculated direct current internal resistance of the current discharge battery in the stable state of each internal resistance;
And S5, calculating the discharge impedance life of the battery according to the new battery impedance, the current life battery impedance and the internal resistance of the battery at the end of the life given by a manufacturer.
Specifically, in step S1, the laboratory device is used to measure the internal resistances of the new battery at different SOCs and temperatures during discharge, and store a new battery impedance table Tnew (which is used as an evaluation reference for the whole life cycle of the battery and is always kept unchanged) in which the new battery impedance table Tnew is a relational table formed by correlating the SOCs, temperatures and internal resistances of the new battery that change with the sampling period during discharge.
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 the sampling periods are arranged at intervals of 5s and 10s or randomly; for another example, each sampling period is set by SOC in a decreasing rule of 5%; as another example, each sampling period is set with an increasing rule of 1 ℃ per rise in 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.), firstly, the SOC, temperature and battery status information of the battery, which change with each sampling period in the current discharging state of the battery, are collected by the battery management system; the battery state information includes, but is not limited to, discharge current duration, discharge current magnitude, equalization state, and fault state, among others. It should be noted that the current discharge of the battery can be distinguished from the last discharge and the next discharge by a mark, and the time difference between the adjacent two discharge measurements, i.e. the acquisition time difference, is calculated by the start 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 is discharged this time, and the specific steps are as follows:
If the battery management system detects that the SOC acquired by the battery in the current sampling period is in a preset SOC range (such as [40%,60% ]), the temperature is in a preset temperature range (such as [25 ℃,40 ℃), the battery state information simultaneously satisfies that the discharge current duration is greater than a preset time threshold (such as 60 s), the discharge current variation value is smaller than a preset limit value (such as 5A) and the varied discharge current is greater than a preset current threshold (such as 0.8C, C=100A) within the discharge current duration (such as 60 s), and the battery internal resistance in the current sampling period is determined to be in a stable state if balance is not opened and no fault exists; otherwise, 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 (for example >60% or < 40%), the temperature exceeds a preset temperature range (for example >40 ℃ or <25 ℃), the duration of the discharge current in the battery state information is less than or equal to a preset time threshold (for example <60 seconds), or the variation value of the discharge current in the duration of the discharge current (for example 60 seconds) is greater than or equal to a preset limit value (for example > 5A) and the variation discharge current is less than or equal to a preset current threshold (for example 0.6c <0.8 c), and at least one of balanced opening and presence of a fault is determined that the internal resistance of the battery in the current sampling period is not in a stable state. In one embodiment, the preset SOC range is [40%,60% ]; the preset temperature range is [25 ℃,40 ℃; the duration of the discharge current is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein c=100deg.A.
It is understood that the conditions for identifying the steady state of the battery dc internal resistance can be evaluated according to the conditions of voltage, current, temperature discharge time, etc., 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 every time, and records the current (Ib & Ia), the voltage (Vb & Va), the battery core electric quantity (SOCb & SOCa) and the temperature (Tb & Ta) before and after the voltage drop pulse of the battery every time.
It should be noted that the direct current internal resistance of the battery shows nonlinear change along with the temperature and the state of the SOC, and the internal resistance of the battery has large change in the upper limit and the lower limit of the SOC and the upper limit and the lower limit of the temperature range, and the accuracy of online measurement of the internal resistance is poor, so that the steady state interval of the internal resistance of the battery can be calibrated through experiments, and the steady interval is selected for online internal resistance estimation, so that the accuracy can be improved.
In step S3, according to formula (1), the dc internal resistance DCR of the present discharge battery in each time the internal resistance is in a stable state is calculated;
DCR＝(Vb-Va)/(Ib-Ia) (1)：
According to the formula (2), calculating the SOC of the discharging battery under the condition that the internal resistance is in a stable state each time;
SOC＝(SOCb+SOCa)/2 (2)；
And (3) calculating the temperature T of the discharge battery in a stable state every time the internal resistance of the discharge battery is calculated 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 between the freshness level K1 and the stability level K2, i.e., k=k1×k2, where K has a value range of [0,1], and the closer the K value is to 1, the higher the confidence level.
Wherein, the freshness K1 is calculated by the formula (4):
K1＝a*e(-t/b) (4)；
Wherein a and b are fixed constants, and can be calibrated according to battery calendar life aging test data; 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 because the internal resistance is not in the steady state k2=0.
Secondly, if the reliability K > = a preset threshold value of 0.85 is judged, according to the SOC and the temperature calculated when the internal resistance of the discharging battery is in a stable state each time, the corresponding internal resistance is found in a new battery impedance table Tnew, and the new battery impedance Rnew is calculated by averaging; meanwhile, according to the DC internal resistance DCR when the internal resistance of the discharging battery is in a stable state every time, the current service life battery impedance Rpr is calculated through averaging.
It can be understood that if the reliability K is less than the preset threshold value 0.85, it is indicated that the calculated dc internal resistance is not preferable each time the internal resistance of the discharged battery is in a stable state, so that the battery discharge impedance life SOH in step S5 does not need to be recalculated, and the previous value is continuously maintained, thereby ensuring the accuracy and robustness of measurement. Meanwhile, the direct current internal resistance calculation is carried out when the internal resistance of the discharge battery is in a stable state every time, 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 formula (5);
SOH＝(Rpr-Rnew)/(Reol-Rnew) (5)；
SOH is the battery discharge resistance life, reol is the internal resistance at the end of the battery life given by the manufacturer.
In an embodiment of the present invention, the method further includes:
and finding the internal resistance in the new battery impedance table according to the calculated SOC and the calculated temperature of the current discharge battery in the state that the internal resistance is stable each time, and updating the new battery impedance table by using the corresponding direct current internal resistance to obtain a current life battery impedance table formed after updating the new battery impedance table.
As shown in 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, a method for estimating the impedance lifetime of a battery according to an embodiment of the present invention comprises the following steps:
step S10, before the all-weather battery is put into use, acquiring the SOC, the temperature and the internal resistance of the battery body in the all-weather battery, which change along with a sampling period when the battery body discharges after a switch is disconnected, so as to construct a new battery impedance table;
Step S20, after the all-weather battery is put into use, acquiring SOC, temperature and battery state information which change along with a sampling period when the battery body in the all-weather battery is discharged this time after a switch is disconnected to detect the internal resistance steady state of the discharged battery body, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the battery body is generated each time after the discharged battery body generates corresponding voltage drop when the internal resistance of the discharged battery body is in the steady state each time;
Step S30, calculating the direct current internal resistance, the SOC and the temperature of the discharging battery body in a stable state each time according to the collected voltage, current, the SOC and the temperature before and after the voltage drop of the battery body each time;
Step S40, acquiring acquisition time difference of the last discharge of the battery body to obtain reliability, and after the reliability is judged to be greater than or equal to a preset threshold value, finding out corresponding internal resistance in the new battery impedance table to calculate new battery impedance according to the calculated SOC and temperature of the current discharge battery body in a stable state of each internal resistance, and calculating the current life battery impedance according to the calculated direct current internal resistance of the current discharge battery body in the stable state of each internal resistance;
And S50, calculating the discharge impedance life of the battery according to the new battery impedance, the current life battery impedance and the internal resistance of the battery at the end of the life given by a manufacturer.
In step S10, the laboratory device is used to measure the internal resistances of the battery body in the new all-weather battery at different SOCs and temperatures when the battery body discharges after the switch is turned off, and store a new battery impedance table Tnew (as an evaluation reference of the whole life cycle of the battery, which is always kept unchanged), wherein the new battery impedance table Tnew is a relational table formed by correlating the SOCs, the temperatures and the internal resistances of the battery body in the new all-weather battery, which change with each sampling period when the battery body discharges after the switch is turned off. It is understood that the sampling period setting in the present step S10 is the same as the sampling period setting in the step S1, and will not be described herein.
In step S20, after the all-weather battery has been put into use for a period of time (e.g. 1 and 1 year, etc.), the battery management system collects the SOC, temperature and battery status information of the battery body in the all-weather battery, which change with each sampling period when the battery body is discharged this time after the switch is turned off; the battery state information includes, but is not limited to, discharge current duration, discharge current magnitude, equalization state, and fault state, among others. It should be noted that the current discharge of the battery body can be distinguished from the last discharge and the next discharge by the mark, and the time difference between the adjacent two discharge measurements, namely 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 is discharged after the switch is disconnected, and the specific steps are as follows:
If the battery management system detects that the SOC acquired by the battery body in the current sampling period is in a preset SOC range (such as [40%,60% ]), the temperature is in a preset temperature range (such as [25 ℃,40 ℃), the battery state information simultaneously satisfies that the discharge current duration is greater than a preset time threshold (such as 60 s), the discharge current variation value is smaller than a preset limit value (such as 5A) and the varied discharge current is greater than a preset current threshold (such as 0.8C, C=100A) within the discharge current duration (such as 60 s), and the battery internal resistance in the current sampling period is determined to be in a stable state if balance is unopened and no fault exists; otherwise, 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 of the battery body acquired in the current sampling period exceeds a preset SOC range (for example, >60% or < 40%), and the temperature exceeds a preset temperature range (for example, >40 ℃ or <25 ℃), in the battery state information, the discharge current duration is less than or equal to a preset time threshold (for example <60 seconds), or the discharge current variation value in the discharge current duration (for example, 60 seconds) is greater than or equal to a preset limit value (for example, > 5A) and the varied discharge current is less than or equal to a preset current threshold (for example, 0.6c <0.8 c), and at least one of balanced opening and presence of faults 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 preset SOC range is [40%,60% ]; the preset temperature range is [25 ℃,40 ℃; the duration of the discharge current is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein c=100deg.A.
Then, when the internal resistance of the discharging battery body is in a stable state every time, the battery management system controls the switch in the all-weather battery to be closed so as to realize the electric connection between the battery body and the heating plate to enable the battery body to generate voltage drop, so that the voltage, current, SOC and temperature before and after the voltage drop of the discharging battery body every time can be collected, namely, high-power pulse is generated by using the all-weather battery ACB technology, and the current (Ib & Ia), the voltage (Vb & Va), the electric quantity of the battery core (SOCb & SOCa) and the temperature (Tb & Ta) before and after the voltage drop pulse of the battery body every 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 internal resistance stable state, a 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 lower than 0.8C and the pulse duration is not lower than 10s.
And finally, immediately disconnecting the switch after the voltage, the current, the SOC and the temperature before and after each voltage drop are acquired when the internal resistance of the discharging battery body is in a stable state, so that the battery body is in a discharging state, and SOC, temperature and battery state information changed in the next sampling period can be acquired again, and the battery body can meet the condition of the stable state of the internal resistance in a plurality of sampling periods, thereby conditionally obtaining the current (Ib & Ia), the voltage (Vb & Va), the SOC (SOCb & SOCa) and the temperature (Tb & Ta) before and after voltage drop pulses are generated by a plurality of groups of batteries. In one embodiment, the SOC is within the SOC range of [40%,60% ] and a plurality of SOC values, such as 55%,50%,45%,40%, the temperature is within the preset temperature range of [25 ℃,40 ℃), the battery status information simultaneously satisfies that the discharge current duration is greater than the preset time threshold 60s and the discharge current variation value is less than the preset limit 5A and the varied discharge current is greater than the preset current threshold 0.8C within the discharge current duration 60s, the equalization is not opened and there is no fault. It can be understood that the switch can be immediately disconnected after the voltage, the current, the SOC and the temperature are collected before and after the voltage drop generated by the battery body when the internal resistance is in a stable state each time, so as to avoid the problem of data measurement errors caused by the loss of the battery by the heating plate.
In step S30, according to formulas (1) to (3) in step S3, the dc internal resistance DCR, SOC and temperature T of the current discharge battery body in each time the internal resistance is in a stable state are calculated, and are not described herein.
In step S40, firstly, the confidence level K is calculated according to the formula (4) and the related conditions in step S4, and the related contents in step S4 are specifically referred to herein and are not described in detail.
Secondly, if the reliability K > = a preset threshold value of 0.85 is judged, according to the SOC and the temperature calculated when the internal resistance of the discharging battery body is in a stable state each time, the corresponding internal resistance is found in a new battery impedance table Tnew, and the new battery impedance Rnew is calculated by averaging; meanwhile, according to the DC internal resistance DCR of the discharging battery body when the internal resistance is in a stable state every time, the current service life battery impedance Rpr is calculated through averaging.
It can be understood that if the reliability K is less than the preset threshold value 0.85, it is indicated that the calculated dc internal resistance is not preferable each time the internal resistance of the discharged battery is in a stable state, so that the battery discharge impedance life SOH in step S5 does not need to be recalculated, and the previous value is continuously maintained, thereby ensuring the accuracy and robustness of measurement. Meanwhile, the direct current internal resistance calculation is carried out when the internal resistance of the discharge battery is in a stable state every time, a model and an estimation algorithm are not needed, and the calculation complexity is reduced.
In step S50, the battery discharge impedance lifetime is calculated according to the formula (5) in step S5, which is not described herein.
In an embodiment of the present invention, the method further includes:
And finding the internal resistance in the new battery impedance table according to the calculated SOC and the calculated temperature of the current discharging battery body under the state that the internal resistance is stable every time, and updating the new battery impedance table by using the corresponding direct current internal resistance to obtain a current life battery impedance table formed after updating the new battery impedance table.
As shown in fig. 4, in an embodiment of the present invention, a battery impedance lifetime estimation system is provided, which includes a new battery impedance table construction unit 110, a current lifetime battery state online measurement unit 120, a current lifetime battery impedance online calculation unit 130, a current lifetime battery impedance calculation unit 140, and a current lifetime battery discharge impedance lifetime estimation unit 150; wherein,
The new battery impedance table construction unit 110 is configured to collect SOC, temperature and internal resistance, which change along with a sampling period when the battery is discharged, 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 collect SOC, temperature and battery state information that change along with a sampling period when the battery is currently discharged after the battery is put into use, detect an internal resistance steady state of the currently discharged battery, and further collect voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time after the current discharged battery generates a corresponding voltage drop when the internal resistance is in a steady state each time;
the on-line calculation unit 130 for calculating the dc internal resistance, SOC and temperature of the discharging battery in a stable state according to the collected voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time;
The current life battery impedance calculating unit 140 is configured to obtain a reliability by acquiring an acquisition time difference of the current discharge of the battery corresponding to the last discharge, and after the reliability is determined to be greater than or equal to a preset threshold, calculate a new battery impedance according to the calculated SOC and temperature of the current discharge battery in a steady state of each internal resistance, find a corresponding internal resistance in the new battery impedance table, and calculate a current life battery impedance according to the calculated dc internal resistance of the current discharge battery in a steady state of each internal resistance;
The current life battery discharge impedance life estimation unit 150 is configured to calculate a 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 credibility is determined by freshness and stability; wherein,
The confidence level is equal to a product between the freshness level and the stability level;
The freshness K1 is calculated by the formula k1=a×e (-t/b); wherein a and b are fixed constants, and can be calibrated according to battery calendar life aging test data; 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.
Wherein, the battery discharge impedance life is calculated by the formula SOH= (Rpr-Rnew)/(Reol-Rnew); wherein SOH is the battery discharge resistance life, rnew is the new battery resistance, rpr is the current life battery resistance, reol is the internal resistance at the end of the battery life given by the manufacturer.
Wherein, still include: a current lifetime battery impedance online updating unit 160; the current life battery impedance online updating unit 160 is configured to find an internal resistance in the new battery impedance table according to the SOC and the temperature calculated when the internal resistance of the current discharge battery is in a stable state each time, and update the internal resistance with a corresponding dc internal resistance, so as to obtain a current life battery impedance table formed after the new battery impedance table is updated.
The embodiment of the invention has the following beneficial effects:
The invention directly measures the impedance increase of the Battery based on the characteristic of pulse working condition generated by All-weather Battery (All-Climate-Battery, ACB) short-time heating, thereby realizing the direct measurement of the impedance life of the Battery, overcoming the problems existing in the online estimation of the impedance life of the existing Battery and having better robustness and reliability.
It should be noted that, in the above system embodiment, each included system unit is only divided according to the functional logic, but not limited to the above division, so long as the corresponding function can be implemented; in addition, the specific names of the functional units are also only for distinguishing from each other, and are not used to limit the protection scope of the present invention.
Those of ordinary skill in the art will appreciate that all or a portion of the steps in implementing the methods of the above embodiments may be implemented by a program to instruct related hardware, where the program may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc.
The foregoing disclosure is illustrative of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (9)
1. A method for estimating battery impedance life, the method comprising the steps of:
Before the battery is put into use, acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery discharges 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 steady state of the discharged battery, and further acquiring voltage, current, SOC and temperature before and after the voltage drop of the discharged battery is generated each time after the discharged battery generates corresponding voltage drop when the internal resistance of the discharged battery is in the steady state each time;
According to the collected voltage, current, SOC and temperature before and after the voltage drop of the battery is generated each time, calculating the direct current internal resistance, SOC and temperature of the discharging battery in a stable state each time;
Acquiring the acquisition time difference of the current discharge of the battery corresponding to the last discharge to obtain the reliability, and after the reliability is judged to be greater than or equal to a preset threshold value, calculating the impedance of the new battery according to the calculated SOC and temperature of the current discharge battery in a stable state of each internal resistance, finding the corresponding internal resistance in the impedance table of the new battery, and calculating the impedance of the battery with the current service life according to the calculated direct current internal resistance of the current discharge battery in the stable state of each internal resistance;
calculating the battery discharge impedance life according to the new battery impedance, the current life battery impedance and the internal resistance of the battery at the end of the life given by a manufacturer;
The credibility is determined by freshness and stability; wherein,
The confidence level is equal to a product between the freshness level and the stability level;
The freshness K1 is calculated by a formula K1=a×e (-t/b); wherein a and b are fixed constants, and can be calibrated according to battery calendar life aging test data; 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.
2. The method for estimating the impedance life of a battery according to claim 1, wherein the step of collecting information of SOC, temperature and battery state of the battery, which are changed with a sampling period, at the time of the current discharge to detect the steady state of the internal resistance of the battery at the current discharge, specifically comprises:
If the SOC acquired by the battery in the current sampling period is detected to be in a preset SOC range, the temperature is in a preset temperature range, the battery state information simultaneously meets the conditions that the discharge current duration is larger than a preset time threshold value, the discharge current change value is smaller than a preset limit value in the discharge current duration, and the changed discharge current is larger than the preset current threshold value, and the battery is balanced and is not started and has no fault, 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.
3. The battery impedance life estimation method according to claim 2, wherein the preset SOC range is [40%,60% ]; the preset temperature range is [25 ℃,40 ℃; the duration of the discharge current is 60s, the preset limit value is 5A, and the preset current threshold value is 0.8C; wherein c=100deg.A.
4. The battery impedance life estimation method according to claim 1, wherein the battery discharge impedance life is calculated by the formula soh= (Rpr-Rnew)/(Reol-Rnew); wherein SOH is the battery discharge resistance life, rnew is the new battery resistance, rpr is the current life battery resistance, reol is the internal resistance at the end of the battery life given by the manufacturer.
5. The method of 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.
6. The battery impedance life estimation method according to claim 5, wherein the new battery impedance table is formed based on the SOC, temperature and internal resistance of the battery body in the all-weather battery, which change with the sampling period when the battery body discharges after the switch is turned off, before the all-weather battery is put into use.
7. The method for estimating the impedance life of a battery according to claim 5, wherein each time the internal resistance steady state is detected based on the SOC, temperature and battery state information which are changed along with a sampling period when the battery body in the all-weather battery discharges after the switch is turned off after the all-weather battery is put into use;
the voltage drop generated in each internal resistance steady state is based on the switch closing of the all-weather battery in each internal resistance steady state, so that the battery body and the heating plate are electrically connected and conducted.
8. The battery impedance life estimation method according to claim 1, wherein the method further comprises:
and finding the internal resistance in the new battery impedance table according to the calculated SOC and the calculated temperature of the current discharge battery in the state that the internal resistance is stable each time, and updating the new battery impedance table by using the corresponding direct current internal resistance to obtain a current life battery impedance table formed after updating the new battery impedance table.
9. The 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 new battery impedance table construction unit is used for acquiring the SOC, the temperature and the internal resistance which change along with the sampling period when the battery discharges before the battery is put into use to construct a new battery impedance table;
the on-line measurement unit for the current life battery state is used for collecting the SOC, the temperature and the battery state information which change along with the sampling period when the battery is discharged at this time to detect the internal resistance steady state of the battery at this time, and further collecting the voltage, the current, the SOC and the temperature before and after the voltage drop of the battery is generated each time after the battery at this time generates corresponding voltage drop when the internal resistance of the battery at this time is in the steady state;
the current life battery state online calculating unit is used for calculating the direct current internal resistance, the SOC and the temperature of the discharging battery in a stable state each time according to the collected voltage, current, the SOC and the temperature before and after the voltage drop of the battery is generated each time;
The current life battery impedance calculating unit is configured to obtain a reliability by acquiring an acquisition time difference of the current discharge of the battery corresponding to the last discharge, and calculate a new battery impedance according to the calculated SOC and temperature of the current discharge battery in a steady state of each internal resistance after the reliability is determined to be greater than or equal to a preset threshold, and calculate a current life battery impedance according to the calculated dc internal resistance of the current discharge battery in a steady state of each internal resistance;
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 of the battery at the end of the life given by a manufacturer;
The credibility is determined by freshness and stability; wherein,
The confidence level is equal to a product between the freshness level and the stability level;
The freshness K1 is calculated by a formula K1=a×e (-t/b); wherein a and b are fixed constants, and can be calibrated according to battery calendar life aging test data; 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.
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