CN113933733A - Lead-acid battery health degree evaluation method - Google Patents
Lead-acid battery health degree evaluation method Download PDFInfo
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- G01—MEASURING; TESTING
- 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]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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Abstract
A lead-acid battery health assessment method comprises the following steps: selecting a battery with the same equivalent circuit model as the battery to be tested as a standard battery; acquiring reference discharge capacity and reference alternating current impedance data of the standard battery at different service life stages; measuring and calculating the reference element parameters in the equivalent circuit corresponding to the standard battery according to the reference alternating-current impedance data; establishing a corresponding relation between the battery health degree of the standard battery and the reference element parameters; acquiring alternating current impedance data of a battery to be tested; measuring and calculating element parameters in an equivalent circuit corresponding to the battery to be measured according to the alternating current impedance data; and determining the battery health degree of the battery to be tested according to the element parameters and the corresponding relation between the battery health degree SOH of the standard battery and the reference element parameters. The method can measure and calculate the capacity retention rate of the lead-acid battery.
Description
Technical Field
The invention relates to the technical field of lead-acid battery performance evaluation, in particular to a method for evaluating the health degree of a lead-acid battery.
Background
The storage battery is used as indispensable equipment in a direct current system, is widely applied in a transformer substation, is important equipment for ensuring reliable operation of a communication network of the transformer substation, and must ensure that a lead-acid battery is in a good health state under the condition. The health state of the lead-acid battery in actual operation is influenced by various factors, the corrosion speed of positive and negative plates of the storage battery can be accelerated when the ambient temperature rises during the operation of the battery, and meanwhile, the electrolyte is dried up due to the rise of the temperature, so that the cycle life of the storage battery is shortened; the storage battery can cause the passivation of the positive electrode when being in a floating charge state for a long time, the internal resistance of the battery is increased, and the corrosion of a grid plate can be accelerated by the oxygen evolution reaction of the positive electrode; in addition, if the alternating current power supply stops supplying power under extreme conditions, the storage battery is used as the only power supply of the direct current load of the transformer substation, over-discharge is easy to occur, a large amount of lead sulfate is accumulated on the surface of the negative electrode of the battery, the internal resistance of the battery is increased due to more lead sulfate, and the discharge performance is deteriorated accordingly. Therefore, the normal operation of the storage battery is influenced by the action of various factors, and meanwhile, the health state of the storage battery is quickly and reliably detected, and it is very important to timely inform maintenance personnel of overhauling on time.
SOH is defined as the ratio of the maximum capacity to the nominal capacity of the battery, and represents the capacity retention rate of the battery. The SOH of the battery is estimated by combining voltage, current and resistance through an algorithm in the existing SOH estimation method, A.Delaile and the like find that the phenomenon of 'coupled de queue' can occur in the discharge of the battery in a full-power state, and the SOH of the battery is estimated by monitoring the voltage change rate in the process. Mchrnoosh Shahriari indicates that the slope of the open circuit voltage change curve varies significantly at different SOHs, but this characteristic is not significant for batteries containing a large number of cells and under a variety of operating conditions.
Disclosure of Invention
The invention aims to provide a lead-acid battery health degree evaluation method for measuring and calculating the battery health degree of a lead-acid battery.
The technical scheme of the invention is as follows:
a lead-acid battery health degree evaluation method comprises the following steps:
selecting a battery with the same equivalent circuit model as the battery to be tested as a standard battery;
acquiring reference discharge capacity and reference alternating current impedance data of the standard battery at different service life stages; measuring and calculating the reference element parameters in the equivalent circuit corresponding to the standard battery according to the reference alternating-current impedance data; establishing a corresponding relation between the battery health degree of the standard battery and the reference element parameters;
acquiring alternating current impedance data of a battery to be tested; measuring and calculating element parameters in an equivalent circuit corresponding to the battery to be measured according to the alternating current impedance data;
and inquiring the corresponding relation between the battery health degree SOH of the standard battery and the reference element parameter according to the element parameter, and determining the battery health degree of the battery to be tested.
Preferably, the method for acquiring the reference discharge capacity and the reference ac impedance data of the standard battery at different life stages is as follows: selecting an unused battery as a standard battery, processing the unused battery by using a large-current accelerated charge-discharge cycle life test, and after the unused battery is sufficiently silenced, enabling the standard battery to be in different life stages; and at any service life stage of the standard battery, after the standard battery is fully charged, performing constant current discharge on the standard battery, and measuring and calculating the reference discharge capacity and reference alternating current impedance data of the standard battery at the service life stage.
Further, the constant current discharge method is to discharge the battery to the cut-off voltage of the battery with a current of 1C.
Preferably, the equivalent circuit model is a Thevenin equivalent circuit model, and the reference element parameter and the element parameter are ohmic internal resistance R0。
Further, the method for establishing the corresponding relationship between the health state of the standard battery and the reference element parameter is as follows: at any service life stage of the standard battery, measuring the alternating current impedance of the standard battery in the excitation frequency range of 20Hz-300Hz, and converting the alternating current impedance data into ohmic internal resistance R0The method comprises the following steps: the constant ε is chosen to be 10-4In the frequency range of 20Hz-300Hz, as the imaginary part Z of the AC impedance dataImSatisfy | ZImIf | < epsilon, the AC impedance data is equal to the ohmic internal resistance R0；
Normalizing the discharge capacity of the standard battery at any service life stage and recording the discharge capacity as C*Non-linearly fitting the ohmic internal resistance R0And 1-C*To obtain the ohmic internal resistance R0And the SOH of the battery.
Preferably, SOH is 1.26 to 0.6 xr0+0.28×R0 2In the formula, SOH is the battery health degree, R0Is the ohmic internal resistance.
The invention has the beneficial effects that:
1. the life-span of lead acid battery receives the influence of many-sided factor, and the battery can suffer operating environment high temperature, overdischarge, be in for a long time the condition such as float charge state, and ambient temperature rising will aggravate the battery just, the corruption condition of negative plate for the polar plate sulfation is serious, is in the float charge state for a long time and can cause the passivation of battery positive plate, increases the internal resistance of battery, and a large amount of lead sulfate can be adsorbed to the battery negative pole during overdischarge, causes the internal resistance of battery to increase, and discharge performance worsens gradually. Therefore, when the health degree of the lead-acid battery is evaluated based on the alternating-current impedance, the defects and the shortcomings in the prior art can be overcome, and the SOH level of the health degree of the battery can be reflected by the change of the alternating-current impedance value under the influence of various factors, so that a maintainer can be helped to quickly select the battery with poor capacity retention rate as much as possible, and the potential safety hazard is avoided.
Drawings
Fig. 1 is a flow chart of a method for evaluating the health of a lead-acid battery based on alternating-current impedance.
Fig. 2 is a conventional equivalent circuit model of a lead-acid battery Thevenin.
Fig. 3 is a schematic diagram of a method for establishing a correlation between equivalent element parameters and battery health.
FIG. 4 is a schematic diagram of the AC impedance of a lead acid battery during charging at different SOH.
Detailed Description
The present invention is described below in terms of embodiments in conjunction with the accompanying drawings to assist those skilled in the art in understanding and implementing the present invention. Unless otherwise indicated, the following embodiments and technical terms therein should not be understood to depart from the background of the technical knowledge in the technical field.
The storage battery is used as indispensable equipment in a direct current system, is widely applied in a transformer substation, is important equipment for ensuring reliable operation of a communication network of the transformer substation, and must ensure that a lead-acid battery is in a good health state under the condition. The health state of the lead-acid battery in actual operation is influenced by various factors, the corrosion speed of positive and negative plates of the storage battery can be accelerated when the ambient temperature rises during the operation of the battery, and meanwhile, the electrolyte is dried up due to the rise of the temperature, so that the cycle life of the storage battery is shortened; the storage battery can cause the passivation of the positive electrode when being in a floating charge state for a long time, the internal resistance of the battery is increased, and the corrosion of a grid plate can be accelerated by the oxygen evolution reaction of the positive electrode; in addition, if the alternating current power supply stops supplying power under extreme conditions, the storage battery is used as the only power supply of the direct current load of the transformer substation, over-discharge is easy to occur, a large amount of lead sulfate is accumulated on the surface of the negative electrode of the battery, the internal resistance of the battery is increased due to more lead sulfate, and the discharge performance is deteriorated accordingly. SOH is defined as the ratio of the maximum capacity to the nominal capacity of the battery, and represents the capacity retention rate of the battery. The existing SOH estimation method estimates the SOH of the battery jointly through voltage, current and resistance by using an algorithm, the phenomenon of 'coupled de queue' can occur when the battery is discharged in a full-power state, and the SOH of the battery is estimated by monitoring the voltage change rate in the process, so that the method has high estimation precision and is not beneficial to online measurement; the slope of the open-circuit voltage change curve is obviously different under different SOH, but the characteristic is not obvious for the battery pack containing a large number of single cells and under various working conditions.
The poorer the health of the battery, the more obvious the change of the alternating current impedance value of the battery. For valve-regulated lead-acid batteries, the discharge performance of the battery deteriorates as the battery loses water, the plates corrode, the plates passivate, and the active material falls off. When the lead-acid battery loses water, the specific gravity of the electrolyte is increased, so that a battery pole plate is corroded, and active substances in the battery are reduced; the active substance of the negative grid plate of the battery is spongy lead, when the charge of the lead-acid battery is insufficient, lead sulfate can be deposited on the positive grid plate and the negative grid plate of the battery, and the quantity of the spongy lead participating in the reaction is further influenced; when the discharge is over-discharged, a large amount of lead sulfate is accumulated on the surface of the negative electrode of the battery, and the more lead sulfate, the more internal resistance of the battery is increased. As the discharge performance of lead-acid batteries is continuously deteriorated, the corresponding influence on the batteries is the change of impedance.
Examples
FIG. 1 is a flow chart of a lead acid battery health assessment method.
A lead-acid battery health degree evaluation method comprises the following steps:
selecting a battery with the same equivalent circuit model as the battery to be tested as a standard battery; the same equivalent circuit model requires the same type of circuit components without requiring that their specifications must be identical. Generally, an unused battery is selected as a standard battery, so that the unused battery can be processed through a large-current accelerated charge-discharge cycle life test to obtain relevant data of the standard battery at different life stages.
Acquiring reference discharge capacity and reference alternating current impedance data of the standard battery at different service life stages; measuring and calculating the reference element parameters in the equivalent circuit corresponding to the standard battery according to the reference alternating-current impedance data; establishing a corresponding relation between the health state of the standard battery and the reference element parameter;
acquiring alternating current impedance data of a battery to be tested; measuring and calculating element parameters in an equivalent circuit corresponding to the battery to be measured according to the alternating current impedance data;
and determining the battery health degree of the battery to be tested according to the element parameters and the corresponding relation between the health state of the standard battery and the reference element parameters.
The method for acquiring the reference discharge capacity and the reference alternating current impedance data of the standard battery at different service life stages comprises the following steps: selecting an unused battery as a standard battery, processing the unused battery by using a large-current accelerated charge-discharge cycle life test, and after the unused battery is sufficiently stood, enabling the standard battery to be in different life stages; and at any service life stage of the standard battery, after the standard battery is fully charged, performing constant current discharge on the standard battery, and measuring and calculating the reference discharge capacity and reference alternating current impedance data of the standard battery at the service life stage.
The method for fully charging the standard battery comprises the following steps: the constant current charging is carried out by 1C current, and when the charging current is less than 1C, the constant voltage charging is carried out by using the charging voltage parameter of the battery. The constant current discharge method comprises the following steps: discharge to the battery cut-off voltage with 1C current.
FIG. 2 is a Thevenin equivalent circuit model of a conventional lead-acid battery, wherein the Thevenin equivalent circuit model is a basis for estimating the health degree of the battery, and is often used for identifying parameters of the lead-acid battery, and has better accuracy and easy operability, and the equivalent circuit model is equivalent to the Thevenin equivalent circuit modelIncluding ohmic internal resistance R in the model0Internal polarization resistance RpAnd a polarization capacitor CpAnd battery open circuit voltage UocAfter the polarized internal resistance is connected in parallel with polarized telephone, it is connected in series with ohmic internal resistance, U0Voltage across ohmic internal resistance, UpFor polarizing the voltage across the internal resistance, i is the operating current of the battery, UiRepresenting the battery terminal voltage.
According to kirchhoff's law and capacitance-voltage-current relationships, the equivalent model can be listed as the following relationships, including:
U0＝R0i
Ui＝Uoc-Uo-Up
fig. 3 is a schematic diagram of a method for establishing a correlation between equivalent element parameters and battery health. Firstly, selecting specific frequency intervals of the lead-acid battery at different stages, recording alternating current impedance values in the intervals in the whole charging and discharging process, selecting a proper battery equivalent circuit model, calibrating alternating current impedance and battery capacity in the intervals selected by the battery at intervals of a preset period, determining element parameters in the equivalent circuit according to the alternating current impedance values in the intervals selected by the equivalent circuit and different preset periods, and finally estimating the battery health degree SOH of the lead-acid battery according to the relevance between the data.
In step 201, the ac impedance in a specific interval of the lead acid battery at different stages is measured, the ac impedance at 29 frequencies in the frequency range of 20Hz to 300Hz is taken, and the ac impedance values of the battery during charging and discharging at different stages are recorded respectively.
In step 202, a Thevenin equivalent circuit model of the battery is selected, and the alternating current impedance and the discharge capacity in the selected interval of the battery are calibrated at intervals of a preset period.
In step 203, on the basis of the equivalent circuit, the ohmic internal resistance R in the equivalent circuit is determined by using the ac impedance values at the 20Hz frequency points under different preset periods0Will cross overThe conversion of the value of the flow impedance into the ohmic internal resistance comprises: the constant ε is chosen to be 10-4In the frequency range of 20Hz-300Hz, as the imaginary part Z of the impedance valueImSatisfy | ZImIf | < epsilon, the AC impedance value can be approximately considered to be equal to the ohmic internal resistance R0。
In step 204, the discharge capacity of the battery at different stages is normalized and recorded as C*Non-linear fitting of ohmic resistance R0And 1-C*Combining SOH as the ratio of the maximum capacity to the nominal capacity of the battery to obtain the ohmic internal resistance R0And SOH estimate. In this embodiment, the relationship is: SOH ═ 1.26-0.6 xr0+0.28×R0 2。
Fig. 4 is a schematic diagram of the ac impedance change of a brand-new unused lead-acid battery before and after a large-current accelerated cycle experiment, and it can be seen that the ac impedance value of the battery is significantly increased along with the decrease of the SOH of the battery, when the battery is measured for 20Hz after being left for 2h through charge-discharge cycle. On the basis of the equivalent circuit, the alternating current impedance value is used for determining element parameters in the equivalent circuit, then the alternating current impedance value in a selected interval under different preset periods is converted into parameter values in the equivalent circuit by a least square method, and the difference is finally reflected in a relational expression of the equivalent element parameter values and the SOH.
The invention is described in detail above with reference to the figures and examples. It should be understood that in practice the description of all possible embodiments is not exhaustive and that the inventive concepts are described herein as far as possible by way of illustration. Without departing from the inventive concept of the present invention and without any creative work, a person skilled in the art should, in all of the embodiments, make optional combinations of technical features and experimental changes of specific parameters, or make a routine replacement of the disclosed technical means by using the prior art in the technical field to form specific embodiments, which belong to the content implicitly disclosed by the present invention.
Claims (6)
1. A lead-acid battery health degree evaluation method is characterized by comprising the following steps:
selecting a battery with the same equivalent circuit model as the battery to be tested as a standard battery;
acquiring reference discharge capacity and reference alternating current impedance data of the standard battery at different service life stages; measuring and calculating the reference element parameters in the equivalent circuit corresponding to the standard battery according to the reference alternating-current impedance data; establishing a corresponding relation between the battery health degree of the standard battery and the reference element parameters;
acquiring alternating current impedance data of a battery to be tested; measuring and calculating element parameters in an equivalent circuit corresponding to the battery to be measured according to the alternating current impedance data;
and determining the battery health degree of the battery to be tested according to the element parameters and the corresponding relation between the battery health degree SOH of the standard battery and the reference element parameters.
2. The lead-acid battery health assessment method according to claim 1, wherein the method of obtaining the reference discharge capacity and the reference ac impedance data for different life stages of the standard battery is: selecting an unused battery as a standard battery, processing the unused battery by using a large-current accelerated charge-discharge cycle life test, and after the unused battery is sufficiently silenced, enabling the standard battery to be in different life stages; and at any service life stage of the standard battery, after the standard battery is fully charged, performing constant current discharge on the standard battery, and measuring and calculating the reference discharge capacity and reference alternating current impedance data of the standard battery at the service life stage.
3. The lead-acid battery health assessment method of claim 2, wherein the constant current discharge method is discharging to the battery cut-off voltage at a current of 1C.
4. The lead-acid battery health assessment method according to claim 1, wherein the equivalent circuit model is a Thevenin equivalent circuit model, and the reference element parameter and the element parameter are ohmic internal resistance R0。
5. The lead-acid battery health assessment method according to claim 4, wherein the method of establishing the correspondence between the state of health of the standard battery and the reference element parameter is: at any service life stage of the standard battery, measuring the alternating current impedance of the standard battery in the excitation frequency range of 20Hz-300Hz, and converting the alternating current impedance data into ohmic internal resistance R0The method comprises the following steps: the constant ε is chosen to be 10-4In the frequency range of 20Hz-300Hz, as the imaginary part Z of the AC impedance dataImSatisfy | ZImIf | < epsilon, the AC impedance data is equal to the ohmic internal resistance R0；
Normalizing the discharge capacity of the standard battery at any service life stage and recording the discharge capacity as C*Non-linearly fitting the ohmic internal resistance R0And 1-C*To obtain the ohmic internal resistance R0And the SOH of the battery.
6. The lead-acid battery health assessment method of claim 5, wherein SOH is 1.26-0.6 xr0+0.28×R0 2In the formula, SOH is the battery health degree, R0Is the ohmic internal resistance.
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