CN105206888B - A kind of internal temperature of lithium ion battery monitoring method - Google Patents

A kind of internal temperature of lithium ion battery monitoring method Download PDF

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CN105206888B
CN105206888B CN201510547525.1A CN201510547525A CN105206888B CN 105206888 B CN105206888 B CN 105206888B CN 201510547525 A CN201510547525 A CN 201510547525A CN 105206888 B CN105206888 B CN 105206888B
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battery
mrow
temperature
lithium ion
discharge
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CN105206888A (en
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宋士刚
林勇
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Zhijiang College of ZJUT
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/486Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for measuring temperature
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

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  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Secondary Cells (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The invention discloses a kind of monitoring method of internal temperature of lithium ion battery, comprise the following steps:1) charge-discharge test under the conditions of varying environment is carried out to lithium ion battery using charge-discharge test instrument, obtains battery surface temperature variation curve;2) relevant parameter such as the internal resistance of cell and open-circuit voltage temperature coefficient is tested, establishes the lithium ion battery electro thermal coupling model based on variable rate of heat production;3) the temperature rise change to battery discharge procedure emulates, and obtains temperature change simulation curve;4) by carrying out com-parison and analysis to experiment test temperature variation curve and simulation curve, electro thermal coupling model is optimized and verified;5) influence between internal temperature of battery and battery surface temperature, discharge current and depth of discharge is analyzed, builds internal temperature of lithium ion battery model;6) internal temperature of battery is monitored in real time according to this model.The inventive method is simple and easy, and estimation error is small, can preferably meet the needs of internal temperature of battery monitors in real time.

Description

A kind of internal temperature of lithium ion battery monitoring method
Technical field
The invention belongs to technical field of lithium ion, is supervised more specifically to a kind of internal temperature of lithium ion battery Survey method.
Background technology
Lithium ion battery appears in phase early 1990s, in the time of short twenties years, lithium ion battery skill Art has obtained unprecedented development.At present, performance of lithium ion battery either still uses the longevity than energy, specific power, operating voltage Life is all more excellent than lead-acid battery, Ni-MH battery, progressively as the developing direction of electrokinetic cell.With the security of lithium ion battery Energy, the improvement of low temperature performance, it is also more and more as the electric automobile of power source using lithium-ion-power cell, show very Wide application prospect.But as electrochmical power source, lithium ion battery is in discharge and recharge along with the chemistry of complexity, electrochemical reaction Process and transmission course of material, the change of caused heat and other factors joint effect battery temperature in these courses of reaction. Temperature all has an impact to the various aspects of performance of lithium ion battery, including the working condition of battery, cycle efficieny, uniformity, capacity With power etc., and then influence whether performance, reliability, security and life-span of electric automobile etc..
At present, the method for traditional monitoring lithium ion battery temperature is measurement battery surface temperature, and the temperature so measured is not Energy accurate response goes out the actual state of inside battery, can not be controlled for internal temperature of lithium ion battery and provide accurate information.Separately Outside, also have by built-in temperature sensor to measure the internal temperature of battery, but this method can only be in cell production process Carry out, to existing battery and do not apply to.
An important factor for internal temperature of lithium ion battery is influence electric automobile effect propety, but the inside temperature of existing battery Degree can not direct measurement, internal temperature of battery field is obtained by three-dimensional thermal model mostly, but the amount of calculation of this method is too big, can not Applied on real vehicle.Simple one-dimensional thermal model or lumped-mass model estimation internal temperature of battery can be used in addition, but model is estimated It is relatively low to count precision, real vehicle demand can not be met.
The content of the invention
Instant invention overcomes drawbacks described above in the prior art, proposes a kind of monitoring method of internal temperature of lithium ion battery, In order to monitor the temperature of inside lithium ion cell, internal high temperature hidden danger is eliminated, and then improve the security of lithium ion battery.
To reach above-mentioned purpose, the technical scheme is that:
A kind of internal temperature of lithium ion battery monitoring method, comprises the following steps:
1) charge-discharge test under the conditions of varying environment, measurement are carried out to lithium ion battery first with charge-discharge test instrument Surface temperature of lithium ion battery change curve in charge and discharge process;
2) lithium ion battery internal resistance and open-circuit voltage temperature coefficient are tested, establishes the electric heating coupling based on variable heat speed Matched moulds type;
3) using the lithium ion battery electro thermal coupling model established, the battery exothermal process under the conditions of varying environment is carried out Three-dimensional artificial, and obtain temperature change simulation curve;
4) simulation curve obtained again by the surface temperature change curve and step 3) that are obtained to step 1) is compared Analysis, is optimized to electro thermal coupling model;
5) and then internal temperature of lithium ion battery and the influence of varying environment factor are analyzed, builds internal temperature of battery mould Type, and verified;
6) the internal temperature of lithium ion battery model based on step 5) structure, according to varying environment factor, to inside battery Temperature is monitored in real time.
Described environmental condition refers to environment temperature, different charge-discharge magnifications and coefficient of heat transfer condition;Described environment Factor refers to charging and discharging currents, battery surface temperature and depth of discharge (Depth of discharge, DOD).
In described step 1) in battery charging and discharging experimentation, battery surface arranges 11 test points altogether, it is contemplated that just Temperature has larger difference with other surfaces at negative electrode lug, is respectively arranged 2 temperature sensors in battery electrode column.
In described step 2) during the test internal resistance of cell, using mixed pulses power characteristic method of testing, method of testing letter It is single quick.
In described step 2) in battery open circuit voltage temperature coefficient test process, first by battery constant-current constant-voltage charging to completely Electricity condition, stand 3 hours;It is put in afterwards in high-low temperature chamber, 5 DEG C of initial temperature is set, and every 5 hours exchange a temperature extremely 15 DEG C and 25 DEG C, measure the change of the open-circuit voltage of battery at different temperatures.
When being compared analysis to the simulation curve of battery exothermal process in described step 3), the setting of battery heat speed For variable, constantly change with the increase of depth of discharge, it is more conformed to reality.
By analyzing the depth of discharge, charging and discharging currents and battery of internal temperature of battery and battery in described step 5) The relation of surface temperature, internal temperature of battery model is established to estimate internal temperature.
The beneficial effects of the invention are as follows:In internal temperature of lithium ion battery monitoring method proposed by the present invention, for energy comprehensively The temperature of battery surface everywhere is embodied, the head of 11 temperature sensors is closely attached to the surface of cell, ensures temperature Spend the accuracy of measurement, it is contemplated that temperature has larger difference with other surfaces at positive and negative lug, is respectively arranged 2 temperature sensors In battery electrode column.Using Arbin charge-discharge tests instrument at room temperature, with 0.5C constant-current charges to 3.6V, turn constant-voltage charge, work as electricity When stream is down to 10%, charging terminates, and shelves 2h, is then discharged respectively with 1C, 2C, 3C, terminates to electric discharge during voltage 2.5V.Charge and discharge In electric process, surface temperature of lithium ion battery is measured in real time using temperature sensor.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, the internal resistance of cell uses mixed pulses power characteristic Method of testing (HPPC), method of testing simple and fast.Battery is calculated using one group of discharge pulse and charging pulse in this method Electric discharge and internal charging resistance under different DOD.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, in order to more accurately assess open-circuit voltage and temperature Relation between degree, battery open circuit voltage temperature coefficient can be asked for.By battery constant-current constant-voltage charging to full power state, it is small to stand 3 When;It is put in afterwards in high-low temperature chamber, 5 DEG C of initial temperature is set, and exchange within every 5 hours a temperature to 15 DEG C and 25 DEG C, surveys Measure the change of the open-circuit voltage of battery at different temperatures.In this approach, measurement battery is opened a way electricity under different DOD states respectively The temperature varying coefficient of pressure.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, when establishing lithium ion battery thermal effect model, Assuming that battery cell is an independent closed system, itself and the external world only carry out the exchange of heat without the boundary of material.And The structural material of battery is simplified, it is assumed that inside battery material each several part is uniform, and specific heat capacity is constant, in same direction On, the thermal conductivity of battery is equal and is not influenceed by battery charge state (SOC) and temperature.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, the ion battery electro thermal coupling mould based on foundation Type, the influence under the conditions of varying environment to battery temperature field is analyzed using the method for simulation analysis.Simulation analysis software is ANSYS business softwares, equation of heat balance of the ANSYS heat analysis based on conservation of energy principle, with each node of Finite element arithmetic Temperature, and obtain temperature change simulation curve.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, because the discharge process of battery is a typical case The transient heat conduct process for having time-varying endogenous pyrogen, the heat speed of battery is presented with the increase of depth of discharge in discharge process The trend risen.Therefore, the temperature rise rate of electro thermal coupling model is set as variable by the present invention, continuous with the increase of depth of discharge Change, particularly phase temperature rise rate rises quickly after discharge, it is more conformed to measured result.However, current most of lithiums In cell thermal model simulation process, the heat speed of battery is set as constant, it is clear that do not meet actual requirement.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, by analyze internal temperature of lithium ion battery with The relation of the depth of discharge of battery, charging and discharging currents and battery surface temperature, internal temperature of battery model is established come in estimating Portion's temperature.The result of calculation of the model differs very little with the simulation result of electro thermal coupling model, and computational methods are simple and easy, can be with Meet monitoring internal temperature of lithium ion battery in real time.
Compared with prior art, the present invention establishes the electro thermal coupling model based on variable heat speed, and in an experiment Demonstrate the validity of model.On this basis, the polynomial function evaluation method of internal temperature of battery is given, by with imitating True mode result of calculation contrasts, and this method can preferably meet the needs of internal temperature of battery monitoring.
Brief description of the drawings
Fig. 1 is the flow chart of internal temperature of lithium ion battery monitoring method of the present invention;
Fig. 2 is the temperature variation curve under lithium ion battery difference discharge-rate in the embodiment of the present invention;Abscissa is electricity Tank discharge time, ordinate are battery surface temperature;
Fig. 3 is mixed pulses power characteristic test curve in the embodiment of the present invention;Abscissa is the battery charging and discharging time, is indulged Coordinate is battery charging and discharging voltage and current;
Fig. 4 is battery discharge simulation result and test result comparison diagram under different DOD in the embodiment of the present invention;Abscissa is Battery discharge depth, ordinate are battery surface temperature;
Fig. 5 is the temperature field distribution in battery discharge procedure emulation in inside battery plane in the embodiment of the present invention Figure;
Fig. 6 is the temperature field distribution in battery discharge procedure emulation on inside battery straight line in the embodiment of the present invention Figure.
Embodiment
Embodiment 1
It is further detailed to the embodiment work of the present invention with reference to the description of embodiment below against accompanying drawing Explanation.Internal temperature of lithium ion battery monitoring method flow of the present invention is as shown in Figure 1:
1) first with charge-discharge test instrument to (varying environment bar under the conditions of lithium ion battery to be detected progress varying environment Part includes environment temperature, different charge-discharge magnifications and coefficient of heat transfer condition) charge-discharge test, multiple temperature sensors are tight The surface of cell is closely attached to, measures surface temperature of lithium ion battery change curve in charge and discharge process;The present embodiment selects Sample is 3.2V/20Ah ferric phosphate lithium ion batteries, discharge cut-off voltage 2.5V, charge cutoff voltage 3.6V, cell chi It is very little:Long 70mm × wide 28mm × high 138mm.Battery surface arranges 11 test points altogether, it is contemplated that at positive and negative lug temperature and its He has larger difference in surface, and 2 temperature sensors must be arranged in battery electrode column.
Using Arbin charge-discharge tests instrument at room temperature, with 10A constant-current constant-voltage chargings to 3.6V, 2h is stood, is then distinguished Discharged with 1C, 2C, 3C, terminated to electric discharge during voltage 2.5V.In discharge process, using temperature sensor to lithium ion battery surface Temperature is measured in real time.When battery is discharged with 1C, the initial temperature of battery is 17.5 DEG C, and electric discharge total time is 3725s.Battery The temperature of each several part increases with the increase of discharge time, and each several part temperature reaches maximum when 3780s is tied in electric discharge.Battery with During 2C multiplying power dischargings, the initial temperature of battery is 22.5 DEG C, discharge 1885s when battery temperature be up to 39.2 DEG C.Battery is with 3C During multiplying power discharging, the initial temperature of battery is 24.5 DEG C, discharge 1253s when battery temperature be up to 44.6 DEG C.Fig. 3 is shown point Not Cai Yong 1C, 2C and 3C electric discharge when, the change of battery surface center (test point 5) temperature.As shown in Figure 2, battery surface Temperature rise rate improves constantly with the increase of discharge-rate, and surface temperature constantly raises.As seen from Figure 2, in electric discharge electricity at initial stage The temperature rise in pond is very fast, slows down in the temperature rise of electric discharge mid-term battery, the temperature rise of phase battery after discharge then can be raised drastically.
2) test lithium ion battery internal resistance and open-circuit voltage temperature coefficient, analysis internal temperature of battery by can not backheating with And can backheating influence, establish the electro thermal coupling model based on variable heat speed;The test internal resistance of cell in described step 2) When, using mixed pulses power characteristic method of testing, method of testing simple and fast.Battery open circuit voltage temperature in described step 2) Spend in coefficient test process, first by battery constant-current constant-voltage charging to full power state, stand 3 hours;It is put in afterwards in high-low temperature chamber, 5 DEG C of initial temperature is set, and exchanges within every 5 hours a temperature to 15 DEG C and 25 DEG C, measures the open-circuit voltage of battery in difference At a temperature of change.
The present embodiment step 2) is when establishing lithium ion battery electro thermal coupling model, it is assumed that battery cell is one independent Closed system, it only carries out exchanging for heat with extraneous.And the structural material of battery is simplified, it is assumed that inside battery material Expect that each several part is uniform, specific heat capacity is constant, and in the same direction, the thermal conductivity of battery is equal and not by state-of-charge (State OfCharge, SOC) and temperature influence.Thus, lithium ion battery Three dimensional transient heat transfer equation is established
In formula, ρ is the equivalent density of micro unit;CpHold for the equivalent specific heat of micro unit;K is the equivalent heat conduction system of micro unit Number, q are the heat speed of micro unit;qdFor the rate of heat dispation on micro unit surface.Can be simply by cell heat from formula (1) The problem of model, is classified as the calculating of heat speed, battery specific heat capacity and thermal conductivity factor.In existing lithium ion battery thermal model Thermal source is substantially to be expressed as based on Bernardi heat models, its heat generation rate
In formula, E is the open-circuit voltage of battery;U is the operating voltage of battery;QmiProduced for the speed of different material reaction rate Raw heat generation rate;QpcFor the heat speed of phase transformation reaction.Part I is the irreversible heat speed of battery on the right of formula (2), the Two parts are the reversible heat speed of battery, and Part III heat speed is produced by inside battery different material reaction rate speed Concentration gradient cause, last part is phase transformation reaction heat speed.In lithium ion battery charge and discharge process, can not backheating with Reversible hot radical originally covers the overwhelming majority of battery heat production, QmiAnd QpcContribution to quantity of heat production is less, i.e., this part of heat energy can neglect Slightly disregard.Can not caused by backheating heat is due to electrode polarization, electrode polarization show as electrode potential deviate from can reciprocal value, i.e., Overpotential.Thus, unit volume heat speed q is expressed as:
In formula,For the overpotential of unit volume;R is the resistivity of unit volume;I is the electric current in battery unit somewhere Density.
Thus, it is necessary to obtain the internal resistance of cell and open-circuit voltage temperature in lithium ion battery electro thermal coupling model application process Spend the parameters such as coefficient.The present embodiment is using mixed pulses power characteristic method of testing (HPPC) test battery charging and discharging internal resistance. HPPC methods are calculated electric discharge of the battery under different depth of discharges (DOD) using one group of discharge pulse and charging pulse and filled Electric internal resistance, the present embodiment will discharge and charging pulse time unification is 10s.HPPC method of testings are to apply pulse current discharge and recharge Method calculate the discharge and recharge internal resistance of battery, be illustrated in figure 3 battery current electricity in mixed pulses power characteristic test process Press change curve.Wherein negative value is discharge pulse, on the occasion of for charging pulse.Wherein discharge internal resistance RdisCalculation expression be:
In addition, by the way that with 10Ah constant-current constant-voltage chargings to full power state, battery is stood into 3 hours;High/low temperature is put in afterwards In case, 5 DEG C of initial temperature is set, and exchanges within every 5 hours a temperature to 15 DEG C and 25 DEG C, the open-circuit voltage for measuring battery exists Change under different temperatures, obtain battery open circuit voltage temperature coefficient.
3) using establish lithium ion battery electro thermal coupling model, to varying environment temperature, different charge-discharge magnifications and Battery exothermal process under the conditions of coefficient of heat transfer carries out three-dimensional artificial, obtains battery cell temperature field, and obtain temperature change and imitate True curve;Because experimental method by step 1), 2) is typically only capable of obtaining the thermo parameters method of battery surface, and inside battery There is larger temperature difference between battery surface, so battery surface temperature can not truly reflect the temperature conditions of inside battery, And the temperature field of inside battery can be more accurately obtained using simulation analysis.
The present embodiment step 3) is in order to analyze cell internal temperature field distribution, using the thermocouple established in step 2) Matched moulds type, 24.5 DEG C of initial temperature is set, to battery 3C discharge temps field under Natural Convection Conditions, using ANSYS simulation softwares (ANSYS companies of U.S. finite element analysis software), is emulated to the temperature field of inside battery.Fig. 5 represents battery discharge procedure Temperature field pattern in emulation in inside battery plane, the center that battery is crossed in the plane make a straight line, are allowed to flat Row is as shown in Figure 6 in the Temperature Distribution of battery in Y-axis, the straight line.By thermo parameters method figure can be seen that internal temperature of battery with The different different of position, maximum temperature center portion position in the battery.Fig. 5 and Fig. 6 more intuitively describe battery center With the temperature difference of outer surface, the temperature values of battery different directions is different different with position, and maximum temperature is in battery Centre.
4) simulation curve obtained by the surface temperature change curve and step 3) that are obtained to step 1) is compared point Analysis, the variation tendency of electro thermal coupling model and traditional thermal model simulation result and battery observed temperature is analyzed, to electro thermal coupling Model optimizes;
Lithium ion battery is carried out using ANSYS simulation softwares model foundation and mesh generation, boundary condition setting with And the determination of battery heat speed carries out the simulation analysis in temperature field in battery discharge procedure.Current most of lithium battery thermal models In simulation process, the heat speed of battery is set as constant, it is clear that do not meet actual requirement.The present embodiment is obtained by experiment Take, set heat speed as variable, the temperature rise rate of electro thermal coupling model constantly changes with the increase of depth of discharge, particularly Phase temperature rise rate rises quickly after discharge, it is more conformed to measured result.Fig. 4 show simulation result and experiment test number According to comparison diagram, as seen from Figure 4, the change of the simulation result and battery observed temperature of thermal model and electro thermal coupling model becomes Gesture is substantially consistent, and the result of calculation of wherein electro thermal coupling model more meets test data of experiment.
5) temperature field of inside battery can be more accurately obtained using the analysis of electro thermal coupling model emulation, but amount of calculation is too Greatly, internal temperature of battery can not be monitored in real time.Therefore in analysis battery charge and discharge process, internal temperature of lithium ion battery t is filled The influence of the factors such as discharge current I, battery surface temperature T and depth of discharge DOD, internal temperature of battery model is established to estimate Internal temperature.According to the measured data to the present embodiment, inside battery maximum temperature model t is built by way of Function Fitting =f (I, T, DOD), temperature model is fitted using quadratic polynomial as follows:
6) using the function of above-mentioned fitting, based on the inside lithium ion cell maximum temperature model of step 5) structure, application During, according to battery present discharge depth, charging and discharging currents and the battery surface temperature detected in real time, using multinomial letter Number can estimate inside battery maximum temperature.The result of calculation of the model differs very little with the simulation result of electro thermal coupling model, Computational methods are simple and easy, can meet to monitor internal temperature of battery in real time.
It is that can embody battery surface comprehensively everywhere in the internal temperature of lithium ion battery monitoring method that the present embodiment proposes Temperature, the head of 11 temperature sensors is closely attached to the surface of cell, ensures the accuracy of temperature survey, considered Temperature has larger difference with other surfaces at positive and negative lug, is respectively arranged 2 temperature sensors in battery electrode column.Use Arbin charge-discharge tests instrument at room temperature, with 0.5C constant-current charges to 3.6V, turns constant-voltage charge, when electric current is down to 10%, fills Electricity terminates, and shelves 2h, is then discharged respectively with 1C, 2C, 3C, terminates to electric discharge during voltage 2.5V.In charge and discharge process, temperature is utilized Degree sensor is measured surface temperature of lithium ion battery in real time.
In the internal temperature of lithium ion battery monitoring method that the present embodiment proposes, the internal resistance of cell is special using mixed pulses power Property method of testing (HPPC), method of testing simple and fast.Electricity is calculated using one group of discharge pulse and charging pulse in this method Electric discharge and internal charging resistance of the pond under different DOD.
In internal temperature of lithium ion battery monitoring method proposed by the present invention, in order to more accurately assess open-circuit voltage and temperature Relation between degree, battery open circuit voltage temperature coefficient can be asked for.By battery constant-current constant-voltage charging to full power state, it is small to stand 3 When;It is put in afterwards in high-low temperature chamber, 5 DEG C of initial temperature is set, and exchange within every 5 hours a temperature to 15 DEG C and 25 DEG C, surveys Measure the change of the open-circuit voltage of battery at different temperatures.In this approach, measurement battery is opened a way electricity under different DOD states respectively The temperature varying coefficient of pressure.
In the internal temperature of lithium ion battery monitoring method that the present embodiment proposes, lithium ion battery thermal effect model is established When, it is assumed that battery cell is an independent closed system, and itself and the external world only carry out the exchange of heat without the boundary of material. And the structural material of battery is simplified, it is assumed that inside battery material each several part is uniform, and specific heat capacity is constant, same On direction, the thermal conductivity of battery is equal and is not influenceed by battery charge state (SOC) and temperature.
In the internal temperature of lithium ion battery monitoring method that the present embodiment proposes, the ion battery electro thermal coupling based on foundation Model, the influence under the conditions of varying environment to battery temperature field is analyzed using the method for simulation analysis.Simulation analysis software is ANSYS business softwares, equation of heat balance of the ANSYS heat analysis based on conservation of energy principle, with each node of Finite element arithmetic Temperature, and obtain temperature change simulation curve.
In the internal temperature of lithium ion battery monitoring method that the present embodiment proposes, because the discharge process of battery is an allusion quotation The transient heat conduct process for having time-varying endogenous pyrogen of type, the heat speed of battery is presented with the increase of depth of discharge in discharge process The trend of rising.Therefore, the temperature rise rate of electro thermal coupling model is set as variable by the present embodiment, with the increase of depth of discharge Constantly change, particularly phase temperature rise rate rises quickly after discharge, it is more conformed to measured result.However, at present mostly In number lithium battery thermal model simulation process, the heat speed of battery is set as constant, it is clear that do not meet actual requirement.
In the internal temperature of lithium ion battery monitoring method that the present embodiment proposes, by analyzing internal temperature of lithium ion battery The relation of depth of discharge, charging and discharging currents and battery surface temperature with battery, establishes internal temperature of battery model to estimate Internal temperature.The result of calculation of the model differs very little with the simulation result of electro thermal coupling model, and computational methods are simple and easy, can To meet monitoring internal temperature of lithium ion battery in real time.
Compared with prior art, the present embodiment establishes the electro thermal coupling model based on variable heat speed, and is testing In demonstrate the validity of model.On this basis, give the polynomial function evaluation method of internal temperature of battery, by with Results of model simulation contrasts, and this method can preferably meet the needs of internal temperature of battery monitoring.

Claims (4)

1. a kind of internal temperature of lithium ion battery monitoring method, it is characterised in that comprise the following steps:
1) charge-discharge test under the conditions of varying environment is carried out to lithium ion battery first with charge-discharge test instrument, by multiple temperature Degree sensor is closely attached to the surface of cell, measures surface temperature of lithium ion battery change curve in charge and discharge process;
2) lithium ion battery discharge and recharge internal resistance and open-circuit voltage temperature coefficient are tested, establishes the electric heating based on variable heat speed Coupling model;When establishing lithium ion battery electro thermal coupling model, the battery cell closed system independent as one, its with it is outer Boundary only carries out the exchange of heat, and inside battery material each several part is uniform, and specific heat capacity is constant, in the same direction, electricity The thermal conductivity in pond is equal and is not influenceed by state-of-charge and temperature;Micro unit is equivalent in lithium ion battery electro thermal coupling model Density is ρ, and it is C that the equivalent specific heat of micro unit, which holds,p, the Equivalent Thermal Conductivities of micro unit are k, and the heat speed of micro unit is q, micro- The rate of heat dispation in first body surface face is qd, thus, establish lithium ion battery Three dimensional transient heat transfer equation
<mrow> <msub> <mi>&amp;rho;C</mi> <mi>p</mi> </msub> <mfrac> <mrow> <mi>d</mi> <mi>T</mi> </mrow> <mrow> <mi>d</mi> <mi>t</mi> </mrow> </mfrac> <mo>=</mo> <mo>&amp;dtri;</mo> <mo>&amp;CenterDot;</mo> <mrow> <mo>(</mo> <mi>k</mi> <mo>&amp;dtri;</mo> <mi>T</mi> <mo>)</mo> </mrow> <mo>+</mo> <mi>q</mi> <mo>-</mo> <msub> <mi>q</mi> <mi>d</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow>
The problem of cell thermal model, is classified as to the calculating of heat speed, battery specific heat capacity and thermal conductivity factor from formula (1);It is based on Battery heat rate representation is in the lithium ion battery thermal model of Bernardi heat models
<mrow> <mi>Q</mi> <mo>=</mo> <mi>I</mi> <mrow> <mo>(</mo> <mi>E</mi> <mo>-</mo> <mi>U</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>I</mi> <mi>T</mi> <mfrac> <mrow> <mi>d</mi> <mi>E</mi> </mrow> <mrow> <mi>d</mi> <mi>T</mi> </mrow> </mfrac> <mo>+</mo> <msub> <mi>Q</mi> <mrow> <mi>m</mi> <mi>i</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>Q</mi> <mrow> <mi>p</mi> <mi>c</mi> </mrow> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow>
In formula parameter have the open-circuit voltage E of battery, the operating voltage U of battery, different material reaction rate speed caused by it is raw Hot speed Qmi, phase transformation reaction heat speed Qpc;Part I is the irreversible heat speed of battery on the right of formula (2), second It is divided into the reversible heat speed of battery, Part III heat speed is dense as caused by inside battery different material reaction rate speed Degree gradient causes, and Part IV is phase transformation reaction heat speed;Due in lithium ion battery charge and discharge process, QmiAnd QpcTo production The contribution of heat is seldom, i.e., this part of heat energy does not consider;Caused by the irreversible heat of battery is due to electrode polarization, electrode polarization Showing as that electrode potential deviates from can reciprocal value, i.e. overpotential;The overpotential of unit volume isThe resistivity of unit volume is R, the current density in battery unit somewhere is i, it can thus be concluded that unit volume heat speed q ' is:
<mrow> <msup> <mi>q</mi> <mo>&amp;prime;</mo> </msup> <mo>=</mo> <mo>&amp;dtri;</mo> <mi>&amp;eta;</mi> <mo>&amp;CenterDot;</mo> <mi>i</mi> <mo>=</mo> <msup> <mi>ri</mi> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>
3) using the test battery charging and discharging internal resistance of mixed pulses power characteristic method of testing, mixed pulses power characteristic method of testing Electric discharge and internal charging resistance of the battery under different depth of discharges is calculated using one group of discharge pulse and charging pulse, wherein putting Electric internal resistance RdisCalculation expression be:
<mrow> <msub> <mi>R</mi> <mrow> <mi>d</mi> <mi>i</mi> <mi>s</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mrow> <mi>&amp;Delta;</mi> <mi>U</mi> </mrow> <mrow> <mi>&amp;Delta;</mi> <mi>I</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <msub> <mi>U</mi> <mrow> <mi>t</mi> <mn>1</mn> </mrow> </msub> <mo>-</mo> <msub> <mi>U</mi> <mrow> <mi>t</mi> <mn>0</mn> </mrow> </msub> </mrow> <mrow> <msub> <mi>I</mi> <mrow> <mi>t</mi> <mn>1</mn> </mrow> </msub> <mo>-</mo> <msub> <mi>I</mi> <mrow> <mi>t</mi> <mn>0</mn> </mrow> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>
4) according to the lithium ion battery electro thermal coupling model of foundation, model is carried out to lithium ion battery using ANSYS simulation softwares Foundation and mesh generation, the setting of boundary condition and the determination of battery heat speed, the battery under the conditions of varying environment is produced Thermal process carries out three-dimensional artificial, obtains battery cell temperature field, and obtain temperature change simulation curve;
5) the battery temperature change emulation obtained by the battery surface temperature variation curve and step 4) that are obtained to step 1) is bent Line is compared analysis, and electro thermal coupling model is optimized;
6) analyze in battery charge and discharge process, inside lithium ion cell maximum temperature t is by charging and discharging currents I, battery surface temperature T And the influence of depth of discharge environmental factor, inside battery maximum temperature model is established to estimate inside battery maximum temperature;Root According to measured data, inside battery maximum temperature model t=f (I, T, DOD) is built by way of Function Fitting, and using secondary Multinomial is fitted to temperature model;
7) the inside lithium ion cell maximum temperature model based on step 6) structure, according to battery present discharge depth, discharge and recharge Electric current and the battery surface temperature detected in real time, using quadratic polynomial Function Estimation inside battery maximum temperature;
Described environmental condition refers to environment temperature, different charge-discharge magnifications and coefficient of heat transfer condition;Described environmental factor Refer to charging and discharging currents, battery surface temperature and depth of discharge.
A kind of 2. internal temperature of lithium ion battery monitoring method according to claim 1, it is characterised in that:Described step 1) in battery charging and discharging experimentation, battery surface arranges 11 test points altogether, it is contemplated that at positive and negative lug temperature and other There is larger difference on surface, is respectively arranged 2 temperature sensors in battery electrode column.
A kind of 3. internal temperature of lithium ion battery monitoring method according to claim 1, it is characterised in that:Described step 2) in battery open circuit voltage temperature coefficient test process, first by battery constant-current constant-voltage charging to full power state, 3 hours are stood; It is put in afterwards in high-low temperature chamber, 5 DEG C of initial temperature is set, and exchanges within every 5 hours a temperature to 15 DEG C and 25 DEG C, measurement electricity The change of the open-circuit voltage in pond at different temperatures.
A kind of 4. internal temperature of lithium ion battery monitoring method according to claim 1, it is characterised in that:Described step 4) battery heat speed is set as variable in, is constantly changed with the increase of depth of discharge, it is more conformed to reality.
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