CN107677965B - A kind of lithium battery energy state evaluation method - Google Patents
A kind of lithium battery energy state evaluation method Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
A kind of lithium battery energy state evaluation method comprising following steps: step 1, considering electric energy, thermal energy and on the basis of off-energy, establish the mathematics appraising model of lithium battery energy state；Step 2 is discharged stage by stage using battery overall process electric discharge, and the first stage discharges under nonstandard design, and second stage is discharged under standard condition, obtains the electric energy of battery first stage and second stage electric discharge and the parameter of thermal energy；The energy summation of step 3, the energy that battery first stage and second stage electric discharge release is calculated and overall process release；Step 4 obtains battery maximum available energy E using energy summation data progress Function FittingmaxAnd Eloss(I,T1) mathematic(al) representation；Above-mentioned parameter and expression formula are substituted into step 1 by step 5, carry out real-time estimation to energy state SOE in conjunction with acquisition data.The present invention obtains accurate lithium battery energy state in the case where having comprehensively considered electric energy, thermal energy and off-energy influences battery power status estimation.
Description
Technical field
The present invention relates to technical field of lithium batteries, and in particular to arrives a kind of lithium battery energy state evaluation method.
Background technique
Battery status is generally characterized with battery dump energy, can be described from the angle of capacity or energy,
The former residual capacity accounts for the ratio of rated capacity, i.e. battery charge state (SOC)；The latter indicates that remaining utilisable energy Zhan is total
The ratio of energy, i.e. battery power status (SOE).The case where electric quantity change is described due to SOC, while between the voltage of end
There are stronger coupled relations, predict to be easy to lead to biggish prediction error when the parameter directly related with power using SOC.And
SOE then with power parameter linear correlation, therefore in practical applications, using SOE to continual mileage, cruise duration of battery etc. into
Row is measured and estimation, will be a kind of more accurate method.
But current battery energy state estimation precision is not still high, is on the one hand that computation model is inaccurate, battery is exchanged work
When condition is run, electricity, thermal parameters change, and above-mentioned variation does not obtain off-energy brought by battery temporarily
More perfect consideration；On the other hand, the estimation of battery initial energy state also not formed preferable scheme, leads to current entirety
Estimation precision is still lower.
Summary of the invention
The object of the present invention is to provide a kind of lithium battery energy state evaluation methods, to solve the estimation of lithium battery energy state
Inaccurate problem.
To achieve the above object, the technical solution adopted by the present invention is that:
A kind of lithium battery energy state evaluation method comprising following steps:
The energy of lithium battery discharge process is divided into electric energy, thermal energy and off-energy three parts by step 1, is considering electricity
On the basis of energy, thermal energy and off-energy, the mathematics appraising model of lithium battery energy state is established are as follows:
Wherein, SOE (k) is current time battery power status, and SOE (k-1) is last moment battery power status, tk、
tk-1Respectively current time and last moment time value, u are battery terminal voltage, and i is discharge current and takes positive value, and R is in battery
Resistance, EmaxFor battery maximum available energy, Eloss(i, T) is the off-energy of battery, Esum(i, T) be battery release electric energy and
The summation of thermal energy；
Step 2, the electric energy and thermal energy parameter for using battery overall process electric discharge acquisition battery: with discharge cut-off voltage a1V,
Upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, discharge process is divided into two stages, and the first stage: battery is put non-standard
Electric discharge records the electric energy of first stage battery and the parameter of thermal energy up to reaching cut-off condition under electrician's condition；Second stage: first
After stage, battery standing restores to battery temperature to rated temperature, discharge to battery using standard electric discharge operating condition straight
To cut-off condition is reached, the electric energy and thermal energy parameter of second stage battery are recorded；
Step 3, using the parameter of above-mentioned electric energy and thermal energy, respectively obtain at least two groups battery the first rank during discharge
The electric energy W of section consumptione1(i, T) and thermal energy Wh1(i, T), the electric energy W of second stage consumptione2(i, T) and thermal energy Wh2(i, T), then
We1(i, T)=u1×i1×Δt (2)
Wh1(i, T)=i1 2×R1×Δt (3)
And obtain the energy of battery first stage release:
We2(i, T)=u2×i2×Δt (5)
Wh2(i, T)=i2 2×R2×Δt (6)
And obtain the energy of battery second stage release:
Total property of battery are as follows: E (i, T)=Esum(i,T)+E'sum(i,T)
Wherein, Δ t=tk-tk-1, u1And i1Respectively the first stage when battery terminal voltage and discharge current, u2And i2Respectively
Battery terminal voltage and discharge current when for second stage, internal resistance of cell R are the summation of battery ohmic internal resistance and polarization resistance；
Step 4, using at least two groups E (i, T) data carry out Function Fitting, and obtain fitting function maximum value E (i,
T)max,
To which battery maximum available energy is are as follows: Emax=E (i, T)max (8)
Battery is in T moment off-energy known to then are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)；
Step 5 substitutes into formula (4), (8) and (9) in formula (1), and the energy state SOE (k) of T moment battery can be obtained.
Practice have shown that lithium battery, under different electric discharge operating conditions, the electric energy and thermal energy of release be not identical, and electric energy and heat
The summation of energy is also inconsistent, this phenomenon explanation battery under partial discharge operating condition causes its maximum available there are energy loss
Energy can not be completely converted into electric energy and thermal energy.The present invention can be reflected by the parameter of the introducing off-energy in appraising model
The influence of different discharge currents, varying environment temperature to energy state has comprehensively considered electric energy, thermal energy and off-energy to battery
The influence of energy state estimation, to obtain accurate lithium battery energy state.Meanwhile battery discharge is discharged using overall process
Method, and be fitted to obtain battery maximum available energy with two stage electric energy and thermal energy, traditional rated energy parameter is modified,
Further improve the accuracy of estimation.
The state that SOE is 100% is defined as battery fully charged state, namely under standard charging operating condition, after first constant current
The mode of constant pressure charge the battery until charging current be less than 0.02C, think at this time SOE be 100%；The shape that SOE is 0%
State is defined as battery maximum available energy EmaxThe state all consumed.
As an improvement of the present invention, state-of-charge SOC battery initial energy state SOE (0) current by battery
(0) it obtains, relational expression are as follows:
SOE (0)=m × SOC (0)+n (10)
Wherein, m, n are the coefficient of coup of SOE and SOC curve.
Further, the detailed process of the first stage of the battery overall process electric discharge are as follows: at a temperature of nominal environment, with
Discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, battery is put under different discharge-rates
Electricity, electric discharge is until reach cut-off condition.
Further, the detailed process of the first stage of the battery overall process electric discharge are as follows: under nominal discharge multiplying power, with
Discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, battery is put at different ambient temperatures
Electricity, electric discharge is until reach cut-off condition.
As an improvement of the present invention, in the step 2 using battery overall process electric discharge obtain battery electric energy and
Thermal energy parameter: the electric energy and thermal energy gain of parameter mode of first group of battery are as follows: with discharge cut-off voltage a1V, upper limit cut-off temperature b1
DEG C as electric discharge cut-off condition, discharge process is divided into two stages, the first stage: at a temperature of nominal environment, in different electric discharges
It discharges under multiplying power battery, electric discharge records the electric energy of first stage battery and the parameter of thermal energy up to reaching cut-off condition；
Second stage: after the first stage, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition pair
Battery carries out electric discharge until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery；
The electric energy and thermal energy gain of parameter mode of second group of battery are as follows: with discharge cut-off voltage a1V, upper limit cut-off temperature b1
DEG C as electric discharge cut-off condition, discharge process is divided into two stages, the first stage: under nominal discharge multiplying power, in varying environment
At a temperature of discharge battery, electric discharge records the electric energy of first stage battery and the parameter of thermal energy until reach cut-off condition；
Second stage: after the first stage, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition pair
Battery carries out electric discharge until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery.
Compared with prior art, the invention has the following advantages that
The present invention can reflect different discharge currents, varying environment by the parameter of the introducing off-energy in appraising model
Influence of the temperature to energy state is comprehensively considering what electric energy, thermal energy and off-energy influenced battery power status estimation
In the case of, obtain accurate lithium battery energy state；Meanwhile battery discharge uses overall process electric discharge, and with two stage electricity
It can be fitted to obtain battery maximum available energy with thermal energy, traditional rated energy parameter is modified, estimation is further improved
Accuracy.
Detailed description of the invention
Fig. 1 is the flow chart of lithium battery energy state evaluation method of the present invention；
Fig. 2 is the connecting curve figure of SOE and SOC.
Specific embodiment
The contents of the present invention are described in further details with reference to the accompanying drawings and detailed description.It is understood that
It is that specific embodiment described herein is used only for explaining the present invention rather than limiting the invention.It further needs exist for illustrating
, for ease of description, only some but not all contents related to the present invention are shown in the drawings.
The present invention can reflect different discharge currents, varying environment by the parameter of the introducing off-energy in appraising model
Influence of the temperature to energy state is comprehensively considering what electric energy, thermal energy and off-energy influenced battery power status estimation
In the case of, obtain accurate lithium battery energy state.
The state that SOE is 100% is defined as battery fully charged state, namely under standard charging operating condition, after first constant current
The mode of constant pressure charge the battery until charging current be less than 0.02C, think at this time SOE be 100%；The shape that SOE is 0%
State is defined as battery maximum available energy EmaxThe state all consumed.
Embodiment 1
Referring to FIG. 1, a kind of lithium battery energy state evaluation method comprising following steps:
The energy of lithium battery discharge process is divided into electric energy, thermal energy and off-energy three parts by step 1, is considering electricity
On the basis of energy, thermal energy and off-energy, the mathematics appraising model of lithium battery energy state is established are as follows:
Wherein, SOE (k) is current time battery power status, and SOE (k-1) is last moment battery power status, tk、
tk-1Respectively current time and last moment time value, u are battery terminal voltage, and i is discharge current and takes positive value, and R is in battery
Resistance, EmaxFor battery maximum available energy, Eloss(i, T) is the off-energy of battery, Esum(i, T) be battery release electric energy and
The summation of thermal energy；
Wherein, in the present embodiment, state-of-charge SOC (0) battery initial energy state SOE (0) current by battery
It obtains, relational expression are as follows:
SOE (0)=m × SOC (0)+n (10)
M, n is the coefficient of coup of SOE and SOC curve.
Step 2, the electric energy and thermal energy parameter for using battery overall process electric discharge acquisition battery: with discharge cut-off voltage a1V,
Upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, discharge process is divided into two stages, and the first stage: battery is put non-standard
Electric discharge records the electric energy of first stage battery and the parameter of thermal energy up to reaching cut-off condition under electrician's condition；Second stage: first
After stage, battery standing restores to battery temperature to rated temperature, discharge to battery using standard electric discharge operating condition straight
To cut-off condition is reached, the electric energy and thermal energy parameter of second stage battery are recorded；
In the present embodiment, the detailed process of the first stage of the battery overall process electric discharge are as follows: in nominal environment temperature
Under, with discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, under different discharge-rates to battery into
Row electric discharge, electric discharge is until reach cut-off condition.
Step 3, using the parameter of above-mentioned electric energy and thermal energy, respectively obtain at least two groups battery the first rank during discharge
The electric energy W of section consumptione1(i, T) and thermal energy Wh1(i, T), and the electric energy W of discrete consuminge2(i, T) and thermal energy Wh2(i, T), then
We1(i, T)=u1×i1×Δt (2)
Wh1(i, T)=i1 2×R1×Δt (3)
And obtain the energy of battery first stage release:
We2(i, T)=u2×i2×Δt (5)
Wh2(i, T)=i2 2×R2×Δt (6)
And obtain the energy of battery second stage release:
Total property of battery are as follows: E (i, T)=Esum(i,T)+E'sum(i,T)
Wherein, Δ t=tk-tk-1, u1And i1Respectively the first stage when battery terminal voltage and discharge current, u2And i2Respectively
Battery terminal voltage and discharge current when for second stage, internal resistance of cell R are the summation of battery ohmic internal resistance and polarization resistance.
Step 4, using at least two groups E (i, T) data carry out Function Fitting, and obtain fitting function maximum value E (i,
T)max,
To which battery maximum available energy is are as follows: Emax=E (i, T)max (8)
Battery is in T moment off-energy known to then are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)；
Step 5 substitutes into formula (4), (8) and (9) in formula (1), and the energy state SOE (k) of T moment battery can be obtained.
Explain below by way of specific example to the above process: choosing a voltage rating/capacity is 3.2V/20Ah's
Ferric phosphate lithium cell is experimental subjects, is monitored by BMS to it, and it is 2V, upper limit cut-off temperature that its discharge cut-off voltage, which is arranged,
Degree is 60 DEG C, and allowing its maximum discharge current is 3C.
To obtain battery initial energy state SOE (0), need to determine the corresponding relationship of lithium battery SOE and SOC first,
Its method are as follows: use standard recharging methods charge the battery until reach fully charged state, it is specified that at this time battery SOE for
100%, SOC 100%.Then standard discharge operating condition under (discharge-rate 1/3C, environment temperature are 25 DEG C), to battery into
Row electric discharge is until reach electric discharge cut-off condition.Percentage processing is carried out by capacity to discharge process and energy datum, with SOC
As independent variable, SOE as dependent variable, the homologous thread of SOE and SOC is obtained as shown in Fig. 2, fitting obtains coefficient of coup m and is
1.0374, n be -3.7508.Therefore, it according to lithium battery SOC numerical value under current static condition, substitutes into initial energy state and calculates public affairs
Formula obtains the current value of primary power SOE, which represents percentages.Battery initial energy state is by standing shape
Battery charge state SOC under state is obtained, and effectively increases the estimation precision of battery power status SOE.
Then, it using discharge-rate 1/3C, 25 DEG C of environment temperature as standard electric discharge operating condition, is discharged using battery overall process
Method, discharge process are divided into two stages, the first stage: setting insulating box environment temperature is 25 DEG C, is 2V with discharge cut-off voltage,
Upper limit cut-off temperature is 60 DEG C as cut-off condition of discharging, and the electric discharge times of 2.5C, 2C, 1.5C, 1C, 0.5C, 1/3C is respectively adopted
Rate is discharged, and records the electric energy of first stage battery and the parameter of thermal energy；Second stage: after the first stage, battery
It stands, restores to battery temperature to 25 DEG C, electric discharge is carried out to battery until reaching cut-off condition using standard electric discharge operating condition, is recorded
The electric energy and thermal energy parameter of second stage battery.
Based on the experimental data that above-mentioned discharge process obtains, in conjunction with sampling time interval and internal resistance of cell R, (R takes battery
The summation of ohmic internal resistance and polarization resistance), according to formula:
We1(i, T)=u1×i1×Δt (2)
Wh1(i, T)=i1 2×R1×Δt (3)
Obtain the energy of battery first stage release:
According to formula:
We2(i, T)=u2×i2×Δt (5)
Wh2(i, T)=i2 2×R2×Δt (6)
Obtain the energy of battery second stage release:
Be added to the total property for obtaining battery with the energy that second stage discharges are as follows: E the above-mentioned battery first stage
(i, T)=Esum(i,T)+E'sum(i,T).Function Fitting is carried out using at least two groups E (i, T) data, and obtains fitting function
Maximum value E (i, T)max, so that battery maximum available energy is are as follows:
Emax=E (i, T)max (8)
In conjunction with obtained EmaxAnd E under any operating conditionsum(I,T1) numerical value, the operating condition corresponding battery damage is calculated
Lose ENERGY Eloss(I,T1), then know battery in T moment off-energy are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)
Initial energy state SOE (0), (4), (8) and (9) is substituted into formula (1), in integration time period section [tk,tk-1]
Voltage u, electric current i and temperature t interior, collected by BMS carry out real-time estimation to battery power status SOE, can be obtained
The energy state SOE (k) of T moment battery.
Embodiment 2
This embodiment differs from embodiment 1 in that in step 2, the first stage of the battery overall process electric discharge
Detailed process are as follows: under nominal discharge multiplying power, with discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C as electric discharge cut-off item
Part at different ambient temperatures discharges to battery, and electric discharge is until reach cut-off condition.
Explain below by way of specific example to the above process: choosing a voltage rating/capacity is 3.2V/20Ah's
Ferric phosphate lithium cell is experimental subjects, is monitored by BMS to it, and it is 2V, upper limit cut-off temperature that its discharge cut-off voltage, which is arranged,
Degree is 60 DEG C, and allowing its maximum discharge current is 3C.
To obtain battery initial energy state SOE (0), need to determine the corresponding relationship of lithium battery SOE and SOC first,
Its method are as follows: use standard recharging methods charge the battery until reach fully charged state, it is specified that at this time battery SOE for
100%, SOC 100%.Then standard discharge operating condition under (discharge-rate 1/3C, environment temperature are 25 DEG C), to battery into
Row electric discharge is until reach electric discharge cut-off condition.Percentage processing is carried out by capacity to discharge process and energy datum, with SOC
As independent variable, SOE as dependent variable, the homologous thread of SOE and SOC is obtained as shown in Fig. 2, fitting obtains coefficient of coup m and is
1.0374, n be -3.7508.Therefore, it according to lithium battery SOC numerical value under current static condition, substitutes into initial energy state and calculates public affairs
Formula obtains the current value of primary power SOE, which represents percentages.
Then, it using discharge-rate 1/3C, 25 DEG C of environment temperature as standard electric discharge operating condition, is discharged using battery overall process
Method, discharge process are divided into two stages, the first stage: the discharge-rate that battery is arranged is 3C, is 2V with discharge cut-off voltage, on
Limiting cut-off temperature is 60 DEG C as cut-off condition of discharging, be respectively adopted 35 DEG C, 25 DEG C, 15 DEG C, 5 DEG C, 0 DEG C of environment temperature carries out
Electric discharge, and record the electric energy of first stage battery and the parameter of thermal energy；Second stage: after the first stage, battery standing, to
Battery temperature restores to 25 DEG C, carries out electric discharge to battery until reaching cut-off condition using standard electric discharge operating condition, records second-order
The electric energy and thermal energy parameter of section battery.
Based on the experimental data that above-mentioned discharge process obtains, in conjunction with sampling time interval and internal resistance of cell R, (R takes battery
The summation of ohmic internal resistance and polarization resistance), according to formula:
We1(i, T)=u1×i1×Δt (2)
Wh1(i, T)=i1 2×R1×Δt (3)
Obtain the energy of battery first stage release:
According to formula:
We2(i, T)=u2×i2×Δt (5)
Wh2(i, T)=i2 2×R2×Δt (6)
Obtain the energy of battery second stage release:
Be added to the total property for obtaining battery with the energy that second stage discharges are as follows: E the above-mentioned battery first stage
(i, T)=Esum(i,T)+E'sum(i,T).Function Fitting is carried out using at least two groups E (i, T) data, and obtains fitting function
Maximum value E (i, T)max, so that battery maximum available energy is are as follows:
Emax=E (i, T)max (8)
In conjunction with obtained EmaxAnd E under any operating conditionsum(I,T1) numerical value, the operating condition corresponding battery damage is calculated
Lose ENERGY Eloss(I,T1), then know battery in T moment off-energy are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)
Initial energy state SOE (0), (4), (8) and (9) is substituted into formula (1), in integration time period section [tk,tk-1]
Voltage u, electric current i and temperature t interior, collected by BMS carry out real-time estimation to battery power status SOE, can be obtained
The energy state SOE (k) of T moment battery.
Embodiment 3
It is unlike the first embodiment: obtaining the electric energy and heat of battery in the step 2 using battery overall process electric discharge
Energy parameter: the electric energy and thermal energy gain of parameter mode of first group of battery are as follows: with discharge cut-off voltage a1V, upper limit cut-off temperature b1℃
As electric discharge cut-off condition, discharge process is divided into two stages, the first stage: at a temperature of nominal environment, in different electric discharges times
It discharges under rate battery, electric discharge records the electric energy of first stage battery and the parameter of thermal energy up to reaching cut-off condition；The
Two-stage: after the first stage, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition to electricity
Pond carries out electric discharge until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery；
The electric energy and thermal energy gain of parameter mode of second group of battery are as follows: with discharge cut-off voltage a1V, upper limit cut-off temperature b1
DEG C as electric discharge cut-off condition, discharge process is divided into two stages, the first stage: under nominal discharge multiplying power, in varying environment
At a temperature of discharge battery, electric discharge records the electric energy of first stage battery and the parameter of thermal energy until reach cut-off condition；
Second stage: after the first stage, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition pair
Battery carries out electric discharge until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery.
The electric energy of two groups of batteries and thermal energy parameter under Bu Tong non-standard electric discharge operating condition respectively by obtaining, then using upper
It states two groups of E (i, T) data and carries out Function Fitting, and obtain the maximum value E (i, T) of fitting functionmax, the battery obtained at this time is most
Available energy is more accurate by the battery maximum available energy being fitted under single non-standard electric discharge operating condition than only.
Explain below by way of specific example to the above process: choosing a voltage rating/capacity is 3.2V/20Ah's
Ferric phosphate lithium cell is experimental subjects, is monitored by BMS to it, and it is 2V, upper limit cut-off temperature that its discharge cut-off voltage, which is arranged,
Degree is 60 DEG C, and allowing its maximum discharge current is 3C.
To obtain battery initial energy state SOE (0), need to determine the corresponding relationship of lithium battery SOE and SOC first,
Its method are as follows: use standard recharging methods charge the battery until reach fully charged state, it is specified that at this time battery SOE for
100%, SOC 100%.Then standard discharge operating condition under (discharge-rate 1/3C, environment temperature are 25 DEG C), to battery into
Row electric discharge is until reach electric discharge cut-off condition.Percentage processing is carried out by capacity to discharge process and energy datum, with SOC
As independent variable, SOE as dependent variable, the homologous thread of SOE and SOC is obtained as shown in Fig. 2, fitting obtains coefficient of coup m and is
1.0374, n be -3.7508.Therefore, it according to lithium battery SOC numerical value under current static condition, substitutes into initial energy state and calculates public affairs
Formula obtains the current value of primary power SOE, which represents percentages.
Then, the electric energy and thermal energy gain of parameter mode of first group of battery are as follows: with 25 DEG C of discharge-rate 1/3C, environment temperature
As standard electric discharge operating condition, using battery overall process electric discharge, discharge process is divided into two stages, the first stage: setting constant temperature
Case environment temperature is 25 DEG C, is 2V with discharge cut-off voltage, and upper limit cut-off temperature is 60 DEG C as cut-off condition of discharging, and is adopted respectively
It is discharged with the discharge-rate of 2.5C, 2C, 1.5C, 1C, 0.5C, 1/3C, and records the electric energy and thermal energy of first stage battery
Parameter；Second stage: after the first stage, battery standing restores to battery temperature to 25 DEG C, using standard electric discharge operating condition
Electric discharge is carried out to battery until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery.
The electric energy and thermal energy gain of parameter mode of second group of battery are as follows: using discharge-rate 1/3C, 25 DEG C of environment temperature as
Standard electric discharge operating condition, using battery overall process electric discharge, discharge process is divided into two stages, and putting for battery the first stage: is arranged
Electric multiplying power is 3C, is 2V with discharge cut-off voltage, and upper limit cut-off temperature is 60 DEG C as cut-off condition of discharging, and is respectively adopted 35
DEG C, 25 DEG C, 15 DEG C, 5 DEG C, 0 DEG C of environment temperature discharges, and records the electric energy of first stage battery and the parameter of thermal energy；
Second stage: after the first stage, battery standing restores to battery temperature to 25 DEG C, using standard electric discharge operating condition to battery
Electric discharge is carried out until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery.
Based on the experimental data that above-mentioned discharge process obtains, in conjunction with sampling time interval and internal resistance of cell R, (R takes battery
The summation of ohmic internal resistance and polarization resistance), according to formula:
We1(i, T)=u1×i1×Δt (2)
Wh1(i, T)=i1 2×R1×Δt (3)
Obtain the energy of battery first stage release:
According to formula:
We2(i, T)=u2×i2×Δt (5)
Wh2(i, T)=i2 2×R2×Δt (6)
Obtain the energy of battery second stage release:
Be added to the total property for obtaining battery with the energy that second stage discharges are as follows: E the above-mentioned battery first stage
(i, T)=Esum(i,T)+E'sum(i,T).Function Fitting is carried out using two groups of E (i, T) data, and obtains the maximum of fitting function
Value E (i, T)max, so that battery maximum available energy is are as follows:
Emax=E (i, T)max (8)
In conjunction with obtained EmaxAnd E under any operating conditionsum(I,T1) numerical value, the operating condition corresponding battery damage is calculated
Lose ENERGY Eloss(I,T1), then know battery in T moment off-energy are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)
Initial energy state SOE (0), (4), (8) and (9) is substituted into formula (1), in integration time period section [tk,tk-1]
Voltage u, electric current i and temperature t interior, collected by BMS carry out real-time estimation to battery power status SOE, can be obtained
The energy state SOE (k) of T moment battery.
Above-described embodiment is only to illustrate this patent and not limits technical solution described in this patent；Therefore, although
This specification has been carried out detailed description to this patent referring to above-mentioned each embodiment, still, the ordinary skill of this field
Personnel should be appreciated that and still can be modified or replaced equivalently to this patent；And all do not depart from this patent spirit and
The technical solution and its improvement of range, should all cover in the scope of the claims of this patent.
Claims (6)
1. a kind of lithium battery energy state evaluation method, it is characterised in that the following steps are included:
The energy of lithium battery discharge process is divided into electric energy, thermal energy and off-energy three parts by step 1, is considering electric energy, heat
The mathematics appraising model of lithium battery energy state can be established on the basis of off-energy are as follows:
Wherein, SOE (k) is current time battery power status, and SOE (k-1) is last moment battery power status, tk、tk-1Point
Not Wei current time and last moment time value, u is battery terminal voltage, and i is discharge current and takes positive value, and R is the internal resistance of cell,
EmaxFor battery maximum available energy, Eloss(i, T) is the off-energy of battery, Esum(i, T) is the electric energy and heat of battery release
The summation of energy；
Step 2, the electric energy and thermal energy parameter for using battery overall process electric discharge acquisition battery: with discharge cut-off voltage a1V, the upper limit
Cut-off temperature b1DEG C as electric discharge cut-off condition, discharge process is divided into two stages, and the first stage: battery is in non-standard electric discharge work
Electric discharge records the electric energy of first stage battery and the parameter of thermal energy up to reaching cut-off condition under condition；Second stage: first stage
After, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition discharge battery until reaching
To cut-off condition, the electric energy and thermal energy parameter of second stage battery are recorded；
Step 3, using the parameter of above-mentioned electric energy and thermal energy, respectively obtaining at least two groups battery, the first stage disappears during discharge
The electric energy W of consumptione1(i, T) and thermal energy Wh1(i, T), the electric energy W of second stage consumptione2(i, T) and thermal energy Wh2(i, T), then
We1(i, T)=u1×i1×Δt (2)；
Wh1(i, T)=i1 2×R1×Δt (3)；
And obtain the energy of battery first stage release:
We2(i, T)=u2×i2×Δt (5)；
Wh2(i, T)=i2 2×R2×Δt (6)；
And obtain the energy of battery second stage release:
Total property of battery are as follows: E (i, T)=Esum(i,T)+E'sum(i,T)
Wherein, Δ t=tk-tk-1, u1And i1Respectively the first stage when battery terminal voltage and discharge current, u2And i2Respectively
Battery terminal voltage and discharge current when the two-stage, internal resistance of cell R are the summation of battery ohmic internal resistance and polarization resistance；
Step 4 carries out Function Fitting using at least two groups E (i, T) data, and obtains the maximum value E (i, T) of fitting functionmax,
To which battery maximum available energy is are as follows: Emax=E (i, T)max(8)；
Battery is in T moment off-energy known to then are as follows:
Eloss(I,T1)=Emax-Esum(I,T1) (9)；
Step 5 substitutes into formula (4), (8) and (9) in formula (1), and the energy state SOE (k) of T moment battery can be obtained.
2. lithium battery energy state evaluation method according to claim 1, it is characterised in that: the state that SOE is 100% is fixed
Justice is battery fully charged state, namely under standard charging operating condition, is charged the battery directly by the way of constant pressure after first constant current
It is less than 0.02C to charging current, thinks that SOE is 100% at this time；The state that SOE is 0% is defined as battery maximum available energy
EmaxThe state all consumed.
3. lithium battery energy state evaluation method according to claim 1, it is characterised in that: battery initial energy state
SOE (0) is obtained by the current state-of-charge SOC (0) of battery, relational expression are as follows:
SOE (0)=m × SOC (0)+n (10)；
Wherein, m, n are the coefficient of coup of SOE and SOC curve.
4. lithium battery energy state evaluation method according to claim 1, it is characterised in that: the battery overall process electric discharge
First stage detailed process are as follows: at a temperature of nominal environment, discharge under different discharge-rates battery, electric discharge is straight
To reaching cut-off condition.
5. lithium battery energy state evaluation method according to claim 1, it is characterised in that: the battery overall process electric discharge
First stage detailed process are as follows: under nominal discharge multiplying power, discharge at different ambient temperatures battery, electric discharge is straight
To reaching cut-off condition.
6. lithium battery energy state evaluation method according to claim 1, it is characterised in that: using electricity in the step 2
The electric energy and thermal energy parameter of pond overall process electric discharge acquisition battery: the electric energy and thermal energy gain of parameter mode of first group of battery are as follows:
With discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C as electric discharge cut-off condition, discharge process is divided into two stages, the first rank
Section: at a temperature of nominal environment, discharging to battery under different discharge-rates, and electric discharge is recorded up to reaching cut-off condition
The electric energy of first stage battery and the parameter of thermal energy；Second stage: after the first stage, battery standing is extensive to battery temperature
Again to rated temperature, electric discharge is carried out to battery until reaching cut-off condition using standard electric discharge operating condition, records second stage battery
Electric energy and thermal energy parameter；
The electric energy and thermal energy gain of parameter mode of second group of battery are as follows: with discharge cut-off voltage a1V, upper limit cut-off temperature b1DEG C make
For cut-off condition of discharging, discharge process is divided into two stages, the first stage: under nominal discharge multiplying power, in varying environment temperature
Under discharge battery, electric discharge records the electric energy of first stage battery and the parameter of thermal energy until reach cut-off condition；Second
Stage: after the first stage, battery standing restores to battery temperature to rated temperature, using standard electric discharge operating condition to battery
Electric discharge is carried out until reaching cut-off condition, records the electric energy and thermal energy parameter of second stage battery.
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