CN105759213A - Method for measuring storage battery residual capacity SOC - Google Patents

Abstract

The invention provides an accurate and convenient method for measuring storage battery residual capacity SOC. The method comprises the steps that a. initial residual capacity SOC<0> of a storage battery is determined; b. working current of the storage battery in the working time is measured in real time; c. residual capacity SOC(t) of the storage battery after continuous working time t is calculated according to the formula 1 (which is expressed in the specification), wherein eta<age> refers to the attenuation coefficient of the storage battery, C<n> refers to the rated capacity of the storage battery, eta<e> refers to the current efficiency coefficient, eta refers to the correction coefficient of the actual capacity of the storage battery, and t refers to continuous working time of the storage battery; and d. after the end of working of the storage battery, eta=1, and the SOC value calculated according to the formula 1 is the SOC value after the end of working of the storage battery of the time, wherein eta<age> refers to the specific value of the actual capacity to the rated capacity of the storage battery after N times of cyclic charge and discharge of the storage battery, C<n> refers to the electric energy which can be discharged by charging to cut-off voltage, eta<e> refers to the specific value of actual current used for electrode reaction to external current in charge and discharge of the storage battery, and eta refers to the specific value of actual capacity which can be charged or discharged by the storage battery to the rated capacity under the actual use state.

Description

A kind of method measuring remaining battery capacity SOC

Technical field

The present invention relates to a kind of battery management system, relate more specifically to the measuring method of a kind of remaining battery capacity (SOC), belong to cell art.

Background technology

Battery is the device that chemical energy is converted to electric energy, is also called electrochmical power source.The active substance of inside battery is regenerated by the mode that can pass through to charge after battery discharge, is chemical energy electrical power storage, releases electric energy in if desired again.This kind of battery is called accumulator, also referred to as secondary cell.

Accumulator, as energy storage device, no matter at sphere of life or at production field, suffers from purposes widely, little mobile phone in people's hands, notebook computer, arrive greatly spaceship, foreign-going ship, all not lacking accumulator, therefore accumulator suffers from extremely important status in life and production field.

Accumulator is of a great variety, at present application at most and technology the most ripe surely belong to lead-acid accumulator, owing to the specific energy of lead-acid accumulator is low, and lead contamination problem cannot effectively be solved, thus lead-acid accumulator is replaced rapidly.NI-G, nickel-hydrogen accumulator were once considered as most possibly replace lead-acid accumulator and obtain flourish.But, along with the development of lithium ion battery technology, after solving the safety problem of self, surmount rapidly NI-G, nickel-hydrogen accumulator, become the Developing impetus the most violent, the accumulator that market growth rate is the fastest, there is greatly the trend comprehensively replacing lead-acid accumulator.

Lithium ion battery includes liquid lithium ionic cell (LIB) and polymer Li-ion battery (PLB).It is big that lithium ion battery has energy density, average output voltage is high, and self discharge is little, it does not have memory effect, operating temperature range width, cycle performance is superior, can fast charging and discharging, charge efficiency is high, output is big, long service life, without advantages such as poisonous and harmful substances, becomes the accumulator that current development prospect is the most wide.Especially the succeeding in developing of lithium-ion-power cell so that it is become the green energy resource that new-energy automobile is first-selected, thus have stimulated the fast development of lithium ion battery further.

No matter which kind of accumulator, at its duration of work, the management to accumulator is requisite, and correct battery management can improve the service efficiency of accumulator, increases the service life, and ensures the use safety of accumulator.Along with the development of electronics technology and chip technology, the management of accumulator has been realized computer and has automatically managed, i.e. battery management system (BMS).The Main Function of BMS is intelligent management and safeguards each secondary battery unit, it is prevented that overcharge or overdischarge occurs in accumulator, extends the service life of accumulator, the state of monitoring accumulator.Concrete function includes: the measurement of accumulator voltage, the balancing energy between cell, the measurement of accumulator output or charging current, the estimation of storage battery charge state (SOC), the duty of kinetic measurement accumulator, data record and analysis, realtime curve, external communication etc..In these functions, the estimation of SOC is the core of BMS.Especially lithium-ion-power cell, the accurately estimation of SOC is directly connected to safety that lithium ion battery uses, the performance of dynamical system and life-span, thus determining the performance of new-energy automobile.

SOC is called the state-of-charge of accumulator, is also called residual capacity, and sign is the number of accumulator dump energy.SOC commonly used at present is defined as: accumulator under certain discharge-rate, the ratio of rated capacity under dump energy and the same terms, popular understanding can define with following formula:

Owing to the influence factor of accumulator SOC estimation is a lot of and relation is complicated, existing researcher in this field proposes a lot of computational methods at present, mainly has open-circuit voltage method, ampere-hour integration method, internal resistance method, load method, neural network, Kalman filtering method, discharge test method etc..In these methods, open-circuit voltage method and discharge test method can not when battery-operated on-line real-time measuremen；Internal resistance method is easy to be subject to the interference of each side so that measurement result is not accurate enough；Neural network and Kalman filtering method are due to also immature, and algorithm is complicated, and hardware requirement height is actually rare in actual applications.Ampere-hour integration method is by measuring the electric current of load and the time being integrated calculating SOC, easy to use, and algorithmic stability becomes the SOC computational methods employed up in current all kinds of BMS system.

The current commonly used following operation principle model of ampere-hour integration method is calculated:

$SOC\left(t\right)={\mathrm{SOC}}_0-\frac{{\&Integral;}_0^{t}i\left(\mathrm{\&tau;}\right)d\mathrm{\&tau;}}{C_n}\&times;100\%---\left(6\right)$

In formula: the SOC value after SOC (t) accumulator continuous working period t, %；

SOC₀Initial residual capacity when accumulator is started working, %；

C_nThe rated capacity of accumulator, Ah；

The real time operation electric current (discharge condition is just, charged state is negative) of i (τ) accumulator, A.

Ampere-hour integration method measures the electric current being filled with accumulator or releasing from accumulator in real time, the integration of time is calculated the electricity being filled with in real time or releasing by real-time current, thus providing the dump energy of accumulator any time.Compared with the computational methods of other several SOC, it is achieved get up simpler, it is easy to monitor in real time.

From the operation principle of this ampere-hour integration method, if current measurement is accurate, and the residual capacity of accumulator when being completely filled with electricity is defined as 100%, then the SOC of any time should be estimated exactly.

But, this is a kind of perfect condition simply, and in actually used process, situation is sufficiently complex, and the result error causing calculating is very big.The technical staff of field of batteries is clear, and same accumulator is under different duties, it is possible to the ability being charged into or releasing electricity is different.Rated capacity simply records when specifying for one, and the capability value of the accumulator declared by manufacturer.When actual service conditions is different from the rated condition measuring rated capacity, the ability that accumulator could be charged into or release electricity is just different, say, that the actual capacity of accumulator is inequal with its rated capacity.Formula (6) does not consider this influence factor, and therefore widespread practice is to introduce coulombic efficiency coefficient η in formula (6) at present_εIt is modified.

$SOS\left(t\right)={\mathrm{SOC}}_0-\frac{{\&Integral;}_0^t{\mathrm{\&eta;}}_{\mathrm{\&epsiv;}}I\left(\mathrm{\&tau;}\right)d\mathrm{\&tau;}}{L_7}\&times;100\%---\left(7\right)$

In formula: η_εThe coulombic efficiency coefficient of accumulator.

The coulombic efficiency coefficient η of accumulator_εWhat represent is under actual working state, the actual capacity that accumulator can be charged into or release correction factor compared with rated capacity.It is relevant with charging and discharging currents, operating temperature, cycle-index etc..

In existing technology, even if introducing coulombic efficiency coefficient to revise the computing formula of ampere-hour integration, but still there is bigger deviation in actual use.For this deviation, it is common to think to cause due to the reason of following two aspects: one be the determination problem of initial value for integral；Another is to there is the problem that current measurement errors causes integral process error accumulation.

Multiple technologies currently also being had been disclosed to correct this deviation, most readily achieved also most widely used is with open-circuit voltage (OCV) correction method, it with ampere-hour integration method with the use of, it is possible to the computational accuracy of accumulator SOC is controlled within 10%.

So-called battery open-circuit voltage OCV refers to terminal voltage when reaching stable when accumulator exports without extrinsic current or inputs (i.e. open circuit).There is corresponding relation in accumulator SOC and the OCV of all kinds.As long as the OCV of accumulator can accurately be measured, it is possible to accurately determine the SOC of accumulator.But the OCV of accumulator is an Index For Steady-state, after accumulator quits work, to reach stable state need the longer time, general no less than 1 hour, therefore OCV may not apply to the real-time SOC measurement of accumulator, and when accumulator time of repose is inadequate, there is bigger deviation with its OCV in the terminal voltage recorded, corrects SOC with this and necessarily bring bigger error.For lithium ion battery, there is a further problem, it is simply that OCV～SOC curve of lithium ion battery exists a shallower region of ratio, when the SOC of accumulator is in this region, the slight error that OCV measures all can bring great SOC deviation.

Summary of the invention

The invention solves the problems that there is battery remaining power SOC in existing ampere-hour integration method technology calculates the problem that error is big and there is error accumulation.A kind of method measuring remaining battery capacity SOC of the present invention is provided for this, adopts this method can improve the computational accuracy of ampere-hour integration method, and meet the practical working situation of accumulator, thus reducing the calculating error of ampere-hour integration method.

For solving the problems referred to above, the technical solution used in the present invention its be characterized in that and measure the residual capacity SOC (t) after accumulator continuous working period t according to the following steps:

A. initial residual capacity SOC during battery-operated is determined₀；

B. measure the operating current i (τ) during battery-operated in real time, during electric discharge be on the occasion of, be negative value during charging；

C. by the residual capacity SOC (t) after formula calculated below (1) calculating accumulator continuous working period t:

$SOC\left(t\right)=\frac{\mathrm{\&eta;}\&CenterDot;(\frac{{\mathrm{SOC}}_0}{100}\&CenterDot;{\mathrm{\&eta;}}_{age}\&CenterDot;C_n-{\&Integral;}_0^t{\mathrm{\&eta;}}_{e}i(\mathrm{\&tau;})d\mathrm{\&tau;})}{{\mathrm{\&eta;}}_{age}\&CenterDot;C_n}\&times;100\%---\left(1\right)$

In formula: η_ageThe attenuation quotient of accumulator；

C_nThe rated capacity of accumulator, Ah；

η_eCurrent efficiency coefficient；

The correction coefficient of η storage battery practical capacity；

The time of t accumulator continuous firing, s.

D. after battery-operated terminates, take η=1, be recorded as the SOC value after this battery-operated terminates by computing formula (1) calculated SOC value；

The attenuation quotient η of described accumulator_ageAfter referring to accumulator cycle charge-discharge n times, the ratio of storage battery practical capacity and rated capacity；The rated capacity C of described accumulator_nRefer to accumulator by the charge condition of regulation fully charged after, then by the discharging condition electric discharge of regulation until the electricity can released when being discharged to blanking voltage；Described current efficiency coefficient η_eIt is actually used in the electric current of electrode reaction and the ratio of extrinsic current, less than or equal to 1 during charging, be more than or equal to 1 during electric discharge when referring to accumulator cell charging and discharging；The correction coefficient η of described storage battery practical capacity refers to the ratio of accumulator can be charged into or release under real use state actual capacity and rated capacity.

Described initial residual capacity SOC₀Determined by one of following situation:

A. when described accumulator by regulation charging system fully charged time, SOC₀=100%；

B. when described accumulator stand when extrinsic current is 01 little time more than time, measure accumulator open-circuit voltage OCV, determine SOC according to OCV～SOC relation curve of accumulator₀Value；

C. in addition to the conditions already mentioned, SOC₀=SOC_prev, SOC in formula_prevThe SOC value recorded when being accumulator last time end-of-job.

The attenuation quotient η of described accumulator_ageObtained by following steps test:

A. by known nominal capacity C_nAccumulator cycle charge-discharge n times；

B. the actual capacity C (N) of the accumulator after cycle charge-discharge n times is obtained by the method for testing measurement of battery rating；

C. the accumulator attenuation quotient η after cycle charge-discharge n times_age(N) obtained by following calculating:

${\mathrm{\&eta;}}_{age}\left(N\right)=\frac{C\left(N\right)}{C_n}---\left(2\right)$

D. choose different N value repeat the above steps, obtain the η under a series of different N value_age(N) value mapping, obtains η_age(N) relation curve of～N；

E. described η is looked into_age(N) relation curve of～N, obtains the accumulator attenuation quotient η after Arbitrary cyclic discharge and recharge number of times_age。

The correction coefficient η of described storage battery practical capacity is calculated as follows according to actually measured temperature and charging and discharging currents:

η=η_T·η_C(3)

In formula: η_TCorrection coefficient due to the storage battery practical capacity that variations in temperature causes；

η_CThe accumulator actual capacity under different charge-discharge magnifications capacity correction coefficient compared with rated capacity.

Described in computing formula (1), the correction coefficient η of storage battery practical capacity determines by the following method:

A. according to the temperature recorded in real time and charging and discharging currents, calculate by formula (3) and obtain real-time correction coefficient η (t)；

B. the average correction coefficient in the set time section before current time is calculated

C. by currently real-time calculated η_NOWWith average correction coefficientCompare, ifThen $\mathrm{\&eta;}=\stackrel{\&OverBar;}{\mathrm{\&eta;}};$ If ${\mathrm{\&eta;}}_{\mathrm{NOW}}\&GreaterEqual;\stackrel{\&OverBar;}{\mathrm{\&eta;}},$ Then η=η_NOW,

The time span of described set time section is between 1 second to 3 hours, described average correction coefficientCalculating comprise the real time correction coefficient η of current time_NOW。

When described accumulator is in charged state, take η=1.

When being lithium ion battery for described accumulator, take η_e=1, described lithium ion battery is liquid lithium ionic cell or polymer Li-ion battery.

The described storage battery practical capacity correction coefficient η that current time records in real time_NOWCompared with the η value that previous moment uses in computing formula (1), when amplitude of variation is less than or equal to 5%, the η value in computing formula (1) is constant.

Described η_TCalculated by following formula:

η_TIn=1-α (25-T) (4) formula: the temperature coefficient of α accumulator, 1/ DEG C；

The operating temperature of T accumulator, DEG C.

The present invention operation principle according to accumulator, corresponding relation between the variable quantity of internal storage battery active substance and externally measured electricity, re-establish the concept of accumulator SOC and thus proposed new ampere-hour integration method computing formula, with this computing formula for core, in conjunction with conventional measurement technology, it is proposed to a kind of method measuring accumulator remaining capacity SOC.The method more meets the practical working situation of accumulator, substantially increases the computational accuracy of ampere-hour integration method.The method is combined with open-circuit voltage correction method, it is possible to reduce the calculating error of accumulator SOC to less than 3%.

Accompanying drawing explanation

Fig. 1 is the fundamental diagram of lithium ion battery；

Fig. 2 is OCV～SOC graph of relation of lithium ion battery；

The graph of relation of the ratio of discharge capacity and rated capacity and temperature when Fig. 3 is lithium-ion electric tank discharge training rate 1C；

Fig. 4 is the terminal voltage capacity discharge curve under lithium ion battery difference discharge-rate；

Fig. 5 is the graph of relation of the actual capacity correction coefficient under lithium ion battery difference discharge-rate and discharge-rate；

Fig. 6 is the lithium ion battery attenuation quotient cycle-index curve chart that experiment records；

Fig. 7 is lithium ion battery intermittent discharge experiment discharge current time service curve chart, and in figure, 1C, 2C, 3C represent discharge-rate；

Fig. 8 is that the present invention represents discharge-rate with 1C, 2C, 3C in prior art measurement remaining battery capacity Comparative result figure, figure.

Below in conjunction with accompanying drawing, further illustrate the measuring method of accumulator SOC proposed by the invention.

Accumulator is the device that electric energy converts mutually with chemical energy, is mainly made up of positive pole, negative pole, electrolyte, barrier film and shell etc..Positive pole and negative pole have been respectively coated with positive active material and negative electrode active material.Positive active material and what negative electrode active material always occurred in groups, both can not be split and are optionally combined into new accumulator.Positive active material such as lead-acid accumulator is PbO₂, negative electrode active material is Pb.Electric energy and chemical energy mutually convert what the electrode reaction being exactly based on these active substances realized in accumulator:

Positive pole:

Negative pole:

Cadmium-nickel storage cell, nickel-hydrogen accumulator, sodium sulfur storage battery, lithium-sulfur battery, full vanadium accumulator, zinc bromine accumulator etc. are all similar, and simply the active substance of positive and negative electrode is different, and the electrode reaction of generation is different.

But lithium ion battery and above-mentioned accumulator are slightly different, its happens is that Li⁺In the deintercalation process of both positive and negative polarity, shown in accompanying drawing 1 be positive active material is LiCoO₂；Negative electrode active material is the fundamental diagram of the lithium ion battery of porous carbonaceous.In figure, in external circuit, electronics flow direction is in opposite direction with actual current, and inside battery Li⁺Moving direction is identical with the sense of current.Lithium ion battery positive pole when charging occurs de-lithium reaction to generate Li⁺Move to negative pole to embed in negative material；Discharge process is then contrary.Concrete electrode process can be expressed as:

Positive pole:

Negative pole:

There it can be seen that no matter which kind of accumulator, when charging, the electronics flowing into negative pole that charger provides is all negative electrode active material by negative pole sorption enhanced, and positive pole then discharges the electronics of equal number and supplements and recharge electrical equipment, and itself is converted into positive active material；And when discharging, negative electrode active material discharges after electronics flows through external circuit and flows into positive pole, absorbed by positive active material.Therefore, no matter charge or discharge, external circuit flows in or out the electronics of accumulator all must have the positive active material of corresponding amount and negative electrode active material to participate in reaction, flow through the electron amount of external circuit and internal storage battery and participate in the positive active material of electrode reaction and negative electrode active material exists corresponding relation, this corresponding relation only with the activated species of accumulator about and unrelated with the use condition of accumulator.It is to say, accumulator is released or is filled with how many electricity, it is necessary to having the electrode active material of corresponding amount to participate in reaction, this is unrelated with the condition of use.

Therefore, basically, the active volume that accumulator is total is to be determined by the total amount of the active substance of electrode.It is known that positive pole reaction and negative reaction are a pair simultaneous conjugation reactions, more precisely, the capacity of accumulator is by measuring few side's decision in positive active material and negative electrode active material.In general, the amount of negative electrode active material is always more than positive active material, and the total active volume of accumulator is determined by the amount of positive active material.In the following partial content of the present invention, described active substance refers to the positive active material of accumulator.

In the actually used process of accumulator, owing to the existence of polarization phenomena (including activation polarization, concentration polarization and ohmic polarization) makes the active substance of electrode all for participating in electrode reaction, accumulator otherwise can not can cause the infringement that cannot recover.Therefore, the amount of actual available active substance is always less than total Useful active amount of substance, and we can be referred to as the ratio of both effective rate of utilization of active substance.This effective rate of utilization is just closely related with the use condition of accumulator, and topmost influence factor is exactly discharge rate and uses temperature.

As seen from the above analysis, ampere-hour integration method in existing accumulator SOC computational methods, simply from the angle of electricity observe different uses the accumulator electricity difference that can release or be filled with, thus in the electricity that current integration obtains, introduce coulombic efficiency coefficient carry out the electrical phenomena that matching is observed, it is clear that this practical work process with accumulator does not also correspond.

From the operation principle of accumulator, we can clearly follow that such conclusion: the effective rate of utilization that the capacity under accumulator actual operating conditions is the total amount with active substance and active substance is relevant, the measurer of the active substance flowing through the electricity in external circuit and participation electrode reaction has corresponding relation, and this corresponding relation is unrelated with the working condition of accumulator.

It follows that we are just from the operation principle of accumulator, redefine the concept of accumulator remaining capacity SOC the computing formula of the ampere-hour integration method calculating accumulator SOC made new advances that thus derives.

Saying from the most basic definition, SOC is the ratio of residue available power and total available power, as shown in formula (5).From the operation principle of accumulator it can be seen that the amount of the electricity of internal storage battery storage and electrode active material has corresponding relation, therefore SOC may be defined as again the ratio of residue Useful active amount of substance and total Useful active amount of substance:

The total Useful active amount of substance of accumulator after the battery lead plate of accumulator completes just it has been determined that and cannot be carried out measuring after accumulator completes.In actual use, what we generally surveyed is the capacity of its electric discharge.In view of the capacity of accumulator exists, with the amount of its active substance, the corresponding relation determined, we just characterize the amount of the active substance of accumulator by the discharge capacity of accumulator.But, the discharge capacity that under different test conditions, accumulator records is different, it is therefore necessary to determining that the battery discharging capacity recorded under the measuring condition of a standard is to characterize the Useful active amount of substance that accumulator is total, this is called rated capacity.

Rated capacity is generally all specified by corresponding standard or accumulator manufacturer specifies in technological document.As IEC standard specifies that the rated capacity of NI-G and nickel-hydrogen accumulator is under 20 DEG C ± 5 DEG C environment, the electricity can released when being discharged to 1.0V with 0.2C again after charging 16 hours with 0.1C.For another example, for lithium ion battery general provision under normal temperature condition, with 1C constant-current charge to charge cutoff voltage, then turn to constant-voltage charge, stopping when continuing to charge to charging current less than 0.05C, the electricity released time then with 0.2C current discharge to discharge cut-off voltage is its rated capacity.The rated capacity of accumulator is with C_nRepresenting, unit is Ah or mAh.

The rated capacity of accumulator is a nominal value, and total active volume is also not exactly equal to rated capacity.This is mainly manifested in two aspects: on the one hand, in order to improve service lifetime of accumulator, the capacity of accumulator often have during fabrication 10% more than needed, say, that the actual capacity of new accumulator is usually 1.1 times of rated capacity.On the other hand, accumulator is in recycling process, and irreversible side reaction inevitably occurs electrode, causes electrode active material irreversibly to be lost, and the capacity showing as accumulator is constantly decayed.Therefore, it is necessary to introduce the attenuation quotient η of an accumulator_age, use η_age·C_nRepresent the Useful active amount of substance that current accumulator is total.That is:

Total Useful active amount of substance=η_age·C_n(9)

Usually, η is worked as_ageDuring less than 0.8, mean that accumulator has reached service life, do not continue to use.So η_ageSpan be generally 0.8～1.1.

The attenuation quotient η of accumulator_ageGenerally provided by accumulator manufacturer, if manufacturer is not provided that, it is also possible to measure by experiment.Concrete method of testing is as follows:

A. it is C by known nominal capacity_nAccumulator is cycle charge-discharge n times on storage battery integrated tester, and discharge and recharge condition should simulate actually used operating mode；

B. the actual capacity C (N) after cycle charge-discharge n times is recorded by the method for testing of battery rating；

C. the attenuation quotient η after obtaining cycle charge-discharge n times is calculated by formula (2)_age(N)；

D. choose different N value repeat the above steps, obtain the η under a series of different N value_age(N) value mapping, obtains η_age(N) relation curve of～N；

E. above-mentioned η is compareed_age(N) relation curve of～N, can obtain the accumulator attenuation quotient η after Arbitrary cyclic discharge and recharge number of times_age。

Due to η_age(N) very little with N change, in order to simplify calculating, it is possible to η_age(N) segmentation value is carried out.As for high performance lithium ion battery, η_age(N) segmentation value in the following manner is rational.

${\mathrm{\&eta;}}_{age}\left(N\right)=\left\{\begin{array}{c}\mathrm{1.1.....}N\&le;50\\ \mathrm{1.05...50}<N\&le;100\\ \mathrm{1.0....100}<N\&le;500\\ \mathrm{0.98...500}<N\&le;1000\\ \mathrm{0.95...1000}<N\&le;1500\\ \mathrm{0.9.....}N>1500\end{array}\right.$

It should be noted that different accumulator, η_age(N) segmentation obtaining value method is entirely different.

When being aware of the Useful active amount of substance that accumulator is total, then the SOC of calculating accumulator, it is only necessary to calculating accumulator operationally between after t, there remains the amount of how many available active substance.

If we know that the residual capacity SOC at battery-operated initial stage₀, thenJust can be expressed as the Useful active amount of substance in battery-operated preliminary electrode.

The residual capacity SOC at battery-operated initial stage₀Can be determined by one of in the following manner:

A. when accumulator according to regulation charging system fully charged time, SOC₀=100%.

B. after accumulator quits work, time of repose was more than 1 hour, it is possible to by measuring the open-circuit voltage OCV of accumulator, determine SOC according to the relation curve of the OCV～SOC looking into accumulator₀Value.

C. except above-mentioned two situations, SOC₀=SOC_prev, SOC_prevThe SOC value recorded when representing accumulator last time end-of-job.

Different accumulator has different charging systems, is generally all specified according to the service condition of user by accumulator manufacturer.Such as the charging system combined with constant voltage frequently with constant current for the lithium ion battery of quickly-chargeable, first with the big electric current quick charge of 3C to the charge cutoff voltage of lithium ion battery, then turning to constant-voltage charge, charging current constantly reduces, when charging current is decreased to 0.05C, charging terminates.Now just specify SOC₀=100%.

The open-circuit voltage OCV and its SOC of accumulator also exist corresponding relation, by measuring the open-circuit voltage OCV of accumulator, compare OCV～SOC curve, namely can determine that the SOC value of now accumulator.But OCV is an Index For Steady-state, only when accumulator is in stable state, the terminal voltage at the accumulator two ends recorded is only OCV.Accumulator after work to stand the long time and can be only achieved stable state, at least needs more than 1 hour.Therefore, when accumulator stand when extrinsic current is 01 little time more than time, it is possible to by measure accumulator OCV determine its SOC₀Value.

OCV～SOC curve generally can be provided by accumulator manufacturer.When manufacturer is not provided that, it is also possible to measure by experiment and obtain.First the actual capacity C of this accumulator is recorded by the rated capacity method of testing of accumulator₀, then by accumulator by regulation charging system fully charged after, stands more than 1 hour, measurement accumulator terminal voltage, when the magnitude of voltage amplitude of variation recorded is less than 1mV, be recorded as OCV during SOC100%；Then 0.05C is released with 0.5C electric current constant current₀Electricity, stand more than 1 hour, then record OCV during SOC95% by upper method；The like, until discharging completely, record OCV during SOC0%.The data mapping that will record, just obtains OCV～SOC curve.OCV～SOC the curve testing the lithium ion battery that rated voltage is 2.4V recorded exactly shown in Fig. 2.

Except above-mentioned two situations, the SOC value recorded after taking last end-of-job is as the SOC at this task initial stage₀Value.Therefore, when accumulator continuous operation, or dwell time do not grow after when resuming work again, the accuracy that ampere-hour integration method calculates just has directly influenced the precision that accumulator SOC value calculates.

When battery-operated, measurement is the real-time current i (τ) in external circuit, it time is integrated, and after just obtaining battery-operated time t, flows through the electricity Q of external circuit, it may be assumed that

$Q={\&Integral;}_0^{t}i\left(\mathrm{\&tau;}\right)d\mathrm{\&tau;}---\left(10\right)$

Owing to the accumulator sense of current when charging and discharging is contrary, when therefore we specify to discharge, electric current is for just, and during charging, electric current is negative.

It should be noted that the electricity that active substance participation electrode reaction produces not necessarily all flows through external circuit, or the electric current in external circuit also might not all be absorbed by the active substance of accumulator.This mainly has three reasons to cause, i.e. cell bypass electric leakage, accumulator self discharge (i.e. internal electrical losses) and electrode side reaction.Accordingly, it would be desirable to introduce current efficiency coefficient η_eCorrect this situation.During charging, η_eLess than or equal to 1；η during electric discharge_eBe more than or equal to 1.Then, formula (10) becomes:

$Q={\&Integral;}_0^t{\mathrm{\&eta;}}_{e}i\left(\mathrm{\&tau;}\right)d\mathrm{\&tau;}---\left(11\right)$

For accumulator reasonable in design, manufacturing process specification, the bypass leakage of battery is negligible.And for lithium ion battery, self discharge and electrode side reaction are all few, therefore can η_eSee 1 as.

Formula (11) represents between accumulator is operationally after t, the amount of the active substance increasing in accumulator or reducing.This increase amount or minimizing amount are unrelated with the working condition of accumulator, as long as accumulator has electricity to flow in or out, the amount of corresponding active substance must be had to take part in electrode reaction.

Then, after battery-operated time t, internal storage battery there remains the amount of active substance and can be represented by the formula:

But, as it was previously stated, these residual activity amount of substances are not all to participate in electrode reaction, in these residual activity materials, have how much can to participate in electrode reaction then relevant with the use condition of accumulator on earth.Under current operating conditions, real surplus Useful active amount of substance also need to introduce an effective rate of utilization coefficient η in above formula, we term it the correction coefficient of actual capacity.Then formula (12) becomes:

Affect a lot of because have of active substance of battery effective rate of utilization, as used condition, manufacturing process, battery system and structure etc..But for manufacturing the accumulator of molding, topmost influence factor uses condition exactly, i.e. operating temperature and charge-discharge magnification.

Operating temperature is very big on the impact of accumulator capacity, being primarily due to improve temperature and the reactivity of active substance can be made to improve, and reduce the diffusional resistance of active substance, thus improve the utilization rate of active substance, making the actual capacity of accumulator be improved.We are referred to as the temperature correction facotor η of storage battery practical capacity the ratio of the accumulator capacity recorded under different temperatures Yu its rated capacity_T, it may be assumed that

${\mathrm{\&eta;}}_T=\frac{C_T}{C_n}---\left(14\right)$

In formula: C_TThe actual capacity of accumulator, Ah when operating temperature is T.

For lead-acid accumulator, η_TGenerally linear with T, can be represented by the formula:

η_T=1-α (25-T) (4)

In formula, α is the temperature coefficient of accumulator, and this is one of the fundamental performance parameter of accumulator, can be provided by accumulator manufacturer.α is relevant with the discharge-rate of accumulator, when discharging such as 1C, and α=0.01/ DEG C；During 0.5C electric discharge, α=0.0085/ DEG C；During 0.1C electric discharge, α=0.006/ DEG C.

But for lithium ion battery, the impact of temperature is much smaller, and not linear yet.Shown in Fig. 3 be lithium ion battery 1C electric discharge time, η_TRelation curve with T.The temperature characterisitic of accumulator is the key property of accumulator, in order to be sufficiently accurate it may be desired to accumulator manufacturer provides, naturally it is also possible to measure by experiment.

Charge-discharge magnification is on the key property that the impact of accumulator capacity is also accumulator.Charge-discharge magnification refers to the ratio of charging and discharging currents and the rated capacity of this accumulator, and conventional xC represents.As being the accumulator of 10Ah for rated capacity, 1C electric discharge means that its discharge current is 10A；0.2C charging then represents that its charging current is 2A.Charge-discharge magnification is more big, and the capacity that accumulator can be filled with or release is more little, the restriction of this electrochemical reaction rates being mainly receptor 1 activity material and diffusion inside.Increase along with discharge-rate, the velocity of electrons flowed in or out on electrode is more fast, the response speed of active substance will not catch up with the speed of electron transfer, or the active substance of electrode interior does not catch up with the speed of electrode active surface material consumption to the speed that electrode surface spreads, make the internal resistance increase of accumulator so that the utilization rate of active substance reduces.Shown in Fig. 4 is lithium ion battery charging curve under different discharge-rates, it can be seen that along with the increase of discharge-rate, the capacity that accumulator can be released is obviously reduced.

We call rate capability correction coefficient η the ratio of the storage battery practical capacity under different discharge-rates with rated capacity_C, shown in Fig. 5 is exactly lithium ion battery capacity correction coefficient under different discharge-rates.

Owing to accumulator is when actually used, its actual capacity is limited mainly by operating temperature and discharge-rate impact, and therefore the correction coefficient η of accumulator actual capacity under currently used condition just can be expressed from the next:

η=η_T·η_C(3)

After specify that the implication of above-mentioned parameter, formula (13) and (9) are substituted into formula (8), just draw the computing formula of accumulator SOC:

$SOC\left(t\right)=\frac{\mathrm{\&eta;}\&CenterDot;(\frac{{\mathrm{SOC}}_0}{100}\&CenterDot;{\mathrm{\&eta;}}_{age}\&CenterDot;C_n-{\&Integral;}_0^t{\mathrm{\&eta;}}_{e}i(\mathrm{\&tau;})d\mathrm{\&tau;})}{{\mathrm{\&eta;}}_{age}\&CenterDot;C_n}\&times;100\%---\left(1\right)$

But, use and there will be a problem during formula (1), i.e. storage battery practical capacity correction coefficient η under current operating state_NOWMore than the storage battery practical capacity correction coefficient η under a upper duty_prevTime, SOC value increases.This seems that some is unintelligible, and the practical working situation of accumulator is thus in fact, and this phenomenon is called capacity restoration.In real life, we can be clearly felt that the battery of off-capacity in winter is much older to capacity in summer, and illustrating under low temperature that the accumulator of off-capacity has arrived capacity under hot conditions can be restored.For another example, not driven the battery of remote-control car to be put in crystal clock can also use for a long time, illustrates that, when the accumulator of off-capacity has arrived low-rate discharge under big multiplying power discharging, capacity can also obtain recovery.Produce the reason of this phenomenon to be primarily due at low temperatures or when high-multiplying power discharge, cause that actual capacity diminishes owing to the utilization rate of electrode active material is low, but the amount of electrode active material does not reduce.So when this accumulator is put under the high temperature conditions or when low-rate discharge, this amount of activated material can retrieve again utilization, then can release again electricity.The phenomenon that capacity can recover is not taken into account in existing ampere-hour integration method.

The practical working situation that is consistent with accumulator though this residual capacity fluctuates up and down along with working condition, but be difficult to for a user accept, the sensation of instability can be given.Therefore, it is necessary to the value of η is made stipulations, reduce fluctuation.It is true that although the capacity of accumulator can recover, but can not instant recovery, say, that capacity restoration requires time for.The time of capacity restoration was relevant with accumulator, from several seconds to several hours.We can take the average size correction coefficient in a set time section before accumulator current timeAs the η in formula (1).The time span of this set time section can be several seconds, it is also possible to is several hours, it is preferable that 1 minute to 30 minutes.

But it is noted that when accumulator actual capacity correction coefficient under current operating conditions diminishes, be just absent from capacity restoration, therefore should take the real time capacity correction coefficient η of current time in this case_NOW。

To sum up, we the correction coefficient η of regulation storage battery practical capacity determines by the following method:

A. according to the temperature recorded in real time and discharge current, calculate by formula (3) and obtain real-time correction coefficient η (t)；

B. the average correction coefficient in the set time section of (including current time) before calculating current time

C. currently the η obtained will be measured in real time_NOWThe calculated average correction coefficient with step bCompare, if ${\mathrm{\&eta;}}_{\mathrm{NOW}}>\stackrel{\&OverBar;}{\mathrm{\&eta;}},$ Then $\mathrm{\&eta;}=\stackrel{\&OverBar;}{\mathrm{\&eta;}};$ If ${\mathrm{\&eta;}}_{\mathrm{NOW}}\&le;\stackrel{\&OverBar;}{\mathrm{\&eta;}},$ Then η=η_NOW。

The time span of described set time section is between 1 second to 3 hours.Preferably 1 minute to 30 minutes.

In order to reduce amount of calculation and the fluctuation of SOC result of calculation, current time measures the storage battery practical capacity correction coefficient η obtained in real time_NOWCompared with the current η value just used in computing formula (1), when amplitude of fluctuation is less than or equal to 5%, η value can remain unchanged.

Working condition when the value rule of above η is just for battery discharging, owing to accumulator charging is always undertaken by fixing charging system until fully charged, now specifying SOC=100%, it can be considered that when charging η=1.

When accumulator quits work, it should take η=1 and recalculate SOC, recording as the SOC after this end-of-job, what it represented is the whole residual activity amount of substance of accumulator.This is also consistent with the practical working situation of accumulator, because the amount of the active substance not being utilized effectively under running conditions does not reduce, this portion capacity all can partly recover or full recovery.

According to the new accumulator SOC computing formula that the present invention proposes, only need to measuring the charging and discharging currents in side circuit according to a conventional method, battery operating temperature can calculate the SOC of accumulator in real time in accumulator practical work process.When accumulator is in electric discharge duty, the concrete grammar measuring its SOC is as follows:

A. start, determine η according to accumulator kind and recycling number of times_eAnd η_age, and be used for calculatingThe time span of set time section；

B. judge whether just fully charged, in this way then SOC₀=100%；Otherwise, then judge whether that time of repose was more than 1 hour, then measures the terminal voltage OCV as accumulator of accumulator in this way, determines SOC according to OCV～SOC relation curve₀；The SOC value recorded time otherwise using end-of-job last time is as the SOC of this task₀Value；

C. operating temperature and the discharge current of accumulator are measured in real time, according to the temperature characterisitic of accumulator and flash-over characteristic, it is determined that η_TAnd η_C, calculate η according to formula (3)_NOWAnd calculate in current time (comprising current time) set time section beforeBy η_NOWComparing with the η value being being currently used in computing formula (1), if amplitude of fluctuation is less than or equal to 5%, then η value is constant；Otherwise compare η again_NOWWithIf ${\mathrm{\&eta;}}_{\mathrm{NOW}}>\stackrel{\&OverBar;}{\mathrm{\&eta;}},$ Then $\mathrm{\&eta;}=\stackrel{\&OverBar;}{\mathrm{\&eta;}};$ Otherwise η=η_NOW；

D. according to the real-time residual capacity SOC after computing formula (1) calculating accumulator working time t；

E. terminate, take η=1, recalculate the SOC value after the SOC value obtained is recorded as this end-of-job.

The advantages such as above-mentioned measurement process is easily achieved for a person skilled in the art, and therefore the method for measurement remaining battery capacity SOC provided by the invention has that computational methods are simple but precision is high, it is achieved easy but hardware requirement is low, applied widely.

Detailed description of the invention

Specific embodiments of the invention are described below, and in conjunction with accompanying drawing, the bright technical scheme of we are further elaborated, but the present invention is not limited to these embodiments.

The mensuration of embodiment 1 accumulator attenuation quotient

Take a nominal 2.4V newly dispatched from the factory, rated capacity is the lithium-ion-power cell of 10Ah, by the detection method of 20 DEG C of discharge capacities in automobile industry standard QC/T743-2006 " lithium-ions battery used for electric vehicle ", it is 2.75V by charge cutoff voltage, discharge cut-off voltage is 1.5V, measure the actual capacity of this accumulator, calculate attenuation quotient η by formula (2)_age.Then it being circulated discharge and recharge 10 times with battery test system, the charging system that charge condition specifies by battery manufacturers, electric discharge is then with the constant current discharge 35 minutes of 20A.Measure the capacity of accumulator by the detection method of above-mentioned 20 DEG C of discharge capacities again and calculate attenuation quotient η_age.Change the cycle-index N of discharge and recharge, measure a series of attenuation quotient and map, as shown in Figure 6.

Accumulator SOC measurement result when embodiment 2 constant current discharge

Take a nominal 2.4V, rated capacity is 10Ah lithium-ion-power cell, no more than 10 times of cycle charge-discharge number of times, and in electric automobile laboratory, ambient temperature is carry out 1C constant current discharge experiment at 20 DEG C, discharge time is 30 minutes, stands more than 2 hours at ambient temperature before experiment.The terminal voltage recording accumulator is 2.493V, looks into the SOC=80% that OCV～SOC curve chart is corresponding.Take SOC₀=80%, overlap identical BMS with two and monitor battery discharging situation simultaneously, a set of employing SOC measuring method provided by the invention, owing to being accumulator cycle charge-discharge number of times no more than 10 times, therefore desirable η_age=1.1；And take 20 minutes sections to calculate average size correction coefficient.The ampere-hour integration method SOC computational methods that another set of employing is traditional.All parameters all by BMS according to the temperature recorded in real time and the automatic value of discharge current data the calculating for SOC.After electric discharge terminates, method provided by the invention finally shows SOC=34.6%；Traditional ampere-hour integration method finally shows SOC=34.1%.Accumulator is stood more than 2 hours, records OCV=2.300V, look into the SOC=34.5% that OCV～SOC curve chart is corresponding.Visible, SOC measuring method result provided by the invention is closer to real SOC value, and computational accuracy is 0.3%.

Accumulator SOC measurement result under embodiment 3 time-dependent current discharging condition

Taking a nominal 2.4V, rated capacity is 10Ah, cycle charge-discharge 200 times fully charged lithium-ion-power cell, and in electric automobile laboratory, discharge test when ambient temperature is carry out time-dependent current at 20 DEG C, discharge current and persistent period see following table.Overlap identical BMS with two and monitor the discharge scenario of accumulator, a set of employing SOC measuring method provided by the invention simultaneously, take η_age=1.0；And take the 30s time period and calculate average size correction coefficient.All parameters all by BMS according to the temperature recorded in real time and the automatic value of discharge current data the calculating for SOC.

Sequence number	Discharge current, A	Persistent period, s
			1	5	60
2	30	300
			3	20	300
4	10	600
			5	5	300

After electric discharge terminates, method provided by the invention finally shows SOC=36.7%；Traditional ampere-hour integration method finally shows SOC=37.3%.Accumulator is stood more than 2 hours, records OCV=2.316V, look into the SOC=36.5% that OCV～SOC curve chart is corresponding.Visible, SOC measuring method result provided by the invention is closer to real SOC value, and computational accuracy is 0.5%.

Accumulator SOC measurement result when embodiment 4 intermittent discharge

Take a nominal 2.4V, rated capacity is 10Ah, cycle charge-discharge 1200 times fully charged lithium-ion-power cell, in electric automobile laboratory, discharge test when ambient temperature is carry out intermittent discharge at 20 DEG C, discharge current and persistent period see accompanying drawing 7.Overlap identical BMS with two and monitor the discharge scenario of accumulator, a set of employing SOC measuring method provided by the invention simultaneously, take η_age=0.95；And take in 5 minutes sections and calculate average size correction coefficient.All parameters all by BMS according to the temperature recorded in real time and the automatic value of discharge current data the calculating for SOC.The comparing result of SOC measuring method provided by the invention and existing ampere-hour integration method evaluation method is shown in accompanying drawing 8.In Fig. 8, abscissa represents the time of accumulator real work, and the middle time stood is not shown in the diagram.After experiment terminates, method provided by the invention finally shows SOC=43.1%, and existing ampere-hour integration method finally shows SOC=39.9%.Continue to be discharged to blanking voltage by the method for embodiment 1 by accumulator, release the electricity of 4.08Ah altogether, calculate real SOC=42.9%.Its computational accuracy of method provided by the invention is 0.7%, far above existing ampere-hour integration method.As can be seen from Figure 8, on the SOC curve of the present invention, when big multiplying power discharging forwards little multiplying power discharging to, SOC curve substantially has a buffering, and this is that accumulator capacity recovers phenomenon, meets the practical working situation of accumulator.Existing integration ampere-hour method fails to embody the working condition of this reality, thus estimation precision is high not as good as the present invention.

Although the present invention is by above-mentioned nominal 2.4V; rated capacity is that the embodiment of the lithium-ion-power cell of 10Ah is to set forth the particular content of the present invention; but the present invention is not limited to lithium ion battery and foregoing thereof; those skilled in the art; without departing under technical solution of the present invention premise; the present invention is made various change and modification, both falls within scope.

Claims (9)

1. the method measuring remaining battery capacity SOC, it is characterised in that measure the residual capacity SOC (t) after accumulator continuous working period t according to the following steps:

A. initial residual capacity SOC during battery-operated is determined₀；

B. measure the operating current i (τ) during battery-operated in real time, during electric discharge be on the occasion of, be negative value during charging；

C. by the residual capacity SOC (t) after formula calculated below (1) calculating accumulator continuous working period t:

$SOC\left(t\right)=\frac{\mathrm{\&eta;}\&CenterDot;(\frac{{\mathrm{SOC}}_0}{100}\&CenterDot;{\mathrm{\&eta;}}_{age}\&CenterDot;C_n-{\&Integral;}_0^t{\mathrm{\&eta;}}_{e}i(\mathrm{\&tau;})d\mathrm{\&tau;})}{{\mathrm{\&eta;}}_{age}\&CenterDot;C_n}\&times;100\%---\left(1\right)$

In formula: η_ageThe attenuation quotient of accumulator；

C_nThe rated capacity of accumulator, Ah；

η_eCurrent efficiency coefficient；

The correction coefficient of η storage battery practical capacity；

The time of t accumulator continuous firing, s.

D. after battery-operated terminates, take η=1, be recorded as the SOC value after this battery-operated terminates by computing formula (1) calculated SOC value；

The attenuation quotient η of described accumulator_ageAfter referring to accumulator cycle charge-discharge n times, the ratio of storage battery practical capacity and rated capacity；The rated capacity C of described accumulator_nRefer to accumulator by the charge condition of regulation fully charged after, then by the discharging condition electric discharge of regulation until the electricity can released when being discharged to blanking voltage；Described current efficiency coefficient η_eIt is actually used in the electric current of electrode reaction and the ratio of extrinsic current, less than or equal to 1 during charging, be more than or equal to 1 during electric discharge when referring to accumulator cell charging and discharging；The correction coefficient η of described storage battery practical capacity refers to the ratio of accumulator can be charged into or release under real use state actual capacity and rated capacity.

2. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that described initial residual capacity SOC₀Determined by one of following situation:

A. when described accumulator by regulation charging system fully charged time, SOC₀=100%；

B. when described accumulator stand when extrinsic current is 01 little time more than time, measure accumulator open-circuit voltage OCV, determine SOC according to OCV～SOC relation curve of accumulator₀Value；

C. in addition to the conditions already mentioned, SOC₀=SOC_prev, SOC in formula_prevThe SOC value recorded when being accumulator last time end-of-job.

3. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that the attenuation quotient η of described accumulator_ageObtained by following steps test:

A. by known nominal capacity C_nAccumulator cycle charge-discharge n times；

B. the actual capacity C (N) of the accumulator after cycle charge-discharge n times is obtained by the method for testing measurement of battery rating；

C. the accumulator attenuation quotient η after cycle charge-discharge n times_age(N) obtained by following calculating:

${\mathrm{\&eta;}}_{age}\left(N\right)=\frac{C\left(N\right)}{C_n}---\left(2\right)$

D. choose different N value repeat the above steps, obtain the η under a series of different N value_age(N) value mapping, obtains η_age(N) relation curve of～N；

E. described η is looked into_age(N) relation curve of～N, obtains the accumulator attenuation quotient η after Arbitrary cyclic discharge and recharge number of times_age。

4. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that the correction coefficient η of described storage battery practical capacity is calculated as follows according to actually measured temperature and charging and discharging currents:

η=η_T·η_C(3) in formula: η_TCorrection coefficient due to the storage battery practical capacity that variations in temperature causes；

η_CThe accumulator actual capacity under different charge-discharge magnifications capacity correction coefficient compared with rated capacity.

5. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that described in computing formula (1), the correction coefficient η of storage battery practical capacity determines by the following method:

A. according to the temperature recorded in real time and charging and discharging currents, calculate by formula (3) and obtain real-time correction coefficient η (t)；

B. the average correction coefficient in the set time section before current time is calculated

C. by currently real-time calculated η_NOWWith average correction coefficientCompare, ifThen $\mathrm{\&eta;}=\stackrel{\&OverBar;}{\mathrm{\&eta;}};$ If ${\mathrm{\&eta;}}_{\mathrm{NOW}}\&le;\stackrel{\&OverBar;}{\mathrm{\&eta;}},$ Then η=η_NOW,

The time span of described set time section is between 1 second to 3 hours, described average correction coefficientCalculating comprise the real time correction coefficient η of current time_NOW。

6. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that when described accumulator is in charged state, take η=1.

7. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterised in that when being lithium ion battery for described accumulator, take η_e=1, described lithium ion battery is liquid lithium ionic cell or polymer Li-ion battery.

8. a kind of method measuring remaining battery capacity SOC according to claim 1, it is characterized in that described storage battery practical capacity correction coefficient η that current time records in real time is compared with the η value that previous moment uses in computing formula (1), when amplitude of variation is less than or equal to 5%, the η value in computing formula (1) is constant.

9. a kind of method measuring remaining battery capacity SOC according to claim 4, it is characterised in that described η_TCalculated by following formula:

η_T=1-α (25-T) (4)

In formula: the temperature coefficient of α accumulator, 1/ DEG C；

The operating temperature of T accumulator, DEG C.