JP2000147075A - Apparatus for calculating remaining capacity of cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for calculating the remaining capacity of a cell with few calculation errors. SOLUTION: A discharge characteristic map showing the relation between the discharge voltage in a reference discharge power value and the discharge quantity is formed (S26) from open voltage characteristics and internal resistance characteristics, and the discharge characteristic map is integrated to obtain (S28) the remaining capacity. Thus the remaining capacity drop due to memory effects and the remaining capacity drop due to the cell deterioration can be separated to obtain the remaining capacity, and hence the remaining capacity of the cell can be estimated accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery remaining capacity calculator for calculating the remaining capacity or the degree of deterioration of a battery mounted on an electric vehicle, for example.

[0002]

2. Description of the Related Art A rechargeable battery used in an electric vehicle is repeatedly charged and discharged, so that the dischargeable capacity gradually decreases due to deterioration. The amount (watts) or the amount of discharge (ampere hours) must be known exactly. For this reason, a method of storing the relationship between the discharge voltage V and the remaining capacity in a map and substituting the detected discharge voltage V into this map to determine the remaining capacity has conventionally been employed. In this method, since the above relationship fluctuates due to the effect of the memory effect of the battery, the relationship between the discharge voltage V and the remaining capacity when the memory effect occurs is learned.

Japanese Patent Application Laid-Open No. 7-55903 discloses that the discharge amount Ah obtained by current integration is subtracted from a previously stored full charge capacity (a discharge amount obtained from a full charge state to a predetermined discharge termination condition). , It is proposed to determine the remaining capacity. Japanese Patent Application Laid-Open No. 8-278352 discloses that a remaining capacity corresponding to a discharge voltage at a predetermined reference current value is calculated from a measured discharge voltage and a discharge current, and data comprising the measured discharge voltage and the discharge current has been used. It has been proposed that the calculation of the remaining capacity be stopped if it is specific compared to the collected data.

However, in these conventional methods for calculating the remaining capacity, it is difficult to distinguish whether the deterioration of the discharge characteristics is caused by the deterioration of the battery or the memory effect, and it is difficult to calculate the remaining capacity accurately. There was a problem that was large. Therefore, Japanese Patent Application Laid-Open No. Hei 10-246760 filed by the present applicant discloses that the initial characteristic map indicating the relationship between the discharge voltage V and the discharge amount Ah is separately corrected based on the memory effect and the battery deterioration, respectively. A discharge characteristic indicating the relationship between the voltage V and the discharge amount Ah is formed, the area of the discharge region determined by the discharge characteristic is integrated to obtain a remaining dischargeable power amount, and the remaining dischargeable power amount is defined as a remaining capacity. An estimation method (remaining dischargeable power amount estimation expression remaining capacity calculation method) was proposed.

[0005]

However, even in the method of estimating the residual dischargeable electric energy described above, the shape of the discharge characteristics, particularly the shape of the discharge characteristics at the end of discharge, in which the change of the discharge voltage becomes remarkable during repeated charging / discharging. However, there is a problem that a remaining capacity calculation error deviating from the shape of the initial discharge characteristics becomes large.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an apparatus for calculating the remaining capacity of a battery, which can accurately calculate the remaining capacity.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for calculating a remaining capacity of a battery, the internal resistance characteristic indicating a past relationship between an internal resistance of the battery and a discharge amount. The remaining capacity is calculated based on the open voltage characteristics indicating the past relationship between the open voltage of the battery and the discharge amount, the current value of the internal resistance, and the current value of the open voltage. That is, in this configuration, the remaining capacity is estimated based on the relationship between the internal resistance and the discharge amount and the relationship between the open-circuit voltage and the discharge amount.

In this manner, the remaining capacity of a battery having a memory effect can be estimated much more accurately than in the past for the reason described in detail below. According to the second aspect of the present invention, in the battery remaining capacity computing device according to the first aspect, the open-circuit voltage characteristic of the past is modified by modifying a past open-circuit voltage characteristic with a predetermined function having a current value of the open-circuit voltage as a variable. The characteristic is formed, the past internal resistance characteristic is deformed by a predetermined function having the current value of the internal resistance as a variable to form the current internal resistance characteristic, and the remaining capacity is calculated based on both of these characteristics. . In this way, the remaining capacity of the battery having the memory effect can be estimated much more accurately than before.

That is, a feature of the remaining capacity calculation method according to the first or second aspect is that an internal resistance characteristic (a relation between an internal resistance and a discharge amount) and an open voltage characteristic (a relation between an open voltage and a discharge amount) are used. To calculate the remaining capacity. With this configuration, the influence of the battery deterioration on the decrease in the battery capacity and the influence of the memory effect can be accurately distinguished, so that the remaining capacity can be calculated accurately. In other words, in this configuration, the capacity reduction due to the battery degradation is estimated based on the estimated internal resistance characteristic, and the capacity reduction due to the memory effect is estimated based on the estimated open-circuit voltage characteristic. The cause can be clearly distinguished and the remaining capacity can be accurately estimated.

[0010] More specifically, the battery is equivalent to
It can be represented by an equivalent circuit in which an ideal battery having a predetermined open voltage with no internal resistance and a resistance element equal to the internal resistance are connected in series. In this equivalent circuit, the memory effect causes a decrease in the open-circuit voltage of the battery, and the battery deterioration causes an increase in the internal resistance of the battery. This is clear from Japanese Patent Application Laid-Open No. Hei 10-246760 filed by the present applicant.

Therefore, it is easy to extract a change in battery characteristics due to the memory effect as a change in open-circuit voltage and a change due to battery deterioration as a change in internal resistance. The remaining capacity can be calculated. To calculate the remaining capacity based on the internal resistance characteristic and the open-circuit voltage characteristic, for example, as described in claim 3, the discharge voltage and the discharge voltage obtained based on the current internal resistance characteristic and the present open-circuit voltage characteristic are calculated. The remaining capacity can be calculated by calculating a discharge characteristic indicating a relationship with the discharge amount and integrating the discharge characteristic from the current discharge amount value to a predetermined discharge end discharge amount value.

After all, if the internal resistance characteristic and the open-circuit voltage characteristic at this time, that is, at the present time, can be accurately estimated for each value of the discharge amount, the relationship between the discharge voltage and the discharge amount can be easily obtained based on them. The remaining capacity can be accurately estimated by integration. By the way, the open circuit voltage is OC
V, and the internal resistance is r, the discharge voltage V = OCV + A ·
r.

FIG. 2 schematically shows this state. C1 is a reference past discharge characteristic, and C2 is a current discharge characteristic of a further deteriorated battery. The voltage difference ΔV between the two at the predetermined discharge amount value AH0 is the difference ΔVo between the open voltages due to the memory effect.
And the voltage difference ΔVr = A · Δr resulting from the internal resistance r increasing by Δr due to battery deterioration. What is important here is that the change in the open-circuit voltage (ie, the functional relationship between the two) with the change in the discharge amount is completely different from the change in the internal resistance (ie, the functional relationship between the two) with the change in the discharge amount. That is. If the two are exactly the same, there is no need to distinguish between the change in the open voltage due to the change in the discharge amount and the change in the internal resistance due to the change in the discharge amount.

Change (decrease) in open-circuit voltage due to memory effect
Is the same in the discharge amount range where the same memory effect occurs, and therefore, if the past open-circuit voltage characteristics have been determined, the open-circuit voltage value on this past open-circuit voltage If the open-circuit voltage value of (actual measurement) is known, the past open-circuit voltage characteristics are slid by the difference between them (level down).
By doing so, the current open-circuit voltage characteristics can be accurately estimated.

That is, the voltage difference between the virtual open voltage value corresponding to the current value of the discharge amount and the current value of the open voltage on the past open voltage characteristics is determined by the memory effect. What is necessary is to store the discharge amount ranges having different amounts, respectively, and to slide the past open-circuit voltage characteristics by this voltage difference for each discharge amount range to obtain the present open-circuit voltage characteristics. It should be noted that the decrease in the open-circuit voltage due to the memory effect can be considered to be substantially eliminated by this charging in the discharge amount range from the charging start point to the charging end point. Therefore, after performing a plurality of partial discharges having different charge start points and charge end points between the fully charged state and the completely discharged state,
It can be seen that the open circuit voltage is different in each discharge amount range. Therefore, a voltage difference between a past reference open-circuit voltage value and a current open-circuit voltage value corresponding to an equal discharge amount value for each discharge amount range having different charge / discharge histories is stored in memory. Thus, it can be seen that the slide amount of the open-circuit voltage characteristic as a reference in the past should be changed.

An example is schematically shown in FIG. In this figure, C3 is the initial open-circuit voltage characteristic, and C4 is first fully charged after discharging to the discharge amount value Ah1, then fully charged after discharging to the discharge amount value Ah2, Indicates open circuit voltage. ΔV1 is the discharge amount value Ah1
The open circuit voltage drop due to the memory effect in the discharge amount range of Ah2 is shown, and ΔV2 shows the open circuit voltage drop due to the memory effect in the discharge amount range after the discharge amount value Ah2.

On the other hand, the change (increase) in the internal resistance due to battery deterioration tends to increase as the discharge becomes deeper (as the discharge amount increases). Therefore, in order to estimate the current internal resistance characteristic from the past internal resistance characteristic, it is necessary to process the past internal resistance characteristic with a function that shows such a tendency well and make it the current internal resistance characteristic. Therefore, in this specification, as described in claims 5 and 6,
In the following two methods, the internal resistance characteristic as a reference in the past is modified.

First, in the method according to the fifth aspect, a resistance ratio between a virtual internal resistance value corresponding to the current value of the discharge amount on the past internal resistance characteristic and the current value of the internal resistance is determined. The internal resistance axis of this internal resistance characteristic is extended by this resistance ratio to obtain the current internal resistance characteristic. This makes it possible to cope with the above tendency because the internal resistance value in the current internal resistance characteristic increases as the discharge proceeds and the internal resistance value in the past internal resistance characteristic increases. It is apparent that the error between the current internal resistance characteristic and the current true internal resistance characteristic can be reduced well.

Next, in the method according to the sixth aspect, a discharge amount ratio between a virtual discharge amount value corresponding to the current value of the internal resistance on the past internal resistance characteristic and the current value of the discharge amount is determined. Then, the discharge amount axis of the past internal resistance characteristic is compressed by this discharge amount ratio to obtain the current internal resistance characteristic. This makes it possible to cope with the above tendency because the internal resistance value in the current internal resistance characteristic increases as the discharge proceeds and the internal resistance value in the past internal resistance characteristic increases. It is apparent that the error between the current internal resistance characteristic and the current true internal resistance characteristic can be reduced well.

It is known that as the battery deteriorates, the internal resistance specifically increases in accordance with the increase in the amount of discharge in a deep discharge state. FIG. 4 schematically shows how the internal resistance increases due to an increase in the amount of discharge as the battery deteriorates at the end of discharge. C5 is an initial internal resistance characteristic, and C6 is an internal resistance characteristic in which battery deterioration has advanced. Therefore, a function for calculating the internal resistance corresponding to a specific increase in the internal resistance at the end of discharge when the battery is deteriorated, and a function for calculating the internal resistance in the other discharge amount range (referred to as a function for expressing the specific internal resistance at the end of discharge). , The current internal resistance characteristic can be calculated from the past internal resistance characteristic. The above-described internal resistance calculating method according to claim 6 shows a favorable increase in the internal resistance at the time of battery deterioration at the end of discharge (a phenomenon in which the internal resistance increases more rapidly than other discharge amount ranges). Can be.

In particular, the expression function for increasing the internal resistance specific to the end of discharge is considered in view of the fact that the internal resistance characteristics gradually change.
It is preferable that the internal resistance characteristic used as a reference in the past is the internal resistance characteristic as short as possible, preferably the internal resistance characteristic at the time of the previous discharge. In the first to seventh aspects of the present invention, the past open-circuit voltage characteristic and the past internal resistance characteristic for calculating the current open-circuit voltage characteristic and the current internal resistance characteristic used for the remaining capacity calculation are calculated based on the immediately preceding charging characteristic. The previous open-circuit voltage characteristics and the previous internal resistance characteristics calculated in the previous previous discharge can be used. This is particularly suitable for the internal resistance characteristic calculation in which the internal resistance gradually changes irreversibly.

The past open-circuit voltage characteristics and the past internal resistance characteristics can be an initial open-circuit voltage characteristic and an initial internal resistance characteristic at the initial stage (initial operation of the battery). It is particularly suitable for the open-circuit voltage characteristic calculation which recovers in a timely manner. Furthermore, if the battery is fully charged or discharged from a predetermined discharge value to a complete discharge when the battery is used, the open-circuit voltage characteristics and the internal resistance characteristics at this time are stored. Calculating the characteristics and the internal resistance characteristics by the above method is also a preferable method for reducing errors.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a battery remaining capacity calculating device according to the present invention will be described below with reference to the drawings.

[0024]

FIG. 1 is a block diagram showing an example of a remaining capacity calculating device for a hybrid vehicle according to the present invention. Reference numeral 1 denotes a battery, and 2 denotes power transmission means including a rotating electric machine of a hybrid vehicle. The power transmission means is connected to an engine and a drive shaft of the vehicle and exchanges energy between them and the battery in the form of electric power. Reference numeral 3 denotes a bidirectional power converter that converts between DC power input / output to / from the battery 1 and AC power input / output to / from the power transmission means 2. Since the configurations of the power transmission means 2 and the bidirectional power converter 3 are well known and are not the gist of the present invention, further detailed description will be omitted. Note that the battery remaining capacity calculation means of this embodiment can be applied not only to a hybrid vehicle but also to an electric vehicle that runs on only a battery without an internal combustion engine.

The battery 1 is an assembled battery in which a number of Ni-MH batteries are connected in series, a current sensor 5 detects the charging / discharging current, a temperature sensor 6 detects the temperature, and the current, temperature, Is input to a controller 4 having a microcomputer configuration for calculating and displaying the battery deterioration degree together with the output voltage of the battery 1. (Remaining Capacity Calculation Routine 1) An example of the remaining capacity calculation process of this embodiment will be described below with reference to the flowchart shown in FIG.

First, it is checked whether or not the battery is currently discharging (S1).
0), if it is discharging, proceed to S12; if it is not discharging, proceed to S26. In S12, the measured internal resistance (current value of the internal resistance) Rm and the measured open-circuit voltage (current value of the open-circuit voltage) OCV are calculated from the measured current values of the discharge voltage V and the discharge current A.
m, and discharge current A from the beginning of discharge to the present.
Is accumulated to determine the current value Ahm of the discharge amount.

The measured internal resistance Rm is obtained by plotting a number of points defined by recently detected pairs of the discharge voltage V and the discharge current A on a VA two-dimensional plane to determine a first-order approximate straight line. It is determined from the inclination rate (ΔV / ΔA). Next, the detected discharge current A is multiplied by the actually measured internal resistance Rm to determine the voltage drop, and this voltage drop is added to the current value of the discharge voltage V to obtain the actually measured open voltage OCVm.

Next, a Ram map showing the internal resistance characteristics in the current discharge is created (S16). In this embodiment, it is assumed that this Ram map is created by modifying the previous Ram map created at the time of the previous discharge before the immediately preceding charge. In addition, it is a matter of course that the initial Ram map is created by modifying the initial Ram map indicating the initial internal resistance characteristic stored in advance.

First, the actually measured internal resistance R is shown in the previous Ram map.
m, the value Ahx of the virtual discharge amount corresponding to the actually measured internal resistance Rm is obtained on the previous Ram map. Next, an operation of calculating the ratio between the current value Ahm of the discharge amount Ah and the virtual value Ahx, and proportionally compressing an axis indicating the discharge amount on the two-dimensional plane indicating the previous Ram map (referred to as a discharge amount axis) with this ratio ( Capacity reduction operation) to obtain the current Ram map.

Various methods can be considered for creating the current Ram map. The internal resistance values of the Ram map in the past predetermined discharge cycle can be obtained by various methods. It can also be obtained by multiplying each conversion coefficient value. Further, the map indicating the conversion function can be rewritten together with the accumulation of the number of discharges. Next, the open voltage map OCVam stored in advance and the above Ra
A discharge characteristic map at the reference discharge power value is created from the m map (S18). Here, the discharge characteristic at the reference discharge power value is a predetermined reference discharge power (here, 2 k
This is a characteristic showing the relationship between the output voltage (discharge voltage) V of the battery and the amount of discharge Ah when W) is discharged.

More specifically, the discharge voltage V corresponding to an arbitrary value of the discharge amount Ah includes an open-circuit voltage value OCV ′ obtained from the corrected open-circuit voltage characteristic corresponding to the value of the discharge amount Ah, and the discharge amount Ah. Is calculated from the internal resistance value R ′ obtained from the corrected internal resistance characteristic in accordance with the following quadratic function equation. Here, W is the reference discharge power value, and A is this discharge amount Ah
Is the discharge current value at.

V = OCV′−R ′ · A = OCV′−R ′ · W / V Next, the remaining capacity is calculated from the discharge characteristics obtained in S18 (S20). That is, the discharge characteristic is changed to the discharge amount Ah
From the current value Ahm to the discharge amount at which the battery can no longer be discharged with the predetermined reference discharge power, to obtain a remaining capacity at which the reference discharge power can be discharged.

Next, it is checked whether or not the discharging is completed and the charging is started (S22). If not, the process jumps to S26, and if so, the discharge amount value Ahx immediately before the start of the charging is stored. (S24). This is because the decrease in the open-circuit voltage due to the memory effect starts from this discharge amount value Ahx in the next discharge. Next, it is checked whether or not the discharge has reached the discharge amount value Ahx at the time when the charging operation started immediately before (S26). If it has not reached, the process returns to the main routine without rewriting the open-circuit voltage map OCVam in S28, and if it has reached, the last time corresponding to the current value Ahx of the current discharge amount Ah on the open-circuit voltage map OCVam to be stored. Open-circuit voltage value OCVx and the actual measured open-circuit voltage OC corresponding to the current value Ahx of the discharge amount Ah
Open voltage map OCV for obtaining and storing the difference ΔV from Vm
The open-circuit voltage is slid downward by ΔV in a discharge amount range that is greater than the current value Ahm of the discharge amount Ah (S28). Thus, the open-circuit voltage drop due to the immediately preceding memory effect can be written to the open-circuit voltage map OCVam. Of course, the correction of the open-circuit voltage map OCVam after the first charging is performed using the initial Ram map indicating the initial open-circuit voltage characteristic stored in advance.

Next, in S10, if it is not discharging, it is checked whether or not the charging is completed (S30). If not, the process returns to the main routine, and if the charging is completed, the open voltage map OCVam in the stored open voltage map OCVam is stored. The value of the open-circuit voltage in the charge amount range where the charging operation has been performed is restored to the value of the initial open-circuit voltage characteristic (that is, the initial open-circuit voltage OCV map) stored in advance. This makes it possible to reflect the recovery effect of the charging operation corresponding to the decrease in the open-circuit voltage due to the memory effect on the open-circuit voltage map OCVam. (Remaining Capacity Calculation Routine 2) Hereinafter, the remaining capacity calculation process of this embodiment will be described with reference to flowcharts shown in FIGS.

Calculation of measured parameters (step S10)
0) First, the actually measured internal resistance Rm and the actually measured open circuit voltage OCVm are calculated from the current values of the actually measured discharge voltage V and discharge current A, respectively.
Further, the current value Ahm of the discharge amount is obtained by accumulating the discharge current A from the beginning of the discharge to the present. The measured internal resistance Rm
Plots a number of points defined by a pair of a recently detected discharge voltage V and a discharge current A on a VA two-dimensional plane to determine a first-order approximation straight line, and calculates a gradient thereof (ΔV / ΔA). Ask. Next, the detected discharge current A is multiplied by the actually measured internal resistance Rm to determine the voltage drop, and this voltage drop is added to the current value of the discharge voltage V to obtain the actually measured open voltage OCVm.

Calculation of Related Initial Parameters (Step S102) Next, the initial internal resistance Rini in the initial operation of the battery.
The initial internal resistance characteristic corresponding to the current value Ahm of the discharge amount is substituted by substituting the value of the current value Ahm of the above discharge amount into the initial internal resistance characteristic (stored in advance as an initial internal resistance map) indicating the relationship between the current value Ahm and the discharge amount. The current value of the initial internal resistance Rini is obtained, and the current value of the initial internal resistance Rini is further determined from the current value of the initial internal resistance Rini and the current value of the detected discharge voltage V and the current value of the discharge current A. The current value of the corresponding initial open circuit voltage OCVini (= Rini · A +
V) is calculated.

Determination of End of Discharge (Step S106) Next, in order to correct the internal resistance at the end of discharge, the remaining capacity of the initial characteristic at the present time is used as a material for determining whether or not it is at the end of discharge (or the latter half of discharge). This time Qr
Ini is calculated. The current value Qrini of the remaining capacity on the initial characteristics is the initial full charge capacity Q stored in advance.
The current value Ahm of the discharge amount described above is obtained from rfull (Ah).
(Ah) is subtracted.

Next, the present value Qr of the remaining capacity on the initial characteristics
It is checked whether or not ini is less than a predetermined threshold value obtained by multiplying the initial full charge capacity Qinifull by a predetermined constant x. If it is less than the above, it is determined that there is a possibility that a specific increase in the internal resistance of the battery occurs at the end of the discharge or the latter half of the discharge, and the process proceeds to the next step S110. There is no possibility that a significant internal resistance increase phenomenon will occur, and the correction performed in S114 is unnecessary, and the process jumps to S122. That is, this determination step is performed in a shallow discharge amount region where a specific increase phenomenon of the internal resistance R at the end of the discharge should not occur.
This is to prevent the internal resistance correction operation performed in step 4 from being erroneously performed. For example, the constant x is a constant less than 1, and is set to, for example, 0.5.

In step S106, the current value Qini of the remaining capacity on the initial characteristics and the initial full charge capacity Qinifu
Although it was determined whether the end of discharge or the latter half of discharge by comparing with the full charge capacity Ah, it may be obtained by the same comparison between the previously obtained full charge capacity Ah and the current discharge amount Ah. It may be obtained by the same comparison between the full charge capacity by discharging with electric power and the discharging capacity by discharging with the predetermined discharging power.

Determination of Increase in Internal Resistance at End of Discharge (Step S110) Next, the previously determined corrected internal resistance characteristic (corrected internal resistance Ra
characteristics indicating the relationship between the Mend and the discharge amount Ah,
Current value Ahm of the discharge amount Ah
Is substituted for the corrected internal resistance Ram on the previous Ram map corresponding to the current value Ahm of the discharge amount Ah.
The value of nd (called the previous value) Rambefore is obtained.

Next, the measured internal resistance Rm is calculated as Ramb
It is determined whether or not a predetermined threshold value obtained by multiplying “efore” by a predetermined constant y is exceeded. If it exceeds, it is determined that the specific internal resistance increase phenomenon at the end of the discharge has occurred, and the process proceeds to S112. If it is equal to or less than the above, the increase phenomenon has not occurred, and it is determined that the correction in S114 for compensating for the increase phenomenon is unnecessary, and the process proceeds to S116. For example, the constant y is a constant exceeding 1.

In S110, the discharge amount Ah
Of the internal resistance value Rambefore on the previous Ram map corresponding to the current value Ahm and the measured internal resistance Rm, it was determined whether or not the internal resistance sudden increase phenomenon occurred at the end of discharge. Value Rin of the corrected internal resistance Rini on the initial internal resistance characteristic
The presence or absence of a sudden increase in the internal resistance at the end of discharge may be determined by comparing ivefore with the measured internal resistance Rm.

Correction of internal resistance sudden increase phenomenon at the end of discharge 1
(Step S112) Next, the measured internal resistance Rm is substituted for the corrected internal resistance characteristic (previous Ram map) obtained at the time of the previous discharge before the immediately preceding charge, and the discharge corresponding to the measured internal resistance Rm on the previous Ram map is performed. The value Ahx of the quantity is determined. In S112,
Substituting the actually measured internal resistance Rm into the corrected internal resistance characteristic (previous Ram map) obtained at the time of the previous discharge before the immediately preceding charge,
Although the value Ahx of the discharge amount corresponding to the actually measured internal resistance Rm was obtained on the previous Ram map, the actually measured internal resistance Rm was substituted into the initial internal resistance characteristic (the initial Ram map), and the actually measured internal resistance Rm was obtained on the initial Ram map. The value Ahx of the discharge amount corresponding to the resistance Rm may be obtained.

Correction of internal resistance sudden increase phenomenon at the end of discharge 2
(Step S114) Next, the ratio between the current value Ahm of the discharge amount Ah and the value Ahx of the discharge amount on the previous Ram map is obtained, and the ratio indicates the axis indicating the discharge amount on the two-dimensional plane indicating the previous Ram map. An operation (capacity reduction operation) for proportionally compressing the discharge amount axis (referred to as a discharge amount axis) is performed to obtain a current corrected internal resistance characteristic (current Ram map).

In S114, the discharge amount axis of the previous Ram map was proportionally compressed by the ratio of the current value Ahm of the discharge amount Ah to the value Ahx of the discharge amount on the previous Ram map.
Instead, the current value Ahm of the discharge amount Ah and the initial Ram
Initial Ram from the ratio to the value of discharge amount Ahxini on the map
The discharge amount axis of the map may be proportionally compressed. Since the internal resistance sudden increase phenomenon at the end of discharge is a phenomenon appearing at the end of discharge, the correction of the previous internal resistance characteristic (previous Ram map) by the compression operation of the discharge amount axis is performed by detecting the internal resistance sudden increase in S110. The compression operation of the discharge amount axis is not performed in the discharge amount range larger than the discharge amount value at the time point.

Thus, the sudden increase in the internal resistance at the end of the discharge is reflected in the previous corrected internal resistance characteristic (previous Ram map) indicating the relationship between the corrected internal resistance Ramend and the discharge amount Ah, and the current corrected internal resistance characteristic (the current Ram map) is reflected. Map). Correction 1 for Increase in Internal Resistance Due to Battery Deterioration (Step S116) Next, in the determinations in S106 and S110, when it is determined that the discharge is in a shallow discharge amount range, or when it is determined that the internal resistance has not increased sharply. Is the value of the corrected internal resistance Ramend (referred to as the previous value) Rambefo corresponding to the current value Ahm of the discharge amount Ah on the previous Ram map.
re is compared with the measured internal resistance Rm.
It is checked whether or not m is larger than a threshold value obtained by multiplying the equivalent internal resistance value Rambeforex on the previous Ram map by a predetermined constant z. If it is larger, the internal resistance increase due to battery deterioration is corrected by the previous correction. Internal resistance characteristics (previous R
It is determined that the correction has progressed to the extent that the am map (am map) needs to be modified, and the process proceeds to the next step S120. In the following case, an increase in internal resistance due to battery deterioration requires modification of the previous corrected internal resistance characteristic (previous Ram map). It is determined that it has not progressed so much, and the process jumps to S122. Correction 2 for Increase in Internal Resistance Due to Battery Deterioration (Step S120) Next, the axis (internal resistance axis) indicating the internal resistance of the two-dimensional plane on which the previous Ram map is displayed is the measured internal resistance Rm
The current value of the corrected internal resistance (current Ra) is expanded at a ratio of the internal resistance value Rambefore on the previous Ram map corresponding to the current value Ahm of the discharge amount Ah (resistance value is increased).
m map). In other words, the corrected internal resistance value Ram0 on the current Ram map for a certain discharge amount value Ah0
Is the ratio (Rm0 / Rambefore0) between the measured internal resistance value Rm0 and the previous internal resistance value Rambefore0 for the discharge amount value Ah0, respectively, and the corrected internal resistance value R on the previous Ram map for the discharge amount value Ah0.
am0.

As a result, it is possible to obtain the current corrected internal resistance characteristic (Ram map) taking into account the increase in the internal resistance due to the deterioration of the battery. As a result, an increase in internal resistance due to normal battery deterioration is obtained by elongation of the internal resistance axis in S120, and a specific increase in internal resistance at the end of discharge is S1.
14 and can be obtained by compression of the discharge amount axis.

Correction of open-circuit voltage drop due to memory effect 1
(Steps S122, S124) In the next S122, it is checked whether or not the discharge has reached the discharge amount value Ahx at the start of the immediately preceding charging operation, and if not, the process proceeds to S126. A
The voltage difference ΔV between the value of the open circuit voltage OCV at the current value Ahx of h (the open circuit voltage OCVm at the end of the discharge) and the value corresponding to the current value Ahx of the current discharge amount Ah on the initial open circuit voltage characteristic is calculated as the current discharge The amount Ah is stored in pairs with the current value Ahx (S124), and the process proceeds to S126. This is to store that the open circuit voltage OCV due to the memory effect decreases by ΔV with respect to the discharge after the discharge amount Ahx at the next discharge.

Correction of open-circuit voltage drop due to memory effect 2
(Step S126) In this step, the open-circuit voltage characteristics are corrected. The correction of the open-circuit voltage is performed as follows. First, in the discharge amount range charged in the immediately preceding charging operation, it is considered that the decrease in the open-circuit voltage OCV due to the memory effect has been eliminated, and the initial open-circuit voltage characteristic is used as the current open-circuit voltage characteristic. In step 1, one or a plurality of the pairs stored in step S124 are deleted.

Next, in the discharge amount range in which charging was not performed in the immediately preceding charging operation, it is considered that the decrease in the open circuit voltage OCV due to the memory effect remains, and this discharge amount range is stored in S124 up to now. Based on one or a plurality of pairs of the discharge amount value at the end of the discharge and the voltage difference ΔV, the axis (open voltage axis) indicating the open circuit voltage OCV on the initial open circuit voltage characteristic (OCVini map) is moved in the voltage decreasing direction. An operation is performed by sliding by the voltage difference ΔV to obtain the corrected open-circuit voltage characteristic. Thereby, the deterioration of the electromotive voltage due to the memory effect can be represented in the corrected open-circuit voltage characteristic.

Note that the slide operation may be performed a plurality of times. For example, let us consider a point in time when the battery is first discharged from a full charge to a discharge amount value of 100 Ah, then discharged to a discharge amount value of 70 Ah after being fully charged, and then discharged to a discharge amount value of 50 Ah after the full charge. At this time, the open circuit voltage OCV has almost recovered to the initial open circuit voltage from the discharge amount of 0 Ah to 70 Ah, but the open circuit voltage OCV from the initial open circuit voltage has decreased by the voltage difference ΔV1 at the discharge amount value of 70 Ah, At the discharge amount value of 100 Ah, the open circuit voltage OCV decreases from the initial open circuit voltage by the voltage difference ΔV2.

Therefore, the current open-circuit voltage characteristic is determined by shifting the level of the initial open-circuit voltage by the voltage difference ΔV1 at the discharge amount value of 70 Ah, and further shifting the level of the initial open-circuit voltage by the voltage difference ΔV2 at the discharge amount value of 100 Ah. be able to. Calculation of Discharge Characteristics at Reference Discharge Power Value (S128) Next, discharge at the reference discharge power value is performed using the current corrected internal resistance characteristics obtained at S114 or S120 and the current corrected open-circuit characteristics obtained at S126. Calculate the characteristics. Here, the discharge characteristic at the reference discharge power value is a characteristic indicating the relationship between the output voltage (discharge voltage) V of the battery and the discharge amount Ah when discharging a predetermined reference discharge power (here, 2 kW). It is.

More specifically, the discharge voltage V corresponding to an arbitrary value of the discharge amount Ah includes an open-circuit voltage value OCV ′ obtained from the corrected open-circuit voltage characteristic corresponding to the value of the discharge amount Ah, and a discharge amount Ah Is calculated from the internal resistance value R ′ obtained from the corrected internal resistance characteristic in accordance with the following quadratic function equation. Here, W is the reference discharge power value, and A is this discharge amount Ah
Is the discharge current value at.

V = OCV′−R ′ · A = OCV′−R ′ · W / V · Calculation of Remaining Capacity (S130) In this step, the predetermined discharge power (2 kW in this case) obtained in S128 is used. The discharge characteristics are integrated from the current value Ahm of the discharge amount Ah to a discharge amount at which the battery can no longer be discharged at a predetermined reference discharge power, a remaining capacity at which the reference discharge power can be discharged is obtained, and the process returns to the main routine. (Effects of Embodiment) In this embodiment described above, since the remaining capacity is obtained from the discharge characteristics obtained based on the internal resistance characteristics and the open-circuit voltage characteristics, it is possible to calculate the remaining capacity more accurately than before.

That is, in a battery having a memory effect,
The applicant of the present invention stated that the decrease in the remaining capacity due to the memory effect can be expressed not as an increase in the internal resistance but as a decrease in the open-circuit voltage, and the decrease in the remaining capacity due to the deterioration of the battery can be expressed as an increase in the internal resistance rather than a decrease in the open-circuit voltage. This is shown in the prior art of the application. What is important here is a value at which the internal resistance changes according to a discharge amount or a remaining capacity, or more precisely, a function according to a discharge amount or a remaining capacity with respect to a full charge amount. In order to compensate, it is required to compress the discharge amount axis of the discharge characteristic indicating the discharge voltage-discharge capacity by this function. On the other hand, the decrease in open-circuit voltage due to the memory effect is constant with respect to the value of each discharge amount. It is necessary to lower the level of the discharge amount axis in the discharge characteristics indicating the following.

However, in the above-described prior art of the present applicant, the voltage difference between the discharge voltage in the discharge before charging immediately before the occurrence of a certain discharge amount and the discharge voltage measured this time in the same discharge amount is measured. Of these, the ratio of the component caused by the memory effect (the voltage component to be level-shifted) and the component caused by the battery degradation (the voltage component to be compensated by the compression of the discharge amount axis) is unknown, and the level shift compensation is accurately performed. And capacity axis compression compensation cannot be performed, which results in a remaining capacity calculation error.

On the other hand, in this embodiment, by using the internal resistance characteristic and the open-circuit voltage OCV characteristic, the increase in the internal resistance due to the deterioration of the battery can be accurately handled by compressing the discharge amount axis or extending the internal resistance axis. In addition, since the open-circuit voltage drop due to the memory effect can be accurately dealt with by sliding the open-circuit voltage axis, the remaining capacity after the present time can be calculated by pairing the initial open-circuit voltage characteristic and the initial internal resistance characteristic, or the previous open-circuit voltage characteristic and the previous open-circuit voltage characteristic. It can be accurately obtained based on the pair of the internal resistance characteristics and the actually measured open-circuit voltage value and internal resistance value.

Further, as the deterioration of the battery progresses, the phenomenon that the internal resistance sharply increases at the end of discharging of the battery is discriminated and dealt with, so that the remaining capacity can be calculated more accurately. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a battery remaining capacity calculating device according to the present invention.

FIG. 2 is a schematic characteristic diagram showing a relationship between a discharge amount Ah and a discharge voltage V.

FIG. 3 is a schematic characteristic diagram showing a relationship between a discharge amount Ah and an internal resistance r.

FIG. 4 is a schematic characteristic diagram showing a relationship between a discharge amount Ah and an open-circuit voltage map OCV.

FIG. 5 is a flowchart illustrating a remaining capacity calculation process 1;

FIG. 6 is a flowchart showing a remaining capacity calculation process 2;

FIG. 7 is a flowchart illustrating a remaining capacity calculation process 2;

[Explanation of symbols]

 1 is a battery, 4 is a controller, 5 is a current sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G016 CA03 CB06 CB11 CB12 CB13 CB21 CB22 CC01 CC03 CC04 CC27 5G003 CA01 CA11 CB01 CB07 EA05 EA09 GC04 GC05 5H030 AA08 AS08 FF42 FF44 5H115 PA14 PG04 PI16 PU05 QN03 TI05 TI05 DD03 EB26 EB39 FF04 FF14 FF22 LL10

Claims (7)

[Claims] 1. A detecting means for detecting a discharge voltage and a discharge current of a chargeable / dischargeable battery; a discharge amount calculating means for calculating a current value of a discharge amount based on the discharge current A; Open voltage calculation means for calculating the current value of the internal resistance of the battery and the current value of the open voltage, an internal resistance characteristic indicating a past relationship between the internal resistance of the battery and the discharge amount, and an open voltage and a discharge of the battery. Discharge characteristic storage means for storing an open voltage characteristic indicating a past relationship with the amount, a remaining capacity for calculating a remaining capacity based on the current value of the internal resistance and the current value of the open voltage, and the internal resistance characteristic and the open voltage characteristic A battery remaining capacity calculation device, comprising: calculation means. 2. The battery remaining capacity calculating device according to claim 1, wherein the remaining capacity calculating means deforms the past open-circuit voltage characteristic by a predetermined function having a current value of the open-circuit voltage as a variable. Forming the current open-circuit voltage characteristic for calculating the remaining capacity; deforming the internal resistance characteristic in the past with a predetermined function using the current value of the internal resistance as a variable; A battery remaining capacity calculating device for forming a characteristic, and calculating a remaining capacity based on the current internal resistance characteristic and the current open voltage characteristic. 3. The battery remaining capacity calculating device according to claim 2, wherein the remaining capacity calculating means includes: the discharge voltage and the discharge amount obtained based on the current internal resistance characteristic and the current open voltage characteristic. And calculating a remaining capacity by integrating a discharge characteristic indicating a relationship from the current discharge amount value to a predetermined discharge end discharge amount value to calculate a remaining capacity. 4. The battery remaining capacity calculating device according to claim 2, wherein the remaining capacity calculating means includes: a virtual open voltage value corresponding to a current value of the discharge amount on the past open voltage characteristics; The voltage difference between the current value and the current value is stored for each discharge amount range in which the amount of the memory effect is different, and the past open voltage characteristics are slid by the voltage difference for each discharge amount range, and A battery remaining capacity calculating device characterized by forming the open-circuit voltage characteristic of the battery. 5. The battery remaining capacity calculating device according to claim 2, wherein said remaining capacity calculating means includes: a virtual internal resistance value corresponding to a current value of said discharge amount on said past internal resistance characteristic; A remaining capacity calculation device for a battery, wherein a resistance ratio between a current resistance value and a current value is obtained, and the past internal resistance characteristic is extended by the resistance ratio to form the current internal resistance characteristic. 6. The battery remaining capacity calculating device according to claim 2, wherein said remaining capacity calculating means includes: a virtual discharge amount value corresponding to a current value of said internal resistance on said past internal resistance characteristic; A remaining capacity calculating device for a battery, wherein a discharge amount ratio between the current amount and a current value is obtained, and the past internal resistance characteristic is compressed by the discharge amount ratio to form the current internal resistance characteristic. 7. The battery remaining capacity calculating device according to claim 6, wherein the remaining capacity calculating means is configured to determine the discharge amount ratio when the discharge is deep and the current value of the internal resistance is greater than a predetermined value. A remaining capacity calculating device for a battery, wherein the current internal resistance characteristic is obtained by the compression based on the following.