JP6946691B2 - Power storage device and open circuit voltage estimation method - Google Patents

Description

The present invention relates to a power storage device for estimating open circuit voltage and a method for estimating open circuit voltage.

When estimating the state of charge (SOC) of a battery, simply obtaining the charge rate based on the current integration will gradually increase the charge rate obtained based on the current integration due to current measurement errors and the like. It deviates from. Therefore, the charge rate is estimated based on the open circuit voltage (OCV) acquired after the polarization is eliminated, and the estimated charge rate is corrected to be regarded as the actual charge rate.

As a related technique, for example, there is Patent Document 1.

Japanese Unexamined Patent Publication No. 2004-109007

However, if charging / discharging is started before the polarization is eliminated, the open circuit voltage after the polarization is eliminated cannot be obtained, so that the charge rate cannot be estimated using the open circuit voltage after the polarization is eliminated. In that case, the charge rate cannot be corrected, and the charge rate deviates from the actual charge rate.

An object of one aspect of the present invention is to provide a power storage device capable of estimating an open circuit voltage after polarization elimination before polarization elimination and a method for estimating open circuit voltage.

The power storage device according to the present invention includes a battery and a control circuit for controlling charging / discharging of the battery.
The control circuit acquires the open circuit voltage measured at regular intervals from the battery charge / discharge end time to the polarization elimination time, which is considered to have eliminated the polarization of the battery, and continuously acquires the open circuit voltage measured at regular intervals. The open circuit voltage after depolarization of the battery is estimated using the measured open circuit voltage at the three points and the equal ratio sequence.

Further, the control circuit estimates the open circuit voltage OCVe after the charge / discharge is completed and the polarization is eliminated by using the following equation.

V1, V2, and V3 indicate open circuit voltages at three points measured continuously at regular time intervals.

Further, the control circuit uses the four open circuit voltages Va1, Va2, Va3, and Va4 measured continuously at regular time intervals, and uses the following equation to set the first ratio A and the second ratio B. Is calculated.
A = (Va2-Va3 / Va1-Va2)
B = (Va3-Va4 / Va2-Va3)
Subsequently, when the difference between the first ratio A and the second ratio B is within a predetermined range, the control circuit selects three consecutive points from the four open circuit voltages Va1, Va2, Va3, and Va4. The open circuit voltages are V1, V2, and V3.

Further, in the control circuit, the open circuit voltages Vb1, Vb2, and Vb3 at three points measured continuously at regular intervals are such that the open circuit voltage Vb1 is larger than the open circuit voltage Vb2 and the open circuit voltage Vb2 is higher than the open circuit voltage Vb2 after charging is completed. The first condition that is larger than the open circuit voltage Vb3, or the second condition that the open circuit voltage Vb1 is smaller than the open circuit voltage Vb2 and the open circuit voltage Vb2 is smaller than the open circuit voltage Vb3 after the end of discharging is satisfied. In this case, the three open circuit voltages Vb1, Vb2, and Vb3 are set to the open circuit voltages V1, V2, and V3.

The control circuit acquires the open circuit voltage measured at regular intervals after the standby time has elapsed from the charge / discharge end time. The standby time means that from the charge / discharge end time, all the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery after the charge / discharge end are eliminated except for the polarization having the longest polarization elimination time. It is the time until the time that can be considered.

In the open circuit voltage estimation method according to another embodiment of the present invention, the control circuit that controls the charging / discharging of the battery is from the charging / discharging end time of the battery to the polarization elimination time at which the polarization of the battery is considered to be eliminated. In time, the open circuit voltage measured at regular time intervals is acquired.

Subsequently, the control circuit estimates the open circuit voltage after depolarization of the battery by using the three points of open circuit voltage and the geometric progression measured continuously at regular time intervals.

The open circuit voltage after depolarization can be estimated before depolarization.

It is a figure which shows one Example of the power storage device. It is a figure which shows the change of the voltage of the polarization elimination time of a battery after charging. It is a figure which shows the change of the voltage of the polarization elimination time of a battery after discharge. It is a figure which shows one Example of the open circuit voltage estimation method.

Hereinafter, embodiments will be described in detail based on the drawings.
<Embodiment 1>
FIG. 1 is a diagram showing an embodiment of the power storage device 1. The power storage device 1 includes an ammeter 2, a voltmeter 3, a control circuit 4, a battery B1, a switch SW1, and a switch SW2. The power storage device 1 may be, for example, a battery pack mounted on a vehicle (for example, PHV: Plug-in Hybrid Vehicle or the like).

The ammeter 2 measures the current flowing through the battery B1. The voltmeter 3 measures the voltage across the battery B1.
The control circuit 4 has an open circuit voltage estimation unit 5 and a charge rate estimation unit 6. Further, the control circuit 4 controls the charging / discharging of the battery B1.

The battery B1 is a secondary battery provided in the battery pack, and is, for example, a secondary battery such as a nickel hydrogen battery or a lithium ion battery, or a power storage element. As the battery B1, an assembled battery in which a plurality of batteries are connected may be used.

The switches SW1 and SW2 are connected to the C contact side from the start of charging to the end of charging, and are connected to the D contact side from the start of discharging to the end of discharging. The switches SW1 and SW2 may be, for example, a relay or a semiconductor element. It should be noted that only one of the switches SW1 and SW2 may be provided. Further, there may be one switch for the charging device CHG and one switch for the load LD.

The circuit configuration of the power storage device 1 will be described.
The positive electrode terminal (+) of the battery B1 is connected to one terminal of the ammeter 2 and one terminal of the voltmeter 3. The other terminal of the ammeter 2 is connected to the B terminal of the switch SW1. The output terminal of the ammeter 2 is connected to the control terminal P1 of the control circuit 4.

The negative electrode terminal (−) of the battery B1 is connected to the other terminal of the voltmeter 3 and the B terminal of the switch SW2. The output terminal of the voltmeter 3 is connected to the control terminal P2 of the control circuit 4.
The C terminal of the switch SW1 is connected to the positive electrode terminal (+) of the charging device CHG. The D terminal of the switch SW1 is connected to the positive electrode terminal (+) of the load LD (for example, a motor, an auxiliary machine, etc.). The C terminal of the switch SW2 is connected to the negative electrode terminal (−) of the charging device CHG. The D terminal of the switch SW2 is connected to the negative electrode terminal (−) of the load LD. Further, the control terminals of the switches SW1 and SW2 are connected to the control terminal P3 of the control circuit 4.

The control circuit 4 will be described.
As the control circuit 4, for example, a circuit using a CPU (Central Processing Unit), a multi-core CPU, a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.) can be considered. Further, the control circuit 4 is provided with a storage unit inside or outside, and reads and executes a program for controlling each unit of the power storage device 1 stored in the storage unit.

When charging the battery B1, the control circuit 4 connects the contacts of the switches SW1 and SW2 to the C contact side. Further, the control circuit 4 acquires a signal or information corresponding to the current (charging current) flowing from the charging device CHG to the battery B1 during charging from the current meter 2, and also acquires the voltage (closed circuit voltage) of the battery B1 being charged. The signal or information corresponding to is acquired from the voltmeter 3. Further, in the control circuit 4, when the battery B1 is discharged, the contacts of the switches SW1 and SW2 are both connected to the D contact side. Further, the control circuit 4 acquires the current (discharge current) flowing from the battery B1 to the load LD during discharging from the current meter 2, and acquires the voltage (closed circuit voltage) of the battery B1 being discharged from the voltmeter 3. .. Further, when the control circuit 4 acquires the open circuit voltage after charging / discharging the battery B1, the contacts of the switches SW1 and SW2 are not connected to both the C contact and the D contact, and the opening circuit voltage after charging / discharging the battery B1 is prevented. Is obtained from the voltmeter 3. The open circuit voltage after charging / discharging is the voltage when no current is flowing through the battery B1 even when the contacts of the switches SW1 and SW2 are connected to the C contact or the D contact. May be good.

The open circuit voltage estimation unit 5 will be described.
The open circuit voltage estimation unit 5 measures the open circuit voltage for each Toc for a certain period of time from the charging end time ct of the battery B1 in FIG. 2 to the polarization elimination time tocvc, which is considered to have eliminated the polarization of the battery B1. To get.

FIG. 2 is a diagram showing a change in voltage during the polarization elimination time of the battery B1 after charging. The curve 21 in FIG. 2 shows the voltage of the battery B1 after charging. The time Tac in FIG. 2 indicates the time (polarization elimination time) from the charging end time ct to the polarization elimination time tocvc, which is considered to have eliminated the polarization of the battery B1.

The time Tbc in FIG. 2 is the time t1c in which it can be considered that all the polarizations other than the polarization having the longest polarization elimination time among the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 after the end of charging are eliminated. The time from to the polarization elimination time tocvc is shown. In other words, the time Tbc indicates the time in which only one of the three polarizations is not resolved after the waiting time Tmc has elapsed in the time Tac. The standby time Tmc is such that from the charging end time ct of the battery B1, all the polarizations other than the polarization having the longest polarization elimination time among the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 after the charging is completed are eliminated. It is the time until the time t1c, which can be regarded as having been done. In other words, the waiting time Tmc indicates the time during which the three or two polarizations have not been resolved in the time Tac.

In the case of a lithium ion battery using a silicon negative electrode, the polarization elimination time of the negative electrode is the longest. Further, the waiting time Tmc is obtained by an experiment or a simulation and is stored in the storage unit in advance.

The open circuit voltage Vc in FIG. 2 indicates the open circuit voltage at the charging end time ct. The open circuit voltage V1c in FIG. 2 indicates the open circuit voltage measured at the time t1c after the standby time Tmc has elapsed. The open circuit voltages V2c, V3c, and V4c in FIG. 2 indicate the open circuit voltages measured continuously at every Toc for a certain period of time from the time t1c. That is, the open circuit voltages V1c, V2c, V3c, and V4c indicate the open circuit voltages acquired at the times t1c, t2c, t3c, and t4c in FIG. The Toc for a certain period of time is obtained by an experiment or a simulation and is stored in a storage unit in advance.

The open circuit voltage OCVc in FIG. 2 indicates the actual open circuit voltage acquired at the polarization elimination time tocvc.
Subsequently, the open circuit voltage estimation unit 5 uses the three points of the open circuit voltage and the geometric progression measured continuously at each Toc for a certain period of time at the time Tbc to eliminate the polarization of the battery B1. Estimate OCVe. The open circuit voltage estimation unit 5 estimates the open circuit voltage OCVe after depolarization after charging using Equation 1.

That is, the open circuit voltage OCVe after depolarization after charging is estimated by using Equation 2 showing the convergence destination of the geometric progression (infinite geometric series).

The first term of the geometric progression included in Equations 1 and 2 corresponds to (V1-V2), and the common ratio of the geometric progression included in Equations 1 and 2 is (V2-V3) / ( V1-V1- ). Corresponds to V2). The geometric progression included in Equations 1 and 2 has a common ratio smaller than 1.

Further, the three-point open circuit voltage used in the formulas 1 and 2 after charging corresponds to, for example, the open circuit voltages V1c, V2c, V3c and the open circuit voltages V2c, V3c, V4c of FIG.
In this way, when the change in the voltage of the battery B1 having a long time Tac during the polarization elimination time can be expressed by a geometric progression, the open circuit voltage that approximates the open circuit voltage OCVc before the polarization elimination and after the polarization elimination is used by using Equation 2. OCVe can be estimated.

Further, the reason why the open circuit voltage is continuously acquired at every Toc for a certain period of time after the standby time Tmc has elapsed is that the polarization generated in each of the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 is not eliminated in the standby time Tmc. Therefore, the voltage change (voltage difference) is not stable, and the voltage change during the polarization elimination time of the battery B1 cannot be represented by using the equal ratio sequence. For example, when the polarization having the longest polarization elimination time is caused by the negative electrode, after the standby time Tmc elapses, only the polarization caused by the negative electrode of the battery B1 is generated, so that the voltage change is stable and the polarization elimination time of the battery B1 is satisfied. The change in the voltage of can be expressed using a geometric progression. Therefore, after the standby time Tmc has elapsed, by continuously acquiring the open circuit voltage at every Toc for a certain period of time, the estimated open circuit voltage OCVe after the polarization is eliminated after charging is charged using the geometric progression. It can be accurately approximated to the open circuit voltage OCVc of.

Further, the open circuit voltage estimation unit 5 measures the opening time for each Tod for a certain period of time from the discharge end time td of the battery B1 in FIG. 3 to the polarization elimination time tocvd, which is considered to have eliminated the polarization of the battery B1. Get the circuit voltage.

FIG. 3 is a diagram showing a change in voltage during the polarization elimination time of the battery B1 after discharge. The curve 31 in FIG. 3 shows the voltage of the battery B1 after discharging. The time Tad in FIG. 3 indicates the time (polarization elimination time) from the discharge end time td to the polarization elimination time tocvd, which is considered to have eliminated the polarization of the battery B1.

The time Tbd in FIG. 3 is the time t1d in which it can be considered that all the polarizations other than the polarization having the longest polarization elimination time among the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 after the end of the discharge are eliminated. The time from to the polarization elimination time tocvd is shown. In other words, the time Tbd indicates the time in which only one of the three polarizations is not resolved after the waiting time Tmd has elapsed in the time Tad. The standby time Tmd is such that from the discharge end time td of the battery B1, all the polarizations other than the polarization having the longest polarization elimination time among the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 after the discharge is eliminated are eliminated. It is the time until the time t1d which can be regarded as having been done. In other words, the waiting time Tmd indicates the time during which the three polarizations or the two polarizations are not resolved at the time Tad.

In the case of a lithium ion battery using a silicon negative electrode, the polarization elimination time of the negative electrode is the longest. Further, the standby time Tmd is obtained by an experiment or a simulation and is stored in the storage unit in advance.

The open circuit voltage Vd in FIG. 3 indicates the open circuit voltage at the discharge end time td. The open circuit voltage V1d in FIG. 3 indicates the open circuit voltage measured at the time t1d after the standby time Tmd has elapsed. The open circuit voltages V2d, V3d, and V4d in FIG. 3 indicate the open circuit voltages measured continuously for each Tod for a certain period of time from the time t1d. That is, the open circuit voltages V1d, V2d, V3d, and V4d indicate the open circuit voltages acquired at the times t1d, t2d, t3d, and t4d in FIG. Tod for a certain period of time is obtained by an experiment or a simulation and is stored in a storage unit in advance.

The open circuit voltage OCVd in FIG. 3 indicates the actual open circuit voltage acquired at the polarization elimination time tocvd.
Subsequently, the open circuit voltage estimation unit 5 uses the three points of the open circuit voltage and the geometric progression measured continuously for each Tod for a certain period of time at the time Tbd, and the open circuit voltage after the polarization of the battery B1 is eliminated. Estimate OCVe. That is, the open circuit voltage estimation unit 5 estimates the open circuit voltage OCVe after the polarization is eliminated after the discharge by using the equations 1 and 2.

The three-point open circuit voltage used in Equations 1 and 2 after discharge corresponds to, for example, the open circuit voltages V1d, V2d, V3d and the open circuit voltages V2d, V3d, V4d in FIG.
In this way, when the change in the voltage of the battery B1 having a long time Tad can be expressed by a geometric progression, the open circuit voltage close to the open circuit voltage OCVd before the polarization elimination and after the polarization elimination is used by using Equation 2. OCVe can be estimated.

Further, the reason why the open circuit voltage is continuously acquired at every Tod for a certain period of time after the standby time Tmd has elapsed is that the polarization generated in each of the positive electrode, the negative electrode, and the electrolytic solution of the battery B1 is not eliminated in the standby time Tmd. Therefore, the voltage change (voltage difference) is not stable, and the voltage change during the polarization elimination time of the battery B1 cannot be represented by using the equal ratio sequence. For example, when the polarization having the longest polarization elimination time is caused by the negative electrode, after the standby time Tmd elapses, only the polarization caused by the negative electrode of the battery B1 is generated, so that the voltage change is stable and the polarization elimination time of the battery B1 is satisfied. The change in the voltage of can be expressed using a geometric progression. Therefore, after the standby time Tmd has elapsed, by continuously acquiring the open circuit voltage at every Toc for a certain period of time, the estimated open circuit voltage OCVe after discharge elimination is discharged using a geometric progression. It can be accurately approximated to the open circuit voltage OCVd of.

The charge rate estimation unit 6 will be described.
The charge rate estimation unit 6 estimates the charge rate using the open circuit voltage OCVe after polarization elimination estimated by the open circuit voltage estimation unit 5.

In this way, since the open circuit voltage OCVe after polarization elimination can be obtained, the charge rate can be estimated accurately even before polarization elimination.
<Modification example 1>
The open circuit voltage estimation unit 5 continuously measures four points for a certain period of time from the charging end time ct of the battery B1 to the polarization elimination time tocvc, which is considered to have eliminated the polarization of the battery B1. Using the open circuit voltages Va1, Va2, Va3, and Va4, the first ratio A and the second ratio B are calculated by the formulas 3 and 4.

A = (Va2-Va3 ) / ( Va1-Va2) Equation 3
B = (Va3-Va4 ) / ( Va2-Va3) Equation 4
For example, when the open circuit voltages V1c, V2c, V3c, and V4c acquired at the time Tbc in FIG. 2 are used as the open circuit voltages Va1, Va2, and Va3 of the formula 3 and the open circuit voltages Va2, Va3, and Va4 of the formula 4. Since the open circuit voltages V1c, V2c, V3c, and V4c are all on the curve 21 of FIG. 2, the first ratio A and the second ratio B have the same value. Further, when any of the open circuit voltages V1c, V2c, V3c, and V4c is not on the curve 21 of FIG. 2, the first ratio A and the second ratio B have different values.

Further, the open circuit voltage estimation unit 5 continuously measures the time from the discharge end time td of the battery B1 to the polarization elimination time tocvd, which is considered to have eliminated the polarization of the battery B1, for a certain period of time. Using the point open circuit voltages Va1, Va2, Va3, and Va4, the first ratio A and the second ratio B are calculated by the equations 3 and 4.

For example, when the open circuit voltages V1d, V2d, V3d, and V4d acquired at the time Tbd in FIG. 3 are used as the open circuit voltages Va1, Va2, and Va3 of the formula 3 and the open circuit voltages Va2, Va3, and Va4 of the formula 4. Since the open circuit voltages V1d, V2d, V3d, and V4d are all on the curve 31 of FIG. 3, the first ratio A and the second ratio B have the same value. Further, when any of the open circuit voltages V1d, V2d, V3d, and V4d is not on the curve 31 of FIG. 3, the first ratio A and the second ratio B have different values.

Subsequently, when the difference between the first ratio A and the second ratio B is within a predetermined range, the open circuit voltage estimation unit 5 has three points continuous from the four open circuit voltages Va1, Va2, Va3, and Va4. Is selected, and the open circuit voltages V1, V2, and V3 are set. That is, when the difference between the first ratio A and the second ratio B is within a predetermined range, the open circuit voltage estimation unit 5 has any of the open circuit voltages Va1, Va2, Va3 or the open circuit voltages Va2, Va3, and Va4. Select one.

The predetermined range is a value for determining whether or not the open circuit voltages at the four points are within a range that can be regarded as a geometric progression. It is obtained by an experiment or a simulation and is stored in the storage unit in advance. There is. For example, the predetermined range is a range in which the open circuit voltage OCVe after depolarization can be estimated accurately even if any of the four points of the open circuit voltage is not on the curve 21 of FIG. 2 or the curve 31 of FIG. ..

Further, when the difference between the first ratio A and the second ratio B is not within a predetermined range, the open circuit voltage estimation unit 5 continuously measures the open circuit voltage (Va2) at the next four points for each Toc for a certain period of time. , Va3, Va4 and the newly measured open circuit voltage Va5) are used to calculate the first ratio A and the second ratio B, and the difference between the first ratio A and the second ratio B is within a predetermined range. It is determined whether or not it is.

According to the first modification, the open circuit voltages Va1, Va2, Va3 or the open circuit voltages Va2, Va3, and Va4 in the range that can be regarded as an equal ratio sequence are set to the open circuit voltages V1, V2 of the equations 1 and 2. Since it can be used as V3, the open circuit voltage OCVe after charging / discharging can be estimated accurately. Further, since the open circuit voltage OCVe can be estimated accurately, the charge rate can be estimated accurately even before the polarization is eliminated.

<Modification 2>
The open circuit voltage estimation unit 5 continuously measures three points for a fixed period of time from the charging end time ct of the battery B1 to the polarization elimination time tocvc, which is considered to have eliminated the polarization of the battery B1. When the open circuit voltages Vb1, Vb2, and Vb3 satisfy the first condition (Vb1>Vb2> Vb3) in which the open circuit voltage Vb1 is larger than the open circuit voltage Vb2 and the open circuit voltage Vb2 is larger than the open circuit voltage Vb3. (When the tendency is decreasing), the open circuit voltages Vb1, Vb2, and Vb3 are set to the open circuit voltages V1, V2, and V3.

For example, when the open circuit voltages V1c, V2c, and V3c acquired at the time Tbc in FIG. 2 are set to the open circuit voltages Vb1, Vb2, and Vb3, the open circuit voltage V1c is larger than the open circuit voltage V2c and the open circuit voltage V2c is Since it is larger than the open circuit voltage V3c, the first condition is satisfied.

Further, the open circuit voltage estimation unit 5 continuously measures the time from the discharge end time td of the battery B1 to the polarization elimination time tocvd, which is considered to have eliminated the polarization of the battery B1, for a certain period of time. The open circuit voltages Vb1, Vb2, and Vb3 at the points satisfy the second condition (Vb1 <Vb2 <Vb3) in which the open circuit voltage Vb1 is smaller than the open circuit voltage Vb2 and the open circuit voltage Vb2 is smaller than the open circuit voltage Vb3. If there is (when there is an increasing tendency), the open circuit voltages Vb1, Vb2, and Vb3 are set to the open circuit voltages V1, V2, and V3.

For example, when the open circuit voltages V1d, V2d, and V3d acquired at the time Tbd in FIG. 3 are set to the open circuit voltages Vb1, Vb2, and Vb3, the open circuit voltage V1d is smaller than the open circuit voltage V2d, and the open circuit voltage V2d is Since it is smaller than the open circuit voltage V3d, the second condition is satisfied.

When the first condition or the second condition is not satisfied, the open circuit voltage estimation unit 5 uses the following three open circuit voltages Va2, Va3, and Va4 continuously measured at every Toc for a certain period of time. It is determined whether or not the first condition or the second condition is satisfied.

According to the second modification, when it can be considered that the change in the voltage of the battery B1 tends to decrease in the polarization elimination time after charging, or when the change in the voltage of the battery B1 tends to increase in the polarization elimination time after discharging. Since the open circuit voltages Vb1, Vb2, and Vb3 can be used as the open circuit voltages V1, V2, and V3 of the formulas 1 and 2, the open circuit voltage OCVe after charging and discharging can be estimated accurately. can. Further, since the open circuit voltage OCVe can be estimated accurately, the charge rate can be estimated accurately even before the polarization is eliminated.

<Embodiment 2>
FIG. 4 is a diagram showing an embodiment of the open circuit voltage estimation method. In step S1, the control circuit 4 acquires the open circuit voltage measured for each Toc for a certain period of time from the charging end time ct of the battery B1 to the polarization elimination time tocvc, which is considered to have eliminated the polarization of the battery B1. do. Further, in step S1, the control circuit 4 measures the open circuit voltage for each Tod for a certain period of time from the discharge end time td of the battery B1 to the polarization elimination time tocvd, which is considered to have eliminated the polarization of the battery B1. To get.

In step S2, the control circuit 4 determines whether or not the continuously measured open circuit voltage acquired in step S1 can be used. For example, a determination is made using the method described in the first modification or the second modification, and the open circuit voltage used in step S3 is selected.

In step S3, the control circuit 4 uses the three points of open circuit voltage and geometric progression measured continuously at every Toc for a certain period of time after charging is completed to obtain the open circuit voltage OCVe after the polarization of the battery B1 is eliminated. presume. Further, in step S3, the control circuit 4 uses the three-point open circuit voltage and the geometric progression measured continuously for each Tod for a certain period of time after the discharge is completed, and the open circuit voltage after the polarization of the battery B1 is eliminated. Estimate OCVe. The control circuit 4 estimates the open circuit voltage OCVe after the polarization of the battery B1 is eliminated by using, for example, Equation 2.

According to steps S1, S2, and S3, when the change in the voltage of the battery B1 at time Tbc can be expressed by a geometric progression after charging, the open circuit voltage OCVc after the polarization is eliminated before the polarization is eliminated by using Equation 2. The approximate open circuit voltage OCVe can be estimated. Further, when the change in the voltage of the battery B1 at time Tbd can be expressed by using a geometric progression after discharging, the open circuit voltage OCVe that approximates the open circuit voltage OCVd before and after the polarization elimination is used by using Equation 2. Can be estimated.

Further, according to steps S1, S2, and S3, after the standby time Tmc elapses after charging, the open circuit voltage measured continuously at every Toc for a certain period of time is acquired to obtain the open circuit voltage before the polarization is eliminated after charging. The open circuit voltage OCVe can be estimated accurately. Further, by continuously acquiring the open circuit voltage at every Tod for a certain period of time after the standby time Tmd has elapsed after the discharge, the open circuit voltage OCVe before the polarization elimination after the discharge can be estimated accurately.

Subsequently, in step S4, the control circuit 4 estimates the charge rate using the open circuit voltage OCVe after polarization elimination estimated in step S3.
According to step S4, since the open circuit voltage OCVe can be estimated accurately before the polarization is eliminated, the charge rate can be estimated accurately even before the polarization is eliminated.

Further, the present invention is not limited to the above embodiments, and various improvements and changes can be made without departing from the gist of the present invention.
For example, when the measured open circuit voltage deviates from the geometric progression after the completion of charging / discharging, the first term and the common ratio of the geometric progression may be corrected by using a coefficient, an offset, or the like.

Moreover, the present invention may be carried out only after charging or discharging. The charging / discharging in the present invention means charging or discharging.
Further, the standby time Tmc after charging and the standby time Tmd after discharging of the present invention may be the same or different.

Further, the open circuit voltage measured at regular intervals in the present invention is measured after the standby time has elapsed, but it is not limited to after the standby time has elapsed, and may be before the standby time has elapsed. However, it is possible to estimate the open circuit voltage after the polarization is eliminated more accurately by measuring after the standby time has elapsed.

1 Power storage device 2 Ammeter 3 Voltmeter 4 Control circuit 5 Open circuit Voltage estimation unit 6 Charge rate estimation unit B1 Battery CHG Charging device LD Load SW1, SW2 Switch

Claims (5)

Batteries and
A power storage device including a control circuit for controlling charging / discharging of the battery.
The control circuit
From the charge / discharge end time of the battery to the polarization elimination time, which is considered to have eliminated the polarization of the battery, the three open circuit voltages measured continuously at regular intervals are V1, V2, and V3, respectively. When the battery is depolarized, the open circuit voltage OCVe is estimated using the following equation.

A power storage device characterized by this. The power storage device according to claim 1.
The control circuit
Using the four open-loop voltages Va1, Va2, Va3, and Va4 measured continuously at regular time intervals, the first ratio A and the second ratio B were calculated using the following formula.
A = (Va2-Va3 ) / ( Va1-Va2)
B = (Va3-Va4 ) / ( Va2-Va3)
When the difference between the first ratio A and the second ratio B is within a predetermined range, three consecutive points are selected from the four points of open circuit voltage Va1, Va2, Va3, and Va4, and the open circuit voltage is selected. V1, V2, V3,
A power storage device characterized by this. The power storage device according to claim 1.
The control circuit
After charging is completed, the open circuit voltage Vb1 is larger than the open circuit voltage Vb2 and the open circuit voltage Vb2 is the open circuit voltage Vb2. The first condition that is larger than the circuit voltage Vb3, or the second condition that the open circuit voltage Vb1 is smaller than the open circuit voltage Vb2 and the open circuit voltage Vb2 is smaller than the open circuit voltage Vb3 after the end of discharging. If the conditions are satisfied, the open circuit voltages Vb1, Vb2, and Vb3 at the three points are set to the open circuit voltages V1, V2, and V3.
A power storage device characterized by this. The power storage device according to any one of claims 1 to 3.
The control circuit
After the standby time has elapsed from the charge / discharge end time, the open circuit voltage measured at regular intervals is acquired.
The waiting time is
From the charge / discharge end time, it can be considered that all the polarizations other than the polarization having the longest polarization elimination time among the polarizations caused by the positive electrode, the negative electrode, and the electrolytic solution of the battery after the charge / discharge end are eliminated. Time to
A power storage device characterized by this. It is a method of estimating the open circuit voltage of a battery.
The control circuit that controls the charging and discharging of the battery is
From the charge / discharge end time of the battery to the polarization elimination time, which is considered to have eliminated the polarization of the battery, the three open circuit voltages measured continuously at regular intervals are V1, V2, and V3, respectively. When the battery is depolarized, the open circuit voltage OCVe is estimated using the following equation.

An open-circuit voltage estimation method characterized by this.

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