JP7375473B2 - Energy storage amount estimating device, energy storage amount estimation method, and computer program - Google Patents

Description

The present invention relates to a storage amount estimating device, a storage amount estimation method, and a computer program for estimating a storage amount such as SOC (State of Charge) of a storage element.

BACKGROUND ART In recent years, in secondary batteries such as lithium ion batteries, a technique for estimating the SOC of a battery with high accuracy has been required. The OCV method and the current integration method are widely used as methods for estimating the SOC in a secondary battery. In the OCV method, the SOC is estimated based on a one-to-one correlation (SOC-OCV curve) between the OCV (Open Circuit Voltage) and the SOC of the secondary battery. In the current integration method, the SOC is calculated by integrating the charging and discharging current values of the secondary battery.

When calculating the SOC by the current integration method, the following equation (1) is calculated sequentially.
SOC _i =SOC _i-1 +I _i ×Δt _i /Q×100 (1)
SOC _i : SOC after update
SOC _i-1 : Previous SOC
I _i : Current value Δt _i : Time interval Q: Battery capacity (Available Capacity)

In the current integration method, the current SOC is estimated from the integrated value of the amount of electricity charged and discharged, and generally, if data can be obtained from a high-performance ammeter, the accuracy is high and the SOC can be monitored in real time. However, when estimating the SOC over a long period of time, estimation errors accumulate, so there is a problem that the accuracy decreases as the period becomes longer. Therefore, a method may be adopted in which the accumulated estimation errors are reset by using a combination of the OCV method, which estimates the SOC using only currently obtained information without using past history information.

However, a positive electrode active material such as lithium iron phosphate has a property called hysteresis, in which the voltage value and electrochemical characteristics for the same SOC change depending on the charging history and discharging history. Therefore, when these positive electrode active materials are used in a power storage device, the SOC-OCV curve changes depending on the charging and discharging history of the battery, breaking the one-to-one correspondence between OCV and SOC. It is not possible to reset the error accurately. As described above, there are problems in that the accuracy of SOC estimation is poor and battery control is difficult.

Patent Document 1 proposes a technique for accurately estimating OCV in consideration of charging/discharging history. The power storage member state estimation method disclosed in Patent Document 1 calculates the OCV correction amount of the power storage member based on parameters calculated based on the current value of the power storage member, and performs hysteresis correction to reduce errors due to OCV hysteresis. conduct.

Patent Document 2 proposes a technique for improving the accuracy of estimating the SOC of a power storage element by accurately converting the SOC-OCV curve into a function. In the approximation function creation method disclosed in Patent Document 2, data on the SOC-OCV curve of a power storage element is acquired. The midpoint is moved within a range in which the rate of change in OCV with respect to SOC of the SOC-OCV curve indicated by the acquired data is equal to or less than a predetermined threshold. For each intermediate point position, the degree of similarity is calculated between an approximated curve that approximates the characteristic curve of each divided range obtained by dividing the range using the intermediate point as a boundary, and data used to approximate the approximated curve. An approximation function is generated by approximating the characteristic curve using an approximation straight line for each division range with the intermediate point as the boundary for which the calculated degree of similarity is highest.

JP2015-166710 Patent 6171897

In Patent Document 1, OCV is corrected based on the integrated amount of electricity and the average current value at the time of switching to discharging after being charged, but a huge amount of data is acquired in advance in order to be able to respond to various patterns. Because it is necessary to correct OCV based on integrated values from the past to the present, such as integrated electricity amount and average current value, it is easy to accumulate calculation errors due to sequential calculations, so it is necessary to accurately estimate the correct SOC. I can't.

In Patent Document 2, an approximation function that expresses the SOC-OCV curve is obtained, but at the stage where no history information is included in the input data, it is impossible to express hysteresis behavior that changes depending on the history, and accurate SOC cannot be calculated with accuracy. cannot be estimated well.

An object of the present invention is to provide a storage amount estimation device, a storage amount estimation method, and a computer program that can estimate the storage amount with high accuracy even after a complicated usage history. Here, the amount of stored electricity means SOC, remaining discharge capacity, rated capacity ratio, etc. The rated capacity ratio refers to the ratio of the remaining discharge capacity of a battery to the rated capacity, and is a standardization of the remaining discharge capacity of a battery between 0 and 1 based on the rated capacity.

A storage amount estimating device according to the present invention is a storage amount estimating device for a storage element that has hysteresis due to a charge/discharge history in the correlation between a storage amount and a pseudo open circuit voltage, and the storage amount estimating device is a storage amount estimation device for a storage element that has hysteresis due to a charge/discharge history in the correlation between a storage amount and a pseudo open circuit voltage. a determination unit that determines a correlation between pseudo open circuit voltages; and a determination unit that estimates a storage amount in a discharge process based on the pseudo open circuit voltage and the determined correlation when the pseudo open circuit voltage in the discharge process is within a predetermined range; and an estimation section.

With the above configuration, it is possible to estimate with high accuracy the amount of electricity stored in a power storage element having an active material whose electricity storage amount-voltage value characteristic exhibits hysteresis.

It is a graph showing changes in the SOC-OCV curve depending on charge/discharge history. 3 is a graph showing changes in the rated capacity ratio r-OCV curve depending on charging and discharging history. FIG. 3 is an explanatory diagram for determining an r-OCV curve. It is a figure showing an example of a power storage module. It is a figure showing other examples of a power storage module. FIG. 3 is an exploded perspective view of the power storage module. FIG. 3 is a block diagram of a power storage module. It is a flowchart which shows the procedure of the electrical storage amount estimation process by CPU. This is a charge/discharge curve obtained by an SOC fluctuation test. FIG. 3 is a diagram showing the total SOC variation amount by an SOC variation test. FIG. 3 is an explanatory diagram for determining an r-OCV curve.

(Summary of embodiment)
The stored power amount estimating device according to the embodiment is a stored power amount estimating device for a power storage element that has hysteresis due to charging and discharging history in the correlation between the stored power amount and the pseudo open circuit voltage, and is configured to estimate the stored power amount and the amount of stored power corresponding to the stored power amount at the start of discharge. a determination unit that determines a correlation between pseudo open circuit voltages; and a determination unit that estimates a storage amount in a discharge process based on the pseudo open circuit voltage and the determined correlation when the pseudo open circuit voltage in the discharge process is within a predetermined range; and an estimation section.

Here, the pseudo open circuit voltage is the OCV obtained after a rest period and the voltage (pseudo OCV) obtained without a rest period when the storage element is used with a small current, such as dark current. including. In the following explanation, it will be simply referred to as "OCV".
The estimation method of Patent Document 1 considers that OCV hysteresis depends on the average current value and the integrated current value. However, the inventors of the present application have realized that OCV hysteresis does not depend on the current value, and that the behavior of hysteresis cannot be understood in detail unless the influence of the amount of stored electricity at the start of discharge on OCV hysteresis is taken into account. I found it. Furthermore, the inventors of the present application have discovered that there is an extremely strong linear proportional relationship between the amount of stored electricity and the pseudo open circuit voltage in a predetermined voltage section. In this way, by implementing the OCV method in a predetermined voltage section while taking into account the correlation between the amount of stored electricity and the pseudo open circuit voltage that changes due to hysteresis, it becomes possible to accurately determine the amount of stored electricity in the electricity storage element.
According to the above configuration, the correlation between the amount of stored electricity at the start of discharge and the pseudo open circuit voltage is determined in consideration of hysteresis, and the OCV method is implemented in a predetermined voltage section, so the influence of accumulation of errors during current integration is eliminated. This can be kept to a minimum, and the amount of electricity stored in the electricity storage element can be estimated with high accuracy.

In the above-mentioned power storage amount estimating device, the determining unit is configured to calculate the correlation between the power storage amount and the pseudo open-circuit voltage stored in advance for each power storage amount at the start of discharge, and the amount of change in the pseudo-open-circuit voltage between at least two points in the discharge process. and the amount of discharge, the correlation corresponding to the amount of stored electricity at the time of starting the discharge may be determined.

According to the above configuration, even if the correlation between the amount of stored electricity and the pseudo open-circuit voltage corresponding to the amount of electricity stored at the start of discharge at the current point in time is not stored in advance, only the amount of change in the pseudo-open-circuit voltage and the amount of discharge between the two points in time are stored. can be used to obtain the correlation between the current amount of stored electricity and the pseudo open circuit voltage. In other words, even if the amount of stored power at the start of discharge is not known, the amount of stored power can be estimated only from data between two points in time.

In the above-mentioned power storage amount estimating device, the correlation may be a characteristic curve showing a linear proportional relationship between a rated capacity ratio of the power storage element and a pseudo open circuit voltage.

According to the above configuration, it is possible to accurately determine the correlation between the amount of stored electricity and the pseudo open-circuit voltage at the present time, using the gradient obtained from the amount of change in the pseudo-open-circuit voltage and the amount of discharge between two points in time.

The stored power amount estimation method according to the embodiment is a stored power amount estimation method of a power storage element in which the correlation between the stored power amount and the pseudo open circuit voltage has hysteresis due to the charging/discharging history, and the method is a method for estimating the stored power amount of the power storage element, which has hysteresis due to the charge/discharge history in the correlation between the stored power amount and the pseudo open circuit voltage. a step of determining a correlation between pseudo open circuit voltages; and a step of estimating the amount of electricity stored in a discharge process based on the pseudo open circuit voltage and the determined correlation when the pseudo open circuit voltage in the discharge process is within a predetermined range. and has.

According to the above configuration, by taking hysteresis into consideration and implementing the OCV method in a predetermined voltage section, it is possible to accurately estimate the amount of electricity stored in the electricity storage element.

The computer program according to the embodiment provides a computer that estimates the amount of stored power of a power storage element that has hysteresis due to charge/discharge history in the correlation between the amount of stored power and the pseudo-open voltage. A correlation between voltages is determined, and when a pseudo open circuit voltage in a discharge process is within a predetermined range, a process of estimating the amount of stored electricity in a discharge process is executed based on the pseudo open circuit voltage and the determined correlation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.
The power storage element according to the present embodiment includes a positive electrode active material that has hysteresis due to charging and discharging history in the correlation between the amount of stored power and the pseudo open circuit voltage.

The SOC-OCV curve of the power storage element changes depending on the charging/discharging history. FIG. 1 is a graph showing changes in the SOC-OCV curve depending on charge/discharge history. In FIG. 1, the horizontal axis is SOC (%) and the vertical axis is OCV (V). Curve C shows the SOC-OCV curve during charging from 0% to 100% SOC. Curve D shows the SOC-OCV curve during discharge at SOC of 100% to 0%. Curve D30 shows the SOC-OCV curve during discharge at SOC of 30% to 0%.

As shown in FIG. 1, the SOC-OCV curve C during charging and the SOC-OCV curve D during discharging are different. In curve C and curve D, there is a difference of ΔSOC1 in SOC for the same OCV. When the discharge start SOC is different, the SOC-OCV curve is also different. In curve D and curve D30, there is a difference of ΔSOC2 in SOC for the same OCV. Here, the discharge start SOC refers to the SOC at the time when the electricity storage element is switched to discharging after being charged. That is, curve D30 shows the SOC-OCV curve when the discharge start SOC is 30%, and curve D shows the SOC-OCV curve when the discharge start SOC is 100%.

Depending on the charging/discharging history, the correlation between the rated capacity ratio r of the power storage element and the OCV (hereinafter referred to as an r-OCV curve) also changes. FIG. 2 is a graph showing changes in the rated capacity ratio r-OCV curve depending on the charging/discharging history. In FIG. 2, the horizontal axis is the rated capacity ratio r, and the vertical axis is the OCV (V). Curve C0 shows the r-OCV curve when charging from SOC 0 to 100%. Curve D10 shows the r-OCV curve during discharge at SOC of 100% to 0%. Each point indicates a measurement point when the discharge start SOC is 20%, 30%, 40%, 60%, 70%, and 90%, respectively. It has been found that when linear approximation is applied to these measurement points, OCV with respect to r exhibits good linearity in a predetermined voltage section. Here, the predetermined voltage section is preferably 3.220V to 3.295V. The lower limits are more preferably in the order of 3.230, 3.225, and 3.220. The upper limit is more preferably in the order of 3.280, 3.290, and 3.295.

FIG. 2 shows r-OCV curves corresponding to each discharge start SOC after linear approximation. D2, D3, D4, D6, D7, and D9 show r-OCV curves when the discharge start SOC is 20%, 30%, 40%, 60%, 70%, and 90%, respectively. In FIG. 2, the linear approximation obtained good fitting accuracy when the discharge start SOC was 20%, 30%, 40%, 60%, 70%, and 90%, respectively.

As described above, in a predetermined voltage space, there is an extremely strong linear proportionality between the rated capacity ratio r of the power storage element and the OCV. Therefore, if the r-OCV curve in the discharge process, that is, the r-OCV curve with hysteresis taken into account, can be determined, it becomes possible to accurately determine the amount of electricity stored in the electricity storage element using the OCV method.

In this embodiment, an r-OCV curve with hysteresis taken into account is determined by using the linear proportional relationship between the rated capacity ratio r and OCV in the above-mentioned predetermined voltage space.

FIG. 3 is an explanatory diagram for determining the r-OCV curve. The horizontal axis is the rated capacity ratio r, and the vertical axis is the OCV (V). When OCV obtained at two time points t0 and t1 in the discharge process are OCV _t0 and OCV _t1 , the OCV change amount ΔV and discharge amount Δr in the period from time t0 to t1 are calculated by the formula ( 2).

Here, I is the current, _r0 is the rated capacity, and the discharge direction is assumed to be positive.
As described above, the gradient ΔV/Δr of the straight line passing through the two measurement points in FIG. 3 is determined. Using the obtained gradient ΔV/Δr, the r-OCV curve in the discharge process can be determined by referring to a reference r-OCV curve obtained in advance.

The reference r-OCV curve will be explained below.
The reference r-OCV curve refers to a plurality of r-OCV curves obtained in advance through experiments for each discharge start SOC. For example, by charging a storage element to a predetermined SOC and discharging it at multiple points in time, and measuring the terminal voltage and current of the storage element at each point in the discharge process, the coordinates (OCV, r) of each measurement point can be determined. get. A linear approximation curve is obtained by linearly approximating each measurement point, and this linear approximation curve is defined as an r-OCV curve corresponding to a predetermined discharge start SOC.

In this embodiment, a plurality of r-OCV curves measured when the discharge start SOC is 20%, 30%, 40%, . . . , 100% are used as reference r-OCV curves. Data related to the reference r-OCV curve is stored in a table 63b of the memory 63 of the storage amount estimating device, which will be described later. For example, the slope and intercept of these r-OCV curves are stored in a table in memory in association with the discharge start SOC. Table 1 is an example of a reference r-OCV curve table.

Hereinafter, a method for determining an r-OCV curve in a discharge process based on a reference r-OCV curve will be described.
The gradient ΔV/Δr obtained as described above is compared with the gradient stored in the table. If the determined slope ΔV/Δr matches the slope stored in the table, the r-OCV curve can be created using the slope stored in the table and the corresponding intercept. If the obtained slope ΔV/Δr does not match the slope stored in the table, the r-OCV curve can be determined by interpolation or extrapolation calculation based on the reference r-OCV curve table. The determined r-OCV curve may be stored in a table. This makes it possible to use the r-OCV curve until charging/discharging is switched.

For example, if the obtained gradient ΔV/Δr is between two adjacent gradients in the table, the r-OCV curve is determined by interpolation calculation, but the obtained gradient ΔV/Δr is between the minimum SOC in the table. If it is larger than the corresponding slope, the r-OCV curve is determined by extrapolation calculation. In this embodiment, reference r-OCV curves are stored discretely in the table, but r-OCV curves corresponding to all discharge start SOCs may be stored continuously instead of discretely.

Using the determined r-OCV curve, it is possible to estimate the current remaining discharge capacity based on the current OCV, and further to estimate the SOC from the remaining discharge capacity. The current OCV is calculated from the acquired voltage and current. Calculation of OCV is obtained by estimating the voltage when the current is zero using a regression line from a plurality of voltage and current data. Further, when the current is small like a dark current, or when the pause time is relatively long even when the current is zero and the voltage is stabilizing, the acquired voltage can be read as OCV.
In the determined r-OCV curve, read r from the OCV. The rated capacity ratio r is shown by equation (3). The rated capacity ratio r is shown by equation (3).

ｆ_ｒ-OCVは、参照ｒ－ＯＣＶ曲線、又は勾配及び切片を内挿計算することによって得たｒ－ＯＣＶ曲線であり、ＯＣＶを引数とする定格容量比の関数である。

f _r-OCV is a reference r-OCV curve or an r-OCV curve obtained by interpolating the slope and intercept, and is a function of the rated capacity ratio using OCV as an argument.

By the above method, when a material with hysteresis is used for the energy storage element, the current r- OCV curves can be estimated. Thereby, the amount of stored electricity such as the remaining discharge capacity and SOC of the electricity storage element can be detected with high accuracy.

The amount of electricity stored in the electricity storage element mounted in the electricity storage system can be monitored with high precision by taking into account OCV changes due to hysteresis.

Furthermore, even for energy storage elements with hysteresis, the r-OCV curve during the discharge process can be estimated, so if the OCV can be measured during any period during the discharge process, the remaining discharge capacity and SOC can be estimated. I can do it.

Furthermore, since the amount of stored electricity can be estimated with high accuracy, it is possible to reduce the extra margin area included in the SOC range of the electricity storage element, and it is possible to improve the substantially usable volumetric energy density. For example, when there is an SOC estimation error, the usage range of the SOC is often limited with some margin in consideration of deterioration of the power storage element. According to the estimation method of the present invention, the usage range of the SOC can be set as wide as possible, and unnecessary margin areas can be reduced.

(Embodiment 1)
Embodiment 1 will be described below as an example of a power storage module mounted on a vehicle.
FIG. 4 shows an example of a power storage module. The power storage module 50 includes a plurality of power storage elements 200, a monitoring device 100, and a housing case 300 that accommodates them. The power storage module 50 may be used as a power source for an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV).
The power storage element 200 is not limited to a square cell, but may be a cylindrical cell or a pouch cell.

Monitoring device 100 may be a circuit board disposed facing a plurality of power storage elements 200. Monitoring device 100 monitors the state of power storage element 200. The monitoring device 100 may be a storage amount estimating device. Alternatively, a computer or a server connected by wire or wirelessly to the monitoring device 100 may execute the method for estimating the amount of stored electricity based on the information output by the monitoring device 100.

FIG. 5 shows another example of the power storage module. The power storage module 1 may be a 12-volt power source or a 48-volt power source that is suitably mounted on an engine vehicle. 5 is a perspective view of the power storage module 1 for 12V power supply, FIG. 6 is an exploded perspective view of the power storage module 1, and FIG. 7 is a block diagram of the power storage module 1.

The power storage module 1 has a case 2 in the shape of a rectangular parallelepiped. A plurality of lithium ion secondary batteries (hereinafter referred to as batteries) 3, a plurality of bus bars 4, a BMU (Battery Management Unit) 6, and a current sensor 7 are housed in the case 2.

The battery 3 includes a rectangular parallelepiped case 31 and a pair of terminals 32 and 32 provided on one side of the case 31 and having different polarities. The case 31 houses an electrode body 33 in which a positive electrode plate, a separator, and a negative electrode plate are laminated.

The positive electrode plate of the electrode body 33 includes an active material that has hysteresis in the amount of stored electricity-voltage value characteristic depending on the transition of charging and discharging. Examples of the positive electrode active material include positive electrode active materials having an olivine structure such as LiFePO ₄ , Li(Mn _1-x Fe _x )PO ₄ , and Li ₂ MnSiO ₄ .

Case 2 is made of synthetic resin. The case 2 includes a case body 21, a lid part 22 that closes the opening of the case body 21, a BMU accommodating part 23 provided on the outer surface of the lid part 22, a cover 24 that covers the BMU accommodating part 23, and an inner lid. 25 and a partition plate 26. The inner lid 25 and the partition plate 26 may not be provided. A battery 3 is inserted between each partition plate 26 of the case body 21.

A plurality of metal bus bars 4 are placed on the inner lid 25. An inner lid 25 is placed on the terminal surface where the terminals 32 of the batteries 3 are provided, and the adjacent terminals 32 of the adjacent batteries 3 are connected by a bus bar 4, so that the batteries 3 are connected in series.

The BMU accommodating portion 23 has a box shape, and has a protrusion 23a that protrudes outward in a square shape at the center of one long side. A pair of external terminals 5, 5 made of metal such as lead alloy and having different polarities are provided on both sides of the protrusion 23a of the lid 22. The BMU 6 includes an information processing section 60, a voltage measurement section 8, and a current measurement section 9 mounted on a board. By accommodating the BMU 6 in the BMU accommodating portion 23 and covering the BMU accommodating portion 23 with the cover 24, the battery 3 and the BMU 6 are connected.

As shown in FIG. 7, the information processing section 60 includes a CPU 62 and a memory 63.
The memory 63 stores a storage amount estimation program 63a according to the present embodiment and a table 63b storing data related to the reference r-OCV curve. The stored power amount estimation program 63a is provided in a state stored in a computer-readable recording medium 70 such as a CD-ROM, DVD-ROM, or USB memory, and is stored in the memory 63 by being installed in the BMU 6. Alternatively, the stored power amount estimation program 63a may be acquired from an external computer (not shown) connected to a communication network and stored in the memory 63.

The CPU 62 executes a stored power amount estimation process, which will be described later, according to the stored power amount estimation program 63a read from the memory 63.

The voltage measurement unit 8 is connected to both ends of the batteries 3 via voltage detection lines, and measures the voltage of each battery 3 at predetermined time intervals.
The current measurement unit 9 measures the current flowing through the battery 3 via the current sensor 7 at predetermined time intervals.

External terminals 5, 5 of the power storage module 1 are connected to a load 11 such as a starter motor for starting an engine and electrical equipment. An ECU (Electronic Control Unit) 10 is connected to a BMU 6 and a load 11.

The method for estimating the amount of stored electricity according to this embodiment will be described below.
FIG. 8 is a flowchart illustrating the procedure of the power storage amount estimation process by the CPU 62. The CPU 62 repeats the processing from S1 at predetermined or appropriate time intervals.

The CPU 62 acquires the voltage measured by the voltage measuring section 8 and the current measured by the current measuring section 9 at two points in time (S1).
The CPU 62 calculates the OCV change amount ΔV and the discharge amount Δr between the two time points based on the obtained voltage and current (S2), and calculates the slope ΔV/Δr of the r-OCV curve (S3).

The CPU 62 compares the calculated slope ΔV/Δr with the slope in the table 63b, and if they match (S4: YES), refers to the table 63b and creates an r-OCV curve corresponding to the calculated slope. (S5).

The CPU 62 estimates the remaining discharge capacity and calculates the SOC based on the specified r-OCV curve (S6), and ends the process.

If they do not match (S4: NO), the CPU 62 reads slope data close to the calculated slope value from the table 63b and uses these data to perform interpolation calculation to estimate the discharge start SOC. (S7).

The CPU 62 determines the slope and intercept from the reference table based on the estimated SOC, estimates the r-OCV curve determined from them (S8), stores it in the table 63b (S9), and shifts the process to S6. let

Below, the accuracy of estimating the amount of stored electricity using the estimation method of the present application will be verified.
FIG. 9 is a charge-discharge curve obtained by the SOC fluctuation test. FIG. 10 is a diagram showing the total SOC variation amount by the SOC variation test. In FIG. 9, the horizontal axis is SOC (%) and the vertical axis is voltage (V). In FIG. 10, the horizontal axis is the total SOC fluctuation amount (%), and the vertical axis is the voltage (V). When the current was 0.1 CA and 1 CA, charge adjustment and discharge adjustment were performed to vary the SOC so that the total SOC fluctuation amount was equal in both cases. After each adjustment, the terminal voltage was obtained as OCV after a predetermined pause time.

In this embodiment, the SOC was varied irregularly within the range of SOC 0 to 100%, and the OCV was obtained in the 3.22 to 3.28 V range. Further, the predetermined rest time was set to 2 hours after the end of energization.

Table 2 shows the OCV (V1, V2) of the two most recent measurement points and the discharge amount Δr between the two points in each discharge process acquired in the 3.22 to 3.28V interval in the SOC fluctuation test.

In this embodiment, the remaining discharge capacity Q is estimated for P3 in Table 2. FIG. 11 is an explanatory diagram for determining the r-OCV curve. In FIG. 11, the horizontal axis is the rated capacity ratio r, the vertical axis is the OCV (V), and two measurement points corresponding to P3 and a part of the reference r-OCV curve are shown. The slope of the straight line passing through the two measurement points is determined as follows.

ΔV/Δr=(3.2673-3.2306)/0.0819≒0.448(V)

Referring to the reference r-OCV curve table in Table 1, the calculated slope is between 0.472 and 0.411 in Table 1, so the discharge start SOC (rated capacity ratio) corresponding to P3 is 30 % to 40% (r=0.3 to 0.4). As described above, by performing interpolation calculations using the data in Table 1, the slope and intercept of the r-OCV curve were determined, and the discharge start SOC was 33.9% and the remaining discharge capacity Q was 3.34Ah. estimated that. Compared to the actually measured residual discharge capacity Q of 3.31 Ah, the SOC conversion error is only 0.3%, and the estimation accuracy is high.

Table 3 shows the slope, SOC, and intercept calculated for P1 to P7 in Table 2.

Table 4 shows the estimated remaining discharge capacity Q based on Tables 2 and 3, the measured remaining discharge capacity Q, and the error calculated based on these.

In Tables 3 and 4, the slopes corresponding to P6 and P7 are larger than the slopes corresponding to the rated capacity ratio of 0.2 in Table 1, so the estimated SOC and estimated Q were obtained by extrapolation calculation. The SOC error is an error with respect to the actual measured value of SOC determined by the conventional OCV method (charge/discharge average OCV). Based on Tables 3 and 4, the estimation method according to the present application can estimate the remaining discharge capacity with higher accuracy than the conventional OCV method that does not take OCV hysteresis into consideration.

The present invention is not limited to the contents of the embodiments described above, and various changes can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included within the technical scope of the present invention.

The power storage amount estimating device according to the present invention is not limited to being applied to vehicle-mounted lithium ion secondary batteries, but can also be applied to other power storage modules such as regenerative power storage devices for railways and solar power generation systems. In a power storage module through which a minute current flows, the voltage between the positive and negative terminals of the power storage element or the voltage between the positive and negative terminals of the power storage module can be regarded as OCV.

The power storage element is not limited to a lithium ion secondary battery, but may be another secondary battery or electrochemical cell having hysteresis characteristics.

The present invention is not limited to the case where the monitoring device 100 or the BMU 6 is a storage amount estimating device. A CMU (Cell Monitoring Unit) may be a storage amount estimating device. The power storage amount estimating device may be part of a power storage module in which the monitoring device 100 and the like are incorporated. The power storage amount estimating device may be configured separately from the power storage element and the power storage module, and may be connected to the power storage module including the power storage element whose heat storage amount is to be estimated at the time of estimating the heat storage amount. The heat storage amount estimating device may remotely monitor the power storage element or the power storage module.

1, 50 Energy storage module 2 Case 200 Energy storage element 21 Case body 22 Lid 23 BMU accommodating part 24 Cover 25 Inner lid 26 Partition plate 3 Battery (energy storage element)
31 Case 32 Terminal 33 Electrode body 4 Bus bar 5 External terminal 6 BMU (Stored electricity amount estimating device)
60 Information processing unit 62 CPU (determination unit, estimation unit)
63 memory 63a storage amount estimation program 63b table 7 current sensor 8 voltage measurement unit 9 current measurement unit 10 ECU
70 Recording medium 100 Monitoring device (storage amount estimation device)
300 storage case

Claims (5)

A storage amount estimating device for a power storage element having hysteresis due to charging and discharging history in the correlation between the storage amount and pseudo open circuit voltage,
Calculate the ratio between the amount of change in the pseudo open circuit voltage and the amount of discharge between at least two points in the discharge process, and calculate the ratio between the calculated ratio and the amount of stored electricity and pseudo open circuit voltage stored in advance for each amount of stored electricity at the start of discharge. a determining unit that determines the correlation between the amount of stored electricity and the pseudo open circuit voltage corresponding to the amount of stored electricity at the start of discharge based on the correlation;
An estimation unit for estimating the amount of stored electricity in the discharging process based on the pseudo open circuit voltage and the determined correlation when the pseudo open circuit voltage in the discharging process is within a predetermined range. The storage amount estimating device according to claim 1 , wherein the correlation is a characteristic curve showing a linear proportional relationship between the rated capacity ratio of the storage element and the pseudo open circuit voltage. The pre-stored correlation between the amount of stored electricity and the pseudo open circuit voltage includes the slope of the characteristic curve,
The determining unit determines the correlation corresponding to the amount of electricity stored at the time of starting the discharge by comparing the calculated ratio with a slope of the characteristic curve stored in advance. Electricity storage amount estimation device. A method for estimating the amount of stored electricity of a power storage element having hysteresis due to charging and discharging history in the correlation between the amount of stored electricity and the pseudo open circuit voltage, the method comprising:
Calculate the ratio between the amount of change in the pseudo open circuit voltage and the amount of discharge between at least two points in the discharge process, and calculate the ratio between the calculated ratio and the amount of stored electricity and pseudo open circuit voltage stored in advance for each amount of stored electricity at the start of discharge. determining the correlation between the amount of stored electricity and the pseudo open circuit voltage corresponding to the amount of stored electricity at the start of discharge, based on the correlation;
A method for estimating the amount of stored electricity, comprising: when the pseudo open circuit voltage during the discharging process is within a predetermined range, the amount of stored electricity in the discharging process is estimated based on the pseudo open circuit voltage and the determined correlation. A computer that estimates the amount of electricity stored in an electricity storage element that has hysteresis due to charge/discharge history in the correlation between the amount of electricity stored and the pseudo open circuit voltage,
Calculate the ratio between the amount of change in the pseudo open circuit voltage and the amount of discharge between at least two points in the discharge process, and calculate the ratio between the calculated ratio and the amount of stored electricity and pseudo open circuit voltage stored in advance for each amount of stored electricity at the start of discharge. Based on the correlation, determine the correlation between the amount of stored electricity and the pseudo open circuit voltage corresponding to the amount of stored electricity at the start of discharge,
A computer program that executes a process of estimating an amount of electricity stored in a discharge process based on the pseudo open circuit voltage and the determined correlation when the pseudo open circuit voltage in the discharge process is within a predetermined range.

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