JP2021071319A - Soc estimating device, power storage device, and soc estimating method - Google Patents

Abstract

To provide an SOC estimating device for estimating a range in which the SOC of a power storage element is included, a power storage device, and an SOC estimating method.SOLUTION: An SOC estimating device for estimating the SOC of a power storage element comprises: a first storage unit for storing a first resistance value that represents resistance the power storage element when the SOC of the power storage element is included in a prescribed first range; a first acquisition unit for acquiring a current and voltage when the power storage element discharges electricity; a second resistance value calculation unit for calculating, on the basis of the acquired current and voltage, a second resistance value that represents resistance when the power storage element discharges electricity; a resistance ratio calculation unit for calculating a resistance ratio that represents the calculated second resistance value divided by the first resistance value; and a first determination unit for determining, in accordance with the calculated resistance ratio, in which range, a first range or a second range in which an SOC lower than the first range is included, the SOC of the power storage element is included.SELECTED DRAWING: Figure 2

Description

The present invention relates to an SOC estimation device, a power storage device, and an SOC estimation method for estimating the SOC of a power storage element.

Power storage elements such as lithium ion secondary batteries are used in various fields such as power storage devices for vehicles. When using the power storage device, it is necessary to manage the charge rate (SOC) of the power storage element included in the power storage device. SOC represents the amount of electricity charged in the power storage element as a ratio to the full charge capacity of the power storage element. As a method of estimating the SOC of the power storage element, there is a method of estimating the SOC based on the correlation (SOC-OCV curve) in which the OCV (open circuit voltage) and the SOC have a one-to-one correspondence. This SOC estimation method is generally used in a state where the power storage element is not charged / discharged (a state in which the overvoltage is eliminated, for example, a state in which the vehicle is parked).

Some power storage elements include a plateau region in which the OCV becomes substantially constant with respect to a change in SOC in the SOC-OCV curve. For example, some lithium ion secondary batteries have a plateau region in which the SOC is in the range of 50% to 80%. When the SOC is included in the plateau region, the OCV is almost constant with respect to the change in the SOC. In that state, although the output voltage of the power storage element is stable, it is difficult to accurately estimate the SOC according to the OCV value. Patent Document 1 describes an example of a technique for estimating the SOC of a power storage element.

Japanese Unexamined Patent Publication No. 2016-109455

If the power storage element can be used even when the SOC is lower than the plateau region, the usage efficiency of the power storage element is improved. However, if the SOC becomes too low, an over-discharged state will occur.

An object of the present invention is to provide an SOC estimation device, a power storage device, and an SOC estimation method for estimating the SOC of a power storage element including a plateau region in the SOC-OCV curve during use of the power storage element.

The SOC estimation device according to one aspect of the present invention estimates the SOC (State of Charge) of the power storage element. The SOC estimation device includes a first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range, and a first storage unit that stores the first resistance value when the power storage element discharges. The first acquisition unit for acquiring the current and voltage and the second resistance value calculation unit for calculating the second resistance value representing the resistance when the power storage element discharges based on the acquired current and voltage were calculated. It includes a resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the second resistance value by the first resistance value, and an SOC that is lower than the first range or the first range depending on the calculated resistance ratio. It is provided with a first determination unit for determining which range of the second range is included in the SOC of the power storage element. The first determination unit determines the storage element in any of the first range, the second range, and the third range including the SOC lower than the second range, depending on the calculated resistance ratio. It may be determined whether SOC is included.

The power storage device according to one aspect of the present invention includes a power storage element. The power storage device includes a first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range, and a current when the power storage element discharges. And a measuring unit for measuring voltage, a second resistance value calculating unit for calculating a second resistance value representing the resistance when the power storage element discharges based on the acquired current and voltage, and the calculated second resistance value. A resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the resistance value by the first resistance value, and a second range including the first range or an SOC lower than the first range depending on the calculated resistance ratio. A first determination unit for determining which range of the range includes the SOC of the power storage element is provided.

The SOC estimation method according to one aspect of the present invention measures the current and voltage when the power storage element discharges, and represents the resistance when the power storage element discharges based on the acquired current and voltage. The two resistance values are calculated, and the resistance ratio obtained by dividing the calculated second resistance value by the first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in the predetermined first range is calculated. Then, according to the calculated resistance ratio, it is determined whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included. In the determination, the SOC of the power storage element is included in any of the first range, the second range, and the third range including the SOC lower than the second range, depending on the calculated resistance ratio. It may be determined whether or not it is.

With the above configuration, it is estimated whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included. Since the SOC can be grasped during the use of the power storage element whose SOC-OCV curve includes the plateau region, the range of SOCs in which the power storage element can be used is expanded.

It is a schematic diagram which shows the example of the power storage module and the SOC estimation device. It is a block diagram which shows the example of the functional structure of the power storage module and the SOC estimation device which concerns on Embodiment 1. FIG. It is a graph which shows the example of the SOC-OCV curve of a storage cell. It is a graph which shows the example of the measurement result of the current-voltage characteristic when a storage cell discharges for 10 seconds. It is a graph which shows SOC and DCR when a storage cell discharges for 10 seconds. It is a graph which shows the resistance ratio which divided the DCR of a storage cell by DCR when SOC is included in the 1st range. It is a flowchart which shows the procedure of the process which estimates the SOC of the storage cell performed by the SOC estimation apparatus which concerns on Embodiment 1. FIG. It is a graph which shows the example of the measurement result of the current-voltage characteristic when a storage cell in EOL discharges for 10 seconds. It is a graph which shows the resistance ratio which divided the DCR at the time of discharge of a storage cell in EOL by DCR at the time of discharge when SOC is included in the 1st range. It is a block diagram which shows the example of the functional structure of the power storage module and SOC estimation apparatus 3 which concerns on Embodiment 2. It is a block diagram which shows the example of the functional structure of the power storage module which concerns on Embodiment 3.

The SOC estimation device that estimates the SOC of the power storage element includes a first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range, and the power storage unit. A first acquisition unit that acquires the current and voltage when the element discharges, and a second resistance that calculates a second resistance value that represents the resistance when the power storage element discharges based on the acquired current and voltage. The value calculation unit, the resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the calculated second resistance value by the first resistance value, and the first range or the first range according to the calculated resistance ratio. A first determination unit for determining which range of the second range in which the SOC lower than the range is included includes the SOC of the power storage element is provided.

The SOC estimation device calculates the resistance ratio obtained by dividing the second resistance value representing the resistance of the power storage element at the time of discharge by the first resistance value representing the resistance when the SOC is included in the predetermined first range. Further, the SOC estimation device determines whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included, depending on the resistance ratio. By doing so, the SOC is estimated. The SOC estimator determines in which of the first range, the second range, and the third range, which includes the SOC lower than the second range, the SOC of the power storage element is included, depending on the resistance ratio. You may. Since the resistance ratio decreases almost monotonously as the SOC increases, it is possible to determine in which range the SOC is included according to the resistance ratio. In the state where the SOC is included in the second range, the voltage of the power storage element becomes relatively low, but if the use is restricted such as prohibiting the use of power by a load that requires high power, the power storage element can be used. Can be used. Therefore, the range of SOCs in which the power storage element can be used is expanded as compared with the conventional technique in which the power storage element is used only when the SOC is included in the first range.

In the SOC estimation device, the SOC of the power storage element is included in the first range based on the OCV acquisition unit that acquires the OCV of the power storage element and the acquired OCV before the power storage element is charged or discharged. A second determination unit for determining whether or not the power storage element is used, and a second determination unit for acquiring the current and voltage when the power storage element first discharges when the SOC of the power storage element is included in the first range. An acquisition unit and a first resistance value calculation unit that calculates the first resistance value based on the current and voltage acquired by the second acquisition unit may be further provided. Before the power storage element is used, it is confirmed that SOC is included in the first range based on OCV, the current and voltage at the time of discharge are acquired, and the resistance of the power storage element when SOC is included in the first range is determined. The first resistance value to be represented is calculated. The first resistance value of the power storage element for which the SOC is estimated is calculated.

In the SOC estimation device, when the resistance ratio is less than a predetermined first threshold value, the first determination unit determines that the SOC of the power storage element is included in the first range, and the resistance ratio is determined to be within the first range. When it is equal to or more than the first threshold value and less than a predetermined second threshold value exceeding the first threshold value, it is determined that the SOC of the power storage element is included in the second range, and the resistance ratio is When it is equal to or higher than the second threshold value, it may be determined that the SOC of the power storage element is included in the third range lower than the second range. By comparing the resistance ratio with the first threshold value and the second threshold value, the range in which the SOC of the power storage element is included can be easily estimated.

In the SOC estimation device, the first threshold value is the resistance of the power storage element when the SOC of the power storage element is the lower limit of the first range, and the resistance when the SOC of the power storage element is included in the first range. The second threshold value is a value that exceeds the value divided by, and the second threshold value is the resistance of the power storage element when the SOC of the power storage element is the upper limit of the third range, and the SOC of the power storage element is the first range. It may be a value equal to or more than the value divided by the resistance of the power storage element at the lower limit of. When the first threshold value and the second threshold value are such values, if the resistance ratio is less than the first threshold value, the SOC of the power storage element is likely to be included in the first range. Even if the SOC is included in the second range, the SOC is close to the first range and the voltage at the time of discharging the power storage element is relatively high, so that it can be roughly estimated that the SOC is included in the first range. When the resistance ratio is equal to or higher than the second threshold value, the SOC of the power storage element is likely to be included in the third range. Even if the SOC is included in the second range, the SOC is close to the third range and the voltage at the time of discharging the power storage element is relatively low, so that it can be roughly estimated that the SOC is included in the third range.

The SOC estimation device may further include a second storage unit that stores the first threshold value and the second threshold value that differ depending on the SOH (State of Health) for each of the plurality of SOHs, and the first determination unit. May use the first threshold value and the second threshold value stored in the first storage unit for the SOH of the power storage element to determine in which range the SOC of the power storage element is included. Since the resistance ratio changes according to the SOH of the power storage element, the SOC of the power storage element can be estimated accurately by performing the determination using the first threshold value and the second threshold value according to the SOH.

In the SOC estimation device, the second resistance value calculation unit may calculate the second resistance value from the currents and voltages at a plurality of time points when the power storage element is discharging. By statistically calculating the second resistance value from the current and voltage at a plurality of time points, the second resistance value is calculated with high accuracy.

The power storage device including the power storage element has a first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range, and the power storage element discharges the electric current. A measurement unit that measures the current and voltage at the time of operation, and a second resistance value calculation unit that calculates a second resistance value that represents the resistance when the power storage element discharges based on the acquired current and voltage. The resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the second resistance value by the first resistance value, and the SOC that is lower than the first range or the first range depending on the calculated resistance ratio. A first determination unit for determining which range of the included second range includes the SOC of the power storage element is provided. The power storage device determines whether the SOC of the power storage element is included in the first range or the second range according to the resistance ratio obtained by dividing the second resistance value by the first resistance value. Estimate the SOC. The power storage device determines, depending on the resistance ratio, which of the first range, the second range, and the third range including the SOC lower than the second range contains the SOC of the power storage element. May be good. In the state where the SOC is included in the second range, the voltage of the power storage element becomes relatively low, but the power storage element can be used if the use is restricted. Therefore, the range of SOCs in which the power storage element can be used is expanded as compared with the conventional technique in which the power storage element is used only when the SOC is included in the first range.

In the method of estimating the SOC of the power storage element, the current and voltage when the power storage element discharges are measured, and the second resistance representing the resistance when the power storage element discharges based on the acquired current and voltage. The value is calculated, and the resistance ratio obtained by dividing the calculated second resistance value by the first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in the predetermined first range is calculated. According to the calculated resistance ratio, it is determined whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included. The SOC is estimated by determining whether the SOC of the power storage element is included in the first range or the second range according to the resistance ratio obtained by dividing the second resistance value by the first resistance value. To. In the SOC estimation method, it is determined in which of the first range, the second range, and the third range, which includes the SOC lower than the second range, the SOC of the power storage element is included, depending on the resistance ratio. You may. In the state where the SOC is included in the second range, the voltage of the power storage element becomes relatively low, but the power storage element can be used if the use is restricted. Therefore, the range of SOCs in which the power storage element can be used is expanded as compared with the conventional technique in which the power storage element is used only when the SOC is included in the first range.

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments thereof.
<Embodiment 1>
FIG. 1 is a schematic diagram showing an example of a power storage module 10 and an SOC estimation device 3. The power storage module 10 and the SOC estimation device 3 execute the SOC estimation method. The power storage module 10 includes a plurality of power storage cells 11 connected in series and / or in parallel. The power storage cell 11 corresponds to a power storage element. The power storage cell 11 is a power storage element for a secondary battery such as a lithium ion battery. The storage cell 11 has a rectangular parallelepiped shape. The storage cell 11 includes a rectangular parallelepiped case, positive terminals, and negative terminals. Inside the case, a positive electrode, a negative electrode, a separator and an electrolyte (electrolyte solution) are housed. For example, the positive electrode is made of a material containing lithium iron phosphate, and the negative electrode is made of graphite. The separator is interposed between the positive electrode and the negative electrode. For example, the positive electrode, the negative electrode, and the separator are in the form of a sheet, and are housed in a case as an electrode body in which they are stacked and wound. The electrode body is not limited to the wound type, and may be a laminated type. The positive electrode is connected to the positive terminal and the negative electrode is connected to the negative terminal. The shape of the power storage cell 11 may be a shape other than a rectangular parallelepiped, and may be a pouch shape or a cylindrical shape.

The power storage module 10 includes a rectangular parallelepiped housing 12 which is an example of a holding member. The plurality of storage cells 11 are arranged side by side and held (stored) in the housing 12. Alternatively, the holding member may be formed by a pair of end plates and a plurality of fastening bars connecting the end plates. The plurality of storage cells 11 are connected in series and / or in parallel by a bus bar (not shown). Although FIG. 1 shows an example in which the power storage module 10 includes four power storage cells 11, the power storage module 10 may include a number of other power storage cells 11.

The power storage module 10 includes a CMU (Cell Monitoring Unit) 2. The CMU2 has a configuration in which various parts are arranged on a substrate. In FIG. 1, CMU2 is shown in a plate shape. The CMU 2 measures the current flowing through the power storage cell 11 included in the power storage module 10 and the voltage generated in the power storage cell 11. The SOC estimation device 3 is provided outside the power storage module 10. The SOC estimation device 3 is connected to the CMU 2. The power storage module 10 supplies electric power to the load.

Further, the SOC estimation device 3 is connected to the load circuit 4. The load circuit 4 is a circuit including a load to which electric power is supplied from the power storage module 10. The load circuit 4 may include a plurality of loads. For example, the power storage module 10 is mounted on a vehicle, and the load circuit 4 includes, as a load, a motor that assists the acceleration of the vehicle and electrical components such as lights. The load circuit 4 may include a control unit that controls the operation of various loads, or may include an alternator.

FIG. 2 is a block diagram showing an example of the functional configuration of the power storage module 10 and the SOC estimation device 3 according to the first embodiment. In the power storage module 10, for example, a plurality of power storage cells 11 are connected in series. The CMU 2 includes a calculation unit 21, a memory 22, a storage unit 23, a current measurement unit 24, a voltage measurement unit 25, and a communication unit 26. The calculation unit 21 is, for example, a CPU (Central Processing Unit). The memory 22 stores information necessary for the calculation in the calculation unit 21. The storage unit 23 is non-volatile and stores programs and data. The calculation unit 21 executes the process according to the program stored in the storage unit 23. For example, the storage unit 23 is a non-volatile semiconductor memory. The current measuring unit 24 measures the current flowing through the plurality of storage cells 11. For example, the current measuring unit 24 includes a resistor connected in series to a plurality of storage cells 11 connected in series, and a voltmeter for measuring the voltage across the resistor. The voltage measuring unit 25 measures the voltage between both ends of each storage cell 11. For example, the voltage measuring unit 25 includes a voltmeter connected to a positive terminal and a negative terminal of each storage cell 11. The communication unit 26 transmits / receives information to / from the outside of the power storage module 10. The communication unit 26 is connected to the SOC estimation device 3 and transmits information to the SOC estimation device 3. The calculation unit 21 performs a process of controlling each unit of the CMU2.

The SOC estimation device 3 is configured by using a computer. For example, when the power storage module 10 is included in the power storage device mounted on the vehicle, the SOC estimation device 3 may be configured by an ECU (Electronic Control Unit). The SOC estimation device 3 includes a calculation unit 31, a memory 32, a storage unit 33, and a communication unit 34. The arithmetic unit 31 is configured by using, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a multi-core CPU. The calculation unit 31 may be configured by using a quantum computer. The memory 32 stores temporary data generated by the calculation. The memory 32 is, for example, a RAM (Random Access Memory). The storage unit 33 is, for example, a hard disk or a non-volatile semiconductor memory. The storage unit 33 stores the computer program 331, and the calculation unit 31 executes necessary processing according to the computer program 331 stored in the storage unit 33. The communication unit 34 is connected to the power storage module 10 and receives the information transmitted from the power storage module 10. A load circuit 4 is connected to the communication unit 34. The calculation unit 31 transmits a control signal for controlling the load circuit 4 from the communication unit 34 to the load circuit 4.

FIG. 3 is a graph showing an example of the SOC-OCV curve of the storage cell 11. The horizontal axis in the figure shows SOC (State of Charge), and the vertical axis shows OCV (Open Circuit Voltage). The range of 50% to 80% SOC is a plateau region where OCV becomes substantially constant with respect to changes in SOC. The range of SOC included in the plateau area is defined as the first range. It is possible to measure OCV and determine if SOC is included in the first range based on the SOC-OCV curve. However, it is difficult to determine which value the SOC is in the first range. When the SOC is included in the first range, the voltage at the time of discharging the storage cell 11 is stable. In the prior art, the storage cell 11 has been used with the SOC included in the first range.

The range of SOC of 20% to 50% is defined as the second range. The second range includes SOCs lower than the first range. In the state where the SOC is included in the second range, the voltage at the time of discharging the storage cell 11 is lower than in the state where the SOC is included in the first range, and the power that can be supplied is lowered. However, depending on the load, the power storage cell 11 can supply sufficient power to the load even when the SOC is included in the second range. The range of SOC of 0% to 20% is defined as the third range. The third range includes SOCs lower than the second range. In the state where the SOC is included in the third range, the voltage at the time of discharging the storage cell 11 becomes even lower, and the storage cell 11 cannot supply sufficient power to the load. When the SOC is included in the third range, the storage cell 11 needs to be charged.

When the OCV is obtained, the SOC according to the OCV can be estimated based on the SOC-OCV curve. However, when the SOC is included in the first range, the OCV is almost constant. Therefore, although it becomes clear that the SOC is included in the first range according to the OCV, the SOC is within the first range. The exact value is unknown. The storage unit 33 stores OCV data representing the SOC-OCV curve. The OCV data may be a graph as shown in FIG. 3, a pickup table, or a function that approximates the relationship between SOC and OCV.

The SOC estimation device 3 performs a process of estimating the SOC by determining whether the SOC of the storage cell 11 is included in the first range, the second range, or the third range. The discharge resistance of the storage cell 11 is used to estimate the SOC.

FIG. 4 is a graph showing an example of the measurement result of the current-voltage characteristic when the storage cell 11 is discharged for 10 seconds. The horizontal axis in the figure indicates the current, and the value increases to the right. The vertical axis in the figure indicates the voltage, and the value increases upward. With the SOC of the storage cell 11 set to a specific value, charge with a constant current for 10 seconds, measure the voltage, discharge with a current of 1C to return the SOC value, and return the SOC value with a constant current for 10 seconds. Was discharged, the voltage was measured, and an experiment was conducted in which the value of SOC was returned by charging with a current of 1C. In the experiment, charging / discharging and voltage measurement were repeated while changing the current value of the constant current. FIG. 4 shows a part of the experimental results and shows the current-voltage characteristics at the time of discharge. The right end of the horizontal axis of FIG. 4 indicates zero current, and the value of the current shown in the figure is negative.

FIG. 4 shows the current-voltage characteristics acquired in the state where the SOC of the storage cell 11 is 20%, 30%, 40%, 50%, 60%, 70% and 80%, respectively. It is indicated by a black square, a black triangle, a black circle, a white rhombus, a white square, and a white circle, respectively. The slope of the current-voltage characteristic corresponds to the DCR (Direct Current Resistance) inside the storage cell 11. DCR is the internal resistance of the storage cell 11. The DCR can be calculated from the current-voltage characteristics. As shown in FIG. 4, the DCR of the storage cell 11 at the time of discharge differs depending on the SOC.

FIG. 5 is a graph showing SOC and DCR when the power storage cell 11 is discharged for 10 seconds. The DCR when the power storage cell 11 is discharged for 10 seconds in a state where the SOC of the power storage cell 11 is a value of 20% to 80%, respectively, is shown. The horizontal axis in the figure indicates SOC. The vertical axis in the figure indicates DCR, and the value increases upward. The DCR shown in FIG. 5 is a value statistically calculated from the values of the current and the voltage included in the current-voltage characteristic shown in FIG. The DCR at the time of discharge is high when the SOC is low and low when the SOC is high. That is, the DCR at the time of discharge decreases monotonically as the SOC increases.

FIG. 6 is a graph showing the resistance ratio obtained by dividing the DCR of the storage cell 11 by the DCR when the SOC is included in the first range. The horizontal axis in the figure shows the SOC, and the horizontal axis shows the resistivity ratio obtained by dividing the DCR in the state where the SOC is each value by the DCR when the SOC is included in the first range. FIG. 6 shows the resistivity ratio obtained by dividing the DCR in the state where the SOC is each value by the DCR in the state where the SOC is 50%, 60%, 70% and 80%, respectively. 50%, 60%, 70% and 80% are SOC values included in the first range. FIG. 6 shows the resistivity obtained by dividing the DCR at each SOC by the DCR at 50%, 60%, 70% and 80% SOC, respectively, as circles, triangles, diamonds and squares. There is. The resistivity shown in FIG. 6 is a value calculated from the DCR shown in FIG. The resistivity decreases monotonically as the SOC increases.

Since the DCR at the time of discharge decreases monotonically as the SOC increases, the resistance ratio divided by the DCR at 50% SOC is smaller than the resistance ratio divided by the DCR at other SOCs. In FIG. 6, a straight line having a resistivity of 2.2 is shown by a broken line. In the example shown in FIG. 6, 2.2 is a value equal to or greater than the resistance ratio obtained by dividing the DCR at 20% SOC by the DCR at 50% SOC. 20% is the upper limit of the third range and 50% is the lower limit of the first range. The resistivity ratio obtained by dividing the DCR at which the SOC is 20% or less by the DCR when the SOC is included in the first range is 2.2 or more. Therefore, if the resistance ratio obtained by dividing the DCR of the storage cell 11 whose SOC is unknown by the DCR when the SOC is included in the first range is 2.2 or more, the SOC is likely to be included in the third range. ..

Even if the resistance ratio is 2.2 or more, the resistance ratio obtained by dividing the DCR when the SOC exceeds 20% by the DCR when the SOC exceeds 50% may be 2.2 or more. SOC may also be included in the second range. However, even if the SOC is included in the second range, the SOC is close to the third range, and the voltage at the time of discharging the storage cell 11 is relatively low. It is considered that the SOC is equivalent to that included in the third range, and there is no problem in charging the power storage cell 11. Therefore, when the resistance ratio obtained by dividing the DCR by the DCR when the SOC is included in the first range is 2.2 or more, it can be roughly estimated that the SOC of the storage cell 11 is included in the third range.

In FIG. 6, a straight line having a resistivity of 1.2 is shown by a broken line. 1.2 is greater than the resistivity ratio 1.0 obtained by dividing the DCR at 50% SOC by the DCR at 50% SOC. In the example shown in FIG. 6, 1.2 is greater than the resistivity ratio of DCR at 50% SOC divided by DCR at 80% SOC. Therefore, when the resistance ratio obtained by dividing the DCR by the DCR when the SOC is included in the first range is 1.2 or more and less than 2.2, the SOC of the storage cell 11 is included in the second range. ..

In the example shown in FIG. 6, if the resistance ratio obtained by dividing the DCR by the DCR when the SOC is included in the first range is less than 1.2, the SOC of the storage cell 11 may be included in the first range. high. Although there is a possibility that the SOC is included in the second range, even if the SOC is included in the second range, the SOC is close to the first range and the voltage at the time of discharging the storage cell 11 is relatively high. It is possible to use the storage cell 11 assuming that the SOC is equivalent to that included in the first range. Therefore, when the resistance ratio obtained by dividing the DCR by the DCR when the SOC is included in the first range is less than 1.2, it can be roughly estimated that the SOC of the storage cell 11 is included in the first range.

As described above, the resistance ratio obtained by dividing the DCR by the DCR when the SOC is included in the first range decreases monotonically as the SOC increases. Therefore, the SOC decreases in the first range, the second range, and the like according to the resistance ratio. It is possible to determine which range of the third range is included. When the resistance ratio is less than a predetermined first threshold value, it can be determined that the SOC of the storage cell 11 is included in the first range. Similarly, when the resistance ratio is equal to or higher than the first threshold value and is less than a predetermined second threshold value exceeding the first threshold value, it can be determined that the SOC is included in the second range, and the resistance ratio is equal to or higher than the second threshold value. If, it can be determined that the SOC is included in the third range. In the example shown in FIG. 6, the first threshold value is 1.2 and the second threshold value is 2.2. By comparing the resistance ratio with the first threshold value and the second threshold value, the range in which the SOC of the power storage element is included can be easily estimated. A predetermined first threshold value and a second threshold value are stored in the storage unit 33.

FIG. 7 is a flowchart showing a procedure of a process of estimating the SOC of the storage cell 11 performed by the SOC estimation device 3 according to the first embodiment. Hereinafter, the step is abbreviated as S. The calculation unit 31 executes the following processing according to the computer program 331. Before the storage cell 11 is used, that is, before the storage cell 11 is discharged or charged, the CMU2 measures the OCV of the storage cell 11 with the voltage measuring unit 25. The calculation unit 21 of the CMU2 causes the communication unit 26 to transmit data representing the measured OCV value to the SOC estimation device 3. The SOC estimation device 3 acquires the OCV of the storage cell 11 by receiving the data representing the OCV value in the communication unit 34 (S1). The processing of S1 corresponds to the OCV acquisition unit.

The calculation unit 31 of the SOC estimation device 3 determines whether or not the SOC of the storage cell 11 is included in the first range based on the acquired OCV (S2). In S2, the calculation unit 31 determines whether or not the SOC corresponding to the OCV on the SOC-OCV curve represented by the OCV data stored in the storage unit 33 is included in the first range. For example, when the acquired OCV value is equal to or greater than the OCV value corresponding to the lower limit SOC of the first range on the SOC-OCV curve, the calculation unit 31 determines that the SOC is included in the first range. The process of S2 corresponds to the second determination unit.

When it is determined that the SOC of the power storage cell 11 is not included in the first range (S2: NO), the calculation unit 31 charges the power storage cell 11 (S3). In S3, the calculation unit 31 causes the communication unit 34 to transmit a control signal for charging the storage cell 11 to the CMU2. The CMU 2 receives the control signal in the communication unit 26, and the calculation unit 21 causes the storage cell 11 to be charged. Alternatively, the SOC estimation device 3 charges the storage cell 11 by transmitting a control signal to the load circuit 4 and causing the load circuit 4 to supply electric power to the storage cell 11. For example, the SOC estimation device 3 supplies electric power to the storage cell 11 from the alternator included in the load circuit 4. After the end of S3, the SOC estimation device 3 ends the process.

When it is determined that the SOC of the power storage cell 11 is included in the first range (S2: YES), the calculation unit 31 discharges the power storage cell 11 and determines the current and voltage when the power storage cell 11 first discharges. Acquire (S4). In S4, the calculation unit 31 causes the communication unit 34 to transmit a control signal for discharging the storage cell 11 to the CMU2. The CMU 2 receives the control signal in the communication unit 26, and the calculation unit 21 causes the storage cell 11 to discharge. The current measuring unit 24 measures the current flowing through the storage cell 11, and the voltage measuring unit 25 measures the voltage between both ends of the storage cell 11. The calculation unit 21 causes the communication unit 26 to transmit data representing the measured current and voltage values to the SOC estimation device 3. The SOC estimation device 3 acquires the current and voltage of the storage cell 11 by receiving data representing the current and voltage values in the communication unit 34. The calculation unit 31 stores data representing the acquired current and voltage values in the storage unit 33. The processing of S4 corresponds to the second acquisition unit.

Next, the calculation unit 31 calculates the first resistance value indicating the DCR of the storage cell 11 when the SOC is included in the first range, based on the acquired current and voltage (S5). Since the first resistance value is calculated from the current and voltage when the storage cell 11 first discharges while the SOC is included in the first range, the first resistance value is when the SOC of the storage cell 11 is included in the first range. Represents DCR. For example, the calculation unit 31 calculates the first resistance value by dividing the voltage value by the current value. By the processing of S1 to S5, the first resistance value of the storage cell 11 for which the SOC is estimated can be obtained. The calculation unit 31 stores the calculated first resistance value in the storage unit 33. The process of S5 corresponds to the first resistance value calculation unit, and the storage unit 33 corresponds to the first storage unit.

Next, the calculation unit 31 starts using the storage cell 11 (S6). The calculation unit 31 causes the communication unit 34 to transmit the control signal to the CMU 2, the CMU 2 receives the control signal in the communication unit 26, and the calculation unit 21 causes the storage cell 11 to start charging or discharging. Alternatively, the SOC estimation device 3 transmits a control signal to the load circuit 4 and causes the load circuit 4 to use the electric power from the storage cell 11, or causes the load circuit 4 to supply the electric power to the storage cell 11. The power storage cell 11 is charged. For example, when the kinetic energy of the vehicle is regenerated in the load circuit 4, the storage cell 11 is charged, and when the load circuit 4 assists the acceleration of the vehicle by electric power, the storage cell 11 is discharged. Will be done. Normally, charging and discharging of the storage cell 11 are repeated alternately.

Next, the calculation unit 31 acquires the current and voltage at the time of discharging the storage cell 11 (S7). When the storage cell 11 is discharged, the current measuring unit 24 measures the current flowing through the storage cell 11, and the voltage measuring unit 25 measures the voltage between both ends of the storage cell 11. The CMU 2 transmits data representing the measured current and voltage values to the SOC estimation device 3. The SOC estimation device 3 acquires the current and voltage of the storage cell 11 by receiving data representing the current and voltage values in the communication unit 34. The calculation unit 31 stores data representing the acquired set of current and voltage values in the storage unit 33.

In S7, the CMU 2 measures the current and voltage a plurality of times, and the SOC estimation device 3 stores data representing a plurality of sets of current and voltage values in the storage unit 33. Even if the CMU 2 stores data representing a plurality of sets of current and voltage values in the memory 22 or the storage unit 23, and collectively transmits the data representing a plurality of sets of current and voltage values to the SOC estimation device 3. Good. The process of S7 corresponds to the first acquisition unit.

Next, the calculation unit 31 calculates a second resistance value representing DCR when the storage cell 11 discharges based on the acquired current and voltage (S8). In S8, the calculation unit 31 calculates the second resistance value by statistical calculation based on a plurality of sets of current and voltage values measured when the storage cell 11 is discharged. For example, the second resistance value is calculated from a plurality of sets of current and voltage values by the method of least squares. By calculating the second resistance value from a plurality of sets of current and voltage values, the second resistance value is calculated from the current and voltage at a plurality of time points when the storage cell 11 is discharging. By statistically calculating the second resistance value from the current and voltage at a plurality of time points, the second resistance value is calculated with high accuracy. The processing of S8 corresponds to the second resistance value calculation unit.

Next, the calculation unit 31 calculates the resistance ratio obtained by dividing the second resistance value by the first resistance value (S9). In S9, the calculation unit 31 divides the second resistance value calculated in S8 by the first resistance value stored in the storage unit 33. The processing of S9 corresponds to the resistivity calculation unit.

Next, the calculation unit 31 determines whether or not the resistance ratio calculated in S9 is less than the first threshold value stored in the storage unit 33 (S10). When the resistance ratio is less than the first threshold value (S10: YES), the calculation unit 31 determines that the SOC of the storage cell 11 when the current and voltage are measured is included in the first range (S11). The calculation unit 31 then returns the process to S7, and the storage cell 11 continues to be used.

When the resistance ratio is equal to or greater than the first threshold value (S10: NO), the calculation unit 31 determines whether or not the resistance ratio is less than the second threshold value stored in the storage unit 33 (S12). When the resistance ratio is less than the second threshold value (S12: YES), the calculation unit 31 determines that the SOC of the storage cell 11 when the current and voltage are measured is included in the second range (S13). Next, the calculation unit 31 limits the use of the storage cell 11 (S14). For example, in S14, the calculation unit 31 causes the communication unit 34 to transmit the control signal to the load circuit 4, so that the power from the storage cell 11 is not used for the load that requires a relatively high power. It controls the circuit 4. For example, it is prohibited for the motor that assists the acceleration of the vehicle to use the electric power from the electric power storage cell 11, and it is permissible for electrical components such as lights having low electric power to use the electric power from the electric power storage cell 11. .. Alternatively, the arithmetic unit 31 may control to set an upper limit on the electric power from the storage cell 11 used by the load circuit 4. The calculation unit 31 then returns the process to S7, and continues to use the power storage cell 11 while being restricted.

When the resistance ratio is equal to or greater than the second threshold value (S12: NO), the calculation unit 31 determines that the SOC of the storage cell 11 when the current and voltage are measured is included in the third range (S15). Next, the calculation unit 31 charges the power storage cell 11 (S16). After the end of S16, the calculation unit 31 returns the process to S7, and the use of the storage cell 11 is resumed. The processes of S10 to S13 and S15 correspond to the first determination unit.

The SOC estimation device 3 may have a function of outputting information indicating which range the SOC is included in S11, S13, and S15 to the outside. The processing of S1 to S16 ends when the use of the storage cell 11 ends. For example, when the vehicle stops operating and the load circuit 4 no longer uses the electric power from the storage cell 11, the processes of S1 to S16 are terminated.

As described in detail above, the SOC estimation device 3 calculates the resistance ratio obtained by dividing the second resistance value by the first resistance value, and the SOC of the storage cell 11 is set to the first range, the second range, and the second range according to the resistance ratio. The SOC is estimated by determining which range of the third range is included. Since the resistance ratio decreases almost monotonously as the SOC increases, it is possible to determine in which range the SOC is included according to the resistance ratio.

In the state where the SOC is included in the second range, the voltage of the storage cell 11 is relatively low, but it is possible for a load having a low required power to use the power from the storage cell 11. The power storage cell 11 can be used even when the SOC is included in the second range by restricting the use of electric power such as prohibiting the use of electric power by a load requiring high electric power. By the processing of the SOC estimation device 3, it is possible to estimate that the SOC is included in the second range and use the power storage cell 11 while restricting the use. Therefore, as compared with the conventional technique in which the storage cell 11 is used only when the SOC is included in the first range, the range of SOC in which the storage cell 11 can be used is expanded, and the usage efficiency of the storage cell 11 is improved. improves.

When the SOC is included in the third range, the voltage of the storage cell 11 becomes lower, and over-discharging may occur. By the processing of the SOC estimation device 3, it is possible to estimate that the SOC is included in the third range, prohibit the use of the storage cell 11, or charge the storage cell 11. Therefore, it is possible to prevent the storage cell 11 from being over-discharged.

Since the resistance ratio used for estimating the SOC is calculated from the current and voltage measured when the storage cell 11 is used, the SOC of the storage cell 11 can be estimated while the storage cell 11 is in use. Further, since the SOC is estimated without using the SOC-OCV curve, the SOC can be estimated even for the storage cell 11 in which the change in OCV is large with respect to the change in SOC.

<Embodiment 2>
Deterioration of the power storage cell 11 progresses by repeating charging and discharging, and the state of health (SOH) indicating the ratio of the current capacity of the power storage cell 11 to the capacity of the new power storage cell 11 gradually decreases. The relationship between DCR and SOC changes between the BOL (Beginning of Life), which is the state before the deterioration of the storage cell 11, and the EOL (End of Life), which is the state after the deterioration of the storage cell 11.

FIG. 8 is a graph showing an example of the measurement result of the current-voltage characteristic when the storage cell 11 in the EOL is discharged for 10 seconds. The horizontal axis in the figure indicates the current, and the value increases to the right. The vertical axis in the figure indicates the voltage, and the value increases upward. An experiment similar to the experiment for measuring the current-voltage characteristic shown in FIG. 4 was performed. FIG. 8 shows a part of the experimental results and shows the current-voltage characteristics at the time of discharge. The right end of the horizontal axis of FIG. 8 indicates zero current, and the value of the current shown in the figure is negative. The current-voltage characteristics acquired when the SOC of the power storage cell 11 is 20%, 30%, 40%, 50%, 60%, 70%, and 80%, respectively, are shown as black rhombuses, black squares, and black triangles. , Black circle, white rhombus, white square and white circle, respectively. The current-voltage characteristic shown in FIG. 4 is the current-voltage characteristic in BOL. The current-voltage characteristic in EOL is different from the current-voltage characteristic in BOL. Therefore, the DCR at the time of discharging in EOL is also changed as compared with the DCR at the time of discharging in BOL.

FIG. 9 is a graph showing the resistance ratio obtained by dividing the DCR at the time of discharging the storage cell 11 in EOL by the DCR at the time of discharging when SOC is included in the first range. The horizontal axis in the figure shows the SOC, and the horizontal axis shows the resistivity ratio obtained by dividing the DCR in the state where the SOC is each value by the DCR when the SOC is included in the first range. FIG. 9 shows the resistivity ratio obtained by dividing the DCR in the state where the SOC is each value by the DCR in the state where the SOC is 50%, 60%, 70% and 80%, respectively. The resistivity ratios obtained by dividing the DCR at each SOC by the DCR at 50%, 60%, 70% and 80% SOC are indicated by circles, triangles, diamonds and squares, respectively. FIG. 9 shows the resistance ratio calculated from the DCR calculated from the DCR at the time of discharge from the current-voltage characteristic shown in FIG.

The resistivity shown in FIG. 6 is the resistivity in BOL. Like the resistivity ratio in BOL, the resistivity ratio in EOL decreases monotonically as the SOC increases. However, the resistivity ratio in EOL is increased as compared with the resistivity ratio in BOL. Therefore, the first threshold value and the second threshold value in the EOL need to be larger than the first threshold value and the second threshold value in the BOL. In FIG. 9, straight lines indicating the first threshold value and the second threshold value in EOL are shown by broken lines. The second threshold exceeds the first threshold. The first threshold value and the second threshold value in the EOL are larger than the first threshold value and the second threshold value in the BOL shown in FIG. In this way, the appropriate first threshold value and second threshold value change according to the SOH of the storage cell 11. In the second embodiment, the SOC estimation device 3 estimates the SOC of the storage cell 11 by using the first threshold value and the second threshold value according to the SOH.

FIG. 10 is a block diagram showing an example of the functional configuration of the power storage module 10 and the SOC estimation device 3 according to the second embodiment. The storage unit 33 stores OCV data and a threshold database in which a first threshold value and a second threshold value are recorded according to a state in which the SOH of the storage cell 11 is each of a plurality of values. For example, in the relational database, the first threshold value and the second threshold value corresponding to the BOL and the EOL, and the first threshold value and the second threshold value according to the storage cell 11 in the intermediate state between the BOL and the EOL are recorded. .. For example, in a relational database, SOH from BOL to EOL is divided into a plurality of ranges, and a first threshold value and a second threshold value are associated with each SOH range. The storage unit 33 corresponds to the second storage unit. The configuration of the other parts of the power storage module 10 and the SOC estimation device 3 is the same as that of the first embodiment.

The SOC estimation device 3 performs a process of estimating the SOH of the storage cell 11 in parallel with the process of estimating the SOC of the storage cell 11. The SOC estimation device 3 estimates SOH using a conventional method. For example, the SOC estimation device 3 sequentially estimates SOH based on the current and voltage of the storage cell 11 continuously measured by CMU2. Alternatively, the SOC estimation device 3 may estimate the SOH based on a characteristic value such as the internal resistance of the storage cell 11. For example, the estimated value of SOH is stored in the storage unit 33.

The SOC estimation device 3 performs a process of estimating the SOC of the storage cell 11 by the processes of S1 to S16 shown in the flowchart of FIG. 7. In S1 to S9, the SOC estimation device 3 performs the same processing as in the first embodiment. In S10, the calculation unit 31 of the SOC estimation device 3 uses the first threshold value corresponding to the SOH of the storage cell 11 to determine whether or not the resistance ratio calculated in S9 is less than the first threshold value. For example, the calculation unit 31 reads the estimated value of SOH stored in the storage unit 33, reads the first threshold value associated with the range of SOH including the estimated value of SOH from the threshold database, and reads the first threshold value. And the resistivity are compared. The calculation unit 31 may estimate the SOH of the storage cell 11 at the stage of S10 and read out the first threshold value according to the SOH. In S11, the calculation unit 31 performs the same processing as in the first embodiment.

In S12, the calculation unit 31 determines whether or not the resistance ratio calculated in S9 is less than the second threshold value by using the second threshold value according to the SOH of the storage cell 11. For example, the calculation unit 31 reads a second threshold value associated with the range of SOH including the estimated value of SOH from the threshold database, and compares the read first threshold value with the resistance ratio. In S13 to S16, the calculation unit 31 performs the same processing as in the first embodiment.

As described in detail above, also in the second embodiment, the SOC estimation device 3 has the SOC of the storage cell 11 in the first range, the second range, and the second range according to the resistance ratio obtained by dividing the second resistance value by the first resistance value. The SOC is estimated by determining which range of the third range is included. Since the resistance ratio changes according to the SOH of the storage cell 11, the SOC of the storage cell 11 can be estimated accurately by performing the determination using the first threshold value and the second threshold value according to the SOH. Also in the second embodiment, the storage cell 11 can be used even when the SOC is included in the second range. Therefore, as compared with the prior art, the range of SOCs in which the power storage cell 11 can be used is widened, and the usage efficiency of the power storage cell 11 is improved.

In the first and second embodiments, the SOC estimation device 3 may execute processing on each of the plurality of storage cells 11 to estimate the SOC of each storage cell 11. Alternatively, the CMU 2 controls charging and discharging of the storage cells 11 so that the SOCs of the plurality of storage cells 11 are the same, and the SOC estimation device 3 estimates a common SOC among the plurality of storage cells 11. May be good. Alternatively, the power storage module 10 may include a single power storage cell 11 and the SOC estimation device 3 may estimate the SOC of the single power storage cell 11. The SOC estimation device 3 may estimate the SOC of the storage cell 11 included in the plurality of power storage modules 10.

In the first and second embodiments, an example is shown in which the current and voltage when the storage cell 11 first discharges are measured and the first resistance value is calculated. Alternatively, the SOC estimation device 3 stores a predetermined first resistance value in the storage unit 33, and the SOC of the storage cell 11 may be estimated using this first resistance value.

<Embodiment 3>
FIG. 11 is a block diagram showing an example of the functional configuration of the power storage module 10 according to the third embodiment. In the third embodiment, the power storage module 10 includes a plurality of power storage cells 11 and a BMU (Battery Management Unit) 5. The BMU 5 performs a process of estimating the SOC of the storage cell 11. The power storage module 10 corresponds to a power storage device. Alternatively, the BMU 5 corresponds to an SOC estimator. The power storage module 10 executes the SOC estimation method.

The BMU 5 includes a calculation unit 51, a memory 52, a storage unit 53, a current measurement unit 54, a voltage measurement unit 55, and a communication unit 56. The calculation unit 51 is configured by using, for example, a CPU, GPU, or multi-core CPU. The calculation unit 51 may be configured by using a quantum computer. The memory 52 stores information necessary for the calculation in the calculation unit 51. The memory 52 is, for example, a RAM. The storage unit 53 is non-volatile and stores programs and data. The storage unit 53 stores OCV data, a first threshold value, and a second threshold value. The storage unit 53 corresponds to the first storage unit. The calculation unit 51 executes the process according to the program stored in the storage unit 53. For example, the storage unit 53 is a non-volatile semiconductor memory. The current measuring unit 54 measures the current flowing through the plurality of storage cells 11, and the voltage measuring unit 55 measures the voltage between both ends of each storage cell 11. The current measuring unit 54 and the voltage measuring unit 55 correspond to the measuring unit. The communication unit 56 communicates with the outside of the power storage module 10. A load circuit 4 is connected to the communication unit 56. The power storage module 10 supplies electric power to the load included in the load circuit 4.

The BMU 5 executes the same processing as the processing of S1 to S16 executed by the SOC estimation device 3 in the first embodiment. By measuring the OCV of the storage cell 11 with the voltage measuring unit 55 before using the storage cell 11, the BMU 5 acquires the OCV of the storage cell 11 (S1). The calculation unit 51 determines whether or not the SOC of the storage cell 11 is included in the first range based on the acquired OCV (S2). When it is determined that the SOC is not included in the first range (S2: NO), the calculation unit 51 charges the storage cell 11 (S3) and ends the process.

When it is determined that the SOC of the storage cell 11 is included in the first range (S2: YES), the calculation unit 51 discharges the storage cell 11, and the current measuring unit 54 measures the current flowing through the storage cell 11. By measuring the voltage between both ends of the storage cell 11 with the voltage measuring unit 55, the BMU 5 acquires the current and the voltage when the storage cell 11 first discharges (S4). The calculation unit 51 calculates the first resistance value indicating the DCR of the storage cell 11 when the SOC is included in the first range based on the acquired current and voltage (S5). The calculation unit 51 stores the calculated first resistance value in the storage unit 53.

Next, the calculation unit 51 starts using the storage cell 11 (S6). The calculation unit 51 causes the power storage cell 11 to start charging or discharging. Alternatively, the calculation unit 51 causes the communication unit 56 to transmit a control signal to the load circuit 4 and causes the load circuit 4 to use the electric power from the storage cell 11, or causes the load circuit 4 to supply the electric power to the storage cell 11. This causes the power storage cell 11 to be charged. When the storage cell 11 is discharged, the current measuring unit 54 measures the current flowing through the storage cell 11, and the voltage measuring unit 55 measures the voltage between both ends of the storage cell 11, so that the BMU 5 discharges the storage cell 11. The current and voltage of the hour are acquired (S7). The calculation unit 51 stores data representing a set of current and voltage values in the storage unit 53.

Next, the calculation unit 51 calculates a second resistance value representing DCR when the storage cell 11 discharges based on the acquired current and voltage (S8). In S8, the calculation unit 51 calculates the second resistance value by statistical calculation based on a plurality of sets of current and voltage values measured when the storage cell 11 is discharged. Next, the calculation unit 51 calculates the resistance ratio obtained by dividing the second resistance value by the first resistance value (S9).

Next, the calculation unit 51 determines whether or not the resistance ratio calculated in S9 is less than the first threshold value (S10). When the resistance ratio is less than the first threshold value (S10: YES), the calculation unit 51 determines that the SOC of the storage cell 11 is included in the first range (S11), and returns the process to S7.

When the resistance ratio is equal to or greater than the first threshold value (S10: NO), the calculation unit 51 determines whether or not the resistance ratio is less than the second threshold value (S12). When the resistance ratio is less than the second threshold value (S12: YES), the calculation unit 51 determines that the SOC of the storage cell 11 is included in the second range (S13). The calculation unit 51 limits the use of the power storage cell 11 (S14), and returns the process to S7.

When the resistance ratio is equal to or greater than the second threshold value (S12: NO), the calculation unit 51 determines that the SOC of the storage cell 11 is included in the third range (S15), and charges the storage cell 11 (S16). After the end of S16, the calculation unit 51 returns the process to S7, and the use of the storage cell 11 is resumed. The BMU 5 may have a function of outputting information indicating which range the SOC is included in S11, S13, and S15 to the outside. The processing of S1 to S16 ends when the use of the storage cell 11 ends.

The BMU 5 may be in a form in which the SOC is estimated according to the SOH of the storage cell 11. In this form, the storage unit 53 stores a threshold database in which the first threshold value and the second threshold value are recorded according to the state in which the SOH of the storage cell 11 is each of a plurality of values. The storage unit 53 corresponds to the second storage unit. The BMU 5 performs a process of estimating the SOH of the storage cell 11. For example, the estimated value of SOH is stored in the storage unit 53.

The BMU 5 executes the same processing as the processing of S1 to S16 executed by the SOC estimation device 3 in the second embodiment. In S1 to S9, the calculation unit 51 performs the same processing as described above. In S10, the calculation unit 51 uses the first threshold value according to the SOH of the storage cell 11 to determine whether or not the resistance ratio calculated in S9 is less than the first threshold value. The calculation unit 51 may estimate the SOH of the storage cell 11 at the stage of S10 and read out the first threshold value according to the SOH. In S11, the calculation unit 51 performs the same processing as described above. In S12, the calculation unit 51 determines whether or not the resistance ratio is less than the second threshold value by using the second threshold value according to the SOH of the storage cell 11. In S13 to S16, the calculation unit 51 performs the same processing as described above.

As described in detail above, in the third embodiment, the SOC of the power storage cell 11 is estimated inside the power storage module 10. The BMU 5 determines whether the SOC of the storage cell 11 is included in the first range, the second range, or the third range according to the resistance ratio obtained by dividing the second resistance value by the first resistance value. By doing so, the SOC is estimated. Also in the third embodiment, the storage cell 11 can be used even when the SOC is included in the second range. Therefore, as compared with the prior art, the range of SOCs in which the power storage cell 11 can be used is widened, and the usage efficiency of the power storage cell 11 is improved.

In the third embodiment, the BMU 5 may estimate the SOC for each of the plurality of storage cells 11, and instead controls the charging and discharging of the storage cells 11 so that the SOCs of the plurality of storage cells 11 are the same. Then, the SOC common to the plurality of storage cells 11 may be estimated. Alternatively, the power storage module 10 may include a single power storage cell 11 and the BMU 5 may estimate the SOC of the single power storage cell 11.

In the third embodiment, an example is shown in which the current and voltage when the storage cell 11 first discharges are measured and the first resistance value is calculated. Alternatively, the BMU 5 stores a predetermined first resistance value in the storage unit 53, and the SOC of the storage cell 11 may be estimated using this first resistance value.

In the first to third embodiments, the SOC is in the range of 50% to 80% as the first range, the SOC is in the range of 20% to 50% as the second range, and the SOC is in the range of 0% to 20% as the third range. An example of the range is shown. The first range, the second range, and the third range may be other ranges according to the characteristics of the storage cell 11. Further, the first threshold value and the second threshold value used in the first to third embodiments are examples, and other values according to the characteristics of the storage cell 11 may be used as the first threshold value and the second threshold value.

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

10 Power storage module 11 Power storage cell 2 CMU
3 SOC estimator 4 Load circuit 5 BMU

Claims (8)

An SOC estimation device that estimates the SOC (State of Charge) of a power storage element.
A first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range.
A first acquisition unit that acquires the current and voltage when the power storage element discharges, and
Based on the acquired current and voltage, a second resistance value calculation unit that calculates a second resistance value representing the resistance when the power storage element discharges, and a second resistance value calculation unit.
A resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the calculated second resistance value by the first resistance value, and
The first determination for determining whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included according to the calculated resistance ratio. SOC estimation device including a unit. An OCV acquisition unit that acquires the OCV (Open Circuit Voltage) of the power storage element before the power storage element charges or discharges.
Based on the acquired OCV, a second determination unit that determines whether or not the SOC of the power storage element is included in the first range, and a second determination unit.
When the SOC of the power storage element is included in the first range, a second acquisition unit that acquires the current and voltage when the power storage element first discharges, and
The SOC estimation device according to claim 1, further comprising a first resistance value calculation unit that calculates the first resistance value based on the current and voltage acquired by the second acquisition unit. When the resistance ratio is less than a predetermined first threshold value, the first determination unit determines that the SOC of the power storage element is included in the first range, and the resistance ratio is the first threshold value. When the above is the above and the value is less than the predetermined second threshold value exceeding the first threshold value, it is determined that the SOC of the power storage element is included in the second range, and the resistance ratio is equal to or higher than the second threshold value. The SOC estimation device according to claim 1 or 2, wherein the SOC of the power storage element is determined to be included in a third range lower than the second range. The first threshold value is a value obtained by dividing the resistance of the power storage element when the SOC of the power storage element is the lower limit of the first range by the resistance when the SOC of the power storage element is included in the first range. It is a value that exceeds
The second threshold is the resistance of the power storage element when the SOC of the power storage element is the upper limit of the third range, and the resistance of the power storage element when the SOC of the power storage element is the lower limit of the first range. The SOC estimation device according to claim 3, wherein the value is equal to or greater than the value divided by. A second storage unit for storing the first threshold value and the second threshold value, which differ according to the SOH (State of Health), for each of the plurality of SOHs is further provided.
The first determination unit uses the first threshold value and the second threshold value stored by the first storage unit for the SOH of the power storage element to determine in which range the SOC of the power storage element is included. The SOC estimation device according to claim 3 or 4. The SOC estimation device according to any one of claims 1 to 5, wherein the second resistance value calculation unit calculates the second resistance value from currents and voltages at a plurality of time points when the power storage element is discharging. .. A power storage device equipped with a power storage element
A first storage unit that stores a first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in a predetermined first range.
A measuring unit that measures the current and voltage when the power storage element discharges,
Based on the acquired current and voltage, a second resistance value calculation unit that calculates a second resistance value representing the resistance when the power storage element discharges, and a second resistance value calculation unit.
A resistance ratio calculation unit that calculates the resistance ratio obtained by dividing the calculated second resistance value by the first resistance value, and
The first determination for determining whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included according to the calculated resistance ratio. A power storage device equipped with a unit. It is a method of estimating the SOC of a power storage element.
Measure the current and voltage when the power storage element discharges,
Based on the acquired current and voltage, a second resistance value representing the resistance when the power storage element discharges is calculated.
The resistance ratio obtained by dividing the calculated second resistance value by the first resistance value representing the resistance of the power storage element when the SOC of the power storage element is included in the predetermined first range is calculated.
SOC estimation method for determining whether the SOC of the power storage element is included in the first range or the second range in which the SOC lower than the first range is included according to the calculated resistance ratio. ..

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