JP7449738B2 - Method, device, program and recording medium for estimating battery condition - Google Patents

Description

The present invention relates to a method, device, program, and recording medium for estimating a battery state, and particularly to a method for estimating a full charge capacity of a battery and a correlation between an open circuit voltage and a charging rate.

Since the characteristics of a battery change greatly depending on the environment in which it is used and over time, it is necessary to constantly understand the battery condition. In particular, for batteries installed in vehicles such as automobile starter batteries, battery failure or abnormality may lead to serious events such as accidents, so in-vehicle sensors that detect battery failure or abnormality are It is common to have means for estimating the battery condition, particularly the correlation between the full charge capacity SOH of the battery, the open circuit voltage OCV, and the charging rate SOC.

As a method for estimating these, using voltages V1 and V2 at two timings with different charging states, voltage VM at full charge, voltage V0 at charging rate SOC = 0%, and integrated current amount Q between two points, The full charge capacity can be calculated by calculating the full charge capacity as SOH=Q×(VM-V0)/|V1-V2| (Patent Document 1) or based on the SOC difference before and after charging and the integrated charging current value during charging. A calculation method (Patent Document 2) has been proposed.

Japanese Patent Application Publication No. 8-179018 Japanese Patent Application Publication No. 2014-185896

However, in the method described in Patent Document 1, the voltage VM at full charge and the voltage V0 at charging rate SOC=0% need to be known. Further, the method described in Patent Document 2 requires means for determining the SOC difference before and after charging, and for this purpose, the correlation between OCV and SOC needs to be known. In this way, with conventional methods, it is necessary to know the characteristics of the battery to be estimated (such as the correlation between VM, V0, OCV and SOC). If the value changes, estimation becomes difficult or the accuracy decreases significantly.

Therefore, there is a need for a method, device, program, and recording medium that records the program that can accurately estimate the full charge capacity SOH, the correlation between the open circuit voltage OCV, and the charging rate SOC even for batteries with different characteristics. It was getting worse.

The above problem is a method (20) for estimating the state of a battery (1), which includes steps (202, 206, 212) of measuring the voltage and charging/discharging current of the battery (1) in time series, respectively; Steps (203, 213) of determining the open circuit voltages (OCV1, OCV2) of the battery (1) at two different points in time based on the measured voltages; A step (214) of determining the amount of change in open circuit voltage (ΔOCV) between two different points in time, and determining the amount of change in electrical quantity (ΔQ) of the battery (1) between two different points in time based on the measured charging and discharging current. Step (207), Step (216) of calculating the ratio of the open circuit voltage change amount to the amount of electricity change amount (ΔOCV/ΔQ, ΔQ/ΔOCV), and The known correlation (30) between the ratio of circuit voltage change and electrical quantity change (ΔOCV/ΔQ, ΔQ/ΔOCV) and full charge capacity (SOH), and the calculated ratio (ΔOCV/ΔQ, ΔQ/ estimating (217) the full charge capacity (SOH) of the battery (1) based on the ΔOCV).

That is, from the measured values of the voltage and current of the battery (1), the ratio (ΔOCV/ΔQ, ΔQ/ΔOCV) between the current open circuit voltage change and the amount of electricity change is calculated, and the calculated ratio is calculated in advance from multiple The characteristics of the battery (1) to be estimated (correlation between VM, V0, OCV and SOC, etc.) are estimated by determining the full charge capacity (SOH) in correspondence with the known correlation (30) determined using the battery. ) is unknown, it is possible to estimate the full charge capacity SOH with high accuracy.

In the present invention, "chronologically" means a plurality of different points in time, regardless of whether it is periodic or not. For example, "time-series measurements" refers not only to measurements that are performed periodically, but also to irregular measurements that are performed at multiple different points in time as needed or in response to external requests. include.

In the above method, when the battery (1) is a battery (1) mounted on a vehicle, it is desirable that the two different times are before and after the vehicle is running. For on-board batteries, the amount of charge and discharge of the battery increases when the vehicle is running, so the open circuit voltage change (ΔOCV) and electrical quantity change (ΔQ) required for estimating the full charge capacity SOH should be set to large values. This makes it possible to keep estimation errors small.

Further, the above method includes a step (218) of calculating the amount of change in charging rate (ΔSOC) based on the amount of change in electricity quantity (ΔQ) and the estimated full charge capacity (SOH), and a step (218) when the battery (1) is almost fully charged. Steps (210, 220) of calculating the charging rate (SOCo) and open circuit voltage (OCVo) when the battery (1) is almost full. The method may further include a step (221) of estimating a correlation (40) between the open circuit voltage of the battery (1) and the charging rate based on the charging rate (SOCo) and the open circuit voltage (OCVo) during charging. desirable.

By determining the correlation (40) from SOH, ΔQ, SOCo, and OCVo determined from the measured voltage and current values of battery (1), the open circuit voltage can be determined accurately even for battery (1) whose characteristics are unknown. It becomes possible to estimate the correlation between the charging rate and the charging rate.

Furthermore, the above-mentioned problem can also be solved by an apparatus and a program that implement the method described above, and a recording medium on which the program is recorded.

3 is a flowchart of a battery state estimation method and program according to the present invention. 1 is a schematic configuration diagram of a battery state estimation device according to the present invention. FIG. 3 is a diagram showing a known correlation between the ratio of the amount of change in open circuit voltage and the amount of change in electrical quantity, and the full charge capacity. It is an example of the correlation between the estimated open circuit voltage of the battery and the charging rate.

FIG. 2 shows a schematic configuration diagram of a battery state estimating device 10 that is an embodiment of the present invention. The battery state estimating device 10 is connected to the battery 1 and the charging circuit 2. The battery 1 is, for example, a lead-acid battery for vehicles. The charging circuit 2 is a power supply circuit that is connected to the battery 1 and supplies charging current. Further, the battery 1 is connected to a load 3, for example, an in-vehicle electrical device such as a motor, a control circuit, and a lighting device. A battery 1, a charging circuit 2, a load 3, and a battery state estimation device 10 are mounted on a vehicle (not shown).

The battery state estimation device 10 includes a voltage measurement section 11, a current measurement section 12, a storage section 13, and a control section 14. The voltage measurement section 11, the current measurement section 12, and the storage section 13 are electrically connected to the control section 14 and can communicate with each other using data and signals. The voltage measurement section 11, the current measurement section 12, the storage section 13, and the control section 14 may be integrated into one chip like an ASIC.

The voltage measurement unit 11 is connected between the terminals of the battery 1, measures the voltage between the terminals periodically and/or in response to a request from the control unit 14, and sends the measured voltage to the control unit 14. The current measuring section 12 is connected between the battery 1 and the charging circuit 2 so that the battery 1, the current measuring section 12, and the load 3 are connected in parallel, and is connected to the charging/discharging current flowing through the battery 1. That is, the charging current flowing into the battery 1 and the discharging current flowing from the battery 1 to the load 3 are measured periodically and/or in response to a request from the control section 14, and the measured voltage is sent to the control section 14. .

The control unit 14 includes a processor, acquires measurement signals and measurement data from the voltage measurement unit 11 and the current measurement unit 12, and calculates the full charge capacity SOH of the battery 1 and the correlation 40 between the open circuit voltage OCV and the charging rate SOC. Executes and controls the process for estimation. Furthermore, the control section 14 may be configured to control the timing at which the voltage measurement section 11 and the current measurement section 12 perform measurements.

The storage unit 13 is a computer-readable recording medium that includes a semiconductor memory such as a RAM, an SSD, and a flash memory, and a magnetic memory such as an HDD. The storage unit 13 stores programs executed by the processor of the control unit 14 , various parameters used in information processing by the program, correlation 40 between the estimated full charge capacity SOH, the open circuit voltage OCV, and the charging rate SOC, and the control unit 14 . stores the measured values obtained from the voltage measuring section 11 and the current measuring section 12. Furthermore, the storage unit 13 stores a known correlation 30 between the ratio of the open circuit voltage change amount to the amount of electricity change amount and the full charge capacity of a plurality of batteries having different full charge capacities. FIG. 3 shows an example of the correlation 30.

FIG. 3 is a graph in which the horizontal axis shows the amount of change in open circuit voltage ΔOCV/ΔQ per unit change in the amount of electricity, and the vertical axis shows the full charge capacity SOH. Data 31, 32, 33, . . . obtained from the batteries are shown as dots. As is clear from the figure, there is a correlation between the two, and a linearly approximated correlation 30 is shown by a broken line. The storage unit 13 stores the correlation 30 in the form of a table or approximate formula, and the control unit 14 reads out the stored correlation 30 to determine the full charge capacity SOH corresponding to the estimated battery ΔOCV/ΔQ. be able to. Note that even if the ratio between the amount of change in open circuit voltage and the amount of change in electrical quantity is the reciprocal of the amount of voltage change ΔOCV/ΔQ per unit amount of change in electrical quantity, that is, the amount of electrical quantity change ΔQ/ΔOCV with respect to the unit amount of voltage change. good.

Next, a battery state estimation method 20, which is an embodiment of the present invention, will be explained with reference to the flowchart 20 of FIG. A program for executing the functions shown in the flowchart 20 by the processor of the control unit 14 is recorded in the storage unit 13 of the battery state estimating device 10.

The state estimation is performed from a stopped state (steps 202, 203) before the vehicle travels (steps 205 to 210) to a stopped state after the vehicle travels (from 212). Since the battery 1 is mainly charged and discharged while the vehicle is running, the parameters ΔOCV and ΔQ required in the estimation process can be increased by using the measured values before and after the vehicle is running. Further, the open circuit voltage OCV, which is another necessary parameter, can be measured or estimated more stably and with higher accuracy when the vehicle is stopped, when the amount of charging and discharging of the battery 1 is small. Therefore, by estimating the full charge capacity SOH and the correlation 40 between the open circuit voltage OCV and the charging rate SOC based on the measurement results before and after driving and when stopping, it is possible to perform highly accurate estimation with small errors. becomes possible. The estimation method 20 will be explained below in accordance with the processing order.

First, the control unit 14 determines whether or not the vehicle is in a running state, and if the vehicle is in a running state, waits until the vehicle is in a stopped state (step 201). When it is determined that the vehicle has stopped, the control unit 14 requests the voltage measurement unit 11 to measure the voltage between the terminals of the battery 1 and obtains the voltage measured by the voltage measurement unit 11, or 11 acquires the latest voltage periodically measured from the storage unit 13 (step 202).

Next, the control unit 14 calculates the open circuit voltage OCV1 from the obtained voltage (step 203). If the state in which the amount of charging and discharging of the battery 1 continues to be small and the polarization due to charging and discharging is sufficiently eliminated and the voltage is stable, the obtained measured voltage can be regarded as the open circuit voltage OCV1. On the other hand, if the voltage is not stable, the open circuit voltage OCV1 can be found by sampling multiple voltages in time series and estimating the voltage convergence value using an approximate formula. .

The above operation is repeated until the vehicle starts running (step 204), and the open circuit voltage OCV1 is updated. Ultimately, OCV1 becomes the open circuit voltage at the time the vehicle starts running.

When it is determined that the vehicle is running, the control unit 14 determines the amount of change ΔQ in the amount of electricity before and after the vehicle is running. Specifically, first, the electric quantity change amount ΔQ is reset to 0 (step 205). Next, the control unit 14 requests the current measurement unit 12 to measure the charging/discharging current of the battery 1 and obtains the magnitude of the current measured by the current measurement unit 12, or the current measurement unit 12 periodically The latest current magnitude being measured is acquired from the storage unit 13 (step 206).

Next, the control unit 14 updates ΔQ (step 207). More specifically, the obtained current is multiplied by the time interval (for example, measurement cycle) from the acquisition of the immediately preceding measured current to obtain the amount of electricity in the battery 1 that has changed between measurements, and is added to ΔQ. In this way, by integrating the amount of electricity determined from the measured current, it is possible to determine the amount of change ΔQ in the amount of electricity from the time when the vehicle starts traveling to the present time.

Next, the control unit 14 determines whether the battery 1 is fully charged or nearly fully charged (hereinafter simply referred to as a "fully charged state") (step 208). For example, when the charging/discharging current becomes smaller than a predetermined threshold value, it can be determined that the battery is in a fully charged state. Further, the fully charged state may be determined based on the charging resistance obtained by dividing the difference between the charging voltage measured by the voltage measuring section 11 and the open circuit voltage by the charging current measured by the current measuring section 12. If it is determined that the battery is fully charged, the control unit 14 determines the charging rate SOCo based on the charging resistance of the battery 1 (step 210). At this time, in addition to the charging resistance, the charging rate SOCo may be determined by adding the discharging resistance during engine starting and the resistance due to pulse discharge. Furthermore, the value of the determined charging rate SOCo may be finely adjusted in consideration of the influence of temperature, charging voltage, etc. Instead of estimating the charging rate SOCo, the charging rate SOCo may be simply set to 100%.

On the other hand, if it is determined that the battery is not in a fully charged state as a result of the full charge determination (step 208), the estimation of SOCo (step 210) is skipped.

Thereafter, the control unit 14 repeats steps 206 to 210 until the vehicle comes to a halt (step 211). Finally, the amount of change in the amount of electricity ΔQ is the amount of change in the amount of electricity caused by charging and discharging the battery 1 from the time when the vehicle starts traveling to the time when the vehicle ends. Furthermore, if it is determined in step 208 that the battery is fully charged while the vehicle is running, the final charging rate SOCo will be the charging rate at the end of the vehicle running.

When it is determined that the vehicle has stopped, the control unit 14 requests the voltage measurement unit 11 to measure the voltage between the terminals of the battery 1 and obtains the voltage measured by the voltage measurement unit 11, or 11 acquires the latest voltage periodically measured from the storage unit 13 (step 212). Then, the control unit 14 determines the open circuit voltage OCV2 at the end of travel from the acquired voltage (step 213). If the state in which the amount of charging and discharging of the battery 1 continues to be small and the polarization due to charging and discharging is sufficiently eliminated and the voltage is stable, the obtained measured voltage can be regarded as the open circuit voltage OCV2. On the other hand, when the voltage is not stable, the open circuit voltage OCV2 can be obtained by sampling the voltage in time series and estimating the convergence value of the voltage using an approximation formula.

Next, the control unit 14 calculates the difference between the open circuit voltage OCV1 at the start of running and the open circuit voltage OCV2 at the end of running, thereby determining the amount of change in open circuit voltage between the start of running and the end of running. ΔOCV is determined (step 214).

Further, the control unit 14 determines whether the absolute value of the amount of change in the amount of electricity ΔQ while the vehicle is running is larger than a predetermined threshold (step 215). If the absolute value of the electrical quantity change ΔQ is less than a predetermined threshold value, there is a concern that the influence of errors will become large and the accuracy of the estimation result will deteriorate. Returning to steps 202 and 203), the open circuit voltage change amount ΔOCV and the electrical quantity change amount ΔQ before and after the vehicle travels are determined.

If the absolute value of the amount of change in electrical quantity ΔQ while the vehicle is running is larger than a predetermined threshold value, it is considered that the corresponding amount of change in open circuit voltage ΔOCV is also large, so that high estimation accuracy can be expected. In this case, the control unit 14 calculates a ratio between the obtained open circuit voltage change amount ΔOCV and the amount of electricity change amount ΔQ (step 216). In this embodiment, since the known correlation 30 stored in the storage unit 13 is the correlation between the amount of voltage change per unit amount of change in electricity and the full charge capacity, ΔOCV/ΔQ is determined as a ratio.

Next, the control unit 14 estimates the full charge capacity SOH by referring to the known correlation 30 stored in the storage unit 13 and obtaining the full charge capacity SOH corresponding to the obtained ΔOCV/ΔQ ( step 217). Note that when the known correlation 30 stored in the storage unit 13 is a correlation between the amount of change in electrical quantity for a unit voltage change and the full charge capacity, ΔQ/ΔOCV is calculated as a ratio and the corresponding full charge capacity is determined. SOH can be estimated. The estimated full charge capacity SOH is stored in the storage unit 13 and can be used to control the vehicle and battery 1 as needed.

As described above, even if the characteristics of the battery 1 to be estimated (such as the correlation between VM, V0, OCV and SOC) are unknown, the full charge capacity SOH can be accurately estimated from the measured voltage and current values of the battery 1. becomes possible.

The battery state estimating device 10 can further estimate a correlation 40 between the open circuit voltage OCV of the battery 1 and the charging rate SOC as shown in FIG. 4 . Specifically, first, the amount of change in the amount of electricity ΔQ obtained in steps 205 to 207 before and after the vehicle runs is divided by the full charge capacity SOH estimated in step 217 to obtain the amount of change in the charging rate ΔSOC (step 218). The determined charging rate change amount ΔSOC is the charging rate change amount ΔSOC corresponding to the open circuit voltage change amount ΔOCV before and after the vehicle travels. Therefore, the slope 42 of the correlation 40 between the open circuit voltage OCV and the charging rate SOC can be determined from the open circuit voltage change amount ΔOCV and the charging rate change amount ΔSOC.

Next, the control unit 14 determines whether the charging rate SOCo in the fully charged state has been determined (step 219). If the charging rate SOCo can be determined, the open circuit voltage OCV2 estimated immediately after the vehicle stops running is set as the closed/open circuit voltage OCVo in the fully charged state (step 220). A case where the charging rate SOCo can be determined is a case where a full charge determination is made during driving, so the charging rate SOCo records the charging rate in a fully charged state at the end of vehicle driving. . The open circuit voltage OCV2 estimated immediately after the vehicle stops running is the open circuit voltage corresponding to the charging rate SOCo.

Therefore, the point 41 on the correlation 40 can be specified from the obtained OCVo and SOCo. By finding a straight line from the identified point 41 and slope 42, it is possible to estimate the correlation 40 between the open circuit voltage OCV of the battery 1 and the charging rate SOC (step 221). The estimated correlation 40 is stored in the storage unit 13 in a desired format such as a table or an approximation formula, and can be used to control the vehicle and battery 1 as needed. On the other hand, in step 219, if the charging rate SOCo in the fully charged state is not determined, the process ends without estimating the correlation 40 between the open circuit voltage OCV and the charging rate SOC.

By using the above method, even if the characteristics of battery 1 to be estimated (VM, V0, correlation between OCV and SOC, etc.) are unknown, the open circuit voltage OCV and charge can be determined accurately from the measurement results of battery 1 voltage and current. It becomes possible to estimate the correlation 40 with the rate SOC.

The method, device, and program for estimating the battery state according to the present invention, as well as the recording medium on which the program is recorded, have been described above, but the present invention is not limited to the above-described embodiments. It includes all aspects falling within the inventive concept and scope of the claims. For example, in the embodiment described above, a method for estimating the condition of a lead-acid battery for use in a vehicle was explained as an example, but a method for estimating the state of a lead-acid battery for use in a vehicle is explained as an example. It can also be applied to battery state estimation. Further, the known correlation 30 stored in the storage unit may be a correlation based on multivariable function approximation instead of linear approximation.

1 Battery 2 Charging circuit 3 Load 10 Battery state estimation device 11 Voltage measuring section 12 Current measuring section 13 Storage section 14 Control section

Claims (7)

A method for estimating a battery condition, the method comprising:
Measuring the voltage and charging/discharging current of the battery in time series;
determining the open circuit voltage of the battery at two different points in time based on the measured voltage or the voltage estimated from the measured voltage ;
determining an amount of change in open circuit voltage between the two different points of time based on the open circuit voltage;
determining an amount of change in the amount of electricity of the battery between the two different points of time based on the measured charging and discharging current;
determining a ratio between the amount of change in the open circuit voltage and the amount of change in the amount of electricity;
The ratio between the open circuit voltage change and the amount of electricity change for multiple batteries with different full charge capacities,
estimating the full charge capacity of the battery based on a known correlation with the full charge capacity and the determined ratio;
including methods. The battery is a battery mounted on a vehicle,
The two different points in time are points before and after the vehicle travels,
The method according to claim 1. calculating a charging rate change amount based on the amount of change in electricity amount and the estimated full charge capacity;
determining a charging rate and an open circuit voltage when the battery is almost fully charged;
Estimating the correlation between the open circuit voltage of the battery and the charging rate based on the open circuit voltage change amount, the charging rate change amount, and the charging rate and open circuit voltage when the battery is almost fully charged. and,
3. The method of claim 1 or 2, further comprising: A device for estimating the state of a battery, the device comprising:
a voltage measuring unit that measures the voltage of the battery;
a current measuring unit that measures charging and discharging current of the battery;
The ratio between the open circuit voltage change and the amount of electricity change for multiple batteries with different full charge capacities,
a storage unit that stores a known correlation with full charge capacity;
a control unit capable of communicating with the voltage measurement unit, the current measurement unit, and the storage unit;
Equipped with
The control unit includes:
Obtaining the voltage of the battery measured by the voltage measuring unit and the charging/discharging current of the battery measured by the current measuring unit, respectively in time series,
Determining the open circuit voltage of the battery at two different times based on the acquired voltage or the voltage estimated from the acquired voltage ,
Based on the open circuit voltage, determine the amount of change in the open circuit voltage between the two different points in time,
Based on the acquired charging and discharging current, determine the amount of change in the amount of electricity of the battery at the two different times,
Determining the ratio between the open circuit voltage change amount and the electrical quantity change amount,
configured to estimate a full charge capacity of the battery based on the correlation and the determined ratio;
Device. The control unit further includes:
Determining the amount of change in the charging rate based on the amount of change in the amount of electricity and the estimated full charge capacity,
Based on the obtained voltage, determine the charging rate and open circuit voltage when the battery is almost fully charged,
Estimating the correlation between the open circuit voltage of the battery and the charging rate based on the open circuit voltage change amount, the charging rate change amount, and the charging rate and open circuit voltage when the battery is almost fully charged. 5. The device according to claim 4, wherein the device is configured to. a voltage measuring section that measures the voltage of the battery;
a current measuring unit that measures charging and discharging current of the battery;
The ratio between the open circuit voltage change and the amount of electricity change for multiple batteries with different full charge capacities,
a storage unit that stores a known correlation with full charge capacity;
a control unit including a processor and capable of communicating with the voltage measurement unit, the current measurement unit, and the storage unit;
A control program for a device for estimating a battery state, comprising:
the processor;
Obtaining the voltage of the battery measured by the voltage measuring unit and the charging/discharging current of the battery measured by the current measuring unit, respectively in time series,
Determining the open circuit voltage of the battery at two different times based on the obtained voltage or the voltage estimated from the measured voltage ,
Based on the open circuit voltage, determine the amount of change in the open circuit voltage between the two different points in time,
Based on the acquired charging and discharging current, determine the amount of change in the amount of electricity of the battery at the two different times,
Determining the ratio between the open circuit voltage change amount and the electrical quantity change amount,
executing a function of estimating the full charge capacity of the battery based on the correlation and the determined ratio;
program. A computer-readable recording medium on which the program according to claim 6 is recorded.

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