JP2021150220A - Method of estimating battery state, device, program, and storage medium - Google Patents

Abstract

To provide a method of accurately estimating a full-charging amount or a correlation of an open circuit voltage and a charging rate for batteries having different characteristics, a device, a program, and a storage medium.SOLUTION: A method of estimating a battery state, includes: steps 202, 206, and 212 of measuring a voltage and a charging/discharging current of a battery in time series; steps 203 and 213 of calculating an open circuit voltage of the battery at two different time points on the basis of the measured voltage; a step 214 of calculating an open circuit voltage change amount ΔOCV between the two different time points on the basis of the open circuit voltage; a step 207 of calculating an electric amount change amount ΔQ at the two different time points on the basis of the measured charging/discharging current; and a step 216 of calculating proportions ΔOCV/ΔQ and ΔQ/ΔOCV of the open circuit voltage change amount and the electric amount change amount. A full-charging capacity of the battery is estimated on the basis of the proportion of the open circuit voltage change amount and the electric amount change amount and the existed correlation with the full-charging capacity of a plurality of batteries having different full-charging capacity.SELECTED DRAWING: Figure 1

Description

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

Since the characteristics of a battery change significantly with time depending on the usage environment, it is required to constantly grasp the battery state. In particular, in the case of batteries mounted on vehicles such as automobile starter batteries, battery failures / abnormalities may lead to serious events such as accidents. Therefore, in-vehicle sensors that detect battery failures / abnormalities are used. Generally, a means for estimating the battery state, particularly the full charge capacity SOH of the battery, and the correlation between the open circuit voltage OCV and the charge rate SOC is installed.

As these estimation methods, the voltages V1 and V2 at two timings with different charging states, the voltage VM at the time of full charge, the voltage V0 at the time of charging rate SOC = 0%, and the current integration amount Q between the two points are used. Full charge capacity Based on the method of obtaining as SOH = Q × (VM-V0) / | V1-V2 | (Patent Document 1), the SOC difference before and after charging, and the integrated charging current value during charging, the full charge capacity is determined. A method for calculating (Patent Document 2) has been proposed.

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

However, in the method described in Patent Document 1, it is necessary to know the voltage VM at the time of full charge and the voltage V0 at the time of charge rate SOC = 0%. Further, in the method described in Patent Document 2, a means for obtaining the SOC difference before and after charging is required, and for this purpose, it is necessary that the correlation between OCV and SOC is known. As described above, in the conventional method, it is necessary to know the characteristics of the battery to be estimated (such as the correlation between VM, V0, OCV and SOC), and the characteristics are due to replacement with a battery having different characteristics or deterioration over time. If is changed, it will be difficult to estimate or the accuracy will be significantly reduced.

Therefore, even for batteries having different characteristics, a method, an apparatus, a program, and a recording medium on which the full charge capacity SOH and the correlation between the open circuit voltage OCV and the charge rate SOC can be estimated with high accuracy are required. Was being done.

The above object is a method (20) for estimating the state of the battery (1), in which the voltage of the battery (1) and the charge / discharge current are measured in time series (202, 206, 212), respectively. Steps (203, 213) for obtaining the open circuit voltage (OCV1, OCV2) of the battery (1) at two different time points based on the measured voltage, and different 2 based on the open circuit voltage (OCV1, OCV2). Based on the step (214) for obtaining the open circuit voltage change amount (ΔOCV) between two time points and the measured charge / discharge current, the electric amount change amount (ΔQ) of the battery (1) is obtained between two different time points. Step (207), step (216) for obtaining the ratio (ΔOCV / ΔQ, ΔQ / ΔOCV) between the open circuit voltage change amount and the electric amount change amount, and opening of a plurality of batteries having different full charge capacities (SOH). The known correlation (30) between the ratio of the circuit voltage change amount and the electricity amount change amount (ΔOCV / ΔQ, ΔQ / ΔOCV) and the full charge capacity (SOH), and the obtained ratio (ΔOCV / ΔQ, ΔQ /). It can be solved by a method that includes a step (217) of estimating the full charge capacity (SOH) of the battery (1) based on ΔOCV).

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

In the present invention, "time-series" means a plurality of different time points, regardless of whether they are periodic or not. For example, "measurement in time series" means not only measurement performed periodically but also irregular measurement performed at different time points as needed or in response to an external request. include.

In the above method, when the battery (1) is the battery (1) mounted on the vehicle, it is desirable that the two different time points are the time points before and after the vehicle travels. With an in-vehicle battery, the amount of charge and discharge of the battery increases when the vehicle is running. Therefore, the values of the open circuit voltage change amount (ΔOCV) and the electric amount change amount (ΔQ) required for estimating the full charge capacity SOH should be large. It is possible to keep the estimation error small.

Further, in the above method, the step (218) of obtaining the charge rate change amount (ΔSOC) based on the electric energy change amount (ΔQ) and the estimated full charge capacity (SOH) and the battery (1) are almost fully charged. Steps (210, 220) for obtaining the charge rate (SOCo) and open circuit voltage (OCVo) at the time, the amount of change in open circuit voltage (ΔOCV), the amount of change in charge rate (ΔSOC), and the battery (1) are almost full. It may further include a step (221) of estimating the correlation (40) between the open circuit voltage of the battery (1) and the charge rate based on the charge rate (SOCo) and open circuit voltage (OCVo) at the time of charging. desirable.

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

Further, the above-mentioned problems can be solved by an apparatus, a program, and a recording medium on which the program is recorded, which implements the above-mentioned method.

It is a flowchart of the battery state estimation method and a program which concerns on this invention. It is a schematic block diagram of the battery state estimation device which concerns on this invention. It is a figure which shows the known correlation with the ratio of the open circuit voltage change amount and the electric amount change amount, and a full charge capacity. This is an example of the correlation between the estimated open circuit voltage of the battery and the charge rate.

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

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

The voltage measuring 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 unit 12 is connected between the battery 1 and the charging circuit 2 so that the battery 1, the current measuring unit 12 and the load 3 are connected in parallel, and the charge / discharge 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 unit 14, and the measured voltage is sent to the control unit 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 obtains the full charge capacity SOH of the battery 1 and the correlation 40 between the open circuit voltage OCV and the charge rate SOC. Execute and control the processing for estimation. Further, the control unit 14 may be configured to control the timing at which the voltage measurement unit 11 and the current measurement unit 12 perform measurement.

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

FIG. 3 is a graph in which the horizontal axis is the open circuit voltage change amount ΔOCV / ΔQ per unit electric energy change amount and the vertical axis is the full charge capacity SOH. Data 31, 32, 33 ... Obtained from the battery of the above are indicated by dots. As is clear from the figure, there is a correlation between the two, and the linearly approximated correlation 30 is shown by the broken line. The correlation 30 is stored in the storage unit 13 in a format such as a table or an approximate expression, and the control unit 14 reads the stored correlation 30 to obtain the full charge capacity SOH corresponding to the estimated ΔOCV / ΔQ of the battery. be able to. The ratio of the open circuit voltage change amount to the electric amount change amount is the reciprocal of the voltage change amount ΔOCV / ΔQ per unit electric amount change amount, that is, even if the electric amount change amount ΔQ / ΔOCV with respect to the unit voltage change amount. good.

Next, the battery state estimation method 20 according to the embodiment of the present invention will be described with reference to the flowchart 20 of FIG. In the storage unit 13 of the battery state estimation device 10, a program for executing the function shown in the flowchart 20 by the processor of the control unit 14 is recorded.

The state estimation is executed from the stopped state (steps 202, 203) before the vehicle travels (steps 205 to 210) to the stopped state (212 to) after the vehicle travels. Since charging / discharging of the battery 1 is mainly performed when the vehicle is running, the magnitudes of the parameters ΔOCV and ΔQ required in the estimation process can be increased by using the measured values before and after the running. Further, the open circuit voltage OCV, which is another required parameter, can be measured or estimated with stability and high accuracy when the vehicle is stopped when the charge / discharge amount 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 charge rate SOC based on the measurement results at the time of stopping before and after running, it is possible to perform highly accurate estimation with small error. Is possible. Hereinafter, the estimation method 20 will be described according to the processing order.

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

Next, the control unit 14 obtains the open circuit voltage OCV1 from the acquired voltage (step 203). When the charge / discharge amount of the battery 1 continues to be small and the polarization due to charge / discharge is sufficiently eliminated and the voltage is stable, the acquired measured voltage can be regarded as the open circuit voltage OCV1. On the other hand, when the voltage is not stable, the open circuit voltage OCV1 can be obtained by sampling a plurality of voltages in time series and estimating the convergence value of the voltage using an approximate expression. ..

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

When the traveling of the vehicle is determined, the control unit 14 obtains the amount of change in the amount of electricity ΔQ before and after the traveling. Specifically, first, the amount of change in the amount of electricity ΔQ is reset to 0 (step 205). Next, the control unit 14 requests the current measurement unit 12 to measure the charge / discharge current of the battery 1, acquires the magnitude of the current measured by the current measurement unit 12, or causes the current measurement unit 12 to cycle. The latest magnitude of the current being measured is acquired from the storage unit 13 (step 206).

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

Next, the control unit 14 determines whether the battery 1 is in a fully charged state or a state close to a fully charged state (hereinafter, simply referred to as a “fully charged state”) (step 208). For example, when the charge / discharge 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 by the charging resistance obtained by dividing the difference between the charging voltage measured by the voltage measuring unit 11 and the open circuit voltage by the charging current measured by the current measuring unit 12. When it is determined that the battery is fully charged, the control unit 14 obtains the charge rate SOCo based on the charge resistance of the battery 1 (step 210). At this time, the charge rate SOCo may be obtained by adding the discharge resistance at the time of starting the engine and the resistance due to pulse discharge in addition to the charge resistance. Further, the obtained charge rate SOCo value may be finely adjusted in consideration of the influence of temperature, charging voltage and the like. Instead of estimating the charge rate SOCo, the charge rate SOCo may be simply set to 100%.

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

After that, the control unit 14 repeats steps 206 to 210 until the vehicle is stopped (step 211). Finally, the amount of change in the amount of electricity ΔQ is the amount of change in the amount of electricity generated by charging / discharging the battery 1 from the start of traveling of the vehicle to the end of traveling. If it is determined in step 208 that the vehicle is fully charged while the vehicle is running, the final charge rate SOCo is the charge rate at the end of the vehicle running.

When it is determined that the vehicle is stopped, the control unit 14 requests the voltage measuring unit 11 to measure the voltage between the terminals of the battery 1, and acquires the voltage measured by the voltage measuring unit 11 or the voltage measuring unit. The latest voltage measured periodically by 11 is acquired from the storage unit 13 (step 212). Then, the control unit 14 obtains the open circuit voltage OCV2 at the end of traveling from the acquired voltage (step 213). When the charge / discharge amount of the battery 1 continues to be small and the polarization due to charge / discharge is sufficiently eliminated and the voltage is stable, the acquired 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 approximate expression.

Next, the control unit 14 takes the difference between the open circuit voltage OCV1 at the start of running and the open circuit voltage OCV2 at the end of running, so that the amount of change in the open circuit voltage between the start of running and the end of running Obtain ΔOCV (step 214).

Further, the control unit 14 determines whether or not 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 value (step 215). When the absolute value of the amount of change in electric energy ΔQ is equal to or less than a predetermined threshold value, the influence of the error becomes large and there is a concern that the accuracy of the estimation result deteriorates. Returning to steps 202 and 203), the open circuit voltage change amount ΔOCV and the electric amount change amount ΔQ at the time before and after the vehicle travels are obtained.

When 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 value, the corresponding amount of change in the open circuit voltage ΔOCV is also considered to be large, so that high estimation accuracy can be expected. In this case, the control unit 14 obtains the ratio of both from the obtained open circuit voltage change amount ΔOCV and the electric amount change amount ΔQ (step 216). In the present embodiment, since the known correlation 30 stored in the storage unit 13 is the correlation between the voltage change amount per unit electric amount change amount and the fully charged capacity, ΔOCV / ΔQ is obtained as a ratio.

Next, the control unit 14 estimates the full charge capacity SOH by obtaining the full charge capacity SOH corresponding to the obtained ΔOCV / ΔQ with reference to the known correlation 30 stored in the storage unit 13 (). Step 217). When the known correlation 30 stored in the storage unit 13 is the correlation between the amount of change in the amount of electricity and the full charge capacity with respect to the amount of change in the unit voltage, ΔQ / ΔOCV is obtained as a ratio and the corresponding full charge capacity is obtained. SOH can be estimated. The estimated full charge capacity SOH is stored in the storage unit 13 and can be used for controlling the vehicle and the battery 1 as needed.

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

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

Next, the control unit 14 determines whether or not the charge rate SOCo in the fully charged state could be obtained (step 219). When the charge rate SOCo can be obtained, the open circuit voltage OCV2 estimated immediately after the vehicle stops running is set to the closed circuit voltage OCVo in the fully charged state (step 220). Since the charge rate SOCo can be obtained, that is, the case where a full charge determination is made during driving, the charge rate SOCo records the charge rate in the 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 charge rate SOCo.

Therefore, the point 41 on the correlation 40 can be identified from the obtained OCVo and SOCo. By obtaining a straight line from the specified point 41 and the slope 42, the correlation 40 between the open circuit voltage OCV of the battery 1 and the charge rate SOC can be estimated (step 221). The estimated correlation 40 is stored in the storage unit 13 in a desired format such as a table or an approximate expression, and can be used for controlling the vehicle or the battery 1 as needed. On the other hand, in step 219, when the charge rate SOC in the fully charged state is not obtained, the process ends without estimating the correlation 40 between the open circuit voltage OCV and the charge rate SOC.

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

Although the method, apparatus, program for estimating the state of the battery according to the present invention, and the recording medium on which the program is recorded have been described above, the present invention is not limited to the above embodiment, and the present invention is not limited to the above embodiment. Includes all aspects of the concept of the invention and claims. For example, in the above-described embodiment, a method of estimating the state of a lead battery for an in-vehicle use has been described as an example, but a battery for storing electricity generated by solar power generation or the like other than the in-vehicle use, or a lead-acid battery other than the lead-acid battery. It can also be applied to battery state estimation. Further, the known correlation 30 stored in the storage unit may be a correlation by a multivariable function approximation instead of a linear approximation.

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

Claims (7)

A method of estimating the state of the battery
The step of measuring the voltage of the battery and the charge / discharge current in chronological order, respectively.
The step of obtaining the open circuit voltage of the battery at two different time points based on the measured voltage, and
A step of obtaining the amount of change in the open circuit voltage between the two different time points based on the open circuit voltage, and
A step of obtaining the amount of change in the amount of electricity of the battery between the two different time points based on the measured charge / discharge current, and a step of obtaining the amount of change in the amount of electricity of the battery.
The step of obtaining the ratio between the amount of change in the open circuit voltage and the amount of change in the amount of electricity,
Based on the known correlation between the ratio of the open circuit voltage change amount and the electricity amount change amount of a plurality of batteries having different full charge capacities and the full charge capacity, and the obtained ratio, the full charge capacity of the battery is obtained. And the steps to estimate
Including methods. The battery is a battery mounted on a vehicle.
The two different time points are the time points before and after the vehicle travels.
The method according to claim 1. A step of obtaining a charge rate change amount based on the electricity amount change amount and the estimated full charge capacity, and a step of obtaining the charge rate change amount.
Steps to obtain the charge rate and open circuit voltage when the battery is almost fully charged, and
A step of estimating the correlation between the open circuit voltage and the charge rate of the battery based on the open circuit voltage change amount, the charge rate change amount, and the charge rate and the open circuit voltage when the battery is almost fully charged. When,
The method according to claim 1 or 2, further comprising. A device that estimates the state of the battery
A voltage measuring unit that measures the voltage of the battery,
A current measuring unit that measures the charge / discharge current of the battery,
A storage unit that stores a known correlation between the ratio of the open circuit voltage change amount and the electricity amount change amount and the full charge capacity of a plurality of batteries having different full charge capacities.
A voltage measuring unit, a current measuring unit, and a control unit capable of communicating with the storage unit,
With
The control unit
The voltage of the battery measured by the voltage measuring unit and the charge / discharge current of the battery measured by the current measuring unit are acquired in time series, respectively.
Based on the acquired voltage, the open circuit voltage of the battery at two different time points is obtained.
Based on the open circuit voltage, the amount of change in the open circuit voltage between the two different time points is obtained.
Based on the acquired charge / discharge current, the amount of change in the amount of electricity of the battery at the two different time points was obtained.
Obtain the ratio of the open circuit voltage change amount and the electric amount change amount,
It is configured to estimate the full charge capacity of the battery based on the correlation and the calculated ratio.
Device. The control unit further
Based on the amount of change in the amount of electricity and the estimated full charge capacity, the amount of change in the charge rate was obtained.
Based on the acquired voltage, the charge rate and open circuit voltage when the battery is almost fully charged are obtained.
To estimate the correlation between the open circuit voltage and the charge rate of the battery based on the open circuit voltage change amount, the charge rate change amount, and the charge rate and the open circuit voltage when the battery is almost fully charged. The device according to claim 4, which is configured in the above. A voltage measuring unit that measures the voltage of the battery and
A current measuring unit that measures the charge / discharge current of the battery,
A storage unit that stores a known correlation between the ratio of the open circuit voltage change amount and the electricity amount change amount and the full charge capacity of a plurality of batteries having different full charge capacities.
A control unit including a processor and capable of communicating with the voltage measuring unit, the current measuring unit, and the storage unit.
A control program for a device that estimates the state of a battery.
To the processor
The voltage of the battery measured by the voltage measuring unit and the charge / discharge current of the battery measured by the current measuring unit are acquired in time series, respectively.
Based on the acquired voltage, the open circuit voltage of the battery at two different time points is obtained.
Based on the open circuit voltage, the amount of change in the open circuit voltage between the two different time points is obtained.
Based on the acquired charge / discharge current, the amount of change in the amount of electricity of the battery at the two different time points was obtained.
Obtain the ratio of the open circuit voltage change amount and the electric amount change amount,
The function of estimating the full charge capacity of the battery is executed based on the correlation and the obtained ratio.
program. A computer-readable recording medium on which the program according to claim 6 is recorded.

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