JP7377125B2 - Battery control device and battery control method - Google Patents

Description

The present invention relates to a battery control device and a battery control method.

Conventionally, technology has been known to estimate the state of charge (SOC) of lithium-ion rechargeable batteries (LIB), etc. installed in HEVs (Hybrid Electric Vehicles) and EVs (Electric Vehicles). (For example, see Patent Document 1). Note that the above-mentioned SOC is, for example, the charging rate of the battery.

JP2010-283922A

By the way, in the prior art, a reference charging rate that serves as a reference for battery charge/discharge control is set in advance. In conventional technology, for example, when the estimated charging rate of the battery becomes lower than the standard charging rate, the battery is charged by operating a generator connected to the battery to generate electricity, and the charging rate is made to match the standard charging rate. Such charging and discharging control is performed.

However, as batteries deteriorate, their capacity decreases. Therefore, depending on the degree of deterioration of the battery, there is a possibility that the battery may not be able to output the expected power even if the charging rate is the standard charging rate, and there is room for improvement.

The present invention has been made in view of the above, and an object of the present invention is to provide a battery control device and a battery control method that can output desired power even when the battery is deteriorated.

In order to solve the above problems and achieve the objects, the present invention provides a battery control device that includes a deterioration detecting section and a reference charging rate changing section. The deterioration detection section detects the deterioration state of the battery. The reference charging rate changing unit sets a reference charging rate, which is a reference for charge/discharge control of the battery, based on the deterioration state of the battery detected by the deterioration detection unit, so that the amount of remaining charge of the battery is constant. change.

According to the present invention, even if the battery is deteriorated, the desired power can be output.

FIG. 1A is a block diagram illustrating a configuration example of a battery system including a battery control device according to an embodiment. FIG. 1B is a diagram illustrating an overview of a battery control method executed by the battery control device according to the embodiment. FIG. 1C is a diagram illustrating an overview of a battery control method executed by the battery control device according to the embodiment. FIG. 2 is a block diagram showing the configuration of a battery system including the battery control device according to the embodiment. FIG. 3 is a diagram showing an example of an OCV-SOC characteristic curve. FIG. 4 is a diagram showing an example of change information. FIG. 5A is a diagram showing the state of LIB. FIG. 5B is a diagram showing the state of LIB. FIG. 5C is a diagram showing the state of LIB. FIG. 6 is a flowchart showing the processing procedure executed by the battery control device.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a battery control device and a battery control method disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

Further, below, a case will be described as an example in which a battery control device controls a lithium ion secondary battery (hereinafter referred to as LIB) mounted on a vehicle. Note that the object to be controlled by the battery control device is not limited to the LIB installed in a vehicle, but may be a LIB installed in any device.

First, an overview of the battery control method of the battery control device according to the embodiment will be described using FIGS. 1A to 1C. FIG. 1A is a block diagram illustrating a configuration example of a battery system including a battery control device according to an embodiment.

As shown in FIG. 1A, battery system 1 includes a battery pack 10, a generator 11, a starter 12, a lead battery 13, and a host ECU (Electronic Control Unit) 100. The battery pack 10 includes an LIB 14, a first switch 16, a second switch 17, and a battery control device 20.

In this way, the battery system 1 is a two-power supply system including two batteries, the lead battery 13 and the LIB 14. Note that the battery system 1 is not limited to a dual power supply system with duplicated batteries, but may include one battery, or three or more batteries as long as it is a power supply system that includes at least a lithium ion secondary battery. Good too.

The generator 11 is a device that generates electric power using the rotation of the engine E as a power source. Additionally, when the vehicle is decelerating, regenerative braking generates regenerative power. Note that the generator 11 is also called an alternator or a generator.

Further, the generator 11 may generate electric power in accordance with an instruction from the host ECU 100 or the battery control device 20, for example. Then, the lead battery 13 and LIB 14 are charged by, for example, supplying the generated power to the lead battery 13 and LIB 14 .

The starter 12 is a starting device that starts the engine E and includes, for example, an electric motor. Note that in the example shown in FIG. 1A, the battery system 1 is configured to include a starter 12 and a generator 11, but for example, an ISG (Integrated Starter Generator) may be provided instead of the starter 12 and the generator 11. .

Note that the engine E described above may have an idling stop function. The starter 12 can restart the engine E after the engine E is automatically stopped by the idling stop function of the engine E.

The lead battery 13 is a secondary battery using lead as an electrode. Note that the lead battery 13 serves as a main power source for electrical equipment mounted on a vehicle, for example.

The LIB 14 of the battery pack 10 is a secondary battery that is charged or discharged, and serves as an auxiliary power source for the lead battery 13, for example. Note that an iron-based LIB can be used as the LIB 14, but is not limited thereto. Furthermore, the LIB 14 is an example of a vehicle battery.

The first switch 16 and the second switch 17 are switches (relays) that control shorting and opening of the circuit. The first switch 16 is connected between the lead battery 13 and the generator 11 (or starter 12). The second switch 17 is connected between the LIB 14 and the generator 11 (or starter 12). Opening and closing of the first switch 16 and the second switch 17 are controlled by the above-described host ECU 100.

The host ECU 100 is a host ECU of the battery pack 10, and acquires vehicle conditions and the like as needed, and controls the battery pack 10 according to the vehicle conditions and the like. For example, the host ECU 100 acquires information regarding the vehicle status, the status of the LIB 14, the status of the lead battery 13, and the like. Note that the information regarding the state of the LIB 14 includes, for example, the state of charge (SOC) of the LIB 14 estimated by the battery control device 20 and information on a reference charging rate to be described later. The above-mentioned SOC is, for example, the charging rate (charge amount) of the LIB 14.

Then, the host ECU 100 opens and closes the first switch 16 and the second switch 17 based on the vehicle condition, the state of the LIB 14 (for example, SOC), the state of the lead battery 13, etc., and charges and discharges the lead battery 13 and LIB 14. Control. Furthermore, the host ECU 100 controls the operation of various electrical devices such as the generator 11, the starter 12, and auxiliary equipment (not shown) depending on the vehicle situation and the like.

As described above, the battery control device 20 executes the process of estimating the SOC of the LIB 14, and notifies the upper ECU 100 of information on the estimated SOC.

Further, the battery control device 20 can also perform charging and discharging control of the LIB 14. Here, a battery control method including charge/discharge control by the battery control device 20 will be described in detail with reference to FIGS. 1B and 1C. FIG. 1B and FIG. 1C are diagrams showing an overview of a battery control method executed by the battery control device 20 according to the embodiment.

First, as shown in FIG. 1B, the battery control device 20 performs charging/discharging control based on a reference charging rate. For example, the battery control device 20 can control charging and discharging of the LIB 14 so that the SOC of the LIB 14 matches the reference charging rate.

The reference charging rate is a charging rate that serves as a reference for charge/discharge control of the LIB 14, and is set in advance. The reference charging rate is set, for example, to a value that allows the LIB 14 to output the desired power that allows the starter 12 to restart the engine E or to enable other auxiliary equipment to operate while the engine E is automatically stopped. Note that the reference charging rate is the center of control in charging and discharging control, and can also be said to be the target charging rate of the SOC.

Therefore, for example, when the SOC decreases and becomes lower than the standard charging rate (hereinafter sometimes referred to as "standard SOC"), the battery control device 20 rotates the engine E in order to ensure the desired output of electric power. An instruction to cause the generator 11 (see FIG. 1A) to generate electricity is output to the engine E and the generator 11. According to this instruction, the generator 11 generates power, and the generated power is charged to the LIB 14, so that the SOC increases to a value that matches or exceeds the reference SOC, and it is possible to secure the desired power output in the LIB 14. become.

Note that in the example of FIG. 1B, the reference SOC is set to 30%. Furthermore, if the capacity of the LIB 14 when the SOC is 100% is "10 Ah", the remaining charge amount of the LIB 14 is "3 Ah" when the SOC is 30% of the reference SOC. Further, FIG. 1B shows the charging state when the deterioration rate of the LIB 14 is 0%, that is, the LIB 14 is not deteriorated.

For convenience of understanding, specific numerical values such as the reference SOC, the capacity of the LIB 14, and the deterioration rate will be cited, but these numerical values are merely examples and are not limiting.

By the way, the capacity of the LIB 14 decreases as it deteriorates. Therefore, depending on the degree of deterioration of the LIB 14, there is a possibility that the LIB 14 may not be able to output the expected power even if the SOC is the reference SOC.

This will be explained in detail with reference to FIG. 1C. The example in FIG. 1C shows a charging state when the deterioration rate of the LIB 14 is 20%. If the deterioration rate is 20%, in other words, if the performance of the LIB 14 becomes 80% due to deterioration, the capacity of the LIB 14 will be "8 Ah" even if the SOC is 100%.

Therefore, even if LIB14 charge/discharge control is performed so that the SOC maintains 30% of the reference SOC, the remaining charge amount of LIB14 when the SOC is 30% decreases from "3Ah" to "2.4Ah". However, there was a possibility that the LIB 14 would not be able to output the expected power.

Therefore, in the battery control device 20 according to the present embodiment, the reference SOC is changed depending on the deterioration of the LIB 14. Thereby, the battery control device 20 can output the desired power even if the LIB 14 has deteriorated.

Specifically, the battery control device 20 detects the deterioration state of the LIB 14. Here, the deterioration rate of the LIB 14 is detected as the deterioration state of the LIB 14. Detection of the deterioration rate of the LIB 14 will be described later.

Then, the battery control device 20 changes the reference SOC based on the detected deterioration state of the LIB 14 (deterioration rate of the LIB 14) so that the remaining charge amount of the LIB 14 becomes constant. Specifically, the standard SOC was changed from "30%" to "37.5%." That is, since the capacity of the LIB 14 has decreased (degraded) to 80%, the standard SOC 30% before the change is divided by 0.8 to change the standard SOC to 37.5%.

As a result, if the battery control device 20 performs charging/discharging control so that the SOC becomes 37.5%, which is the standard SOC after the change, the remaining charge amount of the LIB 14 will be reduced to 3Ah, which is the same as before deterioration. This allows the LIB 14 to output the desired power.

In this way, the battery control device 20 changes the reference SOC based on the deterioration rate of the LIB 14 so that the amount of remaining charge of the LIB 14 becomes constant with the amount of charge before deterioration. As a result, in this embodiment, even if the LIB 14 has deteriorated, it is possible to output the desired power.

Next, with reference to FIG. 2, the configuration of the battery system 1 including the battery control device 20 according to the embodiment will be described in detail. FIG. 2 is a block diagram showing the configuration of the battery system 1 including the battery control device 20 according to the embodiment. Note that in FIG. 2, only the components necessary to explain the features of this embodiment are shown as functional blocks, and descriptions of general components are omitted.

In other words, each component illustrated in FIG. 2 is functionally conceptual, and does not necessarily need to be physically configured as illustrated. For example, the specific form of distribution and integration of each functional block is not limited to what is shown in the diagram, and all or part of it can be functionally or physically distributed in arbitrary units depending on various loads and usage conditions. - Can be configured in an integrated manner.

As shown in FIG. 2, the battery system 1 includes the above-described LIB 14, a battery control device 20, a host ECU 100, a current sensor 61, a voltage sensor 62, a temperature sensor 63, various electrical devices 70, and a first , second switches 16 and 17.

In FIG. 2, for simplicity of illustration, the generator 11 and starter 12 described above, as well as auxiliary equipment (loads) mounted on the vehicle, such as a navigation device, an audio system, and an air conditioner, are shown as one electrical device 70. Shown in blocks. Further, in FIG. 2, the first switch 16 and the second switch 17 are shown as one block.

The current sensor 61 is a sensor that measures the charging and discharging current of the LIB 14. The voltage sensor 62 is a sensor that measures the battery voltage of the LIB 14. The temperature sensor 63 is a sensor that measures the battery temperature of the LIB 14. Current sensor 61, voltage sensor 62, and temperature sensor 63 each output a signal indicating a measurement result to battery control device 20.

The battery control device 20 includes a control section 30 and a storage section 40. The control unit 30 includes a detection unit 31, an estimation unit 32, a charge/discharge control unit 33, a deterioration detection unit 34, a reference charging rate change unit 35, an estimable area change unit 36, and a prohibition unit 37. .

The control unit 30 includes, for example, a computer and various circuits having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), an input/output port, and the like.

For example, the CPU of the computer reads out and executes a program stored in the ROM, thereby controlling the detection unit 31, estimation unit 32, charge/discharge control unit 33, deterioration detection unit 34, and reference charging rate change unit 35 of the control unit 30. , functions as an estimable area changing section 36 and a prohibition section 37.

In addition, at least a part or all of the detection unit 31, estimation unit 32, charge/discharge control unit 33, deterioration detection unit 34, reference charging rate change unit 35, estimable area change unit 36, and prohibition unit 37 of the control unit 30 It is also possible to configure it with hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

Furthermore, the storage unit 40 is, for example, a storage device such as a data flash, a nonvolatile memory, or a register. The storage unit 40 stores OCV-SOC map information 41 and change information 42.

The OCV-SOC map information 41 includes information regarding charging characteristics indicating the relationship between the open circuit voltage (OCV) of the LIB 14 and the SOC, and specifically includes information regarding the OCV-SOC characteristic curve. Note that the OCV-SOC characteristic curve is an example of a charging characteristic indicating the relationship between open circuit voltage (OCV) and SOC. Furthermore, the estimation unit 32, which will be described later, can also estimate the SOC from the OCV of the LIB 14 using the OCV-SOC characteristic curve.

FIG. 3 is a diagram showing an example of an OCV-SOC characteristic curve. As shown in FIG. 3, the OCV-SOC characteristic curve is a function derived from the observed values of SOC and OCV when the LIB 14 is charged and discharged, for example, by the method of least squares.

Here, the OCV-SOC characteristic curve of iron-based LIB14 will be explained in detail. As shown in FIG. 3, in the OCV-SOC characteristic curve, when the SOC changes in a relatively low region E1 (for example, between 0% and a predetermined value Aa), the OCV also changes in a region D1 (between a predetermined value Va and a predetermined value Aa). Vb) shows characteristics that change relatively significantly. Similarly, when SOC changes in a relatively high region E3 (between predetermined value Ab and 100%), OCV also has a characteristic that changes relatively greatly in region D3 (between predetermined value Vc and predetermined value Vd). show. Therefore, even if, for example, there is a slight detection error in the OCV in the region D1 or the region D3, the effect on the estimated SOC is small and the SOC can be estimated with relatively high accuracy.

On the other hand, when the SOC changes in a region E2 (between the predetermined value Aa and the predetermined value Ab) between the region E1 and the region E3, the OCV changes in the region D2 (between the predetermined value Vb and the predetermined value Vc) shows characteristics that change relatively small. In this way, the OCV-SOC characteristic curve has a region D2 where the change in OCV with respect to the change in SOC is gradual and flat. Therefore, for example, if there is a slight detection error in the OCV in the region D2, the SOC will change significantly, making it difficult to estimate the SOC with high accuracy.

That is, in the OCV-SOC characteristic curve of iron-based LIB14, if OCV is in region D1 or region D3, it is possible to estimate SOC, and if OCV is in region D2, SOC can be estimated from the viewpoint of accuracy. Difficult to estimate.

Therefore, the estimation unit 32, which will be described later, determines that the state of the LIB 14 is such that the SOC can be estimated using the OCV, for example, when the OCV of the LIB 14 at startup is in a predetermined region such as region D1 or region D3. do. Furthermore, hereinafter, predetermined regions such as the region D1 and the region D3 may be referred to as regions in which the SOC can be estimated based on the OCV-SOC characteristic curve (estimable regions).

Furthermore, the OCV-SOC characteristic curve may also change depending on the state of deterioration of the LIB 14. Therefore, in this embodiment, the region in which the SOC can be estimated is changed in accordance with changes in the OCV-SOC characteristic curve due to deterioration of the LIB 14. In addition, in this embodiment, for convenience of understanding, a case where only the estimable region D1 is changed depending on the deterioration state of the LIB 14 will be exemplified. For example, it is assumed that the upper limit (here, the predetermined value Vb) of the estimable region D1 decreases as the LIB 14 deteriorates. Therefore, in this embodiment as well, as the upper limit of the estimable region D1 decreases due to deterioration, the charging rate (SOC, here the predetermined value Aa) corresponding to the upper limit of the estimable region D1 is changed to decrease. I made it.

Further, in order to facilitate understanding, the following description may include specific numerical values, such as the predetermined value Aa being 40% and the predetermined value Ab being 85%.

Returning to the explanation of FIG. 2, the change information 42 is information regarding various numerical values that are changed depending on the deterioration state of the LIB 14. Here, the change information 42 will be explained with reference to FIG. 4.

FIG. 4 is a diagram showing an example of the change information 42. As shown in FIG. 4, the change information 42 includes information regarding a "reference SOC," "SOC corresponding to the upper limit of the estimable region D1," and "restartable SOC."

The "reference SOC" of the change information 42 is information regarding the reference SOC that is changed due to deterioration of the LIB 14, as described above. For example, the "reference SOC" of the change information 42 includes information indicating that the reference SOC is changed to increase as the deterioration state of the LIB 14 progresses. Specifically, the "reference SOC" includes information indicating that the reference SOC is changed to increase when the deterioration rate of the LIB 14 increases.

The "SOC corresponding to the upper limit of the estimable region D1" of the change information 42 is information regarding the estimable region D1 that is changed in accordance with changes in the OCV-SOC characteristic curve due to deterioration of the LIB 14, as described above. For example, the "SOC corresponding to the upper limit of the estimable region D1" of the change information 42 includes the SOC corresponding to the upper limit of the estimable region D1 ( Refer to the predetermined value Aa in FIG. 3 (hereinafter sometimes referred to as "estimateable area corresponding SOC").

The “restartable SOC” of the change information 42 is information on an SOC that can supply the power necessary for restarting the engine E by the starter 12. That is, when the SOC of the LIB 14 is equal to or higher than the "restartable SOC", the starter 12 is supplied with electric power from the LIB 14 and can restart the engine E. Conversely, if the SOC of the LIB 14 is less than the "restartable SOC", the starter 12 cannot restart the engine E due to insufficient power from the LIB 14.

The “restartable SOC” of the change information 42 is information for changing such a restartable SOC. For example, the "restartable SOC" of the change information 42 includes information indicating that the restartable SOC is changed to increase as the deterioration state of the LIB 14 progresses. Specifically, the "restartable SOC" includes information indicating that when the deterioration rate of the LIB 14 increases, the restartable SOC is changed to increase.

Note that the restartable SOC is an example of a charging rate at which a predetermined power can be output. Moreover, the electric power that can restart the engine E is an example of predetermined electric power.

Here, the reference SOC, the SOC corresponding to the estimable region, and the restartable SOC described above will be explained in more detail with reference to FIG. 5A. FIG. 5A is a diagram showing the state of the LIB 14 when the deterioration rate is 0%. Note that in FIG. 5A and FIGS. 5B and 5C, which will be described later, the state of the LIB 14 is shown superimposed on the OCV-SOC characteristic curve for ease of understanding.

As shown in FIGS. 5A and 4, when the deterioration rate is 0%, the reference SOC (indicated by code A1) is "30%", the SOC corresponding to the estimable area (indicated by code B1) is "40%", and the The startable SOC (indicated by code C1) is set to "20%".

In the example of FIG. 5A, when the deterioration rate is 0%, the capacity of LIB14 at 100% SOC is "10Ah", so the remaining charge amount of LIB14 corresponding to 30% of the reference SOC is "3Ah", The remaining charge amount of the LIB 14, which corresponds to 20% of the startable SOC, is "2Ah".

Returning to the explanation of FIG. 2, the detection unit 31 of the control unit 30 detects the current (current value) of the LIB 14 based on the signal input from the current sensor 61. Furthermore, the detection unit 31 detects the voltage (voltage value) of the LIB 14 based on a signal input from the voltage sensor 62. Note that the detection unit 31 can detect the above-mentioned OCV as the voltage of the LIB 14. The detection unit 31 detects the battery temperature of the LIB 14 based on a signal input from the temperature sensor 63. The detection unit 31 outputs signals indicating the detected current, voltage, and battery temperature to the estimation unit 32, the charge/discharge control unit 33, the deterioration detection unit 34, and the like.

The estimation unit 32 estimates the SOC using a current integration method. For example, the estimation unit 32 calculates the initial SOC based on the OCV of the LIB 14 at startup and the OCV-SOC characteristic curve of the OCV-SOC map information 41 (see FIG. 3).

Then, the estimation unit 32 estimates the SOC using the calculated initial SOC as an initial value. Note that, as an arithmetic expression for the current integration method, for example, "SOC(k+1)=SOC(k)+current integral/FCC" can be used. Here, k is a discretized time index, in other words, the number of steps. Further, FCC is a constant called full charge capacity.

Furthermore, the estimation unit 32 can update (correct) the SOC estimated by the current integration method to the SOC estimated based on the OCV and the OCV-SOC characteristic curve (see FIG. 3).

That is, in estimating SOC using the current integration method described above, measurement errors of the current sensor 61 are accumulated, and the accumulation of such measurement errors may cause errors in SOC estimation, leading to a decrease in SOC estimation accuracy. There is. Therefore, the estimation unit 32 may update the SOC estimated by the current integration method to the SOC estimated by the OCV-SOC characteristic curve.

For example, the estimation unit 32 determines whether the OCV of the LIB 14 at startup is in a region where the SOC can be estimated using the OCV-SOC characteristic curve. If it is determined that the SOC of the OCV can be estimated using the OCV-SOC characteristic curve, the estimation unit 32 updates the SOC estimated by the current integration method to the SOC estimated by the OCV-SOC characteristic curve. good. The estimation unit 32 outputs a signal indicating the estimated or updated SOC to the charge/discharge control unit 33 or the like.

In this way, the estimation unit 32 updates (corrects) the SOC estimated by the current integration method to the SOC estimated using the OCV, so that the estimation accuracy of the SOC is improved by the accumulation of measurement errors of the current sensor 61. It is possible to suppress the decrease due to

The charge/discharge control section 33 performs charge/discharge control based on the SOC and the reference SOC. For example, the charging/discharging control unit 33 can control charging/discharging of the LIB 14 so that the SOC matches the reference SOC.

For example, when the SOC becomes lower than the reference SOC, the charge/discharge control unit 33 charges the LIB 14 by rotating the engine E and causing the generator 11 to generate electricity. Further, when the SOC becomes higher than the reference SOC, the charge/discharge control unit 33 causes the LIB 14 to supply power to various electrical devices 70 to discharge the LIB 14. In this manner, the charge/discharge control unit 33 performs charge/discharge control to match the SOC of the LIB 14 with the reference SOC.

The deterioration detection unit 34 detects the deterioration state of the LIB 14. Specifically, the deterioration detection unit 34 detects the deterioration rate of the LIB 14. For example, the deterioration detection unit 34 can detect the deterioration rate of the LIB 14 based on the internal resistance of the LIB 14. That is, the internal resistance of the LIB 14 increases as the LIB deteriorates. Therefore, the deterioration detection unit 34 calculates an internal resistance value based on the detected current and voltage of the LIB 14, and detects a deterioration rate that increases as the calculated internal resistance value increases. The deterioration detection section 34 outputs a signal indicating the detected deterioration rate to the reference charging rate change section 35 and the estimable region change section 36.

In addition, although the deterioration detection part 34 detected the deterioration rate based on internal resistance in the above, it is not limited to this. That is, for example, the deterioration detection unit 34 may detect the deterioration rate based on various usage environmental conditions of the LIB 14 (for example, usage time, average battery temperature, etc.), or may detect it using other methods.

The reference charging rate changing unit 35 changes the reference SOC based on the deterioration rate of the LIB 14 (the deterioration state of the LIB 14) so that the remaining charge amount of the LIB 14 becomes constant. For example, the reference charging rate changing unit 35 changes the reference SOC based on the deterioration rate detected by the deterioration detecting unit 34 and the change information 42 (see FIG. 4) in the storage unit 40.

Here, with reference to FIGS. 5B and 5C, the process of changing the reference SOC by the reference charging rate changing unit 35 will be described. FIG. 5B is a diagram showing the state of the LIB 14 when the deterioration rate is 20%, and FIG. 5C is a diagram showing the state of the LIB 14 when the deterioration rate is 50%.

As shown in FIG. 5B, when the deterioration rate is 20%, the capacity of the LIB 14 when the SOC is 100% decreases to "8 Ah". Therefore, the reference charging rate changing unit 35 changes the reference SOC (indicated by the symbol A2) from "30%" to "37.5%" so that the remaining charge amount of the LIB 14 becomes constant.

As a result, if the charging/discharging control unit 33 performs charging/discharging control so that the SOC becomes 37.5%, which is the standard SOC after the change, the remaining charge amount of the LIB 14 will be the same as before deterioration. 3Ah", and the LIB 14 can output the desired power.

Further, as shown in FIG. 5C, when the deterioration rate is 50%, the capacity of the LIB 14 when the SOC is 100% decreases to "5 Ah". Therefore, the reference charging rate changing unit 35 changes the reference SOC (indicated by the symbol A3) from "30%" to "60%" so that the remaining charge amount of the LIB 14 becomes constant.

As a result, if the charge/discharge control unit 33 performs charge/discharge control so that the SOC becomes 60%, which is the standard SOC after the change, the remaining charge amount of the LIB 14 will be reduced to 3Ah, which is the same as before deterioration. This allows the LIB 14 to output the desired power.

In addition to changing the reference SOC, the reference charging rate changing unit 35 may change the restartable SOC based on the deterioration rate. For example, the reference charging rate changing unit 35 changes the restartable SOC based on the deterioration rate and the change information 42 (see FIG. 4).

As shown in FIG. 5B, when the deterioration rate is 20%, the reference charging rate changing unit 35 changes the restartable SOC (indicated by code C2) from "20%" to "25%." Further, as shown in FIG. 5C, when the deterioration rate is 50%, the reference charging rate changing unit 35 changes the restartable SOC (indicated by code C3) from "20%" to "40%". did.

Thereby, the charge/discharge control unit 33 described above can set the remaining charge amount of the LIB 14 whose SOC corresponds to the restartable SOC after the change to "2Ah", which is the same as before deterioration.

Returning to the explanation of FIG. 2, the estimable region changing unit 36 changes the SOC estimable region D1 (see FIG. 3) based on the deterioration state of the LIB 14. As a result, in this embodiment, the estimable region D1 can be changed to a region that conforms to the OCV-SOC characteristic curve that changes depending on the deterioration state of the LIB 14.

For example, the estimable area changing unit 36 changes the estimable area D1 based on the deterioration rate of the LIB 14 and the change information 42 (see FIG. 4) in the storage unit 40. Specifically, the estimable area changing unit 36 changes the estimable area D1, The SOC (SOC corresponding to the estimable region) corresponding to (predetermined value Vb) is changed. Specifically, the estimable area changing unit 36 changes the estimable area corresponding SOC to decrease as the deterioration rate of the LIB 14 increases.

This will be explained with reference to FIGS. 5B and 5C. First, as shown in FIG. 5B, when the deterioration rate is 20%, the estimable area changing unit 36 changes the estimable area corresponding SOC (indicated by code B2). Changed from "40%" to "32%". Note that the upper limit of the estimable region D1 here is a predetermined value Vb2 that is lower than the predetermined value Vb. Further, as shown in FIG. 5C, when the deterioration rate is 50%, the estimable area changing unit 36 changes the estimable area corresponding SOC (indicated by code B3) from "40%" to "20%". I made it. Note that the upper limit of the estimable region D1 here is a predetermined value Vb3 lower than the predetermined value Vb2.

As a result, in this embodiment, the SOC (SOC corresponding to the estimable area) corresponding to the upper limit of the estimable area D1 can be set to a value that corresponds to the deterioration state of the LIB 14.

Here, as mentioned above, in the OCV-SOC characteristic curve of iron-based LIB14, there is a region D2 in which the change in OCV with respect to a change in SOC is gentle and flat, and when OCV is in region D2, the accuracy It is difficult to estimate the SOC. Note that in FIG. 5B and the like, dots are attached to the area of the SOC corresponding to area D2.

Further, as shown in FIGS. 5B and 5C, when the reference SOC is changed due to deterioration of the LIB 14, the changed reference SOC may fall into the SOC region corresponding to the region D2. In this case, since the LIB 14 is controlled to charge and discharge so that the SOC matches the changed reference SOC, the OCV is unlikely to fall within the estimable region D1, and the SOC may not be updated (corrected).

Therefore, the reference charging rate changing unit 35 according to the present embodiment changes the reference SOC at a predetermined timing so that the OCV falls into the region D1 in which the SOC can be estimated based on the OCV-SOC characteristic curve.

Note that the above-mentioned predetermined timing is, for example, when the estimation period indicating the period during which the SOC was estimated by the current integration method has elapsed, or when the LIB 14 is started, but is not limited thereto. Further, the predetermined period is set to a value that may reduce the accuracy of SOC estimation due to accumulation of measurement errors of the current sensor 61, for example, but is not limited to this.

For example, in FIG. 5B, the reference charging rate changing unit 35 changes the reference SOC (indicated by the symbol A2a) to be equal to or less than the estimable region corresponding SOC: B2. As a result, since the LIB 14 is controlled to charge and discharge so that the SOC matches the changed reference SOC: A2a, the OCV becomes the estimable region D1. At that time, the estimation unit 32 updates (corrects) the SOC estimated by the current integration method to the SOC estimated using the OCV. As a result, in the present embodiment, it is possible to suppress the deterioration of the SOC estimation accuracy due to accumulation of measurement errors of the current sensor 61 or the like.

Further, when changing the reference SOC to the estimable region D1, the reference charging rate changing unit 35 may set the reference SOC to be less than or equal to the estimable region corresponding SOC: B2 and greater than or equal to the restartable SOC: C2. As a result, even when LIB 14 is controlled to charge and discharge so that the SOC matches the changed standard SOC, the SOC is unlikely to fall below the "restartable SOC" and the engine E can be restarted. I can do it.

However, as shown in FIG. 5C, depending on the deterioration state of the LIB 14, if the reference charging rate changing unit 35 changes the reference SOC: A3a to the estimable region D1, which is less than or equal to the estimable region corresponding SOC: B3, the The reference SOC: A3a may be lower than the restartable SOC: C3.

In such a case, the SOC of the LIB 14 may become less than the restartable SOC, and the starter 12 may not be able to restart the engine E due to insufficient power from the LIB 14.

Therefore, the prohibition unit 37 shown in FIG. 2 prohibits execution of the predetermined control using the power from the LIB 14 when the changed standard SOC: A3a becomes less than the restartable SOC: C3. For example, the prohibition unit 37 prohibits the execution of idling stop control that automatically stops and automatically restarts the engine E mounted on the vehicle.

Specifically, the prohibition unit 37 outputs a prohibition signal that prohibits automatic stopping of the engine E in the idling stop control to the host ECU 100. The host ECU 100 does not automatically stop the engine E when the prohibition signal is input.

As a result, in this embodiment, even if the changed standard SOC: A3a becomes less than the restartable SOC: C3, the engine E is not automatically stopped, so the engine E cannot be restarted. There is no possibility that you will be unable to do so.

In addition, although idling stop control was used as an example of the predetermined control in the above, the predetermined control is not limited to this, and other controls such as power supply control to various electric devices 70 including auxiliary machines may be used.

Then, the reference charging rate changing unit 35 changes the reference SOC so that the OCV is in the estimable region D1, and after the SOC is updated (corrected), the changed reference SOC is returned to the position before the change. .

Next, the processing procedure executed by the battery control device 20 according to the embodiment will be described using FIG. 6. FIG. 6 is a flowchart showing the processing procedure executed by the battery control device 20.

As shown in FIG. 6, the control unit 30 of the battery control device 20 first detects the charging rate of the LIB 14 (step S10). Next, the control unit 30 changes the reference SOC, the estimable region D1 (more precisely, the SOC corresponding to the upper limit of the estimable region D1), and the restartable SOC based on the deterioration rate (step S11).

Next, the control unit 30 estimates the SOC using a current integration method (step S12). Next, the control unit 30 determines whether it is time to update the SOC (step S13). The update timing may be when the LIB 14 is activated or when a predetermined period of time has elapsed during which the SOC was estimated using the current integration method, but is not limited thereto.

If it is determined that it is not the SOC update timing (step S13, No), the control unit 30 skips the subsequent processing. On the other hand, if it is determined that it is time to update the SOC (Step S13, Yes), the control unit 30 determines whether or not it is possible to estimate the SOC using the OCV (Step S14), in other words. For example, it is determined whether the OCV is an estimable area such as area D1 or area D3.

When it is determined that the SOC is not in a state in which it is possible to estimate the SOC using the OCV (Step S14, No), the control unit 30 changes the reference SOC so that the OCV is in the estimable region D1 (Step S15).

Next, the control unit 30 determines whether the changed reference SOC is less than the restartable SOC (step S16). If it is determined that the changed reference SOC is less than the restartable SOC (Step S16, Yes), the control unit 30 prohibits execution of the idling stop control (Step S17). If it is determined that the changed reference SOC is not less than the restartable SOC (No in step S16), the control unit 30 skips the process in step S17.

Next, the control unit 30 executes an update process to update the SOC estimated by the current integration method (step S18). Further, if it is determined that the SOC can be estimated using the OCV (step S14, Yes), the control unit 30 proceeds to step S18 and executes the SOC update process.

Note that in step S18, for example, if the reference SOC has been changed in step S15 so that the OCV is in the estimable region D1, after the SOC is updated, a process of returning the reference SOC to the position before the change is also executed.

As described above, the battery control device 20 according to the embodiment includes the deterioration detecting section 34 and the reference charging rate changing section 35. The deterioration detection unit 34 detects the deterioration state of the LIB 14 (an example of a battery). The reference charging rate changing unit 35 sets a reference charging rate (standard SOC). Thereby, even if the LIB 14 has deteriorated, it is possible to output the desired power.

Further advantages and modifications can be easily deduced by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1 Battery system 14 LIB
20 Battery control device 34 Deterioration detection unit 35 Standard charging rate changing unit 36 Estimable area changing unit 37 Prohibition unit

Claims (6)

a deterioration detection unit that detects the deterioration state of the battery;
Based on the deterioration state of the battery detected by the deterioration detection unit, the worse the deterioration state is, the charging rate of the battery becomes a target for charging/discharging control of the battery, and when the charging rate becomes lower, charging starts. and a target charging rate changing unit that changes the target charging rate to a large value so that the remaining charge amount of the battery becomes constant when the target charging rate is reached . a detection unit that detects the current of the battery and the open circuit voltage of the battery;
The charging rate of the battery is estimated by a current integration method based on the current detected by the detecting section, and the open circuit voltage detected by the detecting section is calculated based on the relationship between the open circuit voltage and the charging rate. If the charging rate is in a region where it is possible to estimate the charging rate based on the charging characteristic, the charging rate estimated by the current integration method is updated to the charging rate estimated based on the open circuit voltage and the charging characteristic. It includes an estimator and
The target charging rate changing unit includes:
The battery control device according to claim 1, wherein the target charging rate is changed at a predetermined timing so that the open circuit voltage falls within a range in which the charging rate can be estimated based on the charging characteristics. The battery according to claim 2, further comprising: an estimable area changing unit that changes a corresponding charging rate that defines an estimable area to decrease as a deterioration rate indicating a deterioration state of the battery increases. Control device. The target charging rate is changed by the target charging rate changing unit so that the open circuit voltage is in a region where the charging rate can be estimated based on the charging characteristics, and the target charging rate after the change is a predetermined value for the battery. 4. The battery control device according to claim 2, further comprising: a prohibition unit that prohibits execution of a predetermined control using power from the battery when the charging rate becomes lower than the charging rate at which power can be outputted. The battery is a vehicle battery,
The battery control device according to claim 4, wherein the predetermined control is an idling stop control that automatically stops and automatically restarts an engine installed in the vehicle. a deterioration detection step of detecting a deterioration state of the battery;
Based on the deterioration state of the battery detected in the deterioration detection step, the worse the deterioration state is, the charging rate of the battery becomes a target for charging/discharging control of the battery, and when the charging rate becomes lower, charging starts. a target charging rate changing step of changing the target charging rate to a large value so that the remaining charge amount of the battery becomes constant when the target charging rate is reached .

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