JP2021141722A - Battery control device and battery control method - Google Patents

Abstract

To improve the estimation accuracy of the battery charge rate.SOLUTION: In a battery control device, a first battery and a second battery are connected as a power source. The battery control device includes a detection unit, an estimation unit, and a power supply control unit. The detection unit detects the current of the first battery and the open circuit voltage of the first battery. The estimation unit estimates the charge rate of the first battery on the basis of the current detected by the detection unit by the current integration method, and updates the charge rate estimated by the current integration method to the charge rate estimated on the basis of the open circuit voltage and the charge characteristics, when the state of the first battery can estimate the charge rate on the basis of the open circuit voltage detected by the detection unit and the charge characteristics indicating the relationship between the open circuit voltage and the charge rate. The power supply control unit cuts off the connection of the first battery as a power source, when the detection unit detects the open circuit voltage at the time of updating the charge rate by the estimation unit.SELECTED DRAWING: Figure 1

Description

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

Conventionally, a technique for estimating the state of charge (SOC) of a lithium ion secondary battery (LIB: Lithium-Ion rechargeable battery) mounted on a HEV (Hybrid Electric Vehicle) or EV (Electric Vehicle) has been known. (See, for example, Patent Document 1). In the prior art, the SOC is estimated by the current integration method.

Japanese Unexamined Patent Publication No. 2011-106952

As a method for estimating SOC, in addition to the above-mentioned current integration method, there is a method using a voltage when the lithium ion secondary battery is not charged or discharged, that is, an open circuit voltage. Further, the SOC is estimated by a battery control device, and a lithium ion secondary battery and another secondary battery such as a lead battery may be connected to the battery control device as a power source.

However, in the battery control device configured as described above, there is a risk that the SOC estimation accuracy may decrease. For example, when the battery control device is supplied with power from the lithium ion secondary battery and the battery control device attempts to detect the open circuit voltage, the lithium ion secondary battery is discharged by the power supply. (That is, the closed circuit voltage) is erroneously detected as the open circuit voltage. Therefore, in the battery control device, the SOC is estimated by using an erroneous open circuit voltage, and there is a possibility that the estimation accuracy of the SOC may be lowered.

As described above, there is room for improvement in the prior art in terms of improving the SOC estimation accuracy. The SOC described above is, for example, the charge rate of the battery.

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 capable of improving the estimation accuracy of the battery charge rate.

In order to solve the above problems and achieve the object, the present invention is a battery control device in which a first battery and a second battery are connected as a power source, and a detection unit, an estimation unit, and a power supply control unit are provided. Be prepared. The detection unit detects the current of the first battery and the open circuit voltage of the first battery. The estimation unit estimates the charge rate of the first battery by a current integration method based on the current detected by the detection unit, and the open circuit in which the state of the first battery is detected by the detection unit. When the charge rate can be estimated based on the voltage and the charge characteristic indicating the relationship between the open circuit voltage and the charge rate, the charge rate estimated by the current integration method is used as the open circuit voltage. And update to the charge rate estimated based on the charge characteristics. When the detection unit detects the open circuit voltage when the estimation unit updates the charge rate, the power supply control unit cuts off the connection of the first battery as a power source.

According to the present invention, the accuracy of estimating the charge rate of the battery can be improved.

FIG. 1 is a diagram illustrating an outline of a battery control method of the battery control device according to the embodiment. FIG. 2 is a block diagram showing a 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 flowchart showing a processing procedure executed by the battery control device. FIG. 5 is a diagram illustrating an OCV-SOC characteristic curve. FIG. 6 is a diagram showing the voltage of the LIB from before the engine is stopped until the polarization is eliminated. FIG. 7 is a flowchart showing a processing procedure executed by the battery control device according to the modified example.

Hereinafter, embodiments of the battery control device and the battery control method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

Further, in the following, the case where the battery control device estimates the charge rate of the lithium ion secondary battery (lithium ion battery; hereinafter referred to as LIB) mounted on the vehicle, that is, the SOC of the LIB will be described as an example. do. The target of estimation by the battery control device is not limited to the LIB mounted on the vehicle, and may be the LIB mounted on any device.

First, the outline of the battery control method of the battery control device according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an outline of a battery control method of the battery control device according to the embodiment. Note that FIG. 1 is also a block diagram showing a configuration example of a battery system including a battery control device.

As shown in FIG. 1, the 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 a LIB 14, a first switch 15, a second switch 16, a lead battery changeover switch 17, a LIB changeover switch 18, and a battery control device 20. The LIB 14 is an example of the first battery, and the lead battery 13 is an example of the second battery.

As described above, the battery system 1 is a dual power supply system including two batteries, a lead battery 13 and a LIB 14. The battery system 1 is not limited to a dual power supply system in which batteries are duplicated, and at least a lithium ion secondary battery (first battery) and a secondary battery (second battery) different from the lithium ion secondary battery. Batteries. Here, if the power supply system includes a lead battery 13), the number of batteries may be three or more.

The generator 11 is a device that generates electric power by using the rotation of the engine as a power source. In addition, when the vehicle is decelerating, regenerative electric energy is generated by the regenerative brake. The generator 11 is also called an alternator or a generator.

Further, the generator 11 may generate electric power in response to an instruction from, for example, the upper ECU 100. Then, for example, the generated electric power is supplied to the lead battery 13 and the LIB 14 to charge the lead battery 13 and the LIB 14.

The starter 12 is, for example, a starting device including an electric motor to start an engine. In the example shown in FIG. 1, the battery system 1 is configured to include the starter 12 and the generator 11, but for example, an ISG (Integrated Starter Generator) may be provided instead of the starter 12 and the generator 11. .. In the battery system 1, in addition to the load of the starter 12 and the generator 11 described above, for example, an auxiliary machine load such as a headlight or a wiper may be connected.

The lead battery 13 is a secondary battery using lead as an electrode. The lead battery 13 is, for example, a main power source for an electric device mounted on a vehicle.

The LIB 14 of the battery pack 10 is a secondary battery that charges or discharges, and serves as an auxiliary power source for, for example, a lead battery 13. As the LIB 14, an iron-based LIB can be used, but the LIB 14 is not limited to this.

The first switch 15 and the second switch 16 are switches (relays) that control short circuits and open circuits. The first switch 15 is connected between the lead battery 13 and the generator 11 (or starter 12). The second switch 16 is connected between the LIB 14 and the generator 11 (or starter 12). The opening and closing of the first switch 15 and the second switch 16 is controlled by the higher-level ECU 100 or the battery control device 20 described above.

For example, when the first switch 15 is turned on, the lead battery 13 and various loads such as the generator 11 and the starter 12 are electrically connected, and electric power can be supplied from the lead battery 13 to the various loads. .. On the other hand, when the first switch 15 is turned off, the electrical connection between the lead battery 13 and the various loads is cut off, and the supply of electric power from the lead battery 13 to the various loads is stopped. As described above, the first switch 15 is a changeover switch that switches between a state in which the lead battery 13 is connected as a power source and a state in which the connection of the lead battery 13 as a power source is cut off for various loads.

Further, for example, when the second switch 16 is turned on, the LIB 14 and various loads such as the generator 11 and the starter 12 are electrically connected, and electric power can be supplied from the LIB 14 to the various loads. On the other hand, when the second switch 16 is turned off, the electrical connection between the LIB 14 and the various loads is cut off, and the supply of electric power from the LIB 14 to the various loads is stopped. As described above, the second switch 16 is a changeover switch that switches between a state in which the LIB 14 is connected as a power source and a state in which the connection of the LIB 14 as a power source is cut off for various loads.

The higher-level ECU 100 is a higher-level ECU of the battery pack 10, acquires a vehicle condition or the like at any time, and controls the battery pack 10 according to the vehicle condition or the like. For example, the upper ECU 100 acquires information on the vehicle status, the status of the LIB 14, information on the status of the lead battery 13, and the like. The information regarding the state of the LIB 14 includes, for example, the SOC information of the LIB 14 estimated by the battery control device 20.

Then, the upper ECU 100 opens and closes the first switch 15 and the second switch 16 based on the vehicle condition, the state of the LIB 14 (for example, SOC), the state of the lead battery 13, and charges and discharges the lead battery 13 and the LIB 14. Control. Further, the upper ECU 100 controls the operation of various electric devices such as a generator 11, a starter 12, and an auxiliary machine (not shown) according to a vehicle condition or the like.

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

Further, the LIB 14 and the lead battery 13 are connected to the battery control device 20 as a power source. For example, the battery control device 20 is connected to the LIB 14 via the power supply line 14a, and is configured to be able to supply electric power from the LIB 14.

Specifically, the LIB changeover switch 18 is inserted in the power supply line 14a. When the LIB changeover switch 18 is turned on, the battery control device 20 and the LIB 14 are electrically connected, and power is supplied from the LIB 14 to the battery control device 20. On the other hand, when the LIB changeover switch 18 is turned off, the electrical connection between the battery control device 20 and the LIB 14 is cut off, and the supply of electric power from the LIB 14 to the battery control device 20 is stopped. As described above, the LIB changeover switch 18 is a changeover switch that switches between the state in which the LIB 14 is connected as a power source and the state in which the connection of the LIB 14 as a power source is cut off to the battery control device 20.

Further, for example, the battery control device 20 is connected to the lead battery 13 via the power supply line 13a, and is configured to be able to supply electric power from the lead battery 13.

Specifically, a lead battery changeover switch 17 is inserted in the power supply line 13a. When the lead battery changeover switch 17 is turned on, the battery control device 20 and the lead battery 13 are electrically connected, and power is supplied from the lead battery 13 to the battery control device 20. On the other hand, when the lead battery changeover switch 17 is turned off, the electrical connection between the lead battery 20 and the lead battery 13 is cut off, and the supply of power from the lead battery 13 to the battery control device 20 is stopped. As described above, the lead battery changeover switch 17 is a changeover switch that switches between the state in which the lead battery 13 is connected as a power source and the state in which the connection of the lead battery 13 as a power source is cut off to the battery control device 20. be.

The battery control device 20 controls the operations of the first and second switches 15 and 16, the lead battery changeover switch 17 and the LIB changeover switch 18 so that power is supplied from one of the LIB 14 and the lead battery 13. You may. For example, the battery control device 20 compares the voltage of the LIB 14 with the voltage of the lead battery 13, and sets the first and second switches 15 and 16 and the changeover switch for the lead battery so that the power is supplied from the higher voltage. The operation of the changeover switch 18 for 17 and the LIB may be controlled.

Here, the battery control device 20 according to the present embodiment uses a current integration method as an algorithm for SOC estimation. In the current integration method, the battery control device 20 detects, for example, the current value of the LIB 14 with a current sensor, integrates the detected current values, and estimates the SOC.

In the SOC estimation by the current integration method described above, the measurement error of the current sensor is accumulated, and the accumulation of the measurement error causes an error in the SOC estimation, so that the SOC estimation accuracy may decrease. Therefore, the battery control device 20 estimates the SOC by using the voltage when the battery is not charged / discharged in the LIB 14, that is, the open circuit voltage (OCV), in addition to the current integration method.

The SOC is estimated using the OCV when the state of the LIB 14 is in a predetermined state. For example, in the estimation of SOC using OCV, the state of LIB14 at the time of starting (for example, when the vehicle is started) shows the relationship between the detected OCV of LIB14 and OCV and SOC, and the charging characteristic (OCV-SOC characteristic curve). This is performed when the SOC can be estimated based on (see FIG. 3 described later)). The SOC estimation using OCV will be described in detail later.

Then, the battery control device 20 updates (corrects) the SOC estimated by the current integration method to the SOC estimated by using the OCV, so that the estimation accuracy of the SOC is caused by the accumulation of the measurement error of the current sensor. It is possible to suppress the decrease.

However, as described above, when the LIB 14 and the lead battery 13 are connected as a power source, there is a risk that the accuracy of SOC estimation using the OCV may decrease in the battery control device 20.

Specifically, for example, when power is supplied from the battery control device 20 or various loads from the LIB 14, when the battery control device 20 tries to detect OCV, it is discharged by the power supply. The voltage of the LIB 14 (that is, the closed circuit voltage (CCV)) is erroneously detected as the OCV. Therefore, in the battery control device 20, the SOC is estimated using the erroneous OCV. There was a risk that the SOC estimation accuracy would decrease.

Therefore, in the battery control device 20 according to the present embodiment, it is possible to suppress a decrease in the SOC estimation accuracy using the OCV, and as a result, the SOC estimation accuracy can be improved.

More specifically, the battery control device 20 detects the current of the LIB 14 with the current sensor 61 (see FIG. 2 described later), and estimates the SOC of the LIB 14 by the current integration method based on the detected current (step S1).

The battery control device 20 determines, for example, whether or not the state of the LIB 14 at the time of startup is a state (predetermined state) in which the SOC can be estimated using the OCV (step S2).

Then, when the battery control device 20 determines that the state of the LIB 14 is a state in which the SOC can be estimated using the OCV, the battery control device 20 turns off the second switch 16 and the LIB changeover switch 18 to serve as a power source for the LIB 14. The connection is cut off (step S3).

Although not shown, the battery control device 20 turns on the lead battery changeover switch 17 when the LIB changeover switch 18 is turned off so that power is supplied from the lead battery 13 to the battery control device 20. do.

Next, the battery control device 20 detects the OCV of the LIB 14 with the voltage sensor 62 (see FIG. 2 described later) (step S4). Next, the battery control device 20 updates the SOC estimated by the current integration method to the SOC estimated by using the OCV (step S5).

As described above, when the battery control device 20 according to the present embodiment detects the OCV when updating the SOC, the connection as the power source of the LIB 14 is cut off before the OCV is detected, in other words. The supply of electric power from the LIB 14 to the battery control device 20 and various loads is stopped.

As a result, in the battery control device 20 according to the present embodiment, the voltage (CCV) of the LIB 14 discharged by the power supply is not erroneously detected as the OCV, so that the SOC is estimated using the erroneous OCV. There is no. Therefore, in the present embodiment, it is possible to suppress a decrease in the estimation accuracy of the SOC using the OCV, and as a result, it is possible to improve the estimation accuracy of the SOC.

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 a configuration of a battery system 1 including a battery control device 20 according to an embodiment. In FIG. 2, only the components necessary for explaining the features of the present embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component shown in FIG. 2 is a functional concept and does not necessarily have to be physically configured as shown in the figure. For example, the specific form of distribution / integration of each functional block is not limited to the one shown in the figure, and all or part of the functional blocks are functionally or physically distributed in arbitrary units according to various loads and usage conditions. -It is possible to integrate and configure.

As shown in FIG. 2, the battery system 1 includes the lead battery 13, the LIB 14, the battery control device 20, the upper ECU 100, the current sensor 51 and the voltage sensor 52 connected to the lead battery 13, and the LIB 14. It includes a connected current sensor 61 and voltage sensor 62, a lead battery changeover switch 17, a LIB changeover switch 18, various electric devices 70, and first and second switches 15 and 16.

In FIG. 2, for simplification of the illustration, the above-mentioned generator 11 and starter 12, for example, auxiliary equipment (load) mounted on the vehicle such as a navigation device, audio, and air conditioner are used as various electric devices 70. Shown in blocks. Further, in FIG. 2, the lead battery changeover switch 17 and the LIB changeover switch 18 are shown in one block, and the first switch 15 and the second switch 16 are shown in one block.

The current sensor 51 is a sensor that measures the charge / discharge current of the lead battery 13. The voltage sensor 52 is a sensor that measures the battery voltage of the lead battery 13. The current sensor 51 and the voltage sensor 52 each output a signal indicating the measurement result to the battery control device 20.

The current sensor 61 is a sensor that measures the charge / discharge current of the LIB 14. The voltage sensor 62 is a sensor that measures the battery voltage of the LIB 14. The current sensor 61 and the voltage sensor 62 each output a signal indicating the measurement result to the battery control device 20.

The battery control device 20 includes a control unit 30 and a storage unit 40. The control unit 30 includes a detection unit 31, an estimation unit 32, a power supply control unit 33, and a determination unit 34.

The control unit 30 includes, for example, a computer 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 various circuits.

The CPU of the computer functions as a detection unit 31, an estimation unit 32, a power supply control unit 33, and a determination unit 34 of the control unit 30, for example, by reading and executing a program stored in the ROM.

Further, at least a part or all of the detection unit 31, the estimation unit 32, the power supply control unit 33, and the determination unit 34 of the control unit 30 are hardware such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field Programmable Gate Array). It can also be configured with.

Further, the storage unit 40 is a storage device such as a data flash, a non-volatile memory, or a register. The storage unit 40 stores the OCV-SOC map information 41.

The OCV-SOC map information 41 includes information on charging characteristics indicating the relationship between the open circuit voltage (OCV) of the LIB 14 and SOC, and specifically includes information on the OCV-SOC characteristic curve. The OCV-SOC characteristic curve is an example of charging characteristics showing the relationship between the open circuit voltage (OCV) and the SOC. Further, the estimation unit 32, which will be described later, can estimate the SOC from the OCV of the LIB 14 based on 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 by, for example, the least squares method with respect to the observed values of SOC and OCV when the LIB 14 is charged and discharged.

Here, the OCV-SOC characteristic curve of the iron-based LIB 14 will be described in detail. As shown in FIG. 3, in the OCV-SOC characteristic curve, when SOC changes in a relatively low region E1 (for example, between 0% and a predetermined value Aa), OCV also changes in region D1 (predetermined value Va and predetermined value Aa). It shows a characteristic that changes relatively greatly with respect to Vb). Similarly, when SOC changes in a relatively high region E3 (between a predetermined value Ab and 100%), OCV also has a characteristic that changes relatively significantly in a region D3 (between a predetermined value Vc and a predetermined value Vd). show. Therefore, for example, even if there is a slight detection error in the OCV in the area D1 or the area D3, the influence 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 the region E2 (between the predetermined value Aa and the predetermined value Ab) between the regions E1 and E3, the OCV is the region D2 (predetermined value Vb and the predetermined value) between the regions D1 and D3. It shows a characteristic that changes relatively small with Vc). As described above, the OCV-SOC characteristic curve has a flat region D2 in which the change in OCV with respect to the change in SOC is gradual. Therefore, for example, if there is a slight detection error in the OCV in the region D2, the SOC changes significantly, and it is difficult to estimate the SOC with high accuracy.

That is, in the OCV-SOC characteristic curve of the iron-based LIB 14, it is possible to estimate the SOC when the OCV is in the region D1 or D3, and when the OCV is in the region D2, the SOC is determined in terms of accuracy. Difficult to estimate.

Therefore, in the estimation unit 32 described later, for example, when the OCV of the LIB 14 at the time of activation is in a predetermined area such as the area D1 or the area D3, the state of the LIB 14 is a state in which the SOC can be estimated using the OCV (predetermined state). ).

Returning to the description of FIG. 2, the detection unit 31 of the control unit 30 detects the current and voltage of the lead battery 13 and the current and voltage of the LIB 14. For example, the detection unit 31 detects the current (current value) of the lead battery 13 based on the signal input from the current sensor 51. Further, the detection unit 31 detects the voltage (voltage value) of the lead battery 13 based on the signal input from the voltage sensor 52. The detection unit 31 outputs a signal indicating the detected current or voltage of the lead battery 13 to the determination unit 34 or the like.

Further, for example, the detection unit 31 detects the current (current value) of the LIB 14 based on the signal input from the current sensor 61. Further, the detection unit 31 detects the voltage (voltage value) of the LIB 14 based on the signal input from the voltage sensor 62. The detection unit 31 can detect the above-mentioned OCV and CCV as the voltage of the LIB 14. The detection unit 31 outputs a signal indicating the detected current or voltage to the estimation unit 32 or the like.

The estimation unit 32 estimates the SOC by the current integration method. For example, the estimation unit 32 calculates the initial SOC based on the OCV of the LIB 14 at the time of activation and the OCV-SOC characteristic curve.

Here, the power supply control unit 33 detects the OCV of the LIB 14 when the estimation unit 32 calculates the initial SOC, and the LIB changeover switch 18 is turned on to power the battery control device 20 from the LIB 14. When is supplied, the second switch 16 and the LIB changeover switch 18 are turned off before the OCV is detected to cut off the connection of the LIB 14 as a power source. When the second switch 16 and the LIB changeover switch 18 are turned off, the power supply control unit 33 turns on the first switch 15 and the lead battery changeover switch 17, and power is supplied from the lead battery 13 to the battery control device 20. To be done.

As a result, the detection unit 31 does not erroneously detect the voltage (CCV) of the LIB 14 discharged by the power supply as the OCV, so that the estimation unit 32 does not estimate the initial SOC using the erroneous OCV. Therefore, in the present embodiment, it is possible to suppress a decrease in the estimation accuracy of the initial SOC using the OCV, and as a result, it is possible to improve the estimation accuracy of the SOC.

Subsequently, the estimation unit 32 performs the SOC estimation process by the current integration method with the calculated initial SOC as the initial value.

As the calculation formula of the current integration method, for example, "SOC (k + 1) = SOC (k) + current integration / FCC" can be used. Here, k is an index of discretized time, in other words, the number of steps. The current integral is a value obtained by integrating the above-mentioned current values. FCC is a constant called full charge capacity.

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

For example, the estimation unit 32 determines whether or not the state of the LIB 14 at the time of starting (for example, when the vehicle is started) is a state (predetermined state) in which the SOC can be estimated using the OCV and the OCV-SOC characteristic curves. do. When it is determined that the state of the LIB 14 is not a predetermined state, the estimation unit 32 does not update the SOC. On the other hand, the estimation unit 32 updates the SOC when it is determined that the state of the LIB 14 is a predetermined state.

Here, the power supply control unit 33 detects the OCV of the LIB 14 when the estimation unit 32 updates the SOC, and the LIB changeover switch 18 is turned on to transfer power from the LIB 14 to the battery control device 20. When supplied, the second switch 16 and the LIB changeover switch 18 are turned off to cut off the connection of the LIB 14 as a power source before the OCV is detected. When the second switch 16 and the LIB changeover switch 18 are turned off, the power supply control unit 33 turns on the first switch 15 and the lead battery changeover switch 17, and power is supplied from the lead battery 13 to the battery control device 20. To be done.

Therefore, the detection unit 31 detects the voltage (OCV) of the LIB 14 that is not supplying power to the battery control device 20 and is not charged / discharged, and the estimation unit 32 estimates the SOC using the OCV. Will be done.

In other words, since the detection unit 31 does not erroneously detect the voltage (CCV) of the LIB 14 discharged by the power supply as the OCV, the estimation unit 32 does not estimate the SOC using the erroneous OCV. Therefore, in the present embodiment, it is possible to suppress a decrease in the estimation accuracy of the SOC using the OCV, and as a result, it is possible to improve the estimation accuracy of the SOC.

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

Here, the charging state of the lead battery 13 will be described. As described above, the power supply control unit 33 turns off the second switch 16 and the LIB changeover switch 18 to cut off the connection of the LIB 14 as a power source, while turning on the first switch 15 and the lead battery changeover switch 17. , The lead battery 13 is supplied with power to the battery control device 20. However, depending on the usage state, the lead battery 13 may be in a charged state in which the voltage drops to such an extent that it cannot be used as a power source for the battery control device 20 or various loads.

In such a case, the battery control device 20 according to the present embodiment may connect the LIB 14 that has been cut off as a power source as a power source. As a result, even if the voltage of the lead battery 13 drops to the extent that it cannot be used as a power source for the battery control device 20 or various loads, the power to the battery control device 20 or the like can be supplied by reconnecting the LIB 14 as a power source. Supply can be secured.

Specifically described below, the determination unit 34 performs a process of determining whether or not the lead battery 13 cannot be used as a power source for the battery control device 20 or various loads. For example, the determination unit 34 determines whether or not the voltage of the lead battery 13 is equal to or less than a predetermined voltage. The predetermined voltage is set to a value (for example, 8V) indicating a charging state (unusable state) such that the voltage of the lead battery 13 drops and cannot be used as a power source for the battery control device 20 or the like. It is not limited to, and may be set to any value. Then, the determination unit 34 notifies the power supply control unit 33, the estimation unit 32, and the like of the above determination result.

The power supply control unit 33 notified of the determination result controls the connection of the lead battery 13 as the power source of the battery control device 20 and the like and the connection of the LIB 14 based on the determination result. For example, when the determination unit 34 determines that the voltage of the lead battery 13 is equal to or lower than a predetermined voltage, the power supply control unit 33 turns on the second switch 16 and the LIB changeover switch 18, and powers the battery control device 20 and the like. LIB14, which had been cut off from the connection as a power source, is connected (reconnected) as a power source. Further, the power supply control unit 33 turns off the first switch 15 and the lead battery changeover switch 17 to cut off the connection of the lead battery 13 as a power source.

As a result, even when the lead battery 13 cannot be used as a power source for the battery control device 20 and various loads, the power supply to the battery control device 20 and various loads can be secured by connecting the LIB 14 as a power source. Can be done.

When the determination unit 34 determines that the voltage of the lead battery 13 is not equal to or lower than a predetermined voltage, the power supply control unit 33 may continue to cut off the connection of the LIB 14 as a power source.

As described above, when the LIB 14 that has cut off the connection as the power source of the battery control device 20 or the like is reconnected as the power source, when the detection unit 31 tries to detect the OCV, it is discharged by the power supply. There is a possibility that the voltage (CCV) of the LIB 14 is erroneously detected as an OCV, and the estimation unit 32 estimates the SOC using the erroneous OCV and updates the SOC.

Therefore, the estimation unit 32 according to the present embodiment prohibits the update process for updating the SOC when the LIB 14 that has been cut off as a power source by the power supply control unit 33 is connected (reconnected) as a power source. You may.

As a result, in the battery control device 20 according to the present embodiment, the voltage (CCV) of the LIB 14 discharged by the power supply is not erroneously detected as the OCV, so the SOC is estimated using the erroneous OCV. Since the SOC is not updated, the estimation accuracy of the SOC can be further improved.

Here, the prohibition of the SOC update process described above will be described. For example, if the estimation unit 32 continues to prohibit the SOC update process for a relatively long period of time, the SOC will be estimated by the current integration method for a relatively long period of time. In such a case, the estimation accuracy of the SOC may decrease due to the accumulation of measurement errors of the current sensor 61 and the like.

Therefore, the estimation unit 32 according to the present embodiment may execute (restart) the SOC update process when the SOC estimated by the current integration method satisfies a predetermined condition when the update process is prohibited. ..

As a result, the estimation unit 32 can update (correct) the SOC estimated by the current integration method, so that the estimation accuracy of the SOC is suppressed from being lowered due to the accumulation of measurement errors of the current sensor 61 and the like. be able to. In the restarted SOC update process, since the LIB 14 is connected to the battery control device 20 or the like as a power source, the estimation unit 32 calculates the OCV of the LIB 14 and uses the calculated SOC to estimate the SOC. , Executes the process of updating the SOC.

Specifically, the estimation unit 32 will explain the predetermined conditions described above by the SOC when the estimation period indicating the period for estimating the SOC by the current integration method has elapsed when the update process is prohibited. Is determined to be satisfied. The predetermined period is set to a value that may reduce the SOC estimation accuracy due to, for example, accumulation of measurement error of the current sensor 61, but is not limited to this, and is set to an arbitrary value. You may.

When the SOC estimated by the current integration method satisfies a predetermined condition when the update process is prohibited, the estimation unit 32 calculates the OCV based on the CCV detected by the detection unit 31. That is, since the LIB 14 is connected to the battery control device 20 or the like as a power source, the voltage of the LIB 14 detected by the detection unit 31 is CCV, and the estimation unit 32 calculates (estimates) the OCV based on the CCV. do. In the following, the calculated OCV may be referred to as "calculated OCV".

Specifically, the estimation unit 32 calculates the calculated OCV using the following equation (1).
Calculation OCV = CCV- (R × I) ・ ・ ・ Equation (1)
In the formula (1), the CCV is the voltage of the LIB 14 detected in a state where the LIB 14 is connected to the battery control device 20 and various loads as a power source. Further, R is the internal resistance of the LIB 14, and I is the total value of the current consumption of, for example, the battery control device 20 including a computer and the like. Regarding I in detail, the current value of charging the LIB 14 is a positive value, and the current value of discharging from the LIB 14 is a negative value.

The estimation unit 32 estimates the SOC based on the calculated OCV and the OCV-SOC characteristic curve (see FIG. 3). Then, the estimation unit 32 executes an update process for updating the SOC estimated by the current integration method using the estimated SOC.

In this way, the estimation unit 32 executes (restarts) the SOC update process when the SOC estimated by the current integration method satisfies a predetermined condition, so that the SOC estimation accuracy is the measurement error of the current sensor 61. It is possible to suppress the decrease due to accumulation or the like.

Since the voltage of the LIB 14 (CCV in this case) is transiently moving at the time of startup, the estimation unit 32 waits for a certain period of time until the polarization stabilizes, and then executes the calculation process of the calculated OCV. May be good.

Next, the processing procedure executed by the battery control device 20 according to the embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a processing procedure executed by the battery control device 20.

As shown in FIG. 4, the control unit 30 of the battery control device 20 first detects the current of the LIB 14 (step S10). Subsequently, the control unit 30 estimates the SOC of the LIB 14 based on the detected current by the current integration method (step S11).

Next, the control unit 30 determines whether or not the state of the LIB 14 at the time of activation is, for example, a state in which the SOC can be estimated using the OCV (predetermined state) (step S12). When it is determined that the state of the LIB 14 is not a predetermined state (steps S12, No), the control unit 30 ends the process as it is.

On the other hand, when the control unit 30 determines that the state of the LIB 14 is a predetermined state (step S12, Yes), the control unit 30 determines whether or not the voltage of the lead battery 13 is equal to or lower than the predetermined voltage (step S13). That is, it is determined whether or not the lead battery 13 cannot be used as a power source for the battery control device 20.

When the control unit 30 determines that the voltage of the lead battery 13 is not equal to or lower than a predetermined voltage (steps S13, No), that is, when it is determined that the lead battery 13 can be used as a power source for the battery control device 20. The second switch 16 and the LIB changeover switch 18 are turned off, and the connection of the LIB 14 as a power source is cut off (step S14).

Subsequently, the control unit 30 detects the OCV of the LIB 14 (step S15). Then, the control unit 30 executes an update process for updating the SOC estimated by the current integration method (step S16). Specifically, the control unit 30 estimates the SOC based on the OCV and the OCV-SOC characteristic curve (see FIG. 3) detected in step S15, and estimates by the current integration method using the estimated SOC. Update (correct) the SOC.

When the control unit 30 determines that the voltage of the lead battery 13 is equal to or lower than a predetermined voltage (step S13, Yes), that is, when it is determined that the lead battery 13 cannot be used as a power source for the battery control device 20. The second switch 16 and the LIB changeover switch 18 are turned on, and the LIB 14 that has been disconnected as a power source is reconnected as a power source (step S17).

Next, the control unit 30 determines whether or not a predetermined period has elapsed, which indicates the period for which the SOC is estimated by the current integration method when the update process is prohibited (step S18). When it is determined that the estimated period has not elapsed (steps S18, No), the control unit 30 prohibits the update process for updating the SOC (step S19).

On the other hand, when it is determined that the estimated period has elapsed (step S18, Yes), the control unit 30 calculates the calculated OCV based on the detected CCV of the LIB 14 (step S20).

Then, the control unit 30 executes the SOC update process using the calculated OCV (step S21). Specifically, the control unit 30 estimates the SOC based on the calculated OCV calculated in step S20 and the OCV-SOC characteristic curve (see FIG. 3), and estimates by the current integration method using the estimated SOC. Update (correct) the SOC that has been added.

As described above, in the battery control device 20 according to the embodiment, a LIB 14 (an example of a first battery) and a lead battery 13 (an example of a second battery) are connected as a power source. The battery control device 20 includes a detection unit 31, an estimation unit 32, and a power supply control unit 33. The detection unit 31 detects the current of the LIB 14 and the OCV (open circuit voltage) of the LIB 14. The estimation unit 32 estimates the SOC (charge rate) of the LIB 14 by a current integration method based on the current detected by the detection unit 31. When the state of the LIB 14 is a state in which the SOC can be estimated based on the OCV detected by the detection unit 31 and the charging characteristic (OCV-SOC characteristic curve) indicating the relationship between the OCV and the SOC. , The SOC estimated by the current integration method is updated to the SOC estimated based on the OCV and the charging characteristics. When the detection unit 31 detects the OCV when the estimation unit 32 updates the SOC, the power supply control unit 33 cuts off the connection of the LIB 14 as a power supply. As a result, the SOC estimation accuracy of the LIB 14 can be improved.

(Modification example)
Next, a modified example of the embodiment will be described. As described above, the battery control device 20 estimates the SOC using the OCV and executes the update (correction) process and the like. The OCV is preferably a voltage of the LIB 14 in a stable state in which the LIB 14 is not loaded for a certain period of time after the engine is stopped and the influence of polarization is eliminated.

Further, for example, when an iron-based material is used for the LIB 14, the OCV-SOC characteristic curve used for estimating the SOC has different characteristics depending on the charge / discharge state before the polarization of the LIB 14 is eliminated. Therefore, the OCV-SOC map information 41 (see FIG. 2) according to the embodiment and the modified example has a plurality of (here, two types) OCV-SOC characteristics having different characteristics depending on the charge / discharge state before the polarization of the LIB 14 is eliminated. Curve information may be included. This will be described with reference to FIG.

FIG. 5 is a diagram illustrating an OCV-SOC characteristic curve. As shown in FIG. 5, the OCV-SOC characteristic curve has different characteristics depending on whether the LIB 14 is in the charged state or the discharged state before the polarization is eliminated. In FIG. 5, the OCV-SOC characteristic curve when the state before the polarization elimination (for example, before the engine is stopped) of the LIB 14 is the charged state is shown by a solid line, and the state before the polarization elimination (for example, before the engine is stopped) is discharged. The OCV-SOC characteristic curve in the state is shown by a broken line.

In the example of FIG. 5, the battery control device 20 estimates that the SOC is "A1" when the state before the polarization is eliminated is the charged state and the OCV at the time of estimating the SOC is Vx. On the other hand, the battery control device 20 estimates that the SOC is "A2" when the state before the polarization is eliminated is the discharge state and the OCV at the time of estimating the SOC is Vx. As described above, even if the OCV is the same “Vx”, the estimated SOC value changes depending on whether the state before the polarization of the LIB 14 is eliminated is the charged state or the discharged state. Therefore, it is desired to accurately determine the charge / discharge state of the LIB 14 before the polarization is eliminated.

Therefore, the battery control device 20 according to the modified example has a configuration that can accurately determine the charge / discharge state of the LIB 14 before the polarization is eliminated. Specifically, the battery control device 20 according to the modified example determines the charge / discharge state of the LIB 14 before the depolarization of the LIB 14 based on the voltage of the LIB 14 before the depolarization of the LIB 14.

Specifically, the battery control device 20 according to the modified example measures the voltage of the LIB 14 a plurality of times from the engine stop to before the polarization is eliminated, and based on the measured voltage tendency (slope), before the polarization of the LIB 14 is eliminated. The charge / discharge state of is determined. Then, for example, the battery control device 20 estimates the SOC based on the OCV of the LIB 14 and the charging characteristics (OCV-SOC characteristic curve) according to the determination result.

The above-mentioned voltage tendency (slope) will be described with reference to FIG. FIG. 6 is a diagram showing the voltage of the LIB 14 from before the engine is stopped until the polarization is eliminated. In FIG. 6, the voltage when the LIB 14 is in the charged state before the engine is stopped is shown by a solid line, and the voltage when the LIB 14 is in a discharged state is shown by a broken line. Further, FIG. 6 shows an example in which the engine is stopped at time T1 and there is no load for a certain period of time thereafter, and the influence of polarization is eliminated at time T4. Therefore, it can be said that the times T1 to T4 are the polarization elimination periods of LIB14.

As shown by the solid line in FIG. 6, when the engine is stopped while the LIB 14 is in the charged state (time T1), the voltage of the LIB 14 decreases with the passage of time. On the other hand, as shown by the broken line in FIG. 6, if the engine is stopped while the LIB 14 is in the discharged state, the voltage of the LIB 14 increases with the passage of time. In the modified example, the charge / discharge state before the polarization of the LIB 14 is eliminated is determined based on the voltage tendency of the LIB 14 described above, and the SOC is estimated.

Specifically, the control unit 30 (correctly, the detection unit 31 (see FIG. 2)) of the battery control device 20 according to the modified example first measures the voltage of the LIB 14 a plurality of times after the engine is stopped, and then stores the storage unit. Store in 40. In the example of FIG. 6, the time T2 and T3 are measured twice, but the time is not limited to this, and the time may be measured three times or more. Further, the voltage of the LIB 14 is measured, for example, every time an arbitrary predetermined time elapses, but the measurement timing is not limited to this and can be set arbitrarily. The power supply control unit 33 (see FIG. 2) may turn off the second switch 16 and the LIB changeover switch 18 to cut off the connection of the LIB 14 as a power source before the voltage of the LIB 14 is measured. ..

Subsequently, the control unit 30 detects the OCV of the LIB 14 by the detection unit 31 when the vehicle is started after the polarization of the LIB 14 is eliminated (after the time T4), and estimates the SOC based on the detected OCV. ..

Here, the power supply control unit 33 turns off the second switch 16 and the LIB changeover switch 18 to cut off the connection of the LIB 14 as a power source before detecting the OCV of the LIB 14. As a result, the detection unit 31 does not erroneously detect the voltage (CCV) of the LIB 14 discharged to the battery control device 20 and various loads as OCV. When the second switch 16 and the LIB changeover switch 18 are turned off, the power supply control unit 33 turns on the first switch 15 and the lead battery changeover switch 17, and power is supplied from the lead battery 13 to the battery control device 20. To be done.

The detection unit 31 detects the OCV with the second switch 16 and the LIB changeover switch 18 turned off as described above. Subsequently, the estimation unit 32 (see FIG. 2) of the control unit 30 reads out the voltage information of the LIB 14 stored in the storage unit 40, and determines the charge / discharge state of the LIB 14 before the polarization is eliminated.

For example, as shown in FIG. 6, the estimation unit 32 eliminates the polarization of the LIB 14 when the measured voltage of the LIB 14 tends to decrease, in other words, when the measured voltage of the LIB 14 has a negative slope. It is determined that the previous state was the charged state. On the other hand, in the estimation unit 32, when the tendency of the measured voltage of the LIB 14 is increasing, in other words, when the measured voltage of the LIB 14 is a positive slope value, the state before the polarization of the LIB 14 is eliminated is the discharged state. Judge that there was.

As described above, in the modified example, by using the voltage of the LIB 14 from the engine stop to before the polarization is eliminated, the charge / discharge state of the LIB 14 before the polarization is eliminated can be accurately determined.

Then, the estimation unit 32 estimates the SOC of the LIB 14 based on the detected OCV and the OCV-SOC characteristic curve (see FIG. 5) according to the charge / discharge state before the polarization of the LIB 14 is eliminated.

As described above, in the modified example as well, as in the embodiment, the connection of the LIB 14 as a power source is cut off before the OCV of the LIB 14 is detected. Therefore, the estimation unit 32 uses the wrong OCV of the LIB 14. There is no estimation of SOC. Therefore, even in the modified example, it is possible to suppress a decrease in the SOC estimation accuracy of the LIB 14 using the OCV, and as a result, the SOC estimation accuracy can be improved.

Next, a processing procedure executed by the battery control device 20 according to the modified example will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a processing procedure executed by the battery control device 20 according to the modified example. It should be noted that the process of FIG. 7 is executed after the engine is stopped as an example.

As shown in FIG. 7, the control unit 30 of the battery control device 20 determines whether or not the influence of polarization has been eliminated after a certain period of time has elapsed after the engine was stopped (step S100). The control unit 30 determines that the influence of polarization has not been eliminated (steps S100, No) because it is before a certain period of time elapses when the process of step S100 is first executed, and then the voltage of LIB 14 is measured. It is determined whether or not it is the timing (step S101). Here, the measurement timing is, for example, the timing at which the above-mentioned predetermined time has elapsed from the stop of the engine or the previous voltage measurement. The predetermined time shall be shorter than the above-mentioned fixed time.

When the control unit 30 determines that it is not the voltage measurement timing of the LIB 14 (steps S101 and No), the control unit 30 returns to the process of step S100. On the other hand, when the control unit 30 determines that it is the measurement timing of the voltage of the LIB 14 (step S101, Yes), the control unit 30 measures (detects) the voltage of the LIB 14 (step S102), stores the voltage in the storage unit 40, and steps S100. Return to the process of.

When it is determined that the influence of polarization has been eliminated (step S100, Yes), the control unit 30 determines whether or not the vehicle has been started (step S103). When it is determined that the vehicle has not been started (steps S103, No), the control unit 30 repeats the process of step S103.

When it is determined that the vehicle has been started (step S103, Yes), the control unit 30 turns off the second switch 16 and the LIB changeover switch 18 and cuts off the connection of the LIB 14 as a power source (step S104).

Subsequently, the control unit 30 detects the OCV of the LIB 14 (step S105). Next, the control unit 30 determines whether or not the state before the polarization of the LIB 14 is eliminated is the charged state based on the tendency (slope) of the voltage obtained from the voltage information of the LIB 14 stored in the storage unit 40. (Step S106).

When the control unit 30 determines that the state of the LIB 14 before the depolarization is in the charged state (step S106, Yes), the detected OCV and the OCV-SOC characteristic curve for the charged state (solid line in FIG. 6). The SOC is estimated based on (step S107).

On the other hand, when the control unit 30 determines that the state of the LIB 14 before the depolarization is not in the charged state (steps S106, No), that is, when it is determined that the LIB 14 is in the discharged state, the detected OCV and the discharge The SOC is estimated based on the OCV-SOC characteristic curve for the state (broken line in FIG. 6) (step S108).

In the above-described modification, the voltage measurement of the LIB 14 (including the detection of the OCV) is performed by temporarily activating the battery control device 20 including the computer or the like while the IG (ignition) is off. It is not limited to this. That is, for example, the voltage of the LIB 14 may be measured (including the detection of the OCV) when the IG is turned on.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

1 Battery system 13 Lead battery 14 LIB
20 Battery control device 31 Detection unit 32 Estimator unit 33 Power supply control unit 34 Judgment unit

Claims (8)

A battery control device to which the first battery and the second battery are connected as a power source.
A detector that detects the current of the first battery and the open circuit voltage of the first battery,
The charge rate of the first battery is estimated by the current integration method based on the current detected by the detection unit, and the state of the first battery is the open circuit voltage detected by the detection unit and the open circuit voltage. When the charge rate can be estimated based on the charge characteristic indicating the relationship between the open circuit voltage and the charge rate, the charge rate estimated by the current integration method is used as the open circuit voltage and the charge characteristic. An estimation unit that updates the charge rate estimated based on
A battery control including a power supply control unit that cuts off the connection of the first battery as a power source when the detection unit detects the open circuit voltage when the charge rate is updated by the estimation unit. Device. A determination unit for determining whether or not the voltage of the second battery is equal to or lower than a predetermined voltage is provided.
The power supply control unit
The first aspect of claim 1, wherein when the determination unit determines that the voltage of the second battery is equal to or lower than a predetermined voltage, the first battery, which has been disconnected as a power source, is connected as a power source. Battery control device. The estimation unit
The battery control according to claim 2, wherein when the first battery, which has been disconnected as a power source by the power supply control unit, is connected as a power source, the update process for updating the charge rate is prohibited. Device. The detection unit
The closed circuit voltage of the first battery is detected,
The estimation unit
When the charge rate estimated by the current integration method satisfies a predetermined condition when the update process is prohibited, the open circuit voltage is calculated based on the closed circuit voltage detected by the detection unit. The battery control device according to claim 3, wherein the update process is executed using the calculated open circuit voltage and the charge rate estimated based on the charge characteristics. The estimation unit
The battery control device according to claim 4, wherein it is determined that the charge rate satisfies the predetermined condition when the estimated period indicating the period for which the charge rate is estimated by the current integration method elapses. .. The first battery is a lithium ion battery.
The battery control device according to any one of claims 1 to 5, wherein the second battery is a lead battery. The estimation unit
The charge / discharge state of the first battery before depolarization is determined based on the voltage before depolarization of the first battery, and the charge rate is determined based on the open circuit voltage and the charging characteristics according to the determination result. The battery control device according to any one of claims 1 to 6, wherein the battery control device is characterized in that. It is a battery control method of a battery control device in which a first battery and a second battery are connected as a power source.
A detection step for detecting the current of the first battery and the open circuit voltage of the first battery, and
The charge rate of the first battery is estimated by a current integration method based on the current detected by the detection step, and the state of the first battery is the open circuit voltage detected by the detection step and the open circuit voltage. When the charge rate can be estimated based on the charge characteristic indicating the relationship between the open circuit voltage and the charge rate, the charge rate estimated by the current integration method is used as the open circuit voltage and the charge characteristic. And the estimation process to update to the estimated charge rate based on
When the open circuit voltage is detected in the detection step when updating the charge rate in the estimation step, the battery control includes a power supply control step of cutting off the connection of the first battery as a power source. Method.

Images