JP6531784B2 - Storage element management device, and SOC estimation method for storage element - Google Patents

Description

  The invention disclosed by the present specification relates to a technique for estimating SOC (remaining capacity state of charge) of a storage element.

  Conventionally, as an example of a method of estimating the SOC of a storage element, there is an SOC estimation method using OCV (open circuit voltage) of a battery. This is a method of measuring the OCV of a battery, referring to the correlation between the OCV and SOC determined in advance, and using the SOC corresponding to the measured OCV as the estimated SOC (see Patent Document 1).

  JP, 2007-171205, A

  By the way, in some storage elements, the correlation between the OCV and the SOC is not in direct proportion but draws a curve. With such a storage element, the OCV measurement error is determined by the SOC estimation method using the OCV. The error width of SOC varies depending on the measured value of OCV. In particular, in the case of a storage element in which an electrode material having a wide range of minute change regions with a small change rate of OCV with respect to SOC is used, the error between the SOC obtained by the SOC estimation method by OCV and the actual SOC becomes large. There is a risk of

  In this specification, a technology is disclosed that can suppress that the SOC determined by the SOC estimation method using OCV is determined as the estimated SOC despite the fact that it is different from the actual SOC.

  In the storage element management device disclosed by the present specification, in the correlation between the OCV and the SOC, a minute change region in which the change rate of the OCV with respect to the SOC is less than or equal to a reference value, and the change rate is higher than the reference value. A voltage sensor for detecting the voltage of the storage element having a high steep change area, a memory storing at least information on the correlation between the OCV and the SOC in the steep change area, and a control unit; The control unit determines whether the voltage measurement process of measuring the OCV of the storage element based on the detection result of the voltage sensor and the measured value of the OCV measured by the voltage measurement process are within the steep change region. When it is determined in the OCV determination process of determining and the OCV determination value in the OCV determination process that the measured value of the OCV is within the steep change area, the information stored in the memory Based on the above, if the SOC corresponding to the measured value of the OCV is determined as the estimated SOC, and it is determined in the OCV determination processing that the measured value of the OCV is not within the steep change region, the SOC corresponding to the measured value of the OCV To prohibit the determination of the estimated SOC.

  In the storage element management device, in the correlation between the OCV and the SOC, the slight change region may be present in the two slight change regions sandwiching the sharp change region. Further, in the storage element management device, the OCV of the steep change area may be within the rated voltage range of the storage element.

  In the storage element management device, the control unit is configured to execute an acquisition process for obtaining a value of a variable element of the storage element having a correlation with the SOC and different from the OCV, and the SOC estimation In the processing, when it is determined in the OCV determination processing that the measured value of the OCV is not within the steep change region, the SOC based on the value of the variable element acquired in the acquisition processing may be determined as the estimated SOC.

  The storage element management device includes a current sensor that detects a current flowing through the storage element, and the control unit integrates the current flowing through the storage element over time based on the detection result of the current sensor as the acquisition process. SOC integration processing for obtaining an estimated SOC by current integration, and in the SOC estimation processing, the SOC is determined on the condition that the measured value of the OCV is determined to be within the steep change region in the OCV determination processing. The estimated SOC obtained by the integration process is shifted to the SOC corresponding to the measured value of the OCV in the correlation between the OCV and the SOC.

  In the storage element management device, the control unit determines whether the charging device is capable of charging the storage element or not, and determines whether or not the charging device is in the chargeable state. There is a configuration to execute SOC maintenance processing that causes the charging device to execute a charging operation that maintains the SOC estimated in the SOC estimation processing above the minimum value of the SOC in the steep change region when it is determined that there is You may

  In the storage element management device, the control unit determines whether the charging device is capable of charging the storage element or not, and determines whether or not the charging device is in the chargeable state. There is a configuration to execute SOC maintenance processing that causes the charging device to execute a charging operation that maintains the SOC estimated in the SOC estimation processing below the maximum value of the SOC in the steep change region when it is determined that there is You may

  In the storage element management device, the storage element is a secondary battery, and the information stored in the memory is a steep change region in the correlation when the secondary battery is charged, and discharge of the secondary battery. Information related to the correlation between an OCV and an SOC in an area where both of the correlation at the time of the correlation and the abrupt change area exist, and the control unit determines whether the OCV and the SOC in the SOC estimation process The SOC corresponding to the measured value of the OCV may be estimated based on the information on the correlation.

  A storage element pack may be provided that includes a storage element and the storage element management device.

  The present invention can be realized in various aspects such as a storage element management device, an SOC estimation method, a computer program for realizing the function of the storage element management device, and a recording medium recording the computer program. .

  According to the present invention, it is possible to suppress that the SOC determined by the SOC estimation method using the OCV is determined as the estimated SOC despite the fact that it is different from the actual SOC.

Schematic which shows the structure of the battery pack which concerns on one Embodiment Graph showing correlation between OCV and SOC Partial enlargement of the graph showing the correlation between OCV and SOC Flow chart showing battery management processing Flow chart showing charge control processing

(Outline of this embodiment)
The storage element targeted by the storage element management device of the present invention is a sharp change area where the change rate of OCV to SOC is less than or equal to the reference value and the change rate is higher than the reference value in the correlation between OCV and SOC. There is a change area. On the other hand, according to this configuration, when it is determined that the measured value of OCV is within the steep change region, the measured value of OCV is dealt with based on the information on the correlation between OCV and SOC in the steep change region. The SOC to be determined is determined to be the estimated SOC. On the other hand, when it is determined that the measured value of OCV is not within the steep change region, it is prohibited to determine the SOC corresponding to the measured value of OCV as the estimated SOC. As a result, it is possible to suppress that the SOC determined by the SOC estimation method using the OCV is determined as the estimated SOC despite the fact that it is different from the actual SOC.

  The OCV in the steep change region is within the rated voltage range of the storage element. Therefore, during normal use of the storage element, it is possible to estimate the SOC corresponding to the measured value of OCV.

  When it is determined that the charging device is in the chargeable state, the storage element management device causes the charging device to maintain the SOC estimated in the SOC estimation process at least the minimum SOC value in the sharp change region. Run it. As a result, for example, when the charging apparatus becomes non-chargeable, the SOC of the storage element is already less than the minimum value of the steep change region, so the error between the estimated SOC and the actual SOC occurs during the non-charge state. It is possible to suppress the occurrence of a situation where the storage element management device is left as it is.

  When it is determined that the charging device is in the chargeable state, the storage element management device causes the charging device to maintain the SOC estimated in the SOC estimation process at or below the maximum value of the SOC in the sharp change region. Run it. Thereby, for example, when the charging device becomes incapable of charging, the SOC of the storage element already exceeds the highest value in the steep change region, and the SOC of the storage element is further increased by a charger other than the charging device. In addition, it is possible to suppress the occurrence of a situation where the storage element management device is left with the error between the estimated SOC and the actual SOC occurring while charging is not possible by the charging device.

  Because the correlation between OCV and SOC changes depending on whether the use state of the storage element before measurement of OCV is charge state or discharge state, a voltage difference occurs even though SOC is the same value Under certain conditions, the error between the estimated SOC and the actual SOC may be large. On the other hand, according to the present configuration, the information stored in the memory includes both a sharp change region in the correlation at the time of charging of the secondary battery and a sharp change region in the correlation at the time of discharging of the secondary battery It is information on the correlation between one OCV and SOC in the existing area. Such a steep change region has a relatively small difference in SOC with respect to the same OCV during charge and discharge as compared to other regions. Therefore, it is possible to estimate the SOC corresponding to the measured value of OCV by using common information in both states without determining whether the state before the OCV measurement is in the charged state or in the discharged state. .

  According to the storage element management device, when it is determined that the measured value of the OCV is not within the abrupt change region, the SOC is estimated based on the value of the variable element of the storage element different from the OCV. On the other hand, when it is determined that the measured value of OCV is within the steep change region, the SOC corresponding to the measured value of OCV is determined as the estimated SOC based on the information on the correlation between the OCV and SOC within the steep change region. Ru. This makes it possible to avoid the estimation of the SOC from the OCV in the slight change region, and to suppress the occurrence of an error between the estimated SOC and the actual SOC.

  Further, the estimated SOC obtained by the SOC integration process is shifted to the SOC corresponding to the measured value of OCV in the correlation between OCV and SOC. As a result, even if the measured value of OCV is within the slight change region, the estimated SOC is actually compared with the configuration in which the estimated SOC is shifted to the SOC corresponding to the measured value of OCV in the correlation between OCV and SOC. It is possible to suppress that the error with the SOC of the above becomes larger than that before the shift.

One embodiment will be described with reference to FIGS. 1 to 5.
The battery pack 1 of the present embodiment is mounted, for example, on an electric car or a hybrid car, and supplies power to a power source operated by electric energy. Hereinafter, a hybrid vehicle will be described as an example.

(Configuration of battery pack)
As shown in FIG. 1, the battery pack 1 includes a battery pack 2 and a battery management system (Battery Management System, hereinafter an example of a storage element management system called BMS) 3. The battery pack 2 is an example of a storage element and a secondary battery, and has a configuration in which a plurality of battery cells C are connected in series, and each battery cell C is a secondary battery that can be repeatedly charged. An iron phosphate lithium ion battery having a negative electrode formed of a graphite material.

  The battery pack 2 is electrically connected to the charging device 40 provided inside or outside the hybrid vehicle or a load (not shown) such as a power source provided inside the hybrid vehicle via the wiring 4 Be done. Hereinafter, the charging device 40 includes an alternator 41, which is an example of a generator, and a charge control unit 42, and receives power supply from the alternator 41 to charge the battery assembly 2. The charge control unit 42 is, for example, an engine control unit, and can increase or decrease the power generation output level of the alternator 41.

  The BMS 3 includes a control unit 31, an analog-to-digital converter (hereinafter referred to as ADC) 32, a current sensor 33, and a voltage sensor 34. The control unit 31 has a central processing unit (hereinafter referred to as a CPU) 35 and a memory 36 such as a ROM or a RAM. The memory 36 stores various programs (including a storage element management program) for controlling the operation of the BMS 3, and the CPU 35 executes a battery management process described later according to the program read from the memory 36, etc. , Control each part. The control unit 31 is an example of a control unit.

  The current sensor 33 detects a current value I of a charge current or a discharge current (hereinafter referred to as a charge / discharge current) flowing through the battery pack 2 through the wiring 4 and detects an analog value corresponding to the detected current value I [A]. The detection signal SG1 is transmitted to the ADC 32. The voltage sensor 34 is connected to both ends of the battery pack 2, detects a voltage value V [V] which is a voltage across the battery pack 2, and transmits an analog detection signal SG2 corresponding to the detected voltage value V to the ADC 32. Do. The voltage sensor 34 can detect an accurate voltage value V in which the influence of the wiring resistance of the wiring 4 is suppressed by directly detecting the voltage at both ends without using the wiring 4.

  The ADC 32 converts the detection signals SG1 and SG2 transmitted from the current sensor 33 and the voltage sensor 34 from analog signals to digital signals, and stores digital data indicating the current value I and the voltage value V in the memory 36. The charging device 40 is provided with an operation unit (not shown) for receiving an input from the user, and a display unit (not shown) comprising a liquid crystal display for displaying the deterioration state of the assembled battery 2 and the like.

(About SOC estimation method by OCV and SOC estimation method by current integration)
The SOC estimation method by OCV is a method of measuring the OCV of a battery, referring to a predetermined correlation between the OCV and the SOC, and using the SOC corresponding to the measured OCV as the estimated SOC. The SOC estimation method based on current integration first measures OCV to calculate an initial SOC, and then estimates SOC obtained by adding the integrated SOC to the initial SOC while integrating the charge / discharge current of the battery to obtain an integrated SOC. It is a method to make it SOC.

  Here, there are many cases where the OCV can not be measured accurately. For example, in an electric car or a hybrid car equipped with a secondary battery, when the vehicle starts to travel, no current flows even when the vehicle is stopped waiting for a signal. In other words, no load occurs and current flows in the secondary battery. Because of flow, it may not be possible to accurately measure the OCV. In this regard, in the SOC estimation method based on the OCV, when estimating the SOC, it is always necessary to measure the OCV at that time. On the other hand, in the SOC estimation method based on current integration, although it is necessary to first measure the OCV, it is not necessary to measure the OCV when estimating the SOC thereafter. That is, the SOC estimation method based on current integration is more advantageous than the SOC estimation method based on OCV in that the SOC estimation method is less susceptible to the measurement error of the OCV and the change amount of the SOC can be accurately measured.

  However, in the SOC estimation method based on current integration, if current integration is performed for a long time due to, for example, a measurement error of the current sensor, an error between the estimated SOC and the actual SOC may be integrated and increased. Therefore, the SOC estimation method based on OCV is advantageous over the SOC estimation method based on current integration, depending on the usage of the battery, in that the error between the estimated SOC and the actual SOC is not integrated.

  Then, BMS3 utilizes the estimation method which combined the SOC estimation method by electric current integration, and the SOC estimation method by OCV so that it may mention later. Specifically, this estimation method usually shifts the estimated SOC to the SOC determined by the above-described SOC estimation method by the OCV at a predetermined timing while determining the estimated SOC by the SOC estimation method by current integration. Is a method of suppressing an integration error of the SOC due to current integration.

(OCV-SOC curve of battery pack)
The OCV-SOC curve of the iron phosphate lithium ion battery is shown in FIG. 2, and a part of the OCV-SOC curve is shown enlarged in FIG. The OCV-SOC curve is information indicating the correlation between the OCV and the SOC for the battery assembly 2, and this can be determined in advance by the specifications of the battery assembly 2, predetermined experiments, or the like.

  Here, the correlation between the OCV and the SOC of the assembled battery 2 may differ depending on whether the used state of the assembled battery 2 is in a charged state or a discharged state. The graph of the dashed-dotted line in the same figure is an OCV-SOC curve at the time of charge, and the graph of a solid line is an OCV-SOC curve at the time of discharge. For this reason, even though the use state of the assembled battery 2 before the measurement of the OCV is the charge state, when the SOC is estimated from the measured value of the OCV using the OCV-SOC curve at the time of discharge, the measurement of the OCV Depending on the value, the estimated SOC may deviate greatly from the actual SOC. In addition, even though the use state of the assembled battery 2 before the measurement of the OCV is a discharge state, when the SOC is estimated from the measured value of the OCV using the OCV-SOC curve during charging, the measured value of the OCV In some cases, the estimated SOC deviates significantly from the actual SOC.

  The OCV is not limited to the voltage across the battery pack 2 in the no-current state. For example, a minute current such as dark current flows, but the amount of voltage change per unit time of the battery pack 2 is less than a specified amount It may be the voltage across the battery pack 2 when the condition is satisfied. Each graph shown in FIGS. 2 and 3 is created based on the measured value of OCV when the conditions are satisfied. Further, the specified amount can be arbitrarily determined by the specification of the battery assembly 2 or a predetermined experiment.

  In general, in a battery having a negative electrode formed of a graphitic material, the OCV-SOC curve has a wide range of minute change regions where the change amount of OCV per unit SOC is extremely small. Hereinafter, the amount of change in OCV per unit SOC is simply referred to as the OCV change rate. In the example of FIG. 2, the area of about 30% to about 64% of SOC and the area of about 68% to about 98% of SOC are flat areas of which the OCV change rate is about 0, and the OCV change is It corresponds to a minute change area where the rate is less than the reference value. The reference value can be determined arbitrarily, and the OCV change rate (for example, 0 in the example of FIG. 2) of an area other than a minute change area and a steep change area described later, such as an SOC of about 0% to about 30%. It may be .81 mV /%) or an integral multiple (preferably twice or more) of the OCV change rate. Also, the reference value is preferably 5 mV /% or less.

  Here, when the SOC is obtained from the measured value of OCV using the slight change region of the OCV-SOC curve, if the measurement error of the voltage sensor 34 is ± 5 mV, the calculated SOC is an error of ± 15%. Will be included. For this reason, it is difficult to accurately determine the SOC from the measured value of OCV in the slight change region, and it is not preferable to shift the estimated SOC determined by the SOC estimation method by current integration to the SOC determined from the measured value of OCV .

  On the other hand, in a battery having a negative electrode formed of a graphite-based material, a sharp change region, in which the OCV change rate is relatively larger than that of the small change region, exists between the two small change regions. This steep change area can be said to be an area between two inflection points. The inflection point is a point at which the OCV change rate changes by a predetermined value or more. In the example of FIG. 2, the region where the SOC is about 64% to about 68% is a slope region where the OCV change rate is large, and corresponds to a steep change region where the OCV change rate is higher than the reference value. The reason why the region of about 64% to about 68% of SOC becomes the steep change region is considered to be that the stage structure of the negative electrode formed of the graphite material changes in this region.

  In the steep change region, the OCV change rate is relatively large compared to the minute change region, so the SOC can be accurately obtained from the measured value of OCV. Therefore, when the measured value of OCV exists in the steep region, SOC is obtained from the measured value of OCV, and the estimated SOC obtained by the SOC estimation method by current integration is shifted to the SOC obtained from the measured value of OCV. Is preferred. The OCV in the steep change region is in the rated voltage range of the battery pack 2, specifically, preferably in the range of 3.2 V to 3.5 V, and more preferably in the range of 3.3 V to 3.35 V . As a result, in the normal use environment of the battery pack 2, the estimated SOC obtained by the SOC estimation method based on current integration can be shifted to the SOC obtained from the measured value of the OCV.

  In the example of FIG. 3, .DELTA.V1 is the OCV range of the steep change region at the time of charging, .DELTA.V2 is the OCV range of the steep change region at the time of discharge, and .DELTA.V3 is the region where the OCV range .DELTA.V1 and the OCV range .DELTA.V2 overlap. OCV range. Further, the SOC range Δ% is the SOC range of the steep change region. Hereinafter, a region in which the OCV is within the OCV range ΔV3 and the SOC is within the SOC range Δ% may be simply referred to as an overlapping region. As can be seen from the figure, in this overlapping region, the OCV-SOC curve at the time of charge and the OCV-SOC curve at the time of discharge are substantially parallel, and the SOC at the time of charge for the same OCV and the SOC at the time of discharge The difference is extremely small compared to the area other than the overlapping area. Therefore, in the overlapping area, only the correlation data of one OCV-SOC included in the area between the OCV-SOC curve during charging and the OCV-SOC curve during discharging is stored. ing. For example, as shown by a two-dot chain line in FIG. 3, correspondence data of the OCV within the OCV range ΔV3 and the central value of the SOC at the time of discharge and the SOC at the time of charge corresponding to the OCV is preferable.

(Battery management process)
For example, regardless of whether or not the engine of the hybrid vehicle is activated, the control unit 31 is operable by supplying power from the assembled battery 2, and repeatedly executes the battery management process shown in FIG.

  In the battery management process, the CPU 35 starts execution of the SOC integration process for obtaining the estimated SOC by the SOC estimation method based on current integration (S1), and thereafter repeatedly executes the SOC integration process at predetermined time intervals. Specifically, based on the detection signal SG1 from the current sensor 33, the CPU 35 integrates the current value I over time. The CPU 35 multiplies the integrated value of the current value I by the charging efficiency of the battery pack 2 and divides the value obtained by dividing 100 by the total capacity of the assembled battery 2 (Total Amount of Charge) and integrates 100 The current SOC value [%]. The CPU 35 determines a value obtained by adding the current value of the integrated SOC to a predetermined initial value of SOC as the current value of the estimated SOC.

  As a method of obtaining the initial value of the SOC, the CPU 35 detects the voltage value V of the voltage across the assembled battery 2 at the start of BMS 3 based on the detection signal SG2 from the voltage sensor 34, and this voltage value V If it is within the range of the OCV range ΔV 3, there is a method of obtaining the SOC corresponding to the voltage value V from the correlation data of OCV-SOC stored in the memory 36 and setting it as an initial value. Further, for example, when the BMS 3 is stopped, the CPU 35 stores the estimated SOC immediately before that in the memory 36, and when the voltage value V is out of the range of the OCV range ΔV3, the estimated SOC stored in the memory 36 is set as an initial value. It is also good.

  After starting execution of the SOC integration process, the CPU 35 determines whether the OCV detection condition is satisfied (S2), and when it is determined that the OCV detection condition is satisfied (S2: YES), measures the current value of the OCV. A voltage measurement process is performed (S3). In the present embodiment, the OCV detection condition is that the state in which the current value I of the charge / discharge current of the assembled battery 2 is less than or equal to the reference current value continues for a predetermined time. The reference current value is a current value 0 [A] in the no-load state or a value higher than the current value 0 [A] by a predetermined current value. For example, when the hybrid vehicle uses electronic components such as audio while the vehicle is at a stop, the OCV detection condition may be satisfied.

  When the current value I becomes equal to or less than the reference current value, the CPU 35 starts counting the elapsed time from that point and recording the voltage value V based on the detection signal SG2 from the voltage sensor 34 in the memory 36. When the state where current value I is less than or equal to the reference current continues for a predetermined time, CPU 35 determines that the OCV detection condition is satisfied (S2: YES), and thereafter current value I first exceeds the reference current value The voltage value V immediately before is considered as the current value of the OCV (S3). As another example of the OCV detection condition, for example, there may be mentioned that the hybrid vehicle has stopped for a predetermined time due to signal waiting or the like.

  When the current value of the OCV is measured, the CPU 35 executes an OCV determination process to determine whether the measured value of the OCV is within the overlapping area (S4). If the CPU 35 determines that the measured value of the OCV is within the overlapping area (S4: YES), the measured value of the OCV is within the steep change area, so that the SOC can be accurately determined from the measured value of the OCV. It is possible. Further, as described above, in the overlapping region, the OCV-SOC curve at the time of charge and the OCV-SOC curve at the time of discharge are substantially parallel, and the difference between the SOC at the time of charge for the same OCV and the SOC at the time of discharge Is small.

  Therefore, when the CPU 35 determines that the measured value of OCV is within the overlapping area (S4: YES), it executes the SOC adjustment processing (S5, S6). The SOC adjustment process is a process of adjusting the estimated SOC obtained by the SOC integration process based on the SOC corresponding to the measured value of the OCV. Specifically, the CPU 35 corresponds to the OCV measured value from the common OCV-SOC correlation data stored in the memory 36 regardless of whether it is currently in the charged state or the discharged state. The SOC is extracted (S5), and shift processing is performed to shift the estimated SOC obtained by the SOC integration processing to the extracted SOC (S6). As a result, it is possible to reduce the integration error accumulated in the estimated SOC obtained by the SOC integration process without determining whether it is currently in the charging state or the discharging state.

  Further, by the shift process, the CPU 35 starts to execute the SOC integration process again for the current value I of the charge / discharge current flowing after the shift process is performed. Then, the CPU 35 multiplies the integrated value of the current values I after the execution of the shift process by the charging efficiency of the battery pack 2 and divides the value obtained by dividing by the total capacity of the battery pack 2 by 100, It is assumed that the present value [%] of the integrated SOC. The CPU 35 determines a value obtained by adding the current value of the integrated SOC to the SOC extracted in S5 as the current value of the estimated SOC. In addition, after executing the SOC adjustment processing, the CPU 35 proceeds to S7.

  On the other hand, when the CPU 35 determines that the measured value of the OCV is out of the overlapping region (S4: NO), the measured value of the OCV is highly likely to be within the minute change region, and as described above, this minute change In the domain, it is difficult to accurately determine the SOC from the measured value of OCV. Therefore, the CPU 35 proceeds to S7 without performing the SOC adjustment process. At S7, the CPU 35 executes the deterioration determination process based on the obtained estimated SOC. Specifically, the CPU 35 determines that the assembled battery 2 is not degraded if the estimated SOC is within a predetermined reference range, and determines that the assembled battery 2 is degraded if the estimated SOC is out of the reference range, For example, SOC and error information are notified to an external device such as an engine control unit or charging device 40. After executing the deterioration determination process, the CPU 35 returns to S2.

(Charge control process)
The control unit 31 is operable by being supplied with power from the battery pack 2, and repeatedly executes the charge control process shown in FIG.

  Specifically, the CPU 35 executes chargeability determination processing for determining whether the state of the charging device 40 satisfies the chargeable condition (S11). The chargeable condition is a condition for the charging device 40 to be able to charge the assembled battery 2. For example, the engine of the hybrid vehicle is operating or the alternator 41 is operating. Etc.

  For example, when the engine is operating, the CPU 35 determines that the state of the charging device 40 satisfies the chargeable condition (S11: YES), and executes the SOC maintaining process (S12 to S15). The SOC maintaining process is a process for causing the charging device 40 to execute a charging operation in which the current value of the estimated SOC in the battery management process is maintained at or above the minimum value of the SOC in the sharp change region. Specifically, the CPU 35 determines whether the current value of the estimated SOC is less than the first threshold (S12). The first threshold is a value equal to or higher than the lowest value (approximately 64% in FIG. 2) of the SOC in the abrupt change region, or a value equal to or higher than the highest value (approximately 67% in FIG. 2) in the abrupt change region.

  When determining that the current value of the estimated SOC is less than the first threshold (S12: YES), the CPU 35 transmits a charge priority command to the charge control unit 42 of the charging device 40 (S13), and returns to S11. Thereby, the charge control unit 42 increases the power generation output level of the alternator 41. As a result, the charge from the alternator 41 to the assembled battery 2 is prioritized over the discharge from the assembled battery 2, and the SOC of the assembled battery 2 can be increased to a first threshold value or more.

  On the other hand, when determining that the current value of the estimated SOC is equal to or greater than the first threshold (S12: NO), the CPU 35 determines whether the current value of the estimated SOC exceeds the second threshold (S14). The second threshold is equal to or greater than the lowest SOC value in the steep change region, and is larger than the first threshold, preferably 90% or less, and more preferably 80% or less. Thus, the second threshold is preferably a value smaller than 100%. This is to suppress the overcharging of the battery assembly 2 by the regenerative power.

  When determining that the current value of the estimated SOC exceeds the second threshold (S14: YES), the CPU 35 transmits a discharge priority command to the charge control unit 42 of the charging device 40 (S15), and returns to S11. Thereby, the charge control unit 42 reduces the power generation output level of the alternator 41. Thus, the discharge from the assembled battery 2 is prioritized over the charge from the alternator 41 to the assembled battery 2, and the SOC of the assembled battery 2 can be reduced to be equal to or less than the second threshold.

  In addition, when the CPU 35 determines that the current value of the estimated SOC is equal to or less than the second threshold (S14: NO), the CPU 35 returns to S11 without transmitting the charge priority instruction or the discharge priority instruction. Thereby, the charge control unit 42 increases or decreases the power generation output level of the alternator 41 by unique control. As described above, the control unit 31 performs feedback control so that the current value of the estimated SOC is maintained between the first threshold and the second threshold while satisfying the chargeable condition. When CPU 35 determines that the current value of estimated SOC is equal to or greater than the first threshold (S12: NO), CPU 35 may return to S11 without executing the processes of S14 and S15.

  On the other hand, for example, when the hybrid vehicle stops and the engine stops, the CPU 35 determines that the state of the charging device 40 does not satisfy the chargeable condition (S11: NO), and does not execute the SOC maintaining process. Therefore, after that, the battery pack 2 is discharged by dark current or the like.

  Here, if the CPU 35 determines that the state of the charging device 40 satisfies the chargeable condition (S11: YES) and the SOC maintenance process is not executed, the battery assembly has already been completed when the engine is stopped. The SOC of 2 may be less than the minimum value of the steep change region. Then, during stoppage of the engine, the SOC does not pass through the steep change region when decreasing along the OCV-SOC curve at the time of discharge, so the shift processing is not performed and the error between the estimated SOC and the actual SOC The battery pack 1 is left as it is. In such a configuration X, for example, when the engine is reactivated and the CPU 35 again determines that the state of the charging device 40 satisfies the chargeable condition (S11: YES), the battery pack 2 is operated by the charging device 40. Is preferably forcibly charged to the minimum value or more of the steep change area to make the shift process executable.

  On the other hand, in the present embodiment, the CPU 35 executes the SOC maintaining process when it is determined that the state of the charging device 40 satisfies the chargeable condition (S11: YES). Therefore, until just before the engine is stopped, the current value of the estimated SOC is maintained at or above the lowest value of the SOC in the steep change region. Then, when the engine is stopped, the SOC can pass through the steep change area when decreasing along the OCV-SOC curve at the time of discharge, and the CPU 35 can execute the shift process. As a result, it is possible to suppress the occurrence of a situation where the battery pack 1 is not left with the error between the estimated SOC and the actual SOC occurring, without the shift processing being executed while the engine is stopped. Further, as in the above configuration A, when it is determined again that the state of the charging device 40 satisfies the chargeable condition (S11: YES), special control is performed such that the battery assembly 2 is forcibly charged by the charging device 40. It is possible to estimate the SOC accurately without performing it.

(Effect of this embodiment)
In the correlation between the OCV of the assembled battery 2 and the SOC, there is a slight change area in which the change rate of the OCV with respect to the SOC is less than the reference value and a steep change area in which the change rate is higher than the reference value. Therefore, according to the configuration of the present embodiment, on the condition that the measured value of OCV is determined to be within the steep change region, the estimated SOC obtained by the SOC integration processing is the correlation between OCV and SOC. It is shifted to the SOC corresponding to the measured value of OCV. As a result, even if the measured value of OCV is within the slight change region, the estimated SOC is actually compared with the configuration in which the estimated SOC is shifted to the SOC corresponding to the measured value of OCV in the correlation between OCV and SOC. It is possible to suppress that the error with the SOC of the above becomes larger than that before the shift.

Other Embodiments
The present invention is not limited to the embodiments described above with reference to the drawings and, for example, the following various aspects are also included in the technical scope of the present invention.

  The battery pack 1 of the said embodiment was mounted in the electric vehicle or the hybrid vehicle. However, the present invention is not limited to this, and the battery pack 1 may be mounted as a power source of an engine start motor or an auxiliary battery, for example, in an engine-driven automobile such as a conventional car.

  In the said embodiment, the assembled battery 2 was mentioned as the example as an example of an electrical storage element and a secondary battery. However, the battery is not limited to this, and may be a battery composed of one single battery, or may be a battery other than the secondary battery. In addition, an electric double layer capacitor may be used. Further, the present invention is not limited to one having a negative electrode formed of a graphite-based material. In short, in the correlation between OCV and SOC, a minute change region where the OCV change rate is less than the reference value, and the OCV change rate is the reference value It is sufficient if the storage element has at least one steep change area higher than the other.

  In addition, in the correlation between OCV and SOC, it is sandwiched between two slight change regions where the OCV change rate is less than or equal to the reference value and the two slight change regions, and the OCV change rate is steeper than the reference value. It is more preferable if it is an electrical storage element in which a change area exists. Furthermore, it is more preferable if it is a storage element in which a plurality of steep regions sandwiched by two minute change regions exist. As a result, the SOC can be accurately estimated from the measured value of OCV in many areas, and the SOC determined by the SOC estimation method using OCV is determined as the estimated SOC despite the fact that it is different from the actual SOC. Can be effectively suppressed.

  Furthermore, the plurality of steep regions are all within the rated voltage range of the battery pack 2, specifically, preferably within the range of 3.2 V to 3.5 V, and more preferably within the range of 3.3 V to 3.35 V . In addition, the manufacturing method of such an electrical storage element is disclosed by Unexamined-Japanese-Patent No. 2007-250299, for example. At this time, the positive electrode active material may be mixed to make the positive electrode, or the positive electrode may be made without mixing the positive electrode active material.

  The positive electrode active material is not limited to iron phosphates, and may be other complex oxides such as manganese phosphates and cobalt phosphates. Further, the positive electrode active material is not limited to the phosphoric acid type, and may be a positive electrode active material containing no phosphoric acid, such as lithium cobaltate. For example, in the above embodiment, since the potential of the graphite negative electrode (OCP: Open Circuit Potential) changes stepwise around SOC 60%, a steep region is generated. Therefore, the type of positive electrode is not particularly limited.

  In the above embodiment, the control unit 31 having one CPU and a memory is taken as an example of the control unit. However, the control unit is not limited to this, and may have a configuration including a plurality of CPUs, a configuration including a hardware circuit such as an application specific integrated circuit (ASIC), or a configuration including both a hardware circuit and a CPU. For example, at least two of the SOC integration process, the voltage measurement process, the OCV determination process, and the SOC adjustment process may be executed by separate CPUs and hardware circuits. Also, the order of these processes may be changed as appropriate.

  In the above embodiment, the memory 36 provided inside the control unit 31 is taken as an example of the memory. However, the memory is not limited to this, and may be provided outside the control unit 31. The medium in which the various programs described above are stored may be a non-volatile memory such as a CD-ROM, a hard disk device, a flash memory, etc. in addition to the RAM and the like.

  In the above embodiment, as an example of the voltage measurement process for measuring the OCV, the voltage value V at the time of becoming close to no load is detected and used as the current value of the OCV. However, the voltage measurement process is not limited to the process of measuring the OCV, but may be a process of calculating the current value of the OCV using the measured voltage value and other parameters. For example, the control unit 31 may be configured to calculate the current value of the OCV from the voltage value V of the assembled battery 2, the current value I, and the resistance value obtained in advance. With this configuration, it is possible to measure the current value of the OCV regardless of whether or not the battery pack 2 is close to the no-load state. In short, in the voltage measurement process, various known OCV measurement methods can be used.

  In the above embodiment, a configuration in which the correspondence relationship data between the OCV within the OCV range ΔV3 and the center value of the SOC during discharge and the SOC during charge corresponding to the OCV is stored in the memory 36 is taken as an example. . However, the present invention is not limited to the central value, and even in the configuration in which the correspondence relationship data between the OCV within the OCV range ΔV3 and the SOC at the time of discharge and the SOC at the time of charge corresponding to the OCV is stored in the memory 36 Good. However, with the configuration of the above embodiment, the SOC can be measured from the measured value of OCV with almost the same accuracy during charging and discharging.

  Alternatively, the memory 36 may store the correlation data of the OCV-SOC in the sharp change region at the time of charge and the correlation data of the OCV-SOC in the sharp change region at the time of discharge. In this configuration, the control unit 31 determines whether it is currently in the charging state or the discharging state based on the detection result of the direction of the charge / discharge current, the instruction signal from the charging device 40, etc. When it determines with, the correlation data of OCV-SOC at the time of charge are utilized, and when it determines with it being discharge state, the structure using the correlation data of OCV-SOC at the time of discharge is preferable. However, with the configuration of the above embodiment, it is not necessary to determine whether it is in the charge state or the discharge state, and the correlation data of both OCV-SOC at the time of discharge and at the time of charge is stored in the memory 36. Memory usage can be reduced because it is not necessary to

  The control unit 31 may be configured to estimate the SOC of one battery cell C constituting the assembled battery 2. In this case, the control unit 31 uses the OCV-SOC curve for one battery cell C. The control unit 31 may divide, for example, the OCV of the entire assembled battery 2 by the number of battery cells C configuring the assembled battery 2 and set the value after the division as the OCV for one battery cell C. Further, a voltage sensor for individually detecting the cell voltage of each battery cell C is provided in BMS 3, and the control unit 31 calculates, for example, the maximum value and the average value of the cell voltages of the plurality of battery cells C Therefore, the OCV for one battery cell C may be obtained.

  As described above, in the overlapping region, since the OCV-SOC curve at the time of charge and the OCV-SOC curve at the time of discharge are substantially parallel, the difference between the SOC at the time of charge for the same OCV and the SOC at the time of discharge is It is constant. Therefore, if the correlation data of only one of the OCV-SOC at the time of discharge and charge and the value data of the difference are stored in the memory 36, both the OCV-SOC at the time of discharge and charge are stored. Compared to the configuration in which the correlation data of the above is stored in the memory 36, the memory usage can be reduced.

  In the above embodiment, the current value I of the charge / discharge current flowing in the assembled battery 2 is taken as an example of the variable element of the storage element different from the OCV. However, the variable factor is not limited to this, and may be, for example, voltage, current, temperature of the storage element, use time of the storage element, etc. at the time of engine start (cranking) of an engine-driven automobile Thus, the SOC can be estimated.

  For example, when the battery pack 2 is charged by an external battery charger, a solar panel, or the like when the engine is stopped, the control unit 31 determines that the current value of the estimated SOC is the highest SOC in the steep change region during engine startup. The charging device 40 may be configured to execute the charging operation to be maintained below. In this case, in FIG. 5, the first threshold and the second threshold are equal to or less than the highest value of the SOC in the sharp change region, or less than the lowest value of the SOC in the sharp change region.

  Then, when the engine is stopped, the SOC can pass through the steep change region when rising along the OCV-SOC curve at the time of charge, and the CPU 35 can execute the shift process. As a result, when the engine is stopped, the SOC of the battery pack 2 has already exceeded the highest value in the steep change area, and when the SOC rises along the OCV-SOC curve during charge, the steep change area The shift process is not executed without passing through the path, and it is possible to suppress the situation where the battery pack 1 is left with the error between the estimated SOC and the actual SOC occurring. In other words, after the hybrid vehicle stops, when charging by solar power generation, etc., the SOC passes through a sharp change region, so shift processing is performed without performing any special control such as forced charge / discharge. It is possible to accurately estimate the SOC.

  Note that the control unit 31 may be configured to cause the charging device 40 to perform a charging operation that maintains the current value of the estimated SOC above the minimum value and the maximum value of the SOC in the steep change region during engine startup. The OCV is not limited to the voltage across the battery pack 2 in the no-current state. For example, a minute current such as dark current flows, but the amount of voltage change per unit time of the battery pack 2 is less than a specified amount It may be the voltage across the battery pack 2 when the condition is satisfied.

  In the battery management process, when the control unit 31 proceeds to S2 without executing the SOC integration process (S1) and determines that the measured value of the OCV is within the overlapping area (S4: YES), it becomes the measured value of the OCV. After extracting the corresponding SOC (S5), instead of the shift processing S6, the extracted SOC may be determined as the estimated SOC, and the process may proceed to S7.

  If the control unit 31 determines that the measured value of the OCV is not within the overlapping area (S4: NO), the control unit 31 may be configured to prohibit determining the SOC corresponding to the measured value of the OCV as the estimated SOC. That is, as shown in FIG. 4, the control unit 31 is not limited to the configuration in which the extraction itself of the SOC corresponding to the measured value of the OCV is not performed. The control unit 31 extracts the SOC corresponding to the measured value of the OCV, but the extracted SOC may not be determined as the estimated SOC.

  1: Battery pack 2: assembled battery 3: BMS 31: control unit 33: current sensor 34: voltage sensor 36: memory

Claims (10)

In the correlation between OCV and SOC, the voltage of a storage element in which a slight change region in which the change rate of the OCV with respect to the SOC is less than a reference value and a steep change region in which the change rate is higher than the reference value Voltage sensor to detect,
A memory in which at least information on the correlation between the OCV and the SOC in the steep change area is stored;
And a control unit,
The control unit
A voltage measurement process of measuring an OCV of the storage element based on a detection result of the voltage sensor;
OCV determination processing for determining whether the measured value of OCV measured by the voltage measurement processing is within the steep change region;
If it is determined in the OCV determination process that the measured value of the OCV is within the steep change region, the SOC corresponding to the measured value of the OCV is determined as the estimated SOC based on the information stored in the memory, SOC estimation processing for prohibiting the SOC corresponding to the measured value of the OCV to be estimated SOC when it is determined in the OCV determination process that the measured value of the OCV is not within the steep change region;
Charge availability determination processing for determining whether the charging device is capable of charging the storage element or not;
The SOC maintenance that causes the charging device to execute a charging operation that maintains the SOC estimated in the SOC estimation process at or above the minimum value of the SOC in the sharp change region when it is determined that the charging device is in the chargeable state have a structure to perform processing and, the,
The storage element is for a vehicle having at least an engine in a drive source,
The control unit executes the SOC maintenance process by controlling charge / discharge by adjusting the power generation output of the alternator of the vehicle during engine operation, and sets the SOC of the storage element immediately before the engine is stopped within the steep change region. Storage element management device to maintain . The storage element management device according to claim 1, wherein
The storage element management device, wherein the control unit causes the charging device to execute a charging operation of maintaining the SOC estimated in the SOC estimation process at or below a maximum value of the SOC in the abrupt change region in the SOC maintenance process. The storage element management apparatus according to claim 1 or 2, wherein
The control unit is configured to maintain the SOC of the storage element immediately before the charging device switches from the chargeable state to the non-chargeable state by execution of the SOC maintenance process, at a minimum value of the steep change region or more. Management device. The storage element management device according to any one of claims 1 to 3 , wherein
In the correlation between the OCV and the SOC, a storage element management device in which two small change areas sandwiching the rapid change area exist. The storage element management device according to any one of claims 1 to 4 , wherein
The storage element management device, wherein OCV of the steep change area is within a rated voltage range of the storage element. The storage element management device according to any one of claims 1 to 5 , wherein
The control unit
It has a configuration that executes acquisition processing for acquiring the value of the variable element of the storage element that has a correlation with the SOC and is different from the OCV,
In the SOC estimation process, when it is determined in the OCV determination process that the measured value of the OCV is not within the steep change region, SOC is determined as an estimated SOC based on the value of the variable element acquired in the acquisition process. Element management device. The storage element management device according to claim 6 , wherein
A current sensor that detects a current flowing through the storage element;
The control unit
As the acquisition processing, SOC integration processing for obtaining an estimated SOC by current integration that integrates the current flowing through the storage element over time based on the detection result of the current sensor is executed,
In the SOC estimation process, on the condition that the measured value of the OCV is determined to be within the steep change region in the OCV determination process, the estimated SOC obtained in the SOC integration process is the OCV and the SOC. The storage element management device, which is configured to shift to the SOC corresponding to the measured value of the OCV in the correlation of In correlation between OCV and SOC, SOC estimation of a storage element in which a slight change region in which the change rate of the OCV with respect to the SOC is less than or equal to a reference value, and a steep change region in which the change rate is higher than the reference value Method,
A voltage measurement step of measuring an OCV of the storage element;
An OCV determination step of determining whether the measured value of the OCV measured in the voltage measurement step is within the steep change region;
If it is determined in the OCV determination step that the measured value of the OCV is within the abrupt change area, the OCV is measured based on the information on the correlation between the OCV and the SOC within the abrupt change area stored in the memory. If the SOC corresponding to the value is determined as the estimated SOC, and it is determined in the OCV determination step that the measured value of the OCV is not within the steep change region, the SOC corresponding to the measured value of the OCV is determined as the estimated SOC. SOC estimation process that prohibits
A charge availability determination step of determining whether the charging device is capable of charging the storage element or not;
SOC maintenance for causing the charging device to execute a charging operation to maintain the SOC estimated in the SOC estimation step at least the minimum value of the SOC in the steep change region when it is determined that the charging device is in the chargeable state and the process, only including,
The storage element is for a vehicle having at least an engine in a drive source,
During operation of the engine, the SOC maintaining step is executed by controlling charge / discharge by adjusting the power generation output of the alternator of the vehicle to maintain the SOC of the storage element just before the engine is stopped within the steep change region SOC estimation method. It is the SOC estimation method of the electrical storage element of Claim 8 , Comprising:
A method of estimating SOC of a storage element, which causes the charging device to execute a charging operation of maintaining the SOC estimated in the SOC estimation process below the maximum value of the SOC in the steep change region in the SOC maintaining step. A method of estimating SOC of a storage element according to claim 8 or 9 , wherein
A method of estimating SOC of a storage element, wherein the SOC of the storage element immediately before the charging device switches from the chargeable state to the non-chargeable state is maintained at or above the minimum value of the steep change region by execution of the SOC maintenance step.

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