JP6413763B2 - Charge state detection device, charge state detection method, mobile object - Google Patents

Description

  The present invention relates to a charge state detection device, a charge state detection method, and a moving object.

  An electricity storage device typified by a lithium ion secondary battery is used in various devices. However, since the input / output performance varies depending on the state of charge, a more accurate state of charge estimation technique is required. Therefore, the state of charge is estimated using various methods.

  As an example, a battery of a lithium ion secondary battery having a plurality of inflection points showing a change in which the correlation between the battery voltage and the remaining capacity becomes clear between 10% to 90% of the remaining capacity indicating the remaining battery energy A capacity detection device can be mentioned.

  The battery capacity detecting device includes a voltage detecting means for detecting a voltage of the battery and a voltage change rate, an inflection point detecting means for detecting a point where the voltage change rate exceeds a predetermined threshold as an inflection point, and a charge / discharge current of the battery. Current integrating means for integrating as a current integrated value. Then, when the inflection point is detected, it is determined which of the plurality of inflection points is based on the current accumulated value accumulated by the current accumulating means, and the battery capacity corresponding to the inflection point is determined as the inflection point. It searches from the table | surface with which battery capacity was matched, and it is set as 1st battery capacity.

  Also, the current integrated value in the current integrating means from the time of detecting the inflection point to the time when the voltage detected by the voltage detecting means becomes the fully charged voltage is defined as the second battery capacity, and the second battery capacity and the first battery Add the capacity to get the full charge capacity.

  However, in the above technique, it is said that the full charge capacity can be accurately obtained, but the state of charge in a state where a load is connected is not considered.

  The present invention has been made in view of the above, and provides a state-of-charge detection device capable of measuring a state of charge in a state where a load is connected.

  The charge state detection device is a charge state detection device that detects a charge state of an electricity storage device in a state where a load is connected, and a first supply of current for constant current charging of the electricity storage device from a charging unit is started. A voltage detection unit that detects a first voltage of the power storage device at a time point and a second voltage of the power storage device at a second time point before the full charge is stopped when the supply of the current is stopped; A voltage change amount detection unit that detects a voltage change amount by subtracting the first voltage from a second voltage, and a charge state detection that detects a charge state of the power storage device based on the first voltage and the voltage change amount It is a requirement to have a part.

  According to the disclosed technology, it is possible to provide a charge state detection device that can measure a charge state in a state where a load is connected.

1 is a schematic configuration diagram of a hybrid vehicle to which a charging state detection device according to a first embodiment is applied. It is a figure which illustrates the charging rate vs. voltage characteristic of the battery which concerns on 1st Embodiment. It is a figure which illustrates the functional block of the battery control unit which concerns on 1st Embodiment. It is an example of the flowchart which shows the method of the charge condition estimation which concerns on 1st Embodiment. It is a figure which illustrates the charging rate vs. voltage characteristic before and behind deterioration of a battery. It is a figure which illustrates the functional block of the battery control unit which concerns on 2nd Embodiment. It is an example of the flowchart which shows the method of the deterioration estimation which concerns on 2nd Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted. In each embodiment, as an example, a charge state detection device capable of detecting the charge state of a battery mounted on a hybrid vehicle with high accuracy will be described.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of a hybrid vehicle to which a charging state detection apparatus according to a first embodiment is applied. In FIG. 1, the battery pack 10 includes a battery 11 and a monitor unit 12. Note that the battery pack 10 only needs to include at least one battery 11, but two or more batteries 11 may be connected in series or in parallel for higher output.

  The battery 11 is a chargeable / dischargeable battery. As the battery 11, for example, a lithium ion battery or the like can be used. The monitor unit 12 has a function of monitoring the state of the battery 11. The monitor unit 12 may include a voltage sensor, a current sensor, a temperature sensor, and the like. The battery 11 is a typical example of the electricity storage device according to the present invention.

  The engine 20 is a well-known internal combustion engine that uses gasoline, light oil, or the like as fuel. The motor 30 is a known generator motor that functions as a motor and a generator. The battery 11 plays a role of supplying electric power when the motor 30 functions as an electric motor and a role of storing regenerative energy when the motor 30 functions as a generator.

  In hybrid vehicles including PHEV (Plug-in Hybrid Electric Vehicle) and HEV (Hybrid Electric Vehicle), the engine 20 and the motor 30 are used in combination. The vehicle travels with at least one of the power output from the engine 20 and the power output from the motor 30.

  The system control unit 40 switches between an EV mode (first mode) that operates only with the power of the motor 30 and an HEV mode (second mode) that operates using both the power of the motor 30 and the power of the engine 20. An ECU (Electronic Control Unit) configured to be controllable. The system control unit 40 may be configured to be able to perform various other controls such as control of charging the battery 11 and control of regenerative operation.

  The system control unit 40 can be configured to include, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a main memory, and the like. In this case, various functions of the system control unit 40 can be realized by reading a program recorded in the ROM or the like into the main memory and executing it by the CPU. The CPU of the system control unit 40 can read and store data from the RAM as necessary. The system control unit 40 is a typical example of a control unit according to the present invention.

  The battery control unit 50 has a function of managing and controlling the charge / discharge state of the battery 11 and charges the battery 11 via the charging unit 60. The battery control unit 50 has a function of detecting the state of charge of the battery 11. When the hybrid vehicle is a PHEV, the charging unit 60 is provided with an external power plug 65, and can be directly charged by inserting the external power plug 65 into an outlet.

  The battery control unit 50 may be configured to include, for example, a CPU, ROM, RAM, main memory, and the like. In this case, various functions of the battery control unit 50 can be realized by reading a program recorded in the ROM or the like into the main memory and executing it by the CPU. The CPU of the battery control unit 50 can read and store data from the RAM as necessary. The system control unit 40 and the battery control unit 50 are configured to be able to transmit and receive data to and from each other by a CAN (Controller Area Network) or the like.

  However, a part of the functions of the battery control unit 50 may be performed by the system control unit 40, or a part of the functions of the system control unit 40 may be performed by the battery control unit 50. Further, the system control unit 40 and the battery control unit 50 may be physically realized as one ECU, or may be realized as three or more ECUs.

  Here, the relationship between the charging rate and the voltage of the battery 11 will be described. In the battery 11 according to the present embodiment, a single active material may be used for the positive electrode or the negative electrode, but an electrode in which an active material having different output characteristics with respect to the battery voltage is used for the positive electrode or the negative electrode is used. Also good. In the following description, an example in which an electrode in which an active material having different output characteristics with respect to the battery voltage is mixed in the battery 11 is used in the battery 11 will be described.

  FIG. 2 is a diagram illustrating the charging rate versus voltage characteristics of the battery according to the first embodiment. In the battery 11 having the characteristics shown in FIG. 2, an active material having a large voltage gradient and an active material having a small voltage gradient are mixed in a positive electrode or a negative electrode. In this case, since different active materials are only mixed and do not chemically react, the input / output of ions at each voltage during charge / discharge appears as a material-specific characteristic in the charge characteristics.

  Therefore, as shown in FIG. 2, the charging rate versus voltage curve showing the relationship between the state of charge (charging rate) and the voltage includes a plurality of regions with different voltage changes. Specifically, in the example of FIG. 2, a relatively flat B region and D region, and a relatively large slope A region, C region, and E region appear, and a simple reduction characteristic or the like does not occur.

The battery 11 having the characteristics shown in FIG. 2 can be realized by, for example, a non-aqueous solvent storage element in which two or more materials capable of inserting and removing lithium ions having different voltage gradients are mixed in the positive electrode or the negative electrode. In this case, one of the positive electrode materials is, for example, lithium vanadium phosphate having Li ₃ V ₂ (PO ₄ ) ₃ as a basic skeleton or a similar compound in which a part of the structure of the lithium vanadium phosphate is modified (hereinafter, Called lithium vanadium phosphate).

  In the battery 11, it is extremely important to accurately detect the state of charge of the battery, for example, to accurately detect SOC (State Of Charge). For example, when the system control unit 40 switches from the EV mode to the HEV mode based on the detection result of the SOC, if the SOC cannot be detected accurately, the mode is switched with an incorrect SOC different from the original specification. Become. As a result, the output characteristics in the HEV mode may not be sufficiently ensured, or the running performance as a hybrid vehicle may be impaired.

  Therefore, in the present embodiment, the SOC is accurately detected by the following method. The SOC detection method according to the present embodiment will be described with reference to the functional block diagram of the battery control unit shown in FIG. 3, the flowchart shown in FIG. Note that the battery control unit 50 shown in FIG. 3 is a typical example of the state-of-charge detection device according to the present invention.

First, in step S101 of FIG. 4, the voltage detection unit 51 of the battery control unit 50 determines whether or not the voltage of the battery 11 has reached the predetermined voltage V ₀ and determines that it has not reached ( In the case of No), the process of step S101 is repeated. On the other hand, if it is determined that it has been reached (in the case of Yes), the process proceeds to step S102.

  Next, in step S102, the charging state estimation unit 52 of the battery control unit 50 roughly estimates the current SOC of the battery 11. Specifically, the charge state estimation unit 52 reads, for example, a table indicating the relationship between the voltage and the SOC stored in the storage unit 56, and the battery detected by the voltage detection unit 51 based on the read table. An SOC corresponding to a voltage of 11 is estimated.

  Next, in step S103, the communication unit 53 of the battery control unit 50 sends information that the precise detection of the SOC is started to the system control unit 40, and requests the system control unit 40 to start supplying charging current. Then, the system control unit 40 that has received the request from the communication unit 53 starts constant current charging of the battery 11 via the charging unit 60. The current supplied from the charging unit 60 can be a pulse current, for example. Then, the communication unit 53 requests the system control unit 40 to stop supplying the charging current at a predetermined timing before reaching full charge.

  In the present embodiment, since the purpose is to detect the state of charge of the battery 11 at a predetermined time point, in step S103, the battery 11 is not charged to full charge, but is limited to the charge characteristics of the battery 11. Charge only the specified range.

Next, in step S <b> 104, the voltage detection unit 51 of the battery control unit 50 detects the voltage before and after charging the battery 11. Specifically, the voltage (first voltage) at the start of charging of the battery 11 (first time point at which current supply is started) is V ₁ , and at the end of charging (second time point at which current supply is stopped). If the voltage (second voltage) is V ₂ , the voltage detection unit 51 detects the voltages V ₁ and V ₂ . The voltage change amount detection unit 54 detects the voltage change amount ΔV = V ₂ −V ₁ during constant current charging of the battery 11. The voltages V ₁ and V ₂ are lower than the predetermined voltage V ₀ .

Next, in step S105, the charging state detector 55 of the battery control unit 50, based on the voltage _{V 1} and the voltage change amount ΔV detected in step S104, detects the SOC of the battery 11. Specifically, for example, data (table or the like) indicating the relationship between the SOC of the battery 11 and the voltage and voltage change amount is stored in the storage unit 56. The data indicating the relationship between the SOC, the voltage, and the voltage change amount can be, for example, data every time the SOC changes by about 2 to 5%. The charging state detecting section 55, a voltage V ₁ and the voltage change amount ΔV detected by comparing the data stored in the storage unit 56, SOC corresponding to the voltage V ₁ and the voltage change amount ΔV Is detected. Thereby, the current charging state of the battery 11 can be detected.

表１は、記憶部５６に記憶するテーブルの一例である。例えば、ステップＳ１０４で検出した電圧Ｖ_１が３．８（Ｖ）、電圧変化量ΔＶが０．０３（Ｖ）であれば、表１より、ＳＯＣ＝８０％と検出することができる。この方法では、電圧Ｖ_１がほぼフラットな領域（例えば、電圧Ｖ_１＝３．８（Ｖ）近傍の領域）でもＳＯＣを正確に測定することができる。なお、表１の１つのΔＶを測定するための充電時間（第１時点から第２時点までの時間）は任意に設定できるが、例えば、０．１ｓ〜３０秒程度とすることができる。

Table 1 is an example of a table stored in the storage unit 56. For example, voltages _{V 1} detected in step S104 is 3.8 (V), if the voltage change amount [Delta] V 0.03 (V), can be seen from Table 1, to detect the SOC = 80%. In this method, the SOC can be accurately measured even in a region where the voltage V ₁ is substantially flat (for example, a region in the vicinity of the voltage V ₁ = 3.8 (V)). Note that the charging time (time from the first time point to the second time point) for measuring one ΔV in Table 1 can be arbitrarily set, and can be set to about 0.1 s to 30 seconds, for example.

  At this time, it is preferable to store a plurality of data (for example, a plurality of tables) corresponding to the temperature of the battery 11 and indicating the relationship between the SOC, the voltage, and the voltage change amount in the storage unit 56. Thereby, the charging state detection unit 55 detects the temperature of the battery 11 based on the information monitored by the monitor unit 12, and reads the data corresponding to the current temperature from the storage unit 56, thereby improving the SOC detection accuracy. it can.

Here, the voltage V _{0 in} step S101 is preferably the B region or the D region in FIG. 2, but may be the A region, the C region, or the E region. In particular, the method of FIG. 4 is effective for accurately detecting the SOC in the relatively flat B region or D region.

A plurality of voltages may be set in the same area from the A area to the E area. That is, the voltage change amount ΔV may be measured a plurality of times. For example, the voltage detection unit 51 detects voltages V ₁ , V ₂ , V ₃ in the same region or different regions, and the voltage change amount detection unit 54 ΔV ₁ = V ₂ −V ₁ , ΔV ₂ = V ₃ −V _2. , And the SOC of the battery 11 can be detected based on the voltages V ₁ and V ₂ and the voltage changes ΔV ₁ and ΔV ₂ .

  A plurality of voltages may be set over different regions. In this case, in step S103, the current supply is started at a predetermined voltage on the low charge rate side from any inflection point that is the boundary between the regions in FIG. 2, and the high charge rate side from this inflection point is started. When charged to a predetermined voltage, supply of current is stopped. Thereby, since charging is performed across any inflection point, it is possible to detect a point where the amount of voltage change greatly changes. As a result, the current state of charge of the battery 11 can be accurately detected.

  As described above, in the first embodiment, the battery 11 is charged for a very limited predetermined time, and the voltage before and after charging and the voltage change amount before and after charging are measured. At this time, as in the conventional charge state detection method, charging is not performed with a random current but constant current charging, so that the voltage and the amount of voltage change can be accurately measured even when a load is connected. As a result, even when the load is connected, the state of charge (SOC) can be accurately detected based on the measured voltage and the amount of voltage change.

<Second Embodiment>
In the second embodiment, an example in which the state of charge detection device has a battery deterioration estimation function is shown. In the second embodiment, description of the same components as those of the already described embodiments may be omitted.

When the battery 11 uses an electrode mixed with active materials having different output characteristics with respect to the battery voltage,
Due to the difference in the deterioration rate depending on the type of the active material, the charging rate versus voltage characteristics of the battery 11 according to the present embodiment and the initial state after deterioration are, for example, as shown in FIG. The solid lines (A region, B region, C region, D region, and E region) in FIG. 5 illustrate the initial charging rate (before deterioration) of the battery 11 versus voltage characteristics.
Also, the broken lines (A ′ region, B ′ region, C ′ region, D ′ region, E ′ region) in FIG. 5 illustrate the charge rate versus voltage characteristics after the battery 11 is deteriorated.

  In the example of FIG. 5, in the B region and the D region where the characteristics of the active material that is relatively difficult to deteriorate appear, the charging rate (width of the flat region) hardly changes before and after the deterioration. On the other hand, in the A region, the C region, and the E region in which the characteristics of the active material that is relatively easily deteriorated, the charging rate decreases with the deterioration (the increase in internal resistance increases the slope and the width). decreasing).

  As described above, the battery 11 including the electrodes including a plurality of active materials having different deterioration rates has a region depending on the characteristics of the active material having a high deterioration rate in the charging rate versus voltage curve, and the characteristics of the active material having a low deterioration rate. Depending on the area. Therefore, when deterioration progresses, the active material that is relatively easy to deteriorate deteriorates first, and the capacity of the region depending on the characteristics of the active material becomes smaller than the initial capacity. And the contribution to the characteristic of each active material changes with battery voltages.

  Therefore, the deterioration state of the battery 11 can be estimated from the characteristic change before and after the deterioration of the charging rate versus voltage curve of the battery 11. Specifically, the deterioration state of the battery 11 can be estimated by the following method.

  With reference to the functional block diagram of the battery control unit shown in FIG. 6, the flowchart shown in FIG. 7, and the like, a method for estimating the deterioration state of the battery 11 according to the present embodiment will be described. In addition, the battery control unit 50 shown in FIG. 6 is a typical example of the charge state detection apparatus according to the present invention.

First, similarly to steps S101 to S104 of the first embodiment, the voltage detection unit 51 of the battery control unit 50 detects the voltages V ₁ and V ₂ before and after the battery 11 is charged. The voltage change amount detection unit 54 detects the voltage change amount ΔV = V ₂ −V ₁ during constant current charging of the battery 11.

Next, in step S205, the deterioration state detecting unit 57 of the battery control unit 50, based on the voltage _{V 1} and the voltage change amount ΔV detected in step S104, detects (estimates) the deterioration state of the battery 11. Specifically, the storage unit 56 stores data (table or the like) indicating the relationship between the SOC of the battery 11 before deterioration (initial), the voltage and the voltage change amount, and the SOC, voltage, and voltage change of the battery 11 after deterioration. Data (table or the like) indicating the relationship with the quantity is stored. Then, the deterioration state detecting unit 57 includes a voltage V ₁ and the voltage change amount ΔV detected, and by comparing the before and after degradation which has been stored in the storage unit 56 data, detecting the deterioration state of the current of the battery 11 can do.

  Thus, in the second embodiment, the deterioration state of the battery can be detected. At this time, as in the first embodiment, the voltage and the voltage change amount are measured after the constant current charging, and therefore the voltage and the voltage change amount can be accurately measured even when the load is connected. As a result, even when the load is connected, it is possible to accurately detect the deterioration state based on the measured voltage and the amount of voltage change.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

  For example, in the above-described embodiment, an example in which the charge state detection device according to the present invention is applied to a battery (particularly, a lithium ion battery) has been described. However, the charging state detection apparatus according to the present invention can be applied to various power storage devices including rechargeable batteries other than lithium ion batteries, capacitors such as electric double layer capacitors, and the like.

  In the above embodiment, the description has been given using PHEV or HEV as an example of a moving body on which the charging state detection device according to the present invention can be mounted. However, the moving body is not limited to PHEV or HEV, and may be a locomotive or a motorcycle that can travel using an electricity storage device, for example. In addition, the moving body may be a transport robot used in a factory or the like that can travel using the power storage device. In addition, the moving object is an assembly robot in which the entire object does not move but only a part moves, for example, an assembly robot arranged on a production line in a factory and capable of operating an arm or the like using a power storage device. Also good.

DESCRIPTION OF SYMBOLS 10 Battery pack 11 Battery 12 Monitor unit 20 Engine 30 Motor 40 System control unit 50 Battery control unit 51 Voltage detection part 52 Charging state estimation part 53 Communication part 54 Voltage change amount detection part 55 Charging state detection part 56 Storage part 57 Deterioration state detection 60 Charger 65 External power plug

Japanese Patent No. 5282789

Claims (10)

A charge state detection device for detecting a charge state of an electricity storage device in a state where a load is connected,
A first voltage of the electricity storage device at a first time when supply of a current for constant current charging of the electricity storage device from the charging unit is started, and a second time before reaching full charge when the supply of the current is stopped. A voltage detector for detecting the second voltage of the electricity storage device at
A voltage change amount detection unit for detecting a voltage change amount by subtracting the first voltage from the second voltage;
A charge state detection unit configured to detect a charge state of the power storage device based on the first voltage and the voltage change amount; A storage unit for storing data indicating a relationship between a charge state of the power storage device and a voltage;
The charge state detection device according to claim 1, wherein the charge state detection unit detects the charge state of the power storage device by comparing the first voltage and the voltage change amount with the data.   The charge state detection apparatus according to claim 1 or 2, wherein a charge rate vs. voltage curve indicating a relationship between a charge rate and a voltage of the power storage device includes a plurality of regions having different voltage changes. A communication unit that requests start and stop of the supply of the current;
When the voltage of the power storage device is a predetermined voltage on a lower charging rate side than the inflection point that is a boundary of the region, the communication unit requests the start of the supply of the current, and based on the request, the first At that time, the supply of current starts,
When the voltage of the power storage device is charged up to the second voltage on the higher charging rate side than the inflection point, the communication unit requests to stop the supply of the current, and based on the request, the first The charging state detection device according to claim 3, wherein the supply of the current is stopped at two time points.   5. The charge state detection device according to claim 3, wherein two or more materials capable of removing and inserting lithium ions having different voltage gradients are mixed in the positive electrode or the negative electrode of the electricity storage device. The positive electrode material of the electricity storage device includes lithium vanadium phosphate having Li ₃ V ₂ (PO ₄ ) ₃ as a basic skeleton or a similar compound obtained by modifying a part of the structure of the lithium vanadium phosphate. The charging state detection device according to claim 5.   The charge state detection device according to claim 1, further comprising a deterioration state detection unit that estimates a deterioration state of the power storage device based on the first voltage and the voltage change amount.   A mobile unit comprising: the power storage device; the charging unit; a motor that operates with electric power supplied from the power storage device; an engine; and a charge state detection device according to any one of claims 1 to 7.   Based on the detection result of the state-of-charge detection device, switching between a first mode that operates only with the power of the motor and a second mode that operates using both the power of the motor and the power of the engine is controlled. The mobile body according to claim 8, further comprising a control unit that performs the control. A charge state detection method for detecting a charge state of an electricity storage device in a state where a load is connected,
A first voltage of the electricity storage device at a first time when supply of a current for constant current charging of the electricity storage device from the charging unit is started, and a second time before reaching full charge when the supply of the current is stopped. Detecting a second voltage of the electricity storage device at:
Subtracting the first voltage from the second voltage to detect a voltage change amount;
Detecting the state of charge of the electricity storage device based on the first voltage and the amount of voltage change.

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