KR102662549B1 - METHOD FOR ESTIMATION OF LiFePO4 BATTERY CAPACITY RETENTION USING HIGH VOLTAGE INFORMATION, RECORDING MEDIUM AND DEVICE FOR PERFORMING THE METHOD - Google Patents

Abstract

The capacity estimation method based on the full charge voltage section of the iron phosphate battery is the full charge voltage (HV; High Voltage) section, which is the voltage section from the point where discharge begins after full charge of the iron phosphate battery to the point where the voltage changes beyond a pre-specified range after discharge. specifying; Measuring the length of high voltage period (LHP) of the iron phosphate battery in the full charge voltage section; Generating a capacity estimation model using characteristic values according to each capacity of the iron phosphate battery as input; and estimating the capacity of the iron phosphate battery based on characteristic values measured in the full charge voltage section of the iron phosphate battery using the generated capacity estimation model. Accordingly, since LHP is measured and used only in the full charge voltage (HV; High Voltage) section, the reliability of battery capacity estimation can be increased without being significantly affected by the user's usage pattern.

Description

Method for estimating capacity based on full charge voltage section of iron phosphate battery, recording medium and device for performing the same {METHOD FOR ESTIMATION OF LiFePO4 BATTERY CAPACITY RETENTION USING HIGH VOLTAGE INFORMATION, RECORDING MEDIUM AND DEVICE FOR PERFORMING THE METHOD}

The present invention relates to a method for estimating capacity based on the full charge voltage section of an iron phosphate battery, and a recording medium and device for performing the same. More specifically, the present invention relates to a method for estimating capacity based on the full charge voltage section, and more specifically, to designate a voltage section to estimate capacity based on the point at which discharge begins after full charge. It concerns a technology to indirectly estimate the capacity of an iron phosphate battery.

Because vehicles using fossil fuels have a serious impact on air pollution and other pollution, recently, electric vehicles (EV; Electric Vehicle) or hybrid electric vehicles (HEV; Hybrid Electric Vehicle), which generate little pollution, have been developed and commercialized. there is.

These electric vehicles or hybrid electric vehicles are configured to drive using electrical energy output from a battery built into the vehicle body. In addition, batteries used in devices that require high power, such as electric vehicles, are composed of a plurality of secondary battery cells capable of charging and discharging in one pack, and the plurality of packs are combined into one pack. It may consist of a large capacity battery.

In such batteries, especially when multiple secondary batteries alternately charge and discharge, there is a need to efficiently control their charging and discharging to maintain the battery in an appropriate operating state and performance.

For this purpose, a battery management system (BMS) is provided that manages the status and performance of the battery. The BMS measures the battery's current, voltage, and temperature, estimates the battery's remaining capacity (SOC; State of Charge) based on this, and controls the SOC to maximize the vehicle's fuel consumption efficiency. In order to accurately control SOC, it is necessary to accurately measure the SOC of the battery being charged and discharged.

Lithium iron phosphate (LiFePO4) batteries are rechargeable batteries with a long lifespan and high safety. In addition, lithium iron phosphate (LiFePO4) batteries are small and light, and have the advantage of not burning or exploding even if the inside or outside of the battery is damaged.

In addition, it has excellent heat resistance, allows rapid charging, and does not use rare metals, which can significantly reduce costs and eliminate concerns about environmental pollution. Lithium iron phosphate (LiFePO4) batteries can be recharged more than 1,000 times even after discharging to 90% of their total capacity, and their lifespan is more than three times longer than existing lead-acid batteries.

Meanwhile, in such batteries, lithium ions inside the battery generally decrease due to SEI (Solid Electrolyte Interphase) as charging or discharging operations are repeated. Accordingly, the charging capacity of the battery gradually decreases.

Generally, RPT (Reference Performance Test) is used to measure battery capacity. RPT uses full charge and full discharge, so it is difficult to achieve this environment in actual use. Therefore, there is a need for a battery capacity estimation method using indirect factors.

KR 10-2013-0083220 A KR 10-2016-0103332 A KR 10-1429292 B1

Accordingly, the technical problem of the present invention was conceived in this regard, and the purpose of the present invention is to provide a method for estimating capacity based on the full charge voltage section of an iron phosphate battery.

Another object of the present invention is to provide a recording medium on which a computer program for performing a method of estimating capacity based on the full charge voltage section of the iron phosphate battery is recorded.

Another object of the present invention is to provide an apparatus for performing a capacity estimation method based on the full charge voltage section of the iron phosphate battery.

The capacity estimation method based on the full charge voltage section of an iron phosphate battery according to an embodiment for realizing the object of the present invention described above is a method in which the voltage after discharge changes by more than a predetermined range from the point where discharge begins after full charge of the iron phosphate battery. A step of specifying a full charge voltage (HV; High Voltage) section, which is a voltage section up to a point; Measuring the length of high voltage period (LHP) of the iron phosphate battery in the full charge voltage section; Generating a capacity estimation model using characteristic values according to each capacity of the iron phosphate battery as input; And using the generated capacity estimation model, estimating the capacity of the iron phosphate battery based on the characteristic values measured in the full charge voltage section of the iron phosphate battery.

In an embodiment of the present invention, the characteristic value may include the usage length of the full charge voltage section, charge/discharge rate (C-rate), and temperature.

In an embodiment of the present invention, the method for estimating capacity based on the full charge voltage section of the iron phosphate battery may further include measuring the usage length, current, and voltage of the iron phosphate battery in the full charge voltage section.

In an embodiment of the present invention, the step of generating a capacity estimation model includes directly measuring the capacity of the iron phosphate battery through RPT (Reference Performance Test) at each charge/discharge rate (C-rate) and temperature. can do.

In a computer-readable storage medium according to an embodiment for realizing another object of the present invention described above, a computer program for performing a method of estimating capacity based on the full charge voltage section of the iron phosphate battery is recorded.

In order to realize another object of the present invention described above, a capacity estimation device based on the full charge voltage section of an iron phosphate battery according to an embodiment is provided, wherein the voltage after discharge is greater than or equal to a predetermined range from the point where discharge begins after full charge of the iron phosphate battery. A full-charge voltage section designator that specifies a full-charge voltage (HV; High Voltage) section, which is the voltage section up to the point of change; A usage length measurement unit that measures the usage length (LHP; Length of High voltage Period) of the iron phosphate battery in the full-charge voltage section; A capacity learning unit that generates a capacity estimation model using characteristic values according to each capacity of the iron phosphate battery as input; and a capacity estimator that estimates the capacity of the iron phosphate battery based on characteristic values measured in the full charge voltage section of the iron phosphate battery using the generated capacity estimation model.

In an embodiment of the present invention, the characteristic value may include the usage length of the full charge voltage section, charge/discharge rate (C-rate), and temperature.

In an embodiment of the present invention, the capacity learning unit may measure the usage length, current, and voltage of the iron phosphate battery in the full charge voltage section.

In an embodiment of the present invention, the capacity learning unit can directly measure the capacity of the iron phosphate battery through RPT (Reference Performance Test) at each charge/discharge rate (C-rate) and temperature.

According to this method of estimating capacity based on the full charge voltage section of an iron phosphate battery, a voltage section to estimate capacity is specified based on the point where discharge begins after full charge, and the usage length (high voltage) continues in this section ( The capacity of an iron phosphate battery can be indirectly estimated using LHP (Length of High voltage Period).

In addition, since the present invention measures LHP only in the high voltage (HV) section, it is not significantly affected by the user's usage pattern and can increase the reliability of battery capacity estimation.

Figure 1 is a block diagram of a capacity estimation device based on the full charge voltage section of an iron phosphate battery according to an embodiment of the present invention.
Figure 2 is a graph showing the HV section and LHP of a new battery (Fresh Cell).
Figure 3 is a graph showing the HV section and LHP of an old battery (aging cell) for comparison with Figure 2.
Figure 4 is a graph showing the change in LHP according to temperature in an iron phosphate battery.
Figure 5 is a graph showing the change in LHP according to C-rate in an iron phosphate battery.
Figure 6 is a graph showing a virtual graph of learning data according to the present invention.
Figure 7 is a graph showing a virtual graph of user data according to the present invention.
Figure 8 is a flowchart of a method for estimating capacity based on the full charge voltage section of an iron phosphate battery according to an embodiment of the present invention.

The detailed description of the present invention described below refers to the accompanying drawings, which show by way of example specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the invention are different from one another but are not necessarily mutually exclusive. For example, specific shapes, structures and characteristics described herein with respect to one embodiment may be implemented in other embodiments without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. Accordingly, the detailed description that follows is not intended to be taken in a limiting sense, and the scope of the invention is limited only by the appended claims, together with all equivalents to what those claims assert, if properly described. Similar reference numbers in the drawings refer to identical or similar functions across various aspects.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

Figure 1 is a block diagram of a capacity estimation device based on the full charge voltage section of an iron phosphate battery according to an embodiment of the present invention.

The capacity estimation device 10 (hereinafter referred to as the device) based on the full charge voltage section of an iron phosphate battery according to the present invention specifies a voltage section to estimate capacity based on the point at which discharge begins after full charge, and determines a specific voltage (High Voltage) in this section. ) indirectly estimates the capacity of the iron phosphate battery using the Length of High voltage Period.

Referring to FIG. 1, the device 10 according to the present invention includes a full charge voltage section designator 110, a usage length measurement unit 130, a capacity learning unit 150, and a capacity estimator 170. The device 10 may be some module of an electric vehicle.

The device 10 of the present invention can be installed and executed with software (application) for performing capacity estimation based on the full charge voltage section of an iron phosphate battery, and includes the full charge voltage section designator 110 and the usage length measurement unit ( 130), the configuration of the capacity learning unit 150 and the capacity estimating unit 170 can be controlled by software for performing capacity estimation based on the full charge voltage section of the iron phosphate battery executed in the device 10. there is.

The device 10 may be a separate terminal or a partial module of the terminal. In addition, the full charge voltage section designator 110, the usage length measurement unit 130, the capacity learning unit 150, and the capacity estimation unit 170 are formed as an integrated module or are composed of one or more modules. You can lose. However, on the contrary, each component may be comprised of a separate module.

The device 10 may be mobile or fixed. The device 10 may be referred to by other terms such as device, apparatus, terminal, user equipment (UE), mobile station (MS), wireless device, handheld device, etc. It can be called .

The device 10 can execute or produce various software based on an operating system (OS), that is, a system. The operating system is a system program that allows software to use the hardware of the device, and includes mobile computer operating systems such as Android OS, iOS, Windows Mobile OS, Bada OS, Symbian OS, Blackberry OS, Windows series, Linux series, Unix series, etc. It can include all computer operating systems such as MAC, AIX, and HP-UX.

The full-charge voltage section designator 110 specifies a full-charge voltage (HV; High Voltage) section, which is a voltage section from the point where discharging begins after the iron phosphate battery is fully charged to the point where the voltage after discharge changes beyond a pre-designated range. . The usage length measuring unit 130 measures the usage length (LHP; Length of High voltage Period) of the iron phosphate battery in the full charge voltage section.

In other words, set the reference point for the full charge voltage (HV; High Voltage) section of the iron phosphate battery, and set the C-rate and temperature to test the LHP. Afterwards, it is possible to measure how much time has changed during the voltage change section.

Figures 2 and 3 show the HV section and LHP of a new battery (Fresh Cell) and an old battery (Aging Cell).

Here, the HV section is the voltage section from the point at which discharge begins after full charge to the point where it changes rapidly after discharge, and DFC (Distance Full Charge) is the capacity discharged in a fully charged state. LHP (Length of High voltage Period) refers to the length of usage during the HV section. LHP can only be measured in situations where temperature and C-rate are constant.

Referring to Figures 2 and 3, it can be seen that the LHP appears longer in the same HV section in a new battery (Fresh Cell) compared to an old battery (Aging Cell).

The capacity learning unit 150 generates a capacity estimation model that inputs characteristic values according to each capacity of the iron phosphate battery. Here, the characteristic values include the usage length of the full charge voltage section, charge/discharge rate (C-rate), and temperature.

Specifically, capacity is measured directly at various C-rates and temperatures to create a capacity estimation model. For example, the capacity of an iron phosphate battery can be measured through RPT (Reference Performance Test).

Through this, a battery actual capacity data set is created, and the HV section is defined as the point from the start of discharging after full charge to the point where it changes rapidly after discharging. In addition, LHP is measured in the HV section, and a table of LHP, C-rate, and temperature for each capacity, which are characteristic values, is created.

A table containing feature values for each capacity is used as input, and capacity is trained as a target to create a capacity estimation model.

Figure 4 shows the LHP (left) by temperature by specifying the point from the start of discharge after full charge to the point where it changes rapidly after discharge in the discharge graph by temperature (right).

Referring to FIG. 4, it can be seen that the temperature affects the length of the LHP, as the higher the temperature, the longer the LHP. Therefore, in the present invention, the temperature of the battery is defined as a factor affecting LHP and used as a characteristic value.

Figure 5 shows the LHP (left) by temperature by specifying the point from the start of discharge after full charge to the point where it changes rapidly after discharge in the discharge graph by C-rate (right).

C-rate (Current rate) refers to the ratio of charging and discharging current to the battery capacity. In other words, it is a unit for setting the current value and predicting or indicating the usable time of the battery under various usage conditions when charging and discharging the battery. . The unit of C-rate is C.

To calculate the current value according to the charge/discharge rate, the charge/discharge current is divided by the value minus the unit of battery rated capacity to calculate the charge/discharge current value as shown in Equation 1 below.

[Equation 1]

C-rate (A) = charge/discharge current (A) / rated capacity of battery

Here, 1C means charging at 1A based on a 1Ah battery. At 2C, it charges and discharges at 2A, so a 1Ah battery can be charged and discharged for 30 minutes in a fully charged state. As the C-rate increases, a battery of the same capacity is charged and discharged at a higher current, so the internal resistance of the battery can be designed to decrease to improve output characteristics.

Referring to FIG. 5, it can be seen that the lower the C-rate, the longer the LHP, so that the C-rate affects the length of the LHP. Therefore, in the present invention, the temperature of the battery is defined as a factor affecting LHP and used as a characteristic value.

The capacity estimation unit 170 uses the generated capacity estimation model to estimate the capacity of the iron phosphate battery based on characteristic values measured in the full charge voltage section of the iron phosphate battery. The estimated battery capacity can be stored in the database and reflected in later learning data.

LHP is measured during the HV section from the time the state is fully charged and discharged, and the characteristic values for each capacity (LHP, C-rate, temperature) are used to estimate the capacity from the capacity estimation model as shown in Equation 2 below. estimate.

[Equation 2]

Figure 6 is a graph showing a virtual graph of learning data according to the present invention. Figure 7 is a graph showing a virtual graph of user data according to the present invention.

Referring to Figures 6 and 7, in the present invention, a model that can indirectly estimate capacity through characteristic values in the HV section is created using pre-made learning data. Afterwards, when the user uses it in a random pattern and reaches the HV section, characteristic values are extracted, and the extracted value allows indirect capacity estimation using a capacity estimation model created through learning data.

In general, batteries are rarely used with constant current. The current of a car battery also changes depending on when the user accelerates or decelerates or whether there is a slope on the road.

Referring to FIG. 7, in the present invention, LHP is measured only in the high voltage (HV) section, so it is not greatly affected by the user's usage pattern. Additionally, batteries are generally not used immediately after being fully charged, but are used after a long period of time has passed with the charger plugged in. Therefore, because there is sufficient REST, the measured voltage value can be trusted.

Figure 8 is a flowchart of a method for estimating capacity based on the full charge voltage section of an iron phosphate battery according to an embodiment of the present invention.

The method for estimating capacity based on the full charge voltage section of an iron phosphate battery according to this embodiment may be carried out in substantially the same configuration as the device 10 of FIG. 1. Accordingly, the same components as those of the device 10 in FIG. 1 are given the same reference numerals, and repeated descriptions are omitted.

Additionally, the method for estimating capacity based on the full charge voltage section of the iron phosphate battery according to this embodiment can be executed by software (application) for performing capacity estimation based on the full charge voltage section of the iron phosphate battery.

The present invention specifies a voltage section for estimating capacity based on the point at which discharge begins after full charge, and indirectly uses the Length of High Voltage Period, during which a certain voltage (High Voltage) continues in this section. Estimate the capacity of an iron battery.

Referring to FIG. 8, in the capacity estimation method based on the full charge voltage section of the iron phosphate battery according to this embodiment, when discharging starts after full charge of the iron phosphate battery (step S00), the post-discharge voltage from the point where discharge starts is predetermined. Specify the full charge voltage (HV; High Voltage) section, which is the voltage section up to the point where it changes beyond the specified range (step S10).

Measure the length of high voltage period (LHP) of the iron phosphate battery in the full charge voltage section (step S20). In addition, the usage length, current, and voltage of the iron phosphate battery are measured in the full-charge voltage section.

The HV section is the voltage section from the point at which discharge begins after full charge to the point where it changes rapidly after discharge, and DFC (Distance Full Charge) is the capacity discharged in a fully charged state. LHP (Length of High voltage Period) refers to the length of usage during the HV section. LHP can only be measured in situations where temperature and C-rate are constant.

In general, LHP appears longer in the same HV section in a new battery (Fresh Cell) compared to an old battery (Aging Cell).

A capacity estimation model is created using characteristic values according to each capacity of the iron phosphate battery as input (step S30). Here, the characteristic values include the usage length of the full charge voltage section, charge/discharge rate (C-rate), and temperature.

Specifically, capacity is measured directly at various C-rates and temperatures to create a capacity estimation model. For example, the capacity of an iron phosphate battery can be measured through RPT (Reference Performance Test).

Through this, a battery actual capacity data set is created, and the HV section is defined as the point from the start of discharging after full charge to the point where it changes rapidly after discharging. In addition, LHP is measured in the HV section, and a table of LHP, C-rate, and temperature for each capacity, which are characteristic values, is created.

A table containing feature values for each capacity is used as input, and capacity is trained as a target to create a capacity estimation model.

Since the higher the temperature, the longer the LHP, in the present invention, the temperature of the battery is defined as a factor affecting LHP and is used as a characteristic value. Additionally, the lower the C-rate, the longer the LHP, so in the present invention, the temperature of the battery is defined as a factor affecting LHP and used as a characteristic value.

Using the generated capacity estimation model, the capacity of the iron phosphate battery is estimated based on the characteristic values measured in the full charge voltage section of the iron phosphate battery (step S40). The estimated battery capacity can be stored in the database and reflected in later learning data.

The present invention specifies a voltage section to estimate capacity based on the point at which discharge begins after full charge, and indirectly uses the Length of High Voltage Period (LHP) at which a specific voltage (High Voltage) continues in this section. The capacity of an iron phosphate battery can be estimated.

In addition, since the present invention measures LHP only in the high voltage (HV) section, it is not significantly affected by the user's usage pattern and can increase the reliability of battery capacity estimation.

This method of estimating capacity based on the full charge voltage section of an iron phosphate battery may be implemented as an application or in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc., singly or in combination.

The program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and usable by those skilled in the computer software field.

Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and perform program instructions, such as ROM, RAM, flash memory, etc.

Examples of program instructions include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform processing according to the invention and vice versa.

Although the above has been described with reference to the embodiments, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand.

The present invention creates a model that can indirectly estimate capacity through feature values in the HV section using previously measured data, and extracts feature values when the user uses a random pattern and reaches the HV section. At this time, indirect capacity estimation is possible using the capacity estimation model generated through the learning data using the extracted value, so it can be usefully applied to electric vehicles using batteries.

10: Capacity estimation device based on the full charge voltage section of iron phosphate battery
110: Full charge voltage section designation unit
130: Usage length measurement unit
150: Capacity learning unit
170: Capacity estimation unit

Claims (9)

Specifying a full charge voltage (HV; High Voltage) section, which is a voltage section from the point where discharge begins after full charge of the iron phosphate battery to the point where the voltage after discharge changes beyond a pre-specified range;
Measuring the usage length (LHP; Length of High voltage Period) of the iron phosphate battery, which refers to the length of the full charge voltage section that measures the amount of use or duration of discharge at a constant rate during the full charge voltage section;
Generating a capacity estimation model using as input a characteristic value including the usage length of the iron phosphate battery according to each capacity in a designated full charge voltage section; and
Using the generated capacity estimation model, estimating the capacity of the iron phosphate battery based on a characteristic value including the usage length of the iron phosphate battery measured in a designated full charge voltage section; including, full charge of the iron phosphate battery. Capacity estimation method based on voltage section.
According to paragraph 1,
A capacity estimation method based on the full charge voltage section of an iron phosphate battery, where the characteristic values include the usage length, charge/discharge rate (C-rate), and temperature of the full charge voltage section.
According to paragraph 1,
A method for estimating capacity based on a full charge voltage section of an iron phosphate battery, further comprising: measuring the usage length, current, and voltage of an iron phosphate battery in a full charge voltage section.
The method of claim 1, wherein the step of generating a capacity estimation model includes:
A capacity estimation method based on the full charge voltage section of an iron phosphate battery, comprising: directly measuring the capacity of the iron phosphate battery through RPT (Reference Performance Test) at each charge/discharge rate (C-rate) and temperature.
A computer-readable storage medium recording a computer program for performing the method for estimating capacity based on the full charge voltage section of the iron phosphate battery according to any one of claims 1 to 4.
A full-charge voltage section designator that specifies a full-charge voltage (HV; High Voltage) section, which is a voltage section from the point where discharge begins after full charge of the iron phosphate battery to the point where the voltage after discharge changes beyond a pre-specified range;
A usage length measuring unit that measures the usage length (LHP; Length of High voltage Period) of the iron phosphate battery, which refers to the length of the full charge voltage section that measures the usage or duration of discharge at a constant rate during the full charge voltage section;
A capacity learning unit that generates a capacity estimation model that inputs characteristic values including the usage length of the iron phosphate battery according to each capacity in a designated full charge voltage section; and
A capacity estimator for estimating the capacity of the iron phosphate battery based on the characteristic value including the usage length of the iron phosphate battery measured in a designated full charge voltage section using the generated capacity estimation model; an iron phosphate battery comprising a. A capacity estimation device based on the full charge voltage section.
According to clause 6,
A capacity estimation device based on the full charge voltage section of an iron phosphate battery, wherein the characteristic values include the full charge voltage section, the usage length of the full charge voltage section, charge/discharge rate (C-rate), and temperature.
The method of claim 6, wherein the capacity learning unit,
A capacity estimation device based on the full charge voltage section of an iron phosphate battery, which measures the usage length, current, and voltage of the iron phosphate battery in the full charge voltage section.
The method of claim 6, wherein the capacity learning unit,
A capacity estimation device based on the full charge voltage section of an iron phosphate battery that directly measures the capacity of the iron phosphate battery through RPT (Reference Performance Test) at each charge/discharge rate (C-rate) and temperature.

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