JP7402205B2 - Deterioration determination method, deterioration determination program, and deterioration determination device for secondary batteries - Google Patents

Description

The present invention relates to, for example, a method for determining deterioration of a secondary battery, a deterioration determination program, and a deterioration determination device.

When the number of times of charging and discharging of a secondary battery increases, performance deterioration occurs such as an increase in internal resistance of the battery and a decrease in battery capacity. If such performance deterioration occurs, sufficient power cannot be supplied to the power supply destination, so deterioration of the secondary battery may be determined and measures such as replacing the battery may be taken. Therefore, techniques related to determining the deterioration of secondary batteries are disclosed in Patent Documents 1 and 2.

The secondary battery management device described in Patent Document 1 is a secondary battery management device that performs input/output control of the secondary battery, and includes a charging state detection section that detects the charging state of the secondary battery, and a secondary battery management device that performs input/output control of the secondary battery. A battery deterioration separation unit that separates the battery deterioration state into capacity deterioration and resistance deterioration; and a battery deterioration separation unit that separates the battery deterioration state into capacity deterioration and resistance deterioration. A usable capacity calculation unit that calculates capacity. In addition, the battery deterioration isolation unit of Patent Document 1 determines the charging current curve during charging for each of a plurality of predetermined temperature deterioration conditions in which the temperature of the secondary battery is changed, and also takes into account the dependent state of capacity deterioration and resistance deterioration. Capacity deterioration and Understand the deterioration state considering the dependence state of resistance deterioration.

The battery deterioration detection device described in Patent Document 2 is a battery deterioration detection device that detects the deterioration state of a battery mounted on a vehicle, and each time the vehicle is started, the battery deterioration detection device detects the voltage of the battery at the time of starting the vehicle. a flag setting unit that sets a flag indicating a sign of deterioration of the battery based on the value; a flag storage unit that stores the flag; a deterioration sign determination unit that determines whether or not there is a deterioration sign determination unit; and when the deterioration sign determination unit determines that the battery has a deterioration sign, the battery is in a deteriorated state based on the voltage value of the battery. and a deterioration determination unit that determines whether or not the deterioration determination unit is provided.

Patent No. 6217916 Patent No. 5821899

However, the management device described in Patent Document 1 judges capacity deterioration and increase in internal resistance based on a map prepared in advance, so there is a problem that it cannot be applied when using reused batteries with large variations in performance. Furthermore, since the battery deterioration detection device described in Patent Document 2 determines signs of deterioration at the time of startup, there is a problem in that it is difficult to apply to a stationary secondary battery that is expected to be used continuously. In other words, the techniques described in Patent Documents 1 and 2 have a problem in that the number of secondary batteries that can be determined to be degraded is limited.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a means for determining deterioration of a secondary battery that can be applied regardless of the start of use of the secondary battery or the manner of use.

One aspect of the method for determining deterioration of a secondary battery according to the present invention is to record fluctuations in battery voltage of the secondary battery in a log on a computer, and analyze the log using the computer. A method for determining deterioration of a secondary battery that determines deterioration, the method includes a reference voltage distribution generation process that creates a reference voltage distribution by acquiring a battery voltage distribution, which is a reference for determining a secondary battery, from the log, and the standard. A determination voltage distribution generation process that creates a determination voltage distribution from the log indicating the distribution of battery voltage of the secondary battery at the time of determination after voltage distribution creation; A deterioration determination process is performed to determine deterioration of the secondary battery based on a first comparison result that compares the appearance frequency of the side voltage value and a second comparison result that compares the appearance frequency of the high voltage side voltage value.

One aspect of the secondary battery deterioration determination program according to the present invention is executed on a computer, records fluctuations in battery voltage of the secondary battery in a log on the computer, and analyzes the log using the computer. This is a secondary battery deterioration determination program that determines the deterioration of the secondary battery by determining the deterioration of the secondary battery, and the reference voltage that creates a reference voltage distribution by acquiring the battery voltage distribution that is the standard for determining the secondary battery from the log. a distribution generation process; a determination voltage distribution generation process for creating a determination voltage distribution from the log indicating the distribution of battery voltage of the secondary battery at a determination time point after the reference voltage distribution is created; Deterioration in which the deterioration of the secondary battery is determined based on a first comparison result that compares the appearance frequency of the low voltage side voltage value with respect to the reference voltage distribution and a second comparison result that compares the appearance frequency of the high voltage side voltage value. A determination process is performed.

One aspect of the secondary battery deterioration determination device according to the present invention includes: a voltage detection unit that detects battery voltage of the secondary battery; a storage unit; and a storage unit that stores the battery voltage as a log in the storage unit, and A reference voltage distribution generation process that creates a reference voltage distribution by acquiring a battery voltage distribution that is a reference for battery determination from the log, and a battery voltage distribution of the secondary battery at the time of determination after creating the reference voltage distribution. a voltage distribution generation unit that performs a determination voltage distribution generation process of creating a determination voltage distribution representing the distribution from the log; and a voltage distribution generation unit that performs a determination voltage distribution generation process that creates a determination voltage distribution representing the distribution from the log, and compares the appearance frequency of low voltage side voltage values with respect to the determination voltage distribution and the reference voltage distribution. and a deterioration determination section that determines deterioration of the secondary battery based on the first comparison result and the second comparison result that compares the appearance frequency of the high voltage side voltage value.

According to the method for determining deterioration of a secondary battery, the program for determining deterioration, and the device for determining deterioration of a secondary battery of the present invention, it is possible to provide a means for determining deterioration of a secondary battery that is applicable regardless of the start time of use or the manner of use of the secondary battery. I can do it.

2 is a voltage change graph illustrating a difference in battery voltage fluctuation due to a decrease in performance of a secondary battery. 2 is a graph illustrating a difference in the frequency of appearance of battery voltage due to a decrease in performance of a secondary battery. 7 is a graph illustrating differences in the frequency of appearance of battery voltage due to differences in performance deterioration factors of secondary batteries. 1 is a block diagram of a secondary battery system according to Embodiment 1. FIG. 3 is a flowchart illustrating the operation of the deterioration determination device according to the first embodiment.

For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, each element described in the drawing as a functional block that performs various processes can be configured with a CPU (Central Processing Unit), memory, and other circuits in terms of hardware, and can be configured with a memory and other circuits in terms of software. This is accomplished by a program loaded into the computer. Therefore, those skilled in the art will understand that these functional blocks can be implemented in various ways using only hardware, only software, or a combination thereof, and are not limited to either. Note that in each drawing, the same elements are designated by the same reference numerals, and redundant explanations will be omitted as necessary.

Further, the above-described program includes a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments when loaded into the computer. The program may be stored on a non-transitory computer readable medium or a tangible storage medium. By way of example and not limitation, computer readable or tangible storage media may include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD -Includes ROM, digital versatile disc (DVD), Blu-ray disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disc storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, transitory computer-readable or communication media includes electrical, optical, acoustic, or other forms of propagating signals.

Embodiment 1
First, the characteristics of the secondary battery that is the subject of deterioration determination will be explained. For secondary batteries, the rate of performance deterioration varies depending on various factors such as the increase in the number of charging and discharging times, the length of the period of use, and the temperature of the environment in which the battery is used. When the performance of the secondary battery deteriorates, the battery capacity decreases, internal resistance increases, and the ability to supply power to the power supply destination decreases. When the performance of such a secondary battery decreases, a change occurs in the output voltage of the secondary battery (hereinafter referred to as battery voltage) when the current flowing through the secondary battery during charging and discharging is set to the same condition.

Therefore, FIG. 1 shows a voltage change graph illustrating the difference in battery voltage fluctuation due to a decrease in the performance of a secondary battery. The graph shown in FIG. 1 shows what difference occurs in the battery voltage when there is and is not a decrease in battery performance when charging and discharging currents of the same current value are applied to the secondary battery. The graph of FIG. 1 shows that charging occurs when the voltage increases, and discharging occurs when the voltage decreases.

As shown in FIG. 1, for a secondary battery whose performance has not deteriorated, the voltage fluctuation range of the voltage change during charging and discharging generally falls within the initial voltage fluctuation range. On the other hand, as the performance of the secondary battery continues to deteriorate, the voltage fluctuation range of the voltage change during charging and discharging increasingly becomes a voltage caution area defined above and below the initial voltage fluctuation range. In the following explanation, the frequency of appearance of this battery voltage will be used as an index for determining deterioration. The voltage used as an index for determining deterioration includes an upper voltage when the battery voltage changes from increasing to decreasing, and a lower voltage when the battery voltage changes from decreasing to increasing.

Here, a description will be given of how the frequency of appearance of a voltage used as an index for determining deterioration varies depending on the progress of performance deterioration of a secondary battery. In the following description, the voltage used as an index for determining deterioration will be referred to as battery voltage. FIG. 2 shows a graph illustrating the difference in frequency of appearance of battery voltage due to deterioration of the secondary battery.

As shown in FIG. 2, the frequency of appearance of the battery voltage obtained at the initial stage of use of the secondary battery generally falls within the initial voltage fluctuation range. On the other hand, as the performance of the secondary battery continues to deteriorate, the frequency of the battery voltage with the highest frequency of occurrence decreases, and the number of battery voltages that appear in the voltage caution range increases. In other words, as the performance of the secondary battery continues to deteriorate, the top of the peak of the battery voltage frequency distribution becomes low and the distribution shape becomes wide.

Conceptually, the difference in the frequency of appearance of battery voltage shown in Figure 2 appears as the performance of the secondary battery deteriorates, but differences in the frequency of appearance of battery voltage also occur depending on the factors that cause the performance of the secondary battery to deteriorate. . Therefore, FIG. 3 shows a graph illustrating the difference in the appearance frequency of battery voltage due to the difference in the performance deterioration factors of the secondary battery.

As shown in Figure 3, the distribution of battery voltage of the initial battery obtained at the beginning of use of the secondary battery has a narrower and higher frequency distribution than that of the secondary battery whose performance has deteriorated. . In the secondary battery system 1 according to the first embodiment, the battery voltage distribution of this initial battery is acquired over a certain period of time from the start of use of the secondary battery to be used. In the secondary battery system 1 according to the first embodiment, the initial battery voltage distribution is used as a reference voltage distribution, and is used as a comparison standard in the process of determining the degree of progress of performance deterioration of the secondary battery.

As shown in FIG. 3, as the performance of the secondary battery continues to deteriorate, the frequency of appearance of battery voltages on the low voltage side and high voltage side increases with respect to the reference voltage distribution. At this time, when the degree to which battery capacity deterioration progresses is high, the frequency of appearance of battery voltage on the low voltage side becomes higher than when the degree to which the increase in internal resistance progresses is low. Furthermore, when the rate at which the battery capacity decreases is high, the frequency of appearance of the battery voltage on the high voltage side becomes higher than when the rate at which the internal resistance increases is low. To put this situation in perspective, if the rate of battery capacity decline is high, the increase in the frequency of appearance of battery voltage on the low voltage side will be large, and the amount of increase in the frequency of appearance of battery voltage on the high voltage side will be small. becomes. Further, when the degree of increase in internal resistance is high, the amount of increase in the frequency of appearance of battery voltage on the low voltage side is medium, and the amount of increase in the frequency of appearance of battery voltage on the high voltage side is medium.

In the secondary battery system 1 according to the first embodiment, it is determined whether the performance decline of the secondary battery exceeds a preset deterioration threshold based on the difference in the appearance frequency of battery voltages explained in FIG. Therefore, the secondary battery system 1 according to the first embodiment will be explained in detail. FIG. 4 shows a block diagram of the secondary battery system 1 according to the first embodiment. As shown in FIG. 4, the secondary battery system 1 according to the first embodiment includes a deterioration determination device 10, a storage battery 20, a power conditioner 30, and a system control unit 40.

In the secondary battery system 1 according to the first embodiment, the system control unit 40 is a host system of the deterioration determination device 10, and the system control unit 40 controls the power conditioner 30 to control charging and discharging of the storage battery 20. . The power conditioner 30 performs, for example, a charging process of charging the storage battery 20 with power supplied from the grid power supply wiring, and a power supply process of supplying the power stored in the storage battery 20 to a power supply destination. Further, the charging power to the storage battery 20 may be provided by a solar panel. The deterioration determination device 10 monitors the battery voltage Vbat, which is the output voltage of the storage battery 20, and determines the degree of deterioration of the storage battery 20.

The deterioration determination device 10 can realize the functions of the processing blocks to be described later, for example, by executing the deterioration determination program in a computer equipped with an arithmetic unit that can execute the program and a memory as a storage unit, and can also realize the functions of the processing blocks. It can also be realized by the hardware that implements it.

The deterioration determination device 10 includes a voltage detection section 11, a voltage distribution generation section 12, a storage section 13, and a deterioration determination section 14. The voltage detection unit 11 detects the battery voltage Vbat of the secondary battery. At this time, the voltage detection section 11 transmits the upper and lower voltages of the battery voltage to the voltage distribution generation section 12 arranged at the subsequent stage.

Every time the voltage distribution generation unit 12 receives the battery voltage Vbat, the voltage distribution generation unit 12 accumulates the received battery voltage in the voltage data storage area of the storage unit 13 as a log. Further, the voltage distribution generation unit 12 acquires the battery voltage distribution, which is a reference for determining the secondary battery, from the log accumulated in the storage unit 13 during a predetermined period immediately after the start of use of the storage battery 20, and generates a reference voltage distribution. Performs the process of generating the reference voltage distribution to be created. The voltage distribution generation unit 12 stores the generated reference voltage distribution in the reference voltage distribution storage area of the storage unit 13. For this reason, it is suitable for the storage unit 13 to use a non-volatile memory whose stored contents do not disappear even when the power is turned off. Further, the voltage distribution generation unit 12 creates multiple patterns of reference voltage distributions for each characteristic of the ambient temperature and usage history of the storage battery 20. Further, the voltage distribution generation unit 12 generates a voltage distribution for determination from the log accumulated in the storage unit 13, which shows the distribution of the battery voltage Vbat of the secondary battery at the time of determination after the creation of the reference voltage distribution. Perform processing.

The deterioration determination unit 14 determines the voltage distribution based on the first comparison result that compares the appearance frequency of the low voltage side voltage value and the second comparison result that compares the appearance frequency of the high voltage side voltage value for the determination voltage distribution and the reference voltage distribution. A deterioration determination process is performed to determine deterioration of the secondary battery. At this time, the deterioration determination unit 14 uses a reference voltage distribution of a temperature corresponding to the environmental temperature at the time when the determination voltage distribution was created as a comparison target for the determination voltage distribution.

More specifically, in the deterioration determination process, the difference between the appearance frequency of the low voltage side voltage value of the determination voltage distribution and the appearance frequency of the low voltage side voltage value of the reference voltage distribution is larger than the appearance frequency threshold, and If the difference between the appearance frequency of the high-voltage side voltage value of the voltage distribution and the appearance frequency of the high-voltage side voltage value of the reference voltage distribution is smaller than the appearance frequency threshold, it is determined that the battery capacity of the secondary battery has decreased. In addition, in the deterioration determination processing, the difference between the appearance frequency of the low-voltage side voltage value of the determination voltage distribution and the appearance frequency of the low-voltage side voltage value of the reference voltage distribution is larger than the appearance frequency threshold, and If the difference between the appearance frequency of the voltage value and the appearance frequency of the high-voltage side voltage value of the reference voltage distribution is larger than the appearance frequency threshold, it is determined that an increase in internal resistance has occurred in the secondary battery. In the deterioration determination process, it is determined that the deterioration of the secondary battery has reached its limit when it is detected that either a decrease in battery capacity or an increase in internal resistance exceeds a preset deterioration threshold. judge.

Here, it is assumed that the appearance frequency threshold is a value that can distinguish between medium and small increases in appearance frequency as explained with reference to FIG.

Further, in the deterioration determination process, the deterioration determination unit 14 does not immediately determine that the deterioration of the secondary battery has reached its limit when it is determined that the battery capacity has decreased or the internal resistance has increased. In response to the first deterioration determination, the system control unit 40 is instructed to perform refresh processing on the secondary battery. Here, the refresh process is a process in which after discharging the secondary battery until the charging rate falls below a certain level, a charge/discharge cycle is performed at least once until the secondary battery is determined to be fully charged. This refresh process can prevent erroneous determination of deterioration due to the memory effect of the secondary battery.

Next, the operation of the deterioration determination device 10 according to the first embodiment will be explained. Therefore, FIG. 5 shows a flowchart illustrating the operation of the deterioration determination device 10 according to the first embodiment. The deterioration determination device 10 starts operating from the time when the operation of the secondary battery system 1 starts.

Then, the deterioration determination device 10 acquires the initial voltage distribution of the secondary battery over a predetermined period from the start of operation, and creates a reference voltage distribution using the voltage distribution generation unit 12 (step S1). Furthermore, the deterioration determination device 10 generates a plurality of patterns of reference voltage distributions in consideration of temperature, season, and the like.

After that, the deterioration determination device 10 creates a determination voltage distribution indicating the current voltage distribution using the voltage distribution generation unit 12 (step S2). Further, the voltage distribution generation unit 12 acquires current temperature information in conjunction with creation of the determination voltage distribution. Thereafter, in the storage unit 13, the deterioration determining unit 14 reads out the reference voltage distribution corresponding to the current temperature via the voltage distribution generating unit 12, and compares it with the determination voltage distribution generated by the voltage distribution generating unit 12.

Then, the deterioration determination unit 14 compares the first comparison result of determining whether the difference between the low voltage appearance frequency of the determination voltage distribution and the low voltage appearance frequency of the reference voltage distribution is larger than the appearance frequency threshold. obtained (step S3). If the first comparison result shows that the difference between the low voltage appearance frequency of the determination voltage distribution and the low voltage appearance frequency of the reference voltage distribution is equal to or less than the appearance frequency threshold, the deterioration determination unit 14 determines that the storage battery 20 It is determined that no unacceptable performance degradation has occurred (step S4). On the other hand, if the first comparison result shows that the difference between the low voltage appearance frequency of the determination voltage distribution and the low voltage appearance frequency of the reference voltage distribution is larger than the appearance frequency threshold, the deterioration determination unit 14 , obtain a second comparison result (step S5).

In step S5, the deterioration determination unit 14 performs a second comparison in which it is determined whether the difference between the high voltage appearance frequency of the determination voltage distribution and the high voltage appearance frequency of the reference voltage distribution is larger than the appearance frequency threshold. Get results. If the second comparison result shows that the difference between the high voltage appearance frequency of the determination voltage distribution and the high voltage appearance frequency of the reference voltage distribution is equal to or less than the appearance frequency threshold, the deterioration determination unit 14 determines that the storage battery 20 It is determined that the battery capacity has decreased (step S7). On the other hand, if the second comparison result shows that the difference between the high voltage appearance frequency of the determination voltage distribution and the high voltage appearance frequency of the reference voltage distribution is larger than the appearance frequency threshold, the deterioration determination unit 14 , it is determined that the internal resistance has increased in the storage battery 20 (step S6).

Then, in steps S6 and S7, the deterioration determination unit 14 instructs the system control unit 40 to refresh the storage battery 20, and the system control unit 40 starts the refresh process for the storage battery 20. Note that the deterioration determination unit 14 issues instructions for the refresh processing in steps S6 and S7 once after a factor such as a decrease in the battery capacity of the secondary battery or an increase in internal resistance is detected, and then again When the degraded performance of the next battery is recovered, the number of times refreshing is performed is reset.

Thereafter, the deterioration determination unit 14 determines that the refresh process has been executed in steps S6 and S7, and that either the internal resistance or the battery capacity has exceeded the deterioration threshold (for example, in step S3 and step S5). If the condition is determined to be YES (deterioration of the branch), it is assumed that the deterioration of the storage battery 20 has reached its limit and the operation is terminated (step S8). Further, if it is determined in step S8 that the deterioration of the storage battery 20 has not reached the limit (NO branch of step S8), the deterioration determination unit 14 obtains the next first comparison result and second comparison result. A reference voltage distribution for the determination is prepared (step S9), and the voltage distribution for determination in step S2 is created again.

As described above, in the deterioration determination device 10 according to the first embodiment, the reference voltage distribution is acquired from the secondary battery that is the target of deterioration determination when the use of the secondary battery that is the target of deterioration determination is started. Therefore, in the deterioration determination device 10 according to the first embodiment, even if the secondary battery to be subjected to deterioration determination is a reused battery with variations in characteristics, even if it is an unused secondary battery with small variations in characteristics, the high Deterioration can be determined with accuracy.

Further, in the deterioration determination device 10 according to the first embodiment, since the reference voltage distribution and the determination voltage distribution are only obtained from the storage battery 20 in operation, the operation of the storage battery 20 is stopped in order to determine the deterioration of the secondary battery. There's no need. Thereby, the secondary battery system 1 using the deterioration determination device 10 can achieve high operational continuity.

In addition, in the deterioration determination device 10 according to the first embodiment, by performing a refresh process on the secondary battery after the deterioration is determined, it is possible to detect deterioration due to the performance deterioration due to the memory effect of the secondary battery. Misjudgment can be prevented.

Furthermore, in the deterioration determination device 10 according to the first embodiment, it is possible to isolate the cause of performance deterioration of the secondary battery from the difference in the change in voltage distribution based on the performance deterioration factor. In this way, if you can isolate the cause of performance deterioration, you can see a tendency for performance deterioration before it reaches a state of deterioration that makes it unusable, so you can, for example, show users how to use a secondary battery that will prevent performance deterioration. It becomes possible to take measures such as changing the central range of the charging rate.

Note that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit.

1 Secondary battery system 10 Deterioration determination device 11 Voltage detection unit 12 Voltage distribution generation unit 13 Storage unit 14 Deterioration determination unit 20 Storage battery 30 Power conditioner 40 System control unit

Claims (7)

A method for determining deterioration of a secondary battery, which records fluctuations in battery voltage of a secondary battery in a log on a computer, and determines deterioration of the secondary battery by analyzing the log using the computer, the method comprising:
A reference voltage distribution generation process that creates a reference voltage distribution by acquiring a battery voltage distribution that is a reference for determining a secondary battery from the log;
a determination voltage distribution generation process that creates a determination voltage distribution from the log indicating a battery voltage distribution of the secondary battery at a determination time point after the reference voltage distribution is created;
a first comparison result in which the determination voltage distribution and the reference voltage distribution are compared to compare the frequency of appearance of the battery voltage on the low voltage side in a lower voltage range of the battery voltage range where the frequency of appearance has increased; , a deterioration determination process of determining deterioration of the secondary battery based on a second comparison result of comparing the frequency of occurrence of the battery voltage on the high voltage side in a higher voltage range of the battery voltage range in which the frequency of occurrence has increased; A method for determining deterioration of a secondary battery. In the deterioration determination process,
The difference between the appearance frequency of the battery voltage on the low voltage side of the determination voltage distribution and the appearance frequency of the battery voltage on the low voltage side of the reference voltage distribution is greater than an appearance frequency threshold, and the determination If the difference between the appearance frequency of the battery voltage on the high voltage side of the voltage distribution and the appearance frequency of the battery voltage on the high voltage side of the reference voltage distribution is smaller than the appearance frequency threshold, It is determined that the battery capacity has decreased,
The difference between the appearance frequency of the battery voltage on the low voltage side of the determination voltage distribution and the appearance frequency of the battery voltage on the low voltage side of the reference voltage distribution is greater than the appearance frequency threshold, and the determination If the difference between the appearance frequency of the battery voltage on the high voltage side of the secondary voltage distribution and the appearance frequency of the battery voltage on the high voltage side of the reference voltage distribution is greater than the appearance frequency threshold, the secondary battery It is determined that an increase in internal resistance has occurred,
The appearance frequency of the battery voltage on the high voltage side and the low voltage side when it is determined that there is a decrease in the battery capacity, and the frequency of appearance of the battery voltage on the high voltage side and the low voltage side when it is determined that there is an increase in the internal resistance. According to claim 1, it is determined that the deterioration of the secondary battery has reached a limit in response to detecting that either one of the appearance frequency of the battery voltage on the voltage side exceeds a preset deterioration threshold. The described method for determining deterioration of a secondary battery. Refresh processing that performs refresh processing on the secondary battery when it is determined that either one of a decrease in the battery capacity of the secondary battery and an increase in the internal resistance of the secondary battery has occurred. conduct,
The method for determining deterioration of a secondary battery according to claim 2, wherein the deterioration determination process is performed after the refresh process . In the reference voltage distribution generation process, the reference voltage distribution is created for each environmental temperature at which the secondary battery is used;
4. In the deterioration determination process, the reference voltage distribution at a temperature corresponding to the environmental temperature at the time when the determination voltage distribution was created is used as a comparison target for the determination voltage distribution. A method for determining deterioration of a secondary battery described in . The voltages recorded in the reference voltage distribution and the determination voltage distribution are an upper voltage when the battery voltage changes from increasing to decreasing, and a lower voltage when the battery voltage changes from decreasing to increasing. 5. The method for determining deterioration of a secondary battery according to any one of 1 to 4. Deterioration of a secondary battery, which is executed on a computer, records fluctuations in battery voltage of the secondary battery in a log on the computer, and determines deterioration of the secondary battery by analyzing the log using the computer. A determination program,
A reference voltage distribution generation process that creates a reference voltage distribution by acquiring a battery voltage distribution that is a reference for determining a secondary battery from the log;
a determination voltage distribution generation process that creates a determination voltage distribution from the log indicating a battery voltage distribution of the secondary battery at a determination time point after the reference voltage distribution is created;
a first comparison result in which the determination voltage distribution and the reference voltage distribution are compared to compare the frequency of appearance of the battery voltage on the low voltage side in a lower voltage range of the battery voltage range where the frequency of appearance has increased; , a deterioration determination process of determining deterioration of the secondary battery based on a second comparison result of comparing the frequency of occurrence of the battery voltage on the high voltage side in a higher voltage range of the battery voltage range in which the frequency of occurrence has increased; A secondary battery deterioration determination program that performs the following. a voltage detection unit that detects the battery voltage of the secondary battery;
storage section,
a reference voltage distribution generation process of accumulating the battery voltage as a log in the storage unit, obtaining from the log a battery voltage distribution that is a reference for determining the secondary battery to create a reference voltage distribution; and the reference voltage a voltage distribution generation unit that performs a determination voltage distribution generation process of creating a determination voltage distribution from the log indicating a distribution of battery voltage of the secondary battery at a determination time point after distribution creation;
a first comparison result in which the determination voltage distribution and the reference voltage distribution are compared to compare the frequency of appearance of the battery voltage on the low voltage side in a lower voltage range of the battery voltage range where the frequency of appearance has increased; , a deterioration determination unit that determines deterioration of the secondary battery based on a second comparison result that compares the frequency of occurrence of the battery voltage on the high voltage side in a higher voltage range of the battery voltage range in which the frequency of occurrence has increased; A deterioration determination device comprising:

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