JP2022101196A - Deterioration estimation device, deterioration estimation method, and computer program - Google Patents

Abstract

To provide a deterioration estimation device, a deterioration estimation method, and a computer program, capable of estimating the deterioration of a power storage device at the time of shutdown.SOLUTION: A deterioration estimation unit 4 includes a first deriving unit 41 for deriving a first SOC of a power storage device 3 at the time of suspension of the use of the device 3, an acquiring unit 41 for acquiring temperature information during the period of suspension, a second deriving unit 41 for deriving a second SOC before resuming use of the power storage device 3, a third deriving unit 41 for deriving a self-discharge rate on the basis of the first SOC, the second SOC, the temperature information, and the period of suspension, and an estimation unit 41 for estimating the degree of deterioration of the power storage device 3 on the basis of the derived self-discharge rate.SELECTED DRAWING: Figure 2

Description

The present invention relates to a deterioration estimation device for estimating deterioration when a power storage element is stopped, a deterioration estimation method, and a computer program.

A power storage element that can store electrical energy and supply energy as a power source when needed is used. The power storage element is applied to portable equipment, power supply equipment, transportation equipment including automobiles and railways, industrial equipment including aerospace and construction equipment, and the like.

A power storage element (hereinafter referred to as a battery) such as a lithium ion secondary battery gradually deteriorates due to repeated charging and discharging.
It is an important issue to easily and accurately estimate the SOH (State of Health: capacity retention rate, etc.) of a battery in determining whether or not the battery can be used and how to use the battery.

As an example, the relationship between the increase in resistance and the degree of deterioration is obtained, and SOH is estimated based on the relationship. Patent Document 1 discloses an invention of a secondary battery system that calculates a battery charge state based on a battery temperature and an internal resistance calculated from current and voltage.

JP-A-2019-124612

When a battery is installed in an automobile, the above-mentioned technique statistically processes information while driving (when the battery is in use) to detect deterioration, and thus detects deterioration when the vehicle is stopped (when the battery is not in use). I can't. Similarly, in applications other than automobiles, deterioration cannot be detected while the battery is stopped.

An object of the present invention is to provide a deterioration estimation device, a deterioration estimation method, and a computer program capable of estimating deterioration of a power storage element when stopped.

The deterioration estimation device according to one aspect of the present invention includes a first derivation unit for deriving the first SOC when the power storage element is stopped, an acquisition unit for acquiring temperature information during the stop period, and before resuming the use of the power storage element. A second derivation unit for deriving the second SOC, a third derivation unit for deriving the self-discharge rate based on the first SOC, the second SOC, the temperature information, and the stop period, and the derived self-discharge rate. It is provided with an estimation unit for estimating the degree of deterioration of the power storage element based on the above.

In the deterioration estimation method according to one aspect of the present invention, the first SOC when the power storage element is stopped is derived, the temperature information during the stop period is acquired, and the second SOC before the restart of use of the power storage element is derived. The self-discharge rate is derived based on the first SOC, the second SOC, the temperature information, and the stop period, and the degree of deterioration of the power storage element is estimated based on the derived self-discharge rate.

The computer program according to one aspect of the present invention derives the first SOC when the power storage element is stopped, acquires the temperature information during the stop period, derives the second SOC before resuming the use of the power storage element, and obtains the first SOC. The self-discharge rate is derived based on the 1 SOC, the second SOC, the temperature information, and the previous stop period, and the computer is made to execute a process of estimating the degree of deterioration of the power storage element based on the derived self-discharge rate.

In the present invention, the degree of deterioration of the power storage element during the stop period can be estimated with high accuracy.

It is a graph which shows the relationship between the stop period of a power storage element, and the self-discharge rate. It is a block diagram which shows the structure of the charge / discharge system and the server which concerns on Embodiment 1. FIG. It is a graph which shows the relationship between SOC and a coefficient k. It is a graph which shows the relationship between ³ √t and ΔV at a temperature of 25 degreeC. It is a graph which shows the relationship between 1000 / T and lnk. It is a graph which shows the relationship between ³ √t and ΔV in SOC 65%. It is a perspective view of a battery module. It is a flowchart which shows the procedure of the derivation process of the capacity maintenance rate by a control unit. This is an example of a graph showing the fifth relationship between the self-discharge rate and the capacity retention rate. It is a flowchart which shows the procedure of the derivation process of the capacity maintenance rate of the control part which concerns on Embodiment 2.

(Outline of Embodiment)
In the present inventors, the ΔSOC (self-discharge rate) per unit period during the shutdown period of the power storage element decreases as the elapsed time increases, that is, as the deterioration progresses, and the amount of decrease in ΔSOC decreases. I found that it gradually decreased.
FIG. 1 is a graph showing the relationship between the stop period of the power storage element and the self-discharge rate. The horizontal axis of FIG. 1 is the stop period (day), and the vertical axis is the self-discharge rate (%). In FIG. 1, the self-discharge rate (ΔSOC per 30 days) when the temperature of the power storage element is 45 ° C., the SOC1 (first SOC) at the time of stoppage is 85%, and the stoppage period is 30 days is plotted. ing. As shown in FIG. 1, it can be seen that as the elapsed time increases, the self-discharge rate decreases and the amount of decrease in the self-discharge rate also decreases. It is presumed that this is because the amount of side reactions in the power storage element decreases as the deterioration of the power storage element progresses.

The self-discharge rate differs depending on the temperature history even if the first SOC and the stop period are the same. When the temperature is high, the self-discharge rate becomes large. Further, the self-discharge rate differs depending on the first SOC even if the stop period and the temperature are the same. When the self-discharge rate is obtained based on the difference between the first SOC and the second SOC obtained by OCV or the like before resuming the use of the power storage element, and the degree of deterioration is estimated based on the relationship between the self-discharge rate and the degree of deterioration. , The influence of the first SOC and the temperature history is not taken into consideration. The present inventors have found that the self-discharge rate can be derived based on the first SOC, the second SOC, the temperature history, and the stop period, and the degree of deterioration can be satisfactorily estimated based on the derived self-discharge rate and the above relationship. , The present invention has been completed.

That is, the deterioration estimation device according to the embodiment has a first derivation unit that derives the first SOC when the power storage element is stopped, an acquisition unit that acquires temperature information during the stop period, and a first unit before resuming the use of the power storage element. Based on the second out-licensing unit that derives the 2SOC, the third out-licensing unit that derives the self-discharge rate based on the first SOC, the second SOC, the temperature information, and the outage period, and the derived self-discharge rate. It also includes an estimation unit that estimates the degree of deterioration of the power storage element.

Here, the time when the use of the power storage element is stopped is not limited to the timing exactly the same as the timing when the use of the power storage element is stopped, and may include the timing immediately before or immediately after the stop. For example, the first SOC derived by the first derivation unit may be the SOC obtained at the last acquisition timing before the stop. Alternatively, it may be an SOC obtained immediately after entering the suspension period. In this case, after entering the stop period of the power storage element, the SOC may be acquired and then the system may be completely stopped. Before resuming the use of the power storage element, the SOC may be acquired by the SOC-OCV curve or the like when the use of the power storage element is resumed. Alternatively, an SOC obtained by a current integration method or the like at the first SOC acquisition timing after resumption of use may be used. In this case, after reaching the timing of resuming the use of the power storage element, the SOC may be acquired by the SOC-OCV curve or the like, and then the system may be completely restarted.
According to the above configuration, by incorporating it into an existing system such as an electric vehicle, the self-discharge rate can be accurately obtained in consideration of the first SOC, the temperature information, and the stop period, and the self-discharge rate can be satisfactorily obtained when the power storage element is stopped. The degree of deterioration can be estimated.

In the deterioration estimation device described above, the temperature information may be a temperature history.

According to the above configuration, the degree of deterioration of the power storage element can be estimated more accurately by calculating using a plurality of temperatures.

The deterioration estimation device described above includes the first SOC derived by referring to the relationship between the first SOC, the temperature, and the coefficient, and a specific unit that specifies the coefficient based on the temperature information, and the third derivative unit is specified. The self-discharge rate may be derived based on the above-mentioned coefficient.

The temperature information may be a representative value such as an average value, a mode value, or a median value of the temperature during the outage period. Above all, the average value is preferable.
According to the above configuration, when the temperature of the power storage element is not constant during the stop period, the temperature representative value is specified based on the acquired temperature information.
With reference to the relationship between the first SOC, the temperature, and the coefficient obtained in advance, the coefficient can be specified based on the actually measured first SOC and the temperature information, and the self-discharge rate can be easily and satisfactorily derived based on the specified coefficient.

In the deterioration estimation device described above, the coefficient may be a voltage decrease rate.

As described above, the self-discharge rate decreases as the elapsed time increases. The amount of voltage decrease during the stop period corresponding to the self-discharge rate also decreases as the elapsed time increases, and the amount of decrease in the amount of voltage decrease also decreases. The slope of the relationship between the amount of voltage drop and the stop period, that is, the voltage drop rate is used as a coefficient to obtain the voltage drop rate for each first SOC and temperature, and the voltage drop rate is specified based on the measured first SOC and temperature, and the specified voltage drop is specified. By using the speed, the self-discharge rate can be easily and satisfactorily derived.

The deterioration estimation device described above may include an output unit that outputs the estimated degree of deterioration.

According to the above configuration, for example, when the power storage element is provided in, for example, an HEV (hybrid electric vehicle), it is possible to notify the user of the deterioration of the power storage element before starting the engine. With other power storage elements, the degree of deterioration can be obtained before resuming use.

In the deterioration estimation device described above, the third derivation unit may derive the self-discharge rate at a plurality of time points during the stop period, and may integrate the self-discharge rate derived at each time point.

According to the above configuration, by integrating a plurality of self-discharge rates derived according to the change in temperature during the stop period, the self-discharge rate for the entire stop period can be derived with high accuracy.

In the deterioration estimation method according to the embodiment, the first SOC when the power storage element is stopped is derived, the temperature information during the stop period is acquired, the second SOC before the restart of use of the power storage element is derived, and the first SOC, The self-discharge rate is derived based on the second SOC, the temperature information, and the stop period, and the degree of deterioration of the power storage element is estimated based on the derived self-discharge rate.

According to the above configuration, the self-discharge rate can be accurately obtained in consideration of the first SOC, the temperature information, and the stop period, and the degree of deterioration of the power storage element at the time of stop can be estimated satisfactorily.

The computer program according to the embodiment derives the first SOC when the power storage element is stopped, acquires the temperature information during the stop period, derives the second SOC before resuming the use of the power storage element, and describes the first SOC and the above. The self-discharge rate is derived based on the second SOC, the temperature information, and the stop period, and the computer is made to execute a process of estimating the degree of deterioration of the power storage element based on the derived self-discharge rate.

According to the above configuration, the self-discharge rate can be accurately obtained in consideration of the first SOC, the temperature information, and the stop period, and the degree of deterioration of the power storage element at the time of stop can be estimated satisfactorily.
In summary, the degree of deterioration can be estimated accurately by combining the present invention or the present invention in addition to the prior art.

Hereinafter, a method for estimating deterioration of the power storage element will be specifically described.
(Embodiment 1)
FIG. 2 is a block diagram showing the configurations of the charge / discharge system 1 and the server 8 according to the first embodiment. The charge / discharge system 1 is provided in, for example, EV (electric vehicle), HEV, PHEV (plug-in hybrid electric vehicle) and other transportation equipment including automobiles and railways, industrial equipment including aerospace, space and construction. Hereinafter, a case where the charge / discharge system 1 is provided in the HEV supported by the motor at the time of starting and accelerating when the engine uses a large amount of fuel will be described.
The charge / discharge system 1 includes a battery module 3, a control device 4, a voltage sensor 5, a current sensor 6, and a temperature sensor 7.

In the battery module 3, lithium ion secondary batteries (hereinafter referred to as battery cells) 2 as a plurality of power storage elements are connected in series.
The control device 4 controls the entire charge / discharge system 1.
The server 8 includes a control unit 81 and a communication unit 82.
The control device 4 includes a control unit 41, a storage unit 42, a timekeeping unit 43, an input unit 44, and a communication unit 45.
The control unit 41 of the control device 4 is connected to the control unit 81 via the communication unit 45, the network NW, and the communication unit 82.
The load 53 is connected to the battery module 3 via the terminals 51 and 52. When charging, a charger is connected to the battery module 3.

The control units 41 and 81 are composed of, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and control the operations of the control device 4 and the server 8, respectively.

The storage unit 42 stores various programs and data. The SOH estimation program (hereinafter referred to as a program) 421 is stored in the storage unit 42. The program 421 is provided in a state of being stored in a computer-readable recording medium 40 such as a CD-ROM, a DVD-ROM, or a USB memory, and is stored in the storage unit 42 by being installed in the control device 4. Further, the program 421 may be acquired from an external computer (not shown) connected to the communication network and stored in the storage unit 42.

The storage unit 42 also stores the charge / discharge history DB 422, the temperature DB 423, the coefficient DB 424, and the related DB 425. The charge / discharge history is an operation history of the battery module 3, information indicating a period (use period) in which the battery module 3 is charged or discharged, information on charge or discharge performed by the battery module 3 during the use period, and the like. Information including. The information indicating the usage period of the battery module 3 is information including information indicating the start and end points of charging or discharging, the cumulative usage period in which the battery module 3 has been used, and the like. The information regarding charging or discharging performed by the battery module 3 is information indicating the voltage, rate, etc. at the time of charging or discharging performed by the battery module 3.
The temperature DB 423 stores the temperature history of the stop period of the battery module 3.

FIG. 3 is a graph showing the relationship between the SOC (SOC1) at the time of stop and the coefficient k (voltage decrease rate) stored in the coefficient DB 424. The horizontal axis of FIG. 3 is the SOC (%) at the time of stop, and the vertical axis is the coefficient k. k is, for example, the slope of the first relationship between ³ √t and ΔV. Here, t is the number of days. In advance, the first relationship between ³ √t and ΔV is experimentally obtained for each SOC for each average temperature of the battery module 3. For example, as shown in FIG. 4, when the average temperature is 25 ° C., the SOC is changed to, for example, 25%, 45%, and 65%, the first relationship is obtained, and the slope k is obtained, respectively. As shown in FIG. 3, when the average temperature is 25 ° C., k in each SOC is plotted to obtain the second relationship a between SOC and k. The second relations b and c are obtained in the same manner when the average temperature is 45 ° C. and 65 ° C. In the first relationship of FIG. 4, t to the 1 / 3rd power and ΔV have a linear relationship, but the present invention is not limited to this case. It suffices to find n in which t ⁿ and ΔV have a linear relationship, and the voltage decrease rate is the slope of the relationship between t ⁿ and ΔV.
The second relationship can be interpolated. For example, when the average temperature is 35 ° C., the second relationship with the average temperature of 35 ° C. is obtained by interpolation of the second relations a and b, and the coefficient k is read.
Examples of the applicable range of the voltage decrease rate include days: 0 to 150 days, SOC: 25% to 85%, and temperature: −30 ° C. to 65 ° C.

FIG. 5 is a graph showing the relationship between 1000 / T and lnk stored in the coefficient DB424. The horizontal axis of FIG. 5 is 1000 / T (T is absolute temperature), and the vertical axis is lnk (k = ΔV / ³ √t). In advance, the third relationship between ³ √t and ΔV is experimentally obtained for each SOC (SOC1) of the battery module 3 for each average temperature. For example, as shown in FIG. 6, when the SOC is 65%, the average temperature is changed to, for example, 25 ° C., 45 ° C., and 65 ° C. to obtain the third relationship, and the slope k is obtained, respectively. When the SOC is 65%, the logarithm of k in the reciprocal of each average temperature T multiplied by 1000 is plotted to obtain the fourth relation d between 1000 / T and lnk. Similarly, when the SOC is 45% and 25%, the fourth relations e and f are obtained. The fourth relationship is a straight line, and when the average temperature is the same, the average temperature can be used as the representative temperature value even if the difference in temperature during the stoppage period is different. As the representative temperature value, the mode value and the median value of the outage period can be considered, but the average temperature is preferable because the difference in temperature can be offset well.
The coefficient DB424 may store the second relation and the fourth relation as a function (relational expression).

The relationship DB425 stores the fifth relationship between the self-discharge rate SDa and SOH, which is derived as described later. Instead of the fifth relation, the function of SDa may be stored. At least one fifth relationship is stored in the relationship DB425. A plurality of fifth relationships may be stored depending on the range of k and the like.

The timekeeping unit 43 counts the elapsed time.
The input unit 44 receives the input of the detection result from the voltage sensor 5, the current sensor 6, and the temperature sensor 7.
The communication units 45 and 82 have a function of communicating via the network NW, and can transmit and receive required information.

In the present embodiment, either the control device 4 or the server 8 functions as the deterioration estimation device of the present invention. If the server 8 does not function as a deterioration estimation device, the charge / discharge system 1 may not be connected to the server 8.
Although FIG. 2 shows a case where one set of battery modules 3 is provided, a plurality of sets of battery modules 3 may be connected in series.
The control device 4 may be a battery ECU (Electronic Control Unit).

The voltage sensor 5 is connected in parallel to the battery module 3 and outputs a detection result according to the overall voltage of the battery module 3. The voltage sensor 5 is connected to the positive electrode terminal 23 and the negative electrode terminal 26 described later of each battery cell 2, measures the voltage V ₁ between the positive electrode terminal 23 and the negative electrode terminal 26 of each battery cell 2, and each battery cell 2 The voltage V between the negative electrode lead 33 and the positive electrode lead 34, which will be described later, of the battery module 3 which is the total value of V ₁ of the above is detected.
The current sensor 6 is connected in series with the battery module 3 and outputs a detection result according to the current of the battery module 3.
The temperature sensor 7 is provided in the vicinity of the battery module 3 and outputs a detection result according to the temperature of the battery module 3.

FIG. 7 is a perspective view of the battery module 3.
The battery module 3 includes a rectangular parallelepiped case 31 and a plurality of the battery cells 2 housed in the case 31.

The battery cell 2 includes a rectangular parallelepiped case body 21, a lid plate 22, a positive electrode terminal 23, a negative electrode terminal 26 provided on the lid plate 22, a plosive valve 24, and an electrode body 25. The electrode body 25 is formed by laminating a positive electrode plate, a separator, and a negative electrode plate, and is housed in a case body 21.
The electrode body 25 may be obtained by winding a positive electrode plate and a negative electrode plate in a flat shape via a separator.

The positive electrode plate is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of aluminum, an aluminum alloy, or the like, in which an active material layer is formed on a positive electrode base material foil. The negative electrode plate is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of copper, a copper alloy, or the like, in which an active material layer is formed on a negative electrode base material foil. The separator is a microporous sheet made of synthetic resin.

The positive electrode active material used for the active material layer of the positive electrode is, for example, Li _x (Ni _a Mn _b Co _c M _d ) O ₂ (M is a metal element other than Li, Ni, Mn, Co, 0 ≦ a <1, 0). It is a layered oxide represented by ≦ b <1, 0 ≦ c <1, a + b + c + d = 1, 0 <x ≦ 1.1, and a and c are not 0 at the same time). The positive electrode active material has a layered rock salt type crystal structure. The a may satisfy 0.5 ≦ a ≦ 1. In this case, the transition metal site contains a large amount of Ni.
The positive electrode active material is preferably NCM having d = 0 and represented by Li _x (Nia _{Coc Mn b )} O ₂ (a + b + _c = 1). The NCM may be NCM111 (a: b: c = 1: 1: 1), NCM523 (a: b: c = 5: 2: 3) having a high Ni content, or the like.
The positive electrode active material may be NCA in which M is Al and b = 0 and is represented by Li _x (Ni _a Co _c Al _d ) O ₂ (a + c + d = 1).
In NCM or NCA, the metal other than Li and Ni is not limited to two kinds of metals, and may be made of three or more kinds of metals. For example, a small amount of Ti, Nb, B, W, Zr, Ti, Mg and the like may be contained.

Examples of the positive electrode active material include LiMeO ₂ -Li ₂ MnO ₃ solid solution, Li ₂ O-LiMeO ₂ solid solution, Li ₃ NbO ₄ -LiMeO ₂ solid solution, Li ₄ WO ₅ -LiMeO ₂ solid solution, Li ₄ TeO ₅ -LiMeO ₂ solid solution. , Li ₃ SbO ₄ -LiFeO ₂ solid solution, Li ₂ RuO ₃ -LiMeO ₂ solid solution, Li ₂ RuO ₃ -Li ₂ MeO ₃ solid solution and the like.
The positive electrode active material is not limited to the above cases.

The negative electrode active material used for the negative electrode active material layer is a metal or alloy such as graphite, soft carbon, hard carbon, Si, Sn, Cd, Zn, Al, Bi, Pb, Ge, Ag, or a chalcogenide containing these. And so on. An example of a chalcogenide is SiO.

A plurality of battery cells 2 are connected in series by electrically connecting the adjacent positive electrode terminals 23 and the negative electrode terminals 26 of the adjacent battery cells 2 of the battery module 3 by the bus bar 32.
The positive electrode terminal 23 and the negative electrode terminal 26 of the battery cells 2 at both ends of the battery module 3 are provided with a positive electrode lead 34 and a negative electrode lead 33 for extracting electric power.

FIG. 8 is a flowchart showing a procedure for deriving the capacity retention rate as SOH by the control unit 41.
The control unit 41 derives SOC1 when the engine is stopped, that is, when the battery module 3 is stopped (S1). The control unit 41 derives SOC1 by the current integration method.
The control unit 41 reads out the history DB 422 and the temperature DB 423, and acquires the history of the stop period t and the temperature (S2). Here, t is the number of days.

The control unit 41 acquires the OCV immediately before the start of use and derives the SOC2 (S3). The control unit 41 acquires the voltage CCV between terminals and derives the OCV in consideration of the dark current flowing through the control unit 41 and the cell balancer (not shown). Alternatively, the control unit 41 may set the terminal voltage CCV as OCV here.
The control unit 41 reads the SOC corresponding to the derived OCV in the SOC-OCV curve, and sets this as SOC2.

The control unit 41 derives the self-discharge rate SDp by the following equation based on SOC1 and SOC2 (S4).
SDp = (SOC1-SOC2) / t
When CCV is OCV as described above, the decrease in SOC due to dark current is known in advance. Therefore, when SDp is obtained, the decrease in SOC due to dark current is further reduced from SOC1-SOC2.

The control unit 41 specifies the average temperature of the stop period t based on the temperature history (S5).
The control unit 41 reads out the coefficient DB424 and specifies the coefficient k based on the SOC1 and the specified average temperature (S6). The control unit 41 reads, for example, the coefficient k when SOC1 is 45% and the average temperature is 25 ° C., for example, in the graph of the second relationship a in FIG. 3, when SOC1 is 45%. The control unit 41 may read the coefficient k when the average temperature is 25 ° C., that is, 1000/298 in the graph of the fourth relation e in FIG.

The control unit 41 derives ΔV (S7). The control unit 41 calculates ΔV based on the specified k and the stop period t. ΔV is expressed as a function of the stop period t with the coefficient k as a factor. For example, when ³ √t and ΔV have a linear relationship, ΔV is expressed by a function of ³ √t.

The control unit 41 derives SDa based on SDp and ΔV (S8). SDa is represented by the following functions of ΔV and SDp.
SDa = f (ΔV, SDp)
SDa may be represented by a function of k, t, SDp. In this case, it is not necessary to derive ΔV of S7.

The control unit 41 reads out the relation DB425 and derives the capacity retention rate based on the SDa (S9).
The control unit 41 outputs the capacity retention rate to, for example, a car navigation display (S10), and ends the process. The capacity retention rate is displayed as the degree of deterioration on the display, and the user can acquire the degree of deterioration before starting the engine.

FIG. 9 is an example of a graph showing the fifth relationship between SDa and the capacity retention rate as SOH. From FIG. 9, it can be seen that even with the variation of the self-discharge rate of 3σ, the variation of the estimation of the capacity retention rate is within a predetermined range. As described above, the relationship between the self-discharge rate and the degree of deterioration changes depending on the SOC1 and the temperature. It can be seen that k based on SOC1 and temperature can be specified, SDa can be derived based on the specified k, and the capacity retention rate can be satisfactorily derived from SDa based on the fifth relation of the relation DB425.

As described above, according to the present embodiment, the self-discharge rate can be accurately obtained from the SDa in consideration of the SOC1, the temperature history, and the stop period, and the degree of deterioration of the battery module 3 when stopped can be estimated satisfactorily. can. The degree of deterioration of the battery module 3 during use (running) may be derived based on the above-mentioned current integration method or the amount of increase in resistance, and the degree of deterioration during the stop period may be added to obtain the total degree of deterioration. can.

(Embodiment 2)
In the second embodiment, the control unit 41 derives the SDa _i at a predetermined time interval a within the stop period, and derives the capacity retention rate by using the total value of the SDa _i as the SDa of the stop period.
FIG. 10 is a flowchart showing a procedure for deriving the capacity retention rate of the control unit 41 according to the second embodiment.
The control unit 41 derives SOC1 when the engine is stopped, that is, when the battery module 3 is stopped (S11). The control unit 41 derives SOC1 by the current integration method.
The control unit 41 sets the variable i to 1 (S12).

The control unit 41 determines whether or not the time a has elapsed (S13). When the time a has not elapsed (S13: NO), the control unit 41 repeats this determination.
When the time a has elapsed (S13: YES), the control unit 41 reads out the temperature DB 423, acquires the history of the temperature at the time a, and derives the average temperature at the time a (S14).

The control unit 41 derives the OCV from the CCV and derives the SOC2 _i from the OCV (S15).
OCV can be calculated from the following formula, for example.
OCV = CCV + I × R
Here, I: dark current
R: The internal resistance control unit 41 reads the SOC corresponding to the derived OCV in the SOC-OCV curve, and sets this as SOC2 _i .

The control unit 41 derives the self-discharge rate SDp _i by the following equation based on the SOC2 _{i -1} and the SOC2 i (S16).
SDp _i = (SOC2 _i-1 -SOC2 _i ) / t
Here, t: time a (day)
When i = 1, SOC2 _i-1 = SOC1.

The control unit 41 reads out the coefficient DB 424 and specifies the coefficient k based on the SOC2 _i-1 and the specified average temperature (S17). The control unit 41 reads, for example, the coefficient k when SOC2 _i-1 is 45% and the average temperature is 25 ° C., for example, in the graph of the second relation a in FIG. 3, when SOC2 _i-1 is 45%. .. The control unit 41 may read the coefficient k when the average temperature is 25 ° C., that is, 1000/298 in the graph of the fourth relation e in FIG.

The control unit 41 derives ΔV _i (S18). The control unit 41 calculates ΔV _i based on the specified k and the time a. ΔV _i is expressed as a function of time with the coefficient k as a factor. For example, when ³ √t and ΔV have a linear relationship, ΔV is represented by a function of ³ √t, and a is substituted for t.

The control unit 41 derives SDa _i based on SDp _i and ΔV _i (S19). SDa is represented by a function of ΔV _i and SDp _i .
SDa _i = f (ΔV _i , SDp _i )
SDa _i may be represented by a function of k, t, SDp _i . In this case, it is not necessary to derive ΔV _i of S18.

The control unit 41 adds SDa _i to the integrated value of SDa up to the previous time (S20).
The control unit 41 determines whether or not the use of the battery module 3 has been resumed (S21). If the use has not been resumed (S21: NO), the control unit 41 increments i (S22) and returns the process to S13. SDa _i is derived in the same manner as above, and is added in S20.

When the use is resumed (S21: YES), the control unit 41 obtains the SDa _end at the time from the previous derivation of the SDa _i to the resumption in the same manner as described above (S23). If the time when SOC2i is derived is the time of restart, it is not necessary to derive SDa _end .
The control unit 41 adds the SDa _end to the integrated value of SDa up to the previous time (S24).

The control unit 41 reads out the relation DB425 and derives the capacity retention rate based on the total SDa (S25).
The control unit 41 outputs the capacity retention rate to, for example, a car navigation display (S26), and ends the process. The capacity retention rate is displayed as the degree of deterioration on the display, and the user can acquire the degree of deterioration before starting the engine.

According to the present embodiment, since the plurality of self-discharge rates derived according to the change in temperature during the stop period are integrated, the self-discharge rate for the entire stop period can be derived more accurately.

The embodiment is not restrictive. The scope of the invention is intended to include all modifications within the meaning and scope of the claims.
The capacity retention rate is not limited to the case of estimating the capacity retention rate based on the self-discharge rate of the battery module 3, and the capacity retention rate may be estimated based on the self-discharge rate of the battery cell 2.
The SOH is not limited to the case of estimating the capacity retention rate, and the capacity decrease rate, resistance, etc. may be estimated.

The battery module 3 is not limited to the case where it is provided in an automobile. When the battery module 3 is stopped, the degree of deterioration can be estimated by the deterioration estimation method of the present invention when the battery module 3 is provided in another device.
Further, the coefficient k is not limited to the voltage decrease rate.
The power storage element is not limited to the lithium ion secondary battery. The power storage element may be another secondary battery using a non-aqueous electrolyte such as a sodium ion battery.

1 Charge / discharge system 2 Battery cell (storage element)
3 Battery module (power storage element)
4 Control device 41 Control unit (1st out-licensing unit, acquisition unit, 2nd out-licensing unit, 3rd out-licensing unit, estimation unit, specific unit)
42 Storage unit 421 SOH estimation program 422 History DB
423 Temperature DB
424 temperature DB
425 Relational DB
43 Timekeeping unit 44 Input unit 45, 82 Communication unit 5 Voltage sensor 6 Current sensor 7 Temperature sensor 8 Server 81 Control unit

Claims (7)

The first out-licensing unit that derives the first SOC when the power storage element is stopped,
The acquisition unit that acquires temperature information during the stop period,
A second out-licensing unit for deriving the second SOC before resuming the use of the power storage element,
A third derivation unit that derives the self-discharge rate based on the first SOC, the second SOC, the temperature information, and the stop period.
A deterioration estimation device including an estimation unit that estimates the degree of deterioration of the power storage element based on the derived self-discharge rate. The deterioration estimation device according to claim 1, wherein the temperature information is a temperature history. It is provided with the first SOC derived by referring to the relationship between the first SOC, the temperature, and the coefficient, and a specific part for specifying the coefficient based on the temperature information.
The deterioration estimation device according to claim 1, wherein the third derivation unit derives the self-discharge rate based on the specified coefficient. The deterioration estimation device according to claim 3, wherein the coefficient is a voltage reduction rate. The deterioration estimation according to any one of claims 1 to 4, wherein the third derivation unit calculates the self-discharge rate at a plurality of time points and integrates the self-discharge rate calculated at each time point during the stop period. Device. Derived the first SOC when the power storage element is stopped,
Get temperature information during the downtime,
Derived the second SOC before resuming the use of the power storage element,
The self-discharge rate is derived based on the first SOC, the second SOC, the temperature information, and the stop period.
A deterioration estimation method that estimates the degree of deterioration of a power storage element based on the derived self-discharge rate. Derived the first SOC when the power storage element is stopped,
Get temperature information during the downtime,
Derived the second SOC before resuming the use of the power storage element,
The self-discharge rate is derived based on the first SOC, the second SOC, the temperature information, and the stop period.
A computer program that causes a computer to perform a process of estimating the degree of deterioration of a power storage element based on the derived self-discharge rate.

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