JP2017187462A - Estimation device and estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate an effective capacity or total reduction in the effective capacity through a computation that is easier than route computation.SOLUTION: An estimation device 50 is for estimating an effective capacity C or total reduction ΣY in the effective capacity C of a power storage device, and includes a computation processing unit 71 configured to compute the effective capacity C or the total reduction ΣY in the effective capacity C of the power storage device on the basis of approximation data that approximates a capacity variation curve La representing temporal variation of the effective capacity C or total reduction ΣY in the effective capacity C with a plurality of straight lines.SELECTED DRAWING: Figure 4

Description

  The technology disclosed in this specification relates to a technology for estimating the actual capacity of a power storage element or the total decrease in actual capacity.

  For example, it is known that a lithium ion secondary battery has an actual capacity (capacity that can be taken out from a state in which the secondary battery is fully charged) decreases from an initial value over time. It is not easy to measure the actual capacity of a battery during use, and it is required to estimate the actual capacity using measurable parameters. The main factors that decrease the actual capacity of the battery include cycle deterioration due to repeated charge / discharge and deterioration with time due to the passage of time after manufacture. As a method for estimating the actual capacity due to deterioration over time, there are estimation methods using the root rule and the Arrhenius rule. The root rule is a law in which the actual capacity decreases according to the route of elapsed time. Patent Document 1 below discloses a technique for estimating a battery deterioration rate using a root rule. The Arrhenius law is a law that the degree of decrease depends on the temperature.

Japanese Patent No. 5382208

When estimating the actual capacity of the power storage element or the total amount of decrease thereof using the route rule, it is necessary to perform route calculation. Therefore, it is necessary to mount a CPU having a high calculation capability, and the calculation load is large. A similar problem exists even in a secondary battery whose actual capacity or the total amount of reduction follows a predetermined curve.
The technology disclosed in the present specification has been created in view of the above-described problems, and an object thereof is to estimate the actual capacity of a power storage element or the total decrease amount of the actual capacity by a simple calculation.

  The estimation device disclosed in this specification is an estimation device that estimates the actual capacity of a power storage element or the total decrease in actual capacity, and shows the transition of the actual capacity or the transition of the total decrease in actual capacity with respect to elapsed time. An arithmetic processing unit is provided that calculates the actual capacity of the power storage element or the total decrease in the actual capacity based on approximate data obtained by approximating the capacity change curve with a plurality of straight lines.

  According to the estimation device disclosed in the present specification, the actual capacity or the total decrease amount of the actual capacity can be estimated with a simple calculation.

The perspective view of the battery module applied to Embodiment 1. FIG. Exploded perspective view of the battery module Block diagram showing the electrical configuration of the battery module Graph showing capacity change curve of secondary battery An enlarged view of a part of FIG. The figure which shows capacity fall amount map MA Figure showing secondary battery temperature data The flowchart figure which shows the flow of the estimation process of the total amount of reduction of the real capacity of a secondary battery The figure which shows the example of estimation of the total amount of reduction of the real capacity of a secondary battery The figure which shows 1st data in Embodiment 2. Diagram showing second data The graph which shows the capacity | capacitance change curve of the secondary battery applied to Embodiment 3. The figure which shows the correction data applied to Embodiment 4. The figure which shows transition of the actual capacity of each battery temperature in Embodiment 5. Figure showing the transition of the actual capacity of each battery temperature when the horizontal axis (time axis) is multiplied by a coefficient The figure which shows transition of the actual capacity | capacitance of each battery temperature when making a horizontal axis (time axis) the 1 / Nth power of elapsed time T Diagram showing coefficient corresponding to each battery temperature Figure showing the transition of the actual capacity of the reference temperature Diagram showing the slope data of each approximate line

(Outline of this embodiment)
First, an overview of the estimation device disclosed in the present embodiment will be described.
The estimation device is an estimation device that estimates an actual capacity of a power storage element or a total decrease in actual capacity, and a capacity change curve indicating a transition of an actual capacity or a transition of a total decrease in actual capacity with respect to elapsed time is represented by a plurality of straight lines. And an arithmetic processing unit that calculates the actual capacity of the power storage element or the total decrease in the actual capacity based on the approximate data approximated in.

  In this configuration, since the capacity change curve is approximated by a straight line, for example, route calculation is not necessary in calculating the actual capacity of the storage element or the total decrease in the actual capacity, and the calculation load on the calculation processing unit can be suppressed. .

  As one embodiment of the estimation device disclosed in the present embodiment, the capacity change curve is divided into a plurality of areas and approximated by a straight line, and the plurality of areas dividing the capacity change curve are an actual capacity or an actual capacity. This is a region in which the total decrease amount is divided by a predetermined value. In this embodiment, it is not necessary to count and hold the total elapsed time of the elapsed time, and it is easy to calculate the actual capacity of the power storage element or the total decrease amount of the actual capacity.

  As an embodiment of the estimation device disclosed in the present embodiment, the capacity change curve is provided for each temperature of the power storage element, and the arithmetic processing unit includes a plurality of capacity change curves corresponding to the temperature of the power storage element. Based on the approximate data approximated by the straight line, the actual capacity of the power storage element or the total decrease in the actual capacity is calculated. In this configuration, since the capacity change curve is provided for each temperature according to the Arrhenius law, the actual capacity of the power storage element or the total decrease in the actual capacity can be accurately estimated regardless of the temperature change.

  As an embodiment of the estimation device disclosed in the present embodiment, the slope of the straight line approximating the capacity change curve represents the amount of decrease in the actual capacity per unit time, and each region that divides the capacity change curve and For each battery temperature, a storage unit is provided that stores a capacity decrease amount map that represents the amount of decrease in actual capacity per unit time. In this configuration, by referring to the capacity decrease amount map, the actual capacity decrease amount per unit time can be obtained for each battery temperature.

  As an embodiment of the estimation device disclosed in the present embodiment, the arithmetic processing unit calculates the decrease amount of the actual capacity per predetermined time of the power storage element every time a predetermined time elapses after the power storage element is manufactured. Calculating the current value of the actual capacity by subtracting the decrease amount of the actual capacity per predetermined time from the previous value of the actual capacity, or calculating based on the temperature data of the storage element and the capacity decrease amount map, or The current value of the total decrease amount of the actual capacity is calculated by adding the decrease amount of the actual capacity per predetermined time to the previous value of the total decrease amount of the actual capacity.

  In this configuration, the current value of the actual capacity can be calculated by subtracting the amount of decrease in the actual capacity per predetermined time from the previous value of the actual capacity. Further, the total amount of decrease in actual capacity can be determined by determining the amount of decrease in actual capacity per predetermined time and adding it to the previous value. That is, the actual capacity or the total decrease amount of the actual capacity can be obtained by a very simple calculation.

  As one embodiment of the estimation device disclosed in the present embodiment, the slope of the straight line approximating the capacity change curve represents the amount of decrease in the actual capacity per unit time, and each region that divides the capacity change curve The first data representing the ratio of the amount of decrease in the actual capacity per unit time and the first amount representing the amount of decrease in the actual capacity per unit time for each battery temperature for one region dividing the capacity change curve. And a storage unit holding two data. In this configuration, the number of data to be retained can be reduced as compared with the capacity reduction amount map.

  As one embodiment of the estimation device disclosed in the present embodiment, the arithmetic processing unit, when a predetermined time elapses after the storage element is manufactured, the temperature data of the storage element, the first data, and the Based on the second data, the amount of decrease in the actual capacity per predetermined time of the electricity storage element is calculated, and the amount of decrease in the actual capacity per predetermined time is subtracted from the previous value of the actual capacity. The current value is calculated, or the current value of the total decrease in actual capacity is calculated by adding the decrease in the actual capacity per predetermined time to the previous value of the total decrease in actual capacity.

  In this configuration, the current value of the actual capacity can be calculated by subtracting the amount of decrease in the actual capacity per predetermined time from the previous value of the actual capacity. Further, the total amount of decrease in actual capacity can be determined by determining the amount of decrease in actual capacity per predetermined time and adding it to the previous value. That is, the actual capacity or the total decrease amount of the actual capacity can be obtained by a very simple calculation.

  As an embodiment of the estimation device disclosed in the present embodiment, the arithmetic processing unit corrects the data of the decrease amount of the actual capacity per unit time based on the SOC of the power storage element. In this configuration, since the data on the amount of decrease in the actual capacity per unit time is corrected according to the SOC, the estimation accuracy of the actual capacity or the total amount of decrease in the actual capacity is increased.

  As an embodiment of the estimation device disclosed in the present embodiment, the arithmetic processing unit includes a plurality of straight line slopes approximating a capacity change curve at a reference temperature of the power storage element, the temperature of the power storage element, The amount of decrease in the actual capacity per time at the temperature is calculated based on the conversion time obtained by converting the time that the power storage element elapses at the temperature into the time that elapses at the reference temperature. In this configuration, it is only necessary to hold data of a straight line approximating the capacity change curve for the reference temperature, and it is not necessary to hold data for other battery temperatures. For this reason, the number of data to be held can be reduced.

  As one embodiment of the estimation device disclosed in the present embodiment, the conversion time is longer as the temperature of the power storage element is higher. In this configuration, the higher the temperature, the longer the conversion time, and the calculated decrease amount of the actual capacity increases. Therefore, the amount of decrease in actual capacity due to temperature change can be accurately estimated.

  The arithmetic processing unit calculates the conversion time by multiplying a time corresponding to the temperature by a coefficient corresponding to the temperature. In this configuration, the conversion time can be obtained by a relatively simple calculation such as multiplication.

  Note that the present technology can be applied to an estimation method and an estimation program for an actual capacity or a total decrease in actual capacity.

<Embodiment 1>
Next, Embodiment 1 of the present invention will be described with reference to FIGS.
1. Description of Battery Module FIG. 1 is a perspective view of a battery module, FIG. 2 is an exploded perspective view of the battery module, and FIG. 3 is a block diagram showing an electrical configuration of the battery module.

  As shown in FIG. 1, the battery module 20 has a block-shaped battery case 21, and an assembled battery 30 including a plurality of secondary batteries 31 and a control board 28 are accommodated in the battery case 21. Yes. In the following description, when referring to FIG. 1 and FIG. 2, the vertical direction of the battery case 21 when the battery case 21 is placed horizontally without being inclined with respect to the installation surface is defined as the Y direction. The direction along the long side direction will be described as the X direction, and the depth direction of the battery case 21 will be described as the Z direction.

  As shown in FIG. 2, the battery case 21 includes a box-shaped case main body 23 that opens upward, a positioning member 24 that positions a plurality of secondary batteries 31, and an inner lid 25 that is mounted on the upper portion of the case main body 23. And an upper lid 26 mounted on the upper portion of the inner lid 25. In the case body 23, as shown in FIG. 2, a plurality of cell chambers 23A in which the respective secondary batteries 31 are individually accommodated are provided side by side in the X direction.

  As shown in FIG. 2, the positioning member 24 has a plurality of bus bars 27 disposed on the upper surface, and the positioning member 24 is disposed above the plurality of secondary batteries 31 disposed in the case body 23. The plurality of secondary batteries 31 are positioned and connected in series by a plurality of bus bars 27.

  As shown in FIG. 1, the inner lid 25 has a substantially rectangular shape in plan view, and has a shape with a height difference in the Y direction. A pair of terminal portions 22P and 22N to which harness terminals (not shown) are connected are provided at both ends of the inner lid 25 in the X direction. The pair of terminal portions 22P and 22N is made of, for example, a metal such as a lead alloy, 22P being a positive terminal portion and 22N being a negative terminal portion.

  Further, as shown in FIG. 2, the control cover 28 can be accommodated inside the inner lid 25, and the secondary battery 31, the control board 28, and the like can be obtained by attaching the inner cover 25 to the case body 23. Are to be connected.

  Next, the electrical configuration of the battery module 20 will be described with reference to FIG. The battery module 20 includes an assembled battery 30, a current sensor 41, a temperature sensor 43, and a battery management device (hereinafter referred to as BM) 50 that manages the assembled battery 30. The assembled battery 30 includes a plurality of lithium ion secondary batteries (an example of the “storage element” of the present invention) 31 connected in series.

  The current sensor 41 is connected in series with the assembled battery 30 via the connection line 35. The current sensor 41 is provided inside the battery case 21 and functions to detect a current flowing through the secondary battery 31. The temperature sensor 43 is a contact type or non-contact type, and functions to measure the temperature [° C.] of the secondary battery 31.

  The current sensor 41 and the temperature sensor 43 are electrically connected to the BM 50 through signal lines, and the detection values of the current sensor 41 and the temperature sensor 43 are configured to be taken into the BM 50. The current sensor 41 is provided in the battery case 21.

  The BM 50 includes a voltage detection circuit 60 and a control unit 70, and is provided on the control board 28. A power supply line (not shown) of the BM 50 is connected to the assembled battery 30, and the BM 50 receives power from the assembled battery 30.

  The voltage detection circuit 60 is connected to both ends of each secondary battery 31 via a detection line, and in response to an instruction from the control unit 70, the voltage of each secondary battery 31 and the total voltage of the assembled battery 30 are calculated. It performs the function of measuring.

  The control unit 70 includes a CPU (an example of the “arithmetic processing unit” of the present invention) 71 that is a central processing unit, and a memory (an example of the “storage unit” of the present invention) 73. The CPU 71 monitors the current, voltage, and temperature of the secondary battery 31 from the outputs of the current sensor 41, the voltage detection circuit 60, and the temperature sensor 43. Further, as will be described later, the total decrease ΣY of the actual capacity C of the lithium ion secondary battery 31 is estimated.

  The memory 73 is nonvolatile such as a flash memory or an EEPROM. The memory 73 stores a monitoring program for monitoring the secondary battery 31 and data necessary for executing these programs. Further, data of a capacity decrease amount map MA for estimating the total decrease amount ΣY of the actual capacity C of the secondary battery 31 is stored.

2. Linear Approximation of Capacity Change Curve The main factors that decrease the actual capacity C of the lithium ion secondary battery 31 are cycle deterioration due to repeated charge / discharge and deterioration with time due to elapsed time after manufacture. Here, the “real capacity C” is a capacity that can be taken out from a state in which the secondary battery is fully charged. Incidentally, it is said that the cause of deterioration over time is that a SEI (Solid electrolyte interface) film formed on the negative electrode of the lithium ion secondary battery 31 grows and becomes thicker with the passage of time after manufacture.

  For deterioration over time, there is an estimation method using a root rule. The root rule is a law in which the total decrease amount ΣY of the actual capacity C changes according to a route (for example, a square root) of the elapsed time T. The “elapsed time T” is the time that has elapsed since the battery was manufactured.

  FIG. 4 shows the transition of the total decrease amount ΣY of the actual capacity C with respect to the elapsed time T for the iron phosphate-based lithium ion secondary battery 31. Specifically, it is a T-ΣY correlation graph in which the horizontal axis (X axis) is the elapsed time T and the vertical axis (Y axis) is the total decrease amount ΣY of the actual capacity C, and the total decrease amount ΣY of the actual capacity C. The capacity change curve La representing the transition of is a root curve with respect to the elapsed time T.

  The capacity change curve La is provided for each battery temperature, La1 is a capacity change curve with a battery temperature of 0 [° C], La2 is a capacity change curve with a battery temperature of 25 [° C], and La3 is a battery temperature of 50 [° C]. ] Is a capacitance change curve.

  These capacity-temperature curves La1 to La3 are conducted at each battery temperature for an experiment to examine the transition of the total decrease amount ΣY of the actual capacity C with the lapse of time after manufacture of the iron phosphate-based lithium ion secondary battery 31. It was obtained by this. The iron phosphate lithium ion secondary battery 31 is a battery using lithium iron phosphate (LiFePO4) as a positive electrode active material and graphite as a negative electrode active material.

  In this embodiment, the capacity change curve La is divided into a plurality of regions E1 to E3 and approximated by a straight line. More specifically, the total reduced capacity ΣY is divided into three areas E1 to E3 by dividing each predetermined value (3 [Ah] in this example), and the capacity change curve La is a straight line A1 for each area E1 to E3. Approximate to ~ A3.

  That is, the capacitance change curve La1 is divided and approximated by three straight lines A11 to A31 corresponding to the regions E1 to E3. Further, the capacitance change curve La2 is approximated by being divided by three straight lines A12 to A32 corresponding to the regions E1 to E3. Further, the capacitance change curve La3 is approximated by being divided by three straight lines A13 to A33 corresponding to the regions E1 to E3.

  The straight lines A1 to A3 approximating the capacity change curve La can be obtained as straight lines connecting the points P corresponding to the upper limit value and the lower limit value of the corresponding region E in the capacity change curve La. For example, as shown in FIG. 5, in the case of straight lines A11 to A13 that approximate the range corresponding to the region E1, the origin O corresponding to the total decrease amount of the real capacity C being 0 [Ah] and the total decrease of the real capacity C It can be obtained as a straight line connecting points P1 to P3 on the capacitance change curves La1 to La3 corresponding to the amount 3 [Ah].

  Further, in the case of the straight line A22 that approximates the range corresponding to the region E2 in the capacity change curve La2, as shown in FIG. 5, the total decrease amount of the actual capacity C in the capacity change curve La2 is 3 [Ah]. It can be obtained as a straight line connecting the corresponding point P2 and the point P4 corresponding to the total decrease in capacity of 6 [Ah]. Similarly, in the case of the straight line A23 that approximates the range corresponding to the region E2 in the capacity change curve La3, as shown in FIG. 5, the total decrease amount of the actual capacity C is 3 [Ah] in the capacity change curve La3. It can be obtained as a straight line connecting the corresponding point P3 and the point P5 corresponding to the total decrease amount of the actual capacity C of 6 [Ah].

3. Capacity Reduction Map MA and Total Reduction ΣY Estimation Process The slopes of the straight lines A1 to A3 that divide the capacity change curve La indicate the reduction Y of the actual capacity C per unit time (per month in this example). Show. In the present embodiment, for each of the capacity change curves La1 to La3, the magnitudes of the slopes of the straight lines A11 to A33 that approximate the respective capacity change curves La1 to La3 are obtained, and the obtained results are converted into data as a capacity decrease amount map MA of the secondary battery 31. ing.

  As shown in FIG. 6, the capacity decrease amount map MA is obtained by determining the decrease amount Y of the actual capacity C per unit time for each of the regions E1 to E3 and the battery temperature dividing the capacity change curve La. For example, when the battery temperature is 25 [° C.], the reduction amount Y of the actual capacity C per unit time for each of the regions E1 to E3 is 2.3623 [Ah / momth], 0.7874 [Ah / momth], 0.4725 [Ah / momth], and these numerical values are the magnitudes of the inclinations of the three straight lines A12, A22, and A32 that approximate the capacitance change curve La2.

  The battery module 20 holds the data of the capacity decrease amount map MA shown in FIG. 6 in advance in the memory 73 of the BM 50. Then, the CPU 71 of the control unit 70 estimates the total decrease amount ΣY of the actual capacity C of the secondary battery 31 due to deterioration with time based on the temperature data of the secondary battery and the capacity decrease amount map MA ( Steps S10 to S30 in FIG. 8 are performed.

  The estimation process of the total decrease amount ΣY includes the processes of S10 to S30 as shown in FIG. 8. First, in S10, every time a predetermined time (one month as an example) elapses after the battery is manufactured. Based on the output of the temperature sensor 43, a process of calculating an average temperature of the secondary battery 31 per predetermined time (one month as an example) is performed.

  Thereafter, in S20, a process of calculating the decrease amount Y of the actual capacity C per predetermined time (one month as an example) of the secondary battery 31 based on the battery temperature data and the capacity decrease amount map MA is performed. Is called. In S30, the decrease Y of the actual capacity C per predetermined time (one month as an example) calculated from the battery temperature data and the capacity decrease map MA is set to the previous value of the total decrease ΣY. By adding, the current value of the total decrease amount ΣY can be calculated.

  More specifically, immediately after manufacturing the battery, the total decrease amount ΣY of the actual capacity C is 0 [Ah], and the section of the total decrease amount ΣY of the secondary battery 31 is included in the region E1. Therefore, the reduction amount Y of the actual capacity C is 0.5241 [Ah / month], 2.3623 [Ah / month], and 8.4343 [Ah] for the period from the manufacture of the battery until one month elapses. / Month].

  FIG. 7 shows the average temperature of each month of the secondary battery 31 after the battery is manufactured. In the example in the figure, the average temperature of the first month is 0 [° C.]. Therefore, in this case, the decrease amount of the actual capacity C per month is 0.5241 [Ah / month], and the total decrease amount ΣY of the actual capacity C at the time when one month has elapsed after the battery is manufactured is As shown in FIG. 9, 0.5241 [Ah] is obtained.

  When the total decrease amount ΣY of the actual capacity C at the time when one month has elapsed after the battery manufacture is 0.5241 [Ah], the classification of the total decrease amount ΣY of the secondary battery 31 is the region E1 (0-3 [ Ah]). Therefore, the amount of decrease in the actual capacity C per month is 0.5241 [Ah / month] and 2.3623 [Ah / month] for the period from one month to two months after the battery is manufactured. , 8.4343 [Ah / month].

  In the example of FIG. 7, the average temperature in the second month after battery manufacture is 25 [° C.]. Therefore, in this case, the decrease amount of the actual capacity C is 2.3623 [Ah / month] for the second month after the battery is manufactured. Therefore, the total decrease amount ΣY of the actual capacity C at the time when two months have elapsed after the battery manufacture is 2 months from the total decrease amount ΣY of the actual capacity C at the time when one month has elapsed after the battery manufacture. A numerical value obtained by adding the reduction amount Y of the actual capacity C of the eye, that is, 0.5241 [Ah] +2.3623 [Ah], and as shown in FIG. 9, 2.8864 [Ah].

  When the total decrease amount ΣY of the actual capacity C is 2.8864 [Ah] after two months have elapsed since the battery was manufactured, the classification of the total decrease amount ΣY of the secondary battery 31 is the region E1 (0-3). [Ah]). For this reason, the amount of decrease in the actual capacity C per month is 0.5241 [Ah / month], 2.3623 [Ah / month] One of 8.4343 [Ah / month].

  In the example of FIG. 7, the average temperature in the third month after the manufacture of the battery is 25 [° C.]. Therefore, in this case, the decrease Y of the actual capacity C per month is 2.3623 [Ah / month] for the third month after the battery is manufactured. Therefore, the total decrease amount ΣY of the actual capacity C at the time when three months have elapsed after the battery manufacture is the third month with respect to the total decrease amount ΣY of the actual capacity C at the time when two months have elapsed after the battery manufacture. The value obtained by adding the actual capacity C reduction amount Y, that is, 2.8864 [Ah] +2.3623 [Ah], is 5.2487 [Ah] as shown in FIG.

  When the total decrease amount ΣY of the actual capacity C is 5.2487 [Ah] after three months have elapsed since the battery was manufactured, the classification of the total decrease amount ΣY of the secondary battery 31 is the region E2 (3-6 [Ah]). Therefore, the amount of decrease in the actual capacity C per month is 0.1747 [Ah / month] and 0.7874 [Ah / month] for a period of 3 to 4 months after the battery is manufactured. 2.8114 [Ah / month].

  In the example of FIG. 7, the average temperature in the fourth month after the manufacture of the battery is 25 [° C.]. Accordingly, in this case, the decrease Y of the actual capacity C per month is 0.7874 [Ah / month] for the fourth month after the battery is manufactured. Therefore, the total decrease amount ΣY of the actual capacity C at the time when four months have elapsed after the battery manufacture is the fourth month relative to the total decrease amount ΣY of the actual capacity C at the time three months have elapsed after the battery manufacture. The value obtained by adding the actual capacity C reduction amount Y, that is, 5.2487 [Ah] +0.7874 [Ah], is 6.0361 [Ah] as shown in FIG.

  As described above, the total decrease amount ΣY of the actual capacity C is obtained by adding the decrease amount of the actual capacity C per month obtained from the capacity decrease amount map MA to the total decrease amount ΣY until the previous month. The current value of can be obtained.

  In the present embodiment, the capacity change curves La1 to La3 are approximated by a plurality of straight lines A11 to A33. Therefore, in calculating the actual capacity C or the total decrease amount ΣY of the actual capacity C, no route calculation is required, and the control unit The calculation load of 70 can be suppressed.

  In the first embodiment, the capacity change curve La is divided in the Y-axis direction. That is, the total decrease amount ΣY is divided into regions E1 to E3 divided by a predetermined value. In this way, there is no need to count and hold the total elapsed time of the elapsed time T, and there is an advantage that the total decrease amount ΣY of the actual capacity C can be easily calculated. That is, when the capacity change curve La is divided in the X-axis direction (when the elapsed time T is divided by a predetermined value), the total elapsed time of the elapsed time T can be calculated to obtain the total decrease amount ΣY of the actual capacity C. Although it is necessary to count and hold, in this example, there is no such need.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, for each of the capacity change curves La1 to La3, the magnitudes of the slopes of the straight lines A11 to A33 that approximate the respective capacity change curves La1 to La3 are obtained, and the obtained results are converted into data as a capacity decrease amount map MA of the secondary battery 31. Held.

  Here, regarding the amount of decrease Y of the actual capacity C per unit time, the ratio K between the regions E to E3 is as follows when the battery temperature is 25 [° C.].

Y1 = 2.623, Y2 = 0.7874, Y3 = 0.4725
K = Y1: Y2: Y3 = “1.000”: “0.3333”: “0.2000”
Y1 to Y3 are reduction amounts of the actual capacity C per unit time in the respective regions E1 to E3.

  On the other hand, when the battery temperature is 0 [° C.], the ratio K is “1.000”: “0.3333”: “0.2000”, and when the battery temperature is 50 [° C.], the ratio K is Becomes “1.000”: “0.3333”: “0.2000”. Thus, the ratio K of the reduction amounts Y1 to Y3 of the actual capacity C per unit time between the regions E1 to E3 is constant regardless of the battery temperature.

  In the second embodiment, paying attention to the property that the ratio K of the decrease amounts Y1 to Y3 of the actual capacity C is substantially constant regardless of the battery temperature, the data of the capacity decrease amount map MA shown in FIG. And the second data shown in FIG. That is, in the first embodiment, the data of the capacity decrease amount map MA shown in FIG. 4 is stored in the memory 73, but in the second embodiment, instead of the capacity decrease amount map MA, it is shown in FIG. The first data and the second data shown in FIG. 11 are held.

  As shown in FIG. 10, the first data is data representing the ratio K of the decrease amounts Y1 to Y3 of the actual capacity C per unit time for each of the areas E1 to E3 that divide the capacity change curve La. In this example, a numerical value of 25 [° C.] is described as a representative value of the ratio K.

  In addition, as shown in FIG. 11, the second data includes an actual capacity C per unit time for each battery temperature in an area E1 (total decrease amount: 0 to 3 Ah) that divides the capacity change curve L. This is data representing the decrease amount Y of the.

  If the first data shown in FIG. 10 and the second data shown in FIG. 11 are held in the memory 73, the reduction amount Y of the actual capacity C per unit time held in FIG. By multiplying the ratio K, the reduction amounts Y2 and Y3 of the actual capacity C per unit time can be calculated for other areas E2 and E3 which are not held in FIG.

  For example, when the battery temperature is 25 ° C., the ratio of the decrease amount of the actual capacity C in the region E2 to the region E1 (0) with respect to the decrease amount of the actual capacity C per unit time in the region E1 (Y1 = 2.623). ., 3333), the reduction amount (Y2 = 0.7874) of the actual capacity C per unit time in the region E2 is obtained. Further, by multiplying the decrease amount of the actual capacity C per unit time in the region E1 (Y1 = 2.623) by the ratio (0.2000) of the decrease amount of the actual capacity C of the region E3 to the region E1. A reduction amount (Y3 = 0.725) of the actual capacity C per unit time in the region E3 is obtained.

  Further, since the ratio K of the decrease amounts K1 to K3 of the actual capacity C between the regions E1 to E3 is substantially constant regardless of the battery temperature, the battery temperature is set to 25 [25] such as 0 [C] or 50 [C]. Other than [° C.], the reduction amounts Y2 and Y3 of the actual capacity C per unit time can be calculated for each of the regions E2 and E3 dividing the capacity change curve La by the same calculation as the above calculation method.

  Note that calculating the total decrease amount ΣY of the actual capacity C is the same as in the first embodiment, and in the second embodiment, the decrease amount of the actual capacity C per predetermined time using the first data and the second data. The current value of the total decrease amount ΣY is calculated by obtaining Y and adding it to the previous value of the total decrease amount ΣY.

  As described above, in the second embodiment, instead of the capacity decrease amount map MA, the first data shown in FIG. 10 and the second data shown in FIG. 11 are held, so the data held in the memory 73 is reduced. I can do it.

  In the example of Embodiment 1, the example which has three types of temperature patterns of La1-La3 as the capacity | capacitance change curve La was shown. In addition, an example is shown in which each capacitance change curve La1 to La3 is divided into three and approximated by a straight line. If the capacity change curve La is divided into 10 and has 100 temperature patterns, it is necessary to have “10 × 100 ways” of data as the capacity decrease amount map MA. In the configuration of the second embodiment, even when the capacity change curve La is divided into 10 and has 100 kinds of temperature patterns, it is only necessary to have “10 + 100 ways” data. That is, in this example, the number of data stored in the memory 73 can be suppressed to about 1/9, which is extremely effective for data reduction.

<Embodiment 3>
Next, Embodiment 3 of the present invention will be described with reference to FIG.
In the first embodiment, an example in which the total decrease amount ΣY of the actual capacity C with the passage of the elapsed time T is calculated is shown. In the third embodiment, the actual capacity C is calculated as the elapsed time T elapses.

  FIG. 12 is a TC correlation graph of the iron phosphate lithium ion secondary battery 31 with the horizontal axis (X axis) representing elapsed time T and the vertical axis (Y axis) representing actual capacity C. As shown in FIG. 12, the capacity change curve Lb representing the transition of the actual capacity C is an inverted curve obtained by turning back the capacity change curve La shown in FIG. 4 along the X axis, and the elapsed time T is the same as the capacity change curve La. Is the root curve for.

  As shown in FIG. 12, the capacitance change curve Lb can be approximated by being divided into a plurality of regions E1 to E3, like the capacitance change curve La. In the example of FIG. 12, the capacity change curve Lb1 is divided and approximated by three straight lines B11 to A31 corresponding to the regions E1 to E3. Further, the capacity change curve Lb2 is approximated by being divided by three straight lines B12 to A32 corresponding to the regions E1 to E3. Further, the capacity change curve Lb3 is divided and approximated by three straight lines B13 to B33 corresponding to the regions E1 to E3.

  From the above, as in the first embodiment, for each of the capacity change curves Lb1 to Lb3, the magnitudes of the slopes of the straight lines B11 to B33 approximating the respective capacity change curves Lb1 to Lb3 are obtained. If it is converted into data as the decrease amount map MB, the decrease amount Y of the actual capacity C per predetermined time can be calculated using the capacity decrease amount map MB. Then, the current value of the actual capacity C can be calculated by subtracting the calculated decrease Y of the actual capacity C from the previous value of the actual capacity C.

<Embodiment 4>
Next, Embodiment 4 of the present invention will be described with reference to FIG. The decrease amount Y of the actual capacity C per unit time may vary depending on the SOC (State of charge) of the lithium ion secondary battery 31. Therefore, in the fourth embodiment, based on the SOC value of the secondary battery 31, a process of correcting the decrease amount Y of the actual capacity C per predetermined time (one month) is performed.

  Specifically, in the fourth embodiment, correction data shown in FIG. 13 is stored in advance in the memory 73 in addition to the capacity decrease amount map MA shown in FIG. The correction data is stored in association with the SOC of the secondary battery 31 with the correction coefficient α. Note that the decrease Y of the actual capacity C tends to be smaller as the SOC is lower if the elapsed time T is the same. Therefore, as shown in FIG. 13, the magnitude relationship of the correction coefficients is α1 <α2 <α3. It becomes.

  As in the first embodiment, the control unit 70 refers to the capacity decrease amount map MA and calculates the decrease amount Y of the actual capacity C for each month after the battery is manufactured. In addition, the control unit 70 performs processing for calculating the average value of the SOC for each month after the battery is manufactured. Then, the correction coefficient α corresponding to the SOC is read out from the correction data shown in FIG. 13, and the reduction amount Y of the actual capacity C in each month is corrected.

  Then, the current value of the total decrease amount ΣY is calculated by adding the corrected decrease amount Y to the previous value of the total decrease amount ΣY. As described above, in the fourth embodiment, the amount of decrease Y of the actual capacity C is corrected according to the SOC. Therefore, the total amount of decrease ΣY of the actual capacity C of the secondary battery 31 can be accurately calculated as compared with the case where correction is not performed. Can be estimated. The SOC of the secondary battery 31 can be obtained by using a so-called current integration method or OCV method.

<Embodiment 5>
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
FIG. 14 is a TC correlation graph of the iron phosphate lithium ion secondary battery 31 with the elapsed time T on the horizontal axis and the actual capacity C on the vertical axis, and the battery temperatures are 25 [° C.] and 45 [ The transition of the actual capacity C with respect to the elapsed time T is shown for three patterns [° C.] and 60 [° C.]. As shown in FIG. 14, the actual capacity C decreases with the lapse of time after the battery is manufactured, but even if the elapsed time T is the same, the capacity decrease is more remarkable as the battery temperature is higher. That is, the higher the battery temperature, the lower the actual capacity C “accelerated”.

  FIG. 15 is a TC correlation graph of the iron phosphate-based lithium ion secondary battery 31 with the elapsed time T on the horizontal axis and the actual capacity C on the vertical axis. The horizontal axis (X axis) is shown in FIG. The battery temperature is changed every 25 [° C.], 45 [° C.], and 60 [° C.]. Specifically, with respect to the horizontal axis of the battery temperature 25 [° C.], the battery temperature 45 [° C.] times the horizontal axis “k1” times, and at the battery temperature 60 [° C.], the horizontal axis times “k 2” times. ing. Note that k2> k1> 1.

  As shown in FIG. 15, when the horizontal axis (time axis) is multiplied by a predetermined “coefficient k”, the transitions of the actual capacity C substantially match even when the battery temperature is different. This means, for example, that “1 hour” at a battery temperature of 45 [° C.] corresponds to “k × 1 hour” at a battery temperature of 25 [° C.]. That is, when the battery temperature is 45 [° C.], the reduction amount of the actual capacity C per “hour” is converted into the reduction amount of the actual capacity C per “k × 1 hour” when converted to the battery temperature 25 [° C.]. Equivalent to.

The coefficient k for each battery temperature can be calculated by the following method.
(A) The N-th root of the elapsed time T and the actual capacity C of each battery temperature determine the value of N that is proportional.
(B) A linear approximation formula of the actual capacity C is determined for each battery temperature.
(C) The ratio M of the slope with respect to the linear approximation formula of the reference temperature is determined for the linear approximation formula of each battery temperature.
(D) The coefficient k is calculated from the values of N and M.

  An example of calculating the coefficient k of battery temperatures 40 [° C.] and 60 [° C.] with 25 [° C.] as the reference temperature is shown below.

  First, while changing the multiplier N, the correlation between the N-th root of the elapsed time T and the actual capacity C is examined, and each battery temperature 25 [° C.], 45 [° C.], 60 [° C.] is proportional to N Identify the value.

FIG. 16 is an ^N √TC correlation graph of the iron phosphate lithium ion secondary battery 31 with the horizontal axis representing the Nth root of the elapsed time T and the vertical axis representing the actual capacity C. In [C], 45 [C], and 60 [C], the transition of the actual capacity C is shown by a straight line. The value of N is “3.1215” as an example.

From FIG. 16, a linear approximation formula of the actual capacity C at each battery temperature can be obtained as follows.
Y = −a1X + b (1)
Y = −a2X + b (2)
Y = −a3X + b (3)
Note that (1) is a linear approximation formula of the actual capacity C at a battery temperature of 25 [° C.], (2) is a linear approximation formula of the actual capacity C at a battery temperature of 45 [° C.], and (3) is a battery temperature of 60 [° C.]. Is a linear approximation of the actual capacity C.

  Next, from the linear approximation formulas (1) to (3), the slope ratio M of the reference temperature linear approximation formula for each battery temperature linear approximation formula is determined.

The slope ratio M of each battery temperature is as follows.
M1 = a2 / a1 (4)
M2 = a3 / a1 (5)

Since the values of N and M can be obtained as described above, the coefficient k can be obtained for battery temperatures of 45 [° C.] and 60 [° C.] from the following equations (6) and (7).
k _{45 ℃} = M1 ^N (6)
k _{60 ° C} = M2 ^N (7)

  In the fifth embodiment, as shown in FIG. 17, the value of the coefficient k is calculated in advance for each battery temperature, and the data is stored in the memory 73.

  The coefficient k increases as the battery temperature increases. In this example, 25 [° C.] is set as a reference temperature. When the battery temperature is lower than 25, the coefficient k is 1 or less, and when it is higher, it is 1 or more. Therefore, k1 <k2 <1 and 1 <k3 <k4... K8 <k9.

  FIG. 18 is a TC correlation graph of the iron phosphate lithium ion secondary battery 31 with the elapsed time T on the horizontal axis (X axis) and the actual capacity C on the vertical axis (Y axis). A curve Ld shows the transition of the actual capacity C at the reference temperature of 25 [° C.].

  In the fifth embodiment, the capacity change curve Ld is divided into a plurality of regions E1 to E3 and approximated in common with the first to fourth embodiments, and the capacity change curve Lc corresponds to each of the regions E1 to E3. It is divided and approximated by two straight lines D1 to D3.

  The memory 73 stores data on the slopes d1 to d3 of the three approximate lines D1 to D3 that are obtained by dividing and approximating the capacity change curve Ld of the reference temperature 25 [° C.] together with the coefficient k data for each battery temperature. (See FIGS. 17 and 19).

In the fifth embodiment, the CPU 71 of the control unit 70 estimates the actual capacity C in five steps (A) to (E).
(A) Calculation of slope d of approximate line D at reference temperature corresponding to actual capacity C (B) Calculation of coefficient k corresponding to battery temperature (C) Predetermined time W when secondary battery 31 elapses at battery temperature Converted to the time elapsed at the reference temperature (D) Calculates the decrease Yw of the actual capacity C per predetermined time W at the battery temperature (E) Calculates the total decrease ΣY of the actual capacity C

  Hereinafter, an estimation example of the actual capacity C will be described with reference to FIGS. Here, the initial value of the actual capacity C, the total decrease amount of the actual capacity at the previous estimation (total decrease amount from the initial value), and the battery temperature are as follows.

  The initial value of the actual capacity C is C0. In the previous time, it is assumed that the actual capacity C is estimated at time t1 shown in FIG. 18, and the total decrease amount ΣY1 of the actual capacity C at the previous estimation time t1 is in the range of e1 <ΣY1 <e2. In the following example, the amount of decrease Y in the actual capacity C per predetermined time W is calculated from the previous estimation time t1. Further, the battery temperature of the secondary battery 31 detected by the temperature sensor 43 in the predetermined time W is 40 [° C.].

  The slope d of the approximate line D at the reference temperature corresponding to the actual capacity C can be obtained from the total decrease amount ΣY1 of the actual capacity C at the previous estimation time t1 and the data of FIG. In this example, the total decrease amount ΣY1 at the previous estimation time t1 is in the range of e1 <ΣY1 <e2. Accordingly, from FIG. 19, the approximate straight line at the reference temperature corresponding to the actual capacity C is D2, and its slope is “d2”.

  The coefficient k corresponding to the battery temperature can be obtained from the battery temperature of the secondary battery 31 measured by the temperature sensor 43 and the data shown in FIG. In this example, since the battery temperature during the predetermined time W is 40 [° C.], the coefficient is “k5” from FIG.

  The time that the secondary battery 31 elapses at the battery temperature corresponds to the time obtained by multiplying the time elapsed at the reference temperature by the coefficient k. Therefore, the conversion time Wt obtained by converting the predetermined time W that the secondary battery 31 elapses at the battery temperature into the elapsed time at the reference temperature is expressed by the following equation (8).

  Wt = k × W (8)

  The slope d of the approximate straight line D indicates the amount of decrease in the actual capacity C per unit time. Therefore, by multiplying the conversion time Wt by the slope d of the approximate straight line D, the reduction amount Yw of the actual capacity C per predetermined time W at the battery temperature is calculated as shown in the following equation (9). I can do it.

  Reduction amount of actual capacity C Yw = (k × W) × d (9)

  Further, assuming that the predetermined time W = unit time (for example, 1 [month]), the reduction amount Yw of the actual capacity C can be expressed by the following equation (10).

  Reduction amount of actual capacity C Yw = k × d (10)

  In the above example, since the coefficient is “k5” and the slope of the approximate line is “d2”, the decrease amount of the actual capacity C from the previous estimation time t1 until the unit time of 1 [month] elapses. Yw is “k5” × “d2”.

  As described above, when the predetermined time = unit time, the actual value per predetermined time (unit time) at the battery temperature is obtained by multiplying the “slope d of the approximate line D” by the “coefficient k corresponding to the battery temperature”. The decrease amount Yw of the capacity C can be calculated.

  Further, the total decrease amount ΣY2 of the actual capacity C at time t2 can be calculated by adding the calculated decrease amount Yw of the actual capacity C to the total decrease amount ΣY1 of the actual capacity C at the previous estimation time t1. I can do it. Then, as shown in the following equation (11), the actual capacity C at time t2 can be estimated by subtracting the total decrease amount ΣY2 from the initial value C0 of the actual capacity C.

  C = C0−ΣY2 (11)

  The CPU of the control unit 70 estimates the actual capacity C by performing the above processing every predetermined time (unit time).

  In the fifth embodiment, the capacity change curve data only needs to be retained for the reference temperature, and other battery temperatures do not need to retain the capacity change curve data. That is, it is not necessary to store the data of the slope d of the approximate straight line D shown in FIG. 19 for each battery temperature. Therefore, the number of data stored in the memory 73 can be significantly reduced, which is effective.

  The coefficient k increases as the battery temperature increases, and the conversion time Wt increases. Therefore, since the amount of decrease in actual capacity increases as the battery temperature increases, the amount of decrease Yw in actual capacity C due to temperature change can be accurately estimated.

  Further, since the conversion time Wt and the amount of decrease Yw of the actual capacity C per predetermined time can be obtained by a comparatively simple calculation such as multiplication of a coefficient, a predetermined time, and a slope, the calculation load on the control unit 70 is also small.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the first to third embodiments, an iron phosphate-based lithium ion secondary battery is exemplified as an example of the “storage element”. The present invention can be widely applied as long as the transition of the total decrease amount ΣY of the actual capacity C with respect to the elapsed time T is a lithium ion secondary battery having characteristics according to a root rule or a predetermined curve. The present invention can also be applied to a lithium ion secondary battery. A ternary lithium ion secondary battery uses a lithium-containing metal oxide containing elements of Co, Mn, and Ni as a positive electrode active material, and uses graphite, carbon, or the like as a negative electrode active material.

  Further, if the transition of the total decrease amount ΣY of the actual capacity C with respect to the elapsed time T is a secondary battery having a characteristic according to a predetermined curve, it can be applied to other secondary batteries such as lead storage batteries, capacitors, and the like. .

  (2) In the first to third embodiments, the capacity change curves La and Lb are approximated by dividing them into three regions E1 to E3. The number of divisions of the capacitance change curve La is not limited to “3”, and may be more than that. Further, the region E that divides the capacitance change curve La is not necessarily equal, and may be dense. For example, the large range of the capacity change curves La and Lb is to narrow the region E to be divided and increase the number of divisions, while the range close to a straight line is to widen the region E to be divided and reduce the number of divisions. Also good.

  (3) In the first embodiment, the example in which the decrease amount Y of the actual capacity C is obtained every month after the battery is manufactured is shown. The interval for obtaining the decrease amount Y of the actual capacity C may be every two months or every three months.

20 ... Battery module 30 ... Battery 31 ... Secondary battery (an example of the “storage element” of the present invention)
50 ... Battery manager (an example of the “estimation device” of the present invention)
60 ... voltage detection circuit 70 ... control unit 71 ... CPU (an example of the "arithmetic processing unit" of the present invention)
73. Memory (an example of the “storage unit” of the present invention)

Claims (12)

An estimation device for estimating an actual capacity of a storage element or a total decrease in actual capacity,
Calculation that calculates the actual capacity of the storage element or the total decrease in the actual capacity based on approximate data obtained by approximating the capacity change curve indicating the transition of the actual capacity with respect to the elapsed time or the transition of the total decrease in the actual capacity with a plurality of straight lines. An estimation apparatus including a processing unit. The estimation device according to claim 1,
The capacity change curve is divided into a plurality of regions and approximated by a straight line,
The plurality of areas into which the capacity change curve is divided are areas where the actual capacity or the total decrease amount of the actual capacity is divided by a predetermined value. The estimation apparatus according to claim 1 or 2, wherein
The capacity change curve is provided for each temperature of the power storage element,
The calculation unit is an estimation device that calculates an actual capacity of a power storage element or a total decrease in the actual capacity based on approximate data obtained by approximating a capacity change curve corresponding to the temperature of the power storage element with a plurality of straight lines. An estimation apparatus according to claim 3, wherein
The slope of the straight line approximating the capacity change curve represents the amount of decrease in actual capacity per unit time,
An estimation apparatus comprising: a storage unit that holds a capacity decrease amount map that represents an actual capacity decrease amount per unit time for each region and each battery temperature that divides the capacity change curve. An estimation apparatus according to claim 4, wherein
The arithmetic processing unit includes:
After the manufacture of the storage element, every time a predetermined time elapses, the amount of decrease in the actual capacity of the storage element per predetermined time is calculated based on the temperature data of the storage element and the capacity decrease amount map,
Calculate the current value of the actual capacity by subtracting the amount of decrease in the actual capacity per predetermined time from the previous value of the actual capacity, or the actual capacity per predetermined time with respect to the previous value of the total decrease in actual capacity An estimation apparatus that calculates a current value of a total decrease amount of the actual capacity by adding the decrease amounts. An estimation apparatus according to claim 3, wherein
The slope of the straight line approximating the capacity change curve represents the amount of decrease in the actual capacity per unit time,
The first data representing the ratio of the amount of decrease in the actual capacity per unit time of each area dividing the capacity change curve, and the area per unit time for each battery temperature for one area dividing the capacity change curve An estimation apparatus comprising: a storage unit that holds second data representing the amount of decrease in actual capacity. The estimation apparatus according to claim 6, wherein
The arithmetic processing unit includes:
Each time a predetermined time elapses after the manufacture of the storage element, the actual capacity per unit time of the storage element is determined based on the temperature data of the storage element, the first data, and the second data. Calculate the amount of decline,
Calculate the current value of the actual capacity by subtracting the amount of decrease in the actual capacity per predetermined time from the previous value of the actual capacity, or the actual capacity per predetermined time with respect to the previous value of the total decrease in actual capacity An estimation apparatus that calculates a current value of a total decrease amount of the actual capacity by adding the decrease amounts. An estimation apparatus according to claim 4 to claim 7, wherein
The arithmetic processing unit includes:
An estimation device that corrects data of a decrease in actual capacity per unit time based on the SOC of the power storage element. The estimation device according to claim 2,
The arithmetic processing unit includes:
Slopes of a plurality of straight lines approximating a capacity change curve at a reference temperature of the storage element;
The temperature of the electricity storage element;
An estimation device that calculates a decrease amount of the actual capacity per time under the temperature based on a conversion time obtained by converting a time when the power storage element elapses at the temperature into a time elapsed at a reference temperature. An estimation apparatus according to claim 9, wherein
The conversion device is an estimation device that is longer as the temperature of the power storage element is higher. An estimation device according to claim 9 or claim 10, wherein
The arithmetic processing unit includes:
An estimation apparatus that calculates the conversion time by multiplying a time corresponding to the temperature by a coefficient corresponding to the temperature. An estimation method for estimating an actual capacity of a storage element or a total decrease in actual capacity,
Based on the approximate data obtained by approximating the capacity change curve indicating the transition of the actual capacity with respect to the elapsed time or the transition of the total decrease in the actual capacity with a plurality of straight lines, the actual capacity of the power storage element or the total decrease in the actual capacity is calculated. Estimation method.

Images