Method for generating estimation formula of full charge capacity of electric vehicle after battery deterioration

Abstract

To provide a method for generating a highly accurate estimation formula of a full charge capacity after battery deterioration.SOLUTION: A method for generating an estimation formula includes the steps of: preparing a first estimation formula which includes a prescribed coefficient and a first battery variable regarding a battery status and acquires a first estimation value of a full charge capacity after battery deterioration and a second estimation formula which includes an undetermined coefficient and a second battery variable regarding the battery status and acquires a second estimation value of the full charge capacity after battery deterioration; collecting actual data of the first battery variables and the second battery variables from L pieces of electric vehicles; specifying the undetermined coefficient through multiple regression analysis using K pieces of the actual data regarding the first battery variables in the L pieces of actual data and the first estimation formula; correcting the undermined coefficient which is specified to increase correlation between the first estimation value and the second estimation value by use of (L-K) pieces of actual data; and finally obtaining the second estimation formula with the specified and corrected undetermined coefficient.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a method for creating an estimation formula for the fully charged capacity of an electric vehicle battery after deterioration.

Background Art

[0002] The fully charged capacity of a battery used for a long time decreases from the fully charged capacity at the start of use (initial fully charged capacity) due to deterioration. Even if it is left unused for a long time, the fully charged amount becomes lower than the initial fully charged capacity due to deterioration. In this specification, the fully charged capacity of a battery after a predetermined period is referred to as the "fully charged capacity after deterioration". An example of a technology for estimating the fully charged capacity after deterioration is disclosed in Patent Document 1. The method of Patent Document 1 estimates the fully charged capacity after deterioration using the charge-discharge history of the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] This specification provides a technology for estimating the fully charged capacity of a battery after deterioration with higher accuracy than before. In this specification, the fully charged capacity after deterioration is expressed as a percentage when the initial fully charged capacity is 100 [%].

Means for Solving the Problems

[0005] The method for creating the estimation formula disclosed in this specification includes the following seven steps.

[0006] (First Step) Prepare a first estimation formula that includes a first battery variable related to a default coefficient and the state of the battery and obtains a first estimated value of the fully charged capacity after battery degradation, and a second estimation formula that includes an undetermined coefficient and a second battery variable related to the state of the battery and obtains a second estimated value of the fully charged capacity after battery degradation. Note that the specific structures of the first estimation formula and the second estimation formula are shown in the "Detailed Description of the Invention".

[0007] (Second Step) Collect performance data of the first battery variable and the second battery variable from L electric vehicles. (Third Step) Substitute K pieces of performance data related to the first battery variable among the L pieces of performance data into the first estimation formula to obtain K first estimated values. (Fourth Step) Identify the undetermined coefficient by multiple regression analysis from the second estimation formula into which K pieces of performance data related to the second battery variable among the L pieces of performance data and the K first estimated values are substituted. (Fifth Step) Substitute (L - K) pieces of performance data related to the second battery variable in the performance data into the second estimation formula including the identified undetermined coefficient to obtain (L - K) second estimated values, and substitute (L - K) pieces of performance data related to the first battery variable into the first estimation formula to obtain new first estimated values. (Sixth Step) Correct the identified undetermined coefficient so that the correlation between the (L - K) first estimated values and the second estimated values obtained in the fifth step becomes strong. (Seventh Step) Use the second estimation formula including the identified and corrected undetermined coefficient and the second battery variable as an estimation formula for the fully charged capacity after battery degradation.

[0008] Note that the first battery variable and the second battery variable related to the state of the battery include the elapsed time and the amount of energized electricity for each temperature section obtained by dividing the battery temperature into a plurality of temperature sections.

[0009] Since the estimation formula creation method disclosed in this specification adopts battery variables defined for each temperature section of the battery, the fully charged capacity after degradation can be estimated with high accuracy. Also, K pieces of performance data out of the L pieces of performance data are used for identifying the undetermined coefficient, and the remaining (L - K) pieces of performance data are used for correcting the identified undetermined coefficient. This also contributes to estimating the fully charged capacity after degradation with high accuracy.

[0010] The details and further improvements of the technology disclosed in this specification will be described in the following "Mode for Carrying Out the Invention".

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0012] As described above, in this specification, the fully charged capacity after deterioration is expressed as a ratio to the initial fully charged capacity. That is, the initial fully charged capacity is set to 100.

[0013] The method for creating an estimation formula disclosed in this specification includes seven steps. Figure 1 shows a flowchart of the procedure of the method for creating an estimation formula. Each step will be described in detail and specifically.

[0014] (First step) In the first step, a first estimation formula and a second estimation formula for calculating an estimated value of the fully charged capacity after deterioration are prepared (step S1). The first estimation formula includes a default coefficient and a first battery variable related to the state of the battery. The estimated value of the fully charged capacity after deterioration obtained by the first estimation formula is referred to as the first estimated value. The second estimation formula includes an undetermined coefficient and a second battery variable related to the state of the battery. The estimated formula of the fully charged capacity after deterioration obtained by the second estimation formula is referred to as the second estimated value.

[0015] The ultimate goal of the method for creating an estimation formula in this embodiment is to collect measured values (i.e., actual performance data) corresponding to the first battery variable and the second battery variable from a plurality of electric vehicles actually used by users, and use these actual performance data and the first estimation formula to identify and optimize the undetermined coefficient. By obtaining the optimized value of the undetermined coefficient, the second estimation formula can estimate the fully charged capacity after deterioration with high accuracy. The second estimation formula including the identified and optimized undetermined coefficient is the required estimation formula.

[0016] The first estimation formula is given by the following (Formula 1). Note that the "coefficient" in this embodiment may include a constant.

Number

[0017] In (Formula 1), y on the left side is the first estimated value. "100" on the right side means the initial fully charged capacity.

[0018] The first battery variable z1 divides the temperatures that the battery can reach when not in use into multiple temperature ranges and represents one of those temperature ranges. The first battery variable x1 represents the time the battery has been left unattended within the temperature range z1. Hereinafter, the time the battery has been left unattended may simply be referred to as the "idle time". The function y1(x1, z1) on the right side represents the estimated fully charged capacity after degradation due to the idle time. The function y1(x1, z1) includes coefficients specified in advance (i.e., predefined coefficients), and an estimated value can be obtained by substituting the first battery variables x1 and z1. The predefined coefficients will be described later.

[0019] An example of the temperature range and the idle time is shown in Figure 2. In the example of Figure 2, the temperature range is divided into seven (Ts1 - Ts7). Also, the function y1(x1, z1) is shown in Figure 3. The fully charged capacity after degradation decreases according to the idle time. The function y1(x1, z1) is a linear function proportional to the square root of the idle time x1. Its slope Ra takes a negative value. Equation (1a) in Figure 3 corresponds to the graph in Figure 3. The constant Ca and the slope Ra are determined in advance by experiments / simulations / analyses, etc. The fact that y1 is proportional to the square root of the idle time x1 is also a finding obtained from the results of experiments and analyses. The constant Ca and the slope Ra are predefined coefficients. An example of the constant Ca is 100. In the example of Figure 2, the temperatures that the battery can reach are divided into seven. Therefore, the first battery variable x1 (idle time x1) is assigned to each of the seven temperature ranges.

[0020] The estimated value y1 due to the idle time is obtained from Equation (1b) in Figure 3. In Equation (1b), "n" means the number of temperature ranges when the battery is left unattended. In the example of Figure 1, n = 7. Also, the battery characteristic values obtained from experiments are used for the slope Rb in Equation (1b).

[0021] (The idle time x1 in Equation (1b)) i The method of obtaining will be explained. Note that the subscript "i" means the i-th temperature range. That is, "x1" i " means the idle time of the battery in the i-th temperature range. The values of the battery idle time recorded for each temperature range are directly used as "x1".i is used as "x1". i An example of " is shown in FIGS. 4 and 5. FIG. 4 is an example of the battery storage time of vehicle A in each temperature section. For example, the battery storage time x12 of vehicle A when the temperature section is "16 to 20 ° C" (the second temperature section) is "2400". FIG. 5 shows an example of the battery storage time "x1" for each "i". i is shown. The battery storage time x1 in each temperature section of FIG. 4 i is substituted into each stage of FIG. 5. Hereinafter, the "battery storage time" may be simply referred to as the "storage time".

[0022] The function y2(x2, z2) on the right side of formula (1) will be described. The first battery variable z2 divides the temperature that the battery can reach during the running of the electric vehicle into a plurality of temperature sections and represents one of the temperature sections. The temperature section of the first battery variable z2 may be the same as or different from the previous first battery variable z1. The first battery variable x2 represents the amount of electricity that has entered and exited the battery in the temperature section z2. Hereinafter, the amount of electricity that has entered and exited the battery is referred to as the energized electricity amount. The function y2(x2, z2) represents an estimated value of the fully charged capacity after deterioration due to the energized electricity amount during running. The function y2(x2, z2) includes a coefficient specified in advance (that is, a predetermined coefficient), and an estimated value can be obtained by substituting the first battery variables x2 and z2. The predetermined coefficient will be described later.

[0023] An example of temperature classification and the amount of energized electricity is shown in FIG. 6. In this example, the temperature classification of the battery is the same as that in the case of FIG. 2 and is divided into seven levels (Ts1 - Ts7). The function y2(x2, z2) is shown in FIG. 7. The function y2(x2, z2) is a linear function proportional to the amount of energized electricity x2. Its slope Rb takes a negative value. That is, the fully charged capacity after deterioration becomes smaller as the amount of energized electricity increases. Equation (1c) in FIG. 7 corresponds to the graph in FIG. 7. The constant Cb and the slope Rb are determined in advance by experiments / simulations / analyses, etc. The fact that y2 is proportional to the amount of energized electricity x2 is also knowledge obtained by experiments and analyses. The constant Cb and the slope Rb are predetermined coefficients. In the example of FIG. 6, the possible temperatures of the battery are divided into seven levels. Therefore, the amount of energized electricity x2 (the first battery variable x2) is assigned to each of the seven temperature classifications.

[0024] The estimated value y2 caused by the amount of energized electricity is obtained from Equation (1d) in FIG. 7. In Equation (1d), "n" means the number of temperature classifications during driving. In the example of FIG. 6, n = 7. Also, an example of the constant Ca in Equation (1d) is 100. The battery characteristic values obtained by experiments are used for the slope Ra in Equation (1d).

[0025] The energized electricity amount x2 in Equation (1d) i will be explained. Note that the subscript "i" means the i-th temperature classification. That is, "x2 i " means the energized electricity amount in the i-th temperature classification. The energized electricity amount x2 i is obtained in the following two steps.

[0026] (Step 1) The driving time of each temperature classification during driving is frequency - counted. In the upper part of FIG. 8, an example of the driving time of vehicle A in each temperature classification is shown. For example, the driving time of vehicle A when the temperature classification is "16 - 20°C" (the second temperature classification) is "100". In the example of FIG. 8, the total driving time is 1540. The value obtained by dividing the driving time of each temperature classification by the total driving time is the frequency - counted driving time, that is, the driving frequency. In the lower part of FIG. 8, the driving frequencies of each temperature classification are shown. The sum of the driving frequencies of all temperature classifications is 1.0.

[0027] (Step 2) Multiply the total energized electricity of vehicle A by the driving frequency of each temperature range. FIG. 9 shows an example of the energized electricity x2 of each temperature range obtained in Step 2. For example, the energized electricity x25 in the fifth temperature range (i = 5) is x25 = 0.227 (driving frequency in the fifth temperature range) × 8500 (total energized electricity) = 1932.

[0028] (Equation 1) is an equation for obtaining the first estimated value y of the fully charged capacity after deterioration from the estimated value y1 due to the battery storage time and the estimated value y2 due to the energized electricity. (Equation 1) includes fixed coefficients and does not include undetermined coefficients. Substituting the actual data of the battery storage time (the first battery variable x1) and the energized electricity (the first battery variable x2) for each temperature range into (Equation 1), the first estimated value y can be obtained.

[0029] The second estimation formula is given by the following (Equation 2).

[0030] [Number]

[0031] Qdeg on the left side of (Equation 2) also means the estimated value of the fully charged capacity after deterioration. Qdeg in (Equation 2) corresponds to the second estimated value.

[0032] The battery mounted on an electric vehicle deteriorates under the influence of various variables related to the electric vehicle and the battery state. The main factors affecting the battery deterioration are the following four. (1) The storage deterioration amount Dpark representing the deterioration amount caused by the time when the battery is not used (battery storage time). (2) The low-power charging deterioration amount Dlow representing the deterioration amount that occurs when the battery is charged with a low power smaller than a predetermined power threshold. (3) The high-power charging deterioration amount Dhigh representing the deterioration amount that occurs when the battery is charged with a high power larger than a predetermined power threshold. (4) The driving deterioration amount Drun representing the deterioration amount that occurs during the driving of the electric vehicle. Note that the power threshold for distinguishing between low-power charging and high-power charging is set to several tens of kilowatts (for example, 20 kilowatts). The power threshold is predetermined and stored in the controller of the electric vehicle.

[0033] (Equation 1) means that the decrease in the full charge capacity due to deterioration is represented by the sum of the storage deterioration amount Dpark, the low-power charge deterioration amount Dlow, the high-power charge deterioration amount Dhigh, and the driving deterioration amount Drun. The estimation method disclosed in this specification individually obtains the four main factors (Dpark, Dlow, Dhigh, Drun) that affect deterioration, and sums them up to estimate the total deterioration amount. (Equation 2) can accurately estimate the full charge capacity after deterioration because it estimates the deterioration amount for each factor of deterioration. (Equation 2) includes a plurality of battery variables. The battery variables included in (Equation 2) are referred to as the second battery variables and are distinguished from the first battery variables included in (Equation 1).

[0034] The storage deterioration amount Dpark will be specifically described. The storage deterioration amount Dpark can be estimated by the following (Equation 2a).

[0035]

Number

[0036] The meanings of the symbols in (Equation 2a) are as follows. a, b: Undetermined coefficients X i : The battery temperature is divided into n temperature ranges, and represents the second battery variable, which is the time (storage time) that the battery is stored in the i-th temperature range r i : Represents the contribution degree of the storage time to deterioration in the i-th temperature range, which is an undetermined coefficient C: Represents the second battery variable, which is the time from when the electric vehicle is shipped to when it reaches the user Y1: Represents the second battery variable, which is the time (total high charge time) when the remaining battery amount during storage is 80% or more of the initial full charge amount

[0037] Undetermined coefficients a, b, r i are determined from the first estimation formula and the performance data of a plurality of electric vehicles. The determination procedure of the undetermined coefficients will be described later.

[0038] The time C from the shipment of the electric vehicle to the user's receipt is uniquely determined when the electric vehicle reaches the user. That is, C is a fixed constant. The second battery variable, namely, the storage time X for each temperature category i , and the total high-charge time Y1 are regularly measured and accumulated by the controller of the electric vehicle. The accumulated values correspond to the actual performance data of the battery variables.

[0039] Specifically explain the small-power charge degradation amount Dlow. The small-power charge degradation amount Dlow can be estimated by the following (Equation 2b).

Equation

[0040] The meanings of the symbols in (Equation 2b) are as follows. c k : The amount of electricity charged in one small-power charge is divided into m electricity amount categories, and the undetermined coefficient for the k-th electricity amount category Tempa i : The battery temperature is divided into n temperature categories, and the value obtained by dividing the time required for small-power charging at the i-th temperature category by the total small-power charging time (small-power charging time), which is the second battery variable indicating the small-power charging time ra i : The contribution degree to the degradation of battery use in the i-th temperature category, represented by the undetermined coefficient Z k : The amount of electricity charged in one small-power charge is divided into m electricity amount categories, and the number of charging times (small-power charging times) belonging to the k-th electricity amount category, which is the second battery variable

[0041] The undetermined coefficient ra i means the coefficient that converts the battery use per unit time into the degradation amount. "Battery use" means that current flows in and out of the battery. The undetermined coefficient c k is optimized from the actual performance data of the usage status of multiple electric vehicles used by the user. The undetermined coefficient c k , ra i are also determined from the first estimation formula and the actual performance data of multiple electric vehicles. The determination procedure of the undetermined coefficients will be described later.

[0042] The second battery variable Tempa representing the small-power charging time for each temperature range i and the second battery variable Z representing the number of small-power charging times k are periodically measured and accumulated by the controller of the electric vehicle. The accumulated values correspond to the actual performance data of the second battery variables.

[0043] The small-power charging time Tempa for each temperature range i is shown in FIG. 10 as an example. In the example of FIG. 10, the battery temperature is divided into seven temperature ranges. That is, in (Equation 2b), n = 7. The upper part of FIG. 10 shows the small-power charging time in each temperature range. The electric vehicle is equipped with a temperature sensor for measuring the battery temperature, and the controller accumulates and stores each data in the table in the upper part of FIG. 10 from the measured value of the temperature sensor and the time required for small-power charging. The total time required for small-power charging is shown in the rightmost column of the table in the upper part of FIG. 10. In the table in the lower part of FIG. 10, the value obtained by dividing the charging time of each temperature range by the total time is substituted. The numerical values in the table in the lower part of FIG. 10 are an example of the actual performance data of Tempa in (Equation 2b). i is an example of the actual performance data.

[0044] The large-power charging degradation amount Dhigh will be specifically described. The large-power charging degradation amount Dhigh can be estimated by the following (Equation 2c).

Equation

[0045] The meanings of the symbols in (Equation 2c) are as follows. e i : The amount of electricity charged in one large-power charging is divided into p electricity amount ranges, and the undetermined coefficient for the jth electricity amount range Tempb i : The battery temperature is divided into n temperature ranges, and the second battery variable representing the value (large-power charging time) obtained by dividing the time required for large-power charging in the ith temperature range by the total time of large-power charging ra i: Undetermined coefficient representing the contribution to the deterioration of battery usage in the i-th temperature range W j : The amount of electricity charged in one large-power charge is divided into p electricity amount ranges, and the number of charging times (large-power charging times) belonging to the j-th electricity amount range is the second battery variable

[0046] Undetermined coefficient ra representing the contribution i is the same as the undetermined coefficient used in (Equation 2b). Undetermined coefficient e k , ra i are also determined to be optimal values based on the first estimation formula and the performance values of multiple electric vehicles. The procedure for determining the undetermined coefficients will be described later. Battery variable Tempb i is the same as the battery variable Tempa in (Equation 2b) i

[0047] The second battery variable Tempb representing the large-power charging time for each temperature range of the battery i and the second battery variable W representing the number of large-power charging times k are periodically measured and accumulated by the controller of the electric vehicle. The accumulated values correspond to the performance data of the second battery variable.

[0048] The running deterioration amount Drun will be specifically described. The running deterioration amount Drun can be estimated by the following (Equation 2d).

Equation

[0049] The meanings of the symbols in (Equation 2d) are as follows. d: Undetermined coefficient Tempc i : The battery temperature is divided into n temperature ranges, and the value obtained by dividing the time traveled in the i-th temperature range by the total travel time (travel time) is the second battery variable ra i : Undetermined coefficient representing the contribution to the deterioration of battery usage in the i-th temperature range I EV : The second battery variable representing the total amount of electricity flowing in and out of the battery during running

[0050] The second battery variable Tempc representing the driving time for each temperature range of the battery i is the same as the second battery variable Tempa in (Equation 2b). The undetermined coefficient ra i is the same. The undetermined coefficients ra i are the same as the undetermined coefficients used in (Equation 2b). The undetermined coefficients d, ra i are determined to be optimal values from the first estimation formula and the performance data of the usage status of a plurality of electric vehicles used by the user.

[0051] The driving time Tempc for each temperature range i and the total electricity amount I EV are periodically measured and accumulated by the controller of the electric vehicle. The accumulated values correspond to the performance data of the second battery variable.

[0052] The first estimation formulas (Equations 1, 1a - 1d) include the first battery variables x1, x2, z1, z2 and the fixed coefficients Ca, Cb, Ra i , Rb i (where i is an index indicating the temperature range). The fixed coefficients Ca, Ra i define the relational expression between the storage time of the battery and the fully charged capacity after deterioration. The fixed coefficients Cb, Rb i define the relational expression between the charged electricity amount of the battery and the fully charged capacity after deterioration. The fixed coefficients of the first estimation formula are specified in advance by experiments / simulations / theoretical analyses, etc.

[0053] The second estimation formulas (2 - 2 - 4) include the second battery variables X i , C, Y1, Tempa i , Z k , Tempb i , W j , Tempc i , I EV . Also, the second estimation formulas (2 - 2 - 4) include the undetermined coefficients a, b, r i , c k , ra i , e i , ra i , d. Hereinafter, the first battery variable and the second battery variable are collectively referred to as "battery variables".

[0054] (Second Step) Collect actual data of battery variables from L electric vehicles (Figure 1, Step S2). The number L is a number much larger than the number of undetermined coefficients. The electric vehicles targeted by the estimation formula creation method are equipped with communication devices. Also, the electric vehicles periodically store measurement values corresponding to the battery variables. The measurement values stored by the electric vehicles correspond to the actual data of the battery variables. The electric vehicles periodically send the actual data of the battery variables to the management center. The computer of the management center collects the actual data of the battery variables of L electric vehicles.

[0055] (Third Step) Substitute the K actual data regarding the first battery variable among the L actual data into the first estimation formula to obtain K first estimated values of the fully charged capacity after battery degradation (Step S3).

[0056] (Fourth Step) Substitute the K actual data regarding the second battery variable among the L actual data and the K first estimated values into the second estimation formula, and identify the undetermined coefficients by multiple regression analysis from the obtained K second estimation formulas (Figure 1, Step S4). The actual data of the first battery variable and the actual data of the second battery variable in the actual data of one electric vehicle both correspond to the fully charged capacity after degradation of that electric vehicle. The first estimated value obtained by substituting the actual data of the first battery variable into the first estimation formula should be equal to the left side (i.e., the second estimated value) of the second estimation formula when the actual data of the second battery variable is input. That is, the first estimated value can be substituted into the left side of the second estimation formula. At this time, the K second estimation formulas obtained by substituting the actual data into the second battery variable on the right side of the second estimation formula can be regarded as a multiple regression formula with the first estimated value on the left side as the target variable and the undetermined coefficients as the explanatory variables. Therefore, the undetermined coefficients can be identified from the K second estimation formulas by multiple regression analysis.

[0057] (Step 5) Substitute the (L - K) pieces of performance data regarding the second battery variable in the actual performance data into the second estimation formula including the identified undetermined coefficients to obtain (L - K) second estimated values, and substitute the (L - K) pieces of performance data regarding the first battery variable into the first estimation formula to obtain new first estimated values (FIG. 1, Step S5).

[0058] (Step 6) Correct the identified undetermined coefficients so that the correlation between the (L - K) first estimated values and the second estimated values obtained in Step 5 becomes stronger. The (L - K) pieces of performance data are not used for identifying the undetermined coefficients. The computer corrects the coefficients using the (L - K) pieces of performance data and their corresponding first estimated values. The computer substitutes the (L - K) pieces of performance data regarding the second battery variable into (Equation 2) to obtain second estimated values. The value identified in Step S5 is used for the undetermined coefficients of (Equation 2) at this time. Also, the computer substitutes the (L - K) pieces of performance data regarding the first battery variable into (Equation 1) to newly obtain first estimated values.

[0059] FIG. 11 shows an example of the correlation between the first estimated value and the second estimated value. FIG. 11 is a graph plotting the pairs of the first estimated value y and the second estimated value Qdeg calculated using the (L - K) pieces of performance data. Group A is the result of the pairs of estimated values when using the coefficients before correction. It is desirable that the first estimated value and the second estimated value be equal. If the first estimated value and the second estimated value are equal, the pair of the first estimated value and the second estimated value is located on a 45-degree straight line. Before correction (Group A), the identified undetermined coefficients are not accurate, and the pair of the first corrected value and the second corrected value is away from the 45-degree straight line.

[0060] In Step 6, correct the determined undetermined coefficients so that the pair of the first corrected value and the second corrected value is distributed along the 45-degree straight line. Group B in FIG. 11 represents the distribution of the pairs of the first estimated value and the second estimated value when using the coefficients after correction. By optimizing the identified undetermined coefficients through correction, the accuracy of (Equation 2) is improved.

[0061] (Step 7) Use the first estimation formula containing the determined and corrected undetermined coefficients and the first battery variable as the estimation formula for the fully charged capacity after battery degradation. As described above, by optimizing the coefficients (the determined undetermined coefficients) using (L - K) pieces of performance data and (Equation 1), a highly accurate estimation formula for the fully charged capacity after degradation can be obtained.

[0062] Next, an example of optimizing the undetermined coefficients is shown. The first estimation formula (Equation 1) and the second estimation formula (Equation 2) are as described above (Step 1).

[0063] (Step 2) Collect the performance data of the first battery variable and the second battery variable from L electric vehicles. The first battery variable is x1, x2, z1, z2 in (Equation 1). For x1, the battery storage time is used. For z1, each temperature range obtained by dividing the temperature range of the battery when it is stored into a plurality of temperature categories is used. For x2, the total charged electricity amount is used. For z2, each temperature range obtained by dividing the temperature range of the electric vehicle when it is running into a plurality of temperature categories is used. The second battery variable is X in (Equation 2a), (Equation 2b), (Equation 2c), (Equation 2d) i , C, Y1, Tempa i , Z k , Tempb i , W j , Tempc i , I EV . The meaning of each symbol is as described above. The first battery variable and the second battery variable are always measured and accumulated in an actually running electric vehicle.

[0064] (Step 3a) Substitute the L first battery variables included in the L pieces of performance data into the first estimation formula (Equation 1) to obtain L first estimated values y. For convenience of explanation, hereinafter, the L first estimated values y are referred to as L target variables y.

[0065] (Step 3b) Divide the L target variables y into K pieces of learning data and (L - K) pieces of test data. The selection of the learning data and the test data may be random. The ratio of K to (L - K) is preferably 8:2.

[0066] The undetermined coefficients a, b, r in (Formula 2a), (Formula 2b), (Formula 2c), and (Formula 2d) i , c k , ra i , e j , ra i , d are assigned some initial values.

[0067] (Step 4) Substitute the initial values of the undetermined coefficients and the K battery variables into the second estimation formula (Formula 2) to obtain K second estimated values Qdeg. The undetermined coefficients a, b, r are adjusted such that the absolute value of the difference (|y - Qdeg|) between each of the K learning data y and each of the K estimated values Qdeg is minimized i , c k , ra i , e j , ra i , d. A genetic algorithm is suitable for the optimization algorithm.

[0068] (Step 5) Use the (L - K) test data y to verify the accuracy of the second estimation formula (Formula 2) (the accuracy of the undetermined coefficients determined by optimization). Specifically, perform the following process. Substitute the (L - K) second battery variables into the second estimation formula after optimizing the undetermined coefficients to obtain (L - K) second estimated values Qdeg. Plot the pairs (y, Qdeg) of the (L - K) test data y and the corresponding second estimated values Qdeg on a graph. An example of the plot is shown in FIG. 12. Calculate the average error and the maximum error of the (L - K) pairs (y, Qdeg).

[0069] (Step 6) Repeat the process from Step 3b to Step 5 ten times. An example of the results (average error and maximum error) when the process is repeated ten times is shown in FIG. 13.

[0070] (Step 7) As the accuracy of the second estimation formula, adopt the average value of the average error and the maximum error when the process from Step 3b to Step 5 is repeated ten times.

[0071] Points to note regarding the technology described in the embodiments are described. The structure of the formulas introduced in the embodiments is based on the knowledge obtained from experiments / simulations / analyses, etc.

[0072] The method for creating the estimation formula disclosed in this specification may be performed by a computer or by a person.

[0073] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Also, the technology illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of those objectives itself has technical usefulness.

Claims

【Claim 1】 A method for creating an estimation formula for the fully charged capacity after deterioration of a battery of an electric vehicle, including a predetermined coefficient and a first battery variable related to the state of the battery, a first estimation formula for obtaining a first estimated value of the fully charged capacity after deterioration of the battery, an undetermined coefficient, and a second battery variable related to the state of the battery, and a first step of preparing a second estimation formula for obtaining a second estimated value of the fully charged capacity after deterioration of the battery; A second step of collecting performance data of the first battery variable and the second battery variable from L electric vehicles; A third step of substituting K pieces of performance data related to the first battery variable in the L pieces of performance data into the first estimation formula to obtain K first estimated values; A fourth step of identifying an undetermined coefficient by multiple regression analysis from the second estimation formula substituting K pieces of performance data related to the second battery variable in the L pieces of performance data and the K first estimated values; Substitute (L - K) pieces of performance data related to the second battery variable in the performance data into the second estimation formula including the identified undetermined coefficient to obtain (L - K) second estimated values, and substitute (L - K) pieces of performance data related to the first battery variable into the first estimation formula to obtain new first estimated values. A fifth step; A sixth step of correcting the identified undetermined coefficient so that the correlation between the (L - K) first estimated values and the second estimated values obtained in the fifth step becomes strong; A seventh step of using the second estimation formula including the identified and corrected undetermined coefficient and the second battery variable as an estimation formula for the fully charged capacity after deterioration of the battery; Comprising, The first estimation formula is represented by the following (Equation 1), 【Number 1】 Here, y: The first estimated value of the fully charged capacity after deterioration of the battery y1(x1, z1): A function including a predetermined coefficient and taking the first battery variables x1 and z1 as arguments z1: A first battery variable that divides the temperature that the battery can take when not in use into a plurality of temperature ranges and indicates one of the temperature ranges x1: A first battery variable representing the time the battery was left in the temperature range z1 y2(x2, z2): A function including a predetermined coefficient and taking the first battery variables x2 and z2 as arguments z2: A first battery variable that divides the temperature that the battery can take during the running of the electric vehicle into a plurality of temperature ranges and indicates one of the temperature ranges x2: A first battery variable representing the amount of electricity that entered and exited the battery in the temperature range z2 That is, The second estimation formula is represented by the following (Equation 2), 【Number 2】 Here, Qdeg: The second estimated value of the fully charged capacity after deterioration of the battery Dpark: The amount of deterioration due to the storage time of the battery, i.e., the storage deterioration amount Dlow: The amount of deterioration that occurs when the battery is charged at a low power smaller than a predetermined power threshold, i.e., the low-power charging deterioration amount Dhigh: The amount of deterioration that occurs when the battery is charged at a high power greater than a predetermined power threshold, i.e., the high-power charging deterioration amount Drun: The amount of deterioration that occurs during the running of the electric vehicle, i.e., the running deterioration amount and The storage deterioration amount Dpark, the low-power charging deterioration amount Dlow, the high-power charging deterioration amount Dhigh, and the running deterioration amount Drun are respectively 【Number 3】 Here a, b: Undetermined coefficients X ｉ : A second battery variable that divides the battery temperature into n temperature ranges and represents the time the battery was left in the i-th temperature range r ｉ : An undetermined coefficient representing the contribution to deterioration of the standing time in the i-th temperature range C: The second battery variable representing the time from when the electric vehicle is shipped to when it reaches the customer Y1: The second battery variable representing the time during which the remaining battery capacity is 80% or more of the initial full charge capacity during storage 【Number 4】 Here c ｋ : The amount of electricity charged by a single low-power charge is divided into m electricity amount categories, and the undetermined coefficient for the k-th electricity amount category Tempa ｉ : A second battery variable representing a value obtained by dividing the battery temperature into n temperature ranges and dividing the time required for low-power charging in the i-th temperature range by the total time of low-power charging ra ｉ : An undetermined coefficient representing the contribution to the deterioration of battery use in the i-th temperature range Z ｋ : The amount of electricity charged in one small-power charge is divided into m electricity amount categories, and a second battery variable representing the number of charging times belonging to the k-th electricity amount category 【Number 5】 Here e ｊ : The amount of electricity charged in one large-power charging is divided into p electricity amount sections, and the undetermined coefficient for the j-th electricity amount section Tempb ｉ : A second battery variable that divides the battery temperature into n temperature ranges and represents the value obtained by dividing the time required for high-power charging in the i-th temperature range by the total time of high-power charging ra ｉ : An undetermined coefficient representing the contribution to the deterioration of battery use in the i-th temperature range W ｊ : The amount of electricity charged in one large-power charging is divided into p electricity amount sections, and a second battery variable representing the number of charging times belonging to the j-th electricity amount section [Number 6] Here d: Undetermined coefficient Tempc ｉ : A second battery variable representing a value obtained by dividing the time traveled in the i-th temperature range by the total travel time, where the battery temperature is divided into n temperature ranges ra ｉ : An undetermined coefficient representing the contribution to the deterioration of battery use in the i-th temperature range I ＥＶ : A second battery variable representing the total amount of electricity that has entered and exited the battery during travel is A method for creating an estimation formula for the full charge capacity of the battery after deterioration

Images