Method, device, program, and storage medium for estimating internal temperature of secondary battery

Abstract

This invention provides a method for accurately estimating the internal temperature of a secondary battery while considering the state of charge (SOC) and charge / discharge state. The method is a method (80) for estimating the internal temperature (T) of a vehicle secondary battery (1), comprising a repeatedly executed change determination process (50) and a repeatedly executed internal temperature estimation process (60, 60'). The change determination process includes: (54) a step of determining a first change (21) in the internal resistance (R) relative to the charge rate (SOC) based on the voltage (V) and charge / discharge current (I) of the secondary battery when the vehicle is stationary or at the start of driving; and (22) a step of determining a second change (22) in the internal resistance relative to the charge rate based on the voltage and charge / discharge current during vehicle operation. Step (57) of the internal temperature estimation process includes: measuring the external temperature (To) of the secondary battery (62); measuring the charge and discharge current (63); calculating the charge rate (64); determining whether the secondary battery is discharging (66); selecting a first change when discharging (67); selecting a second change when not discharging (68); calculating the internal resistance based on the selected change and the calculated charge rate (69); and estimating the internal temperature based on the external temperature, charge and discharge current, and internal resistance (70).

Description

Technical Field

[0001] This invention relates to a method, apparatus, program, and storage medium storing the program for estimating the internal temperature of a secondary battery, and particularly to a method for estimating the internal temperature of a secondary battery mounted in a vehicle. Background Technology

[0002] The optimal charging rate of a secondary battery varies depending on its internal temperature. In addition, when the internal temperature exceeds a certain value, its performance will deteriorate significantly. Because the characteristics change greatly depending on the internal temperature, internal temperature management is very important.

[0003] Since it is difficult to install sensors that directly measure the internal temperature on a vehicle, a method for estimating the internal temperature from the internal resistance of a secondary battery, taking into account the temperature rise caused by Joule heating, is proposed, as described in Patent Document 1. In Patent Document 1, the internal resistance DCIRnml for a reference time is determined based on the correlation between the battery temperature measured during discharge and the internal resistance. This internal resistance DCIR is then multiplied by a correction factor F that takes into account the elapsed time since the start of discharge, and the Joule heating HGjoule is calculated from the internal resistance DCIR.

[0004] (Existing technical documents)

[0005] (Patent Documents)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-157348. Summary of the Invention

[0007] (The problem that the invention aims to solve)

[0008] However, the internal resistance changes not only with the time elapsed since the start of discharge but also significantly with the charge rate of the secondary battery. Furthermore, the relationship between the charge rate and the internal resistance differs depending on whether the secondary battery is charging or discharging. Particularly in the high charge rate region (near full charge) and the low charge rate region (near full discharge), the internal resistance relative to the charge rate differs greatly during charging and discharging. Therefore, if the internal temperature (liquid temperature) is estimated from the calculated internal resistance without considering the charge rate and the charge / discharge state of the secondary battery, a decrease in accuracy becomes problematic.

[0009] Therefore, there is a need for a method, apparatus, program, and storage medium storing the program that can accurately estimate the internal temperature of a secondary battery, taking into account the charge rate and state of charge / discharge.

[0010] (Solutions)

[0011] The above-mentioned problem can be solved by the following method, etc.: a method (80) for estimating the internal temperature (T) of a secondary battery (1) for a vehicle, the method comprising a repeatedly executed change determination process (50) and a repeatedly executed internal temperature estimation process (60, 60'), the change determination process comprising: a step (54) of determining a first change (21) of the internal resistance (R) relative to the charge rate (SOC) based on the voltage (V) and the charge / discharge current (I) of the secondary battery when the vehicle is stopped or when driving begins; and a second change of the internal resistance relative to the charge rate based on the voltage and charge / discharge current when the vehicle is in motion. (22) Step (57), the internal temperature estimation process includes: step (62) measuring the external temperature (To) of the secondary battery; step (63) measuring the charge and discharge current; step (64) calculating the charge rate; step (66) determining whether the secondary battery is discharging; step (67) selecting the first change when the secondary battery is discharging; step (68) selecting the second change when the secondary battery is not discharging; step (69) calculating the internal resistance based on the selected change and the calculated charge rate; and step (70) estimating the internal temperature based on the external temperature, charge and discharge current and internal resistance.

[0012] That is, two changes are prepared for the secondary battery: the change in internal resistance relative to the charging rate during discharge (first change) and the change in internal resistance relative to the charging rate during charging (second change). The first change is determined when the vehicle, which is mainly discharging, is stationary or when driving begins, and the second change is determined when the vehicle, which is mainly charging, is in motion. Then, based on the changes selected according to the charging and discharging state of the secondary battery, the internal resistance is calculated with high accuracy, and its internal temperature is estimated by using this internal resistance, thereby achieving a high-accuracy estimation of the internal temperature.

[0013] It should be noted that in this application, "in a stopped state" refers to a state in which the secondary battery is not charging or discharging, such as when the ignition device is off. Therefore, in the case of vehicles with internal combustion engines (such as hybrid vehicles), the idling state (the state in which the internal combustion engine is running but the vehicle is not running) is not included in "in a stopped state".

[0014] The method (80) further includes a step (65) to determine whether the calculated charge rate (SOC) is within a specified range. Preferably, in the step (69) of calculating the internal resistance (R), when the calculated charge rate (SOC) is within a specified range, the internal resistance (R) of the secondary battery (1) is calculated based on the change selected in the previous repetition and the calculated charge rate (SOC).

[0015] When the charging rate is in the middle region (the specified range), the difference in the change of internal resistance relative to the charging rate due to different charging and discharging states is small. Therefore, the internal resistance (R) can be obtained by directly using the change selected in the last repetition, which simplifies the estimation process without compromising the estimation accuracy.

[0016] In addition, the preferred method includes a step (65) to determine whether the calculated charge rate (SOC) is within a specified range, and a step (73) to select the first change (21) when the calculated charge rate (SOC) is within a specified range, regardless of whether the secondary battery (1) is discharging.

[0017] When the charging rate is in the middle range (the specified range), the difference in internal resistance relative to the charging rate due to different charging and discharging states is small. Therefore, by always selecting the first change regardless of whether the secondary battery is discharging, it is not necessary to determine whether the secondary battery is discharging during selection, and the estimation process can be simplified without compromising the estimation accuracy.

[0018] Furthermore, the method preferably includes a step (72) of correcting the calculated internal resistance (R) based on the internal temperature (T) estimated during the previous repetition. By using the internal resistance (R) corrected based on the internal temperature (T) estimated during the previous repetition to calculate the new internal temperature (T), discontinuities in the estimation results can be prevented, and rapid changes in the estimated internal temperature can be avoided.

[0019] Furthermore, the aforementioned problems can also be solved by the apparatus, program, and storage medium storing the program that implement the above method. Attached Figure Description

[0020] Figure 1 This is a flowchart of the internal temperature estimation method and procedure involved in the present invention.

[0021] Figure 2 A flowchart for determining the process of change.

[0022] Figure 3A This is a flowchart of the process for estimating the internal temperature.

[0023] Figure 3B This is a flowchart of the process for estimating the internal temperature.

[0024] Figure 4 This is a schematic diagram of the internal temperature estimation device involved in the present invention.

[0025] Figure 5 This represents the change in internal resistance relative to the charge rate during charging and discharging.

[0026] Figure 6 This describes the effects of the present invention. Detailed Implementation

[0027] A schematic diagram of the internal temperature estimation device 10, which is an embodiment of the present invention, is shown in [illustration]. Figure 4 The internal temperature estimation device 10 is connected to the secondary battery 1 and the charging circuit 2. The secondary battery 1 is, for example, a lead-acid battery used in vehicles. The charging circuit 2 is a power supply circuit connected to the secondary battery 1 and providing charging current. In addition, the secondary battery 1 is connected to a load 3, such as an on-board electrical device like a motor, control circuit, or lighting device. The secondary battery 1, charging circuit 2, load 3, and internal temperature estimation device 10 are mounted on a vehicle (not shown).

[0028] The internal temperature estimation device 10 includes a voltage sensor 11, a current sensor 12, a temperature sensor 15, a memory 13, and a controller 14. The voltage sensor 11, current sensor 12, temperature sensor 15, and memory 13 are electrically connected to the controller 14 and can communicate with each other through data and signals.

[0029] Voltage sensor 11 is connected between the terminals of secondary battery 1, periodically and / or upon request from controller 14 to measure the voltage between the terminals, and sends the measured voltage V to controller 14. Current sensor 12 is located between secondary battery 1 and charging circuit 2. Secondary battery 1 and current sensor 12 are connected in parallel with load 3, periodically and / or upon request from controller 14 to measure the charging and discharging current I flowing through secondary battery 1, i.e., the charging current flowing into secondary battery 1 or the discharging current flowing out of secondary battery 1, and sends the measured charging and discharging current I to controller 14. Furthermore, temperature sensor 15 is located on or near secondary battery 1, periodically and / or upon request from controller 14 to measure the external temperature To of secondary battery 1, and sends the measured temperature To to controller 14.

[0030] The controller 14 includes a processor that acquires measurement signals and data from the voltage sensor 11, current sensor 12, and temperature sensor 15, and performs / controls processing for estimating the internal temperature T of the secondary battery 1. Furthermore, the controller 14 can communicate with the charging circuit 2 and can control the flow of charging and discharging current from the charging circuit 2 to the secondary battery 1 in a predetermined pattern. Moreover, the controller 14 can also be configured to control the timing of measurements performed by the voltage sensor 11, current sensor 12, and temperature sensor 15.

[0031] The memory 13 is composed of computer-readable storage media such as semiconductor memory (RAM, SSD, flash memory, etc.) or magnetic memory (HDD, etc.). The memory 13 stores the program executed by the processor of the controller 14, various parameters used during processing according to the program, two changes 21 and 22 of the internal resistance R relative to the state of charge (SOC), measured values ​​obtained by the controller 14 from the voltage sensor 11, current sensor 12, and temperature sensor 15, and stored estimated internal resistance R, internal temperature T, etc. Figure 5 An example of variations 21 and 22 is shown in the figure.

[0032] Figure 5 The graph shows the state of charge (SOC) of the secondary battery 1 on the horizontal axis and the internal resistance (R) of the secondary battery 1 on the vertical axis. It illustrates a first change (21) in the internal resistance (R) relative to the SOC when the vehicle is stationary or starting to move, primarily in a discharging state, and a second change (22) in the internal resistance (R) relative to the SOC when the vehicle is moving, primarily in a charging state. Changes 21 and 22 are stored in memory 13 in the form of tables or approximations. The controller 14 can calculate changes 21 and 22 by generating / updating the coefficients of the stored tables or approximations, and reads selected changes 21 and 22 for estimating the internal resistance (R) or internal temperature (T) of the secondary battery 1.

[0033] Next, refer to Figure 1 Flowcharts 50, 60, 60', and 80 of section ~3 illustrate a method 80 for estimating the internal temperature of a secondary battery as an embodiment of the present invention. The method 80 for estimating the internal temperature of a secondary battery consists of the following two processing steps: Figure 2 The change determination process shown in flowchart 50, and Figure 3A , Figure 3B The flowcharts 60 and 60' show the internal temperature estimation process. The change determination process 50 is a process for determining the first change 21 when the vehicle is stationary or at the start of driving (i.e., when the secondary battery 1 is mainly in a discharging state), and the second change 22 when the vehicle is in motion (i.e., when the secondary battery 1 is mainly in a charging state). Furthermore, the internal temperature estimation processes 60 and 60' are processes for estimating the internal temperature T of the secondary battery 1 using the calculated changes 21 and 22.

[0034] Both processes 50 and 60 (or 50 and 60') are executed periodically or non-periodically as required. The timing of the execution of both processes 50 and 60 (or 50 and 60') can be determined as follows: Figure 1 (a) can be executed independently as described above. Figure 1(b) Processes 50 and 60 (or 50 and 60') are executed sequentially and repeatedly. The memory 13 of the internal temperature estimation device 10 stores a program for the processor of the controller 14 to execute the functions shown in flowcharts 50, 60, 60', and 80.

[0035] Next, refer to Figure 2 Flowchart 50 explains the change determination process 50. First, the controller 14 determines whether the vehicle is stopped or has started driving (step 51). When the vehicle is stopped or has started driving, it is assumed that the charging and discharging current of the secondary battery 1 is small. Therefore, the controller 14 controls the charging circuit 2 to discharge current flowing from the secondary battery 1 in a predetermined discharge mode. The discharge mode is, for example, pulse discharge. The voltage V between the terminals of the secondary battery 1 is measured by the voltage sensor 11, and the discharge current I flowing from the secondary battery 1 is measured by the current sensor 12. In addition, the internal resistance R (R=V / I) can be calculated by dividing the measured voltage V by the current I (step 52). Since this is performed when the vehicle is stopped or has started driving, stable voltage and current measurement results can be obtained, and the internal resistance R can be calculated with high accuracy.

[0036] Next, the controller 14 calculates the charge rate SOC of the secondary battery 1 (step 53). Various methods exist for estimating the charge rate. For example, the charging and discharging current I of the secondary battery 1 after it is fully charged (SOC=100%) can be repeatedly measured using the current sensor 12, and accumulated over measurement time intervals Δt to calculate the change in charge ΔQ after full charge (ΔQ = time integral of (I×Δt)). The change in charge rate ΔSOC is then calculated by dividing the change in ΔQ by the full charge capacity SOH of the secondary battery 1 (ΔSOC = ΔQ / SOH / 100). The current SOC (SOC = 100 - ΔSOC) can then be estimated from the difference at the full charge state (SOC=100%). The initial state of the time integral is not limited to when the battery is fully charged; the charge rate SOCo at any time can also be calculated, and the change in charge ΔQ from that time can be estimated to estimate the current charge rate SOC (SOC = SOCo - ΔSOC).

[0037] Next, based on the estimated charge rate SOC and the calculated internal resistance R, a first change 21 of the internal resistance (R) relative to the charge rate (SOC) of the secondary battery (1) is calculated (step 54). Specifically, for example, the estimated charge rate SOC and the calculated internal resistance R are added to or updated in the table of the first change 21 stored in the memory 13. Alternatively, the approximation representing the change of the internal resistance R relative to the charge rate SOC can be updated based on the estimated current charge rate SOC and the calculated internal resistance R. If the data of the first change 21 stored in the memory 13 is insufficient and the correlation between the charge rate (SOC) and the internal resistance (R) is not fully obtained, the change determination process 50 can be repeated to collect the relationship between the charge rate SOC and the internal resistance R and generate the first change 21. In this invention, "calculating the change" includes either regenerating the change of the internal resistance R relative to the charge rate SOC (table, approximation, etc.) or updating the existing change.

[0038] On the other hand, in step 51, if it is determined that the vehicle is not stopped or has started driving, since the vehicle is in motion, a large charging / discharging current is assumed. Therefore, the voltage V between the terminals of the secondary battery 1 is measured using voltage sensor 11, and the discharge current I flowing from the secondary battery 1 is measured using current sensor 12 (step 55). More specifically, controller 14 requests voltage sensor 11 to measure the voltage between the terminals of the secondary battery 1 and obtains the voltage V measured by voltage sensor 11, or obtains the latest voltage V periodically measured by voltage sensor 11 from memory 13. In addition, controller 14 requests current sensor 12 to measure the charging / discharging current I of the secondary battery 1 and obtains the magnitude of current I measured by current sensor 12, or obtains the latest magnitude of current I periodically measured by current sensor 12 from memory 13. By dividing the measured voltage V by the current I, the internal resistance R (R=V / I) can be calculated (step 55).

[0039] Next, the controller 14 calculates the state of charge (SOC) of the secondary battery 1 (step 56). An example of a specific method for estimating the SOC has been described in the explanation of step 53 and is omitted here. The estimation in step 56 can be performed using the same method as in step 53, or it can be performed using a different method.

[0040] Next, based on the estimated current charge rate SOC and the calculated internal resistance R, a second change 22 of the internal resistance (R) relative to the charge rate (SOC) of the secondary battery (1) is calculated (step 57). Specifically, for example, the estimated charge rate SOC and the calculated internal resistance R are added to or updated in the table of second changes 22 stored in memory 13. Alternatively, the approximate formula representing the change of internal resistance R relative to the charge rate SOC can be updated based on the estimated current charge rate SOC and the calculated internal resistance R. If the data for second changes 22 stored in memory 13 is insufficient and the correlation between the charge rate (SOC) and the internal resistance (R) is not fully obtained, the change determination process 50 can be repeated to collect the relationship between the charge rate SOC and the internal resistance R and generate the second change 22. In addition, since steps 55 to 57 are performed while the vehicle is in motion, there is a possibility that the voltage of the secondary battery 1 is unstable, and the deviation of the measurement results may increase. Therefore, even in the region where the correlation between the charge rate SOC and the internal resistance R has been obtained, a highly accurate change 22 can be obtained by repeatedly acquiring data and calculating the change.

[0041] Through the change determination process 50 described above, the first change 21 of the internal resistance R relative to the charge rate SOC of the secondary battery 1 when the vehicle is stopped or when driving begins, and the second change 22 of the internal resistance R relative to the charge rate SOC of the secondary battery 1 when the vehicle is in motion can be calculated.

[0042] Next, regarding the reference Figure 3A , Figure 3B Flowcharts 60 and 60' illustrate the internal temperature estimation process 60 and 60'. The only difference between internal temperature estimation process 60 and internal temperature estimation process 60' is the presence or absence of step 73; therefore, the following is based on... Figure 3A The flowchart 60 is explained, and appropriate connections are made with it. Figure 3B The different flowcharts 60' will be explained.

[0043] When the vehicle is stationary or at the start of driving, the charging and discharging current is small, resulting in a small temperature rise due to Joule heating. Therefore, the estimation of the internal temperature T varies depending on whether the vehicle is in motion. Here, the controller 14 first determines whether the vehicle's ignition system is on to determine whether the vehicle is in motion (step 61).

[0044] When the ignition device is not in the on state, the controller 14 measures the external temperature To of the secondary battery 1 via the temperature sensor 15 (step 62). More specifically, the controller 14 requests the secondary battery 1 or the temperature sensor 15 located nearby to measure the external temperature of the secondary battery 1, obtains the external temperature To measured by the temperature sensor 15, or obtains the latest external temperature To periodically measured by the temperature sensor 15 from the memory 13. Then, the internal temperature T is estimated based on the measured external temperature To (step 71).

[0045] Repeat the above process until the ignition device is turned on, so the final external temperature To becomes the external temperature To at the moment the vehicle starts driving.

[0046] On the other hand, when the ignition device is in the on state, the controller 14 measures the charging and discharging current I of the secondary battery 1 through the current sensor 12 (step 63). Specifically, the controller 14 requests the current sensor 12 to measure the charging and discharging current I of the secondary battery 1, and obtains the magnitude of the current I measured by the current sensor 12, or obtains the latest magnitude of the current I measured periodically by the current sensor 12 from the memory 13.

[0047] Next, the controller 14 calculates the current charge rate (SOC) of the secondary battery 1 based on the measured charge / discharge current I (step 64). An example of a specific method for estimating the charge rate (SOC) was described in the explanation of step 53 and is omitted here. The estimation in step 64 can be performed using the same method as the estimations in steps 53 and 56, or it can be performed using a different method.

[0048] Next, controller 14 determines whether the calculated SOC (State of Charge) is within the specified range (step 65). Figure 5 It is known that the internal resistance R differs significantly from the state of charge (SOC) in the high charge rate region (near full charge) and the low charge rate region (near full discharge), with the difference decreasing in the median region between the two. Therefore, the median region is defined as the area between the upper threshold (e.g., 80%) and the lower threshold (e.g., 20%) of the charge rate, and it is determined whether the estimated SOC falls within the specified range between the upper and lower thresholds, i.e., whether the SOC is within the median region.

[0049] When the State of Charge (SOC) is outside the specified range—that is, when the SOC is in the region close to full charge (higher than the upper threshold) or close to full discharge (lower than the lower threshold)—the internal resistance R relative to the SOC varies greatly depending on the charging and discharging state. Therefore, it is necessary to estimate based on the changes in the charging and discharging state. Thus, the controller 14 first determines whether the secondary battery 1 is discharging (step 66). If it is discharging, the controller 14 selects the first change 21 (step 67). On the other hand, if it is not discharging (i.e., charging), the controller 14 selects the second change 22 (step 68).

[0050] Next, controller 14 calculates the internal resistance R of secondary battery 1 based on the selected change and the calculated charge rate SOC (step 69). Specifically, the internal resistance R corresponding to the calculated charge rate SOC is calculated with reference to the selected change. In this way, by calculating the internal resistance R without using the measured inter-terminal voltage of secondary battery 1 during driving, which has a large deviation, a highly accurate internal resistance R can be obtained. The calculated internal resistance R is corrected based on the internal temperature T estimated during the last repetition (step 72). When the vehicle transitions from a stationary state to a driving state, the internal resistance R calculated in step 69 is corrected based on the internal temperature T estimated in step 71 during the stationary state. Furthermore, the calculated internal resistance R can also be corrected based on the change in external temperature or the change in charge rate SOC measured by temperature sensor 15. The internal resistance calculated in step 69 and the internal resistance corrected in step 72 are stored in memory 13 and can be used for estimating the internal temperature T, controlling the vehicle, and controlling secondary battery 1.

[0051] On the other hand, if the calculated State of Charge (SOC) is within a specified range, i.e., the estimated SOC is in the midpoint between the upper and lower thresholds, the internal resistance R relative to the SOC varies little depending on the charging and discharging state, so no new selection is made. Therefore, the change selected in the previous repetition of the internal temperature estimation process 60 remains unchanged, and the internal resistance R is calculated based on the change selected in the previous repetition and the SOC calculated in step 64. Thus, steps 66-68 can be omitted, simplifying the process without compromising estimation accuracy and reducing the processing burden on the processor of the controller 14.

[0052] Finally, based on the external temperature To, the measured charge / discharge current I, and the calculated internal resistance R, the internal temperature T of the secondary battery 1 is estimated (step 70). Specifically, the change in internal temperature (ΔT) caused by Joule heating can be calculated using the following formula.

[0053] ΔT=J×I2×t×R / Ro

[0054] Here, t is time, Ro is the reference resistance, and J is a coefficient in the reference resistance Ro, which is pre-calculated for each battery size based on measured values ​​of charge / discharge current and battery temperature changes.

[0055] Once the external temperature To at the moment the vehicle begins driving is determined, ΔTs is reset to 0. Then, during each execution of step 70, ΔT is calculated and accumulated based on the elapsed time t since the last execution. This allows us to determine the change in internal temperature ΔTs after the vehicle begins driving. The internal temperature T at the start of driving can be considered equal to the external temperature To; therefore, the current internal temperature T can be calculated using the following formula.

[0056] T = To + Ts

[0057] The estimated internal temperature T is stored in memory 13 and can be used to control the vehicle and secondary battery 1 as needed.

[0058] In addition, Figure 3A In the internal temperature estimation process 60 shown, no new changes are made if the calculated SOC is within the specified range. However, alternatively, such as... Figure 3B As shown in the internal temperature estimation process 60', when the calculated charge rate SOC is within the specified range, the controller 14 can select the first change 21 regardless of whether the secondary battery 1 is discharging (step 73). Therefore, when the charge rate is in the middle range (specified range), it is not necessary to determine whether the secondary battery is discharging when selecting the change, which simplifies the process and reduces the processing burden on the processor of the controller 14.

[0059] Through the internal temperature estimation process 60 and 60' described above, the internal temperature T can be determined using the change 21 of the internal resistance R relative to the charge rate SOC when the vehicle is stationary or starting to move, and the change 22 of the internal resistance R relative to the charge rate SOC while the vehicle is moving. The internal resistance R is determined based on the change selected according to the charge / discharge state of the secondary battery 1, and the internal temperature T is estimated using the internal resistance R, thus enabling a high-precision estimation of the internal temperature T. Furthermore, the internal resistance R can be estimated based on the charge / discharge current I of the secondary battery 1 without using the measured inter-terminal voltage V of the secondary battery 1 during vehicle movement, which has a large measurement deviation; therefore, the internal temperature T can be estimated with high precision. Moreover, when the charge rate SOC is in the middle region (a specified range), the change selected in the previous repetition can be directly used, or the first change 21 can be selected regardless of whether the secondary battery 1 is discharging, to determine the internal resistance R, and the internal temperature T can be estimated based on this internal resistance R. This simplifies the estimation process and reduces the processing burden on the processor without compromising the accuracy of the internal temperature T estimation. Furthermore, the internal resistance R is corrected based on the internal temperature T estimated during the previous repetition, and a new internal temperature (T) is calculated based on this internal resistance R. This prevents the estimated result from being discontinuous with the previous one and avoids drastic changes in the estimated internal temperature.

[0060] Figure 6 This is a graph showing the change in the internal temperature of the secondary battery 1 over time as the Joule heat generated by charging and discharging causes the internal temperature to rise, and then as the charging and discharging stops and the internal temperature drops. The horizontal axis represents time, and the vertical axis represents internal temperature. Line 31 represents the measured internal temperature of the secondary battery 1, line 32 represents the internal temperature estimated by the internal temperature estimation device 10 using two variations 21 and 22, and line 33 represents the internal temperature estimated using only one variation (as in the past). Figure 6 The internal temperature is estimated by the change in internal resistance relative to the charge rate measured during charging (22). As shown in the figure, the internal temperature 32 estimated by using two changes 21 and 22 as in this invention is closer to the measured temperature 31 than the internal temperature 33 estimated by the conventional method of estimating internal temperature.

[0061] The method, apparatus, program, and storage medium storing the program for estimating the internal temperature of a secondary battery according to the present invention have been described above. However, the present invention is not limited to the embodiments described above, and includes the concept of the present invention and all the embodiments included in the claims. For example, the estimation of the state of charge (SOC) (steps 53, 56, 64) may also be implemented by other methods instead of the method for estimating the cumulative charge and discharge current described in the above embodiments.

[0062] Symbol Explanation

[0063] 1. Secondary battery

[0064] 2. Charging circuit

[0065] 3. Load

[0066] 10. Internal temperature estimation device

[0067] 11. Voltage sensor

[0068] 12. Current sensor

[0069] 13. Memory

[0070] 14. Controller

[0071] 15. Temperature sensor

[0072] 21. First change (change while stationary or at the start of driving)

[0073] 22. Second change (changes during driving)

Claims

1. A method for estimating the internal temperature of a vehicle secondary battery, characterized in that, include: The repetitive variation determination process and the repetitive internal temperature estimation process. The change determination process includes: The step of determining the first change in internal resistance relative to the charging rate of the secondary battery based on the voltage and charging / discharging current of the secondary battery when the vehicle is stopped or when driving begins; The step of calculating the second change in internal resistance relative to the charging rate of the secondary battery based on the voltage and charging / discharging current of the secondary battery during vehicle operation. The internal temperature estimation process includes: The step of measuring the external temperature of the secondary battery; The step of measuring the charge and discharge current of the secondary battery; The steps to determine the charging rate of the secondary battery; The step of determining whether the secondary battery is discharging; When the secondary battery is discharging, the first change step is selected; When the secondary battery is not discharging, select the second change step; The step of determining the internal resistance of the secondary battery based on the selected variation and the calculated charging rate; The step of estimating the internal temperature of the secondary battery based on the external temperature, the measured charge / discharge current, and the internal resistance.

2. The method according to claim 1, further comprising: The step of determining whether the calculated charging rate is within the range of 20% to 80% In the step of determining the internal resistance, when the determined charging rate is within the range, the internal resistance of the secondary battery is determined based on the change selected in the previous repetition and the determined charging rate.

3. The method according to claim 1, further comprising: The step of determining whether the calculated charging rate is within the range of 20% to 80%; When the calculated charging rate is within the specified range, the first change step is selected regardless of whether the secondary battery is discharging.

4. The method according to any one of claims 1 to 3, further comprising: The step of correcting the calculated internal resistance based on the internal temperature estimated during the previous repetition.

5. An apparatus for estimating the internal temperature of a vehicle secondary battery, characterized in that, have: A voltage sensor that measures the voltage of the secondary battery; A current sensor that measures the charging and discharging current of the secondary battery; A temperature sensor that measures the external temperature of the secondary battery; A memory that stores a first change in the internal resistance relative to the charging rate of the secondary battery when the vehicle is stopped or when driving begins, and a second change in the internal resistance relative to the charging rate when the vehicle is in motion. The controller is capable of communicating with the voltage sensor, the current sensor, the temperature sensor, and the memory. The controller is configured to repeatedly execute a change determination process and an internal temperature estimation process. The change determination process includes: The first change is determined based on the voltage and charging / discharging current of the secondary battery when the vehicle is stopped or when it starts driving; Based on the voltage and charging / discharging current of the secondary battery while the vehicle is in motion, the second change is calculated. The internal temperature estimation process includes: The external temperature of the secondary battery, as measured by the temperature sensor, is obtained. The charging and discharging current of the secondary battery, as measured by the current sensor, is obtained. Calculate the charging rate of the secondary battery. Determine whether the secondary battery is discharging. When the secondary battery is discharging, the first change is selected. When the secondary battery is not discharging, the second change is selected. Based on the selected variation and the charging rate, the internal resistance of the secondary battery is determined. The internal temperature of the secondary battery is estimated based on the external temperature, the measured charge / discharge current, and the internal resistance.

6. A program that is a control program for a device for estimating the internal temperature of a vehicle secondary battery, characterized in that, The device includes: A voltage sensor that measures the voltage of the secondary battery; A current sensor that measures the charging and discharging current of the secondary battery; A temperature sensor that measures the external temperature of the secondary battery; A memory that stores a first change in internal resistance relative to the charging rate of the secondary battery when the vehicle is stopped or when driving begins, and a second change in internal resistance relative to the charging rate when the vehicle is in motion. The controller includes a processor and is capable of communicating with the voltage sensor, the current sensor, the temperature sensor, and the memory. The control program causes the processor to repeatedly execute the change determination process and the internal temperature estimation process. The change determination process includes: The first change is determined based on the voltage and charging / discharging current of the secondary battery when the vehicle is stopped or when it begins to move. The second change is determined based on the voltage and charging / discharging current of the secondary battery during vehicle operation. The internal temperature estimation process includes: The external temperature of the secondary battery, as measured by the temperature sensor, is obtained. The charging and discharging current of the secondary battery, as measured by the current sensor, is obtained. Calculate the charging rate of the secondary battery. Determine whether the secondary battery is discharging. When the secondary battery is discharging, the first change is selected. When the secondary battery is not discharging, the second change is selected. The internal resistance of the secondary battery is determined based on the selected variation and the charging rate. The internal temperature of the secondary battery is estimated based on the external temperature, the measured charging and discharging current, and the internal resistance.

7. A computer-readable storage medium storing the program of claim 6.

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