Battery degradation detection device and battery degradation detection method

Abstract

To provide a battery degradation detection device and a battery degradation detection method that can accurately determine battery degradation. [Solution] The battery degradation determination device according to the embodiment is a battery degradation determination device for determining battery degradation, and includes a controller. The controller calculates a change amount deviation rate, which is the deviation rate between a voltage change amount model stored in the memory unit that is detected when a degraded battery in a degraded state is charged or discharged, and the voltage change amount detected when the battery is charged or discharged, and determines whether or not the battery is in a degraded state based on the change amount deviation rate.

Description

Technical Field

[0001] The present invention relates to a battery deterioration determination device and a battery deterioration determination method.

Background Art

[0002] Conventionally, a technique for determining the capacity deterioration of a secondary battery mounted on a product has been known (see, for example, Patent Document 1). Patent Document 1 discloses a technique for comparing the charging characteristics (integrated value of current) when charging a target battery and an undeteriorated battery for deterioration determination, and determining the degree of deterioration based on the comparison result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, there is room for improvement in accurately determining battery deterioration. Specifically, in the prior art, capacity deterioration from the start to the end of charging is determined. In the prior art, for example, when charging from 50% to 80% of the remaining battery level, although it is possible to determine the degree of deterioration of the capacity between 50% and 80% based on the integrated value of the current during charging, the degree of deterioration of the entire capacity (from 0% to 100%) cannot be determined. Therefore, for products that need to keep the remaining battery level above a certain level, such as products that consume power and operate only in an emergency, it is difficult to determine the degree of deterioration of the entire capacity because they cannot be charged from 0% to 100%.

[0005] The present invention has been made in view of the above, and an object thereof is to provide a battery deterioration determination device and a battery deterioration determination method capable of accurately determining battery deterioration.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, the battery degradation determination device according to the present invention is a battery degradation determination device for determining battery degradation, and includes a controller. The controller calculates a change amount deviation rate, which is the deviation rate between a voltage change amount model stored in a memory unit that is detected when a degraded battery in a degraded state is charged or discharged, and the voltage change amount detected when the battery is charged or discharged, and determines whether the battery is in a degraded state or not based on the change amount deviation rate. [Effects of the Invention]

[0007] According to the present invention, the voltage during charging and discharging has the characteristic of changing differently depending on the degree of overall battery capacity degradation. Therefore, by comparing the rate of deviation in the voltage change between a degraded battery and a target battery, the degree of overall battery capacity degradation can be determined. In other words, according to the present invention, battery degradation can be determined with high accuracy. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing an overview of the battery degradation determination method according to the embodiment. [Figure 2] Figure 2 is a block diagram showing an example of the configuration of a battery degradation detection device. [Figure 3] Figure 3 shows the voltage change characteristics of unused and degraded batteries. [Figure 4] Figure 4 is a flowchart showing the processing procedure for the degradation determination process performed by the battery degradation determination device. [Modes for carrying out the invention]

[0009] The battery degradation determination device and battery degradation determination method according to the following embodiments will be described in detail below with reference to the attached drawings. However, the present invention is not limited to the embodiments described below.

[0010] First, an overview of the battery degradation determination method according to the embodiment will be described using Figure 1. Figure 1 is a diagram showing an overview of the battery degradation determination method according to the embodiment. The battery degradation determination method is performed by the battery degradation determination device 1 (see Figure 2). The battery degradation determination device 1 determines, for example, the capacity degradation of an in-vehicle device equipped with a secondary battery or a secondary battery installed in a vehicle.

[0011] Figure 1 shows the voltage changes detected at each time point t1 to t9 when the battery subject to degradation assessment was charged from time t1 to t9. Figure 1 also shows the voltage change characteristics when a degraded battery is charged or discharged between 0% and 100%. A degraded battery is one whose capacity at full charge has deteriorated (decreased) to the point where it is unusable as a battery. In other words, a degraded battery is one in which the remaining capacity at full charge has decreased by a threshold compared to an unused battery. Note that the graph of the voltage change characteristics of a degraded battery shown in Figure 1 can be generated, for example, based on the voltage measured from a degraded battery through experiments. Furthermore, these change characteristics differ depending on the degree of degradation of the battery's overall capacity. In other words, the voltage change characteristics differ between an unused battery and a degraded battery.

[0012] This disclosure focuses on the fact that the voltage change characteristics differ depending on the degree of battery degradation to determine battery degradation. Specifically, in this disclosure, the battery degradation determination device 1 calculates the deviation rate of the voltage change amount in a degraded battery and a target battery by executing a battery degradation determination method, and determines the degradation of the target battery based on the deviation rate.

[0013] Specifically, the battery degradation detection device 1 calculates the voltage deviation rate and slope deviation rate of the target battery and the degraded battery for each time from time t1 to time t9. Specifically, the battery degradation detection device 1 subtracts the voltage of the target battery from the voltage of the degraded battery at each time, and calculates the voltage deviation rate of the target battery by dividing the subtracted value by the voltage of the degraded battery. In the example shown in Figure 1, the battery degradation detection device 1 calculates the voltage deviation rate of the target battery for each time from time t1 to time t9.

[0014] Furthermore, the battery degradation detection device 1 calculates the slope of the voltage between time points from the amount of voltage change between time points for both the degraded battery and the target battery. It then subtracts the slope of the target battery from the slope of the degraded battery and divides the subtracted value by the slope of the degraded battery to calculate the slope deviation rate of the target battery. Note that the slope deviation rate is just one example of the change amount deviation rate. In the example shown in Figure 1, the battery degradation detection device 1 calculates the slope of the straight line connecting the voltages at each time point from the amount of voltage change between time points t1 to t9, and calculates the slope deviation rate of the target battery from this slope. In other words, the battery degradation detection device 1 calculates the slope deviation rate for each time point up to time t9, such as between time points t1 and t2, between time points t2 and t3, between time points t3 and t4, and so on.

[0015] The battery degradation determination device 1 then determines the degradation of the target battery based on the calculated voltage deviation rate and slope deviation rate of the target battery. Specifically, the battery degradation determination device 1 scores the voltage deviation rate and slope deviation rate and determines the degradation state according to the score. Specifically, the battery degradation determination device 1 sums the voltage deviation rates at each time from time t1 to time t9 and calculates a voltage score by normalizing the sum value by time (time from time t1 to time t9).

[0016] Similarly, the battery degradation detection device 1 calculates a slope score by summing the slope deviation rates for each time interval from time t1 to time t9 and normalizing the sum by time (the time interval from time t1 to time t9).

[0017] Then, the battery degradation determination device 1 compares each of the voltage score and the slope score with a threshold value. When both the voltage score and the slope score are less than the threshold value, it determines that the target battery is in a degraded state. Also, when either one of the voltage score and the slope score is less than the threshold value, the battery degradation determination device 1 determines that the target battery is in a state close to being degraded. On the other hand, when both the voltage score and the slope score are greater than or equal to the threshold value, the battery degradation determination device 1 determines that the target battery is not in a degraded state. That is, in the example shown in FIG. 1, since the voltage of the target battery is higher and the slope is steeper at each time compared to the degraded battery, the voltage score and the slope score are less than the threshold value, so it is determined that the target battery is in a degraded state.

[0018] Thus, since the voltage during charging and discharging has the characteristic that the amount of change differs according to the degree of degradation of the entire capacity of the battery, by comparing the voltage deviation rate and the slope deviation rate of the degraded battery and the target battery for degradation determination, the degree of degradation of the entire capacity of the target battery can be determined. That is, according to the present disclosure, the degradation of the target battery can be determined with high accuracy.

[0019] Note that in FIG. 1, an example in which the battery degradation determination device 1 performs degradation determination using both the voltage deviation rate and the slope deviation rate is shown, but a configuration in which degradation determination is performed using only the slope deviation rate may also be used.

[0020] Next, a configuration example of the battery degradation determination device 1 according to the embodiment will be described with reference to FIG. 2. FIG. 2 is a block diagram showing a configuration example of the battery degradation determination device 1. As shown in FIG. 2, the battery degradation determination device 1 includes a controller 2 and a storage unit 3. The storage unit 3 stores degradation model information 31 and unused model information 32.

[0021] The controller 2 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various circuits. The controller 2 executes the operations of the entire battery deterioration determination device 1 by the CPU executing the programs stored in the ROM using the RAM as a working area. Note that part or all of the controller 2 may be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array).

[0022] The storage unit 3 is, for example, a RAM or a data flash. Such a storage unit 3 can store information such as various program information. Note that the battery deterioration determination device 1 may acquire the above-described programs and various information via other computers connected by a wired or wireless network or a portable recording medium.

[0023] The deterioration model information 31 is information on a deteriorated battery change amount model indicating the change characteristics of the voltage of a deteriorated battery. Specifically, the deterioration model information 31 is information on the graph shown in FIG. 1. The unused model information 32 is information on an unused battery change amount model indicating the change characteristics of the voltage of an unused battery. Specifically, the unused model information 32 is information on the graph described later in FIG. 3.

[0024] The controller 2 performs deterioration determination of the target battery using the deterioration model information 31 and the unused model information 32 stored in the storage unit 3.

[0025] First, the controller 2 periodically detects the voltage of the target battery during charging or discharging of the target battery. Then, based on the amount of change in voltage between times of the voltage detected at each time, when the voltage is represented by a line graph, the controller 2 calculates the slope of the straight line when connecting the voltages between times with a straight line.

[0026] Next, the controller 2 reads the degradation model information 31 from the storage unit 3 and calculates the voltage deviation rate and slope deviation rate from the voltage and slope of the degraded battery and the target battery. Specifically, the controller 2 subtracts the voltage of the target battery from the voltage of the degraded battery at each time point, and calculates the voltage deviation rate of the target battery by dividing the subtracted value by the voltage of the degraded battery.

[0027] Furthermore, for both the degraded battery and the target battery, the controller 2 calculates the voltage slope over time from the change in voltage over time, subtracts the slope of the target battery from the slope of the degraded battery, and calculates the slope deviation rate of the target battery by dividing the subtracted value by the slope of the degraded battery.

[0028] The controller 2 then determines the degradation of the target battery based on the calculated voltage deviation rate and slope deviation rate of the target battery. Specifically, the controller 2 further uses the unused model information 32 to equalize the voltage deviation rate and slope deviation rate of the target battery. Specifically, the controller 2 calculates the voltage deviation rate and slope deviation rate of the degraded battery from the voltage of the degraded battery in the degradation model information 31 and the voltage of the unused battery in the unused model information 32. This point will be explained using Figure 3.

[0029] Figure 3 shows the voltage change characteristics of unused and degraded batteries. The graphs of voltage change characteristics of degraded and unused batteries shown in Figure 3 are based on the information from the degraded model information 31 and unused model information 32, and can be generated, for example, based on voltages measured from degraded and unused batteries through experiments.

[0030] As shown in Figure 3, the controller 2 subtracts the voltage of the degraded battery from the voltage of the unused battery at each time point (plot point of the unused battery), and calculates the voltage deviation rate of the degraded battery by dividing the subtracted value by the voltage of the unused battery.

[0031] Furthermore, for both degraded and unused batteries, controller 2 calculates the voltage slope over time from the change in voltage over time, subtracts the slope of the degraded battery from the slope of the unused battery, and divides the subtracted value by the slope of the unused battery to calculate the slope deviation rate for the degraded battery.

[0032] The controller 2 then equalizes the voltage deviation rate and slope deviation rate of the target battery based on the voltage deviation rate and slope deviation rate of the target battery and the voltage deviation rate and slope deviation rate of the degraded battery.

[0033] Specifically, Controller 2 equalizes the voltage deviation rate of the target battery by dividing the voltage deviation rate of the target battery by the voltage deviation rate of the degraded battery. In addition, Controller 2 equalizes the slope deviation rate of the target battery by dividing the slope deviation rate of the target battery by the slope deviation rate of the degraded battery.

[0034] Controller 2 then sums up the normalized voltage deviation rate and slope deviation rate for each time period and uses the sum of these sums for each time period as the degradation determination score. Specifically, if this score exceeds a threshold, Controller 2 determines that the battery is degraded, and if it is below the threshold, it determines that the battery is not degraded.

[0035] In other words, if the threshold is P, the battery in question is determined to be degraded if the following inequality is met.

[0036] P < Σ{(Voltage deviation rate of the target battery / Voltage deviation rate of the degraded battery) + (Slope deviation rate of the target battery / Slope deviation rate of the degraded battery)}

[0037] In the above formula, the range of Σ represents the elapsed time from the start of charging (or discharging) to the end of charging (or discharging). The threshold value P is set according to the elapsed time.

[0038] In this way, the controller 2 can reduce the difference in voltage between the range of small voltage changes (e.g., around 50%) and the range of large voltage changes (e.g., around 100%) by leveling the voltage deviation rate and slope deviation rate of the target battery. In other words, even if the target battery is charged within a range of small voltage changes, the controller 2 can determine the degradation of the target battery with high accuracy from the detected voltage.

[0039] Furthermore, the controller 2 performs degradation detection by summing the voltage deviation rate and the slope deviation rate and calculating a score based on the summation of the elapsed time. This allows for stable and accurate degradation detection even if, for example, the voltage detected at a specific time point becomes an abnormal value (outlier).

[0040] Next, the processing procedure for the degradation determination process performed by the battery degradation determination device 1 will be explained using Figure 4. Figure 4 is a flowchart showing the processing procedure for the degradation determination process performed by the battery degradation determination device 1. Figure 4 shows an example of the degradation determination process when the target battery is charged, but the degradation determination process can also be performed when the target battery is discharged.

[0041] As shown in Figure 4, when the controller 2 detects that the target battery has started charging (step S101), it periodically detects the voltage (step S102).

[0042] Next, the controller 2 determines whether or not charging of the target battery is complete (step S103). Specifically, the controller 2 detects a user's action to end charging (such as unplugging the charging cable) as the end of charging.

[0043] If the target battery has finished charging (step S103: Yes), controller 2 calculates the voltage slope between each detection point (voltage detected at each time point) (step S104). If the target battery has not finished charging (step S103: No), controller 2 returns to step S102.

[0044] Next, the controller 2 reads the degradation model information 31 and calculates the voltage deviation rate and slope deviation rate between the target battery and the degraded battery (step S105). Subsequently, the controller 2 reads the unused model information 32 and calculates the voltage deviation rate and slope deviation rate between the unused battery and the degraded battery (step S106).

[0045] Next, the controller 2 calculates a score by equalizing the voltage deviation rate and slope deviation rate of the target battery with the voltage deviation rate and slope deviation rate of the degraded battery, determines the degradation state based on the score (step S107), and terminates the process. Specifically, the controller 2 calculates the sum of the equalized voltage deviation rate and slope deviation rate of the target battery for each time period, and determines that the target battery is in a degraded state if the sum of the sums for each time period exceeds a threshold.

[0046] As described above, the battery degradation determination device 1 according to the embodiment is a battery degradation determination device 1 that determines the degradation of a target battery and has a controller 2. The controller 2 calculates a change amount deviation rate, which is the deviation rate between the voltage change amount model that is detected when a degraded battery in a degraded state is charged or discharged, which is stored in the storage unit 3, and the voltage change amount detected when the target battery is charged or discharged, and determines whether or not the target battery is in a degraded state based on the change amount deviation rate.

[0047] According to this disclosure, the voltage during charging and discharging has the characteristic of changing differently depending on the degree of overall battery capacity degradation. Therefore, by comparing the rate of deviation in the voltage change between a degraded battery and a target battery, the degree of overall capacity degradation of the target battery can be determined. In other words, according to this disclosure, the degradation of the target battery can be determined with high accuracy.

[0048] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0049] 1 Battery deterioration determination device 2 Controllers 3 Storage section 31. Information on degraded models 32 Unused Model Information

Claims

1. A battery degradation determination device for determining battery degradation, comprising a controller, The aforementioned controller, The system calculates the voltage change deviation rate of the battery, which is the difference between the voltage change model detected when a degraded battery in a degraded state, stored in the memory unit, is charged or discharged, and the actual voltage change detected when the battery is charged or discharged. Based on this voltage change deviation rate, it is determined whether or not the battery is in a degraded state. Battery deterioration determination device.

2. The aforementioned controller, The voltage deviation rate of the battery is calculated, which is the difference between the voltage detected when the degraded battery is charged or discharged and the voltage detected when the battery is charged or discharged. Based on the voltage deviation rate and the change amount deviation rate, it is determined whether or not the battery is in a degraded state. The battery degradation determination device according to claim 1.

3. The aforementioned controller, Based on the voltage detected when the degraded battery is charged or discharged and the voltage detected when the unused battery is charged or discharged, the voltage deviation rate and the change rate deviation rate of the degraded battery are calculated, and it is determined whether the battery is in a degraded state based on the voltage deviation rate and the change rate deviation rate of the battery and the voltage deviation rate and change rate deviation rate of the degraded battery. The battery degradation determination device according to claim 2.

4. The controller determines that the battery has deteriorated if the score calculated by the following formula exceeds a threshold, and determines that the battery has not deteriorated if the score is below the threshold. Score = Σ{(Voltage deviation of battery / Voltage deviation of degraded battery) + (Slope deviation of battery / Slope deviation of degraded battery)} The battery degradation determination device according to claim 3.

5. A battery degradation determination method performed by a battery degradation determination device for determining battery degradation, The system calculates the voltage change deviation rate of the battery, which is the difference between the voltage change amount detected when a degraded battery in a degraded state, stored in the memory unit, is charged or discharged, and the actual voltage change amount detected when the battery is charged or discharged. Based on the voltage change deviation rate, it is determined whether or not the battery is in a degraded state. How to judge battery deterioration.

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