Battery degradation diagnostic system

Abstract

To provide a storage battery deterioration diagnosis system that eliminates the need to search for a frequency desirable for diagnosing deterioration.SOLUTION: A storage battery deterioration diagnosis system has: a current supply unit 2 that supplies AC current to a storage battery 1; a voltage measuring unit 3 that measures a voltage generated by the supplied current in the storage battery 1; and a deterioration determination unit 4 that determines deterioration of the storage battery from the AC current to be supplied and the measured voltage. The current supply unit 2 supplies AC currents with a plurality of frequencies to the storage battery 1. The deterioration determination unit 4 has an impedance calculation unit 41 that calculates impedance, and a storage unit 42 that stores a threshold of the impedance determined to be deteriorated for every frequency of the currents supplied by the current supply unit 2. When the calculated impedance exceeds at least one value of the thresholds, a deterioration determination unit CPU 43 determines that the impedance is deteriorated.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a deterioration diagnosis system for diagnosing the deterioration state of a storage battery used for an emergency power source or storing surplus power. 【Background Art】 【0002】 Storage batteries are used for emergency power sources during power outages, storing solar power generation power, etc. When a storage battery used for such purposes deteriorates, the power that can be stored decreases, and its function cannot be fully exerted. Therefore, it needs to be replaced when the deterioration has advanced to a certain extent. Therefore, as a technique for diagnosing the degree of deterioration, there is a method of supplying an alternating current to a storage battery, measuring the impedance, and diagnosing the deterioration state from the measured impedance value. For example, in Patent Document 1, when supplying an alternating current to a storage battery, the frequency is changed to measure the impedance for each frequency, the impedance at which the imaginary part becomes 0 is obtained based on the frequency characteristic curve, and the deterioration state of the storage battery is determined based on the impedance at this time. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2007-333494 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 However, in the deterioration determination method of Patent Document 1 above, since the frequency at which the imaginary part of the impedance becomes 0 must be selected, it takes time to search for the frequency, and the diagnosis of the degree of deterioration is not easy. 【0005】 Therefore, in view of such problems, an object of the present invention is to provide a deterioration diagnosis system for a storage battery that can diagnose deterioration without searching for a frequency. 【Means for Solving the Problems】 【0006】 To solve the above problems, the invention of claim 1 is a battery degradation diagnosis system comprising: a current supply unit that supplies alternating current to a battery; a voltage measurement unit that measures the voltage generated in the battery by the supplied current; and a degradation determination unit that determines the degradation of the battery from the supplied alternating current and the measured voltage, wherein the current supply unit supplies alternating currents of different frequencies to the battery individually, and the degradation determination unit Real resistance value and imaginary resistance value An impedance calculation unit calculates the impedance, and a frequency threshold value for the impedance used to determine degradation is set. Separate into real resistance values ​​and imaginary resistance values. The memory unit that stores the information and the calculated impedance Regardless of whether the resistance value is real or imaginary, at least one of them It is characterized by having a determination unit that determines that deterioration has occurred if a threshold is exceeded. This configuration allows for the individual supply of alternating currents of different frequencies to calculate the internal impedance of each battery, and then uses these calculated impedances at multiple frequencies to determine degradation. Therefore, it is possible to detect changes specific to the battery without having to search for frequencies to calculate impedance, and to perform degradation diagnosis. 【0007】 In addition, Because the real and imaginary resistance values ​​of the impedance are determined independently, highly accurate determination is possible even when conditions such as battery type and temperature differ. 【0008】 Claim 2 The invention is claimed 1 In the configuration described, the determination unit determines that degradation has occurred if at least two of the calculated impedances exceed a threshold value. This configuration makes it less susceptible to noise and allows for more reliable judgment. [Effects of the Invention] 【0009】 According to the present invention, the impedance inside the battery is calculated by supplying alternating currents of different frequencies, and degradation is determined based on the impedances of the multiple frequencies obtained. Therefore, it is possible to detect changes specific to the battery without having to search for frequencies to calculate the impedance, and degradation diagnosis can be performed. [Brief explanation of the drawing] 【0010】 [Figure 1] This is a diagram showing an example of a battery degradation diagnosis system according to the present invention. [Figure 2] This is a table showing threshold values. [Figure 3] This graph shows an example of the relationship between the State of Health (SOH) and the charge-discharge cycle of a storage battery. [Figure 4] This is a characteristic diagram showing an example of the relationship between the impedance and frequency of a storage battery, with the impedance displayed on a linear scale. [Figure 5] This is a characteristic diagram showing an example of the relationship between the impedance and frequency of a storage battery, with the impedance displayed on a logarithmic scale. [Modes for carrying out the invention] 【0011】 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a configuration diagram showing an example of a battery degradation diagnosis system 10 according to the present invention, and includes a current supply unit 2 that supplies alternating current to a battery 1, a voltage measurement unit 3 that measures the voltage generated in the battery 1, a degradation determination unit 4 that determines degradation, and the like. The degradation determination unit 4 includes an impedance calculation unit 41 that calculates the internal impedance of the battery 1, a storage unit 42 that stores threshold values ​​for determining degradation, and a degradation determination unit CPU 43 that controls the degradation determination unit 4. The degradation determination unit CPU 43 controls the current supply unit 2 to supply the battery 1 with, for example, alternating currents of multiple different frequencies at 100 milliamperes. 【0012】 Still, arrow I1 represents the discharge current supplied by the storage battery 1 to a load (not shown), arrow I2 represents the current supplied from a power source (not shown) to charge the storage battery 1, arrow i1 represents the alternating current supplied by the current supply unit 2 to the storage battery 1, and 5 represents a switch that disconnects the storage battery 1 from the load and the power source. When the alternating current i1 supplied to the storage battery 1 is affected by the discharge current I1 or the charge current I2, the switch 5 is turned on, and the storage battery 1 is disconnected from the power source and the load. 【0013】 The operation of the storage battery deterioration diagnosis system 10 configured as described above is as follows. Here, a case where alternating currents of three frequencies, 1 Hz, 10 Hz, and 20 Hz, are individually supplied from the current supply unit 2 to the storage battery 1 will be described. The deterioration determination is made based on SOH (State of Health), and when the SOH drops to a certain value, it is determined that deterioration has occurred. Here, a case where it is determined that deterioration has occurred when the SOH drops to 74% will be described for reasons to be described later. FIG. 2 shows the threshold values of the storage battery 1 to be diagnosed stored in the storage unit 42. When the calculated impedance exceeds this value, it is determined that the SOH has dropped to 74%. The threshold value used is the value of SOH 74%, but impedance data of 100% and 90% are also shown for reference. 【0014】 The deterioration determination unit CPU43, which is a determination unit, compares the real resistance values and imaginary resistance values of the three frequencies (a total of six values) calculated by the impedance calculation unit 41 with the six stored values, and determines that deterioration has occurred if at least one exceeds the threshold value. For example, if the real resistance value at a frequency of 1 Hz exceeds the threshold value of 5.69 mΩ earlier than other threshold values, it is determined that deterioration has occurred. Still, if the deterioration determination unit 4 determines that deterioration has occurred, notification means (not shown) performs a notification operation to prompt the replacement of the storage battery 1. [[ID=十七]] 【0015】 <000009Ⅰ>[ FIG. 3 shows an example of the relationship between SOH and the number of charge / discharge cycles. As shown in FIG. 3, the SOH becomes smaller as charge / discharge is repeated. Here, it is shown that when charge / discharge is repeated 400 times, the SOH becomes 90%, and when repeated 1000 times, it drops to 74%. 【0016】 Figures 4 and 5 show an example of the frequency characteristics of impedance measured by supplying an alternating current of 100 milliamperes. Figure 4 is a graph showing the frequency on a logarithmic scale and the impedance on a linear scale, and Figure 5 is a graph showing both the frequency and the impedance on a logarithmic scale. In Figures 4 and 5, R1 to R6 represent real resistance values, and X1 to X6 represent imaginary resistance values. R1 and X1 are for SOH 100% R3 and X3 are for SOH 90% R4 and X4 are for SOH 74% and each shows the data. As shown in Figures 4 and 5, the impedance increases as the number of charge-discharge cycles increases. And since the real component of the impedance changes greatly at low frequencies around 1 Hz and the imaginary component changes greatly around 10 Hz, by changing the frequency of the current supplied to measure the impedance, it becomes easier to extract the change characteristics of both the real component and the imaginary component, and it is possible to accurately determine the degree of deterioration. 【0017】 Thus, by supplying alternating currents with different frequencies, the impedance inside the storage battery 1 is calculated, and deterioration is determined based on the impedances at a plurality of obtained frequencies. Therefore, changes specific to the storage battery 1 can be detected without searching for the frequency for calculating the impedance, and deterioration diagnosis can be performed. Also, since the real resistance value and the imaginary resistance value of the impedance are determined independently, highly accurate determination is possible even when conditions such as the type and temperature of the storage battery 1 are different. 【0018】 In the above embodiment, it is determined that deterioration has occurred when one of the calculated impedances exceeds the threshold value. However, instead of determining that deterioration has occurred just because one value has exceeded the threshold, it may be determined that deterioration has occurred only when two or more calculated values exceed the threshold. In this case of determination, it is possible to be less affected by noise and perform a more reliable determination. Furthermore, while impedance was measured at three frequencies—1Hz, 10Hz, and 20Hz—the frequencies measured are not limited to these values. The number of frequencies can also be two, four, or more. Furthermore, while the supplied current is set to 100 milliamperes, it is advisable to increase the current value when measuring a small impedance. Furthermore, while the real and imaginary resistance values ​​of the impedance are independently compared to a threshold for determination, it is also possible to determine the degradation using a single impedance value without separating them into real and imaginary values, and by determining the degradation using multiple impedance values ​​with different frequencies, degradation can be detected. Furthermore, although the deterioration diagnosis is performed with the switch 5 in the closed state, if the discharge current I1 or charging current I2 of the storage and discharging 1 affects the diagnostic value in terms of variability, fluctuations, etc., the switch 5 may be in the open state. [Explanation of Symbols] 【0019】 1. Storage battery, 2. Current supply unit, 3. Voltage measurement unit, 4. Degradation determination unit, 10. Storage battery degradation diagnostic system, 41. Impedance calculation unit, 42. Memory unit, 43. Degradation determination unit CPU (determination unit).

Claims

[Claim 1] A battery degradation diagnosis system comprising: a current supply unit that supplies alternating current to a battery; a voltage measurement unit that measures the voltage generated in the battery by the supplied current; and a degradation determination unit that determines the degradation of the battery from the supplied alternating current and the measured voltage, The current supply unit supplies alternating currents of different frequencies to the storage battery individually, The aforementioned degradation determination unit includes an impedance calculation unit that calculates impedance using a real resistance value and an imaginary resistance value, A storage unit that stores the frequency threshold values ​​of the impedance to be judged for degradation, separated into real resistance values ​​and imaginary resistance values, A battery degradation diagnosis system characterized by having a determination unit that determines that degradation has occurred if at least one of the calculated impedance values ​​exceeds a threshold, regardless of the real resistance value and the imaginary resistance value. [Claim 2] The battery degradation diagnosis system according to Claim 1, characterized in that the determination unit determines that the battery has deteriorated if at least two of the calculated impedances exceed the threshold.

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