Battery degradation diagnostic system

Abstract

To provide a storage battery deterioration diagnosis system in which upon supplying a measurement current, a storage battery does not become over-discharged, or over-recharged.SOLUTION: A deterioration diagnosis unit 4 is configured to: measure a voltage of a storage battery cell 1 before supplying a measurement current to the storage battery cell 1; supply a negative polarity pulsating current, as the measurement current, to the storage battery cell 1 when the measured voltage of the storage battery cell 1 exceeds a first threshold near an upper limit in a prescribed operation voltage range, on the other hand, when the voltage of the storage battery cell 1 is under a second threshold near a lower limit in the prescribed operation voltage range, supply a positive polarity pulsating current, as the measurement current, to the storage battery cell 1; and when the voltage of the storage battery cell 1 stays between the first threshold and second threshold, supply, as the measurement current, a prescribed AC current to the storage battery cells 1, and thereby perform control so that the voltage of the storage battery cell 1 varies within the operation voltage range.SELECTED DRAWING: Figure 1

Description

【Technical Field】 , , , , 【0006】 , , 【0005】 , , , 【0001】 The present invention relates to a battery deterioration diagnosis system for diagnosing the deterioration state of a battery used for, for example, an emergency power source or power storage of surplus power. 【Background Art】 【0002】 Conventionally, for example, a battery used for an emergency power source or power storage of surplus power deteriorates, resulting in a decrease in the power that can be stored and an inability to fully perform its function. Therefore, when the deterioration progresses to a certain extent, it needs to be replaced. Thus, as a deterioration diagnosis system for diagnosing the deterioration state of a battery, a system has been devised that supplies a measurement current (alternating current) to the battery to measure the impedance and diagnoses the deterioration state of the battery from the measured impedance value. <00000!0> 【0003】 For example, in the deterioration diagnosis system described in Patent Document 1, when supplying a measurement current to the 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 battery is determined based on this impedance. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2007-333494 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 However, in the deterioration diagnosis system described in Patent Document 1, when the voltage of the battery is close to the lower limit or the upper limit of the operating voltage range, there is a problem that the battery becomes over-discharged or over-charged when a measurement current is supplied. 【0006】 Therefore, the present invention has been made in view of the above problems and aims to provide a battery degradation diagnosis system that prevents the battery from being over-discharged or overcharged when a measurement current is supplied. [Means for solving the problem] 【0007】 To achieve the above objective, the invention described in claim 1 of the present invention is a battery degradation diagnosis system having a current supply unit that supplies a measurement current to a battery, a voltage measurement unit that measures the voltage of the battery, and a degradation diagnosis unit that diagnoses the degradation state of the battery by calculating the internal impedance of the battery from the supplied measurement current and the voltage at the time of supplying the measurement current, wherein the degradation diagnosis unit measures the voltage of the battery before supplying a measurement current to the battery, and if the measured voltage of the battery exceeds a first threshold closer to the upper limit of a predetermined operating voltage range, This is a current that fluctuates at a constant period on the negative voltage side. While supplying a negative polarity pulsating current to the battery as the measurement current, if the battery voltage falls below a second threshold near the lower limit of the operating voltage range, This is a current that fluctuates at a constant period on the positive side of the voltage. A positive polarity pulsating current is supplied to the battery as the measurement current, and further, when the voltage of the battery is between the first threshold and the second threshold, The voltage fluctuates with the same peak width for both positive and negative voltages, and with a constant period. The method is characterized by supplying an alternating current as the measurement current to the storage battery, thereby controlling the voltage of the storage battery to fluctuate within the operating voltage range. The invention described in claim 2 is characterized in that, in the invention described in claim 1, the storage battery is configured by connecting a plurality of storage battery cells in series, the degradation diagnosis unit diagnoses the degradation state of the plurality of storage battery cells, the current supply unit and the voltage measurement unit are provided for each storage battery cell, and the degradation diagnosis unit determines the type of measurement current to be supplied to each storage battery cell. ru. Na In this invention, a positive polarity pulsating current is a positive bias current that fluctuates at a constant period on the positive side, and a negative polarity pulsating current is a negative bias current that fluctuates at a constant period on the negative side. [Effects of the Invention] 【0008】 According to the present invention, the degradation diagnosis unit measures the voltage of the battery before supplying a measurement current to the battery, and if the measured voltage of the battery exceeds a first threshold near the upper limit of a predetermined operating voltage range, This is a current that fluctuates at a constant period on the negative voltage side. While supplying a negative polarity pulsating current to the battery as the measurement current, if the battery voltage falls below a second threshold near the lower limit of the operating voltage range, This is a current that fluctuates at a constant period on the positive side of the voltage. A positive polarity pulsating current is supplied to the battery as the measurement current, and furthermore, when the battery voltage is between the first threshold and the second threshold, The voltage fluctuates with the same peak width for both positive and negative voltages, and with a constant period. By supplying alternating current as the measurement current to the battery, the battery voltage is controlled to fluctuate within the operating voltage range. Therefore, even if the battery voltage is close to the lower or upper limit of the operating voltage range, the battery will not over-discharge or overcharge when the measurement current is supplied, making it possible to create a battery degradation diagnostic system that can accurately diagnose the degradation state of the battery. [Brief explanation of the drawing] 【0009】 [Figure 1] This is a diagram illustrating an example of a battery degradation diagnosis system. [Figure 2] This is an explanatory diagram showing the voltage waveforms in the battery cell when the measured voltage and measured current are supplied. [Figure 3] These are waveform diagrams of the pulsating current and alternating current supplied as the measurement current, with (a) showing negative polarity pulsating current, (b) showing positive polarity pulsating current, and (c) showing alternating current. [Modes for carrying out the invention] 【0010】 The following describes in detail, based on the drawings, a battery degradation diagnosis system, which is one embodiment of the present invention. 【0011】 Figure 1 is a diagram showing an example of a battery degradation diagnosis system 10. The degradation diagnosis system 10 comprises a battery consisting of a plurality of battery cells 1, 1... connected in series, current supply units 2, 2... provided for each battery cell 1 to supply measurement current to the battery cell 1, voltage measurement units 3, 3... provided for each battery cell 1 to measure the voltage of the battery cell 1, and a degradation diagnosis unit 4 for diagnosing the degradation of the battery cells 1, 1.... 【0012】 The degradation diagnosis unit 4 includes an impedance calculation unit 6 that calculates the internal impedance of the battery cell 1, a storage unit 7 that stores threshold values ​​related to degradation diagnosis, and a diagnosis unit CPU 8 that controls the degradation diagnosis unit 4. The diagnosis unit CPU 8 determines the type of measurement current to supply to the battery cell 1 under the control described later, and controls the current supply unit 2 to supply the measurement current to the battery cell 1. 【0013】 In Figure 1, arrow I1 represents the discharge current supplied by the battery to the load (not shown), and arrow I2 represents the current supplied from the power source (not shown) to charge the battery. Arrow i1 represents the measured current supplied by the current supply unit 2 to the battery cell 1, and 5 represents a switch that disconnects the battery from the load and power source. When supplying the measured current i1 to the battery cell 1, the switch 5 is closed. However, if the discharge current or charging current of the battery cell 1 causes variations or fluctuations in the diagnostic values, the switch 5 may be left open. 【0014】 Here, we will explain the control related to the diagnosis of battery cells 1, 1, etc. by the degradation diagnosis system 10. Figure 2 is an explanatory diagram showing the voltage waveform in battery cell 1 when the measured voltage and measured current are supplied. Figure 3 is a waveform diagram of the pulsating current and alternating current supplied as the measured current, where (a) shows the negative polarity pulsating current, (b) shows the positive polarity pulsating current, and (c) shows the alternating current. First, the degradation diagnosis unit 4 measures the voltage of the battery cell 1 to be diagnosed before supplying a measurement current to the battery cell 1. If the measured voltage of the battery cell 1 exceeds a first threshold near the upper limit of a predetermined operating voltage range (for example, the first measured voltage in Figure 2), there is a risk that the voltage of the battery cell 1 will exceed the upper limit of the operating voltage range when a predetermined AC current is supplied as the measurement current (for example, waveform C in Figure 2). Therefore, the degradation diagnosis unit 4 decides to supply a sinusoidal negative polarity pulsating current as shown in Figure 3(a) as the measurement current. On the other hand, if the measured voltage of the battery 1 falls below a second threshold near the lower limit of the operating voltage range (for example, 50% of the upper limit) (for example, the second measured voltage in Figure 2), there is a risk that the voltage of the battery cell 1 will fall below the lower limit of the operating voltage range when a predetermined AC current is supplied as the measurement current (for example, waveform B in Figure 2). Therefore, the degradation diagnosis unit 4 decides to supply a sinusoidal positive polarity pulsating current as shown in Figure 3(b) as the measurement current. Furthermore, if the measured voltage of the battery cell 1 is between the first threshold and the second threshold (for example, the third measurement voltage in Figure 2), there is no risk of the voltage of the battery cell 1 exceeding the upper limit or falling below the lower limit of the operating voltage range (for example, waveform A in Figure 2), so it decides to supply a predetermined alternating current as shown in Figure 3(c) as the measurement current. 【0015】 Then, the degradation diagnosis unit 4 controls the current supply unit 2 to supply the determined type of measurement current to the battery cell 1. At this time, the voltage of the battery cell 1 moves to the lower limit side (from waveform C to waveform A in Figure 2) when a negative polarity pulsating current is supplied, and to the upper limit side (from waveform B to waveform A in Figure 2) when a positive polarity pulsating current is supplied, and fluctuates within the operating voltage range. Therefore, the battery cell 1 does not become over-discharged or over-charged when the measurement current is supplied. 【0016】 Furthermore, the degradation diagnosis unit 4 calculates the internal impedance of the battery cell 1 when the above-mentioned measurement current is supplied, and diagnoses the degradation state of the battery cell 1 from the impedance value. The diagnosis of the degradation state of the battery cell 1 based on the impedance value can be performed using conventionally known methods, such as those described in Patent Document 1. 【0017】 According to the deterioration diagnosis system 10 having the above configuration, the deterioration diagnosis unit 4 measures the voltage of the storage battery cell 1 before supplying the measurement current to the storage battery cell 1. When the measured voltage of the storage battery cell 1 exceeds a first threshold value close to the upper limit in a predetermined operating voltage range, a negative-polarity pulsating current is supplied to the storage battery cell 1 as the measurement current. On the other hand, when the voltage of the storage battery cell 1 is lower than a second threshold value close to the lower limit in the operating voltage range, a positive-polarity pulsating current is supplied to the storage battery cell 1 as the measurement current. Further, when the voltage of the storage battery cell 1 is between the first threshold value and the second threshold value, a predetermined alternating current is supplied to the storage battery cell 1 as the measurement current, thereby controlling the voltage of the storage battery cell 1 to fluctuate within the operating voltage range. Therefore, even if the voltage of the storage battery cell 1 is in a situation close to the lower limit or the upper limit of the operating voltage range, the storage battery cell 1 will not be over-discharged or over-charged when the measurement current is supplied, and a deterioration diagnosis system 10 that can accurately diagnose the deterioration state of the storage battery cell 1 and thus the storage battery can be achieved. 【0018】 In addition, in the storage battery in which a plurality of storage battery cells 1, 1... are connected in series, in the deterioration diagnosis system 10 in which the deterioration diagnosis unit 4 diagnoses the deterioration state of the plurality of storage battery cells 1, 1..., the current supply unit 2 and the voltage measurement unit 3 are provided for each storage battery cell 1, and the deterioration diagnosis unit 4 is configured to determine the type of measurement current supplied for each storage battery cell 1. Therefore, a deterioration diagnosis system 10 that can accurately diagnose the deterioration state in units of the storage battery cell 1 and can take measures such as replacing only the deteriorated storage battery cell 1 can be achieved. 【0019】 Note that the storage battery deterioration diagnosis system according to the present invention is not limited to the aspects of the above embodiment. Not only the overall configuration of the deterioration diagnosis system but also the configuration related to the supply of the measurement current and the like can be appropriately changed as needed. 【0020】 For example, in the above embodiment, a current supply unit is provided for each battery cell. However, if we assume a situation where there is little difference in the charge state of multiple battery cells, it is possible to adopt a configuration in which only one current supply unit is provided for multiple battery cells. In such a degradation diagnosis system with only one current supply unit, the voltage of all battery cells is measured before supplying the measurement current. If even one battery cell has a voltage exceeding a first threshold, a negative polarity pulsating current is supplied to all battery cells as the measurement current. Conversely, if even one battery cell has a voltage below a second threshold, a positive polarity pulsating current is supplied to all battery cells as the measurement current. By adopting such a configuration, the number of components can be reduced, and the degradation diagnosis system can be constructed at a low cost. Furthermore, while the above embodiment states that a positive or negative pulsating current of a sinusoidal wave is supplied, any pulsating current that fluctuates with a constant period may be supplied, such as a triangular wave or a square wave, rather than a sinusoidal wave. [Explanation of Symbols] 【0021】 1. Battery cell, 2. Current supply unit, 3. Voltage measurement unit, 4. Degradation diagnosis unit, 6. Impedance calculation unit, 7. Memory unit, 8. Diagnostic unit CPU, 10. Degradation diagnosis system.

Claims

[Claim 1] A battery degradation diagnosis system comprising a current supply unit that supplies a measurement current to a storage battery, a voltage measurement unit that measures the voltage of the storage battery, and a degradation diagnosis unit that diagnoses the degradation state of the storage battery by calculating the internal impedance of the storage battery from the supplied measurement current and the voltage at the time the measurement current is supplied, The degradation diagnosis unit measures the voltage of the battery before supplying a measurement current to the battery, If the measured voltage of the battery exceeds a first threshold near the upper limit of a predetermined operating voltage range, a negative polarity pulsating current, which is a current that fluctuates at a constant period on the negative side of the voltage, is supplied to the battery as the measured current. On the other hand, if the voltage of the battery falls below a second threshold near the lower limit of the operating voltage range, a positive polarity pulsating current, which is a current that fluctuates at a constant period on the positive side of the voltage, is supplied to the battery as the measured current. Furthermore, if the voltage of the battery is between the first threshold and the second threshold, an alternating current, which is an alternating current, fluctuates at a constant period with the same peak width for both positive and negative voltages, is supplied to the battery as the measured current. A battery degradation diagnosis system characterized by controlling the voltage of the battery so that it fluctuates within the operating voltage range. [Claim 2] The aforementioned battery is configured by connecting multiple battery cells in series. The degradation diagnosis unit diagnoses the degradation state of the plurality of battery cells, The current supply unit and the voltage measurement unit are provided for each of the battery cells. The battery degradation diagnosis system according to claim 1, characterized in that the degradation diagnosis unit determines the type of measurement current to be supplied to each of the battery cells.

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