Battery deterioration diagnostic device

Abstract

To provide a storage battery deterioration diagnosis device that can perform extremely accurate deterioration diagnosis of storage batteries used in emergency power supplies, uninterruptible power supplies, operation power supplies, etc., and can avoid repeated short-time discharge tests. [Solution] In a storage battery deterioration diagnosis device that discharges a current required for diagnosis for a fixed short time into one storage battery to be diagnosed out of multiple storage batteries connected in series, and measures the terminal voltage multiple times over time, the device is provided with a current detection unit 1 that detects and measures the discharge current of the storage battery to be diagnosed, a voltage detection unit 2 that detects and measures the terminal voltage of the storage battery to be diagnosed, and a central processing unit X that is equipped with a first current control unit 3 and a first discharge switch 4 to control discharge for deterioration measurement, and the central processing unit X is equipped with a second current control unit 5 and a second discharge switch 6, and discharge for eliminating capacitance charge is controlled by pre-discharging the second discharge switch 6 for a fixed time. During deterioration diagnosis, discharge control of the second discharge switch 6 is performed first.

Description

[Technical Field]

[0001] This invention relates to a battery deterioration diagnosis device that can perform extremely accurate deterioration diagnosis of storage batteries used in emergency power supplies, uninterruptible power supplies, operational power supplies, etc., and can avoid the need for repeated short-term discharge tests. [Background technology]

[0002] The most effective way to determine the capacity of a battery is to actually discharge it. This involves preparing a real load or an equivalent mock load and discharging it for a long period of time, which gives highly accurate results, but it can take a long time and there are problems such as the fact that such tests cannot be performed while the actual load is in operation. Therefore, a method is used in which the current is discharged for a short period of time and the diagnosis is made based on the change in the terminal voltage of the battery at that time.

[0003] When diagnosing a storage battery through short-time discharge, since the storage battery is a direct current, it has been common for the battery to be connected in reverse, resulting in an abnormal current flow, and so measurement must be performed with due care taken to ensure polarity. In other words, in a storage battery diagnostic device that uses short-time discharge, since the storage battery has positive and negative electrical polarity, it is necessary to connect the voltage and current terminals correctly. Meanwhile, a storage battery system is composed of multiple storage batteries (for example, in the case of a 100V DC power supply, 52 to 54 lead-acid storage batteries). In this specification, a single storage battery is often referred to as a "cell." In other words, storage battery and cell are the same term. Alkaline storage batteries have 80 to 86 cells connected in series. UPS (uninterruptible power supply) can have even more, with around 200 cells.

[0004] Therefore, in cited document 1, an invention has been developed that includes a current detection unit that detects and measures the discharge current of the storage battery under diagnosis, a voltage detection unit that detects and measures the terminal voltage of the storage battery under diagnosis, and a control unit that includes a current control signal unit, a diode control signal unit, and a polarity determination unit, so that the storage battery equipment can accurately diagnose the deterioration of multiple (many) storage batteries under diagnosis while connecting the polarity correctly.

[0005] The current state of battery inspection, which measures the floating voltage of each cell, is that during float charging, the capacitance charge Vc due to the capacity of the electric double layer present in each cell inflates the terminal voltage, making it impossible to detect the level of degradation even if the electromotive force E drops due to battery degradation. In the case of severely degraded batteries, it is possible to detect the degradation using only the floating voltage, but this is limited to very severe cases. The current state of battery inspection, which measures the internal resistance of each cell, mainly involves calculating the internal resistance from the impedance measurement by applying an AC voltage in order to perform internal measurements during float charging.

[0006] Current battery inspection methods for measuring the floating voltage of each cell include (1) measuring a weak current generated by a high-frequency AC voltage, and (2) calculating the internal resistance from the synthetic impedance. However, these methods are significantly affected by capacitance C, making it difficult to calculate the true internal resistance R1 + R2. Measurements have shown that the larger the capacity of a battery, the smaller its internal resistance becomes, which increases the effect of capacitance C and leads to a larger discrepancy between the measured result and the actual resistance. Currently, approximately 80% of facilities are inspected in addition to the floating voltage measurement described above, but this method lacks accuracy. In actual field situations, there have been many cases where facilities that were deemed to have no problems using this inspection method experienced system downtime when switching to battery operation in an emergency.

[0007] Here, we will explain the basic structure of the connected storage battery again. As shown in Figure 8, in the conventional known diagram, the storage battery to be diagnosed (storage battery 8) is charged and discharged via a charger. Here, the internal structure of the storage battery to be diagnosed is defined as E: electromotive voltage, R: internal resistance (R1 + R2), Vc: capacitance voltage due to the electric double layer, Ic: charging current, and Id: discharging current. Also, the terminal voltage of the storage battery during charging or discharging is defined as VB. Then, in Figure 9, during charging, VB=E+Ic×R1+Vc. In other words, during charging, the terminal voltage was increased by the capacitance voltage Vc due to the electric double layer, making it impossible to measure the correct voltage value. However, during discharge, the cell (storage battery) becomes VB=E-((Id×R1)+(Id×R2)), The capacitance voltage Vc due to the electric double layer disappears almost instantly.

[0008] If we consider these points in detail, as shown in Figure 8(B), for a number of storage batteries to be diagnosed, the measurement unit K is brought into contact with the anode and cathode of one storage battery to be diagnosed, and the battery is charged, etc., and measurements are taken in sequence, as shown in Figure 8(A), with measurements being taken as measurement 1, measurement 2, ... measurement n.

[0009] Specifically, as shown in Figure 6(A), when n series-connected cells (storage batteries) are normal, each cell is charged with the charger voltage Vc / n. Next, as shown in Figure 6(B), when cell (1) is discharged (constantly) for a short time, the voltage of cell (1) temporarily drops, but the charger voltage Vc remains unchanged, so the charging voltages of cells (2) to (n) increase. This increased voltage is stored in the capacitance of each cell.

[0010] As shown in Figure 6(C), if cell (2) is subsequently discharged for a short time before the voltage of cell (1) recovers, the charge voltage of cell (2) as well as cell (1) drops, causing the charge voltages of cells (3) through (n) to rise further. Next, as shown in Figure 6(C), if short discharges are repeatedly performed in this manner, the charge voltages of cells not being tested rise, albeit temporarily. This leads to the problem that cells in the latter half of the test are significantly affected by capacitance, as shown in Figure 6(D).

[0011] Further, a specific experimental example is shown in FIG. 7. In FIG. 7(A), the first cell is measured and charging begins, showing an open-circuit diagram during charging. Then, as shown in FIG. 7(B), the first cell is discharged (for approximately 0.5 seconds). Immediately after this discharge is completed, the floating voltage Vc is applied to many cells other than the first cell, as shown in FIG. 7(C). Under these conditions, the battery deterioration diagnosis for the first cell is completed. Finally, in FIG. 7(D), the second cell is about to be measured. At this time, the deterioration diagnosis is performed with a portion of the floating voltage Vc applied to the second cell.

[0012] If measurements are taken in this way, successively, as in measurement 1, measurement 2, ... measurement n, the floating voltage Vc of the terminal voltage of each cell during the measurement gradually increases, and as shown in Figure 7(E), if the terminal voltage is the vertical axis and the first to nth are the horizontal axis, a floating voltage is generated and gradually increases. This causes the inconvenience of making it difficult to accurately measure degradation.

[0013] These points can be seen in the data diagram shown in Figure 5. In other words, Figure 5(A) shows the results of a short-time discharge test measured on a cell close to the beginning, and at this time, a certain value of capacitance charge is observed. Figure 5(B) also shows a small value of capacitance charge when measured on the first cell, and Figure 5(C) shows a large value of capacitance charge. In this way, as the nth measurement approaches the end, it becomes difficult to accurately measure degradation, which is an inconvenience.

[0014] The reason why degradation measurement is difficult in this way is also related to the fact that the discharge time is constant. In other words, because the discharge time is constant whether it is the first cell, the second cell, or the nth cell, the charge on the capacitance increases as it approaches the end, so the discharge voltage changes each time, and the discharge data within a certain period of time also changes. This poses a major problem that makes it difficult to accurately measure degradation. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-10450 Summary of the Invention [Problem to be solved by the invention]

[0016] Thus, the problem (technical problem or purpose, etc.) that this invention aims to solve is to eliminate floating voltage and measure the deterioration of the storage battery being diagnosed as electromotive force, while making the measurement more accurate. [Means for solving the problem]

[0017] Therefore, the inventor has conducted extensive research to solve the above problem, and as a result, the invention of claim 1 has been developed as a battery deterioration diagnosis device that discharges a current required for diagnosis for a fixed short time from one of multiple series-connected batteries to be diagnosed, and measures the discharge current of the battery to be diagnosed, and the terminal voltages of the battery to be diagnosed during discharge and at the time of recovery after discharge multiple times over time for a set time period, The above problem was solved by providing a battery deterioration diagnosis device comprising a current detection unit that detects and measures the discharge current of the battery to be diagnosed, a voltage detection unit that detects and measures the terminal voltage of the battery to be diagnosed, and a central processing unit that is provided with a first current control unit and a first discharge switch to control discharge for deterioration measurement, and further, the central processing unit is provided with a second current control unit and a second discharge switch, and discharge for eliminating capacitance charge is controlled by pre-discharging the second discharge switch for a fixed period of time, and discharge control of the second discharge switch is performed first when diagnosing deterioration of the battery to be diagnosed.

[0018] The invention of claim 2 solves the above problem by providing a storage battery degradation diagnosis device as set forth in claim 1, characterized in that the first current detection unit, the first current control unit, and the first discharge switch are arranged in series in a closed circuit and the voltage detection unit is arranged in parallel, and the second current control unit and the second discharge switch are arranged in series and connected in parallel to the closed circuit.The invention of claim 3 solves the above problem by providing a storage battery degradation diagnosis device as set forth in claim 1 or 2, characterized in that the discharge time of the second discharge switch is approximately 20 ms to 400 ms, and the discharge time of the first discharge switch is approximately 500 ms. [Effects of the Invention]

[0019] The biggest advantage of the device of claim 1 is that it can eliminate capacitance charge, which was a source of error in conventional tests, during short-term testing during floating charge, thereby obtaining more accurate data. Furthermore, when diagnosing a deteriorated battery, a short-term discharge test (double check) is often performed again to verify its validity. However, with this device, when removing the capacitance charge, a constant, ultra-short discharge of electromotive force E is also performed, resulting in a single test equivalent to a double check. Therefore, even in such cases, a double test is not necessary, shortening measurement time and making measurements more economical while ensuring accuracy. The device of claim 2 ensures reliable operation. Furthermore, the device of claim 3 enables faster and more efficient battery deterioration diagnosis. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a circuit diagram of the entire configuration of the present invention. [Figure 2] (A) is a circuit diagram showing the basic process configuration of the present invention, and (B) is a circuit diagram showing the preliminary process configuration of the present invention. [Figure 3] 1A is a diagram showing short-time discharge test data for the preliminary process configuration and basic process configuration of the present invention, and FIG. 1B is a diagram showing short-time discharge test data for the preliminary process configuration and basic process configuration of the present invention separately. [Figure 4] FIG. 2 is a flowchart showing the preliminary process configuration and the basic process configuration of the present invention. [Figure 5] These are conventionally known figures, where (A) is a diagram showing the results of a short-time discharge test measured on a cell closest to the first, (B) is a diagram showing the results of a short-time discharge test measured on the first cell, and (C) is a diagram showing the results of a short-time discharge test measured on the last cell, the nth cell. [Figure 6] These are conventionally known diagrams. (A) is a diagram showing a state in which a charger is charging multiple parallel-connected cells. (B) is a diagram showing a state in which the first cell is discharged for a short time and diagnostic measurement is performed. (C) is a diagram showing a state in which the second cell is discharged for a short time and diagnostic measurement is performed. (D) is a diagram showing a state in which the fifth cell is discharged for a short time and diagnostic measurement is performed. [Figure 7] (A) is a diagram of an open circuit during charging of the first cell during measurement, (B) is a diagram of an open circuit during discharging of the first cell during measurement, (C) is a diagram of an open circuit immediately after discharging of the first cell during measurement, (D) is a diagram of an open circuit immediately before measuring the second cell, and (E) is a diagram of floating voltage data from the first cell to the nth cell, which is a diagram of a conventionally known data. [Figure 8] 1A is a conceptual diagram of cell deterioration diagnostic measurements from measurement 1 to measurement n, and FIG. 1B is a partial perspective view of specific storage batteries (cells) under test connected in series. [Figure 9] 1 is a circuit diagram and formula for the floating charge state during measurement, which is a conventionally known diagram. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 and 2 are block diagrams showing the configuration of a first embodiment of the present invention. In the diagram, reference numeral 1 denotes a current detection unit that detects and measures a discharge current connected in series to a closed circuit a, 2 denotes a voltage detection unit that detects and measures a terminal voltage connected in parallel to the closed circuit a, and X denotes a central processing unit (CPU), which is equipped with a first current control unit 3 and a first discharge switch 4. The first current control unit 3 measures a current for degradation measurement, and the first discharge switch 4 controls discharge for degradation measurement. The current detection unit 1 and the voltage detection unit 2 each include a rectifier. Furthermore, because the cell (storage battery) 8 is a direct current, polarity determination is important during charging and discharging. Currently available commercially available products are designed to accommodate both forward and reverse currents.

[0022] A closed circuit b is provided in parallel with the closed circuit a and connected to the current detection unit 1 and the first discharge switch 4. A second current control unit 5 and a second discharge switch 6 are provided in series with the closed circuit b. The second current control unit 5 measures the current for eliminating capacitance charge, and the second discharge switch 6 controls the discharge for eliminating capacitance charge. The second current control unit 5 and the second discharge switch 6 are wired to the central processing unit (CPU) X and configured to be controllable respectively.

[0023] Next, the operational procedure from the start of diagnosis to data registration according to the present invention will be explained based on the flowchart shown in Figure 4. In the figure, thin frames indicate operations performed by the operator, while thick frames indicate operations performed automatically by the diagnostic device. The diagnostic device is powered on, and as an initial diagnostic measurement, the current value to be discharged from the cell (storage battery) is input and set using a numeric keypad or the like (see S1). Press "Ready" (see S2) and press the measurement start button (see S3). Then, the second discharge switch for eliminating capacitance charge is turned on (see S4). This starts the discharge timer for eliminating capacitance charge (see S5).

[0024] Then, the discharge current is controlled to a constant value, and the voltage is measured and stored in the memory of the central processing unit X (see S6). Next, it is determined whether the discharge timer for capacitance charge elimination has expired (see S7). If it is not normal (NO), the process returns to before S6. Also, if it is normal (YES) in S7, the discharge switch for capacitance charge elimination is turned OFF (see S8). This voltage is stored in the memory of the central processing unit X while measurement continues (see S9). Next, it is determined whether the restoration timer for capacitance charge elimination has expired (see S10). If it has not expired (NO), the process returns to before S9. Also, if it has expired (YES) in S10, the process proceeds to later stage diagnostic measurement.

[0025] As a diagnostic measurement in the later stage, the first discharge switch is turned ON for the discharge test (see S11). This starts the discharge timer for the discharge test (see S12). Then, the discharge current is controlled to be constant, and the voltage is measured and stored in the memory of the central processing unit X (see S13). Next, it is determined whether the discharge timer for the discharge test has expired (see S14). If the voltage is not normal (NO), the process returns to before S13. If the voltage is normal (YES) in S14, the discharge switch for the discharge test is turned OFF (see S15). This voltage is measured and stored in the memory of the central processing unit X (see S16).

[0026] Next, it is determined whether the recovery timer for the discharge test has expired (see S17). If it is not normal (NO), the process returns to before S16. If it is normal (YES) in S17, the internal resistance is calculated from the discharge test data and stored in memory (see S18). At this time, the measured voltage, current, and calculated internal resistance values ​​are displayed on the panel (see S19). After confirmation (see S20), the process is completed by issuing an instruction to move on to measuring the next cell (storage battery) (see S21).

[0027] In the configuration of the present invention, the pre-discharge time is constant, specifically, about 20 ms to about 400 ms. Preferably, it is about 30 ms to about 300 ms. More preferably, the pre-discharge time is a constant time between about 50 ms and about 200 ms. Furthermore, the discharge time of the first discharge switch is about 500 ms. [Explanation of symbols]

[0028] a, b... closed circuit, 1... current detection unit, 2... voltage detection unit, X... central processing unit (CPU), 3...first current control section, 4...first discharge switch, 5...second current control section, 6...Second discharge switch, 8...Storage battery (cell), 9...Charger.

Claims

1. A battery deterioration diagnosis device that discharges a current required for diagnosis for a fixed short time from one of a plurality of series-connected batteries to be diagnosed, and measures the discharge current of the battery to be diagnosed, and the terminal voltages of the battery to be diagnosed during discharge and at recovery time after discharge, multiple times over time for a set period of time after discharge is completed, a current detection unit that detects and measures the discharge current of the storage battery to be diagnosed, a voltage detection unit that detects and measures the terminal voltage of the storage battery to be diagnosed, and a central processing unit that is provided with a first current control unit and a first discharge switch, and the discharge for deterioration measurement is controlled by the central processing unit; Furthermore, the central processing unit is provided with a second current control unit and a second discharge switch, and discharge for eliminating capacitance charge is controlled by pre-discharging the second discharge switch for a certain period of time, and the discharge control of the second discharge switch is configured to be performed first when diagnosing the deterioration of the storage battery to be diagnosed.

2. 2. The battery deterioration diagnosis device according to claim 1, wherein the first current detection unit, the first current control unit, and the first discharge switch are arranged in series in a closed circuit, and the voltage detection unit is arranged in parallel, and the second current control unit and the second discharge switch are arranged in series and connected in parallel to the closed circuit.

3. 3. The battery deterioration diagnosis device according to claim 1, wherein the discharge time of the second discharge switch is approximately 20 ms to 400 ms, and the discharge time of the first discharge switch is approximately 500 ms.

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