JP2004264076A - Service life diagnostic method for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly diagnose a service life of a battery. <P>SOLUTION: A service life diagnosing current I is impressed for a short time in the condition where a voltage of the battery 23 is a release voltage value and where no current flows, under the condition where a control circuit 27 is in a condition before the diagnosis, and the voltage value therein is detected using a voltage detecting circuit 26. The voltage value of the battery 23 due to the current impression is measured as a characteristic led up vertically from the release voltage value, led up gradually from a certain voltage value, and attenuated from a time point of current interruption, a voltage change value ΔV1 with respect to the release voltage is detected, and an impedance R (Ω) is calculated based on the voltage change value ΔV1 to judge the life of the battery. The battery life is properly diagnosed thereby in the time point when an influence of polarization due to the current impression increasing with the lapse of time is small, by impressing the life diagnosing current larger than a usual charging current value for the short time. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a method for diagnosing the life of a battery in an uninterruptible power supply or the like, and more particularly to a method for diagnosing the life of a nickel-metal hydride battery in advance.
[0002]
[Prior art]
In recent years, computer systems have been using an uninterruptible power supply to supply power for a predetermined time when a power outage or the like has occurred due to an increase in the scale of systems and data, and to ensure that data is saved during this power supply time. Have been. The uninterruptible power supply device includes a battery unit such as a nickel-metal hydride battery for charging when supplying commercial power to the computer system, and a power failure detection circuit for detecting a power failure or instantaneous power failure of the commercial power supply. Detects a power failure due to a commercial power supply interruption / overvoltage due to lightning strike / breaker down due to overpower due to other equipment / noise from other equipment / power failure due to human error etc. Is configured to be supplied.
[0003]
In addition, as a document in which the technology relating to the above-described uninterruptible device is described, for example, JP-A-2001-166016 is cited.
[0004]
[Problems to be solved by the invention]
In general, when the nickel-metal hydride battery used for this uninterruptible power supply is charged and discharged by repeating charging and discharging, the output power is reduced, and the capacity is less than a predetermined capacity or the backup time is less than a specified time. It is determined that the battery has reached the end of its service life, and the storage battery needs to be replaced.
[0005]
However, the battery life diagnosis requires maintenance personnel to manually measure the capacity or backup time of the uninterruptible power supply and determine whether the life is near or not, which is a problem that the life diagnosis is complicated. there were.
[0006]
As a method of diagnosing the life of the nickel-metal hydride battery, for example, as shown in FIG. 4, the fact that the impedance inside the battery has a characteristic of increasing with the deterioration of the battery is used, and the life when the impedance reaches a predetermined value is defined as the life. It is known to make a determination, and the impedance R (Ω) is obtained by the following equation. The range indicated by the broken line in FIG. 4 is the service limit. For example, when the impedance reaches 9Ω, it is diagnosed that the service life is limited.
[0007]
(Equation 1)
Impedance R (Ω) = Voltage change ΔV / Current I
[0008]
In the life diagnosis based on the impedance measurement, the voltage suddenly changes immediately after the current flows through the battery, and the battery voltage changes with time due to the influence of a chemical change of the battery called polarization by continuously flowing the current. The battery voltage rises, and when the supply of current is stopped, the battery voltage decreases. The polarization means, in principle, the amount of movement of a substance per unit time of a current. When this current is taken out, the voltage generally becomes (1) an ohmic component due to the electric resistance of an electrode, and (2) a reactant. Loss due to resistance (charge transfer resistance) generated when electrons move on the electrode surface, etc. (3) Resistance when the reactants in the electrolyte are resupplied to the electrode and exchange electrons, and then diffuse and move again from the electrode surface (Mass transfer resistance) is a phenomenon that occurs when three kinds of resistances of loss occur.
[0009]
The battery characteristics will be described with reference to the drawing. As shown in FIG. 5, in a state before the diagnosis of a state where the battery has a predetermined output voltage value and the current value is zero, the current I is measured in order to measure the internal impedance of the battery. When applied, as shown in the area under diagnosis, the current value I has a characteristic that changes in a rectangular shape, whereas the rising voltage value gradually rises from the rising value of the voltage value ΔV1 immediately after the current is applied, and When the current reaches ΔV and the application of the current is stopped, the characteristic is changed so as to gradually decrease as after diagnosis. It is known that the voltage value change amount ΔV1 at the time of rising tends to be lower for a battery battery that is newer, and to be higher for a battery that has deteriorated.
[0010]
In the measurement of the battery life by the impedance measurement, as shown in FIG. 5, since the battery voltage gradually increases immediately after the application of the current I, the battery voltage changes at the time of the measurement, and the impedance obtained by the calculation also changes. There is a problem that it is difficult to measure a long battery life.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-described disadvantages of the related art, and to provide a battery life diagnosis method capable of diagnosing the battery life with high accuracy.
[0012]
[Means for Solving the Problems]
In order to achieve the object, the present invention measures a battery impedance based on a battery that charges power by applying a predetermined charging current and a voltage value change amount when a life diagnosis current is applied to the battery. A method for diagnosing battery life based on the battery impedance, wherein the life diagnosis current is set to a current value of 0.1 C to 2 C, and the battery application time of the life diagnosis current is set to 1 millisecond to 1 second. A first feature is that the method includes a step of setting and measuring a battery impedance based on a voltage value change amount when the life diagnosis current is applied to the battery.
Note that the life diagnosis current described in this specification is represented by a unit “C”. This unit "C" is a unit represented by y = (x / t) [A], where the current value is y [A], the battery rated capacity is x [A · hour], and the charging time is t [hour]. For example, a charging current that can be fully charged in one hour is “1C”, and a charging current that can be fully charged in 30 minutes is “2C”, and a charging current that can be fully charged in two hours is “1C” based on this. 0.5C ".
[0013]
The present invention also provides a battery that charges power by applying a predetermined charging current, and a battery impedance measured based on a voltage value change amount when a life diagnosis current is applied to the battery. A method of diagnosing the life of a battery, comprising: a first step of charging the battery by applying the charging current to the battery; and stopping the application of the charging current to the battery. A second step of resting until the life diagnosis current is set to a current value of 0.1 C to 2 C, and a battery application time of the life diagnosis current is set to 1 millisecond to 1 second; A third step of measuring the battery impedance based on the amount of change in the voltage value when the battery is applied to the battery.
[0014]
Further, according to the present invention, in the battery life diagnosing method according to any one of the above aspects, before applying the life diagnosing current to the battery, a high-precision reference voltage is applied to a voltage detection circuit, and the current detection circuit is similarly applied. A third feature is that the method includes a step of reducing a detection variation of each detection circuit by applying a reference voltage.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a battery life diagnosis method according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating an embodiment of an uninterruptible power supply to which a battery life diagnosis method according to the present invention is applied, FIG. 2 is a diagram illustrating a first embodiment of a battery life diagnosis method according to the present invention, FIG. 3 is a diagram for explaining a battery life diagnosis method according to a second embodiment of the present invention.
[0016]
FIG. 1 is a diagram illustrating an example of a power supply system including an uninterruptible power supply 20 to which the battery life diagnosis method according to the present embodiment is applied. The system includes a switching power supply 10 that supplies a predetermined output power, When the power from the switching power supply 10 is normal, the power is supplied to the computer system 30 and the internal nickel-metal hydride battery 23 is charged. At the time of a power failure or the like, the power from the battery 23 is supplied to the computer system 30 for a predetermined time. And an uninterruptible power supply 20.
[0017]
The uninterruptible power supply 20 receives power from the switching power supply 10 via a line 1, charges a battery 23 via a line 4 in accordance with an instruction from a control circuit 27, and A charging / discharging circuit 22 for supplying power to the computer system 30 via a power supply; a voltage detecting circuit 21 for detecting a voltage supplied to the line 1; a current detecting circuit 24 for detecting a current value of the line 4; A voltage detection circuit 26 for detecting the voltage of the battery 23, a temperature detection circuit 25 for similarly detecting the temperature of the battery, and a device load level signal / AC / DC operation state signal / DC / DC state operation from the switching power supply 10. A control circuit that receives a signal and the voltage and temperature of the battery 23 and controls charging of the battery 23 and supply of power to a computer system (load). 7 and an interface for supplying power to the computer system via lines 8 and 9 / backup power supply abnormality signal 31 / power supply stop signal 32 / battery replacement instruction signal 33 and other control signals to the computer system in accordance with an instruction from the control circuit 27. And a circuit 28. The nickel-metal hydride battery 23 according to the present embodiment has a rated value of, for example, a voltage of 33.6 V, a current of 5.8 A / h, and a current value of 0.6 A during charging.
[0018]
In the battery life diagnosis method according to the present embodiment, the control circuit 27 makes a diagnosis according to a preset program. Next, the diagnosis method will be described with reference to FIG. First, the control circuit 27 that implements the life diagnosis method according to the present embodiment has a state in which the voltage of the battery 23 has a rated value of 33.6 V and a current value of 0 A (a state in which no current is flowing) before the diagnosis. ), The current I having the current value of 6 A is applied for a short time, and the voltage value at this time is detected using the voltage detection circuit 26.
[0019]
As shown in FIG. 2, the voltage value of the battery 23 due to the application of the current is measured as a characteristic that rises vertically from an open voltage of 33.6 V, gradually rises from a certain voltage value, and attenuates from the time of current interruption. When the peak voltage value is 40V, the difference from the open circuit voltage is calculated as ΔV1 = 40V−33.6V = 6.4V.
[0020]
The short time for applying the current is, for example, about 5 milliseconds, and is preferably a minimum limit value of a circuit for detecting a change in voltage and current, for example, a range of 1 millisecond to a maximum value of an allowable error of 1 second. The shorter the time, the better.
[0021]
In the life diagnosis method according to the present embodiment, the control circuit 27 applies a current of, for example, 6 A for 5 milliseconds by using the charge / discharge circuit 22, detects a voltage change (voltage rise value) ΔV1 at this time, and detects the voltage rise. The life of the battery 23 can be determined by calculating the impedance of the battery 23 from the value ΔV1 using the above-described formula, impedance R (Ω) = voltage change ΔV / current I. That is, in the life diagnosis method according to the present embodiment, the polarization by the application of the current is reduced by applying a life diagnosis current that is 10 times the normal charging current value (0.6 A) for a short time of about 5 milliseconds. The amount of change in the voltage value is measured at a time when the influence that increases with the passage of time is small, and the battery life can be properly diagnosed. Note that the life diagnosis current can be set to a current value that is 5 to 15 times the charging current, and the battery application time of the life diagnosis current can be set to 1 millisecond to 1 second. . The reason for setting the life diagnosis current to a current value that is 5 to 15 times as large as the charging current is that the charging current generally uses the surplus power during the power supply to the original load to the computer system or the like. In order to perform the charging, the voltage is set to a low current value, and when the charging current is applied for a short time, the amount of change in the voltage value of the battery is small and difficult to detect. , The set value.
[0022]
Further, the life diagnosis method according to the present embodiment applies a high-precision reference voltage to the voltage detection circuit 26 and the current detection circuit prior to the short-time application of the current by the charge / discharge circuit 22 described above, and detects the temperature characteristics of the detection and peripheral circuits. Is added to the control circuit 27, and the control circuit 27 executes the above-described voltage and current detection after executing the offset canceller function, thereby providing a more accurate battery. The battery life can be diagnosed by measuring the voltage value and the current value, that is, the impedance.
[0023]
Further, the life diagnosis method according to the present embodiment can perform the above-described life diagnosis after charging the battery 23. In this case, the control circuit 27 supplies the battery 23 with a current of 0.6 ° as shown in FIG. After the charging, the battery is charged (period during charging in FIG. 2), and a pause is provided for a predetermined time (period until the battery voltage reaches a predetermined falling point Pb from the time Pa during charging) after the charging is stopped. After that, a high current (6 °) is applied for a short period of time (5 milliseconds) for the life diagnosis, and the voltage change ΔV1 at this time is measured, whereby the life of the battery can be diagnosed. The pause period is a period until the voltage value detected from the battery is no longer affected by the polarization due to the charging of the battery, and it can be said that the life of the battery is diagnosed after a preset pause time.
[0024]
Further, the uninterruptible power supply 20 according to the present embodiment includes a temperature detection circuit 26 that detects the temperature of the battery 23, and the control circuit 27 uses the battery temperature detected by the temperature detection circuit 25 as a factor to calculate the temperature from the detected voltage value ΔV1. The calculated impedance value can be corrected, and the battery life can be diagnosed based on the corrected impedance value. The correction of the impedance value means that, for example, even if the detected impedance value is 8Ω, if the detected temperature is as high as 45 ° C. with respect to the predetermined temperature at the time of driving of 0 ° C. to 40 ° C., the deterioration is not caused. It is the one that advances fast and the one that corrects.
[0025]
As described above, in the battery life diagnosis method according to the present embodiment, the control circuit 27 of the uninterruptible power supply 20 applies a high current to the battery 23 for a short time compared to the charging current, By measuring the amount of change in voltage value ΔV1 increased from the open-circuit voltage value, the life of the battery can be accurately diagnosed without being affected by the polarization of the battery.
[0026]
When the control circuit 27 determines that the battery 23 has reached the end of its life as a result of the diagnosis, the control circuit 27 issues a battery replacement signal 33 to the computer system 30 via the interface circuit 28 to prompt the administrator to replace the battery. it can. Further, the control circuit 27 stores the measured battery impedance value in a memory (not shown), plots the impedance value, creates an impedance change graph from the transition, and calculates a predicted value of the graph in the future. Thus, it is possible to predict when the battery life will be reached and to warn the administrator at an early point.
[0027]
【The invention's effect】
As described above, in the battery life diagnosis method according to the present invention, the life diagnosis current is set to a current value of 0.1 C to 2 C, and the battery application time of the life diagnosis current is set to 1 millisecond to 1 second. By including the step of measuring the battery impedance based on the amount of change in the voltage value when the life diagnosis current is applied to the battery, the life of the battery can be accurately diagnosed without being affected by the polarization of the battery.
[0028]
The battery life diagnosing method according to the present invention includes a first step of charging the battery by applying a charging current and stopping the application of the charging current to the battery so that the voltage of the battery is affected by the polarization due to the charging of the battery. A second step of resting until the battery runs out, setting the life diagnosis current to a current value of 0.1 C to 2 C, setting the battery application time of the life diagnosis current to 1 millisecond to 1 second, and setting the life diagnosis current to By including the third step of measuring the battery impedance based on the amount of change in the voltage value when the battery is applied, the life of the battery after charging can be accurately diagnosed without being affected by polarization.
[0029]
Further, the present invention applies a high-precision reference voltage to the voltage detection circuit before applying the life diagnosis current to the battery, and also applies a reference voltage to the current detection circuit in the same manner. Accurate life diagnosis can be performed by reducing the variation.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an uninterruptible power supply to which a battery life diagnosis method according to the present invention is applied.
FIG. 2 is a diagram for explaining a first embodiment of a battery life diagnosis method according to the present invention.
FIG. 3 is a view for explaining a second embodiment of the battery life diagnosis method according to the present invention.
FIG. 4 is a diagram for explaining the principle of a battery life diagnosis method according to the related art.
FIG. 5 is a diagram for explaining a voltage change by a battery life diagnosis method according to the related art.
[Explanation of symbols]
1 to 5: power supply line, 10: switching power supply, 20: uninterruptible power supply, 30: computer system, 21: voltage detection circuit, 22: charge / discharge circuit, 23: nickel metal hydride battery, 24: current detection circuit, 25 : Temperature detection circuit, 27: control circuit, 28: interface circuit.

Claims (3)

A battery that charges power by applying a predetermined charging current, and a battery that measures battery impedance based on a change in voltage value when a life diagnostic current is applied to the battery and diagnoses battery life from the battery impedance , Wherein the current value is y [A], the battery rated capacity is x [A · hour], the charging time is t [hour], and the unit C is represented by y = (x / t) [A]. When the life diagnosis current is set to a current value of 0.1 C to 2 C, the battery application time of the life diagnosis current is set to 1 millisecond to 1 second, and the life diagnosis current is applied to the battery. A method of measuring battery impedance based on the amount of change in the voltage value of the battery. A battery that charges power by applying a predetermined charging current, and a battery that measures battery impedance based on a change in voltage value when a life diagnostic current is applied to the battery and diagnoses battery life from the battery impedance , Wherein the current value is y [A], the battery rated capacity is x [A · hour], the charging time is t [hour], and the unit C is represented by y = (x / t) [A]. A first step of applying the charging current to the battery to perform charging, and a second step of stopping the application of the charging current to the battery and stopping until the battery voltage reaches the rated voltage of the battery. The life diagnostic current is set to a current value of 0.1 C to 2 C, the battery application time of the life diagnostic current is set to 1 millisecond to 1 second, and the voltage value when the life diagnostic current is applied to the battery Measure battery impedance based on the amount of change Life diagnosis method of a battery, which comprises a third step. Before applying the life diagnosis current to the battery, a high-precision reference voltage is applied to the voltage detection circuit, and a reference voltage is similarly applied to the current detection circuit, thereby reducing the detection variation of each detection circuit. The method for diagnosing battery life according to claim 1 or 2, wherein:

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