JP2002334725A - Method for monitoring condition of lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately monitor a remaining capacity and a life of a lead-acid battery. SOLUTION: A correlative approximate expression of an internal resistance and a remaining capacity from the time when the internal resistance reaches a fixed value or more is found, and the remaining capacity is monitored based on it. When the remaining capacity becomes not more than 85% of the initial value, the correlative approximate expression of the internal resistance and the remaining capacity is found by the change of the internal resistance within a fixed time period, and the time of the battery life is estimated by the approximation to display it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a state monitoring method for monitoring a state of a lead storage battery such as a remaining capacity and a life.

[0002]

2. Description of the Related Art Conventionally, a lead storage battery is sometimes used as an emergency power supply. This stationary lead-acid battery is connected in parallel with a commercial power supply to a load, and is usually charged with a small current called float charging by the commercial power supply, the capacity of the lead-acid battery is maintained at 100%, and power is cut off to the commercial power supply. When an abnormal situation such as occurs, power is supplied from a lead storage battery to a load instead of the commercial power supply.

[0003] Such a stationary lead-acid battery is used by connecting a large number of lead-acid batteries in series. Such a lead-acid battery can be said to be or constantly being float-charged, so that the lead-acid battery will eventually deteriorate and eventually fail to supply sufficient power to the load. Are known. For this reason, the state of the lead-acid battery is monitored by measuring the voltage of the storage battery, measuring the internal resistance, and deriving the remaining capacity from the result to determine whether sufficient power can be actually supplied when the commercial power supply is abnormal. When the remaining capacity becomes equal to or less than a predetermined value, the life is determined and the lead storage battery is replaced.

[0004]

However, long-term use of these stationary lead-acid batteries is desired, and more accurate condition monitoring is desired.

[0005]

According to the present invention, in order to solve the above-mentioned problems, the invention according to claim 1 uses an initial value having a small internal resistance value when approximating the correlation between the internal resistance and the remaining capacity. Is ignored and the remaining capacity is monitored by approximating the correlation using values after the value at which the internal resistance value starts to increase, and the remaining capacity is monitored according to the first aspect of the present invention. When the remaining capacity measured by the method described above becomes 85% or less of the initial value, the remaining capacity value reaches a predetermined end time by an approximation formula that is approximated based on the internal resistance value data for a predetermined period from that time. The time is calculated and the life is predicted.

Further, according to a third aspect of the present invention, the internal resistance of each lead-acid battery is measured, and the remaining capacity and the life of each lead-acid battery are estimated from this.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An AC voltage can be applied to a stationary lead-acid battery during float charging with a small charging current, and the internal resistance can be determined from the voltage and current. This internal resistance has a correlation with the state of charge of the lead storage battery, that is, the remaining capacity. Therefore, the remaining capacity of the lead-acid battery can be monitored by measuring the internal resistance of the lead-acid battery. However, when actually examining the relationship between the internal resistance and the remaining capacity of a lead-acid battery, in the initial state where the internal resistance is low, there is no clear correlation, and it is more clear that the internal resistance has increased to some extent. It turns out that there is a correlation. Therefore,
When the numerical value in a state where the internal resistance value was low was deleted and an approximate expression was obtained from a correlation after the value became a certain value or more, a high correlation was obtained. Then, it was confirmed that there was no practical problem even when the remaining capacity was 100% during the period when the internal resistance was low.

In addition, since these stationary lead-acid batteries supply electric power to the load in the event of a commercial power failure, a remaining capacity that can supply a sufficient amount of electric power to the load is required. It is necessary to replace this as a lifetime. In this case, only by monitoring the state of the lead storage battery by measuring the internal resistance, it is possible to confirm when the life has expired, but it is not possible to predict when the life will be reached, and the conventional method relies on experience. Therefore, the present inventors have created a new approximate expression based on the internal resistance of a certain period in the past from the measurement time, in order to predict the end of life of the lead storage battery that has reached the state before the end of life, The life expectancy is predicted based on this.

[0009]

FIG. 1 shows a change in the remaining capacity and internal resistance of a lead storage battery by an accelerated life test using a fully charged nominal capacity 200 AH sealed lead storage battery. The horizontal axis indicates the internal resistance of the lead storage battery, and the vertical axis indicates the discharge capacity when discharging with a current of 0.16C. The conditions for the accelerated life test were as follows. A lead storage battery was placed in a water bath at 65 ° C., and a small current of 1 A was continuously passed through the battery. As the internal resistance, an alternating current having a constant frequency of 20 Hz was applied, and the internal resistance was calculated from the response voltage and the phase difference at that time. Then, a portion of the initial value having a small internal resistance value, that is, a portion of 0.568 mΩ or less in the example was deleted, and an approximate curve of the correlation between the internal resistance and the remaining capacity was obtained based on the larger internal resistance value. As a result, a correlation approximation formula of y = 314.8e ^{− 0.7409x} (y = remaining capacity, x = internal resistance) is obtained, and the correlation coefficient is 0.953, which is higher than the case where the conventional initial internal resistance is also included. A correlation was obtained. The internal resistance is a temperature-corrected value. The correlation value of 1.000 indicates a case where there is no deviation from the actual value, and the deviation from this indicates that the deviation is larger.

Next, this approximate expression was previously input to the storage unit of the computer. Connected to a sealed lead-acid battery having a nominal capacity of 200 AH, and connected to the positive and negative terminals of each lead-acid battery by an AC current input line to continue float charging at a current of 1 A, and once a day to a lead-acid battery at 20 Hz. The response voltage when the AC current is applied, the value of the applied AC current, and the like are input to the arithmetic unit, and the arithmetic unit calculates the internal resistance to obtain the internal resistance, which corresponds to the previously input approximate expression of the storage unit. The remaining capacity of the lead storage battery was calculated and displayed on the display unit, and the state of each lead storage battery could be monitored. This display value was confirmed to be practical without any significant difference from the result of a residual capacity test in which a lead storage battery was actually tested with a discharge current of 0.16 C.

[0011]

Embodiment 2 Next, a method of estimating the life of a lead storage battery will be described. The life of the lead storage battery in Example 1 was defined as the time when the remaining capacity reached 80% of the initial value. FIG. 2 shows that 12 lead-acid batteries of Example 1 are arranged close to each other, connected in series, and float-charged with a current of 1 A. 3 shows changes in the internal resistance (R) and the remaining capacity of three batteries having different values. The horizontal axis shows the number of months of the accelerated life test of Example 1 (below, along with the actual predicted years), and the vertical axis shows the internal resistance (R) and discharge capacity on the left and right. It can be seen that each lead storage battery shows a different transition of the internal resistance value. This is thought to be due to the effect of the temperature of the lead storage battery due to the environment of the lead storage battery depending on the location, particularly the location during float charging. From this result, it is clear that simply predicting when the remaining capacity will be 80% of the initial value from the value of the internal resistance is far from actual. In other words, some lead-acid batteries have a rapid rise in internal resistance and have a relatively short life remaining capacity, and some lead-acid batteries have a slow rise if they show a sudden rise.
This is because the behavior differs depending on the environment in which the lead storage battery is installed. Therefore, near the end of the life, in this embodiment, at least the time when the remaining capacity that can secure one year to reach the life is 85% is captured, and the subsequent state of the lead storage battery in this state is described before. The life expectancy is predicted from the change in internal resistance for six months, and thereafter, this prediction is updated based on the data for half a year before the data collection time. This enables more accurate life prediction.

More specifically, as shown in FIG.
Is connected to the load 3 via the rectification / control unit 2 and
The lead storage battery 4 is connected in parallel with the load. The lead-acid battery 4 has 12 fully-charged sealed lead-acid batteries having a nominal capacity of 200 AH connected in series, connected to the alternating current application line 5 at the positive and negative terminals of each lead-acid battery, and connected to the direct-current connected lead-acid battery 4 at 1 A. The float charging current was kept flowing. Once a day, the timer applies an alternating current of 20 Hz from the measuring unit 6 to the lead storage battery 4 from the application line 5 to input the information of the response voltage and the phase difference to the calculating unit. The temperature of each lead-acid battery is measured by a thermistor (not shown) fixed to the side of the battery case of each lead-acid battery, and is stored in the storage unit RAM8. The temperature of the measured internal resistance is corrected by a calibration curve indicating the correlation between the internal resistance and the internal resistance. Similarly, a program is stored by an approximate expression indicating the correlation between the internal resistance and the remaining capacity previously input to the storage unit RAM8. ROM 9
The remaining capacity of the lead storage battery was determined by the following. The result is stored in the storage unit RAM 8 as data, and "good" is displayed until the remaining capacity is reduced to 85% from the initial capacity, and "warning" is displayed in the range of 85% to 80%. Is displayed on the screen. During the display of the “warning”, an approximate expression of a quadratic function is obtained separately from the above-mentioned approximate expression from the internal resistance value of the previous half year, and the remaining capacity as the life is 8
The time at which it reaches 0% was calculated, and the result was displayed on the display unit 10 as "How many years" until the life was reached as the life expectancy. The approximate value of the resistance value at this time was determined by a value without temperature correction. As a result, it is possible to predict the life more realistically.

The calculation section performs calculation according to the flowchart shown in FIG. 4 according to the program stored in the storage section ROM9. First, it is determined whether or not the lead storage battery is float-charged. As described above, the lead storage battery discharges when an abnormal situation such as a power failure occurs in a commercial power supply, and supplies power to a load. After the commercial power supply is restored, when the battery is charged by the commercial power supply and becomes fully charged, float charging is performed again.However, when discharging or charging the lead storage battery, no AC current is applied, and measurement of the internal resistance is not performed. do not do. In order to do this, an alternating current is applied periodically only when the lead storage battery is in the float charge state. The state of the float charge was determined by monitoring the voltage of the lead storage battery. When the state of the lead storage battery is float charging, an alternating current is applied to calculate and measure the internal resistance of each lead storage battery, and the remaining capacity is calculated by a correlation approximation equation between the previously input internal resistance and the remaining capacity. Ask for. Next, the obtained remaining capacity is the remaining capacity 8 determined as the life.
It is determined whether it is 0% or more, and if it is less than 0%, the life is displayed and an alarm is issued. If it is 80% or more, it is then determined whether or not the remaining capacity is 85% or more. If it is below, a warning is displayed, and at that time, the correlation between the internal resistance and the remaining capacity is obtained as an approximate expression of a quadratic function from the transition of the internal resistance value for six months from that time, and the remaining capacity is calculated from this approximate expression. The time when the battery life reaches 80% is calculated, the life time is predicted by subtracting it from the present time, and the predicted life is displayed. Thereafter, this operation is repeatedly executed.

Table 1 shows the results obtained by confirming the life expectancy of the five sealed lead-acid batteries at different locations by an approximate expression when the remaining capacity is 85% and the actually measured life years by an accelerated life test. The result was almost satisfied, with the error between the prediction and the actual measurement being within about 0.2 years.

[0015]

[Table 1]

Table 2 shows the results of examining the capacities and display states of five sealed lead-acid batteries having different residual procedures.

[0017]

[Table 2]

This result was also almost satisfactory.

In each of the above-described embodiments, the internal resistance value is used as it is. However, for example, a value obtained by averaging the internal resistance data for one week or an average value in January may be used. good.

[0020]

As described above, according to the present invention, as a method for monitoring the state of a lead-acid battery, it is possible to accurately display the remaining capacity and life expectancy of the lead-acid battery, and to accurately monitor the state of the lead-acid battery. It is effective. In addition, by monitoring the individual state of each lead storage battery, it is possible to perform an appropriate response to each storage battery instead of group monitoring as an assembled battery.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the internal resistance and the capacity of a lead storage battery.

FIG. 2 is a diagram showing a relationship between a period, an internal resistance, and a lead storage battery capacity.

FIG. 3 is an explanatory view of one embodiment of the present invention.

FIG. 4 is a chart diagram of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Rectification / control part 3 ... Load 4 ... Lead storage battery 5 ... Application line

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuichi Watanabe 597 Jingzawa-ji Uehara, Imaichi-shi, Tochigi Furukawa Battery Co., Ltd.Imaichi Office F-term (reference) 2G016 CA00 CB06 CB12 CC04 CC06 CC27 CC28 CE00 5G003 AA01 BA03 EA05 EA08 5H030 AA06 AS03 FF41

Claims (3)

[Claims] An internal resistance of a lead-acid battery is measured, and a state of the lead-acid battery such as a remaining capacity of the lead-acid battery at the measured internal resistance is determined by an approximate expression showing a correlation between a predetermined internal resistance and a remaining capacity of the lead-acid battery. In the method of monitoring the state of the lead-acid battery to be monitored, an approximate expression of the correlation between the internal resistance and the remaining capacity of the lead-acid battery is obtained from an approximate expression from the time when the internal resistance becomes a certain value or more. Monitoring the remaining capacity of the battery and determining that the remaining capacity is fully charged when the internal resistance is equal to or less than a predetermined value. 2. The internal resistance of the lead-acid battery is measured, and the state of the lead-acid battery, such as the remaining capacity of the lead-acid battery at the measured internal resistance, is determined by an approximate expression indicating the correlation between the previously determined internal resistance and the remaining capacity of the lead-acid battery. In the method of monitoring the state of the lead storage battery to be monitored, an approximate expression showing a correlation between the internal resistance and the remaining capacity based on a change state of the internal resistance a certain period before the time when the remaining capacity decreases to 85% of the initial capacity. ,
A method for monitoring the state of a lead-acid battery, comprising predicting the life of the lead-acid battery based thereon. 3. The method for monitoring the state of a lead storage battery according to claim 1, wherein the state of the lead storage battery is monitored for each lead storage battery.