JPH10334952A - Lead-acid battery life determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a life determination method by which the life of a lead-acid battery can be determined with higher precision in a short time. SOLUTION: For determining lifetime, a lead-acid battery is periodically discharged in a short time high rate constant current, terminal voltages before and after every discharge image are measured, and the lifetime is determined utilizing a difference voltage between the measured terminal voltages. When the difference voltage of the terminal voltages before and after every discharge time is equal to a predetermined reference difference voltage or more, it is determined (step ST4) as a battery life. When the terminal voltage at the discharge termination time when the number of times reaches a predetermined number of discharge times is equal to a predetermined reference voltage or less, it is determined (step ST5) that the battery lifetime isover, even if the every time difference voltage is smaller than the reference difference voltage. When the difference voltage of the terminal voltage at the first discharge termination time and the terminal voltage at the discharge termination time when the number of times reaches the predetermined number of discharge times is equal to an upper limit reference voltage or more, it is determined (step 6) that the battery lifetime is over.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the life of a lead-acid battery, and more particularly to a method for determining the life of a sealed lead-acid battery.

[0002]

2. Description of the Related Art Various methods for determining the life of a lead storage battery have been developed. In particular, various methods for electrically determining the life of a sealed lead-acid battery in which the inside of the battery case cannot be seen have been proposed. For example,
The method of completely discharging the lead storage battery, confirming the capacity, and determining the life based on the capacity is a method capable of determining the life with the highest accuracy. However, this method cannot be used for determining the life of a lead storage battery mounted as a power supply of the apparatus, and is not practical. There is also a method of estimating the number of years of use of the battery. However, this method cannot take account of differences in battery use conditions, so that the accuracy is extremely poor. In addition, a method of discharging a lead storage battery with a relatively large current in a short time, measuring the open voltage or the rising voltage of the open voltage after the discharge is stopped, and determining the battery life from the value of the rising voltage is known. is there. There is also a method of measuring the internal impedance of the lead-acid battery and determining the life of the lead-acid battery from a change in the internal impedance.
The accuracy of the life judgment was not very good.

[0003]

In order to improve the determination accuracy, it is preferable to actually discharge the lead storage battery and measure the life. However, if the lead-acid battery is completely discharged or deeply discharged, it takes a long time to recharge the battery.In particular, when determining the life of a lead-acid battery mounted on an uninterruptible power supply, etc., a power failure occurs after the life is determined. Then, there was a problem that the device became inoperable.

Therefore, a method of periodically discharging a fully charged lead-acid battery with a constant current, measuring a terminal voltage at the end of discharge for each discharge, and judging the life of the lead-acid battery using the measured terminal voltage has been proposed. Developed (Japanese Patent Application No. 5-327746)
issue). In this life determination method, it is determined whether or not the terminal voltages at the end of each discharge become substantially the same, and if they are not substantially the same, it is determined that the lead storage battery has reached the end of its life.

Although this method can determine the life with a certain degree of accuracy, it is desired that the life can be determined with higher accuracy.

An object of the present invention is to provide a life determining method capable of determining the life of a lead storage battery with higher accuracy in a short time.

Another object of the present invention is to provide a life determining method which can determine the life of a lead storage battery with higher accuracy without discharging for a long time.

It is still another object of the present invention to provide a life judging method capable of improving the accuracy of judging the life due to a decrease in capacity in addition to the above objects.

[0009]

In each of the present inventions, in order to determine the life, a lead storage battery is periodically discharged at a high rate and a constant current for a short period of time, and the terminal voltage before and after the discharge is measured at each discharge. The life is determined using the terminal voltage thus obtained.

When a lead-acid battery is discharged, the rate of decrease in battery voltage increases in proportion to the magnitude of the discharge current, and increases in accordance with the state of deterioration (capacity degradation) of the lead-acid battery.
That is, the more the lead storage battery deteriorates, the faster the battery voltage decreases. In addition, when two lead-acid batteries whose lead-acid batteries have large capacities, such as a new lead-acid battery and a considerably deteriorated lead-acid battery, are discharged at the same amount of electricity and then charged at a constant current, the deterioration proceeds. As a result, the lead-acid battery having a smaller lead-acid battery capacity has a higher charging voltage (terminal voltage) faster. In the present invention, the deterioration state, that is, the life of the lead storage battery is determined by utilizing such properties of the lead storage battery.

First, it is determined whether or not the difference voltage between the terminal voltage before discharge and the terminal voltage after discharge measured at each discharge is smaller than a predetermined reference difference voltage. When there is the above, it is determined that the lead storage battery has reached the end of its battery life (first determination step). The magnitude of the difference voltage is proportional to the rate of decrease of the battery voltage. Therefore, by comparing this difference voltage with the reference difference voltage, the deterioration state of the lead storage battery can be determined.

In order to further improve the accuracy of the determination, when the difference voltage of each time is smaller than the reference difference voltage, the terminal voltage at the end of the discharge when the predetermined number of discharges is reached is not more than the predetermined reference voltage. It is determined whether or not it is set. When the terminal voltage at the end of the discharge when the predetermined number of discharges is reached is equal to or lower than the predetermined reference voltage, it is determined that the lead storage battery has reached the end of its battery life even if the difference voltage is smaller than the reference difference voltage. (A second determination step). The reason why such a method is adopted is that the difference voltage before and after the discharge may not be so large depending on the deterioration state of the battery. Even in such a case, if the deterioration of the lead storage battery proceeds, if the amount of discharge increases to some extent, the terminal voltage drops significantly. Therefore, if the terminal voltage at the end of discharge when the predetermined number of discharges is reached is compared with a predetermined reference voltage,
Even when the difference voltage before and after the discharge does not become so large, the life of the lead storage battery can be determined.

However, depending on the state of deterioration of the lead storage battery, even if the terminal voltage at the end of discharge when the predetermined number of discharges is reached is higher than the predetermined reference voltage, the life of the lead storage battery actually reaches its end. May be. In order to cope with such a case, when the terminal voltage at the end of discharge when the difference voltage of each time is smaller than the reference difference voltage and reaches the predetermined number of discharges is larger than the predetermined reference voltage, Measure the difference voltage between the terminal voltage at the end of the first discharge and the terminal voltage at the end of the discharge when the predetermined number of discharges is reached, and when this difference voltage is equal to or higher than the predetermined upper limit reference difference voltage, the lead-acid battery Is the battery life (third determination step). By doing so, the determination accuracy is further improved.

In order to further improve the accuracy of the determination as compared with the case where the first to third determination steps are performed, it is sufficient to look at the rate of increase of the charging voltage during charging. The higher the charging speed, that is, the higher the rising speed of the terminal voltage during charging, the closer the life of the lead storage battery is. To see this rate of rise, it is necessary to recharge the discharged lead storage battery. Therefore, the lead storage battery is charged by an amount of electricity 1 to 5 times the amount of electricity discharged by the above-mentioned predetermined number of discharges, and the difference voltage between the terminal voltage before charging and the terminal voltage after charging is set to a predetermined rising standard. See if there is more than the difference voltage.
When the difference voltage is equal to or higher than the predetermined reference voltage difference, it is determined that the battery has reached the end of the battery life assuming that the deterioration has progressed and the rising speed has increased (fourth determination step). In this way, the life of the lead storage battery can be determined with considerably high accuracy.

The cycle of discharge varies depending on the capacity and output voltage of the lead storage battery, but ranges from several seconds to several tens of seconds. The high rate constant current in the present invention is preferably 3 (A) or more.
The short discharge time is preferably 1 second or less.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. The method according to the invention comprises a charging circuit 1 and a discharging circuit 2 as schematically shown in FIG.
And a charge / discharge control means 3 for controlling the discharge circuit 2, a voltage measurement means 4 for measuring the terminal voltage of the lead-acid battery B, and storing the results measured by the voltage measurement means 4 and performing necessary calculations and life judgment. This can be performed by the arithmetic unit 5.

FIG. 2 shows an example of the state of the charge / discharge current of the lead storage battery during the life judgment. FIG. 3A shows the state shown in FIG. 2 scaled down for explanation. FIG. 3B shows the state of the battery voltage, that is, the terminal voltage of the lead-acid battery when the charge and discharge shown in FIG. 2 are performed with the scale shown in FIG. It is. FIG. 4 is a flowchart illustrating an algorithm for determining the life of software used when the arithmetic unit 5 is configured using a computer.

Hereinafter, each step of FIG. 4 will be described with reference to FIGS. First, in this example, step ST1
To start the life determination check.
At 3, the charging circuit 1 brings the lead storage battery B into a fully charged state.
Thereafter, in the present embodiment, the lead storage battery B is periodically discharged for a short period of time at a high rate constant current (check discharge) by the discharge circuit 2 at a constant short period in accordance with a command from the charge / discharge control means 3.

FIG. 2 shows a measurement pattern used in this example. A fully charged lead-acid battery having a terminal voltage of 13.5 V was subjected to a 15-second rest period, and each discharge time was set to 50 m.
s, the discharge pause time is 5 seconds, the discharge current is 6 C (A), and the check discharge is repeated 10 times. Steps ST4 to ST7 in FIG. 4 show the life determining steps (first to fourth determining steps) in the process of the check discharge. After step ST7, 5
After a pause of 20 seconds, the charging current of 0.35 C (A)
Perform check charging for 2 seconds. This charge amount is more than twice the above-mentioned discharge amount. Step ST8 in FIG. 4 corresponds to this charging.

According to the above-described check discharge / charge, the terminal voltage of the lead storage battery is assumed to change, for example, as shown in FIG. The voltage measuring means 4 measures the terminal voltage of the battery before and after the discharge at each discharge, and calculates the difference voltage (discharge voltage drop) between the measured terminal voltage before the discharge and the terminal voltage after the discharge. It is calculated by: Then, as shown in step ST4 of FIG. 4, it is determined whether or not this difference voltage is smaller than a predetermined reference difference voltage (2 V in this embodiment). It is determined that the lead storage battery has reached the battery life (capacity degradation) (first determination step).

Next, when the difference voltage of each time is smaller than the reference difference voltage, the process proceeds to step ST5 in FIG. 4, and the terminal voltage at the end of the discharge when the predetermined number of discharges (10 times in this example) is reached. (6C discharge potential) [10.72 in FIG.
V] is equal to or lower than a predetermined reference voltage (11 V in this example), and if it is equal to or lower than the reference voltage, it is determined that the lead storage battery has reached the end of its life (second determination step).

Next, when the difference voltage of each discharge is smaller than the reference difference voltage, the process proceeds to step ST6 in FIG. 4, and the terminal voltage at the end of the first discharge [11.24 V in FIG. 3B] is predetermined. The difference voltage (6C) from the terminal voltage at the end of discharge when the number of discharges (10 times) is reached [10.72 V in FIG.
The discharge potential difference is measured, and when the difference voltage is equal to or higher than a predetermined upper limit reference difference voltage (0.7 V in this example), it is determined that the lead storage battery has reached the end of its life (third determination step).

Further, when the difference voltage (6C discharge potential difference) in each discharge is smaller than the reference difference voltage in step ST6, the process proceeds to step ST7 in FIG. 4 to determine the terminal voltage at the end of the first discharge and the predetermined discharge. A difference voltage (6C discharge potential difference) from the terminal voltage at the end of the discharge when the number of times (10 times) is reached is measured, and this difference voltage is smaller than a predetermined lower limit reference difference voltage (0.5 V in this example). Determine whether or not. If the difference voltage is equal to or higher than a predetermined lower-limit reference difference voltage (0.5 V in this example), it is determined that the battery is a good battery. However, when the difference voltage is smaller than the predetermined lower-limit reference difference voltage (0.5 V), as shown in step ST8, the amount of electricity is 1 to 5 times the amount of electricity discharged by 10 times of discharge ( In this example, as shown in FIG. 2, the lead storage battery is charged at a charging current of 0.35 C (A) for 20 seconds. Then, the terminal voltage before charging [12.84 V in FIG. 3B] and the terminal voltage after charging [FIG.
It is determined that the lead-acid battery has reached the end of its life when the difference voltage (charging voltage rise value) from (14B in (B)) is equal to or higher than a predetermined rise reference difference voltage (4.5 V in this example) (fourth determination step). ).

In some cases where the short-circuit accident has occurred inside the lead-acid battery, the voltage rise value due to charging does not increase. However, in such a lead-acid battery, the above-described first to third determination steps at the time of discharging are performed. It is extracted to determine the deterioration of the capacity.

As described above, the method for judging the life of a lead-acid battery according to the present invention involves periodically discharging a fully charged lead-acid battery at a constant period in a short period of time at a constant current, and before and after discharging each time. The terminal life of the lead storage battery is determined by measuring the terminal voltage of the lead-acid storage battery by using the difference voltage between the measured terminal voltages before and after discharging. What is necessary is just to change the numerical value of the criterion.

Next, referring again to FIG. 4, the various steps of the life judgment described above will be summarized and explained.

First, as a first determination step of the life determination method of the present invention, as shown in step ST4 of FIG. 4, the terminal voltage before and after the discharge is measured at each discharge, and the terminal voltage before and after the discharge is measured. The voltage difference voltage is a predetermined reference difference voltage (2
V) When it is equal to or longer than the time, it is determined that the lead storage battery has reached the end of its life.

In the second determination step, a predetermined number of discharges (10 times) is performed as shown in step ST5 of FIG.
, The terminal voltage at the end of discharge when the voltage reaches the predetermined voltage, and when the measured terminal voltage is equal to or lower than a predetermined reference voltage (11 V), it is determined that the lead storage battery has reached the end of its life.

Next, in the third determination step, as shown in step ST6 of FIG. 4, the terminal voltage at the end of the first discharge and the discharge end at the predetermined number of discharges (10 times) are reached. The difference voltage from the terminal voltage at the time is measured, and when the difference voltage is equal to or more than a predetermined upper limit reference difference voltage (0.7 V), it is determined that the lead storage battery has reached the end of its life.

Further, in the fourth determination step, as shown in step ST7 of FIG. 4, the terminal voltage at the end of the first discharge and the terminal voltage at the end of the discharge when the predetermined number of discharges (10 times) are reached are reached. A difference voltage from the terminal voltage is measured, and it is determined whether or not the difference voltage is smaller than a predetermined lower-limit reference difference voltage (0.5 V). When the difference voltage is smaller than the lower limit difference voltage, as shown in step ST8 of FIG. 4, the lead storage battery is charged by 1 to 5 times the discharged amount of electricity. Then, when the voltage difference between the terminal voltage before charging and the terminal voltage after charging is equal to or higher than a predetermined rising reference difference voltage (4.5 V), it is determined that the lead storage battery has reached the end of its life.

Next, when the life determining method of the present invention is carried out, the characteristics of the magnitude of the discharge current of the lead storage battery on the change of the battery voltage will be described with reference to FIG. The curve shown by the solid line in the figure shows an example of the change characteristic of the battery voltage when each discharge time T of the short-time high-rate constant current discharge performed periodically is set to 50 ms, and the curve shown by the broken line shows each discharge time. When the time T is set to 100 ms, the curve shown by the dashed line indicates that each discharge time T is 2 ms.
9 shows an example of a change characteristic of the battery voltage when the time is set to 50 ms.

As can be seen from FIG. 5, the discharge current I is 2C
The magnitude of the change in the battery voltage does not have a fixed relationship below (A) and above 3C (A). When the discharge current is 3 C (A) or more, the voltage change during discharge is larger. In addition, the discharge capacity (Ah
Observing the effect of the magnitude of the discharge current 2C
The capacity discharged for 250 ms in (A) has a discharge current of 6 C
Although the capacity becomes larger than the capacity discharged for 50 ms in (A), the change in the battery voltage at the time of discharge becomes larger when the battery is discharged for 50 ms at 6C (A). Therefore, it can be seen that the magnitude of the discharge current greatly affects the change in the battery voltage. Therefore, in carrying out the above-described life determining method of the present invention, the current of the constant current discharge is preferably set to 3 C (A) or more. The discharge time for each discharge is preferably set to 1 second or less.

In the above-described embodiment, all the life determining methods of the present invention are executed. However, it goes without saying that each of the determining methods may be executed independently. That is, the life may be determined by executing only steps ST2 and ST4 in FIG. Further, the life may be determined by executing steps ST2, ST4 and step ST5. Further, the life may be determined by adding step ST6 to this. Further, in addition to the above steps, steps ST7 and ST8 may be executed to determine the life.

[0034]

According to the life determining method of the present invention, there is an advantage that the life of a lead storage battery can be determined with higher accuracy in a short time. Further, according to the life determination method of the present invention, there is an advantage that the life of the lead storage battery can be determined with higher accuracy without discharging for a long time.
Further, according to the present invention, in addition to the above advantages, it is possible to enhance the accuracy of determining the life due to a decrease in capacity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus for performing a method of the present invention.

FIG. 2 is a diagram illustrating an example of a state of a charge / discharge current of a lead storage battery during life determination according to the present invention.

3A is a scale-down view of the state shown in FIG. 2 for explanation, and FIG. 3B is a view showing FIG. 3A.
3 shows the state of the battery voltage of the lead storage battery, that is, the terminal voltage when the charge and discharge shown in FIG.

FIG. 4 is a flowchart illustrating an algorithm for determining the life used in the example of FIG. 1 that implements the method of the present invention.

FIG. 5 is a characteristic curve diagram showing an example of a characteristic that a magnitude of a discharge current of a lead storage battery affects a change in a battery voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charge circuit 2 Discharge circuit 3 Charge / discharge control means 4 Voltage measurement means 5 Arithmetic unit B Lead storage battery

Claims (6)

[Claims] 1. A fully charged state lead-acid battery is periodically discharged for a short period of time at a constant current at a constant rate, and the terminal voltage before and after discharging is measured at each discharge, and the terminal voltage measured is used to determine the life of the lead-acid battery. In the determination method, it is determined whether or not the difference voltage between the terminal voltage before discharge and the terminal voltage after discharge measured for each discharge is smaller than a predetermined reference difference voltage, and the difference voltage for each discharge is A method for determining the life of a lead storage battery, comprising determining that the lead storage battery has reached the end of its battery life when the voltage is equal to or higher than a reference difference voltage. 2. A fully charged lead-acid battery is periodically discharged for a short period of time at a constant current at a constant rate, and the terminal voltage before and after discharging is measured at each discharge, and the terminal voltage measured is used to determine the life of the lead-acid battery. In the determination method, it is determined whether or not the difference voltage between the terminal voltage before discharge and the terminal voltage after discharge measured for each discharge is smaller than a predetermined reference difference voltage, and the difference voltage for each discharge is When the terminal voltage at the end of discharge when the discharge voltage is smaller than a reference difference voltage and reaches a predetermined number of discharges becomes equal to or lower than a predetermined reference voltage, the lead storage battery is determined to have a life of the battery. Method for determining the life of lead-acid batteries. 3. A fully charged lead storage battery is periodically discharged for a short period of time at a constant current at a constant rate, and the terminal voltage before and after discharging is measured at each discharge, and the terminal voltage measured is used to determine the life of the lead storage battery. In the determination method, it is determined whether or not the difference voltage between the terminal voltage before discharge and the terminal voltage after discharge measured for each discharge is smaller than a predetermined reference difference voltage, and the difference voltage for each discharge is When the terminal voltage at the end of discharge when the voltage is smaller than the reference difference voltage and reaches the predetermined number of discharges is larger than the predetermined reference voltage, the terminal voltage at the end of the first discharge and the predetermined number of discharges are reached. Measuring the difference voltage from the terminal voltage at the end of the discharge at the time of the discharge, and determining that the lead storage battery has a battery life when the difference voltage is equal to or higher than a predetermined upper limit reference difference voltage. Life determination method. 4. A fully charged state lead-acid battery is periodically discharged at a high rate and a constant current for a short period of time, and terminal voltage before and after discharging is measured at each discharge, and the terminal voltage measured is used to determine the life of the lead-acid battery. In the determination method, it is determined whether or not the difference voltage between the terminal voltage before discharge and the terminal voltage after discharge measured for each discharge is smaller than a predetermined reference difference voltage, and the difference voltage for each discharge is When the terminal voltage at the end of discharge when the voltage is smaller than the reference difference voltage and reaches the predetermined number of discharges is larger than the predetermined reference voltage, the terminal voltage at the end of the first discharge and the predetermined number of discharges are reached. Measure the difference voltage from the terminal voltage at the end of the discharge at the time of, and determine whether the difference voltage is smaller than a predetermined lower limit reference difference voltage, the difference voltage is greater than a predetermined lower limit reference difference voltage Is smaller than the predetermined number of discharges. 1 of the discharged amount of electricity Te
The lead-acid battery is charged by an amount of up to five times the amount of electricity, and when the difference voltage between the terminal voltage before charging and the terminal voltage after charging is equal to or higher than a predetermined rising reference difference voltage, the lead-acid battery has a battery life. And determining the life of the lead storage battery. 5. A full-charge state lead-acid battery is periodically discharged at a constant current for a short period of time, and terminal voltage before and after discharging is measured at each discharge, and the terminal voltage measured is used to determine the life of the lead-acid battery. In the method, a first determination that the lead-acid battery has a battery life is provided when a difference voltage between a terminal voltage before discharge and a terminal voltage after discharge measured at each discharge is equal to or greater than a predetermined reference difference voltage. And when the difference voltage is smaller than the reference difference voltage in the first determination step, the terminal voltage at the end of discharge when a predetermined number of discharges is reached is measured, and the measured terminal voltage A second determination step of determining that the lead-acid battery has a battery life when is equal to or less than a predetermined reference voltage, and when the terminal voltage is higher than the predetermined reference voltage in the second determination step. Measure the difference voltage between the terminal voltage at the end of the first discharge and the terminal voltage at the end of the discharge when a predetermined number of discharges is reached, and when the difference voltage is equal to or higher than a predetermined upper limit reference difference voltage, the lead-acid battery A third determination step for determining that the battery voltage is equal to the battery life; and in the third determination step, when the difference voltage is smaller than the predetermined upper reference difference voltage, the difference voltage is a predetermined lower reference difference voltage. Is smaller than the predetermined number of discharges, the lead storage battery is charged by an amount of electricity 1 to 5 times the amount of electricity discharged, and the difference voltage between the terminal voltage before charging and the terminal voltage after charging is set in advance. Performing a fourth determination step of determining that the lead storage battery has a battery life when the voltage is equal to or greater than a predetermined rising reference difference voltage to determine whether the lead storage battery has a battery life. Lead-acid battery life Determination method. 6. The life determination of a lead-acid battery according to claim 1, wherein the short-time high-rate constant-current discharge is set to 3 C (A) or more and each discharge time is set to 1 second or less. Method.