JPH056782A - Method of detecting deteriorated state of sealed lead-acid battery - Google Patents

Abstract

(57) [Summary] [Purpose] To detect the deterioration state of a sealed lead-acid battery without increasing the number of battery components. [Structure] A square wave alternating current is supplied from a square wave signal generator 1 to a battery 3 whose deterioration state is to be detected, and a voltage response component generated between both electrodes of the battery 3 is detected. Using the computer 6, the voltage response component is approximated to an expression of the sum of a term proportional to time, a term proportional to a square root of time, and a constant. The deterioration state of the battery is evaluated by the magnitude of the coefficient of the term proportional to the square root of time.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a method of measuring the specific gravity of an electrolyte has been generally used as a method for detecting the deterioration state of a stationary lead-acid battery. However, the cathode absorption type sealed lead acid battery is a completely sealed type, and therefore the specific gravity of the electrolyte cannot be directly measured. Therefore, a method of installing the specific gravity measuring electrode in the battery case, a method of detecting the physical deformation amount of the anode plate, and the like have been proposed.

[0003]

However, in the former method, since the extra electrode is installed, the number of parts and the manufacturing cost are increased. Further, the latter method requires special parts for detecting the elongation of the anode plate, which also leads to an increase in the number of parts and an increase in manufacturing cost.

It is an object of the present invention to propose a detection method for detecting the deterioration state of a sealed lead-acid battery without using a detection means for increasing the number of constituent parts of the battery.

[0005]

In order to solve the above-mentioned problems, a method for detecting a deteriorated state of a sealed lead-acid battery according to the present invention is a sealed lead for detecting a deteriorated state of a square wave AC current having a constant amplitude. The voltage response component V (t) in either the charging direction or the discharging direction generated between both electrodes of the battery is detected, and the voltage response component V (t) is proportional to time (A · t). ) And a term proportional to the square root of time (B ·
t ^1/2 ) and a constant (V 0), the expression [V (t) = V 0 +
A · t + B · t ^1/2 ], and the deterioration state of the battery is evaluated by the magnitude of the coefficient B of the term proportional to the square root of the time.

[0006]

In the detection method of the present invention, the current in the charging direction flows through the battery during the half cycle of the square wave alternating current, and the current in the discharging direction flows during the negative half cycle. In general, an overvoltage generated at a pole when a current is applied to an electrode system of a lead storage battery is represented by a sum of polarizations such as polarization due to charge transfer, polarization due to charging of electric double layer capacity, and concentration polarization of electrolyte ions. .. Although it is considered that the electrode of the lead acid battery is porous, the voltage response component is also complicated, but since the concentration polarization due to the diffusion of the electrolytic solution is proportional to the square root of time (t ^1/2 ), the method of the present invention. It is considered that the coefficient (B) evaluated in (1) includes information on the diffusion of the electrolytic solution into the active material. Compared to a normal battery, the deteriorated battery has less active material that reacts effectively, and the active material is converted to non-reducing lead sulfate, so the diffusion of the active material that reacts effectively and the electrolyte solution deteriorate, and the square root of time The inventor has found that the coefficient of the term proportional to is likely to increase. Therefore, in the method of the present invention, the deterioration state of the sealed lead-acid battery is evaluated by evaluating the magnitude of this coefficient.

In theory, it is considered that the deterioration state can be detected from the change of the coefficient A of the term proportional to time, but when actually measured, the coefficient A almost changes. No trend was seen.

[0008]

Embodiments of the detection method of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of an apparatus for carrying out the detection method of the present invention. The square wave output of a square wave signal generator 1 is passed through a voltage-current converter 2 to a lead-acid battery 3 to be detected. .. Then, the voltage response component generated during the period when the current in the charging direction flows between both electrodes of the battery 3 is amplified by the amplifier 4,
It is input to the A / D converter 5, converted into a digital signal stepwise at regular time intervals, and calculated and calculated by the computer 6.
To analyze.

The measuring method for applying a square wave signal to detect the voltage response component used in this embodiment is similar to the step method used when analyzing the electrode system in the electrochemical measuring method. .. The difference between the known step method and the measurement method used in this embodiment is basically the signal conduction time. In the step method, a pulse signal having a period on the order of μsec is applied, whereas in this embodiment, a signal on the order of sec is used for measurement. As will be described later, the period of the concretely applied square wave signal is 10 seconds. The reason why the square wave signal is used as the applied signal is that the approximation with the mathematical formula is easier when the constant amplitude is applied, and the accuracy of the approximation is higher. Note that when a sine wave is applied, the voltage response component also becomes a sine wave, making approximation impossible. The frequency of the square wave signal is not particularly limited as long as it can be approximated by the equation of the voltage response component. In the case of analysis using the computer 6, the voltage response component V (t) is divided into a term (A · t) proportional to time,
A term (Bt ^1/2 ) proportional to the square root of time and a constant (V
It is approximated by the following equation with the sum of 0).

V (t) = V 0 + A · t + B · t ^1/2 (1) In the calculation / analysis by the computer 6, the measured value of the voltage response component is used by using the Marquardt method, which is a type of nonlinear least squares method. Then, the values of the coefficients A, B and V0 are calculated so that the error of the calculated value by the equation (1) is minimized.

As a concrete example, 2V, 200Ah
The results of a high temperature accelerated life test using the sealed lead acid battery of No. 1 will be described. The current applied to the battery is ±
FIG. 2 shows the change in the voltage response component generated between both electrodes of the battery during one cycle with a low frequency square wave current of 2 A and a cycle of 10 seconds. The solid line waveform D in the same figure is for the battery at the beginning of performance, and the broken line waveform F is for the battery after its life. Further, the half cycle period of time 0 to 5 seconds is a period in which a current in the charging direction is applied to the battery, and the half cycle period of time 5 to 10 seconds is a period in which a current in the discharging direction is applied. Then, in the example, the above-described calculation / analysis was performed based on the voltage response component in the period in which the current in the charging direction was passed, and each component of the above formula (1) was approximately calculated. FIG. 3 shows the change in the coefficient B of the term proportional to the square root of the time obtained by this calculation in the voltage response component during the test period, and the curve C in the figure shows the change in the discharge capacity of the battery during the test period. It is shown.

As can be seen from the figure, the coefficient B has a difference of about four times between the initial battery life and the end of life, and the deterioration state can be sufficiently detected.

In order to obtain the change in the coefficient B shown in FIG. 3, the voltage response component generated when a current in the charging direction is applied to the battery is used in this embodiment. Of course, the voltage response component that occurs sometimes may be used.

Further, in this embodiment, the period of the square wave current supplied to the battery is set to 10 seconds. However, if the period is such that the voltage response component can be approximated to the three components as described above, it is appropriate. It is possible to use one having a cycle of.

[0016]

As described above, according to the method for detecting the deterioration state of a sealed lead-acid battery according to the present invention, a square wave AC current is passed through the battery to detect the voltage response component generated between both electrodes of the battery. Then, the voltage response component is approximated by a term proportional to time, a term proportional to the square root of time, and a constant, and the deterioration state of the battery is determined based on the magnitude of the coefficient of the term proportional to the square root of time. Since the evaluation is made, the deterioration state of the sealed lead-acid battery can be satisfactorily detected without increasing the number of constituent parts of the battery for detecting the deterioration state or increasing the manufacturing cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration example of an apparatus for carrying out a detection method of the present invention.

FIG. 2 is a characteristic curve diagram showing changes in voltage response components of a normal battery and a battery that has reached the end of its life.

FIG. 3 is a curve diagram showing changes in a discharge capacity of a battery in a life test and a coefficient of a term proportional to a square root of time in a voltage response component.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Square wave signal generator, 2 ... Voltage-current converter, 3 ... Lead-acid battery to be detected, 5 ... A / D converter, 6 ... Computer.

Claims (1)

Claims: What is claimed is: 1. A square-wave alternating current having a constant amplitude is applied to a sealed lead-acid battery whose deterioration state is to be detected, and a voltage response in either the charging direction or the discharging direction generated between both electrodes of the battery. A component is detected, and the voltage response component is approximated to a formula of a sum of a term proportional to time, a term proportional to a parallel root of time, and a constant,
A method for detecting a deteriorated state of a sealed lead-acid battery, characterized in that a deteriorated state of the battery is evaluated based on a magnitude of a coefficient of a term proportional to a square root of the time.