JPH05166545A - Sealed lead-acid battery - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a sealed lead acid battery provided with a long-life capacity sensor that does not easily deteriorate even under high temperature and high humidity. [Constitution] In a sealed lead-acid battery that detects the pressure of water vapor equilibrating with the electrolyte as humidity and detects the charge / discharge state of the battery from this humidity, as a humidity sensor, a part of the surface of the optical fiber is made of microporous silica. As a humidity sensor, a humidity sensor that uses the correlation between the moisture adsorption amount of the humidity sensor and the transmitted light amount attenuation rate of the optical fiber is used.

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 provided with a sensor for detecting a charge / discharge state.

[0002]

2. Description of the Related Art As is well known, the charging / discharging state of a lead storage battery can be accurately determined by measuring the specific gravity or sulfuric acid concentration of the electrolyte. This is because the sulfuric acid in the electrolytic solution is stoichiometrically involved as an active material in the charge / discharge reaction, and the sulfuric acid is removed from the electrolytic solution in proportion to the amount of charge / discharge electricity, or into the electrolytic solution. Because it is released. Therefore, if the sulfuric acid concentration in the electrolytic solution can be detected, it is necessary to accurately know the charging / discharging state or the remaining capacity of the battery, that is, how much the battery is currently discharged or how much can be discharged later. You can

Further, if we can take a step further and develop a sensor that can take out the sulfuric acid concentration as an electric signal, the charging / discharging state of the battery can be automatically controlled by feeding this signal back to the charger. This can greatly contribute to maintenance-free power supply equipment.

On the other hand, in recent years, a lead-acid battery eliminates the electrolyte solution in a free state by using a mat-shaped separator made of ultrafine glass fiber to keep the electrolyte solution to a wet degree or by gelling the electrolyte solution. By using the so-called oxygen cycle principle, the problem of liquid leakage is solved by simultaneously, and at the same time, by depleting the electrolyte solution in this way, the oxygen gas generated in the positive electrode can easily permeate to the negative electrode and react with the negative electrode to be absorbed. By closing it, the problem of liquid loss was solved and almost completely maintenance free. as a result,
Lead acid batteries are gradually replacing the conventional liquid open type with a sealed type.

As described above, the sealed lead-acid battery has an excellent feature that it is maintenance-free, but on the other hand, since there is no free electrolyte in the battery, it has been used in the conventional liquid battery. A buoyancy type or optical type sulfuric acid concentration sensor that uses the relationship between sulfuric acid concentration and buoyancy or refractive index cannot be used, and users lose their ease by checking the charging status or remaining capacity. Still, there were problems such as the inspector being unable to have confidence in the survey results. Therefore, the development of a sensor that can detect the sulfuric acid concentration without the presence of a free electrolyte is strongly desired.

[0006] Against this background, an optical sulfuric acid concentration sensor has been proposed for a sealed lead acid battery (Japanese Patent Laid-Open No. Hei 10 (1999) -242242).
2-103870), this sensor has a small amount of free electrolyte solution, is not guaranteed to be reliably detected for a long time with a sealed lead acid battery that hardly exists, or has poor reproducibility of the indicated value. Has many problems.

As another proposal, the fact that the sulfuric acid concentration of a sulfuric acid aqueous solution and its saturated vapor pressure are in a correspondence relationship is used to detect the saturated vapor pressure as a relative humidity with a humidity sensor. There is something to ask [JE
CS, Vol.129, P.2409 (1982), JP-A-2-210771].

However, the humidity-sensing principle of the humidity sensor used for these is that an inorganic or organic thin film layer that reversibly absorbs and desorbs water is provided between two interdigitated comb-teeth electrodes, and the impedance of this thin film layer is set. Is used depending on the amount of adsorbed water. In order to withstand use in sulfuric acid, the moisture-sensitive part is protected by a water-repellent microporous membrane that is permeable to water vapor but impermeable to water, and is installed in the electrolytic solution or in the gas phase space. However, the humidity sensor based on this humidity-sensing principle has the drawback that the output characteristics change when used at high temperatures and high humidity.The cause of the deterioration is that the impedance characteristics of the thin film layer are such as alteration of the material itself and sulfuric acid. It is thought to be damaged by the attachment of the ionic substance.

[0009]

Means for Solving the Problems The sealed lead acid battery of the present invention comprises:
Saturated water vapor pressure of the electrolyte is the gas phase space in the battery or positive,
As a humidity sensor that detects humidity between the negative electrode plates, an optical fiber humidity sensor in which a part of the surface of the optical fiber is made porous, that is, when water is adsorbed on the surface of the made porous optical fiber, the amount of light passing through the optical fiber is attenuated. It is a storage battery that can detect a charging / discharging state by including a humidity sensor that utilizes the above.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the sealed lead acid battery of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a mounted state of a humidity sensor in the sealed lead acid battery of the present invention. 1 is a battery case of the battery, 2 is a cover of the battery case, 3 is a negative electrode plate, 4 is a negative electrode terminal, 5 is a mat-shaped glass separator, 6 is a positive electrode terminal, and 7 is a vapor phase space. Reference numeral 8 denotes an optical fiber, a light source 9 is arranged at one end of the optical fiber, and a part of the lid 2 is allowed to pass therethrough so that the vapor phase space 7 of the battery is
Is introduced to the outside of the battery, and the other end reaches the photoelectric conversion device 10.
Reference numeral 11 is a moisture sensitive portion formed by making a part of the surface of the optical fiber existing in the gas phase space porous.

FIG. 2 is a characteristic diagram showing the relationship between the relative humidity and the transmitted light attenuation factor of the optical fiber. FIG. 3 shows the relationship between sulfuric acid concentration and relative humidity. The correlation between the transmitted light attenuation rate and the sulfuric acid concentration can be obtained from the two figures, and the battery capacity can be detected from this relationship.

The light transmitted from the light source 9 passes through the inside of the optical fiber 8 and reaches the moisture sensitive portion 11. In the moisture sensitive portion 11, the light is refracted to the outside when the humidity is low, that is, when the adsorbed moisture is small. Without reflecting the amount of transmitted light inside the optical fiber, the amount of adsorbed water increases as the humidity increases,
A part of the amount of transmitted light is refracted to the outside at the interface and attenuated according to the amount of water. This amount of transmitted light is extracted at the other end of the optical fiber and input to the photoelectric conversion device 10. The amount of transmitted light is converted into humidity as an electric signal, and its value is immediately converted into sulfuric acid concentration and battery capacity.

Whereas the humidity-sensing principle of the conventional sensor utilizes the relationship between the chemical phenomenon called ionization and electrical conduction, this sensor absorbs and desorbs moisture and leaks transmitted light on the surface of microporous silica. The sealed lead-acid battery provided with the long-life capacity sensor that does not easily deteriorate even under high temperature and high humidity can be provided because it uses the physical phenomenon that is described above.

[0015]

The sealed lead-acid battery of the present invention utilizes a physical phenomenon using the change of light as the humidity sensor for detecting the capacity of the battery, which is the relationship between the relative humidity at the interface of the optical fiber and the attenuation factor of the transmitted light amount. Therefore, there is no deterioration and the sensor does not need to be replaced until the end of the battery life.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the arrangement of a humidity sensor in the sealed lead acid battery of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between relative humidity and attenuation rate of transmitted light amount of an optical fiber.

FIG. 3 is a diagram showing the relationship between sulfuric acid concentration of sulfuric acid aqueous solution and relative humidity.

[Explanation of symbols]

 1 Battery Case 2 Lid 7 Gas Phase Space 8 Optical Fiber 9 Light Source 10 Photoelectric Converter 11 Moisture Sensing Section

Claims (1)

[Claims] 1. A sealed lead-acid battery in which a vapor pressure in a battery or a humidity sensor provided between positive and negative electrode plates is used to detect water vapor pressure in equilibrium with an electrolytic solution as humidity and to detect a charge / discharge state of the battery from the humidity. Therefore, as a humidity sensor, a humidity sensitive part is constructed by using a part of the surface of the optical fiber as microporous silica, and the humidity utilizing the correlation between the moisture adsorption amount of the humidity sensitive part and the transmitted light amount attenuation rate of the optical fiber. A sealed lead-acid battery using a sensor.