JPH02210771A - Sealed type lead storage battery - Google Patents

Abstract

PURPOSE:To make the condition of a battery clear at any time by arranging a humidity sensor covered with a porous water-impermeable fluorine resin film positioning at the end anode plate or in the lining direction of the electrode plates. CONSTITUTION:Solvent density sensors 7 and 9 in the water solution which are formed by covering and packing a humidity sensor 1 with a three layer membrane composed of a porous water-impermeable fluorine resin film 2, a steam selective permeable layer 3, and an acid vapor absorption layer 4 mainly of calcium carbonate is soaked in a sulfric acid electrolyte of a lead storage battery. And the variation of the specific gravity of the electrolyte following the charge and discharge of the battery is caught as the variation of the relative humidity. As a result, by finding the relation of the specific gravity of the sulfic acid electrolyte and the relative humidity beforehand, the specific gravity of the sulfric acid electrolyte, that is, the condition of the battery, can be found from the relative humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sealed lead-acid battery, and particularly to a sealed J9 storage battery in which the specific gravity of an electrolyte can be measured using a humidity sensor.

Conventional technology and its problems A common method for indirectly estimating the state of charge and life of a lead-acid battery is to measure the specific gravity of the battery's electrolyte.

However, it is a closed type! 9 In the case of a storage battery, it is cut off from the outside air due to its nature, and the electrode plates are impregnated with electrolyte and retained, or
In addition, because it is in a semi-solid state, it is impossible to use the float type hydrometer or optical hydrometer used in liquid lead-acid batteries, and there is no suitable method for measuring the specific gravity of the electrolyte.

In addition, as a special method, West German Patent No.
No. 54207 (1973).

That is, this method attempts to detect the concentration of the sulfuric acid aqueous solution by measuring the water vapor pressure in this space, since the water vapor pressure in the upper space, which is in vapor-liquid equilibrium with the sulfuric acid aqueous solution, changes depending on the sulfuric acid concentration.

Furthermore, by developing this proposal, we directly immersed a humidity sensor coated with a porous polypropylene membrane in an aqueous sulfuric acid solution, and determined the partial pressure of water vapor diffusing through the pores of the porous polypropylene membrane in uJ. This is proposed by Beininger et al. in Journal of Electrochemistry Society, Vol. 129, p. 19 (1982).

However, in the case of the West German patent, there was a problem that even if the sulfuric acid concentration changed, it took time for the water vapor pressure of the sulfuric acid aqueous solution and the water vapor pressure of the space to reach equilibrium, and the response speed was slow. In addition, in the case of the method by Peininger et al., the porous polypropylene is a material problem and its water repellency is insufficient, so not only water vapor but also the sulfuric acid aqueous solution itself passes through the membrane and reaches the humidity sensing part of the humidity sensor. and the humidity is
Not only could they not be used to measure accurately, but they were also chemically attacked and had an extremely short sensor lifespan.

Knowing the specific gravity of the electrolyte in a lead-acid battery can be used as a method for checking the state of charge and indirectly estimating the service life as described above. By measuring the specific gravity, various problems in lead-acid batteries can be detected, such as when the cathode plate active material oxidizes and reacts with the dilute sulfuric acid electrolyte, resulting in a decrease in the specific gravity, or when the electrolyte specific gravity decreases due to an internal short circuit in the electrode plate group. Since it was possible to measure the condition, a lead-acid battery equipped with a hydrometer was required.

Means for Solving the Problems The present inventors have already developed a humidity sensor coated with a porous non-water permeable fluororesin membrane or a membrane in which a water vapor selective permeation layer or an acid vapor absorption layer is formed on the humidity sensor. The present invention, which proposes a long-life sensor for measuring solute concentration in an aqueous solution, provides a lead-acid battery in which the battery status can be checked at any time by using the above-mentioned sensor. That is, the present invention provides a humidity sensor coated with a porous non-water permeable fluororesin that selectively permeates only water vapor, or a membrane in which a water vapor selectively permeable layer or an acid vapor absorbing layer is formed on the membrane. The sensor is attached so as to be immersed in the sulfuric acid electrolyte of a lead-acid battery, and the battery condition can be determined by detecting changes in the specific gravity of the electrolyte as changes in relative humidity occur as the battery is charged and discharged. If the relationship between the specific gravity of the sulfuric acid aqueous solution and the relative humidity is determined in advance, the specific gravity of the sulfuric acid aqueous solution, that is, the battery condition can be determined from the relative humidity.

In addition, although the sensor is generally placed away from the electrode group, since the charging and discharging of the HN battery occurs within the electrode group, changes in the specific gravity of the electrolyte will occur even if the sensor is placed away from the electrode group. In the present invention, the sensor faces and contacts the cathode plate at the end of the electrode plate group or the direction in which the electrode plates are arranged, so that it can quickly respond to charging and discharging of the battery. . The sensor for solute concentration in an aqueous solution used in the present invention can be called a sulfuric acid specific gravity sensor because it determines the specific gravity of an aqueous sulfuric acid solution.

Example: An example in which a sulfuric acid specific gravity sensor is incorporated into a 200 ampere-hour sealed lead-acid battery will be specifically described below. The cross-sectional structure of the specific gravity sensor used in the present invention is shown in FIG. 1B.

First, the thickness of the water repellent layer is O, tnn+, and the porosity is 75%.
One side of the porous polytetrafluoroethylene membrane is coated with an alcohol solution of perfluorocarbon sulfonic acid resin to form a water vapor selective permeation layer. next,
A mixture of calcium carbonate powder with a particle size of 20 μm or less and a fluorine-modified urethane resin is applied onto this water vapor selectively permeable layer to form an acid vapor absorption layer 9. Thus, a three-layer membrane is obtained. Next, with this film, a humidity sensor of a type in which a moisture-sensitive film made of a polymer electrolyte is formed on an alumina substrate is wrapped in a bag shape to produce a specific gravity sensor. In FIGS. 1A and B, a humidity sensor 1 is packaged and coated with a three-layer membrane composed of a porous water-impermeable fluororesin membrane 2, a water vapor selectively permeable layer 3, and an acid vapor absorption layer 4 mainly composed of calcium carbonate. has been done. FIG. 2 shows a cross-sectional structure in which the sensor is incorporated into a sealed lead-acid battery. The inside of the battery case 5 is completely sealed by a safety valve 6 attached to the cover 5' and the lid, and the specific gravity sensor 7 is placed in contact with the outside of the end cathode plate 8 of the storage battery. In order to compare the responsiveness depending on the position of the sensor, a specific gravity sensor 9 was separately placed above the electrode plate group. Reference numerals 10 and 11 are specific gravity display sections that convert the relative humidity signal detected by the specific gravity sensor 7.9 into sulfuric acid specific gravity and display it.

Using this battery, we first determined the electrolyte specific gravity converted from the output value of the sensor during 10 ampere discharge, and compared this with the electrolyte specific gravity value theoretically estimated from the discharge, as shown in Figure 3. Compared to the theoretical transition 21 of the electrolyte specific gravity, the transition 22 of the sensor 7 in contact with the electrode plate corresponded fairly well, although there was a delay in response. In comparison, the response of the sensor 9, which was placed above and away from the electrode group, was delayed as shown at 23 in FIG. From this, it can be seen that it is most preferable to arrange the specific gravity sensor in contact with the electrode plate group.

In addition, the sensor was placed facing the direction in which the electrode plates were lined up and in contact with the separator, but it showed almost the same response as when it was in contact with the end cathode plate.

In addition, to confirm the durability of this sensor when attached to a lead-acid battery, we conducted a temperature-accelerated life test by placing the sensor in contact with the outside of the electrode plate group. The results are shown in FIG.

The temperature was 80″C, 170°C, and 60°C.

From this result, the lifespan extrapolated to 25°C was estimated to be approximately 7 years, indicating that the sensor according to the present invention can be put to practical use.6 Effects of the Invention As described above, according to the present invention In sealed lead-acid batteries, it is possible to quickly and continuously measure the specific gravity, and it is also possible to measure the specific gravity of the electrolyte in sealed lead-acid batteries, which was previously impossible. It is possible to determine the capacity and lifespan of storage batteries, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1A shows 'IfJ' of the sulfuric acid specific gravity sensor used in the present invention.
Figure 1B is a cross-sectional diagram of the structure, Figure 2 is a diagram of how the sensor is attached to the battery, Figure 3 is a diagram showing the change in sensor specific gravity during discharge, and Figure 4 is a diagram showing the temperature and sensor. FIG. 3 is a diagram showing the relationship between service life. 1... Humidity sensor 2... Porous non-water permeable fluororesin membrane, 3... Water vapor selective permeation layer, 4... Acid vapor absorption layer, 5... Battery container, 7.9... Specific gravity sensor 8.
・End #e electrode plate, 10, 11... Specific gravity display section 1 time 2 5 4 s teaching in the sun (h) 4 years old

Claims (1)

[Claims] 1. A humidity sensor covered with a porous, water-impermeable fluororesin film for detecting changes in the specific gravity of the electrolyte in the storage battery is arranged at the end of the electrode plate group or in the direction in which the electrode plates are lined up. A sealed lead-acid battery.