JPH04312769A - Sealed-type lead secondary battery - Google Patents

Abstract

PURPOSE:To extend the life of a capacity sensor by detecting the concentration of an electrolyte by a humidity sensor using the relation between the steam concentration and the thermal conduction. CONSTITUTION:A humidity sensor 7 is attached spirally to a cover part 2 while a packing 11 being set between them and installed in a gas-phase space in the middle of a negative electrode 4 and a positive electrode 6 in the upper part of an electrolytic jar 1. To protect the humidity sensitive part of the sensor, the part is covered with a porous body 10 made of plastic. The sensor 7 detects the concentration of the electrolyte using the relation between the thermal conduction and the steam concentration calculated from the steam pressure in an equiliblium with an aquoeous sulfuric acid solution. By humidity detecting principle is changed from the chemical phenomenon to the physical phenomenon, a capacity sensor is prevented from deteriorating and can have a long life.

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 equipped with a sensor for detecting charging and discharging states.

0002

BACKGROUND OF THE INVENTION As is well known, the charging and discharging state of a lead-acid battery can be determined by measuring the sulfuric acid concentration in the electrolyte. This is because sulfuric acid is involved in the charging and discharging reactions of lead-acid batteries, and the change in the concentration of sulfuric acid (the amount of chemical reaction) changes in proportion to the change in battery capacity, that is, the amount of electricity charged and discharged. Therefore, if the sulfuric acid concentration can be detected, it is possible to accurately know how much the battery has been discharged or how much more can be discharged. Furthermore, if we want to automatically control the charging and discharging status of lead-acid batteries, it is essential to develop a sensor that can convert the sulfuric acid concentration in the electrolyte into an electrical signal and feed it back to the charger.

On the other hand, in recent years, lead-acid batteries are being replaced by sealed lead-acid batteries, which eliminate fluid leakage and depletion by eliminating a flowing electrolyte, and do not require maintenance such as water replenishment. Sealed lead-acid batteries have the excellent feature of requiring no maintenance, but they do not have a flowing electrolyte, so they can be replaced with sulfuric acid, which takes advantage of the buoyancy and changes in the refractive index of the electrolyte, which was used in conventional lead-acid batteries. The concentration sensor is no longer available.

[0004] Therefore, a method that does not require direct contact with the electrolytic solution was considered, and by utilizing the fact that the sulfuric acid concentration of a sulfuric acid aqueous solution and its saturated water vapor pressure correspond, the saturated water vapor pressure was detected with a humidity sensor. A method has been proposed in which the sulfuric acid concentration can be determined from the humidity value (JECS, vol.
．． 129, p. 2409-2412,'82). This system attempts to capture the saturated water vapor pressure by forming a closed system by covering the humidity sensor with a water-repellent microporous membrane and placing it in an electrolyte. Because it forms a system, the water vapor pressure reaches equilibrium quickly, and therefore the response is also fast. On the other hand, however, when used at high temperatures, sulfuric acid penetrates into the microporous membrane and adheres to the moisture-sensitive part of the sensor, changing its characteristics.

In order to solve this problem, there is a proposal to install a humidity sensor in the gas phase space at the top of the container so that it does not come into direct contact with the electrolyte, and to detect the saturated water vapor pressure in the gas phase space as humidity. Ganhei 2-238516).

However, conventionally used humidity sensors have a thin film layer that reversibly adsorbs moisture between two adjacent electrodes, and measure the electrical resistance that changes depending on the amount of moisture adsorbed. It was meant to be converted. However, the electrical resistance of this thin film has problems such as loss of reversibility and deterioration due to adhesion of ionic substances such as sulfuric acid.

[0007]

[Means for Solving the Problems] The sealed lead-acid battery capacity sensor of the present invention is a humidity sensor that utilizes the relationship between water vapor concentration and heat conduction, which is provided in the gas phase space of a battery container to maintain water vapor pressure in equilibrium with an aqueous sulfuric acid solution. The electrolyte concentration is detected by In other words, by changing the humidity detection principle from the conventional chemical phenomenon of ionization to the physical phenomenon of heat conduction, the present invention provides a long-life sealed lead-acid battery capacity sensor that eliminates conventional deterioration.

[0008]

[Embodiment] Next, the principle of the above humidity sensor will be explained with reference to the drawings. Figure 1 is a measurement circuit diagram of a humidity sensor using a thermistor. Electric current is applied from power source E, and Joule heat generates approximately 2
Two thermistors R1 and R2 self-heated to 00℃
is installed on the side of the bridge circuit, R1 is installed in a metal case with a hole so that it can be exposed to the outside air, and R
2 are enclosed together with dry air in a holeless metal case of the same shape and size. R3 and R4 are the resistors that form the bridge, R5 is the resistor that limits the current, and R
6 is a resistor for taking out the output voltage from the bridge circuit. When R1 is placed in dry air, output terminal A
, B, balance the bridge so that no output voltage is generated between them. Next, when R1 is exposed to the atmosphere whose humidity is to be measured, R1 is further cooled due to the difference in thermal conductivity between the atmosphere and dry air, and an output voltage is generated between A and B. Figure 2 shows the relationship between humidity and output voltage. This output voltage value is converted into humidity to obtain the sulfuric acid concentration and to detect the charge/discharge state of the battery.

FIG. 3 is a schematic cross-sectional view showing a state in which a humidity sensor is attached to the battery of the present invention. 1 is the battery case, 2
is the lid of the battery container, 3 is the negative electrode plate, 4 is the negative terminal, 5 is the matte glass separator, 6 is the positive terminal, 7 is the body of the humidity sensor, and the packing 11 is inserted into the opening provided in the lid of the battery container. It has a structure that screws on through it. Reference numeral 9 denotes a gas phase space within the battery case, in which the sensor is placed covered with a porous plastic body 10 so that the moisture sensing part does not come into direct contact with the electrode plate group or the electrolyte. 8 is a conducting wire for taking out the output of the sensor.

0010

Effects of the Invention: The sealed lead-acid battery of the present invention utilizes the physical phenomenon of the relationship between water vapor concentration and heat conduction as a humidity sensor, so it responds quickly, has no hysteresis during humidification/dehumidification cycles, and is resistant to deterioration. There is no need to replace the sensor until the end of its life.

[Brief explanation of the drawing]

FIG. 1 is a measurement circuit diagram of a humidity sensor using a thermistor.

FIG. 2 is a diagram showing the relationship between relative humidity and output voltage.

FIG. 3 is a schematic cross-sectional view showing the arrangement of humidity sensors in the sealed lead battery of the present invention.

[Explanation of symbols]

1 Battery case 2 Lid 7 Humidity sensor 8 Sensor output lead wire

Claims (1)

[Claims] Claim 1: A sealed lead-acid battery that detects the humidity that is in equilibrium with the electrolyte concentration using a humidity sensor provided in the gas phase space above the battery case, and detects the charging/discharging state from the humidity value. A sealed lead-acid battery characterized by being equipped with a humidity sensor that uses the relationship between water vapor concentration and heat conduction to detect.