Fixed battery refers to the battery used in relatively fixed occasions. Currently, there are flooded and valve-regulated batteries. This type of battery is mostly used for emergency use and is mostly a backup power source. However, the application fields are wide, and they cannot all be classified into batteries for backup power. Such batteries are widely used in communications, electricity, postal services, banks, hospitals, enterprises, public facilities, etc. Different occasions may require slightly different requirements.
There are two typical types of stationary batteries. One is a single battery with a rated voltage of 2V and a capacity of 50~3000 A·h. Because of its higher size, it is usually called a high type. The other is composed of 6 single batteries in series, with a rated voltage of 12 V and a capacity of 50~300 A·h. Because of its short size, it is also called a short fixed battery. Because the specifications and sizes of batteries can be determined by both the supply and demand sides in addition to the national standard, there are many batteries of various sizes.
The characteristics of this type of battery are that the battery is large in size, high in capacity, long in life, suitable for floating charging, and produces less acid mist and flammable gas.
The stationary vented battery is a stationary flooded battery, which has been widely used before the appearance of the stationary valve-regulated battery, and now there are some applications, which were called stationary acid-proof batteries in the past. This kind of battery has a long life, and the longest reported use is 20 years, but the battery is of a liquid-rich structure, and when overcharged, it will generate oxygen, oxygen and acid mist. Some liquid hole plugs for fixed acid-proof batteries are specially designed. The plug is equipped with a catalyst for hydrogen oxidation, and hydrogen and oxygen can be partially combined. Some bolts are designed with explosion-proof devices to prevent sparks from entering the battery and cause an explosion. Despite these devices, the acid mist from the gas evolution is still corrosive to the equipment room, and anti-corrosion measures and exhaust air are required to eliminate the existing unsafe hidden dangers.
The fixed exhaust type battery can replenish water in time through the liquid hole plug, so the anti-overcharge performance is better. The alloys of the grid are mostly made of medium brocade and low brocade alloys, that is, lead brocade alloys with a brocade content of about 3% and below. The charging acceptance performance and service life are good.
The fixed valve-regulated battery is characterized in that the battery adopts an adsorption-type separator, and the electrolyte is adsorbed into the separator, and there is no free electrolyte; the battery exhaust is controlled by the one-way valve. When the pressure in the battery is greater than the specified value, the one-way valve is opened to release the pressure, and then the one-way valve is closed again; when the battery is overcharged, the positive plate will generate oxygen, and the oxygen will reach the negative electrode through the separator, and combine with the lead of the negative electrode to realize the recombination of oxygen, so there is little loss of water, and the battery can be used for a long time without adding water.
For fixed valve-regulated batteries, the grid alloys are all lead-calcium alloys, 0.8%~1.5% tin is added to the positive grid, and 0.2%~0.3% tin is added to the negative grid. This alloy increases the overpotential of hydrogen evolution by 200mV, and greatly reduces the loss of water compared with lead alloy, which is the basis for realizing valve-controlled sealing.
The valve-regulated battery has less acid mist, hydrogen and oxygen evolution, and no need to add water for maintenance. This is the biggest advantage, but it also has many shortcomings. The fixed valve-regulated lead-acid battery is finally pressure-limited and sealed by the recombination of oxygen on the negative electrode. The combination of oxygen and lead is an exothermic reaction. The more oxygen, the greater the reaction heat, the higher the temperature of the battery, and the greater the current when the battery is charged at a constant voltage. The higher the current, the more oxygen is produced at the positive electrode, and the more heat is generated by the negative electrode compounding. Cycling like this, the battery is quickly damaged by high temperatures, often referred to as thermal runaway of a valve-regulated battery. Therefore, the use requirements of valve-regulated batteries are much higher than those of fixed vented batteries, and the service life is shorter than that of fixed acid-proof batteries.