[[TitleIndustry]]

Valve-controlled sealed lead-acid battery (VRLA) and pure lead battery

Date:Oct 26, 2019

1. Fixed type valve-regulated sealed lead-acid batteries (abbreviated as VRLA) can be divided into two categories:

One type is a lean liquid AGM battery (referred to as AGM battery) which uses ultrafine glass fiber (AGM) as a separator to adsorb battery sulfuric acid electrolyte technology;

The other is the use of silicone gel to fix the sulfuric acid electrolyte rich liquid colloidal battery (referred to as GEL colloidal battery)

1.1 AGM battery

The AGM battery consists of a positive electrode plate, a negative electrode plate, an adsorbable glass fiber (AGM) separator, a sulfuric acid electrolyte, a safety valve, and a battery case. In an AGM battery, the electrolyte is adsorbed in a glass wool separator, and there is no free flowing electrolyte in the battery. The oxygen generated during the charging process of the battery reaches the negative electrode through the pore passage in the AGM separator to realize the water recombination cycle (as shown in the figure below). AGM batteries are lean liquid designs and have a higher density of electrolytes than flooded batteries.

Technical characteristics of AGM battery:

First, it has better charging efficiency;

Second, the cluster is tightly assembled and has a small internal resistance, which is suitable for large current discharge;

Third, due to the lean liquid design, the gas compounding efficiency is higher (>98%), so no acid mist is revealed;

However, AGM batteries are not suitable for small currents and long-term discharge.

1.2, GEL battery

There are two kinds of colloids:

One is a colloidal battery in which the positive electrode of the battery has a tubular structure and the negative electrode has a grid structure, that is, a tubular colloid (internationally known as an Opzv battery);

The other is a grid structure with positive and negative plates, and a colloidal battery with a grooved phenolic resin or a PVC or microporous separator between the positive and negative electrodes, commonly known as a plate colloid.

The colloidal battery with positive tube structure is more suitable for 2V series batteries due to higher cost, and its stability and life is better than that of plate type colloid series batteries.

The GEL colloidal battery consists of a positive electrode plate, a negative electrode plate, a phenolic resin or a PVC or microporous separator, a colloidal electrolyte, a safety valve, and a battery casing. In GEL gel batteries, the electrolyte is fixed by gel (ie GEL); the separator of GEL gel battery is used to isolate the positive and negative plates of the battery and prevent lead dendrite short circuit. The oxygen generated during the charging process of the GEL colloidal battery reaches the negative electrode through the crack passage of the colloid to realize the water recombination cycle.

The sealing principle of GEL colloidal battery is similar to that of AGM battery technology. In the early stage of use, GEL colloidal battery has less cracking of colloid and low oxygen compounding efficiency. Therefore, the safety valve is easy to open and has more acid mist precipitation. With the use of the battery, the crack increases and the composite efficiency of oxygen is gradually increased.

Features of GEL gel battery:

First, the overcharge resistance is good;

Second, the cycle has a long service life;

Third, small current and long-term discharge performance are good;

However, in the early stage of use, the GEL colloidal battery is less suitable for fast charge and high rate discharge due to the lower complex efficiency of oxygen and more acid mist discharge.

2. pure lead battery

The pure lead battery is a relatively advanced lead-acid battery. It uses ultra-pure lead to make the grid (99.999%), which makes the plate more resistant to corrosion. At the same time, the inner plate of the pure lead battery can be ultra-thin (about 1mm). In the same size housing, more plates can be installed, which greatly increases the reaction area inside the battery, thereby improving the chemical reaction efficiency of the battery and reducing the internal resistance of the battery.

Since the positive and negative plates of pure lead batteries are very "soft", it is very difficult to manufacture the plates. In addition, the superposition and assembly of the plates are difficult to implement, so the early pure lead batteries adopt a winding structure. Design, the capacity is only 100AH. With the rapid development of intelligent manufacturing technology, the electrode manufacturing and assembly technology of pure lead batteries has been effectively solved, and the monomer capacity of pure lead batteries has reached 600AH.

Features of pure lead battery:

First, it is more suitable for harsh environments and has a wide temperature range (-40°C to +80°C);

Second, due to the ultra-thin plate of the pure lead battery, the internal resistance is small, the chemical reaction efficiency is high, and thus the energy density is higher;

Third, the pure lead battery has a fast charging acceptance capability, and the battery capacity of charging for 3 hours is more than 90% (generally GEL colloidal battery takes 8-10 hours);

Fourth, the pure lead battery adopts ultra-thin multi-pole plate design, which has a discharge capacity of 40% to 2 hours in the urban rail transit industry, which is about 40% higher than that of the conventional battery.

In addition, since the pure lead battery has low internal impurities and low self-discharge, it has a long storage life and requires no recharging time of up to two years (generally GEL colloidal battery is six months).

The excellent characteristics of pure lead batteries have gradually attracted the attention of the domestic urban rail transit industry, and some cities have begun to promote their use.

3, true and false GEL gel battery

At present, most of the UPS in the domestic urban rail transit industry still use GEL colloidal batteries from well-known foreign brands. Due to the high price of GEL colloidal batteries and the distribution through agents, some unscrupulous dealers shoddy and fake the city rail transit. Security operations pose a huge hidden danger.

In the true sense, GEL colloidal batteries generally use phenolic resin or PVC or microporous separators. Under vacuum, the colloidal substances are fully filled and diffused into the trenches of the separators or in the microporous separators to form an effective GEL colloidal battery. Partition.

For colloidal batteries using AGM separators, since the colloidal material has a diameter of 14-17 μm and the pores of the AGM separator are 2-4 μm, the colloidal substance cannot penetrate into the AGM separator, so only a layer of colloid is left outside the AGM separator. Substance, not a gel battery in the true sense.

The China Electrotechnical Association Lead Acid Battery Professional Committee issued a clear statement in 2014: The "colloidal battery" using AGM diaphragm does not have the performance characteristics of a gel battery. In the test report and certificate of the Tell laboratory, there is a strict distinction between the types of colloidal batteries: for the true GEL colloidal battery, the YD/T1360 standard is followed, the report is labeled as “colloidal battery”; for the AGM separator battery, Following the YD/T799 standard, the report is labeled "AGM + Colloidal Lead Acid Battery".

At the same time, due to the difference in internal structural materials, the same capacity AGM battery and GEL colloidal battery, the possibility of the same size is small, otherwise it may be a false GEL colloidal battery formed by AGM battery through subsequent filling.

In addition, in the Tyre certification, if the "key components and materials" separator column shows "microporous separator" or "PVC separator", it is generally a true GEL gel battery.

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