Difference between German Sunlight Battery (Colloid) and Lead-acid Battery

ABSTRACT: Glass fiber (AGM) batteries belong to valve-regulated lead acid (VLRA) batteries, which are the earliest invented and widely used batteries. Due to the design and process improvement of gel (GEL) German solar battery, its overall performance has surpassed that of AGM battery.

Key words: AGM (lead-acid) battery; GEL (colloid) German solar cell; design life; performance-price ratio
Lead-acid batteries were first reported by G. Plante in 1859. Since then, lead-acid batteries have been widely used in automobiles, industrial backup power supply and other applications. Despite the continuous development of some new types of batteries, lead-acid batteries are still the dominant species, and have a history of more than 140 years. With the development of valve-regulated lead-acid battery technology, oxygen generated by the positive electrode absorbs and reduces on the surface of the negative active material during the overcharging process, thus reducing the loss of water and realizing the function of water-free (i.e. maintenance-free).

From 1950s to 1960s, sealed lead-acid batteries used anhydrous silica gel (GEL) as electrolyte. Until the 1970s, sealed lead-acid batteries consisted of glass fiber (AGM) separators and sulfuric acid liquids as electrolytes. Although the cost is low, the overall performance of AGM batteries is inferior to that of GEL batteries.

IMPROVED DESIGN AND TECHNOLOGY OF 1 AGM BATTERY

Panasonic collected more than 1000 AGM faulty batteries, dissected and analyzed them, and obtained many available data. Finally, the main factors causing battery deterioration were positive plate, electrolyte, safety valve and its sealing. It was confirmed that the corrosion of positive grid plate was the biggest factor causing battery life deterioration. The main reason is that when the battery is floated at a constant voltage for a long time, the charging current will oxidize and corrode the positive grid plate, which will reduce the area of the conductive part or the extension of the positive grid plate and reduce the tightness of the reactant (contact area), resulting in the reduction of the effective reactant, thus reducing the discharge capacity until the end of life. In view of this main factor, further detailed analysis, test and improvement are made. The experimental results show that improving the corrosion of the positive grid plate can greatly improve the deterioration of the battery. It is clear that the key to prolong the life of the battery is to improve the corrosion resistance of the positive grid plate.

(1) Improving the Corrosion of Positive Grid

In order to improve the corrosion resistance of positive grid alloys for negative absorption sealed lead-acid batteries, alloys containing arsenic, silver, tin and calcium have been studied many times. Considering the "dehydration" characteristics, environmental protection, cost factors, production efficiency and other factors, lead-calcium-tin alloy was finally chosen.

In order to reduce corrosion and prolong service life, the solid solution limit and range of lead-calcium-tin ternary alloys were fully evaluated. Panasonic made batteries with different tin content positive grid plates, sampled in the process of accelerating service life experiment, analyzed and measured the corrosion amount and extension degree of positive grid plates.
With the increase of tin content, the corrosion of the positive grid is reduced and the extension of the positive grid is controlled. Figure 2 shows the relationship between corrosion and elongation of various alloys.

Even if the corrosion amount is the same, the alloy grids with more tin content are not easy to extend.
Corrosion profile of positive grid plate section at different tin alloy content.

Intergranular corrosion is easy to occur when tin content is low, and intergranular corrosion can be controlled by tin content, even if the same amount of corrosion is not easy to cause grid extension.
In summary, increasing tin content in grid alloy has obvious effect on corrosion resistance, so the alloy with tin content of more than 1.6% is used in ultra-long life battery series.

(2) Design of Ultrafine Glass Fiber Diaphragm

In order to control the diffusion of oxygen, the diameter and density of fiberglass diaphragm were studied. In order to evaluate the gas diffusion velocity in the baffle, the time of 300 CC air penetrating the baffle thickness was measured according to the JISP8117 (Guriey Meathod) standard while adjusting the water content of the baffle.

The air permeability resistance of various baffles is shown in Fig. 4.

Diaphragm A has the highest air permeability resistance and can control floating charging current. Especially in the area where charging current is high at high temperature (that is, the area where oxygen is most generated), the effect of diaphragm A is obvious. Therefore, diaphragm A is adopted. But this specification is formulated on the premise of airtight reaction, water retention and no elastic effect.

(3) Design of Improving the Density of Anode Active Substances

Control of floating charge current not only has an important impact on battery life characteristics, especially in large capacity batteries and unreasonably high charging voltage, it is an important technical measure to control the thermal runaway phenomenon of batteries at high temperature.
In the process of floating charging, the internal reactions of the battery are as follows:

Positive pole: oxidation occurs, oxygen diffuses through the barrier
H_2O(1/2)O_2+2H++ 2e
Negative Electrode: Reduction Reaction
Pb+(1/2)O 2_PbO+H 2SO 4>PbSO 4+H 2
PbSO4+2H++ 2e_Pb+H2SO4

In order to control the floating charge current, besides the partition which controls the oxygen diffusion rate (i.e. the fine glass fiber partition), the formulation of the negative electrode material for reduction reaction is discussed in depth. The relationship between the density of active substance and charging current at constant voltage is shown in Fig. 6.


The floating charge current can be controlled by increasing the density of the active material of the negative electrode, but the formula of the density of the active material of the negative electrode approaching 4.5g/cm3 should be selected without degrading the discharge performance.

Characteristics of 2 Ultra Long Life AGM Batteries

Super Life LC-QA series battery specifications developed by Panasonic Company are shown in Table 1 and compared with LC-X series battery of normal life.