Sealing mechanism of VRLA battery

The difficulty of sealing lead-acid batteries is the electrolysis of water during charging. When the charging reaches a certain voltage (generally above 2.30V/cell), oxygen is released on the positive electrode of the battery, and hydrogen is released on the negative electrode. On the one hand, the released gas brings out the acid mist to pollute the environment, on the other hand, the water content in the electrolyte decreases, so it is necessary to add water for maintenance at intervals.

Valve-regulated lead-acid battery is a product developed to overcome these shortcomings. Its product features are:
(1) Multi-element high-quality grid alloy is used to improve the overpotential of gas release. That is, ordinary battery grid alloy releases gas when it is above 2.30V/cell (25°C). After using high-quality multi-component alloys, the gas is released when the temperature is above 2.35V/monomer (25°C), which relatively reduces the amount of gas released.

(2) Let the negative electrode have excess capacity, that is, 10% more capacity than the positive electrode. In the later stage of charging, the oxygen released by the positive electrode contacts the negative electrode, reacts, and regenerates water, that is, O2+2Pb→2PbO+2H2SO4→H2O+2PbSO4, so that the negative electrode is in an undercharged state due to the action of oxygen, so no hydrogen is produced. The oxygen of the positive electrode is absorbed by the lead of the negative electrode, and then it is further converted into water, which is the so-called cathode absorption.

(3) In order to allow the oxygen released by the positive electrode to flow to the negative electrode as soon as possible, a new type of ultra-fine glass fiber separator that is different from the microporous rubber separator used in ordinary lead-acid batteries must be used. The porosity is increased from 50% of the rubber separator to more than 90%, so that the oxygen can easily flow to the negative electrode and be converted into water. In addition, the ultra-fine glass fiber separator has the function of adsorbing the sulfuric acid electrolyte, so even if the battery is toppled, the electrolyte will not overflow.

(4) The sealed valve-controlled acid filter structure is adopted, so that the acid mist cannot escape, so as to achieve the purpose of safety and environmental protection.

In the above-mentioned cathode absorption process, since the generated water cannot overflow under the condition of sealing, the valve-regulated sealed lead-acid battery can be exempted from supplementary water maintenance, which is also the origin of the valve-regulated sealed lead-acid battery called dimension-free battery.

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