The difficulty in sealing lead-acid batteries is the electrolysis of water during charging. When 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 and pollutes the environment. On the other hand, the moisture in the electrolyte is reduced, and it is necessary to add water for maintenance at intervals. The valve-regulated lead-acid battery is a product developed to overcome these shortcomings. Its product features are:
(1) The use of multiple high-quality grid alloys improves the overpotential of gas release. That is, the ordinary battery grid alloy releases gas when it is above 2.30V/cell (25°C). After using high-quality multi-element alloys, gas will be released when the temperature is above 2.35V/single (25°C), thereby reducing 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 from the positive electrode contacts the negative electrode and reacts to regenerate water, namely O2+2Pb→2PbO+2H2SO4→H2O+2PbSO4, so that the negative electrode is in an undercharged state due to oxygen, so no hydrogen is produced. The oxygen in the positive electrode is absorbed by the negative lead, and the process is further transformed into water, which is the so-called cathode absorption.
(3) In order to allow the oxygen released from the positive electrode to circulate to the negative electrode as soon as possible, a new type of ultrafine 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 oxygen can easily circulate to the negative electrode and be reconstituted 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 overturned, there is no electrolyte overflow.
(4) The sealed valve-controlled acid filter structure is adopted to prevent acid mist from escaping, achieving the purpose of safety and environmental protection.
In the above cathode absorption process, since the water produced cannot overflow under the sealed condition, the valve-regulated sealed lead-acid battery can be exempted from water supplement maintenance. This is also the origin of the valve-regulated sealed lead-acid battery called the non-dimensional battery. However, the meaning of maintenance-free does not mean that no maintenance is done. On the contrary, in order to improve the service life of VRLA batteries, there are many maintenance tasks waiting for us to do. The correct method of use can only be explored in the process. come out.