Valve-regulated lead-acid (VRLA) batteries with gelled electrolyte appeared as a niche market during the 1950s. During the 1970s, when glass-fiber felts became available as a further method to immobilize the electrol. Lead-acid batteries represent the oldest rechargeable battery system and despite their r. The lead-acid battery represents a rather complex electrochemical system of primary and secondary reactions. The discharging–charging reactions are based on the conversio. The VRLA battery is based on the same materials and electrode reactions as the conventional version. The main difference is the immobilization of the electrolyte and the internal oxyg. When the battery is overcharged, in principle, the same secondary reactions occur in the vented and the VRLA system, but their weighting is quite different.••. Discharge performance of VRLA batteries corresponds to that of the vented version, since the same reactions occur in both types. In general, discharge performance is degraded at lowe.
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Why should lead-acid batteries be valve regulated?
Thus, the strong position of lead-acid batteries in this field will be improved by the valve-regulated design, and they will remain in widespread use in the future. Furthermore, the VRLA design opens applications for lead-acid batteries where acid stratification had been an obstacle for the vented design.
The valve-regulated version of this battery system, the VRLA battery, is a development parallel to the sealed nickel/cadmium battery that appeared on the market shortly after World War II and largely replaced lead-acid batteries in portable applications at that time.
This version - the valve-regulated lead-acid (VRLA) battery - requires no replenishment of the water content of the electrolyte solution, does not spill liquids, and can be used in any desired orientation.
Lead–acid batteries are employed in a wide variety of different tasks, each with its own distinctive duty cycle. In internal-combustion engine vehicles, the battery provides a quick pulse of high-current for starting and a lower, sustained current for other purposes; the battery remains at a high state-of-charge for most of the time.
What happens when a lead acid battery is discharged?
The process is the same for all types of lead-acid batteries: flooded, gel and AGM. The actions that take place during discharge are the reverse of those that occur during charge. The discharged material on both plates is lead sulfate (PbSO4). When a charging voltage is applied, charge flow occurs.
The unavoidable hydrogen evolution would cause a continuous increase of the internal pressure until the cell would be destroyed. For this reason, the lead-acid battery cannot be sealed, but has to have a valve that opens from time to time and allows the escape of hydrogen, even under normal operational conditions.