VRLA — valve regulated lead acid — is the sealed evolution of the flooded battery. Oxygen generated at the positive plate recombines inside the cell instead of venting, so the electrolyte never needs topping up and the battery can live in an office cabinet, a telecom shelter or under a solar inverter. A pressure-relief valve is the only path to the outside, and it opens only under abuse conditions. XD Battery’s production range is built on this discipline: the deep-cycling series, the gel series and the general lead acid series are all sealed VRLA designs.
Within VRLA there are two electrolyte strategies, and choosing between them is the main engineering decision on this page. AGM (absorbed glass mat) holds the electrolyte in a fiberglass separator — lower internal resistance, strong high-rate performance, the natural UPS battery. Gel immobilises the electrolyte in silica — slower to deliver peak current, but more tolerant of deep discharge, heat and imperfect charging, which is why gel dominates solar cycling duty. XD manufactures both: the documented range includes a combined Gel/AGM deep-cycle model and dedicated gel lines.
Where VRLA is specified
- UPS and standby power — float service, high-rate discharge
- Telecom backup — 48V strings of 12V blocks or 2V cells
- Solar storage — daily cycling in off-grid and hybrid systems
- Emergency systems — lighting, alarms, medical and rail backup
Is a VRLA battery really maintenance free?
It needs no watering and no electrolyte checks — that is the maintenance it removes. Terminals should still be inspected and float voltage kept in specification; our maintenance-free page explains the honest scope of the term.
AGM or gel for a UPS?
AGM for high-rate standby duty; gel where the same battery also cycles or lives in heat. Our gel vs AGM guide compares them in full.