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ITGlossary · Batteries
VRLA Battery
A sealed, valve-regulated lead-acid battery that never needs topping up with water and is used in most UPS systems.
Technical level:Intermediate
VRLA (valve-regulated lead-acid) batteries are sealed batteries in which the gases produced during charging recombine internally, so no water topping-up is needed. They come in two main technologies: AGM, the most common in UPS units, and gel. The usual size in small UPS units is a 12 V block.
Their service life depends mainly on temperature. Standard batteries are designed to operate at around 20–25 °C. For every 10 °C above that, their life is roughly halved, which is why they need replacing much sooner in rooms without air conditioning.
Maintenance-free does not mean check-free. Run a periodic battery test from the UPS and allow some ventilation, since a small amount of gas can be released if the battery is overcharged.
Related terms
- AGM BatteryA sealed VRLA lead-acid battery whose electrolyte is absorbed in glass-fibre mat separators.
- Flooded Lead-Acid BatteryA battery with liquid electrolyte and vent caps that needs regular checks and topping up with deionised water.
- Battery Service LifeThe years a battery keeps enough capacity, typically 3–5 years for VRLA at 20–25 °C, shortened by high temperatures.
- GEL BatteryA sealed lead-acid battery with its electrolyte in gel form, well suited to deep and repeated discharges.
- OPzS / OPzV Tubular BatteryStationary 2 V lead-acid cells with tubular positive plates, flooded (OPzS) or sealed with gel (OPzV), built for a very long life.
- Equalising ChargeA controlled charge at a higher than normal voltage that brings all cells of a lead-acid battery to the same state of charge.