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ITGlossary · Batteries
AGM Battery
A sealed VRLA lead-acid battery whose electrolyte is absorbed in glass-fibre mat separators.
Technical level:Basic
In an AGM battery the acid does not move freely but is held in thin sheets of glass fibre between the plates. The battery does not spill, needs no topping up with water and can be mounted in more positions than a flooded battery.
It has a low internal resistance and delivers high current for a few minutes, which is why it is the most common type in office UPS units and rack-mount UPS units. It is, however, sensitive to heat: above 20–25 °C its life shortens noticeably.
A common mistake is charging it with a flooded-battery profile or at too high a voltage, which dries it out and makes it swell. Always use the charging voltages given by the manufacturer.
Related terms
- VRLA BatteryA sealed, valve-regulated lead-acid battery that never needs topping up with water and is used in most UPS systems.
- GEL BatteryA sealed lead-acid battery with its electrolyte in gel form, well suited to deep and repeated discharges.
- Noise (Electrical)Unwanted high-frequency disturbances on the supply voltage, e.g. from motors or power supplies, which UPS systems and line conditioners filter out.
- Eurobat Design Life ClassesA classification of sealed lead-acid batteries by their design life on float charge at 20 °C.
- Flooded Lead-Acid BatteryA battery with liquid electrolyte and vent caps that needs regular checks and topping up with deionised water.
- 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.