What are VRLA lead-acid batteries with AGM technology?

In VRLA (Valve Regulated Lead Acid) batteries the case is sealed and has a safety valve that opens only if internal pressure rises too high. In AGM (Absorbent Glass Mat) technology the electrolyte is absorbed in glass-fibre separators, so there is no free liquid. The gases produced during charging largely recombine inside the battery, which is why no water top-up is needed.

These features make them practically maintenance-free, suitable for indoor spaces with normal ventilation and able to deliver high currents for short periods, exactly what a UPS needs. UPS batteries are usually 12 V, with capacity expressed in Ah.

There are variants for different uses. StandbyGlossary · UPS technologyOffline (Standby) UPSA UPS that leaves the load on the mains and switches to battery only when the mains fails, with a short transfer time; the simplest and cheapest topology. batteries are designed to stay permanently charged and be discharged rarely, as in a UPS. Cyclic (deep-cycle) batteries better withstand frequent deep discharges, for example in off-grid solar systems.

Practical tip: heat and deep discharges shorten their life more than anything else. Do not leave them discharged, recharge them as soon as possible after use and, while in storage, every few months.