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ITGlossary · Batteries
Battery Service Life
The years a battery keeps enough capacity, typically 3–5 years for VRLA at 20–25 °C, shortened by high temperatures.
Technical level:Basic
In practice, a UPS battery is considered to have reached the end of its life when its capacity drops to about 80% of the rated value. From that point on, runtime falls quickly and the risk that it will not last through an outage grows.
The “design life” quoted by manufacturers assumes ideal conditions; real service life depends on temperature, the number of deep discharges and the quality of charging. As a rule of thumb, every 8–10 °C above 25 °C roughly halves the life of a lead-acid battery.
A common mistake is installing the UPS in a closed cabinet or next to a heat source. Also schedule a periodic runtime test so you can spot a worn battery in time.
Related terms
- VRLA BatteryA sealed, valve-regulated lead-acid battery that never needs topping up with water and is used in most UPS systems.
- Cycle LifeThe number of charge and discharge cycles a battery withstands until its capacity falls, usually, to 80% of the original.
- Fast ChargingA charging method that restores battery capacity quickly without damage by controlling current, voltage and temperature.
- Lithium-ion BatteryA rechargeable lithium-ion battery with high energy density, long life and faster charging than lead-acid batteries.
- AGM BatteryA sealed VRLA lead-acid battery whose electrolyte is absorbed in glass-fibre mat separators.
- Ampere-hour (Ah)The unit of battery capacity, showing how much current a battery can deliver and for how long, e.g. 9 Ah means 0.45 A for 20 hours.