Valve Regulated Lead Acid batteries (VRLA) are designed to be used in two types of applications, Float and Cycle service. In Cycle service mode, the batteries are continuously being discharged throughout the course of a day and then charged overnight (i.e. fork lift). In Float service, the batteries are continuously trickle charged to maintain full charge status and is discharged in short usage cycles or infrequent deep cycles.
When used in Cycle mode, the estimated battery life is around 200 complete discharges. In Float mode, the service life is estimated to be 3 to 4 years. A UPS operates in float mode.
A battery system must be inspected and tested at regular intervals. Faults can occur long before a battery's expected service life expires. Experience shows that this holds true for all types of battery systems. The following are recommended test/inspections that should be performed at least every six months.
1. Battery charger setting. Faulty charging shortens a battery's service life.
2. Corrosion may occur at terminal posts, internal connections, etc.
3. Ambient temperatures may need to be corrected.
4. Leakage may occur.
UPS systems proactively performs a quick self-test discharge test every 14 days (by default) to detect abnormally weak battery packs and it will display this anomaly on the display and any any accessories.
As mentioned before, UPS systems operate under Float battery mode (i.e. idle). VRLA batteries are specially designed to operate in this mode. The UPS will assist you in determining the state of the battery, but this does not substitute for preventive maintenance checks. You should at least check the temperature of the battery pack and give a visual inspection for physical failures (bloating/leaking).