All UPS batteries have a limited service life, regardless of how or where the UPS is deployed. Although determining battery life can be tricky, there are four primary factors that contribute to a battery’s overall lifespan.

Ambient temperature

Because the rated capacity of a battery is based on an ambient temperature of 25°C (77°F), any variation can affect performance and reduce battery life. For every 8.3°C (15°F) average annual temperature above 25°C (77°F), the life of the battery is reduced by 50%.

Battery chemistry

UPS batteries are electro-chemical devices whose ability to store and deliver power slowly decreases over time. Even if all guidelines for storage, maintenance, and usage are followed, batteries will still require replacement after a certain period of time.


After a UPS operates on battery power during a power failure, the battery is recharged for future use, which is called the discharge cycle. At installation, the battery is at 100% of its rated capacity, but each discharge and subsequent recharge slightly reduces the relative capacity of the battery. Once the chemistry is depleted, the cells fail and the battery must be replaced.


For larger UPS models, service and maintenance of batteries are critical to the reliability of the UPS. Periodic preventive maintenance not only extends battery string life by preventing loose connections and removing corrosion, but it can help identify ailing batteries before they fail. Even though sealed batteries are sometimes referred to as “maintenance-free,” they still require scheduled service, as “maintenance-free” refers only to the fact that they do not require replacement fluid.