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Chapter 12 Helpful information
UPS Battery Technical Brief
Introduction
Battery in an Uninterruptible Power System (UPS) is the most vulnerable part of the system. In
fact, battery failure is a leading cause of load loss. Knowing how to maintain and manage your
UPS batteries will extend their life and save you time and potential trouble in the future.
Four factors that affect battery life
Batteries have limited life, usually showing a slow degradation of capacity until they reach 80
percent of their initial rating, followed by a comparatively rapid failure. Regardless of how or
where a UPS is deployed, and what size it is, there are four primary factors that affect battery
life: ambient temperature, battery chemistry, cycling and service.
1. Ambient temperature
The rated capacity of a battery is based on an ambient temperature of 25 °C (77 °F). It's
important to realize that any variation from this operating temperature can alter the battery's
performance and shorten its expected life. To help determine battery life in relation to
temperature, remember that for every 8.3 °C (15 °F) average annual temperature above 25 °C
(77 °F), the life of the battery is reduced by 50 percent.
2. Battery chemistry
UPS batteries are electrochemical devices whose ability to store and deliver power slowly
decreases over time. Even if you follow all the guidelines for proper storage, usage and
maintenance, batteries still require replacement after a certain period of time.
3. Cycling
During a utility power failure, a UPS operates on battery power. Once utility power is restored,
or a switch to generator power is complete, the battery is recharged for future use. This is
called a discharge cycle. At installation, the battery is at 100 percent of rated capacity. Each
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6U Rack or Tower UPS RT8kVA and RT11kVA IUOMG
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