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Chapter 12 Helpful information
discharge and subsequent recharge reduces its relative capacity by a small percentage. The
length of the discharge cycle determines the reduction in battery capacity.
Lead-acid chemistry, like others used in rechargeable batteries, can only undergo a maximum
number of discharge/recharge cycles before the chemistry is depleted. Once the chemistry is
depleted, the cells fail and the battery must be replaced.
4. Maintenance
Battery service and maintenance are critical to UPS reliability. A gradual decrease in battery
life can be monitored and evaluated through voltage checks, load testing or monitoring.
Periodic preventive maintenance extends battery string life by preventing loose connections,
removing corrosion and identifying bad batteries before they can affect the rest of the string.
Even though sealed batteries are sometimes referred to as maintenance-free, they still require
scheduled maintenance and service. Maintenance-free simply refers to the fact that they don't
require fluid.
Without regular maintenance, your UPS battery may experience heat-generating resistance at
the terminals, improper loading, reduced protection and premature failure. With proper
maintenance, the end of battery life can be accurately estimated and replacements scheduled
without unexpected downtime or loss of backup power.
Battery life: design life vs. actual life
Determining battery life can be a tricky business. It's often promoted based on design life, defined as
how long the battery can be expected to perform under ideal conditions.
Estimating actual battery life relies on taking into consideration the four factors that can impact affect
it.
What can go wrong with batteries?
Condition
Plate separation
Grid corrosion
Internal short circuit Heat (plates expand causing shorts), separator failure, handling and
External short circuit Human error (shorting terminals) and leaks
6U Rack or Tower UPS RT8kVA and RT11kVA IUOMG
Cause
Repeated cycling (charging and discharging), damage during handling and
shipping, and overcharging
Normal aging, operating in an acidic environment and high temperatures
shipping, and grid corrosion
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