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Information about UPS and Sealed Lead
Acid Batteries
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| There are four
major factors that affect UPS battery life (both sealed
and flooded cells):
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Ambient Temperature
The rated output
capacity of a battery is based on an ambient temperature
of 25C (77F). It is important to realize that any
variation from this operating temperature can alter the
performance of the battery, and shorten its expected
life. High temperature reduces the battery life greatly.
A good rule of
thumb when determining battery life in relation to
temperature is that for every 8.3C (15F) average annual
temperature above 25C (77F), the life of the battery is
reduced by 50 percent. |
UPS
Battery Capacity
UPS battery
capacity is determined by the battery's ability to
convert chemical energy into electrical current at a
specified rate for a specified amount of time. |
UPS
Battery Chemistry
No UPS battery
will last forever-- even one that experiences minimal
use. This is because UPS batteries are electro-chemical
devices whose ability to store and deliver power slowly
decreases over time. So, even if you follow all the
guidelines for proper storage temperature and
maintenance, you still must replace them after a certain
period of time. |
Cycling
During a utility
power failure (severe brownout or blackout conditions),
the UPS operates on battery power. Once utility power is
restored, the battery is recharged for future use. This
entire "loop" is considered a discharge cycle.
At
installation the battery is at 100 percent of rated
capacity. Each discharge and subsequent recharge reduces
the relative capacity of the battery by a small
percentage. The length of the discharge cycle will
determine the reduction in battery capacity.
The "loaf of bread"
analogy is most often used to illustrate the
relationship between cycling and battery life. A loaf of
bread can either be cut into many thin slices or a few
thicker slices. Similarly, a UPS battery can provide
power over a large number of short cycles, or fewer
cycles of longer duration. |
Maintenance and Service
The final factor to
consider is the maintenance and service of the batteries
and the UPS. The gradual decrease in battery life can be
monitored and evaluated through voltage checks, load
testing and retorquing connections, as part of a
periodic maintenance program.
Without regular
maintenance and service checks, your UPS battery may
experience:
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Heat-generating resistance at the terminals
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Improper loading
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Reduced protection
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Premature failure
With proper
maintenance and service, the end of battery life can be
estimated and replacements scheduled without any
interruption or loss of backup power.
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UPS
Battery FAQs
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| What is the
"end of useful life"?
The IEEE defines
"end of useful life" for a UPS battery as being the
point when it can no longer supply 80 percent of its
rated capacity in ampere-hours. (Because the
relationship between amp-hours and load protection time
is not linear, a 20% reduction in capacity results in a
much greater reduction in protection time. For example,
a UPS battery that supports a full load for 15 minutes
when new, will support the same load for only about 8
minutes when it reaches its defined "end of life"). When
your battery reaches 80 percent of its rated capacity,
the aging process accelerates and the battery should be
replaced. |
Which
factors contribute most to end-of-life for UPS
batteries?
In North America,
Western Europe and similar countries, positive grid
corrosion has been the most common end-of-life factor
for UPS batteries. This is a result of the normal aging
process due to UPS battery chemistry (regardless of
battery cycling) and involves the gradual breakdown of
the inner wires of the positive grid within the battery.
In other areas,
cycling is often the major contributing factor, due to
very unpredictable utility power.
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How do I make
sure that my UPS batteries are maintained and serviced
properly?
With proper
maintenance, battery life can be predicted and
replacements scheduled without interrupting your
operations. These are IEEE and OEM recommendations for
general maintenance:
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Comprehensive maintenance programs with a monthly inspection, and
more rigorous quarterly and annual checks.
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Retorquing all connections, as required
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Load testing
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Cleaning the battery area, as required
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What about my smaller
UPS? Does this information apply only to the larger
models?
Yes, this
information applies to all UPS batteries. It is also
important to understand the fact that battery warranty
does not necessarily equal battery life and the
estimated range for battery life is five to eight years.
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| Are Maintenance
Free batteries maintenance free?
Though sealed
batteries are sometimes called "maintenance free," they
still require scheduled maintenance and service. The
term "maintenance free" refers to the fact that they do
not require fluid. Preventive maintenance is the key to
maximizing your UPS battery service life.
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| What about the
disposal of batteries?
Never toss the UPS batteries in the
trash!
Recycle them.
Please recycle
all batteries.
You may ship your
used batteries to:
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4upsbattery.com
Attn: Recycle
642 E. 39th Place, Ste 5
Yuma, AZ 85365 |
We will recycle them for you or you may take them
to a local recycler. Call
800-255-5545 for additional assistance.
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Dependable
performance and long service life depend upon correct charging.
Faulty procedures or inadequate charging equipment results in
decreased battery life and/or unsatisfactory performance and may
void the warranty.
To charge an SLA battery, a DC
voltage higher than the open circuit of 2.15 volts per cell is
applied to the terminals of the battery. Any of the conventional
charging techniques may be used, but to obtain maximum service life
and capacity, along with acceptable recharge time, constant
voltage-current limited charging is recommended.
During constant voltage or
taper charging, the battery's current acceptance decrease as voltage
and state of charge increase. The battery is fully charged once the
current stabilizes at a low level for a few hours.
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Cycle Applications:
Limit initial current to 0.20C (C is the nominal A.H. capacity of
the battery). Charge until battery voltage (under charge) reaches
2.45 per cell at 68 degrees F (20 deg.C). Hold at 2.45 volts per
cell until current drops to approximately 0.01C ampere. Battery is
fully charged under these conditions, and charge to "float" voltage.
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"Float" of Stand-By Service:
Hold battery across constant voltage source of 2.25 to 2.30 volts
per cell continuously. When held at this voltage, the battery will
seek its own current level and maintain itself in a fully charged
condition.
Continuous over or
undercharging is the single worst enemy of a lead acid battery.
Caution should be exercised to insure that the charger is
disconnected after cycle charging, or that the float voltage is set
correctly.
Because there is a chance of
off-gassing hydrogen and oxygen if the battery is overcharged, it is
important to provide adequate air circulation. (Never charge or
discharge a battery in a hermetically sealed enclosure.)
Batteries should not be stored
in a discharged state or in a hot location. If a battery has
been discharged for some time it may not readily take a charge.
Due to the self-discharge
characteristics of this type of battery, it is imperative that they
be charged after 3-4 months of storage, otherwise permanent loss of
capacity might occur as a result of sulfation. To prolong shelf life
without charging, store batteries at 50 degrees F (10 deg. C) or
less.
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Don't see your
questions? call 800-255-5545 or
email
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