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In today's "always on, always available" world where businesses can't
stop and downtime is measured in dollars, American Power Conversion
(APC) provides protection against some of the leading causes of
downtime, data loss and hardware damage: power problems and
temperature. As a global leader in network-critical physical
infrastructure (NCPI) solutions, APC sets the standard in its industry
for quality, innovation and support. Its comprehensive solutions, which
are designed for both home and corporate environments, improve the
manageability, availability and performance of sensitive electronic,
network, communications and industrial equipment of all sizes.
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Phone: (+98) 21 - |
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88457636, 88457669 |
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88456763, 88455539 |
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88455760, 88412189 |
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Fax: (+98) 21 - 88415327 |
Email address:
info {at} pima-co {dot} com |
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UPS Battery Life and Maintenance |
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The battery is the least reliable component of a UPS. Whereas most components give relatively little
trouble over the lifetime of the UPS, the batteries need to be replaced every two to five years. The battery is also
one of the most expensive components of the UPS and typically accounts for 25% or more of the initial purchase cost.
Consequently, for a UPS with a service life of 10 years, and a battery life of 2 years, the total cost of battery
replacement over the UPS lifetime will be equal to, or exceed, the original purchase cost.
Overall UPS system reliability is more dependents upon the DC component of the system than any other element. Batteries
will remain the DC component of choice for most UPS systems for many years to come.
The performance and service life of batteries can be maximized by observing the following guidelines.
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There are four major factors that affect UPS battery life:
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Ambient Temperature
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The following graph shows how a battery's life is reduced with increasing
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. A good rule of thumb when determining the 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.
The battery capacity of a UPS battery is determined by the UPS Battery Chemistry,
i.e., by the battery's ability to convert chemical energy into electrical current at a specified rate for a
specified amount of time. The graph in shows how a battery's life is reduced with increasing temperature.
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UPS Battery Chemistry and Number of Discharge Cycles
No UPS battery will last forever, but a UPS that utilizes advanced charging technology and battery
monitoring will get far more mileage from the same battery! However, all UPS batteries are electro-chemical devices
whose ability to store and deliver power slowly decreases over time. Even if you follow the guidelines for proper
storage temperature and maintenance you will still need to replace them after a certain period of time.
The number of discharge cycles and the depth of the discharge cycles also affects battery life as shown in the following
figure.
 Batteries are designed for a specific number of discharge cycles (typically 200) and as they approach this number,
their capacity gradually reduces. At 80% capacity, a battery is said to be at its end-of-life. Many UPS manufacturers
guarantee an autonomy time at the battery's end-of-life, but not all do. Check with the manufacturer to see if the
published battery autonomy times are guaranteed after a specific number of discharges.
The number of discharge cycles is related to the quality of the mains supply. The more times the mains fail, the more
times the UPS will use the battery, and the more times the battery will be discharged. Normal variations in the mains
voltage throughout the day can cause some UPS types to use the battery more than others. For example, a Line-Interactive
UPS without a flywheel will use the battery each time the tap changing transformer switches to regulate the voltage. A
true On-line UPS normally will not use the battery as much as an Off-Line UPS. The wider the input voltage range, the less
often the UPS will use the battery, and so on.
Battery Cycling
During any given utility power failure (severe brownout or blackout conditions), the UPS operates on
battery power. The fewer times it must operate on battery power the longer the batteries will last. Once the utility
power is restored, the battery is recharged and available for future use. This entire "loop" is considered a
discharge cycle. Each discharge and subsequent recharge reduces the relative capacity of a UPS battery by a
small percentage. The length of the discharge cycle will also determine the reduction in battery capacity. 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 UPS batteries and the UPS, without
regular maintenance and service checks, a UPS battery could 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 |
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