TABLE 1
Battery Type
Characteristics
Lead-Calcium
20-30 year life on float
charge. Capacity decreases
with decrease in temperature.
Does not require periodic
equalizing charge if floated
between 2.20 and 2.25 volts
per cell.
Nickel-Cadmium**
Life in excess of 25 years
on float charge. Better low
temperature capacity than
other types. Very little
gassing under charge. Not
damaged by complete discharge.
Requires periodic
equalizing charge. High in
cost.
* Lead-antimony batteries use more water as they age
due to high charging current, and therefore require
more maintenance with aging. For this reason they
are not available for valve-regulated (sealed)
applications.
** Nickel-cadmium batteries, if not charged and
discharged periodically, may develop a "memory" and
fail to deliver their design capacity when required.
Also, cadmium is on the EPA's list of toxic
substances. There may be difficulty in disposing of
expended batteries.
b.
Battery Discharges and Service Life
Battery warranties are based on a given number of
discharges per year (at various rates) during the
life of the battery. The warranty may be voided if
the number of discharges per year exceeds the
manufacturer's specifications.
Battery service life is considered to end when the
battery fails to deliver 80 percent of its rated
capacity. Since UPS systems are always expected to
deliver 100 percent capacity, the battery must be
sized to deliver 100 percent of the UPS rating at
the end of its service life, which means the battery
must be oversized initially. Capacity determination
should be made in accordance with the "performance
test" guidelines of IEEE Std 450. If the UPS has
been oversized for specialized loads as described in
notes of paragraph LOAD PROFILE, the battery system
may be sized for the actual load.
c.
Specific Gravity and Charging Volts Per Cell:
SECTION 16265A
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