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Hipulse - Single Phase ‘1+N’ UPS System 130 kVA - 110V
49
6.4 Installation design considerations
Note: Full safety instructions concerning the use and maintenance of UPS batteries are provided in
the appropriate battery manufacturers’ manuals. The battery safety information contained in this
section relates to the key considerations, which must be taken into account during the installation
design process and might affect the design outcome depending on localized conditions.
6.5 Battery installation and maintenance
6.5.1 Temperature considerations
Battery performance depends on the ambient battery temperature. Capacity and
autonomy are quoted for a new battery operating at 20
o
C. Battery capacity is
increased by 1% for every 1
o
C increase in temperature up to 25
o
C. If a battery is
used at a temperature above 25
o
C, its life is reduced; consequently, its capacity and
UPS autonomy time will reduce more rapidly over a period of time. Operating below
20
o
C will reduce the battery capacity by approximately 1% -1.5% per 1
o
C. For
example if a battery discharge test is attempted during the middle of winter when the
ambient temperature is 5
o
C the battery capacity will be only 77.5% of its design value
and will not satisfy its specified autonomy time.
Ambient temperature, ventilation, spacing, float voltage and ripple current all affect
the battery temperature. Uneven temperature distribution through the battery string
will cause the voltage distribution to be uneven which can also lead to problems- it is
therefore very important to maintain an even temperature across the whole battery
chain. ‘Valve regulated’ cells are very sensitive to temperature and should be
operated at a temperature between 15
o
C and 25
o
C. To help sustain this operating
temperature range the battery is normally float charged at 2.25V/cell. When batteries
are cabinet mounted adjacent to the UPS module, it is the battery which dictates the
designed maximum ambient temperature, not the UPS.– i.e. in the case of ‘valve
regulated’ cells the ambient regulated cells the ambient room temperature should be
kept between 15
o
C and 25
o
C, and not between 0
o
C and 40
o
C (which is the specified
main equipment operating temperature range) Temperature excursions are
permissible for short periods of time provided the ambient temperature does not
exceed 25
o
C.
6.5.2 Battery population
The nominal DC bus voltage, and therefore battery float voltage, is set according to
the module’s rated input/output voltage and usually set top 432Vdc (380Vac) 446 Vdc
(440Vac) or 459Vdc (415Vac). Given that the desired cell float voltage is 2.25V, this
means that a different number of cells are required in each case. (See Table 6-1).
Parameter 380V 400V 415V
Number of cells used (Standard) 192 198 204
End-of-discharge voltage 320 330 340
Float voltage 432 446 459
Table 6-1 – Battery population