TOSHIBA
20
Operating the UPS
Battery Backup Time and Discharge Process
The UPS unit's batteries provide about 7 minutes of back-up time for the 2.4 kVA, 3.6 kVA, 6 kVA,
and 8 kVA models. These times are valid when the unit is operating under full load (output
capacity is derated to 87% of nominal capacity when the output voltage is 208 Vac). When
these models are operating at half load, the batteries can provide about 20 minutes of back-up
time. The exact length of these times will depend on the UPS model used, condition of the
batteries, amount and type of load, temperature and other variables. See battery backup time
in 'Standard Specifications' beginning on page 18.
The following illustration graphically shows the battery discharge process at full load conditions.
Current
Voltage
Shutdown
voltage
100% 20% 0%
Imax
Imin
Vnom
Vlow
Vmin
Battery capacity
Battery Low Voltage Tolerances
Excessive discharge will cause the UPS unit's battery voltage to drop. The chart shown
below lists the voltage level at which each UPS unit's low-voltage alarm will sound and
also at what level the low-voltage condition will cause the unit to automatically shut down.
Nominal voltage (Vnom) 144Vdc 144Vdc 216Vdc 144Vdc
Alarm voltage (Vlow) 130Vdc 130Vdc 198Vdc 130Vdc
Shutdown voltage (Vmin) 115Vdc 115Vdc 175Vdc 115Vdc
UPS Capacity 2.4 kVA 3.6 kVA 6 kVA 8 kVA
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