Data Sheet

UB10.241
U–Series
24V, 10A, DC-UPS
Mar. 2019 / Rev. 1.3a DS-UB10.241-EN
All parameters are specified at an input voltage of 24V, 10A output load, 25°C ambient and after a 5 minutes run-in time
unless otherwise noted. It is assumed that the input power source can deliver a sufficient output current.
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9. B
UFFER
T
IME
The buffer time depends on the capacity and performance of the battery as well as the load current. The diagram
below shows the typical buffer times of the standard battery modules.
Buffer time with battery module UZK12.071 min. 19’12’’ At 5A output current *)
min. 5’42’’ At 10A output current *)
typ. 21’30’’ At 5A output current, see Fig. 9-1 **)
typ. 6’45’’ At 10A output current, see Fig. 9-1 **)
Buffer time with battery module UZK12.261 min. 99’30’’ At 5A output current *)
min. 39’ At 10A output current *)
typ. 130’ At 5A output current, see Fig. 9-1 **)
typ.
55’
At 10A output current, see Fig. 9-1 **)
*) Minimum value includes 20% aging of the battery and a cable length of 1.5m with a cross section of 2.5mm
2
between the
battery and the DC-UPS and requires a fully charged (min. 24h) battery.
**) Typical value includes 10% aging of the battery and a cable length of 0.3m with a cross section of 2.5mm
2
between the battery
and the DC-UPS and requires a fully charged (min. 24h) battery.
Fig. 9-1
Buffer time vs. output current with the battery modules UZK12.071 and UZK12.261
Buffer Current
5 15
2
4
6
8
10A
2010 25 30 35 45 5040 55 60 65 70 75 80 85
Buffer Time (Minutes)
UZK12.071 typ.
UZK12.261 typ.
12V 7Ah battery
12V 26Ah battery
120
150 210 240
300
Min.
180 27090
UZK12.261 typ.
UZK12.071 typ.
90
The battery capacity is usually specified in amp-hours (Ah) for a 20h discharging event. The battery discharge is non-
linear (due to the battery chemistry). The higher the discharging current, the lower the appropriable battery capacity.
The magnitude of the reduction depends on the discharging current as well as on the type of battery. High current
battery types can have up to 50% longer buffer times compared to regular batteries when batteries will be
discharged in less than 1 hour.
High discharging currents do not necessarily mean high power losses as the appropriable battery capacity is reduced
with such currents. When the battery begins to recharge after a discharging event, the process is completed much
faster since only the energy which was taken out of the battery needs to be “refilled”.
For this reason, the buffer time cannot be calculated using the Ah capacity value. The equation “I x t” = capacity in
Ah generally leads to incorrect results when the discharging current is higher than C20 (discharging current for 20h).
The battery datasheet needs to be studied and a determination of the expected buffer time can be made according
to the following example: