UB10.241

U–Series

24V, 10A, DC-UPS

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 *)

7/23

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

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

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

515

2

4

6

8

10A

20

10

25 30 35

45 50

40

55 60 65 70 75 80 85

Buffer Time (Minutes)

UZK12.071 typ.

UZK12

.261 ty

p.

12V 7Ah battery

12V 26

Ah batt

ery

120

150

210 240

300

Min.

180

270

90

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:

June. 2010 / Rev. 1.3 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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